Axial Capacity of Drilled Shafts in Clay over Gravel Formation

This paper presents six case histories of load tests on reverse circulation method installed drilled shafts, with or without tip grouting, under axial load. Shaft displacement readings based on both telltale/extensometer and rebar strain gage are presented first. Subsequently, effect of loading cycle on shaft elastic modulus estimation is evaluated. The load versus displacement relationships at the shaft head, the t-z curves of the clay layer and of the gravel layer and the tip resistance versus displacement relationships are other important concerns and are compared in this paper. In addition, revised adhesion factor α and the parameter β based on the pile load test results are proposed in the paper.