Numerical analysis of influence of stiffness of pile tip soil on shaft resistance

Under the fixed compression modulus of pile shaft soil, the finite element method is employed to calculate and analyze the changes in the bearing behavior of single pile as well as the unit stress status and displacement changes of the soil around the pile under the circumstances of different soil compression modulus ratios of pile tip to pile shaft. A conclusion is drawn that different stiffnesses of pile tip soil may change the vertical additional stress in pile shaft soil. Under the same pile top displacement, the greater stiffness of pile tip soil is, the larger high-stress area of pile shaft soil above the pile tip is. With the increase of the stiffness of pile tip soil, the shaft resistance in a certain range of lower pile shaft will develop. So the stiffness of pile tip soil has an enhancing effect on the shaft resistance. Combined with the stress analysis of the soil unit around the pile tip, the influence mechanism can be summed that the pressure damage and protruding effect of the pile is enhanced by the increase of the stiffness of pile tip soil. At the same time, the constraint effect of pile tip soil on the displacement of pile shaft soil is improve, so the confining pressure in a certain area of pile tip soil is increased and the shear resistance is strengthened, and the shaft resistance is also increased.