Research On The Large Deformation Mechanism And Control Measures Of Soft Fractured Surrounding Rock Tunnel

With the high-speed railway tunnel increasing, the large deformation problems of soft fractured surrounding rock has also appeared in a lot of tunnel engineerings, and that increased gradually exceeding clearance limit, primary support craze and even collapse, and some other large deformation disasters. The large deformation problems are always the key and difficult in the construction process of soft fractured surrounding rock tunnel. To prevent the occurrence of the large deformation disasters, the effective support measures are needed. Taking the Lao Dongshan tunnel in Guang Kun railway as the background, by the method of site investigation, theoretical analysis, site monitoring and numerical simulation, this paper researched deeply on the large deformation mechanism of soft fractured surrounding rock and control measures. The main research method and the results are as follows:1. Surveyed the groundwater and surrounding rock conditions in the large deformation tunnel section; monitored the typical section of the tunnel, and the results show that the vault settlement, all of the level convergence, surrounding rockmass pressure and the steel stress have obviously space-time effect.2. Based on the measuring results of typical section and the site investigation of large deformation section, this tunnel has obvious large deformation characteristics, like that large deformation value, large deformation range, primary support crack and drop, edge in the side wall and so on. And on the basis of that, researched deeply on the large deformation mechanism of soft fractured surrounding rock tunnel, from the surrounding rock lithology, structure and environment.3. Discussed the construction technology and the supporting measures of soft fractured surrounding rock tunnel; in reference to the control measures of domestic and foreign soft fractured tunnel, determined that the construction method is3-bench7-step excavation method for the basing project, the primary support is the combination support of belt, shotcreting and mesh, and the assistance supporting measure is leading ductile. Leading ductule injecting is thought about on the rich in groundwater and the softer setion of the surrounding rock.4. Compared the parameters of the tunnel construction methods and key support measures in the numerical simulation method; through the analysis on the large deformation law of surrounding rock, effected by the construction methods and the supporting measures, and compared with the site supporting parameters, the suggested values of key support parameters.are given.5. Based on the rheological theory, got the limit displacement of support structure of typical section on the method of numerical simulation; fitted the deformation law of the site measurement data, got that the lining should be constructed on15th day after working face excavated according to the limit displacement, and it is easy to instruct on-site construction.