Analysis on torque and pile-soil interaction of anti-flood screw pile during the installation process

Anti-flood screw pile has continuous blades, which is a new type of micropile applied in flood control. In this paper, based on the theory of spherical cavity expansion and the method of differential element division, a theoretical method was proposed to evaluate the installation torque of the micro screw pile in cohesion soil. Field tests of different screw piles were carried out, and different torque-displacement response curves were measured. The theoretical results are compared with the tests, and the accuracy and reliability are verified. And the verification method is applied to examine the effects of different parameters on the installation torque. The parameters include pile geometric characteristics and soil properties. Finally, a numerical model is built based on FEM-SPH method, and the test results are compared with the simulation to validate the model. The pile-soil interaction at micro-scale is investigated by studying soil particles movement and soil stress state during the installation process. The numerical analysis results show that the greater the torque required for installation, the greater the damage range of the soil. The damage range of soil during the installation process is consistent with the geometry of the pile, showing a tapered cylinder shape. During this process, the conical pile head shows great mechanical characteristics, a circular stress plastic deformation zone is formed near it, and the size of this area is related to the structural parameters of screw pile. This study further makes up for the deficiencies of theoretical analysis and experimental methods, and it will provide the reference for the study of this type of micro screw piles.