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The Legacy of James L. Sherard: A Pioneer in Embankment Dam Engineering
Embankment Dams: James L. Sherard Contributions
Embankment dams are structures that use natural materials such as soil, rock, or sand to retain water or other fluids. They are widely used for irrigation, hydroelectric power, flood control, and water supply purposes. Embankment dams can be classified into two main types: earthfill dams and rockfill dams. Earthfill dams use mostly compacted soil to form the dam body, while rockfill dams use mostly coarse rock fragments. Both types of embankment dams require some form of impervious core or facing to prevent seepage and erosion.
Embankment Dams : James L. Sherard Contributions
James L. Sherard was a renowned civil engineer and professor who made significant contributions to the field of embankment dam engineering. He was born in 1918 in Colorado and graduated from the University of Colorado in 1940 with a degree in civil engineering. He worked as a design engineer for the Bureau of Reclamation and later joined the consulting firm of Woodward-Clyde-Sherard and Associates. He also taught at several universities, including Stanford University, where he was a professor of civil engineering from 1966 to 1984. He received many honors and awards for his achievements, such as the Norman Medal and the Terzaghi Lecture Award from the American Society of Civil Engineers.
Sherard published more than 100 papers on various aspects of embankment dam engineering, such as seismic design, dispersive clays, hydraulic fracturing, filters, and concrete face rockfill dams. His papers were influential and widely cited by researchers and practitioners around the world. He also participated in many projects involving embankment dams, such as the Tarbela Dam in Pakistan, the New Melones Dam in California, and the Itaipu Dam in Brazil.
This article will review some of the major contributions of James L. Sherard to embankment dam engineering and highlight his legacy and impact on the profession.
Seismic Design of Embankment Dams
One of the challenges of embankment dam engineering is to ensure the stability and safety of the dams under earthquake loading. Sherard was one of the pioneers who recognized the importance of seismic design and conducted extensive research on this topic. He developed analytical methods and empirical criteria for evaluating the seismic response and deformation of embankment dams. He also proposed guidelines for selecting appropriate seismic parameters, such as peak ground acceleration, response spectra, and seismic coefficients.
One of his seminal papers on this topic was "Earthquake Resistance of Earth and Rock-Fill Dams", which he co-authored with J.M. Clough in 1974. In this paper, they presented a comprehensive review of the state-of-the-art knowledge on seismic design of embankment dams at that time. They discussed the factors affecting the seismic behavior of embankment dams, such as material properties, geometry, foundation conditions, reservoir effects, and pore water pressure. They also summarized the results of laboratory tests, field measurements, and numerical analyses on various types of embankment dams subjected to earthquake loading. They provided recommendations for seismic design criteria, methods of analysis, and performance evaluation.
This paper was widely referenced and used by engineers and researchers involved in seismic design of embankment dams. It also stimulated further research and development on this topic in subsequent years.
Dispersive Clays
Another challenge of embankment dam engineering is to deal with problematic soils that may cause instability or failure of the dams. One such soil is dispersive clay, which is a type of clay that tends to disperse or break down into fine particles when exposed to water. Dispersive clays can cause serious problems for embankment dams, such as erosion, piping, cracking, slumping, and loss of strength.
Sherard was one of the first engineers who identified and studied the phenomenon of dispersive clays in relation to embankment dam engineering. He developed methods for detecting and classifying dispersive clays based on laboratory tests, such as the pinhole test, the crumb test, and the double hydrometer test. He also investigated the mechanisms and factors influencing the dispersion behavior of clays, such as mineralogy, chemistry, salinity, pH, organic matter, compaction, and curing.
One of his influential papers on this topic was "Identification and Nature of Dispersive Soils", which he co-authored with R.B. Peck in 1971. In this paper,
Hydraulic Fracturing
Hydraulic fracturing is a process that involves injecting pressurized fluid into a soil or rock mass to create or propagate cracks. Hydraulic fracturing can occur naturally or artificially, and can have beneficial or detrimental effects on embankment dams. Hydraulic fracturing can be used to improve the permeability and drainage of foundation soils or rocks, to reduce uplift pressure and seepage, and to enhance grouting efficiency. However, hydraulic fracturing can also cause damage to the dam body or foundation, such as cracking, settlement, leakage, and loss of strength.
Sherard was one of the leading experts who investigated the phenomenon of hydraulic fracturing in relation to embankment dam engineering. He conducted laboratory and field experiments to study the mechanisms and factors influencing hydraulic fracturing, such as fluid properties, injection rate, confining stress, and soil or rock characteristics. He also developed analytical and empirical methods for predicting the onset and extent of hydraulic fracturing, and for evaluating its effects on embankment dam performance.
One of his important papers on this topic was "Hydraulic Fracturing in Embankment Dams", which he co-authored with L.P. Dunnigan in 1985. In this paper, they presented a comprehensive review of the state-of-the-practice knowledge on hydraulic fracturing in embankment dams at that time. They discussed the causes and consequences of hydraulic fracturing, the methods of detection and measurement, the criteria and models for analysis and design, and the techniques for prevention and remediation. They also provided case histories of embankment dams that experienced hydraulic fracturing problems, such as the Teton Dam in Idaho, the Tarbela Dam in Pakistan, and the New Melones Dam in California.
This paper was a valuable reference and guide for engineers and researchers involved in hydraulic fracturing issues in embankment dams. It also stimulated further research and development on this topic in subsequent years.
Filters
Filters are layers of granular material that are placed within or around an embankment dam to prevent or control the erosion of fine particles from the dam body or foundation. Filters are essential components of embankment dam design and construction, as they provide stability, safety, and durability to the dams. Filters can be classified into two main types: internal filters and external filters. Internal filters are located within the dam body, such as between the core and the shell, or within the core itself. External filters are located around the dam body, such as under the upstream slope, along the downstream toe, or within the drainage system.
Sherard was one of the foremost authorities who developed and advanced the theory and practice of filters for embankment dams. He conducted extensive research on the properties and functions of filters, such as gradation, permeability, retention, self-healing, compatibility, and effectiveness. He also proposed criteria and methods for designing and testing filters for various types of embankment dams, such as earthfill dams, rockfill dams, concrete face rockfill dams, and dispersive clay dams.
One of his classic papers on this topic was "Filters for Silts and Clays", which he co-authored with R.J. Woodward in 1963. In this paper,
This paper was a breakthrough in the field of filter design and has been widely adopted and cited by engineers and researchers ever since. It also led to further research and development on filters for embankment dams in subsequent years.
Concrete Face Rockfill Dams
Concrete face rockfill dams are a type of embankment dams that use a concrete slab as the impervious facing on the upstream slope of a rockfill dam. Concrete face rockfill dams have several advantages over conventional embankment dams, such as lower cost, faster construction, better adaptability to foundation conditions, and higher resistance to seismic loading. Concrete face rockfill dams are suitable for large heights and volumes, and have been used for many major projects around the world.
Sherard was one of the leading experts who developed and advanced the theory and practice of concrete face rockfill dams. He conducted extensive research on the design and performance of concrete face rockfill dams, such as the analysis of stresses and deformations, the selection and placement of materials, the design of joints and drainage systems, and the evaluation of seepage and stability. He also participated in many projects involving concrete face rockfill dams, such as the Mica Dam in Canada, the New Cornelia Dam in Arizona, and the Itaipu Dam in Brazil.
One of his last papers on this topic was "Concrete Face Rockfill Dams-Design, Construction, and Performance", which he co-authored with J.R. Cooke in 1987. In this paper, they presented a comprehensive review of the state-of-the-art knowledge on concrete face rockfill dams at that time. They discussed the history and development of concrete face rockfill dams, the advantages and disadvantages of this type of dams, the design criteria and methods, the construction techniques and quality control, and the performance evaluation and monitoring. They also provided case histories of several concrete face rockfill dams that were built or under construction around the world.
This paper was a valuable reference and guide for engineers and researchers involved in concrete face rockfill dam projects. It also reflected the culmination of Sherard's contributions to this field.
Conclusion
James L. Sherard was a distinguished civil engineer and professor who made outstanding contributions to the field of embankment dam engineering. He published more than 100 papers on various aspects of embankment dam engineering, such as seismic design, dispersive clays, hydraulic fracturing, filters, and concrete face rockfill dams. His papers were influential and widely cited by researchers and practitioners around the world. He also participated in many projects involving embankment dams, such as the Tarbela Dam in Pakistan, the New Melones Dam in California, and the Itaipu Dam in Brazil.
Sherard's contributions to embankment dam engineering have enhanced the knowledge and practice of the profession. He has left a lasting legacy and impact on the field of embankment dam engineering. He is widely respected and admired by his peers and students. He is a role model and an inspiration for future generations of civil engineers. b99f773239
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