Finite element analysis of effect of soil displacement on bearing capacity of single friction pile

Abstract

Effect of soil displacement on friction single pile in the cases of tunneling, surcharge load and uniform soil movement was discussed in details with finite element method. Lateral displacement of the pile caused by soil displacement reached about 90% of the total displacement, which means that P-Δ effect of axial load can be neglected. The maximum moment of pile decreased from 159 kN·m to 133 kN·m in the case of surcharge load when the axial load increased from 0 to the ultimate load. When deformation of pile caused by soil displacement is large, axial load applied on pile-head plays the role of reducing the maximum bending moment in concrete pile to some extent. When pile is on one side of the tunnel, soil displacements around the pile are all alike, which means that the soil pressures around the pile do not decrease during tunneling. Therefore, Q-s curve of the pile affected by tunneling is very close to that of pile in static loading test. Bearing capacities of piles influenced by surcharge load and uniform soil movement are 2480 kN and 2630 kN, respectively, which are a little greater than that of the pile in static loading test (2400 kN). Soil pressures along pile increase due to surcharge load and uniform soil movement, and so do the shaft resistances along pile, as a result, when rebars in concrete piles are enough, bearing capacity of pile affected by soil displacement increases compared with that of pile in static loading test.