Assessing the coefficient of the earth pressure at rest from shear wave velocity and electrical resistivity measurements

Determination of earth pressure coefficient K-0 in natural soil deposits is a significantly important issue in geo-technical engineering. This paper evaluates the feasibility of predicting K-0 values from measurements of vertical and horizontal shear wave velocities [V-s(VH), V-s(HH), and V-s(HV)], and vertical and horizontal electrical resistivities (S-V, S-H). A series of seismic piezocone tests (SCPTU), improved crosshole (CH) tests, and soil resistivity tests using a modified laboratory apparatus were carried out at two research sites in Jiangsu Province of China and results were used to develop two existing K-0-shear wave velocity correlations for prediction of K-0. The seismic and electrical resistivity test results showed that both the shear wave velocity ratios, V-s(HH)/V-s(HV) or V-s(HV)/V-s(VH), and the horizontal to vertical electrical resistivity ratio, S-H/S-V, may provide a good indicator of the inherent soil anisotropy at these sites. The existing V-s-K-0 prediction framework largely requires determining C-s(HV)/C-s(HH) ratio and a simple procedure for evaluating this ratio based on the measured horizontal and vertical electrical resistivities. The K-0 values predicted by shear wave velocity at both sites are also compared with values determined by Jaky's formula and Mayne & Kulhwy's formula. In normally consolidated (NC) soils, the K-0 values predicted from these methods showed good agreement. However, for over-consolidated (OC) soils at shallow depths, certain variations between different methods are noted. Further investigations of the effects of overconsolidation ratio on K-0 predictions will lead to the correction factors for better prediction of K-0 for DC soils. This paper has confirmed that reasonable predictions of K-0 for natural soil deposits can be made using the proposed methodology. (C) 2013 Elsevier B.V. All rights reserved.