Stability Analysis Of Rocky Underground Structures Based On Hoek-Brown Strain-softening Model

In recent years,traffic construction has developed rapidly.In the construction of transportation systems such as railways and highways,it is inevitable that tunnel construction is required.At the same time,its scale is growing and the environment in which it is built is also diverse,which makes it difficult to design and construct the tunnel.Due to the complexity of the roads and railway tunnels built in China and the complexity of the environment,the supporting structure of the underground engineering is very different from the ground structure.At present,the tunnel support design is still in the stage of empirical or semi-empirical methods.At present,the tunnel design method has the following problems:1.This kind of design analysis method can not determine the safety factor of the tunnel under different support timings,and can not quantitatively and comprehensively analyze the safety of the tunnel,which causes great uncertainty in the design of the tunnel,for example,the installation start position of the anchor spray support and the steel arch at the present stage is mostly determined by experience.There is no clear analysis method for the influence of the initial position on the stability of the tunnel;2.There is no clear criterion for the impact of tunnel construction safety under different site environments and different construction methods;3.In the tunnel design,the self-stability of the surrounding rock should be fully considered,and at the same time,the surrounding rock is allowed to have a certain amount of deformation,but there is no quantitative representation of the control of the deformation;4.Different calculation models will affect the safety of the support structure,but at this stage many calculations and analysis are based on the analysis under the elastoplastic model,which may result in certain deviations between the calculation results and the actual results.Therefore,in-depth study of the post-peak characteristics of rock mass and different tunnel construction methods has important guiding significance for the excavation support and safety evaluation of tunnel surrounding rock.Based on the Hoek-Brown?H-B?strain softening model,the numerical simulation software is used to analyze the stability of underground structures under different conditions.The main contents are as follows:First,on the basis of previous studies,explore the damage mechanism of jointed rock mass.Based on the quantitative GSI surrounding rock rating system,the H-B strain softening model was studied to analyze the influence of different influencing factors on the softening parameter?^*.Then,based on the H-B damage criterion,the finite difference FLAC^3D software is used to compare and analyze the effects of the elastoplastic model and the strain softening model on the longitudinal displacement profiles?LDP?.At the same time,the surrounding rock parameters,buried depth and lateral pressure coefficient are analyzed the influence on the longitudinal displacement profiles and the displacement coefficient of surrounding rock.Secondly,a series of longitudinal deformation curves are obtained based on H-B strain softening model by FLAC^3D software.The quadratic regression orthogonal test is used to analyze the influence degree of each influencing factor on the displacement coefficient of surrounding rock.At the same time,the regression equation relating to the displacement coefficient of the surrounding rock of the tunnel and its influencing factors are obtained.And the method of using this formula to predict the initial point displacement of primary support is explained.Then,according to the convergence-constraining principle,the stability of the tunnel supporting structure and the deformation of surrounding rock under different constitutive models,different support timing and different excavation methods are compared and analyzed,and the rules are summarized.Finally,based on the H-B strain softening model,the finite difference FLAC³DD software is used to simulate the excavation construction of the separated independent two-lane tunnel.The influence of the surrounding rock deformation and its displacement release coefficient during the construction of the double-line tunnel is studied by analyzing the tunnel spacing,construction method and tunnel depth.At the sane time,the rules are summarized,and the suggestions for engineering practice are provided.