Centrifuge Testing of Remediation of Liquefaction at Bridge Sites

Five centrifuge models were tested to begin to quantify the effectiveness of liquefaction remediation techniques and to optimize the required volume of soil to be treated to reduce liquefaction consequences to a tolerable level. Detailed models of a bridge site including a river channel, flood plains, and bridge abutments were tested in the large centrifuge at the University of California, Davis. The models consisted of a deep, level, liquefiable sand layer overlain by a sloping, less-permeable clay layer with a free face at the river channel. Densification of a limited region of sand and in-ground water barriers were evaluated as possible remediation treatments. While spinning at a centrifugal acceleration of 30 g, the base of each model was shaken with realistic earthquake base motions. Base motions, pore pressures in the treated and untreated zones, profiles of ground deformations, settlements, and lateral sliding are compared. Settlements were controlled satisfactorily, but lateral sliding of the surface clay layer was not adequately controlled by the limited remedial treatments.