Analysis On Disease Cause And Study On Treatment Method Of Highway Tunnel Crossing Fault Fracture Zone

As an important part of the tunnel civil structure,the pavement directly affects the overall stability of the tunnel structure.Uneven deformation,cracking,and staggering of the pavement will cause serious threats to driving safety.During the treatment of the diseases,the excavation and reinforcement of the tunnel bottom will cause disturbance to the original lining structure,and the degree of disturbance can be known by monitoring and measurement.Relying on "Baotashan Tunnel Disease Treatment Project of Pingyao ～ Yushe Section of Fenyang-Xingtai Expressway",through geological survey,disease statistics,pavement elevation measurement,and tunnel bottom excavation,the factors causing the diseases are preliminarily determined,and block discrete element software is used to simulate the diseases,and verify the causes of the diseases.In the process of tunnel bottom excavation and reinforcement,the deformation of the crown and side wall is measured,and the deformation law of the lining is obtained.Based on the disease simulation model,the simulation of tunnel bottom excavation and reinforcement was carried out,and the deformation law of the crown and side walls measured on site was compared and verified.Finally,based on the disease simulation model,different excavation and protection methods at the bottom of the tunnel are optimized and simulated.The stability of the original support structure under different construction methods is obtained,and the corresponding construction suggestions are put forward with reference to the site construction conditions.The main research results are as follows:(1)The causes of the Baotashan tunnel diseases are caused by many factors,which can be divided into fault fracture zone,ground stress,groundwater intrusion,and weak support at the bottom of the tunnel.(2)During the excavation and reinforcement of the tunnel bottom,the deformation of the lining is mainly the deformation of the side wall in the excavation of the pavement.The influence range of side wall settlement and side wall convergence is about 10 m and 6m respectively;within the influence range,the deformation of the side wall is parabolic,and the peak value is located at the central cross section of the excavation area;within the scope of settlement influence,the maximum cumulative deformation of monitoring item is linearly increased with the length of the excavation unit.When the length of the excavation unit reaches 5m,local yielding occurs at the side wall of the excavation area.It is suggested that the excavation unit length should be less than 5m during construction.(3)When the excavation interval between the two units is less than 2 times the influence range,the influence ranges affect each other;when the excavation interval is greater than the single influence range and less than twice the influence range,the fluctuation of the maximum cumulative deformation of each monitoring item is relatively small.Therefore,it should be ensured that the excavation interval is greater than 2 times the settlement impact range,and in the case of unsatisfactory conditions,it can be less than 2 times settlement impact range and greater than single settlement impact range.(4)For the protective structure of tunnel bottom excavation,the stress state of lock foot anchor pipe of the same cross-section arrangement and plum blossom arrangement are basically the same,and the deformation of the crown and the side wall is basically the same,in order to facilitate on-site construction,the lock foot anchor pipe arranged on the same section can be used.During half-width excavation and reinforcement of the pavement,the 50 cm protective structure is reserved in the carriageway to effectively control the deformation of the foundation pit and facilitate on-site construction.(5)Compared with the full-width excavation and reinforcement of the pavement,the half-width excavation and reinforcement will have a small disturbance to the supporting structure in a single time,but it will cause a second disturbance.Considering the stability of the supporting structure,the construction difficulty and structural quality,it is suggested to adopt the full excavation and reinforcement construction scheme.(6)The monitoring section spacing should be formulated according to the excavation interval,and the monitoring section should be arranged at the central section of the excavation area;the monitoring range may not extend to the unreinforced section;the monitoring project should increase the monitoring of the settlement of the side wall,and the deformation of the side wall should be used as the basis for construction guidance.