Research On Control Technology Of Deformation And Cracking Of Weak Surrounding Rock Tunnel In Red Layer Region Of Central Yunnan

With the development of traffic construction in our country, the problem of large deformation in weak rock tunnel has emerged in a number of engineering practice, resulting in surrounding rock intrude into limit, cracking of primary support, and even collapse. The article combined with the project of Laodongshan tunnel being constructed in Guang-Kun Railway, which is in the typical Red Layer Region of Central Yunnan, By the methods of field investigation and theoretical analysis, field test and numerical simulation, The problem of tunnel construction in weak rock were studied, the mechanism and causes of surrounding rock broken and large deformation of the soft rock tunnel in the Red Layer Region of Central Yunnan were explored, the interaction mechanism of weak surrounding rock and supporting structure were analysised, the control measures of large deformation of the soft rock tunnel in the Red Layer Region of Central Yunnan were studied and put forward. The main research methods and results were as follows:(1) On the basis of investigating the surrounding soft rock tunnel and hydrogeology situation with large deformation in the Red Layer Region of Central Yunnan, the deformation and failure characteristics and the mechanism of tunnel surrounding rock were analysised through in-situ stress test and typical cross section of the vault settlement, horizontal convergence, surrounding rock stress and section stress test results.(2) By the method of load-structure, the primary support of soft rock tunnel in the Red Layer Region of Central Yunnan under different lateral pressure coefficients and different supporting time, supporting stiffness and arch foot supporting under the condition of internal force distribution were calculated and analysised, the primary support stress distribution rule under the condition of different parameters of tunnel were obtained. (3) The interaction mechanism soft rock and supporting structure under high initial geostress conditions in the Red Layer Region of Central Yunnan were researched, the deformation control principle of "combination technology with resistance and release and strength primary support" and the deformation controlling principles and ideas of "the reinforcement in advance, combination technology with resistance and release, prefer strength to weakness, prefer repair to remove, change along with rock, keep up with construction process, quickly closed" were proposed.(4) The tunnel construction processes were optimization analysised by the method of numerical simulation, through the influence law of tunnel structure of excavation sequence, step length and the time of second lining were analysised and the corresponding suggestions were given.(5) According to the deformation controlling principles of soft rock tunnel in the Red Layer Region of Central Yunnan, combined with the engineering practice of Laodongshan Tunnel, the fast dynamic and comprehensive technology of soft rock tunnel with great deformation in Red Layer Region of Central Yunnan was formed and controlling the large deformation of soft rock tunnel was ensured.