Experimental Study on Lining Cracking of Shallow Buried Loess Tunnel under the Simulation of Effect of Slide Surface Immersion

Yuyang Liu,Hongpeng Lai

doi:10.3390/app10176080

Abstract

The water immersion of surrounding rock slide surface causes lining cracking of the shallow buried loess tunnel, and different types of slide surface and different immersion degrees have different effects on secondary lining. In this paper, four types of slide surfaces for shallow buried loess tunnel are proposed. In order to find out the characteristics and laws of lining cracking under the effect of slide surface immersion, a loading model test with a large geometric similarity ratio of 1:10 was carried out. The test results show that the immersion of the slide surface has the most significant influence on the deformation of the lining vault and the arch waist, and the value and speed of the vault deformation are always the largest. When the unilateral slide surface is immersed in water, the lining cracking is concentrated on the flooded side of the slide surface, and the appearance of compressive cracks can be regarded as a precursor of lining instability. In the direction of lining thickness, the cracks always begin to develop from I-type, then gradually develop into L-type, and finally develop to Y-type, among which the number of L-type cracks is the most. Furthermore, the residual bearing capacity of cracked lining is also discussed.

Highlights

The excavation of a shallow buried loess tunnel causes changes and adjustments of the stress state of the overlying stratum in varying degrees
The slide surface is the most critical feature of the shallow buried loess tunnel, which provides a fast channel for the surface water infiltration [4], and the deepest slip surface can reach near the tunnel lining
This paper focus on the characteristics and laws of lining cracking under the effect of slide surface immersion, and a loading model test was carried out

Summary

Introduction

The excavation of a shallow buried loess tunnel causes changes and adjustments of the stress state of the overlying stratum in varying degrees. The cracks incline to the centerline line of the tunnel in the form of a curved surface in the depth direction and form a settlement grooves within a specific range of the stratum [1,2]. The soil in the groove is wedge-shaped and tends to slide toward the excavation free surface. The water immersion softens the loess around the slide surface, resulting in the mechanical property decays rapidly with the increase of the sinking tendency of sliding wedge, which may cause the loads on the support structure and the deformation to increase. The flooding of the slide surface is bound to have a significant impact on the appearance and development of cracks

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Conclusion