Aquaterra provides geotechnical services tailored to each of our client’s specialized needs, identifying potential problems which could result in costly change orders and potential redesign work after the construction phase of a project has been initiated. By identifying potential pitfalls at the onset, such as shallow groundwater or unsuitable soils, our clients can realize overall cost savings by modifying the planned foundation design or selecting the appropriate soil amendments prior to initiating the construction phase of a project.
Aquaterra completed the stability and seismic analysis of an operating municipal sanitary waste landfill located near the New Madrid Fault in Southeast Missouri. Because the site is located within a seismic impact zone as defined by current federal and state regulations, a detailed seismic slope stability analysis was completed according to Missouri’s stringent standards. The project was particularly challenging because of the site’s underlying sands and gravels. Based on seismic hazard maps published by the USGS, the peak horizontal bedrock acceleration for the site was estimated to be 1.05g for a 2 percent probability of exceedance in 50 years, which approximates a magnitude 8.0 earthquake event.
The Aquaterra team used synthetic time histories and Stochastic Model Simulation (SMSIM) to generate time histories which approximated the ground motion expected at the site. These time histories were input into the software DEEPSOIL to perform a one-dimensional site response analysis and propagate the earthquake motion through 600 feet of sand, gravel, and clay layers above the bedrock to the ground surface. This earthquake acceleration was input into the slope stability software XSTABL to determine the resulting factor of safety for several landfill design scenarios. To support this analysis, Aquaterra installed ten (10) piezometers and advanced eleven (11) exploratory borings and four cone penetration soundings to collect in situ data for shear wave velocity, settlement, bearing capacity, seismic site response, and soil liquefaction potential.
