Stability Analysis And Treatment Measures Of Surrounding Rock In The Water-rich Section Of Junmachang Tunnel

In recent years,as the national economic strategy has shifted to the southwest region,industrial and civil buildings,highways,railways and other infrastructure construction also turned to the southwest region,due to the large number of mountainous landforms in the southwestern region of China,the tunnel project is inevitable.During the construction of the Junmachang tunnel on the Shanghe expressway in Yunnan Province,there was a lot of water seepage at the tunnel face,due to the development of fractured joints in the surrounding rock of the tunnel,crushing of the rock mass,and abundant groundwater,many difficulties are encountered in tunnel construction.Therefore,in this paper we take Junmachang tunnel project as an example,for the methods used in the construction of tunnels,such as "geological exploration in water-rich stratum,rock mechanics experiments,numerical simulation analysis,on-site monitoring and measurement" and other methods,this paper studies the stability evaluation and countermeasures of the surrounding rock of the water-rich stratum of the Junmachang tunnel.The main research of this article is:(1)Analyzed the weakening mechanism of groundwater on rock mass.Summed up the status of the study on both stability analysis method of tunnel surrounding rock and quo of grouting reinforcement technology.Retrieved relevant rock samples from the tunnel construction site.By comparing the experimental data of the uniaxial compression strength and the modulus of elasticity of the rock samples under the condition of dry and full water,the results show that the groundwater has a certain weakening effect on the surrounding rock of the tunnel.(2)Based on surveying the original data of the Junmachang tunnel design,high-density electrical geological exploration,geological radar advance forecasting techniques,and on-site surveys were used to accurately and accurately detect the geological conditions of the surrounding rock of the water-rich stratum of the tunnel.The geological conditions of the tunnel surrounding rock and the distribution of bad geological bodies were determined and provided the theoretical basis for the next numerical simulation analysis.(3)Based on the actual situation of the water-rich stratum of the Junmachang tunnel,a three-dimensional numerical analysis model was established using MIDAS/GTS NX.By comparative analysis of the distribution characteristics of surrounding rock displacement and stress during excavation under different tunnel surrounding rock levels,the weakening effect of groundwater on tunnel surrounding rock was revealed;The optimized construction parameters which can provide a basis for safe excavation and rock deformation control in the tunnel's water-rich stratum were obtained after comparing and analyzing the construction parameters of different grouting ring thicknesses and step heights,step lengths,and left and right excavation offset distances in the three-step and seven-step excavation method.(4)Through the regression analysis of field monitoring measurement data of the water-rich stratum of the Junmachang tunnel and the results of numerical simulation analysis,we studied the support and deformation control measures for the surrounding rock of the water-rich stratum of the tunnel,and proposed a reasonable reinforcement and disposal plan.Both the observation and the actual measurement results in the site show that the effect of deformation control of the surrounding rock is good,so it can provide relevant theoretical basis and scientific guidance for the stability control of the surrounding rock of the tunnel.