In recent years, prestressed pipe piles have been widely used in the reinforcement of soft soil foundation, and there will be obvious soil squeezing effect in the construction of pipe piles. However, the research on the soil squeezing effect of pipe piles under various influencing factors is not clear, and it is difficult to guide the actual construction on site. In this paper, the evolution mechanism of soil squeezing effect, pile-soil deformation characteristics and bearing characteristics in the process of pile sinking are analyzed in depth by means of field monitoring and laboratory test. Combined with visual model test, the distribution law of soil displacement field is clarified, and the effects of various influencing factors such as changing pile spacing and pile sinking sequence are revealed. The results show that the soil deformation caused by pile sinking increases first and then decreases in depth, and the soil deformation decreases exponentially in the horizontal direction. The width of the shear strain zone does not change with the increase of penetration, that is, the influence of the squeezing effect on the adjacent pile is mainly rotation and translation. For double piles, the expansion trend of the inner side of the two piles is smaller than that of the outer side of the pile. The squeezing effect will cause the adjacent pile to move and rotate. When the subsequent pile penetration is completed, the displacement field is no longer a basically symmetrical state, and the influence range in the depth area increases. When the pile spacing is set to more than 4 times the pile diameter, the synergistic bearing capacity of the pile group can be better played; The construction sequence from near to far is preferentially selected during construction, which can effectively reduce the impact on adjacent structures. The research results of this paper can provide a reference for further solving the disposal problem of composite foundation reinforced by pipe pile group.

In order to study the squeezing effect of static press large-diameter single pile and piles group in layered soil, field tests of static press large-diameter pipe piles were carried out based on a project under construction, and numerical simulations of the squeezing effect of single piles and piles group were conducted using finite element software. It is shown that during the process of pile penetration, the pore water pressure in the soil surrounding the pile rapidly increases to a higher initial value. Subsequently, the excess pore pressure will rapidly dissipate and gradually stabilize. The simulated and measured values of pile top displacement show a pattern of larger displacement at the pile top when the pile is first penetrated, and smaller displacement at the pile top when the pile is penetrated later. The measured horizontal displacement of the soil layer at each observation point of the group of 7 piles showed a turning point at a depth of about 2.5 m and fluctuated with increasing depth. The measured displacement reached its maximum value between 25 and 30 m and then rapidly decreased. The finite element simulation results of squeezing effect of the group of 20 piles show that the squeezing effect around the pile is very obvious within the depth range of the pile length. The horizontal displacement of the soil below the pile length rapidly decreases, and the maximum horizontal displacement of the soil at different depths around the pile mainly occurs at the surface. In addition, the reasons for the errors between the finite element simulation values and the measured values were analyzed.

Pre-tensioned H-type prestressed concrete revetment piles are a newly developed product dedicated to the protection of river, lake, and sea bank embankments, and their cross- is H-shaped. In this study, a field test of H-type pile soil's squeezing effect is carried out based on the second phase project of the HujiaShen Line. Pore water pressure, soil displacement, and other parameters of the H-type pile-driving process are monitored in real time. The test results show the following: (1) The influence range of the excess pore water pressure caused by the soil squeezing effect in the horizontal direction is about 14-15D, and in the vertical direction, the pore water pressure within a depth range of about 7D below the pile bottom increases rapidly. Its dissipation rate is fast at first and then slows down, and it completely dissipates 20 days after piling. (2) The excess pore water pressure caused by the soil squeezing effect does not decrease linearly in the radial direction. The soil around the construction pile can be divided into four areas: A, B, C, and D. Among them, A and B belong to the plastic zone, and C and D belong to the elastic zone. (3) The horizontal displacement of the soil occurs within the depth range of 5D from the surface of the pile to the bottom of the pile at the piling location, and the radial influence range is about 8-12D. From a vertical perspective, the main horizontal displacement of the soil occurs in the long of the pile driven into the soil, showing a U-shaped distribution. (4) The dividing point between the vertical displacement uplift and the settlement of the soil appears within the range of 2-3 m from the construction pile, that is, between 5 and 7D. Settlement occurs after the piling is completed, and the settlement rate is fast at first and then slows down. The final settlement of the soil is stable on the 20th day. This research and experiment provide a design reference for the engineering application of pre-tensioned H-type prestressed concrete bank protection piles.

The complex mechanical behaviours of steeply inclined and layered surrounding rock in strong and active fault zones result in control measures that cannot adapt to asymmetric squeezing tunnel and are still unsolved. Hence, the Yuntunbao Tunnel was taken as an example to study this issue based on geological survey and indoor and outdoor tests. The results showed that strong geological structures and abundant groundwater undoubtedly deteriorate the mechanical properties of rocks containing many water-sensitive minerals, approximately 45%. The stepwise growth of deformation characteristics before reaching the rock peak strength and the gradient to abrupt failure characteristics after reaching the rock peak strength are determined via triaxial cyclic and static load tests. According to field test results, the unilateral squeezing deformation is severe and greater than 1.5 m, the average extent of the excavation loosening zone is approximately 10 m, and the highest deformation rate reaches 12 cm/d. The gradual and sudden changes in tunnel deformation are demonstrated to be consistent with the postpeak deformation characteristics of layered rock in indoor tests. Moreover, the steel arch exhibits composite failure characteristics of bending and torsion. Finally, reliable and practical controlling measures are suggested, including the optimised three-bench excavation method with reserved core soil, advanced parallel pilot tunnel, long and short rock bolts, and large lock-foot anchor pipe. Compared with tunnel deformation before taking measures, the maximum convergence deformation is reduced from 2.7 to 0.9 m, and the bearing force of the primary support is also reasonable and stable.