New Approach to Determine Composite Shear Wave Velocity of Improved Ground Sites

Abstract

This paper evaluates the current state of practice to determine the average shear wave velocity of improved ground sites and proposes an alternative method that adequately captures the reinforcement effects of ground improvement elements. To estimate the actual stiffness of improved grounds and to develop benchmark data, continuum finite-element models of improved grounds with various area replacement and stiffness ratios are analyzed. The study shows that the common approach, i.e., the area replacement ratio weighted average shear wave velocity, significantly overestimates the improved ground average velocity. This may lead to an incorrect determination of a code-based site class, spectral accelerations, and seismic structural loads. The proposed alternative approach is shown to be capable of providing a reasonable estimate of the actual stiffness of improved grounds.