The soil arching effect induced by shield tunnelling under asymmetric surface loading

It is common nowadays that tunnels are constructed at places where asymmetric topography or building exist, but insufficient attention has been paid to the influence of asymmetric surface loading (ASL) on the soil arching effect, which is vital for the design of tunnel structures. To remedy this research gap, a discrete element method (DEM) with a Rolling Resistance Linear model was employed to investigate the asymmetric soil arching (ASA) under the ASL. Based on the numerical analyses, an improved analytical model was proposed to calculate the stress on the tunnel under the ASL. The results reveal that: (1) The DEM adopted with a new algorithm can effectively simulate the progressive tunnelling and the evolution of soil arching. (2) The soil arch on the ASL side of the tunnel is further mobilized, and the major principal stresses rotate toward the ASL side. The asymmetric stress transfer trajectory significantly reduces the additional stress produced by the ASL. (3) Closer and larger ASL will result in larger and more asymmetric stress, but the further development of ASA could alleviate it. (4) The effectiveness of the proposed analytical method considering the ASA effect is validated via comparisons with numerical computation and other analytical methods.