Large deformation of tunnels in steep dip strata of interbedding phyllite under high geostresses
LI Lei1，2，TAN Zhongsheng1，2，GUO Xiaolong1，2，WU Yongsheng1，2，LUO Ningning3
(1. School of Civil Engineering，Beijing Jiaotong University，Beijing 100044，China；2. Tunnel and Underground Engineering Research Center of Ministry of Education，Beijing Jiaotong University，Beijing，100044，China；3. Chengdu Engineering Co.，Ltd.，China Railway Bureau 5 Group，Chengdu，Sichuan 610073，China)
Abstract：The large deformation of surrounding rocks is easily induced in the tunnel excavation in steep dip and soft rock strata under high geostress conditions. Yangjiaping Tunnel was investigated to identify the factors causing the large deformation，to analyze the failure mechanism and deformation characteristics of surrounding rocks and the internal forces in the supporting structure and to propose a rational method of control. The in-situ sampling was carried out to analyze the significant anisotropic characteristics of chlorite phyllite and to determine the relationships between the load direction and failure mode of rock. The in-situ observations and numerical simulation results showed that the deformation of surrounding rock converged as a whole and the horizontal displacement of convergence was larger than the vault settlement. The bending damage in horizontal direction and the separation of bedding planes were found mainly in the side walls of tunnel. The maximum principal stress in the side walls is distributed like“＜”and“＞”. The main failure mode of tunnel vault and invert is shear slip failure and the maximum principal stress is along the tangential direction of the tunnel. The factors inducing the large deformation are high tectonic stress，adverse stratigraphic occurrence and low rock strength. The results of in-situ experiments show that combinations of long and short bolts intersected with rock strata with large angles together with grouting can strengthen the surrounding rock effectively and adjust the surrounding rock pressure. Reducing the excavation steps led to the initial support be closed sooner and the bearing capacity of primary lining was thus fully utilized. Optimizing the cross section profiles can improve the loading on the support structures.
李 磊1，2，谭忠盛1，2，郭小龙1，2，吴永胜1，2，罗宁宁3. 高地应力陡倾互层千枚岩地层隧道大变形研究[J]. 岩石力学与工程学报, 2017, 36(7): 1611-1622.
LI Lei1，2，TAN Zhongsheng1，2，GUO Xiaolong1，2，WU Yongsheng1，2，LUO Ningning3. Large deformation of tunnels in steep dip strata of interbedding phyllite under high geostresses. , 2017, 36(7): 1611-1622.
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2017, Vol. 36 
