| With the continuous improvement of China’s infrastructure construction,China has achieved rapid development in the field of tunnel engineering research.However,under complex geological conditions the change in geological conditions not only affects the construction of the tunnel,but also overload the lining segments,severely damaging the tunnel structure.Therefore,it is of great engineering significance to study the damage mechanism and reinforcement measures of tunnel lining segments under complex geological conditions.Based on the damage mechanism problem of the lining segment in a diversion tunnel in the northwest region,this paper firstly proposes the use of systematic bolts to strengthen surrounding rock for the cracking of the lining segment caused by the change in geological conditions during construction,and evaluates the rationality of the reinforcement plan.Secondly,this paper analyzes the deformation law of the lining segment structure when the normal fault has different displacementsin response to lining segment dislocation and cracking in the active fault area.Finally,this paper analyzes the occurrence mechanism of large deformation of special soft rock,in view of cracking and structural failure of heavy segment in special largedeformation soft rock section,optimizes the original design support scheme,and finally makes a rational evaluation of the optimization scheme.The main work and conclusions are as follows:(1)This study proposes the use of systematic bolts to strengthen surrounding rock for the cracking of the lining segment caused by the change in geological conditions during construction,and evaluates the safety margin of the reinforcement plan.The results show that when the originally designed surrounding rock grade is adjusted from Class III to Class IV under the support of light segment,the reinforcement of the lining segment structure is greater than the design value of the concrete after the use of system anchor rod reinforcement is greater than 31.41%;light segment support When the grade of the lower original design wall rock was adjusted from Class III to Class V,after being reinforced with system bolts,the surplus of the lining segment structure was greater than 38.22% of the design value of the concrete;When the category is adjusted to category Ⅴ,after being reinforced with system bolts,the surplus of the lining segment structure is greater than 20.10% of the design value of concrete.It can be seen that the effect of the reinforcement scheme is significant.(2)When the tunnel passes through an active normal fault area,the lining segment structure is prone to staggered deformation at the location of the fault fracture zone,and the influence range of fault displacement on the deformation of the lining segment in the active disk area is about the same as that in the passive disk area.double.With the increase of fault offset distance,the lining segment structure firstly crushed and collapsed at the position of the invert and arch,and then at the top of the arch,the failure mode was tensile-extrusion failure.(3)For the special soft rock large deformation leading to heavy segment cracking and structural damage,this study believes that the mechanism of large deformation of surrounding rock in this area is the deformation of the surrounding rock under the action of weak surrounding rock and high ground stress,and it is recommended to use a long The supporting system composed of anchor rods,closed steel arch frames,backfill concrete in invert arches,cast-in-place reinforced concrete lining,etc.is optimized and changed to the original design of the supporting scheme.In the calculation and evaluation of the changing support plan,the lining structure redundancy is greater than 53.30% than the concrete design value,and greater than 66.72% compared with the concrete standard value,which proves that the change plan is reasonable and feasible. |
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