Study On Stability Characteristics And Construction Control Measures Of Surrounding Rock Of Large Cross-section Tunnel With Small Spacing

With the continuous development of highway industry,the construction of tunnels in complex mountainous areas is gradually increasing.The tunnels with large sections and small clear distances are widely used for saving traffic corridor resources and facilitating the exhibition line.Compared with the conventional small clear distance tunnel,large section with small clear distance tunnel section flat rate is low,the excavation disturbance and the characteristics of the interference is serious about hole,if continue to use conventional small clear distance tunnel reinforcement measures and construction methods of the risk of certain how the security under the premise of selecting reasonable excavation methods and supporting measures become the key to the problem.Therefore,this paper conducts in-depth research on surrounding rock stability characteristics and construction control measures of tunnel with large section and small clean distance.The main research contents and conclusions are as follows:(1)Combined with the structure form of the tunnel with large section and small clear distance,the plastic deformation element upper limit finite element method was used to establish the limit analysis model,and the evolution law of the stability and failure mode of surrounding rock under the comprehensive consideration of surrounding rock conditions,double hole clear distance and tunnel span was obtained.(2)Based on the strength reduction method,the stability coefficient and failure mode of surrounding rock of the tunnel with large section and small clean distance are obtained,and compared with the calculation results of limit analysis,and a reasonable spacing range with comprehensive consideration of safety and economy is obtained.(3)Analyze and study the large section construction method,evaluate its effect of stabilizing the surrounding rock and regulating the structural stress,and select the excavation method with different span,surrounding rock grade and double hole net distance according to the reasonable net distance range,combined with the surrounding rock displacement index and structural stress characteristics.(4)to explore the large cross section of small clear distance tunnel surrounding rock and en echelon department joint reinforcement measures,in order to make full use of the surrounding rock bearing capacity for the principle,the grouting reinforcement,anchor reinforcement and composite reinforcement forms in the supporting measures such as selection,comprehensive compare with the distance under the condition of double hole six lanes and double hole eight lanes of small clear distance tunnel and reasonable supporting methods,The effect of reinforcing measures on maintaining tunnel stability is pointed out.(5)Combined with the field engineering data,the design scheme of shapushan six-lane small clear distance tunnel is compared and analyzed,and the construction control measures of super-large section small clear distance tunnel are further discussed,and suggestions are put forward for weizaling eight-lane small clear distance tunnel construction from the perspective of clear distance optimization.