Analytical study of the influence mechanism of cement-stabilized soil on the torsional dynamic bearing performance of single piles

As an effective technique for enhancing the bearing capacity of single piles, cement-stabilized soil has been widely applied in engineering practice. Analyzing the dynamic torsional response of the coupled single pile system is of considerable practical significance. Based on the elastodynamic theory and the plane-section assumption for stress wave propagation in rod members, and considering the nonlinear stiffness degradation behavior of cement-stabilized soil subjected to the circumferential shear strain induced by torsional vibration, this study investigates the vibration characteristics of the coupled single pile–cement-stabilized soil–surrounding soil system under dynamic torsional loading applied at the pile head via theoretical derivation and parametric analysis. First, the governing equations for torsional vibration of the surrounding soil, cement-stabilized soil, and single pile are established respectively through mechanical equilibrium analysis. The Hardin-Drnevich constitutive model is adopted to characterize the nonlinear stiffness degradation behavior of cement-stabilized soil. Subsequently, rigorous theoretical derivations are performed to derive the analytical solutions for pile shaft torsion angle and torque under the confinement of cement-stabilized soil. Finally, through case studies and parametric sensitivity analysis, the influence mechanisms of dynamic torsional load characteristics, physical parameters, and nonlinear properties of cement-stabilized soil, as well as geometric and mechanical parameters of single piles on pile torsional angle and torque ratio are discussed. The results show that cement-stabilized soil can significantly enhance the torsional resistance of single piles. When the nonlinear stiffness degradation of cement-stabilized soil is considered, remarkable amplification effects occur in the frequency-domain response amplitudes of both pile torsional angle and torque ratio. Specifically, when the elastic modulus ratio of cement-stabilized soil to intact soil equals 10, considering the nonlinear behavior increases the pile-top torsion angle by 8.2% and the pile-tip torque ratio by 14.9%. Such nonlinear amplification effect becomes more prominent with larger dynamic load amplitude, lower stiffness of cement-stabilized soil, and smaller reinforcement radius.