| With the advance of the traffic patch board in the west,the problem of tunnel bias is becoming more and more common in the project,which threatens the safety of the project and affects the construction and operation of the tunnel.The causes of bias tunnel are mainly divided into three categories: topographic factors,geological factors and construction factors.But at present,the existing research is mostly carried out in a single factor,and lacks systematicness.Based on the engineering background of Yitou Tunnel of Yibin-Bijie Expressway,this paper summarizes and analyzes the data of vault settlement and horizontal convergence of tunnel;adopts 3 DEC discrete element software to study the influence of geological and topographic factors on the deformation of tunnel under the simultaneous action of bedding thickness and dip angle of based on the properties of rock mass and structural plane,layer thickness,dip angle of rock stratum,slope angle of slope and depth of tunnel,the orthogonal test is designed and the factors affecting the deformation of surrounding rock are analyzed by polar difference analysis.A theoretical system for evaluating tunnel bias of layered rock mass is proposed.The optimal excavation sequence research results,the optimal excavation sequence is studied in three working conditions,i.e.,the topographic factor control and geological factor control.The results and conclusions of the study are as follows:(1)Based on the monitoring data of the head tunnel,the variation of the displacement of the three points of the dome settlement over 120 mm,at the monitoring point is different,and the bias characteristics of the deformation of the head tunnel section acting as geological and topographic factors are determined.(2)The discrete element model of head tunnel is established,and the reasonable excavation depth of head tunnel siltstone model is determined by trial calculation to be 32 m,and compared with the actual monitoring data,the validity of the model is verified.(3)The research reveals the deformation law of the tunnel when the thickness of the layered rock tunnel and the inclination of the rock layer change when the topographic bias exists.When the thickness of the rock layer is less than a certain value,this paper is about 5m.With the thickness of the rock layer decreasing,the cave deformation continues to increase;but when the thickness is too small,the text is about 1 m,the deformation is reduced.The anti-dip rock layer has the terrain bias pressure and the geological bias pressure crossing to control the deformation of the surrounding rock.(4)The control index of bias deformation of the tunnel of the along-tilt layered rock mass is studied by using the range analysis method through orthogonal experiment.The main influencing factors of the deformation of the tunnel chamber in the deep buried side are the rock mass and the structural surface properties,the main influencing factors of the deformation of the two walls of the tunnel chamber in the shallow buried side are the layer thickness,and the main influencing factors of the deformation at the top of the tunnel are the slope angle.The deformation of the inverted arch in the left and right tunnels is controlled by the properties of rock mass and structural plane.(5)For the layered rock mass bias tunnel,a comprehensive construction control method is proposed to optimize the tunnel construction sequence anchor length anchor angle,and the optimal tunnel construction sequence,the influence law of anchor length and anchor angle arrangement form change on the surrounding rock deformation is obtained in different working conditions,which provides the theoretical basis for antibias pressure and a relatively complete construction control optimization scheme. |
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