Dynamic Centrifuge Tests of Soft Clay Reinforced by Soil

Dynamic Centrifuge Tests of Soft Clay Reinforced by Soil–Cement Grids

Khosravi, Mohammad

AbstractA pair of large centrifuge tests was conducted to evaluate the effect of soil-cement grid reinforcement on the seismic response of a deep soft soil profile. The soil profile consisted of a 23-m-thick layer of lightly overconsolidated clay, underlain and overlain by thin layers of dense sand. Each centrifuge model had two separate zones for a total of four different configurations: a zone without reinforcement, a zone with an embedded soil-cement grid that penetrated the lower dense sand layer and had a unit cell area replacement ratio of Ar=24%, a zone with an embedded grid with Ar=33%, and a zone with a floating grid in the upper half of the clay layer with Ar=33%. Models were subjected to 13 shaking events with peak base accelerations ranging from 0.005 to 0.31 g. This paper examines the effect of the soil-cement grids on the global responses of the soil profiles, and the internal interaction between soil-cement grids and their enclosed soils. Nonlinearities in the dynamic responses and interaction mechanisms are examined using (1) time series of accelerations, shaking-induced excess pore-water pressures, and postshaking reconsolidation settlements; (2) response spectra and spectral ratios; (3) back-calculated composite stress-strain responses; (4) analyses of internal stress distributions between the grids and enclosed soils; and (5) dynamic crack detections and posttest crack mapping in the soil-cement grids. The results provide insights on the dynamic performance of soil-cement grids and an archived dataset for evaluating design procedures and numerical analysis methods.