Study On The Stability Analysis Of Shallow Tunnel Considering Bottom Uplift Deformation

Once the surrounding rock destruction phenomenon occurs in shallow tunnel,it will give the surface buildings,pedestrians,vehicles and so on a huge threat to life and property.Therefore,the stability of the surrounding rock of shallow tunnel is very important for the tunnel engineering theory research and construction design.In this paper,the stability of shallow tunnels is studied from two aspects: the failure mode of surrounding rock and the pressure of surrounding.And the results are as follows:(1)Analysis of failure mechanism of shallow buried tunnel in weak surrounding rock condition,put forward the tunnel failure process of surrounding rock in the bottom will deform upward uplift,this phenomenon will not only affect the bottom of the tunnel,but also on the stability of the surrounding rock to produce adverse effects.(2)Considering the phenomenon of uplift deformation at the bottom of the tunnel,the upper limit method of limit analysis is adopted to establish the model for calculating the surrounding rock pressure of the shallow tunnel.And then,the expressions of the surrounding rock pressure of shallow tunnels are deduced.With the software programming,the optimal solution of the pressure of surrounding rock is obtained.(3)The calculation results of this paper are compared with the results of literatures and engineering test data,and the correctness of the method is obtained.On the basis of the above analysis,the influence of lateral pressure coefficient,soil bulk density,cohesion,internal friction angle,depth and span on the surrounding rock pressure of shallow tunnel are analyzed.(4)The model test was designed and carried out.The similar materials were made with barite powder,quartz sand and vaseline for the soil mechanics parameters of ? rock mass which can represent the urban geology.And the full-section excavation of the tunnel is simulated by extraction method.The damage process of the surrounding rock of the shallow tunnel is observed and analyzed,and the results are compared with the theoretical analysis.In this paper,the bottom uplift phenomenon after tunnel excavation is considered,which makes some useful attempts for the study of the failure modes of shallow tunnel,the calculation of the rock pressure and the stability of the tunnel.It can provide certain theoretical guidance for engineering practice.