Test and Numerical Simulation of Excavation of Subway Stations Using the Small Pipe–Roof–Beam Method

Abstract

The small pipe–roof–beam method has better adaptability to ultra-shallow buried subway stations. Five groups of similar model tests were carried out to explore the pipe–roof deformation, surface settlement, and beam strain caused by excavation using this method. Based on the test results, a 3D numerical model was established to study the pipe–roof deformation under different cases. The following conclusions were obtained: as the height-to-span ratio increases, the pipe–roof deformation, and surface settlement increase and, afterward, decrease. Increasing the number of beams can significantly reduce the pipe–roof deformation and surface settlement, and has a greater effect on the surface settlement. The soil-arching effect occurs above the pipe–roof during excavation, and is strengthened with an increase of height-to-span ratios. The difference between the pipe–roof deformation caused by excavation is within 2% in two cases: free at both ends and fixed at only one end. It is not recommended to add support to only one end in actual construction. Adding support at both ends can reduce the pipe–roof deformation by about 40%. The research conclusions have guiding significance for the development of the small pipe–roof–beam method.