Mechanical response of pile group and stratum induced by shallow tunneling based on the model test

Abstract

Taking a shield tunnel in the Beijing subway system as the background, a three-dimensional model test study is conducted on shield tunneling adjacent to the pile group. In this scaled model test, the geometric similarity ratio is designed as C_L = 1/24. This test reveals the evolution patterns of surface displacement and characteristic deformation of piles during shield tunneling. Two conditions are designed to monitor tunneling adjacent to unilateral and bilateral pile groups. During the tunnel excavation process, surface settlements, pile group displacements, and strains of the pile are observed. The measured results elucidate the stratum deformation patterns observed throughout the shield tunneling process, as well as the deformation characteristics of the existing pile groups in both the circumferential and longitudinal directions. This study compares the effects of existing a pile group versus a greenfield area during tunneling adjacent to a unilateral pile group, taking into account the sheltering effect of the pile group. Finally, the differences in impact from varying pile lengths and pile-tunnel spacings on surface settlements are analyzed, along with the influence of pile length on the vertical and horizontal displacements of the pile group.