Considerations for Internal Erosion and Observations of Particle Migration on Bennett South Moraine Sand

ABSTRACT: Dam owners have a responsibility to manage their dams to a standard where the risks associated with dam failure are as low as reasonably practicable; this includes identifying and assessing the risk associated with internal erosion. Internal erosion is responsible for approximately 35% of all earth embankment dam failures worldwide. In current practice, empirical screening tools are available to assess material susceptibility to internal erosion. Current research now focuses on development of a mechanics-based understanding of such erosion processes, to advance the management of internal erosion risks. Experimental testing was carried out on granular materials obtained from the W.A.C. Bennett Dam south moraine borrow source to develop a mechanics-based understanding of internal instability. An index void ratio test program was carried out on gap-graded BSM sand to characterize the sand in loose and dense states and assess the effect of changing finer fraction content on the void ratio of a gap graded mixture. During testing, quantifiable particle migration was observed and measured. This paper presents a review of experimental findings and discusses the implications relating to internal erosion and considerations for index test methodologies for gap-graded soils.