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| Back Analysis on Deformation and Failure Zone Distribution Laws of Surrounding Rock in Deep - buried Soft Rock Tunnel |
| YU Yuan - xiang1，CHEN Bao - ping1，ZHANG Tao2，ZHANG Jie1 |
| (1. Xiran University of Science and Technology，Xiran，Shaanxi 710054，China;2. Second Engineering Division，China
Railway Twelfth Group Co. Ltd，Taiyuan，Shanxi 030032，China) |
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Abstract Abstract ： Research purposes ： Liutongzliai tunnel is the critical engineering of the new railway line from Chengdou to
Lanzhou，whose large deformation problem is very prominent， while there is no perfect calculation method for the
deformation prediction of the deep tunnel surrounding rock on the condition of rock rheology. Based on the summary of
existing research results of surrounding rock deformation，the surrounding rock of the tunnel was simplified as an elastic plastic medium，in which full - column anchor bolts have been laid. This paper analyzed the surface friction and axial
force distribution law of the bolt body by the coordination function principle between surrounding rock and bolt and the
maximum axial force value of bolt neutral point was derived according to the static equilibrium condition. On this basis， the formulas about the radius of plastic zone and loose zone after the surrounding rock deformation ceased were proposed. Finally，it determined theoretically loose zone and plastic zone range of Liutongzhai tunnel surrounding rock， which
provided important technical support for optimization of surrounding rock support scheme as well as parameters. Research conclusions ：( 1) In engineering practice ; rock rheology is the basic reason for the deep - buried tunnel large
deformation. Generally speaking, the surrounding rock tends to stabilize after a period of initial bolting support. (2)The
surrounding rock and bolt body deform coordinately. The interface of the positive and negative friction on the bolt body
surface is neutral point, on which the relative displacement between bolt and surrounding rock as well as surface friction is zero, while the axial tensile force reaches the maximum. ( 3 ) The stable plastic zone and loose zone range of the surrounding rock can be analyzed conversely making use of maximum axial force of bolt body, whose size decreases with
increase of the cohesion and internal friction angle of rock mass and enlarges with increase of tunnel radius. It has little
relationship with the support resistance. (4) Field application results show that deformation zone distribution laws of the
tunnel surrounding rock may be analyzed back on the basis of known bolt axial force. The research findings can be used for reference for safe and rapid construction of similar tunnel engineering.
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Received: 09 November 2016
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2017, Vol. 34 
