| In recent years,with the rapid development of China’s economy,great achievements have been made in many aspects,especially in the field of tunnel construction.The most famous one is the Mubaishan Tunnel,and its maximum depth of penetration has reached 1650 meters.Numerous engineering studies have shown that as the depth of tunnels increases,the temperature and stress of the tunnels will be larger and larger.Compared with shallow tunnels,deep tunnels are more prone to various types.Engineering geological disasters.It is the basic principle of the modern support principle to give full play to the self-supporting ability of the surrounding rock and to exert the bearing capacity of the supporting material as much as possible.In order to realize these two basic principles,it is necessary to quantify the self-supporting ability of the surrounding rock and the bearing capacity of the supporting material..Therefore,this paper introduces the catastrophe theory into the finite element strength reduction method,and proposes a method to quantify the bearing capacity of the surrounding rock and the bearing capacity of the supporting structure.Firstly,the development history of underground structure and the research status of self-stability of deep-buried tunnels at home and abroad are summarized.The strength reduction method is systematically expounded,and the solution process,advantages and disadvantages of finite element software Phase~2 are introduced.The Mohr-Coulomb yield criterion is described in detail from three aspects;Secondly,the cusp catastrophe model is introduced to derive the discriminant of tunnel instability and the combination of highway tunnel design specifications.It is determined that the deep tunnel can maintain self-stability under the condition of Class II surrounding rock and obtain the self-stability coefficient.A quantitative method for determining the self-stability of surrounding rock of deep tunnels is determined;Then,using the orthogonal experimental design,through the value calculation of Phase~2,the degree of influence of factors such as cohesion,internal friction angle,elastic modulus,Poisson’s ratio,span and buried depth on the tunnel self-stability coefficient is obtained by the range analysis.Finally,the support mechanism of different supporting structures is analyzed,the self-stability of the surrounding rock of III~V is quantified,and the concept of support replenishment coefficient is proposed.The support structure of the excavation tunnel under all surrounding rock is provided.The bearing capacity of the tunnel is supported by the bearing capacity and the supporting standard in the specification.The stability coefficient of the tunnel after the support is quantified,and the supporting effect of different supporting structures is analyzed.Combined with the examples of the Luoyixi Tunnel and the Liziping Tunnel,the feasibility of quantifying the self-stabilizing ability of the tunnel and the bearing capacity of the supporting structure is further verified. |
