Clay Core Wall Seepage Control Technology in Hydraulic Engineering

1. Introduction

1.1 Technical Background

Clay core wall technology represents one of the oldest and most reliable methods for seepage control in hydraulic engineering structures, particularly earth and rockfill dams. The principle involves constructing a central impermeable core within the dam body using compacted clay materials, which serves as the primary barrier against water seepage while allowing the use of more permeable materials for the dam shell (26).

The technology has evolved significantly since its early applications, with modern engineering practices incorporating advanced material science, improved construction techniques, and sophisticated design methodologies. The fundamental concept remains unchanged: creating a "sandwich" structure where the impermeable clay core is sandwiched between more permeable shell materials, effectively blocking seepage paths while allowing for efficient load transfer and structural stability (30).

1.2 Advantages and Application Value

Clay core wall technology offers several key advantages that have ensured its continued use in hydraulic engineering projects worldwide:

Hydraulic Performance:

Low Permeability: Well-compacted clay cores achieve permeability coefficients as low as 1×10⁻⁵ cm/s or lower, effectively reducing seepage through the dam body
Self-Healing Capacity: Minor cracks or openings in the clay core can self-seal when exposed to water, maintaining the integrity of the 防渗 system
Effective Seepage Control: By establishing a continuous impermeable barrier, clay cores significantly reduce seepage forces and lower the phreatic surface within the dam

Engineering Properties:

Good Plasticity: Clay materials can undergo significant deformation without cracking, making them suitable for dams that may experience differential settlement
High Shear Strength: Properly compacted clay cores develop sufficient shear strength to maintain slope stability under various loading conditions
Stress Distribution: The core effectively distributes applied loads to the foundation, preventing stress concentration points

Construction Advantages:

Material Availability: Clay is widely available in most regions, reducing transportation costs and dependency on specialized materials
Simple Construction Methods: The technology requires relatively straightforward construction techniques that are well-established in the industry
Compatibility with Various Foundation Conditions: Clay cores can be adapted to different foundation types with appropriate interface treatments

Economic Benefits:

Cost-Effectiveness: Compared to alternative impermeable barrier systems like concrete diaphragm walls or geomembranes, clay cores often provide a more economical solution
Long Service Life: With proper design and maintenance, clay core dams can have service lives exceeding 100 years with minimal major repairs

1.3 Scope and Structure of This Manual

This technical manual is designed to provide comprehensive guidance on clay core wall technology for engineering professionals involved in the design, construction, inspection, and maintenance of hydraulic structures. The content includes:

Material Selection and Properties: Guidance on selecting appropriate clay materials and understanding their key properties
Design Principles and Considerations: Structural design approaches, layout options, and interface design considerations
Construction Methodology: Step-by-step procedures for clay core construction, including preparation, placement, and compaction
Quality Control and Assurance: Methods for ensuring material quality and construction compliance
Case Studies: Detailed analysis of international clay core dam projects, highlighting design innovations and construction challenges
Comparative Analysis with Alternative Technologies: Evaluation of clay core walls against other seepage control methods
Monitoring and Maintenance: Post-construction monitoring systems and long-term maintenance requirements
Relevant Standards and Specifications: Overview of key international standards applicable to clay core wall design and construction

The manual draws on both traditional engineering practices and the latest advancements in clay core technology, incorporating case studies from around the world to illustrate practical applications and solutions to common challenges.

2. Material Selection and Properties

2.1 Key Clay Material Properties

The success of a clay core wall depends largely on the selection of appropriate clay materials with suitable engineering properties. The following are the key characteristics that should be considered during material selection:

Particle Size Distribution:

Clay Content: Optimal clay content (particles <2μm) typically ranges between 30-45%, providing the necessary impermeability while maintaining workability
Silt Content: Silt particles (2-50μm) should ideally comprise 40-50% of the material, contributing to both impermeability and compressibility
Sand Content: Limited sand content (50μm-2mm) up to 20% is acceptable and can improve workability if the clay is excessively plastic

Consistency Limits:

Liquid Limit (LL): Should generally be less than 40% to avoid excessive swelling and shrinkage
Plastic Limit (PL): The plastic limit should be sufficiently high to allow for proper compaction without excessive water content
Plasticity Index (PI): Optimal PI values typically range between 7-20, balancing plasticity and workability

Compaction Characteristics:

Maximum Dry Density: Determined through standard Proctor compaction tests, provides the target density for field compaction
Optimum Moisture Content: The moisture content at which maximum dry density is achieved, critical for achieving desired permeability and strength

Permeability:

Coefficient of Permeability: Target values should be ≤1×10⁻⁵ cm/s, measured using constant or falling head permeability tests
Saturated Permeability: Determined under fully saturated conditions to simulate in-service performance

Shear Strength:

Cohesion (c): Typically ranges between 20-50 kPa for compacted clay cores
Angle of Internal Friction (φ): Values between 15-30° are typical, depending on clay type and compaction conditions

Durability Properties:

Freeze-Thaw Resistance: Resistance to deterioration from cyclic freezing and thawing
Slake Durability: Resistance to disintegration when repeatedly submerged and dried
Chemical Stability: Resistance to chemical attack from reservoir waters or foundation materials

2.2 Common Clay Materials for Core Walls

Several types of clay materials are commonly used in core wall construction, each with distinct characteristics and suitability for different applications:

Lean Clay (CL):

Properties: Moderate plasticity (PI 7-17), low to moderate compressibility, good shear strength
Advantages: Easy to compact, less prone to shrinkage cracks, good workability
Disadvantages: Lower impermeability compared to more plastic clays
Suitable Applications: General dam core construction where moderate impermeability is sufficient

Fat Clay (CH):

Properties: High plasticity (PI >17), high compressibility, lower shear strength when wet
Advantages: Extremely low permeability when properly compacted
Disadvantages: Prone to shrinkage cracks, difficult to compact at optimal moisture content, sensitive to moisture variations
Suitable Applications: High-importance dams requiring maximum impermeability, where shrinkage cracking can be managed

Silty Clay (CL-ML):

Properties: Medium plasticity, moderate compressibility, good workability
Advantages: Balanced combination of impermeability and workability, less prone to drying shrinkage than fat clays
Disadvantages: Lower shear strength than lean clays
Suitable Applications: Most common type for general dam core construction

Bentonitic Clay:

Properties: Extremely high plasticity, high swelling potential, very low permeability
Advantages: Exceptional impermeability, self-healing properties
Disadvantages: High swelling pressure, difficult to handle and compact, sensitive to moisture content
Suitable Applications: Specialized applications requiring maximum impermeability, often used in composite liners or as additives to improve other clays

Weathered Rock Materials:

Properties: Variable composition, often containing clay minerals along with rock fragments
Advantages: Local availability, potential cost savings
Disadvantages: Variability in properties, may require blending or treatment
Suitable Applications: When properly processed and tested, can be used in lower-importance dams or where specialized clays are not available

2.3 Material Selection Process

The material selection process for clay core walls typically follows these systematic steps:

Regional Material Survey

Conduct geological surveys to identify potential clay deposits within reasonable proximity to the project site
Map outcrop locations, thicknesses, and preliminary estimates of material quantities
Collect initial samples for preliminary characterization tests

Laboratory Testing Program

Perform basic index tests (grain size analysis, Atterberg limits) on representative samples
Conduct compaction tests to determine maximum dry density and optimum moisture content
Perform permeability tests to assess seepage characteristics
Conduct shear strength tests to evaluate stability parameters
Test for durability characteristics (freeze-thaw, slake durability) as needed for the project conditions

Material Suitability Assessment

Compare test results against established criteria for clay core materials
Evaluate materials based on engineering properties, availability, and cost
Identify potential issues such as high plasticity, excessive silt/sand content, or deleterious substances
Consider treatment options if natural materials do not fully meet requirements

Source Selection and Development Plan

Select the most suitable material sources based on technical and economic considerations
Develop detailed site development plans including access roads, drainage systems, and extraction methods
Establish quality control procedures for material extraction and processing

Material Treatment and Modification

Implement drying or wetting processes to achieve desired moisture content
Incorporate additives (lime, cement, fly ash) to modify material properties as needed
Process materials to remove oversized particles or deleterious materials

2.4 Special Considerations for Problematic Clays

In situations where ideal clay materials are not available, engineering solutions can be implemented to utilize problematic clays:

Dispersive Clays:

Characteristics: Tendency to disperse in water due to low electrolyte content in pore water
Treatment Methods:
- Add 3-5% lime to increase cation exchange capacity
- Construct protective filter layers to prevent particle migration
- Implement special compaction techniques to enhance structural stability

Expansive Clays:

Characteristics: High swelling potential due to montmorillonite content
Treatment Methods:
- Limit moisture content to minimize swelling potential
- Use lime stabilization to reduce plasticity
- Implement controlled compaction at higher moisture contents
- Provide adequate drainage to minimize moisture variation

Organic Clays:

Characteristics: High organic matter content (>2%), reduces strength and increases compressibility
Treatment Methods:
- Remove organic materials through screening or washing
- Use thermal treatment to reduce organic content
- Incorporate cementitious materials to improve strength and reduce compressibility

Sandy Clays:

Characteristics: High sand content (>20%), reduces plasticity and impermeability
Treatment Methods:
- Blend with higher plasticity clays to improve impermeability
- Implement modified compaction procedures to achieve better particle packing
- Consider adding bentonite to improve sealing properties

3. Design Principles and Structural Considerations

3.1 Basic Design Concepts

Clay core wall design involves creating an impermeable barrier within the dam structure that effectively controls seepage while maintaining structural stability. The basic design concepts include:

Zoned Earth Dam Concept

Clay core walls are typically part of zoned earth dam designs, where the dam is divided into distinct zones with different material properties:

Core Zone: The central impermeable clay core
Transition Zones: Materials with intermediate properties between the core and shell
Shell Zones: More permeable materials forming the main body of the dam
Drainage Zones: Materials providing controlled seepage paths and preventing water accumulation

Hydraulic Design Principles

The primary hydraulic design objectives include:

Minimizing seepage through the dam body
Controlling the position of the phreatic surface within safe limits
Preventing piping or internal erosion within the core or adjacent materials
Ensuring adequate hydraulic gradients do not exceed critical values for the materials used

Structural Design Principles

The key structural design objectives include:

Ensuring overall stability against sliding under all loading conditions
Minimizing differential settlements that could cause cracking in the core
Providing adequate support to the core from surrounding materials
Managing stresses within the core to prevent tensile cracking or shear failure

3.2 Core Wall Geometry and Dimensions

The geometry and dimensions of clay core walls are critical design parameters that influence both hydraulic performance and structural stability.

Cross-Sectional Shape

Common cross-sectional shapes for clay core walls include:

Vertical Core: The most common configuration, with the core extending vertically from foundation to crest
Inclined Core: The core is inclined towards the upstream or downstream face, increasing the seepage path length
Combination Shapes: May incorporate both vertical and inclined sections to adapt to specific site conditions or loading requirements

Core Thickness

The required thickness of the clay core is determined by several factors:

Hydraulic Gradient: The allowable hydraulic gradient (typically 3-5 for clay cores)
Height of Water Head: Thickness is generally 1/8 to 1/4 of the maximum water head
Minimum Thickness: A minimum thickness of 3 meters is typically specified to allow for construction equipment operation

Core Crest Elevation

The core crest should be:

At least 0.5 meters above the design flood water level
Protected by an adequate freeboard to prevent overtopping
Designed to accommodate settlement and deformation

Core Foundation Contact

The core should extend to:

A competent foundation material with low permeability
A depth sufficient to intercept all significant seepage paths
Typically extends 1-2 meters into the foundation material

3.3 Foundation Preparation and Interface Design

Proper foundation preparation and interface design are critical to the success of clay core walls:

Foundation Preparation

Remove all organic materials, vegetation, and loose debris from the foundation surface
Excavate to firm, competent material with low permeability
Provide adequate drainage to keep the foundation dry during construction
Treat any existing cracks, fissures, or cavities in rock foundations

Contact Zone Design

Specialized contact materials may be used between the clay core and foundation or other structures:

Transition Layers: Materials with intermediate properties between the core and foundation
Bedding Layers: Thin layers of fine-grained materials to provide a smooth transition
Sealing Layers: Materials with exceptionally low permeability for critical interfaces

Foundation Seepage Control

Additional measures may be needed to control foundation seepage:

Cutoff Trenches: Excavated trenches filled with impermeable materials to intercept horizontal seepage
Grout Curtains: Deep grouting in rock foundations to reduce permeability
Horizontal Seepage Barriers: Impermeable blankets extending from the core into the foundation

3.4 Seepage Analysis Methods

Comprehensive seepage analysis is essential for proper clay core wall design:

Analytical Methods

Flow Net Analysis: Traditional graphical method for visualizing seepage patterns
Hydraulic Gradient Calculations: Determine maximum gradients within the core and adjacent materials
Seepage Quantity Estimation: Calculate total seepage through the dam for design purposes

Numerical Modeling

Finite Difference Methods: Commonly used for complex geometries and material properties
Finite Element Methods: Provides more accurate solutions for complex stress-deformation conditions
Seepage-Strength Coupled Analysis: Advanced method considering the interaction between seepage and material strength

Design Criteria for Seepage Control

Maximum Allowable Hydraulic Gradient: Typically 3-5 for clay cores, depending on material properties
Seepage Discharge Limits: Should be within acceptable environmental and operational constraints
Phreatic Surface Position: Should be maintained at a safe distance from the downstream slope surface

3.5 Stability Analysis Considerations

Stability analysis ensures the clay core wall and surrounding structures can withstand all anticipated loading conditions:

Slope Stability Analysis

Methods: Swedish circle method, Bishop's simplified method, Janbu's method
Loading Conditions: Consider all relevant load cases including:
- Normal operating conditions
- Flood conditions
- Rapid drawdown conditions
- Earthquake conditions
Factor of Safety Requirements: Typically 1.5 for normal conditions and 1.2 for earthquake conditions

Core Stability Considerations

Shear Strength Parameters: Use appropriate shear strength values for the core material
Stress Distribution: Analyze stress distribution within the core to identify potential failure zones
Deformation Analysis: Consider the effects of differential settlement on core integrity

Earthquake Design Considerations

Pseudo-static Analysis: Traditional method incorporating seismic forces as static loads
Dynamic Analysis: More advanced method considering time-dependent ground motions
Liquefaction Potential: Evaluate potential for liquefaction in saturated granular materials
Core Material Damping: Consider the damping properties of clay materials in seismic design

4. Construction Methodology

4.1 Pre-construction Planning and Site Preparation

Comprehensive pre-construction planning is essential for successful clay core wall construction:

Project Planning Documentation

Develop detailed construction schedules with clear milestones
Prepare comprehensive quality control and assurance plans
Create safety plans addressing site-specific hazards
Develop environmental protection measures

Site Access and Infrastructure

Construct access roads to material sources and work areas
Establish site utilities including water supply, power, and communications
Set up temporary facilities for equipment storage, maintenance, and personnel

Foundation Preparation

Clear and grub the foundation area to remove all vegetation and organic materials
Excavate to the specified depth, ensuring removal of all unsuitable materials
Grade the foundation surface to the specified contours
Install foundation drainage systems as required
Conduct necessary foundation treatment (grouting, cutoff walls) before core construction

Material Source Development

Develop clay material sources including access roads and drainage systems
Implement pre-wetting or drying processes to achieve target moisture content
Establish stockpile areas for processed materials
Install quality control stations at material sources

4.2 Material Handling and Placement Techniques

Proper material handling and placement techniques are critical to achieving design performance:

Material Extraction and Transport

Use appropriate excavation equipment based on material type and conditions
Implement moisture conditioning during extraction if necessary
Transport materials in covered vehicles to minimize moisture loss
Schedule deliveries to match placement rates

Base Preparation and Moisture Control

Prepare the foundation or previous lift surface by scarifying and moistening
Control base moisture content to ensure good bond between lifts
Install any required geosynthetic materials or drainage layers

Laydown and Spreading Operations

Use appropriate equipment (bulldozers, graders) for spreading materials
Maintain consistent layer thicknesses (typically 20-30 cm for clay cores)
Avoid creating thin or thick spots that could affect compaction uniformity
Implement measures to protect placed materials from weathering

Specialized Placement Techniques

Trench Filling: Used for constructing cutoff walls in existing dams
Hydraulic Filling: Less common method using water-saturated slurries
Vibroflotation: Technique for placing materials in difficult-to-access areas
Freeze Core Method: Specialized technique for cold regions creating temporary frozen cores

4.3 Compaction Procedures and Equipment

Proper compaction is essential for achieving the required density, strength, and permeability:

Compaction Equipment Selection

Rollers: Smooth drum rollers (for clay), pneumatic tired rollers (for mixed materials)
Sheepsfoot Rollers: Traditional choice for clay materials, creating indentations that improve inter-layer bonding
Vibratory Rollers: Effective for granular materials but used with caution on clay
Small Equipment: Used for confined areas and around structures

Compaction Parameters

Number of Passes: Typically 6-12 passes depending on material and equipment
Roller Speed: Generally 2-4 km/h for optimal compaction
Overlap: Maintain adequate overlap between passes (1/3 to 1/2 of roller width)
Direction: Maintain consistent rolling direction to avoid segregation

Moisture Content Control

Maintain moisture content within ±2% of the optimum moisture content
Implement drying or wetting procedures as needed
Protect placed materials from rain and evaporation
Adjust compaction efforts based on actual moisture conditions

Compaction Quality Control

Conduct frequent density tests using nuclear densometers or sand cone tests
Monitor layer thickness and roller passes
Record all compaction data for documentation purposes
Correct any identified deficiencies immediately

4.4 Joints and Construction Seams Treatment

Proper treatment of joints and construction seams is critical to maintaining core integrity:

Horizontal Joint Treatment

Prepare the surface of previously placed material by scarifying to a depth of 2-5 cm
Adjust moisture content as needed to ensure good bonding
Overlap adjacent lifts by at least 30 cm to ensure continuity
Ensure that joints are staggered between adjacent lifts

Vertical Joint Treatment

Use key trenches or stepped joints to improve interlock between sections
Place materials in thin layers near vertical joints to ensure proper compaction
Use special attention to moisture control at vertical joints
Implement quality control testing at all vertical joints

Cold Joints

Treat cold joints (delays exceeding 24 hours) as new construction interfaces
Prepare the existing surface by scarifying, cleaning, and adjusting moisture content
Apply a thin layer of slurry (similar to core material) before placing new material
Conduct additional testing at cold joints to ensure adequate bonding

Structural Interface Treatment

Provide adequate bedding layers where the core meets concrete structures
Use special materials (bentonite pads, sealing compounds) at critical interfaces
Implement appropriate curing periods before exposing interfaces to water

4.5 Seasonal Construction Considerations

Special considerations are needed for construction under challenging seasonal conditions:

Rainy Season Construction

Implement comprehensive drainage systems to remove surface water
Use waterproof tarps to protect placed materials from rain
Adjust compaction parameters for wetter conditions
Implement additional drying measures if materials become too wet
Avoid construction during periods of heavy rainfall

Dry Season Construction

Implement water spraying systems to maintain target moisture content
Protect exposed materials from excessive evaporation
Schedule work during cooler parts of the day to minimize moisture loss
Increase the frequency of moisture content testing
Use appropriate equipment to minimize dust generation

Cold Weather Construction

Avoid placing materials when temperatures are below freezing
Implement freeze protection measures for stockpiled materials
Adjust compaction parameters for colder conditions
Increase the number of roller passes for cold weather compaction
Use insulated tarps to protect placed materials from freezing

Extreme Temperature Conditions

Adjust work schedules to avoid extreme temperature periods
Implement additional moisture control measures
Use sunshades to protect materials from excessive solar radiation
Monitor equipment performance under extreme temperatures

4.6 Special Construction Techniques for Problematic Conditions

Specialized techniques may be required for challenging construction conditions:

High Moisture Content Materials

Use pre-drying techniques including windrowing and turning
Implement controlled drainage systems at material sources
Use special compaction equipment designed for wet conditions
Consider adding absorbent materials (lime, fly ash) to reduce moisture content

Low Moisture Content Materials

Implement pre-wetting systems at material sources
Use water trucks for in-situ moisture conditioning
Cover materials to prevent further drying
Consider adding water retention agents to improve workability

Narrow or Confined Spaces

Use specialized compactors designed for confined spaces
Place materials in thinner layers to improve compaction efficiency
Use hand-held equipment for difficult-to-reach areas
Implement special inspection procedures for confined spaces

Steep Slopes

Use stepped construction methods on steep slopes
Implement additional compaction passes near slopes
Use temporary shoring if necessary
Conduct additional stability checks for slopes exceeding 1:2

Existing Dam Modifications

Implement careful excavation techniques to avoid destabilizing existing structures
Use specialized equipment for working in tight spaces
Implement comprehensive monitoring during construction
Develop contingency plans for unexpected conditions

5. Quality Control and Assurance

5.1 Material Quality Control Tests

Comprehensive testing programs are essential to ensure materials meet design requirements:

Index Property Tests

Grain Size Analysis: Conducted to verify particle size distribution
Atterberg Limits: Performed to confirm liquid limit, plastic limit, and plasticity index
Specific Gravity: Determined to assist in other calculations and material characterization

Compaction Tests

Standard Proctor Test: Performed to establish maximum dry density and optimum moisture content
Modified Proctor Test: Used for materials requiring higher compaction energy
Field Density Tests: Conducted using sand cone, rubber balloon, or nuclear densometer methods

Permeability Tests

Constant Head Permeability Test: Used for more permeable materials
Falling Head Permeability Test: Suitable for low-permeability materials
In-situ Permeability Tests: Conducted on completed cores to verify performance

Shear Strength Tests

Direct Shear Test: Simple method for determining shear strength parameters
Triaxial Shear Test: More accurate method considering confining pressures
Unconfined Compression Test: Quick method for estimating undrained shear strength

Specialized Tests

Swelling Pressure Tests: For expansive clays
Shrinkage Limit Tests: To determine the moisture content below which no further volume change occurs
Freeze-Thaw Tests: To evaluate durability in cold climates
Chemical Analysis: To identify potential contaminants or deleterious substances

5.2 Construction Quality Control Procedures

Rigorous construction quality control procedures ensure compliance with design specifications:

Moisture Content Control

Frequency: Test at least once per 200-400 m² or more frequently under varying conditions
Methods: Oven drying, microwave drying, calcium carbide, or electronic moisture meters
Target: Maintain moisture content within ±2% of optimum moisture content

Dry Density Control

Frequency: Test at least once per 200-400 m², with additional tests at joints and critical areas
Methods: Sand cone, rubber balloon, nuclear densometer
Target: Achieve at least 95-98% of the maximum dry density from the Proctor test

Thickness Control

Frequency: Monitor continuously during placement
Methods: Use grade stakes, laser levels, or GPS-guided equipment
Target: Maintain specified layer thickness within ±5%

Compaction Control

Monitor roller passes and speeds using GPS tracking systems
Verify compaction coverage and overlap
Conduct in-place density tests to confirm compaction effectiveness
Adjust compaction parameters as needed based on test results

Surface Condition Control

Inspect surfaces for cracks, segregation, or other defects
Verify proper preparation of surfaces between lifts
Ensure proper moisture conditioning at lift interfaces
Check for adequate scarification between lifts

5.3 In-situ Testing Methods

In-situ testing provides valuable information about the performance of constructed materials:

Penetration Resistance Tests

Standard Penetration Test (SPT): Provides a measure of relative density in granular materials
Dynamic Cone Penetrometer (DCP): Portable device for measuring resistance to penetration
Static Cone Penetration Test (CPT): Provides continuous profile of subsurface conditions

Geophysical Methods

Ground Penetrating Radar (GPR): Used to detect voids, cracks, or changes in material properties
Seismic Refraction: To determine the depth of subsurface layers
Electrical Resistivity: To map variations in material properties
Thermal Imaging: To detect moisture variations or potential seepage paths

Hydraulic Testing

Pumping Tests: To determine hydraulic conductivity of foundation materials
Borehole Packer Tests: To isolate specific zones for permeability testing
Slug Tests: Quick method for determining hydraulic conductivity

Structural Integrity Testing

Cross-hole Sonic Logging: To evaluate the integrity of concrete or grouted zones
Impulse Response Testing: To detect voids or cracks in concrete structures
Ultrasonic Testing: To evaluate material integrity and bond quality

5.4 Monitoring Systems Installation

Permanent monitoring systems provide ongoing assessment of clay core wall performance:

Seepage Monitoring

Piezometers: Installed within the core and foundation to monitor pore water pressures
V-notch Weirs: For measuring seepage discharge rates
Flow Meters: For measuring flow in drainage systems
Water Quality Monitoring Stations: To detect changes in water chemistry that may indicate internal erosion

Deformation Monitoring

Survey Monuments: For measuring surface deformations
Inclinometers: For measuring horizontal deformations with depth
Extensometers: For measuring vertical deformations
GPS Monitoring: Provides high-precision deformation measurements

Stress Monitoring

Earth Pressure Cells: To measure total stress in soils
Pore Pressure Transducers: To measure pore water pressures
Strain Gauges: For measuring strain in structural elements

Environmental Monitoring

Rain Gauges: To monitor precipitation rates and amounts
Temperature Sensors: To monitor ambient and soil temperatures
Wind Speed and Direction Sensors: For wave action analysis

Monitoring System Design Considerations

Install monitoring equipment during construction at strategic locations
Provide adequate protection to monitoring equipment from construction activities
Implement a data management system for monitoring data
Train personnel on monitoring system operation and maintenance
Establish baseline readings before reservoir filling

5.5 Acceptance Criteria and Documentation

Establishing clear acceptance criteria and maintaining comprehensive documentation are essential:

Material Acceptance Criteria

Define acceptable ranges for key material properties
Establish limits for deleterious substances
Specify minimum requirements for durability characteristics
Define corrective actions for materials not meeting specifications

Construction Acceptance Criteria

Set minimum dry density requirements (typically 95-98% of Proctor maximum)
Establish moisture content tolerances (±2% of optimum)
Define acceptable layer thickness variations
Specify limits for surface irregularities
Establish criteria for joint and seam quality

Test Frequency Requirements

Define the required frequency for each type of test
Specify minimum numbers of tests per material source
Establish additional testing requirements for problematic areas
Define the process for increasing test frequencies when issues are identified

Documentation Requirements

Maintain detailed records of all materials used including sources and test results
Document all construction activities including dates, equipment used, and personnel involved
Record all test results with associated locations and times
Maintain photographic documentation of critical activities
Prepare as-built drawings reflecting actual construction conditions

6. Case Studies

6.1 European Clay Core Dam Projects

European engineering practice has produced several notable clay core dam projects:

Canales Dam, Spain

Location: Genil River, Granada, Spain
Dam Type: Clay core rockfill dam
Height: 156 meters
Crest Length: 340 meters
Reservoir Capacity: 110 million cubic meters
Construction Period: 1975-1989
Special Features:
- Unique design combining clay core with concrete face
- Comprehensive monitoring system including piezometers and deformation sensors
- Innovative foundation treatment using deep grouting
- Incorporation of environmental considerations in design and construction
Lessons Learned: Importance of comprehensive foundation investigation and treatment for high dams

Pant-Yr-Eos Reservoir, United Kingdom

Location: Approximately 2 km east of Risca, Monmouthshire, UK
Dam Type: Embankment dam with clay core
Height: 27 meters
Crest Length: 280 meters
Storage Capacity: Approximately 600 million liters
Construction Period: Completed in 1878, major improvements in 2022
Special Features:
- Historic reservoir upgraded to modern standards
- Implementation of improved spillway and emergency scour systems
- Installation of new filtered drainage blanket on downstream embankment toe
- Comprehensive instrumentation for monitoring dam performance
Lessons Learned: Successful adaptation of historic dams to modern safety standards

Burvattnet Dam, Sweden

Location: Northern Sweden
Dam Type: Clay core rockfill dam
Height: Approximately 30 meters
Special Features:
- Revived use of Swedish wet compaction method for clay core construction
- Implemented due to lack of suitable dry core soil and severe weather conditions
- Laboratory compaction tests following 1950s standards
- Successful continuation of filling works within project timeline constraints
Lessons Learned: Innovative adaptation of historic construction methods to modern challenges

6.2 North American Clay Core Dam Projects

North America has a rich history of clay core dam construction with several notable examples:

Guajataca Dam, Puerto Rico

Location: Guajataca River, Puerto Rico
Dam Type: Earthfill dam with clay core
Height: Approximately 45 meters
Reservoir Capacity: 22.7 million cubic meters
Construction Period: Completed in 1938
Special Features:
- Constructed during the Great Depression as part of public works programs
- Experienced significant damage during Hurricane Maria in 2017
- Geological challenges including contact between Miocene-aged limestone and weak calcareous mudstone
- Complex landslide mechanisms affecting dam stability
Lessons Learned: Importance of considering geological complexities in dam design and rehabilitation

Fort Peck Dam, Montana, USA

Location: Missouri River, Montana, USA
Dam Type: Earthfill dam with clay core
Height: 76 meters
Crest Length: 6,400 meters
Reservoir Capacity: 96.1 billion cubic meters
Construction Period: 1933-1940
Special Features:
- One of the largest earthfill dams in the world
- Constructed during the Great Depression as part of the New Deal
- Experienced foundation stability issues during construction
- Utilized extensive borrow areas within the reservoir
Lessons Learned: Valuable insights into large-scale earthfill dam construction and foundation treatment

Atatürk Dam, Turkey

Location: Euphrates River, Turkey
Dam Type: Clay core rockfill dam
Height: 169 meters
Crest Length: 1,820 meters
Reservoir Capacity: 48.7 billion cubic meters
Construction Period: 1983-1990
Special Features:
- Largest dam in Turkey and one of the largest in the Middle East
- Comprehensive 3D nonlinear analysis conducted to evaluate performance under various reservoir levels
- Extensive monitoring system including geodetic measurements
- Verification of numerical analysis results with actual settlement monitoring data
Lessons Learned: Importance of advanced numerical modeling for high dams and verification through comprehensive monitoring

6.3 International Case Studies with Specialized Techniques

Several international projects demonstrate innovative applications of clay core wall technology:

Moragahakanda Dam, Sri Lanka

Location: Mahaweli River, Sri Lanka
Dam Type: Clay core rockfill dam
Height: 117 meters
Crest Length: 1,050 meters
Reservoir Capacity: 1.1 billion cubic meters
Construction Period: 2007-2017
Special Features:
- Largest hydropower project in Sri Lanka
- Comprehensive monitoring system including piezometers and seepage meters
- Implementation of advanced grouting techniques for foundation treatment
- Integration of environmental protection measures into construction activities
Lessons Learned: Successful implementation of large-scale dam projects in challenging tropical environments

Jatigede Dam, Indonesia

Location: Citarum River, West Java, Indonesia
Dam Type: Clay core rockfill dam
Height: 107 meters
Crest Length: 670 meters
Reservoir Capacity: 980 million cubic meters
Construction Period: 2005-2014
Special Features:
- Comprehensive monitoring system including pore pressure gauges at multiple elevations
- Detailed analysis of pore water pressure changes during different construction and operational phases
- Implementation of advanced quality control measures
- Successful performance under various loading conditions
Lessons Learned: Importance of comprehensive monitoring for evaluating dam performance and ensuring safety

Monajavu Dam, Fiji

Location: Viti Levu Island, Fiji
Dam Type: Clay core rockfill dam
Height: 85 meters
Special Features:
- Constructed using high-water-content clay materials (natural water content up to 74%)
- Operated under extreme weather conditions with only 5-6 dry days per month
- Innovative quality control approach focusing on in-situ shear strength testing
- Successful adaptation of construction methods to challenging environmental conditions
Lessons Learned: Demonstrated that high-water-content clays can be successfully used in dam construction with appropriate techniques and quality control measures

6.4 Case Study Comparison and Analysis

A comparative analysis of selected case studies reveals important patterns and considerations:

Material Selection and Treatment Comparison

European Projects: Tend to use more standardized materials with strict quality control
North American Projects: Often utilize locally available materials with appropriate treatment
International Projects: Show greater innovation in using non-traditional materials and methods

Design Approaches Comparison

High Dams: Require more sophisticated design approaches including 3D finite element analysis
Medium and Low Dams: Often use simplified design methods with empirical adjustments
Historic Dams: Show evolution in design approaches over time with increasing sophistication

Construction Methods Comparison

Modern Projects: Incorporate GPS tracking, automated compaction control, and advanced monitoring
Historic Projects: Relied on manual methods and empirical observations
Challenging Environments: Demonstrated innovative adaptations including wet compaction and high-moisture content construction

Lessons Learned Summary

Comprehensive Geological Investigation: Essential for identifying potential foundation issues
Material Quality Control: Critical for achieving design performance
Innovative Adaptation: Necessary when traditional methods are not feasible
Advanced Monitoring: Provides valuable insights into dam performance and safety
Environmental Considerations: Increasing importance in modern dam construction
Integration of New Technologies: Enhances both efficiency and quality control

7. Comparative Analysis with Alternative Technologies

7.1 Comparison with Concrete Diaphragm Walls

Clay core walls and concrete diaphragm walls represent two major approaches to seepage control in hydraulic structures:

Technical Performance Comparison

Performance Aspect	Clay Core Walls	Concrete Diaphragm Walls
Permeability	Lower (≤1×10⁻⁵ cm/s)	Higher (1×10⁻⁷ cm/s)
Flexibility	Higher, adapts better to deformation	Lower, more prone to cracking
Self-healing Capacity	Good, minor cracks can self-seal	Poor, cracks require active repair
Shear Strength	Medium, depends on clay properties	High, especially in tension
Durability	Good, but sensitive to certain chemicals	Excellent, highly resistant to chemicals

Construction Considerations

Construction Complexity: Clay cores are generally simpler with established methods
Equipment Requirements: Clay cores require standard earthmoving equipment; diaphragm walls require specialized equipment
Weather Sensitivity: Clay cores are more sensitive to extreme weather conditions
Construction Time: Clay cores typically take longer due to layering and compaction requirements

Cost Comparison

Material Costs: Clay materials are generally cheaper, especially when locally available
Construction Costs: Concrete diaphragm walls typically have higher construction costs
Maintenance Costs: Clay cores may require more frequent maintenance over time
Life Cycle Costs: Comparative life cycle costs depend on specific project conditions

Applicability Comparison

Clay Core Walls: Best suited for medium to low dams, areas with suitable clay materials, and where some deformation is expected
Concrete Diaphragm Walls: Best suited for high dams, areas with limited clay resources, and where high structural integrity is required

7.2 Comparison with Geomembrane Liners

Clay core walls and geomembrane liners represent two different approaches to creating impermeable barriers:

Technical Performance Comparison

Performance Aspect	Clay Core Walls	Geomembrane Liners
Permeability	Lower (≤1×10⁻⁵ cm/s)	Higher (1×10⁻¹⁰ to 1×10⁻¹⁴ cm/s)
Flexibility	Medium, depends on clay properties	High, excellent resistance to deformation
Puncture Resistance	Medium, depends on thickness and quality	High for reinforced geomembranes
Self-healing Capacity	Good for minor cracks	Poor, requires repair for punctures
Chemical Resistance	Variable, depends on clay composition	Excellent for HDPE geomembranes

Installation Considerations

Surface Preparation: Both require careful surface preparation, but requirements differ
Jointing Techniques: Clay cores require careful compaction at joints; geomembranes require specialized welding
Protection Requirements: Geomembranes typically require protective layers above and below
Installation Speed: Geomembranes can often be installed more quickly

Cost Comparison

Material Costs: Geomembranes generally have higher material costs
Installation Costs: Geomembranes may have lower installation costs for large areas
Maintenance Costs: Geomembranes may require more specialized maintenance
Replacement Costs: Geomembranes may be easier and cheaper to replace in case of failure

Environmental Impact Comparison

Resource Consumption: Clay cores utilize natural materials; geomembranes are petroleum-based
Carbon Footprint: Geomembranes typically have higher carbon footprint due to manufacturing processes
Waste Management: Geomembranes generate more plastic waste at end of life

Applicability Comparison

Clay Core Walls: Best suited for dams where suitable clay materials are available, and long-term performance is critical
Geomembrane Liners: Best suited for reservoirs, ponds, and containment facilities where rapid installation and high chemical resistance are needed

7.3 Comparison with Geosynthetic Clay Liners (GCLs)

Clay core walls and geosynthetic clay liners represent different approaches to creating clay-based barriers:

Technical Performance Comparison

Performance Aspect	Clay Core Walls	Geosynthetic Clay Liners (GCLs)
Permeability	Lower (≤1×10⁻⁵ cm/s)	Higher (1×10⁻⁹ to 1×10⁻¹⁰ cm/s)
Flexibility	Medium, depends on clay properties	High, adapts well to uneven surfaces
Thickness	Typically 3-5 meters	Typically 5-10 mm
Swelling Capacity	Variable, depends on clay type	High, bentonite-based GCLs swell significantly
Self-healing Capacity	Good for minor cracks	Excellent for small punctures

Installation Considerations

Surface Preparation: Both require smooth surfaces, but GCLs are more sensitive to sharp objects
Jointing Techniques: Clay cores require careful compaction at joints; GCLs require proper overlapping and sealing
Water Exposure: GCLs should be wetted carefully to ensure proper hydration
Protection Requirements: GCLs typically require protective layers above and below

Cost Comparison

Material Costs: GCLs generally have higher material costs per unit area
Installation Costs: GCLs may have lower installation costs for large areas
Maintenance Costs: GCLs may require specialized maintenance
Life Cycle Costs: Comparative life cycle costs depend on specific project conditions

Performance Limitations

Clay Core Walls: Performance depends on quality of materials and compaction
GCLs: Performance depends on proper hydration and protection from damage
Extreme Conditions: Both systems have limitations under extreme temperatures or chemical exposure

Applicability Comparison

Clay Core Walls: Best suited for dams and large hydraulic structures where long-term performance is critical
Geosynthetic Clay Liners: Best suited for lining applications in landfills, ponds, and containment facilities where space is limited

7.4 Comparison with Cement-bentonite Cutoff Walls

Cement-bentonite cutoff walls represent another alternative to clay core walls for seepage control:

Technical Performance Comparison

Performance Aspect	Clay Core Walls	Cement-bentonite Cutoff Walls
Permeability	Lower (≤1×10⁻⁵ cm/s)	Higher (1×10⁻⁷ to 1×10⁻⁸ cm/s)
Flexibility	Medium, depends on clay properties	Medium, depends on mix design
Strength	Medium, depends on clay properties	Medium, lower than concrete
Self-healing Capacity	Good for minor cracks	Limited, depends on mix design
Durability	Good, but sensitive to certain chemicals	Good, especially in alkaline environments

Construction Process Comparison

Excavation Methods: Both require excavation, but methods differ
Mixing Processes: Cement-bentonite walls require precise mixing of components
Placement Techniques: Cement-bentonite is placed as a slurry; clay core materials are placed and compacted in layers
Curing Requirements: Cement-bentonite requires curing time; clay cores require proper moisture control

Cost Comparison

Material Costs: Cement-bentonite materials are generally more expensive
Construction Costs: Cement-bentonite walls typically have higher construction costs
Maintenance Costs: Clay cores may require more frequent maintenance
Replacement Costs: Replacement costs depend on specific failure modes and locations

Specialized Applications

Contaminated Sites: Cement-bentonite walls may offer better chemical resistance
Urban Environments: Cement-bentonite walls may be more suitable due to space constraints
High Water Table Conditions: Cement-bentonite walls can be constructed under water
Existing Structures: Cement-bentonite walls can be used for underpinning and retrofitting

Applicability Comparison

Clay Core Walls: Best suited for new dam construction where suitable clay materials are available
Cement-bentonite Cutoff Walls: Best suited for retrofitting existing structures, contaminated sites, and challenging construction environments

7.5 Selection Guidelines for Different Project Conditions

Based on the comparative analysis, the following guidelines can assist in selecting the most appropriate seepage control technology:

Site Conditions-Based Selection

Available Materials: Use clay core walls where suitable clays are available; consider alternatives otherwise
Foundation Conditions: Clay cores are suitable for most foundations with proper preparation; diaphragm walls may be preferred for certain rock foundations
Environmental Conditions: Consider weather patterns and extreme events when selecting construction methods

Project Scale-Based Selection

Large Dams (Height >70m): Concrete diaphragm walls or composite systems may be more appropriate
Medium Dams (30-70m): Clay core walls are often the most economical choice
Small Dams (<30m): Clay core walls or geosynthetic solutions may be suitable
Retrofitting Projects: Cement-bentonite or geomembrane solutions may offer advantages over traditional clay cores

Performance Requirements-Based Selection

High Impermeability Needs: Geomembranes or composite systems may be preferred
High Flexibility Needs: Geomembranes or properly designed clay cores are suitable
Chemical Resistance Needs: Concrete or geomembrane solutions may be more appropriate
Long-term Durability: Clay cores with proper materials and construction can provide excellent long-term performance

Economic Considerations-Based Selection

Initial Costs: Clay cores are often more economical for large projects with local materials
Life Cycle Costs: Consider maintenance and replacement costs over the structure's lifetime
Construction Schedule: Geomembranes and cement-bentonite systems may offer faster installation in certain conditions

Hybrid Systems Consideration

In many cases, hybrid systems combining elements of different technologies can provide optimal performance:

Clay Core with Geomembrane: Provides dual barriers for critical applications
Cement-bentonite Cutoff Wall with Clay Core: Combines deep cutoff with broad coverage
Clay Core with GCL Liner: Enhances impermeability in specific zones
Composite Systems: Combining multiple technologies to address different aspects of seepage control

8. Monitoring, Maintenance, and Rehabilitation

8.1 Operational Monitoring Systems

Comprehensive monitoring systems are essential for evaluating the performance of clay core walls:

Monitoring System Components

Seepage Monitoring: Piezometers, weirs, flow meters
Deformation Monitoring: Survey monuments, inclinometers, extensometers
Stress Monitoring: Earth pressure cells, pore pressure transducers
Environmental Monitoring: Rain gauges, temperature sensors, wind sensors

Monitoring Frequency

Initial Period (0-2 years): More frequent monitoring to establish baseline performance
Established Period (2-10 years): Reduced frequency based on stability
Aging Period (>10 years): Increased monitoring frequency as structures age
Special Events: Increased monitoring during floods, earthquakes, or other extreme events

Data Management and Analysis

Implement automated data logging systems
Develop comprehensive databases for monitoring data
Establish trend analysis procedures
Implement threshold-based alarm systems
Conduct regular performance evaluations using monitoring data

Advanced Monitoring Technologies

Automated Monitoring Stations: Reduce labor requirements and improve data consistency
Wireless Sensor Networks: Enable real-time monitoring from remote locations
Drone Surveys: Provide visual inspections of hard-to-reach areas
Satellite InSAR: Remote monitoring of surface deformations

8.2 Routine Maintenance Procedures

Routine maintenance ensures continued performance and extends the service life of clay core walls:

Surface Maintenance

Vegetation Control: Regular mowing and removal of woody plants
Surface Drainage Maintenance: Clean and repair drainage systems
Crack Repair: Prompt filling of surface cracks with suitable materials
Erosion Control: Repair erosion damage and maintain protective measures

Drainage System Maintenance

Outlet Structures: Regular inspection and cleaning
Drainage Pipes: Periodic flushing and inspection
Filter Materials: Inspection and replacement as needed
Underdrain Systems: Monitoring flow rates and water quality

Structural Element Maintenance

Crest Maintenance: Regular inspection and repair of crest surfaces
Parapet Walls: Inspection for cracks and proper drainage
Access Roads: Routine maintenance and repair
Instrumentation: Regular calibration and replacement of monitoring equipment

Specialized Maintenance Tasks

Grazing Management: Control of livestock access to dam structures
Wildlife Control: Measures to prevent burrowing animals from creating potential seepage paths
Snow and Ice Control: Management of snow accumulation and ice formation in cold climates
Vegetation Management: Strategic planting of erosion-resistant vegetation

8.3 Common Defects and Their Remediation

Despite proper design and construction, clay core walls may develop defects requiring remediation:

Surface Cracks

Causes: Drying shrinkage, differential settlement, frost action
Remediation:
- Clean cracks and fill with suitable sealing materials
- Apply protective coatings to prevent further cracking
- Implement improved surface drainage

Seepage Issues

Causes: Poor compaction, material defects, foundation issues
Remediation:
- Implement grouting programs to reduce seepage
- Install additional drainage systems
- Construct secondary barriers where feasible
- Implement surface sealing treatments

Erosion Damage

Causes: Surface runoff, wave action, ice damage
Remediation:
- Repair eroded areas with appropriate materials
- Improve drainage systems
- Install erosion protection measures
- Adjust vegetation management practices

Internal Erosion

Causes: Piping, suffusion, backward erosion
Remediation:
- Implement grouting programs to seal internal voids
- Improve filter systems to prevent particle migration
- Reduce hydraulic gradients through structural modifications
- Monitor closely for signs of continued internal erosion

Structural Deficiencies

Causes: Settlement, slope instability, earthquake damage
Remediation:
- Implement slope stabilization measures
- Construct additional buttresses or berms
- Strengthen foundations as needed
- Implement seismic upgrades where necessary

8.4 Rehabilitation and Retrofit Techniques

As clay core walls age or face changing requirements, various rehabilitation and retrofit techniques may be necessary:

Grouting Techniques

Compaction Grouting: Used to densify loose materials
Jet Grouting: For creating cutoff walls or strengthening foundations
Permeation Grouting: To reduce permeability in certain soils
Chemical Grouting: For fine-grained soils where traditional grouts are ineffective

Internal Remediation Methods

Slurry Trench Cutoff Walls: Constructed adjacent to existing cores for improved seepage control
Prefabricated Vertical Drains: To accelerate consolidation in soft foundations
Geosynthetic Reinforcement: To improve slope stability
Underwater Repair Techniques: For addressing issues without dewatering the reservoir

External Remediation Methods

Additional Impermeable Layers: Adding geomembranes or GCLs as secondary barriers
Increased Crest Height: To accommodate increased flood requirements
Improved Drainage Systems: To reduce seepage pressures
Enhanced Erosion Protection: Including riprap, revetments, or wave barriers

Rehabilitation Planning Considerations

Comprehensive Condition Assessment: Before developing rehabilitation plans
Risk Assessment: To prioritize necessary interventions
Alternatives Analysis: Considering multiple options before selecting the best approach
Staged Implementation: Where feasible, implement rehabilitation in phases
Monitoring During Rehabilitation: To evaluate effectiveness of interventions

8.5 Long-term Performance Assessment

Long-term performance assessment ensures that clay core walls continue to meet design requirements throughout their service life:

Assessment Methods

Periodic Inspections: Conducted by qualified professionals
Performance Evaluations: Comparing actual performance against design expectations
Condition Rating Systems: Quantitative methods for assessing overall condition
Risk-Based Assessment: Evaluating potential failure modes and consequences

Life Extension Strategies

Material Replacement: Replacing degraded materials in critical areas
System Upgrades: Incorporating modern monitoring and control systems
Structural Strengthening: Reinforcing vulnerable areas
Functional Upgrades: Modifying structures to meet changing requirements

Retirement Planning

Decommissioning Options: Evaluating the feasibility of dam removal or modification
Environmental Considerations: Assessing impacts of retirement on surrounding ecosystems
Public Safety Planning: Ensuring safe transition during decommissioning
Legal and Regulatory Compliance: Addressing all legal requirements for dam retirement

Lessons Learned from Aging Structures

Importance of Routine Maintenance: Regular care significantly extends service life
Value of Comprehensive Monitoring: Provides early warning of potential issues
Benefits of Material Quality: High-quality materials reduce long-term maintenance needs
Limitations of Original Designs: Older structures may not meet modern standards
Advantages of Periodic Upgrades: Incorporating new technologies enhances performance

9. Standards and Specifications

9.1 International Standardization Organizations

Several international organizations have established standards and guidelines relevant to clay core wall technology:

International Commission on Large Dams (ICOLD)

Publishes over 180 bulletins covering various aspects of dam engineering
Technical committees develop guidelines based on international best practices
Recent bulletins address topics such as dam decommissioning, seismic design, and roller-compacted concrete dams

International Organization for Standardization (ISO)

Technical Committee ISO/TC 221 focuses on geosynthetics
Develops standards for geosynthetic materials used in clay core wall construction
Standards cover materials, testing methods, and installation procedures

American Society for Testing and Materials (ASTM)

Develops standards for materials, products, systems, and services
Relevant standards include those for soils, concrete, geosynthetics, and construction materials
ASTM D6751 for geotextiles is particularly relevant to clay core wall construction

European Committee for Standardization (CEN)

Develops European Standards (EN) for construction materials and methods
Relevant standards include EN 13285 for unbound mixtures and EN 13361 for geosynthetic barriers
Standards ensure consistency across European construction practices

United States Army Corps of Engineers (USACE)

Publishes engineering manuals and regulations for dam construction
EM 1110-1-1804 addresses drilling in embankments
ER 1110-1-1807 provides guidance on drilling operations in dam and levee embankments

9.2 Key Design and Construction Standards

Several key standards provide detailed guidance for clay core wall design and construction:

Design Standards

ICOLD Bulletin 121: Clay Core Rockfill Dams: Provides comprehensive guidance on design considerations
ICOLD Bulletin 167: Design and Construction of Clay Core Dams: Focuses on modern design approaches
ASTM D5783: Standard Guide for Design and Construction of Earth-Filled Embankments: Provides general guidance for earth embankments
USACE Engineering Manual EM 1110-2-1902: Design of Small Dams: Covers design considerations for small dams

Material Standards

ASTM D4318: Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils: Defines methods for determining Atterberg limits
ASTM D698: Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort: Defines standard Proctor compaction test
ASTM D5084: Standard Test Methods for Measurement of Hydraulic Conductivity of Saturated Porous Materials Using Constant Head: Defines permeability testing methods
ISO 10319: Geosynthetics - Wide-width tensile test: Standard test method for geosynthetic materials

Construction Standards

ASTM D6928: Standard Practice for Use of Global Positioning System (GPS) Equipment in Construction: Provides guidance on GPS use in earthwork
EN 13361:2013: Geosynthetic barriers - Characteristics required for use in the construction of reservoirs and dams: Defines requirements for geosynthetic barriers in hydraulic structures
BS EN 13285:2010: Unbound mixtures - Specifications: Provides specifications for unbound materials used in earthworks
USACE Engineering Manual EM 1110-1-1904: Earth Embankment Construction: Provides detailed guidance on earth embankment construction

9.3 Testing and Quality Control Standards

Comprehensive testing and quality control standards ensure materials and construction meet design requirements:

Soil Testing Standards

ASTM D422: Standard Test Method for Particle-Size Analysis of Soils: Defines methods for grain size analysis
ASTM D2487: Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System): Provides soil classification system
ASTM D2166: Standard Test Method for Unconfined Compression Strength of Cohesive Soil: Defines method for determining unconfined compressive strength
ASTM D2850: Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions: Defines direct shear test method

Geosynthetic Testing Standards

ISO 10319: Geosynthetics - Wide-width tensile test: For determining tensile properties
ISO 13433: Geosynthetics - Puncture resistance test: For evaluating puncture resistance
ISO 13438: Geosynthetics - Seam strength determination: For testing seam integrity
EN 13361:2013: Geosynthetic barriers - Characteristics required for use in the construction of reservoirs and dams: Defines performance requirements

Field Testing Standards

ASTM D1556: Standard Test Method for Moisture Density Relations of Soil and Soil-Aggregate Mixtures Using a 4.54-kg (10-lb) Rammer and a 305-mm (12-in.) Drop: Field compaction test
ASTM D6938: Standard Test Method for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth): Nuclear densometer method
ASTM D1557: Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort: Modified Proctor compaction test
BS 1377: Methods of test for soils for civil engineering purposes: Comprehensive British standard for soil testing

9.4 Regional and National Variations

Standards and practices vary somewhat between regions and countries:

European Practices

Strong emphasis on environmental protection in dam construction
Detailed requirements for monitoring and documentation
Use of Eurocodes for structural design aspects
Specific standards for cold climate construction

North American Practices

USACE and ASTM standards heavily influence practice
Strong focus on public safety and risk management
Well-established procedures for dam safety evaluation
Comprehensive guidelines for seismic design

Asian Practices

Variability between countries based on local conditions and resources
Growing adoption of international standards alongside local practices
Innovative adaptations to challenging conditions including high rainfall and seismic activity
Increased focus on sustainability in recent projects

African Practices

Emerging standards based on a mix of international and colonial influences
Emphasis on cost-effective solutions using locally available materials
Adaptations to arid and semi-arid conditions
Increasing collaboration with international organizations

Key Regional Differences Summary

Material Specifications: Variations in acceptable material properties
Design Approaches: Different methods for stability analysis and seepage control
Construction Practices: Variations in equipment use and quality control procedures
Regulatory Requirements: Different levels of government oversight and compliance procedures
Safety Factors: Variations in required factors of safety for different loading conditions

9.5 Emerging Trends in Standardization

Standardization practices for clay core wall technology are evolving to address modern challenges:

Integrated Risk-Based Approaches

Transition from prescriptive to performance-based standards
Increased use of risk assessment in design and construction
Incorporation of probabilistic methods alongside deterministic approaches

Sustainability Considerations

Environmental impact assessment becoming standard practice
Carbon footprint considerations in material selection
Life cycle assessment requirements for major projects
Increased focus on biodiversity protection

Digital Transformation

Development of digital standards for BIM (Building Information Modeling) in dam construction
Integration of digital documentation and quality control systems
Standards for data management and exchange between project stakeholders

Advanced Materials and Methods

Development of standards for new materials and construction techniques
Guidelines for emerging technologies such as 3D printing and automated compaction control
Integration of renewable energy systems into dam infrastructure

Climate Change Adaptation

Updated design criteria considering changing climate conditions
Increased focus on extreme weather events in design standards
Guidance on drought and flood resilience in dam construction
Requirements for climate change impact assessment in dam projects

10. Conclusions and Recommendations

10.1 Summary of Key Findings

Based on the comprehensive analysis of clay core wall technology presented in this manual, several key findings emerge:

Material Science Insights

Clay core walls rely on the unique properties of clay materials including low permeability, plasticity, and self-healing capacity
Modern material science has expanded the range of clays that can be used through stabilization techniques
Material quality control remains critical to achieving design performance objectives

Design Evolution

Design approaches have evolved from empirical methods to sophisticated numerical modeling
Modern designs incorporate 3D finite element analysis considering complex loading conditions
Safety factors and performance criteria have evolved based on accumulated experience

Construction Advancements

Construction techniques have become more sophisticated with the incorporation of GPS tracking and automated compaction control
Innovative adaptations have been developed for challenging conditions including high-moisture content construction and wet compaction
Quality control has evolved from primarily visual inspection to comprehensive testing programs

Monitoring and Maintenance

Monitoring systems have evolved from simple manual observations to comprehensive automated systems
Routine maintenance has been shown to significantly extend the service life of clay core walls
Rehabilitation techniques have become more sophisticated allowing for targeted interventions

Technology Comparison

Clay core walls offer a balance between cost, performance, and longevity for many applications
Alternative technologies may offer advantages in specific circumstances including limited space or specialized performance requirements
Hybrid systems combining multiple technologies can often provide optimal solutions

10.2 Recommendations for Practice

Based on the analysis and case studies presented, the following recommendations are offered for engineering practice:

Design Recommendations

Comprehensive Geological Investigation: Always conduct thorough site investigations before finalizing designs
Material Selection Carefully: Base material selection on both technical and economic considerations
Integrated Design Approach: Consider the entire system including foundation, core, and shell in design
Performance-Based Criteria: Establish clear performance objectives rather than relying solely on prescriptive requirements
Seismic Design Considerations: Incorporate appropriate seismic design provisions for all new dams

Construction Recommendations

Implement Quality Control Systems: Establish comprehensive quality control programs from material source to final placement
Train Personnel Properly: Ensure all personnel involved in construction are adequately trained
Use Modern Equipment: Incorporate GPS tracking and automated compaction control where feasible
Weather Management Plan: Develop strategies for dealing with adverse weather conditions
Comprehensive Documentation: Maintain detailed records of all construction activities and test results

Monitoring and Maintenance Recommendations

Install Comprehensive Monitoring: Implement monitoring systems appropriate for the dam's size and importance
Establish Routine Maintenance Programs: Regular maintenance significantly extends service life
Develop Emergency Response Plans: Prepare for potential failures or emergencies
Periodic Performance Evaluations: Regularly compare actual performance against design expectations
Implement Early Warning Systems: Use monitoring data to identify potential issues before they become critical

Technology Selection Recommendations

Consider Project-Specific Factors: Evaluate each project based on its unique characteristics
Hybrid Systems Consideration: Do not limit consideration to single technologies; hybrid systems often provide optimal solutions
Life Cycle Costs Analysis: Consider the full life cycle costs rather than just initial construction costs
Local Resources Utilization: Where feasible, use locally available materials and expertise
Sustainability Integration: Incorporate sustainability considerations into technology selection

10.3 Future Research Needs

Several areas warrant further research to advance the state of the art in clay core wall technology:

Material Research Needs

Development of improved stabilization methods for problematic clays
Investigation of nanotechnology applications in clay materials
Development of self-healing clay composites
Improved understanding of long-term material aging processes

Design Research Needs

Development of improved constitutive models for clay behavior
Better understanding of core-shell interaction mechanisms
Improved methods for predicting long-term performance
Development of risk-informed design approaches

Construction Research Needs

Innovation in construction methods for challenging conditions
Development of automated quality control systems
Improved techniques for cold weather and high-moisture content construction
Integration of artificial intelligence in construction management

Monitoring and Maintenance Research Needs

Development of advanced sensors for early detection of internal erosion
Improvement of non-destructive testing methods for core integrity assessment
Innovation in remote monitoring technologies
Development of optimized maintenance strategies using machine learning

Sustainability Research Needs

Evaluation of environmental impacts of clay core wall construction
Development of sustainable material sourcing strategies
Investigation of carbon sequestration potential in clay materials
Integration of renewable energy systems with dam infrastructure

10.4 Closing Remarks

Clay core wall technology represents a fundamental and enduring solution for seepage control in hydraulic engineering. Despite the development of modern alternative technologies, properly designed and constructed clay core walls continue to provide reliable, cost-effective performance for a wide range of applications.

The technology has evolved significantly over the past century, incorporating advances in material science, design methods, construction techniques, and monitoring systems. This evolution continues as engineers adapt to new challenges including climate change, sustainability requirements, and the need for improved performance in challenging conditions.

The key to successful clay core wall implementation lies in careful consideration of site-specific conditions, appropriate material selection, rigorous quality control during construction, and comprehensive monitoring throughout the structure's life cycle. By applying these principles, engineers can continue to rely on clay core walls as a cornerstone of hydraulic engineering for decades to come.

As with any technology, clay core walls have limitations and are not suitable for every application. However, when properly applied, they offer an effective, economical, and sustainable solution for controlling seepage in dams and other hydraulic structures. The continued advancement of clay core wall technology will depend on ongoing research, innovation, and the application of lessons learned from past experiences.

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[14] Study on Fracture and Seepage Evolution Law of Stope Covered by Thin Bedrock under Mining Influence https://www.semanticscholar.org/paper/Study-on-Fracture-and-Seepage-Evolution-Law-of-by-Li-Wang/b84c5cc4104d778a11166216d3e643661a8b0618

[15] Experimental and numerical simulation of solute transport in non-penetrating fractured clay https://pubmed.ncbi.nlm.nih.gov/36042290/

[16] Canales Dam clay core | Roctest https://roctest.com/en/canales-dam-clay-core/

[17] Pant-Yr-Eos Reservoir (2022) | Water Projects https://waterprojectsonline.com/custom_case_study/pant-yr-eos-2022/

[18] 分散性黏土在麦洛维工程黏土心墙坝中的应用(pdf) http://www.scslfd.com/webapp/accessory/ueditor/upload/file/20191030/1572418824883008306.pdf

[19] 斐济蒙拉加堆石坝高含水量粘土心墙料及其施工方法(pdf) http://www.scslfd.com/webapp/accessory/ueditor/upload/file/20191023/1571811109712050640.pdf

[20] 乌干达伊辛巴水电站黏土心墙堆石坝设计关键点_陈伟 - 道客巴巴 https://m.doc88.com/p-97787036258010.html

[21] 喀麦隆曼维莱水电站黏土心墙堆石坝反滤料、过渡料和堆石料设计研究论文电子版下载 - 道客巴巴 https://m.doc88.com/p-5784713305800.html

[22] 安哥拉凯凯水电站进入基坑开挖阶段_中国新闻网 http://m.toutiao.com/group/7287147415026041398/?upstream_biz=doubao

[23] 超高含水率黏土在斐济维尼撒乌勒乌水电站心墙堆石坝中的应用(pdf) http://www.scslfd.com/webapp/accessory/ueditor/upload/file/20211102/1635838183538017324.pdf

[24] 伊朗塔里干粘土心墙土石坝 - 道客巴巴 https://m.doc88.com/p-8196876476608.html

[25] Guajataca Dam (Puerto Rico, 2017) | Case Study | ASDSO Lessons Learned https://damfailures.org/case-study/guajataca-dam-puerto-rico-2017/

[26] Clay core dam https://www.wp1.en-us.nina.az/Clay_core_dam.html

[27] (PDF) Behavior of an Earth Dam during Rapid Drawdown of Water in Reservoir – Case Study https://www.researchgate.net/publication/282646639_Behavior_of_an_Earth_Dam_during_Rapid_Drawdown_of_Water_in_Reservoir_-_Case_Study

[28] Fort Peck Dam (Montana, 1938) | Case Study | ASDSO Lessons Learned https://damfailures.org/case-study/fort-peck-dam-montana-1938/

[29] Water Wise farmers build earth dams: Part 7 – The core of the dam and construction methods – ProAgri Media https://www.proagrimedia.com/innovation/water-wise-farmers-build-earth-dams-part-7-the-core-of-the-dam-and-construction-methods/

[30] E7 - Construction of small surface dams - Wikiwater https://wikiwater.fr/e7-construction-of-small-surface

[31] Cofferdams-Types of Cofferdam and construction | vin civilworld https://vincivilworld.com/2022/11/29/cofferdams-types-construction-methods/

[32] A Revisit to the Swedish Wet Compaction Method—A Case Study of the Burvattnet Dam Reconstruction https://www.scirp.org/journal/paperinformation?paperid=125535

[33] How fill dam is made - material, making, history, used, processing, dimensions, product, History, Raw Materials http://www.madehow.com/Volume-5/Fill-Dam.html

[34] C212 Standard Specification for Structural Clay Facing Tile https://www.astm.org/standards/c212

[35] ASTM-C34 | Standard Specification for Structural Clay Loadbearing Wall Tile | Document Center, Inc. https://www.document-center.com/standards/show/ASTM-C34

[36] ASTM C652-17 - Standard Specification for Hollow Brick (Hollow Masonry Units Made From Clay or https://standards.iteh.ai/catalog/standards/astm/9bb185ce-cf40-4c94-9ac4-58deb3f7dbb2/astm-c652-17?reviews=true

[37] Select the best excavation wall type | Deep Excavation https://www.deepexcavation.com/select-the-best-wall-type-for-your-project

[38] Comparison between Soldier Pile and Diaphragm Wall http://www.linkedin.com/pulse/comparison-between-soldier-pile-diaphragm-wall-huy-tr%C6%B0%C6%A1ng

[39] Diaphragm Wall vs. Sheet Piling in Retaining Structures: Which One is Right for Your Project? - Hindustan RMC https://hindustanrmc.com/diaphragm-wall-vs-sheet-piling/

[40] ICOLD Dam Decommissioning - Guidelines - 1st Edition - CIGB ICOLD - Ro https://www.routledge.com/ICOLD-Dam-Decommissioning---Guidelines/ICOLD/p/book/9781138491205

[41] Geotextile Specifications - Geofantex https://geofantex.com/geotextile-specifications.html

[42] Documents - 117F Woven Geosynthetic Specification https://www.adspipe.com/resources/documents/739F2AC8-A056-4F7D-B355814AEF3D03AC

[43] Applications of Geosynthetics to Irrigation, Drainage and Agriculture - Blond - 2019 - Irrigation and Drainage - Wiley Online Library https://onlinelibrary.wiley.com/doi/full/10.1002/ird.2300

[44] BS en 13285 - 2010 Unbound Mixtures - Specs - PDFCOFFEE.COM https://pdfcoffee.com/bs-en-13285-2010-unbound-mixtures-specs-pdf-free.html

[45] ISO/TC 221 - Geosynthetics https://www.iso.org/committee/270590.html

[46] EN 13361:2013 - Geosynthetic barriers - Characteristics required for use in the construction of https://standards.iteh.ai/catalog/standards/cen/a56715f6-5e4f-4e7f-b2dd-41bd3ef42caf/en-13361-2013

[47] CSN EN ISO 10319 - Geosynthetics - Wide-width tensile test https://www.en-standard.eu/csn-en-iso-10319-geosynthetics-wide-width-tensile-test/?srsltid=AfmBOorCrtTfv01ZKAYbz0_qumG3g17GI1iiCaNfh7yVQrXrHwtzVWUw

[48] ISO 10319: Tensile strength testing laboratories - Analytice https://www.analytice.com/en/iso-10319-tensile-strength-testing-laboratories/

[49] DS/EN ISO 10319 - Geosynthetics - Wide-width tensile test | GlobalSpec https://standards.globalspec.com/std/9996071/ds-en-iso-10319

[50] ISO 10319 Geosynthetics — Wide Width Tensile Test https://www.laboratuar.com/en/testler/malzeme-testleri/iso-10319-geosentetikler-%E2%80%94-genis-genislikte-cekme-testi/

[51] ISO 10319:2024 - Geosynthetics — Wide-width tensile test https://www.iso.org/standard/82237.html

[52] Diaphragm Wall Construction: Benefits, Cost, FAQs https://www.99acres.com/articles/diaphragm-wall-construction.html

[53] Comparing the construction cost of concrete block, clay brick, & AAC block walls. ~ PARAM VISIONS https://www.paramvisions.com/2021/06/comparing-construction-cost-of-concrete.html

[54] How Much Do Precast Concrete Walls Cost? - Estimate Florida Consulting https://estimatorflorida.com/how-much-do-precast-concrete-walls-cost/

[55] The Soil-Bentonite Advantage in Diaphragm Wall Construction - Hindustan RMC https://hindustanrmc.com/soil-bentonite-diaphragm-wall-construction/

[56] A comprehensive comparison of Geosynthetic Clay Liners VS Geomembranes https://www.ecogeox.com/resources/a-comprehensive-comparison-of-geosynthetic-clay-liners-vs-geomembranes.html

[57] What is a dam liner? - tinhygeosynthetics.com https://tinhygeosynthetics.com/blog-news/what-is-a-dam-liner/

[58] HDPE Geomembrane vs. Traditional Clay Impermeabilization https://www.linkedin.com/pulse/hdpe-geomembrane-vs-traditional-clay-carmen-real-romera

[59] Geomembrane sealing systems for dams - Geosynthetics Magazine https://geosyntheticsmagazine.com/2008/04/01/geomembrane-sealing-systems-for-dams/

[60] Comparing Geomembranes for Floating Covers https://www.ecogeox.com/resources/comparing-geomembranes-for-floating-covers.html

[61] Light Clay Straw Primer: Building Light Clay Straw Walls | The Year of Mud https://theyearofmud.com/2016/09/28/light-clay-straw-wall-building/

[62] How To Lay Porotherm Clay Blocks | wienerberger UK https://www.wienerberger.co.uk/tips-and-advice/blockwork/how-do-you-lay-clay-blocks.html

[63] What is rammed earth construction & how to build a wall step by step? https://www.hiveearth.com/post/what-s-coming-up

[64] ‎ICOLD Dam Decommissioning - Guidelines by CIGB ICOLD on Apple Books https://books.apple.com/us/book/icold-dam-decommissioning-guidelines/id1540676443

[65] ICOLD Dam Decommissioning - Guidelines (ICOLD Bulletins Series): ICOLD, CIGB: 9781138491205: Amazon.com: Books https://www.amazon.com/ICOLD-Dam-Decommissioning-Guidelines-Bulletins/dp/1138491209

[66] Understanding the Cost-Effectiveness of Diaphragm Wall Construction - Hindustan RMC https://hindustanrmc.com/cost-effectiveness-of-diaphragm-wall-construction/

[67] 2025 Concrete Retaining Wall Cost — Poured, Large Blocks & Interlocking https://homeguide.com/costs/concrete-retaining-wall-cost

[68] Geosynthetic Clay Liner vs Geomembrane | Geosynthtics For Sale https://www.bpmgeosynthetics.com/what-is-difference-geosynthetic-clay-liner-vs-geomembrane/

[69] Why Natural Liners and Clay Soils Aren’t Enough for Recreational Ponds https://www.btlliners.com/why-natural-liners-and-clay-soils-arent-enough-for-recreational-ponds

[70] Geomembrane Liner And Clay Liner Used For Landfill • QIVOC https://qivoc.com/geomembrane-liner-and-clay-liner-used-for-landfill/

[71] Performance of GCLS in liners for landfill and mining applications | Environmental Geotechnics https://www.icevirtuallibrary.com/doi/full/10.1680/envgeo.13.00031

[72] Comparative analysis of bentonite waterproof blanket and geomembrane http://www.linkedin.com/pulse/comparative-analysis-bentonite-waterproof-blanket-geomembrane-lee

[73] EM 1110-1-18041 Jan 015-6 https://www.yumpu.com/en/document/view/65315470/em-1110-1-1804/82

[74] Dam Safety Program > U.S. Army Corps of Engineers Headquarters > Dam Safety Program https://www.usace.army.mil/Missions/Civil-Works/Dam-Safety-Program/

[75] 3D Nonlinear Analysis of Atatürk Clay Core Rockfill Dam Considering Settlement Monitoring | International Journal of Geomechanics | Vol 19, No 5 https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GM.1943-5622.0001412?mi=3brfot

[76] Full article: Investigation of riprap stability of a dam: risk assessment by InSAR method and rock mechanical test https://www.tandfonline.com/doi/full/10.1080/19475705.2022.2077145

[78] ICOLD Dam Decommissioning - Guidelines | CIGB ICOLD | Taylor & Francis https://www.taylorfrancis.com/books/edit/10.1201/9781351033664/icold-dam-decommissioning-guidelines-cigb-icold

[79] [PDF] The cost management of rockfill dam with clay core and concrete face and the economical comparison of these two methods (Case Study: Jere dam of Ramhormoz) | Semantic Scholar https://www.semanticscholar.org/paper/The-cost-management-of-rockfill-dam-with-clay-core-Mousavi-Pakbaz/03101cdd1330a140d7d7cfb9de673a096a3eda48

[80] Hindustan RMC | Diaphragm Wall | Dwall construction https://hindustanrmc.com/diaphragm-wall

[81] Cost to build a dam - kobo building https://kobobuilding.com/cost-to-build-a-dam/

[82] Seepage through Earth Filled Dams | Seepage Control in Da,s https://www.aboutcivil.org/seepage-through-earth-filled-dams.html

[83] Diaphragm Walls in Deep Excavations https://www.deepexcavation.com/post/diaphragm-walls-in-deep-excavations

[84] (PDF) Seepage analysis of clay core wall dam based on ABAQUS https://www.researchgate.net/publication/337645393_Seepage_analysis_of_clay_core_wall_dam_based_on_ABAQUS

[85] Integrated Leakage Control Technology for Underground Structures in Karst Terrains: Multi-Stage Grouting and Zoned Remediation at Guangzhou Baiyun Metro Station https://www.mdpi.com/2075-5309/15/13/2239

[86] Publications | USSD | United States Society on Dams https://www.ussdams.org/resource-center/publications/

[87] Official Series Description - DU_PAGE Series https://soilseries.sc.egov.usda.gov/OSD_Docs/D/DU_PAGE.html

[88] Official Series Description - COWOOD Series https://soilseries.sc.egov.usda.gov/OSD_Docs/C/COWOOD.html

[89] ICOLD Bulletins Series - Book Series - Routledge & CRC Press https://www.routledge.com/ICOLD-Bulletins-Series/book-series/ICOLD?a=1&pg=2

[90] About the International Commission on Large Dams https://britishdams.org/about/about-icold/

[92] Full text of "The design and construction of dams, including masonry, earth, rock-fill, timber, and steel structures, also the principal types of movable dams" https://archive.org/stream/designandconstr00wegmgoog/designandconstr00wegmgoog_djvu.txt

[93] Roller-Compacted Concrete Dams eBook by - EPUB Book | Rakuten Kobo United States https://www.kobo.com/us/en/ebook/roller-compacted-concrete-dams

[94] (PDF) Update on ICOLD Embankment Dam Technical Committee Works https://www.researchgate.net/publication/340803907_Update_on_ICOLD_Embankment_Dam_Technical_Committee_Works

[95] ICOLD Position Paper On Dam Safety and Earthquakes (ICOLD Committee) PDF - PDFCOFFEE.COM https://pdfcoffee.com/icold-position-paper-on-dam-safety-and-earthquakes-icold-committee-pdf-pdf-free.html

[96] Full text of "The design and construction of dams; including masonry, earth, rock-fill, and timber structures, also the principal types of movable dams" https://archive.org/stream/cu31924004974840/cu31924004974840_djvu.txt

[97] Dam Safety Management / Gestion de la Sécurité des Barrages eBook by Cigb Icold - EPUB Book | Rakuten Kobo United States https://www.kobo.com/us/en/ebook/dam-safety-management-gestion-de-la-securite-des-barrages

[98] ICOLD Dam Decommissioning - Guidelines eBook by - EPUB Book | Rakuten Kobo United States https://www.kobo.com/us/en/ebook/icold-dam-decommissioning-guidelines

[99] ICOLD Dam Decommissioning - Guidelines a book by Cigb Icold - Bookshop.org US https://bookshop.org/p/books/icold-dam-decommissioning-guidelines-cigb-icold/12243330

[101] ICOLD - Roller Compacted Concrete Dams - DRAFT - PDFCOFFEE.COM https://pdfcoffee.com/icold-roller-compacted-concrete-dams-draft-pdf-free.html

[102] Earth Dams - PDFCOFFEE.COM https://pdfcoffee.com/earth-dams-2-pdf-free.html

[103] Maryland Stormwater Design Manual https://mde.maryland.gov/programs/water/StormwaterManagementProgram/Pages/stormwater_design.aspx

[104] Internal erosion vulnerability of core soil due to drought: Case study of three zoned dams https://www.scirea.org/journal/PaperInformation?PaperID=6201

[105] Full text of "Engineering Journal 1943" https://archive.org/stream/engineeringjourn26engi/engineeringjourn26engi_djvu.txt

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