Research On Spatio-temporal Evolution Law Of Stress Characteristics Of Surrounding Rock And Lining Of High Ground Temperature Diversion Tunnel

This paper combines a high ground temperature diversion tunnel in Xinjiang,using the way of theoretical analysis,field tests and numerical simulations to study the mechanical characteristics of the surrounding rock and lining structure of the high ground temperature hydraulic tunnel,the damage area of the surrounding rock excavation during construction,and the entire construction process.The spatial and temporal evolution of the stress characteristics of surrounding rock-lined hydraulic tunnels has been studied and analyzed.Some conclusions are as follows:(1)Study on the stress characteristics of surrounding rock and lining structure of high ground temperature hydraulic tunnel.Different Poisson’s ratios of surrounding rocks of high ground temperature hydraulic tunnels during the completion period can affect the distribution of stress fields of surrounding rocks and lining structures.With the decrease of Poisson’s ratio of surrounding rocks,the stress field of surrounding rocks and lining structure of hydraulic tunnels decreases;With the increase of Poisson’s ratio,the maximum increase of hoop stress of surrounding rock top arch can reach 126%,and the maximum increase of hoop stress of lining can reach 384%.It can be seen that the hoop stress of the surrounding arch and lining structure is affected more by the change of the Poisson’s ratio of the surrounding rock.(2)Study on excavation damage area of surrounding rock of high ground temperature hydraulic tunnel.Within 130 days of tunnel excavation,the displacement of the surrounding rock is decreasing along the entrance of the tunnel to the deep part of the surrounding rock.The rock mass within the range of5.0-7.0m of the tunnel’s top arch and side wall is significantly affected by the excavation;After the tunnel is excavated,the state of the rock mass can be roughly divided into three regions,which are rock fragmentation zone,rock disturbance zone and complete rock zone,and the integrity of the surrounding rock is worse within 7-9m of the hole depth;The plastic area of rock excavation is ’butterfly-shaped’,and the surrounding rock orifice are significantly affected by excavation and the plastic strain here is greater.The maximum plastic strain of the surrounding rock is 0.0022,and the maximum length of the plastic area is 9.0 m.It can be determined comprehensively that the extent of damage to the surrounding rock excavation is generally within 9m from the orifice.The surrounding rock stability in this area is poor,and corresponding support measures should be taken in time.(3)Study on spatiotemporal evolution of surrounding rock and lining structure of high ground temperature hydraulic tunnel.During the construction period,the maximum principal stresses of the surrounding rock of the high ground temperature hydraulic tunnel are all tensile stresses and as the time increases,the maximum principal stress gradually decreases;the change of the maximum principal stress of the surrounding rock top arch and waist arch with time can be divided into three stages,the stress reduction period,the stress fluctuation period and the stress stabilization period,which can be referred to to carry out corresponding reinforcement measures for the surrounding rock when constructing rock masses with complex geological conditions;the upper part of the surrounding rock has a larger displacement,the lower part has a smaller displacement,and the maximum displacement appears at the top arch of the tunnel.Thelarger part of the surrounding rock stress has a smaller displacement.Surrounding rock stress and displacement can form a mutual contrast.The lining top and bottom arches mainly generate compressive stress and the lining waist arches mainly generate tensile stress.The displacement of the lining structure is more uniform.The displacement of the lining top arch is larger than the waist arch,the top displacement is larger and the bottom displacement is smaller.The internal displacement of the lining is larger and the external displacement is smaller;plastic strain occurs on the lining top and bottom arches on the external of the lining structure,and plastic strain occurs on the lining top,waist,and bottom arches on the internal of the lining.The plastic strain increases with the excavation depth,and the plastic strain of the top arch of the lining structure is the largest at the excavation depth of 50 m.The spatiotemporal distribution of surrounding rocks and lining structures have a good consistency,which can be contrasted with each other.The maximum principal stress fluctuations in the waist arches of the surrounding rock and the lining structure are large,and the maximum displacement and the maximum plastic strain occur at the lining waist arch.Therefore,when designing and constructing the project,it is necessary to take corresponding measures to maintain the stability of the surrounding rock waist arch and increase the concrete strength of the lining waist arch if it is necessary.