Settlement, sliding, and liquefaction remediation of layered soil

A series of highly instrumented, large-scale centrifuge models have been te sted to investigate the extent of remediation required to control settlemen t and lateral sliding of soil deposits at a hypothetical bridge site. The b aseline model represents a prototype with a 9-m-thick layer of fine sand ha ving a relative density (Dr) of 50%. The sand layer is overlain by clay flo odplains with a free face at a river channel. One nearly level floodplain s urface supports a bridge abutment. The other floodplain has a 9% slope towa rd the river. In different models, different amounts of the 50% relative de nsity sand was densified to Dr = 80%. Full depth improvement reduced settle ments and lateral sliding of the sand by about a factor of 3. Due to the ef fects at the clay-sand interface, lateral sliding of the surficial clay dep osit was not controlled by densification of the sand. Tests in which the wi dth of the densified zone was only about 75% of the thickness of the loose sand indicated that relatively narrow zones of improvement can control sett lement and sliding of the sand. Differences in shear resistance, pore press ures, dilatancy, and energy dissipation in loose and dense sands are presen ted.