Appropriate clear distance and reinforcement measures for shallow buried bias pressure tunnel with different spans and small clearance
Taking the Shangxinguang Tunnel of Xinjiang Wuwei Expressway as the background,this paper in-vestigates the appropriate clear distance and reinforcement measures for tunnels with different spans and small clear distances.Using MIDAS GTS NX software to establish a finite element model of the tunnel,the horizontal displacement,vertical displacement,plastic zone,and vertical stress distribution of the intermediate rock under different net distance tunnel conditions are analyzed to determine the reasonable clear distance range for small clear distance tunnels,and the intermediate rock column is reinforced with small diameter grouting.The results show that the vertical stress curve of the middle interlayer rock has a concave distribution,with the vertical stress concentrated at the arch position of the left and right tunnels,while the stress distribution at the midpoint of the connecting line is smaller.The settlement of the arch crown and the ground surface is within the reserved settlement of 150 mm.The reasonable clear distance for the small clear distance tunnel is between 1B and 2B,and the clear distance for the upper Shangxinguang Tunnel exit section is 15.4 m,which meets the design val-ue of the small clear distance tunnel.By using measures such as small diameter grouting reinforcement,the sta-bility and integrity of the middle interlayer rock pillar can be enhanced,thereby reducing the deformation of the surrounding rock.