Design and construction of compacted shale embankments. Vol. 1, Survey of problem areas and current practices : SHAMBURGER, JH PATRICK, DM LUTTON, RJ US ARMY ENGINEERING WATERWAYS ESPERIMENT STATION INTERIN REPORT, AUG. 1975, 307P. PB-253120

Abstract

The purpose of the three-phase study is to develop design and construction methodologies that will enable shales causing settlements and slope failure in highway embankments in the past to be identified and used successfully in future construction. During the first year's work (Phase I), state and federal agencies were contacted. Information obtained on the extent and types of problems, possible causes, and problem formations is discussed, and current highway practices are summarized. Physical and chemical weathering of shale placed as rock fill is a primary cause of problems. Nine states do not permit shale to be placed as rock fill, and seven states allow placement as rock fill with special provisions. Corps of Engineers and Bureau of Reclamation experiences indicate that heavy compaction equipment and relatively thin lifts produce well compacted embankments having no problems. Data from 16 projects indicate that saturated compacted shale materials have low shear strengths. A review of shale composition, factors contributing to degradation, and laboratory testing emphasizes the importance of mineralogy and slake-durability characteristics. The natural variability of shales collected from formations in five geologic age groups is described.