Masters Thesis

Seismic Ground Improvement of Soft Soil Sites with Compacted Soil-cement Panels and Deep Soil Mixing Panels.

Based on previous studies, ground reinforcement methods such as stone columns, jet grouting, dynamic compaction, soil cement mixing, etc. are commonly used against potential liquefaction, settlement and to improve the bearing capacity of soil. However, additional benefits of ground improvement such as the possible reduction in seismic ground shaking are not usually considered in the practice or in the current International Building Code (IBC). As seismic damage is a major concern, soil-cement mixing was found to be the most effective in reducing of ground shaking levels. Among soil-cement mixing, compacted soil-cement panels have been considered as one among the most effective improvement techniques for seismic remediation. Past research shows that replacement of a portion of soil up to certain depth using compacted soil-cement mixture works effectively in improving soft clays and loose dry sand. However, field compaction effort requires some preparation and additional cost. The present study compares the results obtained through deep soil mixing panels with the results obtained with compacted clay based soil-cement panel. The compacted soil-cement panels and deep soil mixing panels corresponding to replacement ratios of 10% and 20% 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 compacted soil-cement panels are more effective in reducing seismic amplification than deep soil mixing panels. The compacted soil cement panels could reduce the seismic amplification by 12% and 25%, whereas the reduction for deep soil mixing panels was 9% and 15% for the replacement ratios of 10% and 20%, respectively.

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