Stress-based velocity correction for evaluating the shear-wave velocity of the earth core of a rockfill dam

Abstract

Shear-wave velocity of an earth core of a rockfill dam is an important input parameter for earthquake site response. The shear-wave velocity should be measured in situ by a non-destructive method. However, this is inherently challenging due to the dam's overall geometry and the geometry of the earth core itself, which is tall, slender, and sandwiched between upstream and downstream rockfill shells. A surface-wave method like the Spectral-Analysis-of-Surface-Waves (SASW) or the Multichannel Analysis of Surface Waves (MASW) method can be considered a possible choice as the non-destructive method, however these methods have been shown to overestimate the velocities at depth (~10–20 m), depending on the width of the dam's crest. This paper proposes an empirical procedure to evaluate the shear-wave velocity profile of an earth core rockfill dam (ECRD). The resulting empirical equations based on the mean effective stress in the earth core were validated by comparing surface-wave tests conducted at rockfill dams with an earth core, alongside other borehole seismic tests. The resulting procedure was applied to six ECRD's located in Korea to demonstrate its feasibility and application.