During pile installation, construction disturbances alter soil mechanical properties near the pile, significantly affecting the dynamic response of the pile. This paper develops a three-dimensional (3D) analytical model to investigate the vertical dynamic response (VDR) of a pile in radially inhomogeneous saturated soil. Firstly, by employing the separation variable method and incorporating the continuity and boundary conditions of the soilpile system, the exact solution of the whole system in the frequency domain was derived. Subsequently, the timedomain velocity response under semi-sinusoidal vertical excitation is obtained using Fourier inverse transform and the convolution theorem. The accuracy and superiority of the proposed solution were validated through comparison with previous analytical solutions. Finally, the developed solution is then used to examine the impact of parameters of saturated soil and pile on the VDR of a pile. The results demonstrate that the proposed saturated model better captures the VDR of a pile in radially inhomogeneous saturated soil compared to the single-phase model. The VDR of a pile is significantly influenced by the pore water, porosity, disturbed degree and range of the saturated soil, as well as the elastic modulus of the pile.

Large-diameter pipe piles are widely applied in various civil engineering fields due to their outstanding load- bearing capability. The unsaturated characteristics, anisotropy, and heterogeneity of the soil jointly affect the dynamic response of the pipe pile. However, most previous studies were limited to single-phase or two-phase soil. This paper develops an analytical model for the torsional vibration of a pipe pile in transversely isotropic unsaturated soils considering construction disturbance. Based on transversely isotropic unsaturated soil theory, a pipe pile-soil interaction model has been developed, while the effect of construction disturbance is simulated by the radial heterogeneity of the soil. The general solution for the unsaturated soil is obtained using the separation of variables method with the boundary conditions. Then, the solution for the whole pipe pile-soil system is derived by considering the pile-soil interface conditions. The accuracy of the proposed solution is verified through comparisons with previous research results. The results show that unsaturated characteristics, construction disturbance, and transverse isotropy of the soil have significant effects on the impedance of large- diameter pipe piles. Specifically, with a low degree of saturation, there will be significant prediction errors when using previous works based on single-phase or two-phase soil theory to predict the dynamic response of large-diameter pipe piles.

Too little support force at the palm surface during shield excavation can lead to destabilization of soil before the excavation face and cause ground subsidence. Construction disturbances during excavation can affect the mechanical properties of the surrounding soil, which cannot be ignored when determining the needed support force at an excavation face. Based on the Mohr - Coulomb yield criterion, the collapse of dense sandy soils before the excavation face of shallowly buried shield tunnels is simulated using PLAXIS 3D to determine the collapse mode. Furthermore, the prismatic body in the traditional 3D wedge model is modified to an inverted elliptical-truncated cone with a certain inclination so that the collapse zone is closer to real sliding soils, and the disturbance ratio r is introduced as an index to consider a construction disturbance. The expression of the active limit support force with respect to wedge inclination is derived, and the maximum support force is determined by trial and error to be the minimum support force needed. The results of the modified 3D curved model are in good agreement with the numerical simulation results, as well as the results of theoretical methods and model tests.

Relying on the Mawan undersea large-diameter, dual-line, mud-water-balanced shield tunnel project and focusing on the characteristics of the tunnel, such as the complex geological conditions at the expected inter location and the existence of a superimposed perturbation or secondary perturbation effect, theoretical calculations and three-dimensional numerical simulations were used to reveal the ground disturbance situation of the large-diameter, two-lane mud-water shield when it is propelled under various working conditions. The working conditions were set for the dynamic inter of the left and right lines, with stopping and moving as the two modes, and a traversing simulation was carried out under three conditions related to the strata. The results show that the surface settlement curve for the two-lane construction became a W-shaped bimodal curve due to the superposition effect; the dynamic inter construction greatly disturbed the ground layer and there was a plastic zone expanding outward at a small angle above the tunnel, with shear damage in the soil layer and tensile damage in the rock layer. A one line stops, and another advances inter can reduce the impact of disturbance; the surface settlement value after the completion of the advancement was smaller than the dual-line intersection. The surrounding rock stress and displacement under the advancement of a single shield machine did not change to a great degree, there was no obvious change in the surface settlement above the tunnel, and the effect of the secondary disturbance was small.