Effect of the degradation of concrete friction piles exposed to external sulfate attack on the pile bearing capacity

An analytical method is proposed in this paper to present the effect of the degradation development of concrete friction piles subjected to vertical loads on the pile bearing capacity. This paper proposes an analytical solution of the sulfate diffusion-reaction equation based on Fick's law and Danckwerts' method in polar coordinates. A chemo-mechanics model is established to compute expansion based on the consideration of the pore filling. Furthermore, the effect of concrete expansion on pile-lateral-soil effective stress is analyzed. A model is based on a hyperbolic nonlinear relationship to simulate the behavior between the skin friction and the pile degradation along the pile-soil interface. Additionally, the sulfate distribution over time, the changes of crack point along a pile radius and the skin friction are analyzed. Finally, a parametric study with different external sulfate concentration, the microcracks and different soil properties is performed. The results show that the crack point moves into a pile due to external sulfate attack, accelerating the invasion of sulfate. The effective radius and the elastic modulus of a pile tend to decrease. The degradation of concrete friction piles lead to loss of friction, resulting in the bearing capacity of the pile decline. The effect of different soil properties the on pile bearing capacity is different.