Seepage Monitoring and Analysis of Embankment Dams: On-Demand
Some amount of seepage passes through and under all embankment dams. The collection, monitoring, and analysis of seepage is crucial in the successful execution of any dam safety program and is helpful in deciding if it is expected ambient seepage or indicative of a more serious condition. Seepage collection methods typically include toe drains, blanket drains, and relief wells. Monitoring schemes can be grouped into several categories including; pressure, flow, temperature, and chemistry. Commonly used methods to collect data for each of these categories are; piezometers, transducers (pressure); weirs, flumes (flow); thermocouples (temperature); and stiff diagrams (chemistry). Upon collecting data from these methods one then conducts an analysis to determine if the performance meets 'design intent' or if it indicates the dam is in distress and repair is required. Since all dams and their foundations are different, there is no standard methodology for analysis and these studies tend to be 'investigative' in nature. This course will provide a background on collection methods including layout, access, and sediment collection techniques for toe drains and maintenance concerns associated with relief wells. Additionally an overview of monitoring methods and instruments will be made, including typical presentation methods. Finally, an overview of analysis methodologies will be presented, as well as for two case histories.
Mark W. Pabst, P.E.
Mark Pabst has over 35 years experience in geotechnical engineering and is presently a senior technical specialist in that field at the Risk Management Center of USACE. There, he is involved in the review, training, research, and implementation of geotechnical issues related to the Corps dam safety program. Prior to that position he was with Reclamation for 24 years and worked in the soils lab developing test procedures and equipment prior to joining the Geotechnical Engineering Group. In that position he was responsible for safety of dams investigations, analysis, design, construction review, and refill monitoring, as well as feasibility design of several proposed large dams. He is also a contributing author on several interagency manuals addressing the use of filters and drains in embankment dams as well as a number of USACE and Reclamation design manuals. Prior to joining Reclamation, he worked for geotechnical consulting firms in Chicago and New York City. Mr. Pabst obtained a BSCE (1978) and MSCE (1981) from Oklahoma State University and a MSGE (1985) from Iowa State University. He has authored 21 technical papers and made numerous presentations on geotechnical engineering, risk analysis, and dam safety.