Centrifuge modeling on effectiveness of liquefaction mitigation measures for clayey sand ground under large dams

Seismic loading has been widely recognized as a critical factor contributing to soil liquefaction. This paper introduces centrifuge tests conducted to characterize the seismic response of clayey sand foundations under surcharge induced by upper structures such as dams, with a focus on examining the effectiveness of different liquefaction mitigation measures. Three models with a surcharged block above are considered: one with soil untreated, one improved with stone columns, and the other enhanced by closed diaphragm walls. In addition, a free ground model is tested to examine the dynamic characteristics of the tested soil. Results show that the soil used is prone to liquefaction, but this trend can be somewhat suppressed by the presence of the surcharge. However, the excess pore pressure within the shallow layer keeps rising after shaking, posing the surcharged structure to instability. With the inclusion of stone columns, seepage can be effectively facilitated, thus eliminate the large pore pressure concentration. The construction of closed diaphragm walls effectively reduces the surface settlement by providing lateral restraint of the soil core. This investigation sheds light on the liquefaction mitigation mechanisms of different measures for clayey sand subjected to large overburden and provides references for improving the seismic design.