Experimental Study of the Influence of Surface Surcharge on Tunnel Lateral Deformation in Soft and Hard Soil

Abstract:

The influence mechanism of surface surcharge position on tunnel lateral deformation in soft and hard soil is studied by using the scale model test. Considering different surcharge position and tunnel traversing soil layer properties， the changes of ellipticity， the joint opening， and the additional earth pressure of tunnel segment during the graded loading-unloading process are measured. The test results show that when the load is the same， the tunnel ellipticity decreases rapidly first and then tends to smoothen with the increase of eccentricity of surcharge， the ellipticity of the tunnel in soft soil layer is larger than that of the tunnel in hard soil layer due to loading， and the decrease of tunnel ellipticity in soft soil layer is more obvious with the increase of eccentricity. Increasing the eccentricity of surcharge can effectively reduce the opening of the tunnel joint. The deformation mainly occurs in the left and right shoulder and the top joint of the tunnel when the load is directly above， and mainly in the shoulder and the top joint on the opposite side of the load during eccentric loading. Under the action of surcharge， the earth pressure of the tunnel in the sandy soil layer is uniformly distributed， while that in the soft soil layer is mainly concentrated in the horizontal direction. With the increase of eccentricity， the earth pressure decreases gradually and the main concentrated point shifts to the oblique section of the opposite side of the load. Finally， based on the results of finite element parameter analysis， the protection suggestions on the surface surcharge in the operating tunnel are proposed.