Seismic Site Characterization in Support of Drilled Shaft Design in Southern Nevada

摘要

In advance of conducting drilled-shaft load testing for a highway interchange in Las Vegas, Nevada, the site investigations have included borehole-based soil sampling and logging, standard penetration testing, and both surface-based and downhole seismic testing. Sediments in the area tend to be dense, deep, and sporadically carbonate-cemented. Locally measured velocities are significantly higher than global expectations for the same sediment types. The measured shear-wave velocity profiles fit local expectations in the dry zone (the upper 14 meters) and in the presence of secondary carbonate cementation. For wet, uncemented media, velocities are closer to global-reference velocities. Compression-wave velocities indicate depth to moist soil, which reaches well above the observed groundwater table. Correlation of shear-wave velocity to blow count is weak. The measurements will be compared with data from O-Cell™ (Osterberg Method) load tests of co-located drilled shafts, with the end goal of improving abilities to predict the capacity of drilled shafts in the Las Vegas area using site characteristics that are readily measured in situ.