Comparative Analysis of Pile-Soil Stress Ratio Calculation Methods for Composite Foundation Based on Lateral Resistance Distribution Assumptions

The pile-soil stress ratio is a critical parameter for the bearing capacity and settlement calculations of rigid pile composite foundations and holds significant engineering importance in their optimization design. Current models are predominantly semi-empirical and semi-theoretical calculation models established on specific theoretical assumptions. The high sensitivity of input parameters and the reliance on limited experimental data for some models significantly reduce the universality and reliability of these computational models. This study summarizes the factors of influencing the pile-soil stress ratio and analyzes the load transfer characteristics of composite foundation. The final result shows that the distribution form of the pile shaft resistance is the main influencing factor of the pile-soil stress ratio. The existing pile-soil stress ratio calculation models are classified and summarized according to the different forms of pile shaft resistance distribution. The predictive performance of these models is compared and analyzed using specific engineering case studies. Comparative results show that the softened shaft resistance distribution model reflecting the ultimate pile shaft resistance can reasonably predict the pile-soil stress ratio at the bearing capacity eigenvalue with an error range of 10%～20%. The location of the neutral surface and the combined force of positive and negative pile shaft resistances are the main factors affecting the pile-soil stress ratio in rigid pile composite foundations. However, the specific form of the pile shaft resistances distribution curve has a limited effect on the predicted results. Based on the engineering parameters, different pile-soil stress ratio calculation models can be selected according to the variation trend of pile shaft resistance distribution during the loading process.