Understanding the Behavior of Embankment Dams Under Blast Loading

This purpose of this study is to investigate the deformation-induced stability of earthen embankment dams to explosive airblast loading. This study specifically investigated the effects of close-in explosive airblast loads on the downstream toe of a homogeneous earthen embankment dam composed of cohesive soils. Small-scale explosive airblast experiments were performed on cohesive soils to obtain an experimental data set with which to compare numerical analyses. Experimental measurements included crater geometry, ground vibration energy, and air overpressure from the blast events. Laboratory tests were conducted on the experiment soils to obtain engineering properties including shear strength and compressibility indices. Finite element simulations of airblast loading on a cohesive soil embankment dam were performed using Multi-Material Arbitrary Lagrangian Eulerian (MM-ALE) methods in LS-DYNA and compared to experimental results. Blast effects on varying reservoir levels and engineered drainage were investigated to determine the impact on dam stability. The airblast simulations created craters on the downstream slope and reduced the toe length. While larger explosive masses removed more material, crater dimensions did not significantly increase with explosive mass due to energy loss in air. Circular slip surfaces intersected the crater and reduced stability for dams with no engineered drainage. A horizontal toe drain effectively lowered the phreatic surface away from the blast crater and increased structural stability. Failure (as defined by a factor of safety less than unity) was induced in dams with no engineered drainage at reservoir levels of 80 percent reservoir capacity or greater. Dams with lower reservoir levels did not experience failure from an explosive airblast event. In addition, failure could not be induced in dams with engineered drainage. It was concluded that explosive airblasts posed a possibility of slope failure only for dams with no engineered drainage that were close to full reservoir capacity