Embankment dams are structures that use earth or rock materials to retain water or other fluids. They are widely used for irrigation, water supply, flood control, hydropower, and recreation purposes. Embankment dams can be classified into different types based on their design, materials, and construction methods.
One of the most influential figures in the field of embankment dam engineering was Dr. James L. Sherard, who passed away in 2002. He was a renowned geotechnical engineer, educator, and consultant who made significant contributions to the theory and practice of embankment dam engineering. He authored or co-authored more than 200 publications on various aspects of soil mechanics, foundation engineering, and dam engineering.
This article will highlight some of the major contributions of Dr. Sherard to the advancement of embankment dam engineering. These include:
His pioneering research on the behavior and design of earth dams on rock foundations, especially on the effects of foundation deformability, jointing, and seepage.
His development of the concept of critical filters and filter compatibility for internal and external stability of embankment dams.
His innovation of the observational method for monitoring and controlling the performance of embankment dams during construction and operation.
His leadership and participation in numerous committees, panels, and boards that established standards and guidelines for embankment dam engineering.
His mentorship and inspiration of many students and young engineers who became leaders in the profession.
To honor his legacy, a memorial volume titled \"Embankment Dams : James L. Sherard Contributions\" was published in 2003 by the American Society of Civil Engineers (ASCE). This volume contains 21 selected papers by Dr. Sherard related to embankment dam engineering. These papers cover a wide range of topics such as soil mechanics, foundation engineering, seepage analysis, slope stability, filter design, instrumentation, performance evaluation, risk assessment, and case histories. These papers are considered seminal works that have influenced the state-of-the-art and state-of-the-practice of embankment dam engineering.
The memorial volume is a valuable resource for anyone interested in learning more about the principles and applications of embankment dam engineering. It is also a tribute to the remarkable achievements and contributions of Dr. Sherard to this important field of civil engineering.
Behavior and Design of Earth Dams on Rock Foundations
One of the main areas of research and practice of Dr. Sherard was the behavior and design of earth dams on rock foundations. He recognized that the foundation conditions have a significant influence on the stability and performance of embankment dams. He conducted extensive field investigations, laboratory tests, and numerical analyses to study the effects of foundation deformability, jointing, and seepage on the stress distribution, settlement, cracking, and leakage of earth dams.
Some of his notable contributions in this field are:
He developed a method for estimating the modulus of deformation of rock foundations based on rock quality designation (RQD) and uniaxial compressive strength.
He proposed a criterion for assessing the potential for hydraulic fracturing of rock foundations due to reservoir water pressure.
He introduced a concept of equivalent permeability for jointed rock masses and derived an empirical formula for estimating it based on joint spacing and aperture.
He analyzed several case histories of earth dams on rock foundations and identified the causes and mechanisms of distress and failure.
He provided practical recommendations for improving the design and construction of earth dams on rock foundations, such as grouting, drainage, filters, zoning, compaction, and instrumentation.
His papers on this topic are considered classics in the literature and have been widely cited and applied by engineers and researchers around the world.
Critical Filters and Filter Compatibility
Another major contribution of Dr. Sherard was the development of the concept of critical filters and filter compatibility for internal and external stability of embankment dams. He realized that the conventional criteria for filter design based on particle size ratios were inadequate and often resulted in excessive or insufficient filtering action. He proposed a new approach based on the concept of critical void ratio, which is the minimum void ratio at which a soil can be compacted without changing its gradation.
Some of his key findings and recommendations in this field are:
He defined a critical filter as a filter that has a critical void ratio equal to or slightly greater than that of the base soil.
He established a method for determining the critical void ratio of a soil by conducting compaction tests at different moisture contents.
He developed a criterion for filter compatibility based on comparing the critical void ratios of the filter and base soils.
He demonstrated that filter compatibility is more important than particle size ratios for preventing piping and erosion of base soils.
He suggested guidelines for selecting and testing filter materials for embankment dams.
His papers on this topic are considered groundbreaking in the field and have influenced the development of standards and codes for filter design for embankment dams. 29c81ba772