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.