Research On Construction Optimization And Treatment Technology For Shallow Buried Large Span Tunnel Section With Poor Geology

In recent years,with the rapid development of China’s economy,the mileage of highways is also increasing day by day,when building highways in mountainous areas,compared with mountain roads,the construction of tunnels is a better choice,because compared with mountain roads not only has the advantages of reducing the car climbing altitude,reduce the time of traffic,protect the ecological environment of the mountain,increase the safety of car driving,and so on,and therefore by the majority of construction,design,construction personnel.construction.However,during the construction of tunnels,problems such as large tunnel deformations,initial support encroachments,collapse of the tunnel envelope and water and mud surges are often encountered,especially when building large span tunnels in shallow buried areas.It is therefore necessary to optimise the construction of large span tunnels in shallow burial situations and to study the adverse geological problems encountered.In this paper,the Lotus Tunnel of Pinglian Expressway in Jiangxi Province is used as the backing project to obtain on-site measurement data through monitoring and measurement work,to establish a model using grey theory,to predict the development trend of rock deformation,to monitor the amount of water gushing out of the section,to use numerical simulation software to simulate the impact of three different excavation methods on the stress,displacement and anchor shaft force of the tunnel surrounding rock and three different excavation methods on the shallow buried section,respectively.The impact of three different excavation methods on the tunnel and three different excavation methods on the tunnel,followed by further studies on the tunnel deformation intrusion section,the shallow buried collapse section and the water surge section.The following aspects of the paper have been completed:(1)The construction monitoring and measurement of rock deformation is carried out on the section of tunnel with large initial deformation and shallow buried collapse section.Based on the on-site monitoring and measurement data,the grey theory model and improved grey model are used to predict the development trend of rock deformation and compare the prediction accuracy of both to guide the on-site construction.Monitoring of the amount of water gushing out of the mud section,according to the measured results to determine the applicability of the water gushing prediction formula.(2)The GTS NX software was used to firstly simulate the construction of a large deformation intrusion section of the tunnel,and to simulate the effects of the up-and-down step method,the double sidewall pit guide method and the three-step seven-step excavation method on the deformation and stress of the tunnel surrounding rock and the axial force of the anchor rods,and then to simulate the effects of the up-and-down step method,the double sidewall pit guide method and the CRD method on the deformation and stress of the tunnel surrounding rock and the axial force of the anchor rods.The pattern.By comparing the results of these excavation methods,the construction methods for the large deformation and collapse sections of the tunnel were optimised.(3)For the section of tunnel with large deformation and encroachment,analyze the causes of encroachment and encroachment,propose two construction solutions: partial arch replacement and demolition and redo,compare the advantages and disadvantages of the two solutions,determine the use of partial arch replacement measures for treatment,and evaluate the effect of treatment;for the section of tunnel with shallow buried collapse,analyze the causes of collapse,propose the use of overrunning small conduit grouting,overrunning anchor,overrunning pipe shed three construction solutions and compare the advantages and disadvantages of the three solutions The advantages and disadvantages of the three options,determine the use of overrunning tube shed construction program for treatment,and evaluation of the treatment effect;for the water and mud emergence section,analysis of the causes of water and mud emergence,proposed in-cavity grouting,surface grouting and in-cavity,surface joint grouting three construction programs and compare the advantages and disadvantages of the three programs,determine the use of in-cavity,surface joint grouting program for treatment.