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In this paper, the pile-soil interaction of a low-rise pile cap foundation of an inclined straight alternating pile on two or three layers of a soil liquefaction site under seismic load is studied. By inputting the 0.5 g El Centro seismic wave in FLAC 3D , the pile-soil interaction rule of the pile foundation of the inclined and straight pile groups of the low-pile cap under seismic action is simulated. By analyzing the soil acceleration, the pore pressure ratio, the horizontal displacement of the pile body, the vertical displacement, and the pile body bending moment, the law of pile-soil interaction between the pile and soil when the lower part of the pile is embedded in the clay layer is studied, and the low-rise pile cap inclined straight alternating group pile foundation on the two-layer soil and the three-layer soil free field is compared and analyzed. e results show that, under seismic load, the maximum acceleration of soil mass in the two-layer soil and three-layer soil model is discrete, and the pore pressure ratio of sand soil increases from bottom to top. By analyzing the displacement and bending moment of pile body, the bending moment at the joint between the pile cap and the top of pile body is the largest and the most vulnerable to damage. e maximum value of pile displacement and bending moment in the three-layer soil is less than the maximum value of the two-layer soil, indicating that the pile group foundation in the three-layer soil free site model is safer.

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To study the force and deformation characteristics of subsea mudmat-pile hybrid foundations under different combined loads, a project at a water depth of 200 m in the South China Sea was studied. A numerical model of a subsea mudmatpile hybrid foundation is developed using the numerical simulation software FLAC3D. The settlement of the seabed soil, the bending moments of the mudmat, and the displacements and bending moments along the pile shaft under different load combinations, including vertical load and horizontal load, vertical load and bending moment, and horizontal load and bending moment load, are analyzed. The results indicate that settlement of the seabed soil is reduced by the presence of piles. The settlement of the mudmat is reduced by the presence of piles. Different degrees of inclination occur along the pile shaft. The angle of inclination of pile No. 1 is greater than that of pile No. 2. The dip directions of piles No. 1 and No. 2 are identical under the vertical load and bending moment and are opposite to those under the other combined loads. The piles that are located at the junctions between the mudmat and the tops of the piles are easily destroyed.

A subway, as a transportation facility for huge traffic, is prone to be the target of terrorist bombings while facilitating people in traffic significantly. Accordingly, to reduce the impact of security risk, this paper proposes a new composite steel plate lining structure to ensure subway anti-explosion protection in light of the advantages of high shear strength and tension resistance of a composite steel plate. In addition, by referring to the case of Nanjing (in China) subway project, this study established a numerical model for the anti-explosion protection impact of a composite steel plate lining structure in a subway tunnel through a dynamic analysis software LS-Dyna, and analysed the dynamic response of the lining structure of the numerical model with or without a composite steel plate under a 10 kg trinitrotoluene (TNT) and a 30 kg TNT of explosive equivalents. According to the results, the composite steel lining structure is able to effectively absorb shock waves in case of subway explosion, and the acceleration and velocity of the tunnel lining structure are reduced significantly, which can effectively prevent an explosion under a low explosive equivalent.