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Slurry diffusion is the key factor affecting the resistance reduction of pipe jacking grouting. Therefore, this paper establishes a three-dimensional numerical analysis model of pipe jacking, introduces a diffusion ring to simulate the slurry diffusion process during pipe jacking construction, modifies the friction coefficient according to the contact between the soil around the pipe and the segment, and studies the influence of the slurry diffusion process on the resistance reduction effect during pipe jacking construction. The calculated jacking friction is compared with the measured data to verify the reliability of the method proposed. The influence of the filtering effect on soil displacement and the influence of grouting diffusion-related parameters on soil displacement and jacking friction during pipe jacking construction are further studied. The results show that the surface subsidence is smaller when the filtration effect is considered; The stronger the attenuation of permeability coefficient caused by the filtration effect, the smaller the surface settlement and jacking friction resistance; The faster the slurry diffuses and the more complete the slurry jacket is, the better the resistance reduction effect of grouting during pipe jacking.

When pumping in confined aquifers, vertical leakage could be found in the multi-aquifer system in soft deposits, and the responses of groundwater flow and strata deformation are complicated. Based on pumping tests in an ultra-deep underground project, this study performs a 3D finite-difference modeling to investigate the responses of groundwater and strata to pumping in the second and third confined aquifers. It considers the hydro-mechanical coupled and small strain stiffness characteristics of soils in the analysis, and discusses and compares the spatiotemporal distribution characteristics of drawdown and deformation induced by pumping in different confined aquifers. The results indicate that the ground settlement induced by pumping in the second confined aquifer is greater though the groundwater drawdown is smaller, and the compression of dewatering aquifers caused by dewatering in the second and third aquifers accounts for 56.18% and 77.69% of the settlement, respectively. It could be attributed to the connectivity between the second confined aquifer and its overlying aquitards, which results in a greater influential depth. In addition, the compressibility of shallow strata is significantly greater than that of deep strata. The study is significant for the dewatering construction and environmental deformation control of ultra-deep excavations.

An adjacent excavation model based on the hardening soil-small strain (HSS) constitutive model was established by using the numerical method, which was compared with the single excavation model and the adjacent excavation model without considering the wall-soil friction. The stress deformation characteristics of adjacent excavation implemented simultaneously were obtained, and the interaction mechanism of adjacent excavations were revealed. The results show that two kinds of arching effects exist in the confined soil. One is the arching effect caused by uneven deformation of walls, and the other is the arching effect caused by the wall-soil friction, both of which affect the lateral earth pressure acting on the retaining walls. With the decrease of the excavation spacing, the former is weakened, resulting in the weakening of the transfer of lateral earth pressure between the soil near the excavation face to bracing soil, while the latter is enhanced, leading to the decrease of magnitude of the lateral earth pressure acting on adjacent retaining walls. Under the action of the arching effects, the curve of lateral earth pressure develops from an R-shaped distribution to a linear distribution and then returns to an R-shaped distribution with the decrease of the spacing. The maximum horizontal displacement of non-adjacent walls increases, and the maximum horizontal displacement of adjacent walls increases primarily and then decreases.

The pile foundation of offshore wind turbines is not only subjected to the cyclic action of wave load, but also the threat of seismic load. Therefore, the environment of pile in the ocean is complex. However, most theoretical investigations have often focused on the seabed response at water wave load or seismic load respectively. In this paper, a wave-seismic-pile-seabed coupling model is constructed by using the finite element method. The numerical analysis is based on the implicit dynamic analysis in Abaqus. Morison’s equations are used to simulate the effect of water wave on pile foundation. The Mohr-Coulomb model is adopted to simulate the seabed while the pile is considered as an elastic medium. The earthquake is applied on the bottom of the model as acceleration. The dynamic response of the pile embedded in seabed are studied, such as acceleration, displacement, shear force, and bending moment. The results show that seismic load has an important influence on the single pile foundation of offshore wind turbine. Under the action of earthquake load, the acceleration and displacement response of the pile are amplified to a certain extent. The properties of the soil and the parameters of the pile are crucial to the design of the single pile foundation for offshore wind turbines.

It is generally difficult to consider the fluid dynamic boundary problem in the traditional particle-fluid coupling algorithm, causing calculation errors owing to the mismatching of the fluid-solid boundary and affecting the accuracy of the results in the modeling of large deformation issues. In view of this problem, the dynamic updating method of fluid mesh is introduced and Darcy’s seepage equation and the particle-fluid interaction equation in dynamic mesh are derived. Based on the discrete element commercial software PFC2D, the particle-fluid coupling algorithm considering dynamic fluid mesh is developed. The proposed algorithm is applied to simulate the undrained shear biaxial test of saturated soil. The comparison result with the constant volume method verifies the effectiveness of the developed algorithm. Finally, the algorithm is used to simulate the undrained biaxial tests at different confining pressures. The law of the calculated results agrees well with that of the laboratory tests. By considering the problem of fluid dynamic boundary, the developed algorithm can obtain the fluid-solid boundary matching in the simulation of triaxial compression test and one-dimensional consolidation test or other cases in large deformations, which can help to improve the simulation accuracy and offer a theoretical reference for similar studies.