Research Of The Self-Anchored Reinforcement Structure For The Landslide Tunnel

In generally, tunnel design is mainly based on the bearing and deformation of the cross section, but the longitudinal is less considered. The related tunnel design standards have less items about this part, then it is lack of theoretical basis for the design of tunnel in landslide. On the other hand, most of the treatment measures of tunnel in landslide is divided into tunnel and landslide traditionally, which need a huge amount of engineering work but can’t cure it fundamentally.This paper is focused on the reinforcement of tunnels located near the sliding surface of deep landslide. A new type of self-anchored strengthening structure is proposed to solve the reinforcement of tunnel in landslide. Theoretical analysis, numerical simulation and physical model were carried out to study the bearing behavior of tunnel in landslide and the reinforcement effect of self-anchored strengthening structure. Through these work, the main achievements are summarized as follow:(1) Under the landslide force, the stable rock and soil masses in slide bed have anchoring effect on the tunnel in the sliding mass. The displacement of the tunnel are mostly occurred in sliding mass. When the tunnel spans relatively large in sliding mass, the center section will range a constant value. The bearing force is worst in the boundary of tunnel and landslide. With the increasing of landslide force, as well as the difference of normal foundation coefficient in and out of the sliding mass, the rangeability of the internal force becomes larger, which is the weakness of bearing and deformation in tunnel.(2) In the analysis of the reinforcement structure, the force system of tunnel is decomposed in the xoy plane and yoz plane. In the xoy plane, the anti-slide sustaining piles restrict the deformation and improve the internal force distribution of the tunnel, which have dominate effect on the tunnel stability. In the xoz plane, the anti-slide sustaining pile and anchor cable restrict the tunnel deformation and improve the internal force distribution together. In practical engineering design, the design value of anchor force in the boundary of tunnel and landslide should be increased to effectively improve the stress states of the tunnel in this scope.(3) Based on the case study, it can be seen that the bearing force and deformation of the tunnel both decrease greatly, and the distribution of internal force is more uniform and reasonable when strengthened by anti-slide sustaining piles and anchor cables. It verifies the well reinforcement effect of the new self-anchored reinforcement structure.(4) The results of numerical simulation shows that:the tunnel in landslide suffers from obviously unsymmetrically pressed. Serious stress concentration will appear in the boundary of tunnel and slip surface. In the center section, the displacement value of tunnel will be the largest and gradually decreases to the sides.Compared with the tunnel un-strengthened, the unsymmetrical pressure of the landslide load decreases, and the bearing force of the tunnel becomes relatively uniform, while the deformation law of tunnel is similar with the strengthened case. When strengthened by the anchor cables and anti-slide sustaining piles, the maximum principal stress of the tunnel decreases obviously, the stress concentration area in the boundary disappears, the internal force distribution of the tunnel are more reasonable and the deformation is well controlled. The anti-slide sustaining piles restrain the tunnel deformation in both horizontal and vertical, while the anchor cables mainly work in the horizontal. The anti-slide sustaining piles and anchor cables only strengthen the rock and soil masses around and down the tunnel, and have little effects on the strengthen of whole landslide. The final failure of landslide should be overtopping, which verifies that the reinforcement idea of this paper that only rescue the tunnel but ignore the landslide is feasible.(5) The test results show that:the distribution and change law affected by the landslide force of moment and displacement in tunnel agree with the theoretical calculation results, which verifies the validity of proposed computing. Compared the internal force and displacement distribution of the strengthened tunnel with the un-strengthened under the same load grade, as well as the deformation and failure behavior of the tunnel when slipping, the well reinforcement effect of the new self-anchored reinforcement structure is verified.