Study On Ground Surface Treatment Measures For Topographically Biased Tunnels

Road tunnels are very common in China,and this is not unrelated to the fact that mountainous areas occupy a large proportion in our territory.However,during the construction of the tunnel,there is often a bias phenomenon.This will not only bring great difficulty to the construction,but may even cause danger during the construction process.In order to ensure the progress and safety of the tunnel construction process,different technical means are needed according to different types of different types of bias tunnels.Just as we often say that the right medicine,dealing with the bias problem,also need to "the right medicine",in order to "drug to disease." At present,the commonly used bias tunnel tunnel treatment measures in the project mainly include advanced support and step-by-step excavation.Commonly used external treatment measures for bias tunnels include cutting water drainage,back pressure backfilling,surface grouting,and setting of retaining structures.This paper coMPares and analyzes the applicable conditions of several surface treatment measures commonly used in engineering construction.Relying on the shallow buried section of the entrance of the Huitougou tunnel.The numerical simulation software was used to analyze the effect and economic benefits of the Huitougou tunnel after taking different surface treatment measures.In order to find the most suitable method to solve the bias problem of the return trench tunnel.And by this kind of coMParison of various technical means of the advantages and disadvantages,as well as the role of the terrain bias tunnel.It solves the key technical problems in the design and construction of terrain-biased tunnels,reduces the construction risk of terrain-biased tunnels,and increases the safety guarantee for the later operation of terrain-biased tunnels.It has important engineering practical significance.The conclusions obtained are as follows:(1)The sensitivity of the settlement of the tunnel to the burial depth is less than the sensitivity to the slope angle.The sensitivity of the stress received by the rock mass around the tunnel to the slope angle is greater than the sensitivity to the depth of the tunnel;(2)When the terrain bias tunnel is treated by the slope cutting method,as the angle of the slope increases,the deformation value of the rock mass around the tunnel gradually decreases,the stress concentration is relieved,and the inelastic deformation region gradually Decrease,the damage caused by the bias is getting smaller and smaller;(4)The effect of back pressure backfilling on the terrain bias tunnel bias is increased with the increase of the backfill angle;however,after reaching a certain critical angle,the backfill angle is increased to the tunnel deformation and The bias effect is small;(5)For the topographically biased tunnel with slope angle less than 26°,the drainage effect of slope selection is more significant;the topographic bias tunnel with slope angle greater than 26° has a significant effect on backfilling backfill;the surface grouting is relatively broken in the treatment of surrounding rock.Pores and fissures have obvious advantages in the development of topographically biased tunnels,and they are most effective for terrain-biased tunnels with a slope angle of less than 21° and a buried depth of more than 20 m;(6)Considering the effect and economic benefits of various surface treatment measures on tunnel bias,for the Huitougou tunnel,the backpressure backfill method is selected to fill the slope ratio from 1:1.5 to 1: 2 is the most reasonable,can not only solve the adverse effects of terrain bias on the tunnel,but also save construction costs.