Abstract: Underground structures are severely damaged when subjected to strike-slip faulting during an earthquake. Mechanism behind inconsistent dynamic responses in soil stratum is not yet fully understood. The influence of pre-existing fracture in soil stratum on the dynamic response of the soil is still not clear. Based on a newly designed laminar box with simulation of strike-slip fault, two dynamic centrifuge tests were conducted on clay stratum to investigate the influences of the pre-existing fracture. Centrifuge test results show that inconsistent dynamic responses for the soil crossing bedrock fault is not obvious when there is no pre-existing fracture. With a pre-existing fracture, however, the magnitude of seismic wave at the moving block decreases with time during shaking. Inconsistent dynamic responses between the stationary and moving blocks are then observed. In addition, the excess pore water pressures developed at the stationary block are larger than what are observed at the moving block. The effects of distribution of the pre-existing fracture on the inconsistent dynamic responses in the soil stratum are also demonstrated. It is of significant importance to identify the tip depth of the pre-existing fracture in soil stratum.

Key words: geotechnical centrifuge, shaking table test, strike-slip fault, preexisting fracture, dynamic response