Nonlinear Pile Stiffness Analysis from an O-Cell Test of a Pile on Maputo Bridge

Abstract

Maputo Bridge will be built between KaTembe and Maputo, Mozambique. To determine the ultimate bearing capacity of pile and friction resistance of different soil layers, a pile is conducted in the field by the method of o-cell test. The length of the pile is 55m, diameter 1.50m. The load cell is placed at 5 meter above the bottom of the pile. The bearing layer is clay siltstone. Strain gages are embedded at the different positions of the test pile to obtain the axial force of different cross section position. According to the field test, it results in an impossibly large computed load by assuming a constant pile stiffness. The pile axial forces of different load grades will confront with reasonable discipline in terms of nonlinear stiffness. The pile stiffness changes with different load grades, and that stiffness is a function of strain. When reaching a certain load level, the pile stiffness changes little and could be regarded as constant. Then the o-cell test result is converted to conventional pile head load-displacement. It shows that the pile ultimate bearing capacity of o-cell test is satisfied with design requirements, and the proposed nonlinear stiffness is reasonable in reality.