Study On Deformation Mechanism And Control Of Soft Surrounding Rock Biased Tunnel

With the rapid development of traffic construction in mountainous areas of central and western China,the road tunnel projects continue to increase,there are more and more bad geological problems encountered during tunnel construction.During the excavation construction and operation of the tunnels problems such as initial lining cracking,intrusion or collapse,secondary lining cracking or slipping often occur,a series of problems,such as delays in construction period and increase in cost,directly affect the safety of tunnel construction and operation.To this end,this paper combines the No.2 tunnel project of JiuBuJiang in You County,Zhuzhou City,Hunan Province,search for the reason of analysis and optimization of excavation scheme for the problem of the initial branch intrusion caused by large deformation of surrounding rock in the weak surrounding rock section of the tunnel.Through the actual monitoring and measurement data obtained on site,combined with tunnel engineering construction theory and numerical simulation method,the following conclusions were drawn:(1)Through the on-site monitoring and data analysis of the large deformation area of surrounding rock in the tunnel,the development law and deformation mechanism of surrounding rock deformation of shallow buried tunnel are summarized.That is to say,in the initial stage,the deformation rate of the surrounding rock is fast,the deformation is large,and the deformation lasts for a long time,which is easy to cause large deformation of the surrounding rock.After the initial support and the inverted arch are closed,the surrounding rock deformation tends to be stable.The soft surrounding rock tunnel caused the deformation of surrounding rock due to uneven geological distribution and construction methods.The bias caused by the uneven geological distribution caused uneven settlement of the surrounding rock of the tunnel vault.Side settlement is greater than the other side.(2)The Midas/GTS numerical simulation software was used to simulate the excavation process of three-step method,three-step seven-step core method and CRD method.The displacement deformation characteristics and stress distribution characteristics of surrounding rock of different excavation methods were analyzed.The calculation results show that the original three steps The method of excavation has great influence on the stability of the surrounding rock of the tunnel vault.The maximum settlement is the largest,and the maximum settlement occurs on the biased side.The three-step seven-step core method and the CRD method can not only effectively control the bias voltage.The surrounding rock is unevenly settled,and the deformation of the surrounding rock can be effectively controlled.(3)According to the deformation mechanism and control principle of the surrounding rock of the weak surrounding rock,the pre-grouting of the surrounding rock at the top of the tunnel face is proposed,and the excavation is carried out by numerical simulation and subsequent actual monitoring.The rock deformation data has a significant improvement over the on-site monitoring data without grouting.Therefore,the pre-grouting reinforcement of the weak surrounding rock bias tunnel can obviously improve the overall stability of the surrounding rock,effectively control the surrounding rock deformation,and ensure the safety of the tunnel.The conclusions obtained provide optimization suggestions for the construction of the project.Provide reference and reference for similar projects.