Research On Large Deformation Prediction Of Weak Rock And Supporting Measures In Maoxian Section Of Chengdu-Lanzhou Railway

The large deformation of the weak rock is serious in the Maoxian section of the newly built Lanzhou railway,large deformation,long duration,timeliness.The prediction,prevention and control of large deformation of surrounding rock is an important part of large deformation research.The influencing factors of large deformation of weak rock are complicated.The experience of prediction and evaluation of large deformation of weak rock in other tunnels can not be fully adapted to the Chengdu-Lanzhou Railway.The large deformation of weak rock tunnel has become a bottleneck in the construction of Chendu-Lanzhou Railway.This thesis summarizes the types,characteristics and factors of the large deformation in the Chengdu-Lanzhou railway tunnel,based on the analysis of the large deformation's data of the weak rock tunnel in the route of Maoxian of the newly built Chengdu-Lanzhou Railway.The method of three-dimensional numerical analysis of complex terrain is proposed,which is based on the measured results of ground.Numerical simulation is used to invert the regional stress environment of Maoxian section(including Yangjiaping tunnel,Maoxian tunnel and Liutongzhai tunnel).Combined with the actual deformation inversion of the typical tunnel section,we analysed the influence of the geostress size and direction,the tunnel diameter and the formation of the rock formation on the deformation.The prediction formula of large deformation of weak rock in tunnel is established,and the large deformation of weak rock in Maoxian section of Chengdu-Lanzhou railway is forecasted and evaluated.The effeciency of the control measures for the large deformation of weak rock in Chengdu-Lanzhou tunnel is analyzed.The results show that the large deformation of Yangjiaping tunnel on Chengdu-Lanzhou railway is the deformation of weak rock,large deformation of extrusion,and large deformation of bulk deformation.In the complex geological structure,high geostress,weak lithologic stratigraphic lithology,Two-line small-distance construction and two-line support measures are not equal,the impact of groundwater softening interaction and other factors.The relationship between the three-way principal stress values of the Maoxian section is SH>SV>Sh,the stress of the geostress is dominated by the regional tectonic stress,the dominant value of the maximum principal stress is about N31 °?55° W,50%The above sections are extremely high stress sections.The original design measures accounted for 84.7%of the serious deformation section of Yangjiaping tunnel,23.7%of the large deformation section of Maoxian tunnel,and 16.9%of the large deformation section of Liutongzhai tunnel.After the original measures have been changed,the deformation control requirements are met.The method of large deformation prediction and the deformation control measures can be applied to the construction of other weak rock tunnels in Chenglan railway.