Beaver Heights Slope Stability Evaluation, Prince George’s County, MD

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GTA was retained as an expert witness to evaluate the alleged slope movement which impacted an existing WMATA railroad track and bridge abutment. This evaluation included subsurface explorations, installation and monitoring of instrumentation, and slope stability analyses to evaluate the apparent movement of a steep fill slope over native marine clays. The explorations included up to 100-foot deep Standard Penetration Test (SPT) borings by hollow-stem auger and mud-rotary methods, including undisturbed (Shelby Tube) samples. Laboratory testing, including Direct Shear and Torsional Shear tests, was performed to evaluate peak and residual shear strength parameters of the native, overconsolidated clays, along with other soil parameters. Instrumentation included inclinometers to evaluate the lateral movement of the slopes and groundwater monitoring wells to assess the levels and variability of the groundwater. Slope stability analyses were performed to evaluate the factors-of-safety against global slope failure and to assess the likelihood that slope movement resulted in damage to structures near the toe of the slope. GTA also provided recommendations for increasing the stability of the existing slope by regrading and incorporating drains to lower the groundwater elevations.