Liquefaction analysis of three Pleistocene sand deposits that did not liquefy during the 1886 Charleston, South Carolina earthquake based on shear wave velocity and penetration resistance.

摘要

The results of geotechnical investigations at three sites located in the South Carolina Coastal Plain are presented in this thesis. The three sites are called the Hobcaw Barony Borrow Pit site located near Georgetown, SC; the Rest Area Ponds site near Walterboro, SC; and the Lowcountry Sand & Gravel site, also near Walterboro. Near-surface sand deposits at these sites ranged in geologic age from 200,000 to greater than 1,000,000 years. These three sites lie well outside the region of most liquefaction effects observed following the 1886 Charleston earthquake. Investigations conducted at the sites include seismic cone penetration tests with pore pressure measurements (SCPTu), dilatometer tests (DMT), standard penetration tests (SPT), seismic crosshole tests, and fixed piston sampling. Laboratory investigations on samples collected include grain size, Atterberg limit, and consolidation tests.;Sand layers most susceptible to liquefaction are identified at each site. For these critical sand layers, ratios of measured Vs to V s estimated (MEVR) using relationships proposed by Andrus et al. (2004a) are 1.28, 1.13, and 1.36 at the Borrow Pit, Rest Area Ponds, and Lowcountry Sand & Gravel sites, respectively. These MEVRs suggest geotechnical ages of 16,000, 240, and 152,000 years for each site, respectively, based on the MEVR-time relationship presented in Andrus et al. (2009).;The critical sand layers at each site are evaluated for liquefaction potential using shear wave velocity-based and penetration-based cyclic resistance ratio (CRR) curves adjusted for age/cementation. The results of the evaluation indicate low probability of liquefaction at the three sites during the 1886 Charleston earthquake. Based on the 2% probability of exceedance in 50 years earthquake scenario suggested by the 2008 USGS Hazard Map, moderate liquefaction is predicted for the Borrow Pit and Rest Area sites and marginal liquefaction is predicted at the Lowcountry Sand & Gravel site. Predictions based on shear wave velocity and penetration are in good general agreement with each other when age/cementation corrections are applied.