Centrifuge model tests on liquefaction mitigation effect of soil-cement grids under large earthquake loadings.

In this study, the seismic response and liquefaction mitigation effect of the soil-cement grid improved ground subjected to large earthquake loadings are studied through dynamic centrifuge tests. The model tests included soil-cement grid improved and unimproved model grounds, both of which have a 15-m-thick liquefiable layer underlain by a 2.5-m-thick coarse sand layer. The pre-cast soil-cement grid adopted in this study enables the dynamic responses of the model closer to the real improved ground. The recorded responses of accelerations, excess pore pressures and the deformation of the enclosed soil in the improved ground were carefully analysed with the comparison of the ground without improvement. It shows that the soil liquefaction and post-shaking settlements were effectively mitigated by the soil-cement grid even under very strong shakings. And the restriction effect of the soil-cement grid on dynamic shear strain of the enclosed soil was the most prominent in the middle height, regardless of the intensities of the shaking events. Such mitigating "waist effect" could mainly be attributed to the dynamic soil-grid interaction during shaking. However, the underlain soil layer may experience larger shear strain due to the increasing inertial force of the overlying ground improved by the soil-cement grid. [ABSTRACT FROM AUTHOR]