Abstract: The retaining pile plus internal support structure has been widely used in foundation pit support engineering. Due to the complexity of geological condition, surrounding environment and earth excavation, however, it brings obstacles to the accurate design and calculation of foundation pit support system. This paper discusses the design and calculation method of single-layer internal support system under asymmetric load. Firstly, the difference of fixed point adjustment coefficient under articulated and fixed conditions between single-layer internal support and retaining pile is analyzed based on ultimate earth pressure method. Secondly, by using finite rod element method, the differences of pile shaft displacement, pile bending moment and pile shear estimated by two methods, i.e., earth pressure considering displacement by Terzaghi, and active earth pressure based on Chinese technical regulations for the support of building foundation pits. Due to the asymmetric load acting on the foundation pit support system, the displacement of the support piles on the side bearing large load and the side bearing small load are different, resulting in the different earth pressure on the support piles on the side bearing large load and the side bearing small load. The phenomenon of large difference in the internal force of the support pile shaft on the large and small sides should be paid attention to. The calculation methods of fixed point adjustment coefficient and displacement earth pressure proposed in this paper are more reasonable.

Key words: asymmetric load, opposite bracing, fixed point adjustment coefficient, limit earth pressure, earth pressure considering displacement, finite rod element method