Study On Stability Of Surrounding Rock And Optimization Of Primary Support Based On Xu-liang Tunnel Of Zheng-wan Railway

The methods of evaluating the stability of shallow-buried tunnel tend to be simple in the time,so the results from this method are inevitable to take a part for the whole,which could lead to uncountable economic loss in most of time.Based on Xu Liang tunnel of Zheng Wan high-speed railway,the paper combines finite element limit analysis method and convergence-confinement theory to evaluate its safety in a comprehensive way,at the same time,the monitored data in the field are used to verify the conclusion above.After this,optimization is conducted on the current support measures of Xu Liang tunnel,and then reasonable suggestions are recommended to it.Additionally,the contrastive test is made to compare the anchor effects between two common ways to anchor bolt,the main research results can be summarized as follows:(1)In the range of the entrance of Xu Liang tunnel to 85m away from it and the exit of Xu Liang tunnel to 320m away from it,the stability of surrounding rock is weak and there poses a threat of Shear sliding failure to side wall on the tunnel and the countermeasures should be prepared in the process of construction,in case of any injury.(2)The combination support of bolt,shotcrete,Steel frame in the tunnel is large in stiffness,so a soften support method is recommended to be adopted in the tunnel.(3)According to the monitored data in the field,the settlement of tunnel crown and the convergence deformation tend to be stable under current support mode,and the final displacements are in the range of the value from code.The stress of primary support can go through verification,which is less than its limit strength.(4)After removing the steel frame from origin support method,the convergence deformation increases about 9.0%;the axis force of shotcrete increases about 3.3%,and its moment increases about 22.9%;the axis force of bolt increases about 11.6%.In a word,whether canceling the steel frame or not,the force and displacement of support would be under the control,which suggest that the safety of tunnel would not be affected if removing the steel frame from the origin support method.(5)The anchoring effect of full grouting bolt is better than that of concrete-based cartridge in current geological condition and construction technology,so full grouting bolt is recommended to be used in the similar tunnel engineer.