Reduction in seismic shaking intensity on soft soils sites using soil-cement panels as stiff ground reinforcement

Soft clay deposits have been found all over the world. These soils are highly compressive and they create serious problems such as low bearing support, settlement, and earthquake induced deformations. Among all these, seismic damage is a major concern. Different ground reinforcement techniques such as stone columns, jet grouting and soil mixing are being used for the seismic mitigation of such sites. However, soil mixing is found to be the most effective as it has additional benefits such as reduction of ground shaking levels. This could result in reduced seismic loads on superstructure and lesser design requirements, thus leading to economized construction. The present study involves the use of stiff soil-cement mix panels in reducing the seismic shaking intensity of soft clay sites. Unconfined compressive strength tests were performed on unmodified soil as well as soil modified with cement and cured for 0, 7 and 14 days. The soil cement mix with the strength in the desired range, stiffness and most effective curing period was selected to be used as stiff panel reinforcement. Two different compacted soil-cement panels corresponding to replacement ratios of 16% and 30% were prepared and cured for 14 days. A series of small-scale shake table tests were performed using models with unimproved and improved soil with reinforcement panels at different seismic shaking levels. The research results show that the ground acceleration could be reduced by 27% and 46% by installing panels at area replacement ratios of 16% and 30%, respectively.