Bearing performance of diaphragm wall pile combination foundation under vertical and horizontal loads

With the development of foundation engineering, finding new types of foundations with higher bearing capacity and stability has become an important research direction. In this paper, a new type of combined foundation consisting of diaphragm walls and pile groups is proposed, taking advantage of the benefits of both diaphragm walls and pile foundations. Finite element software is used to establish combined foundation models with diaphragm walls ranging from 1 m to 4 m in height, and model tests are conducted to validate the reliability of the finite element results. Subsequently, the settlement, axial force, and distribution of the horizontal axial force of the combined foundations under vertical loading are investigated for four different height combinations. Compared to pile foundations, combined foundations can significantly improve the ultimate bearing capacity of the foundation. The axial forces in both the piles and diaphragm walls decrease abruptly at the connection between the two structures. The diaphragm walls can bear larger vertical loads, and a tensile force is generated in the 1 m high diaphragm wall between the pile groups, while compressive forces are generated at higher heights. Additionally, the horizontal bearing capacity of the combined foundation is examined by analyzing its horizontal displacement, bending moment of the piles and diaphragm walls, and horizontal axial force of the diaphragm walls. The horizontal bearing capacity of the combined foundation is 26% higher than that of the pile foundation. The 1 m high diaphragm wall provides constraint to the pile top, reducing the horizontal displacement. As the height of the diaphragm wall increases, the constraint effect weakens, and the horizontal bearing capacity at a height of 4 m mainly relies on the lower part of the pile body.