Seepage Analysis of Earthen Dams in South Carolina with Animal Burrows

The structural integrity of earthen dams in the natural habitat of wildlife is commonly affected by invasive animal burrowed into the embankment. The effects may be observed on the phreatic line, pore water pressures and seepage rate through the dam. This study investigates the effects of previously reported wildlife activities on two failed dams in the Midlands of South Carolina. Dam sites were visited to collect soil samples for geotechnical testing, measure the geometry, and make observations for animal presence. The dams are determined to have burrows by gophers and ant colonies from the inspection reports and site observations. To characterize the soils, geotechnical tests are conducted for grain size distribution, permeability, porosity, and liquid limit. The finite-element method is used to simulate the two-dimensional steady-state seepage at dams with isotropic and homogeneous soil assumption. A saturated/unsaturated soil model is used and Modified Kovacs and Mualem methods are utilized for the estimation of the volumetric water content function and hydraulic conductivity function, respectively. Pore water pressures, hydraulic gradients and seepage velocity are compared for intact and deteriorated structures to investigate the effects of animal activity. The results show that the animal burrows negatively impact the seepage behavior of the dams by affecting the pore water pressures, seepage rate, hydraulic gradients, and seepage velocities.