| Huaping tunnel is the unique through the Xigeda strata, also the only highway tunnel in all Xigeda strata. Research on the stability of surrounding rock of Huaping tunnel can not only provide references for tunnels, constructing and designing, the research results can also be applied to other highway tunnel crossing the Xigeda strata.Therefore, it is necessary to analyze and study on the Huaping tunnel.This paper taking Huaping tunnel as the research object, firstly by collecting data, fielding investigation and laboratorying soil test, mastered the engineering geological background of the tunnel, and then carried out the research on centrifugal model test on the stability of surrounding rock of Xigeda strata tunnel. The subject with model test method, using centrifugal force instead of mountain stress, simulating possible tunnel deformation and geological diseases after tunnel excavation.Three groups of contrast test were conducted to explore the influence of different geological conditions of tunnel surrounding rock deformation and failure.In order to take measures in advance,The test by setting observation point, analyzing of strain data curve and data interpolation, study the influence of different geological conditions supporting measures on the stability of surrounding rock, and then sum up surrounding rockmass deformation, failure to predict tunnel deformation condition and possible geological diseases, provide theoretical support for adaptation measures in advance.The main research contents and results are as follows:(1) Centrifugal force simulating mountain gravity stress is attached to the model surrounding rockmass, which destroyed the original stress balance of surrounding rock, resulting in the surrounding rock stress redistribution, and its forms a new stress state, producing expansion deformation of surrounding rock.(2) Model of tunnel surrounding rock gathered a lot of energy, showing a trend of inward extruding; The closer to the cave walls the more energy concentrated. Reach its maximum around cavity. The energy is most concentrated on Arch tunnel wall, where the strain difference is largest.(3) The different effect of principal stress makes the vault show the concentration of tensile stress, and the sidewall show the concentration of tangential compressive stress. The release of the surrounding rock stress makes each particle of surrounding rock deformate to the interior of the hole. When the vault is greater than the tensile strength of surrounding rock stress, its will produce tensile fracture cave phenomenon.(4) Due to the tunnel wall rock stress concentrated, when the structural plane is weak, the development of tunnel surrounding rock is conducive to the stability of the surrounding rock, and the surrounding rock is prone to collapse.Especially in the fault zone with surrounding rock structure plane tending to outside the constraint, the surrounding rock is easy constrainting along the structure for the slump. Surrounding rock deformation and failure type is belongs to structural plane control type.(5) Anchor reinforcement of surrounding rock makes its integrity enhanced, interlayer frictional resistance increased, the tensile strength increased, thereby increasing the stability of surrounding rock, decreasing the size of plastic zone in surrounding rock strain. The anchor parameters are advisable to taking the length of 4.5meters, the spacing of 0.75 centimeters.(6)The range of surrounding rock of Huaping tunnel is 2 times semidiameter of the tunnel hole. More than 2 times radius, the surrounding rock strain is small.When the spacing is 2 times radius, there is no significant interaction between surrounding rock.(7) Because the steel arch shelf support can have effect of annular closed, which can avoid to drop the arch such as arch instability phenomenon. Therefore, in construction engineering, we recommend steel arch support surrounding rock. According to the results of the impellers of surrounding rock of experiment,the steel arch spacing shall be 0.5 meters advisable. |
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