Method and Application of Determining Ultimate Bearing Capacity of Existing Piles Based on Catastrophe Theory and Specific Energy Comparison Method

In order to further excavate the vertical bearing capacity of existing pile, the load displacement curve equation of the test pile was derived by using the principle of the least square method according to the load displacement curve of the test pile and the bearing behavior of the foundation pile, and the extension of the load displacement curve was fitted. On this basis, in order to predict the vertical ultimate bearing capacity of the pile, the catastrophe point method and the specific energy comparison method were used. The specific energy of the pile-soil system was used as a catastrophe criterion. The load-displacement curve equation of the test pile was used to obtain the cusp catastrophe specific energy curve and the catastrophe point specific energy, and the average shear strength of the pile side soil layer was compared to determine the critical failure state of the pile and soil. The research shows that the curve of pile top deformation-graded loading value is formed through the specific energy function equation of pile foundation, and the catastrophe theory is used to deduce the vertical ultimate bearing capacity of pile. The physical meaning is clear, which can provide a theoretical basis for the prediction of the actual vertical ultimate bearing capacity of existing pile foundation and the determination of the maximum loading value of engineering test pile.