| With the continuous improvement of tunnel construction in China,the most typical example is the rapid development of transportation construction in the central and western regions of China,and a number of important trunk lines connecting the East and the West have also been put on the agenda.In the process of tunnel construction,it often passes through complex geological conditions.As one of the common adverse geology,weak inter layer has a great impact on the stability of tunnel surrounding rock.After the tunnel is excavated,it often causes large deformation of surrounding rock and yield failure of supporting structure.Therefore,it is necessary to further study the tunnel with weak interlayer systematically.Based on the research of many scholars,this paper analyzes the research status of weak intercalation tunnel,and studies and discusses the influence of weak intercalation on the stability of tunnel surrounding rock,the physical model test of rock tunnel with weak intercalation and the spatial effect of excavation and support of rock tunnel with weak intercalation:(1)Combined with many practical engineering cases and literatures,this paper expounds the classification,physicochemical properties,engineering characteristics of weak intercalation and the supporting methods of this kind of tunnel,and sums up several factors that have great influence on the stability of tunnel surrounding rock and the stress of supporting structure: the thickness of weak intercalation,the dip angle of weak intercalation,the position of weak intercalation and the strike of weak intercalation.(2)Using FLAC 3D software established a two-dimensional numerical model of tunnel with weak interlayer under the condition of no support.The influence law of different occurrence(thickness,inclination and position change)of weak interlayer on the displacement,stress and plasticity of surrounding rock is studied.The results show that the influence degree of soft interlayer inclination is the greatest when the inclination angle of soft interlayer is within 25°～45° range;the greater the thickness of soft interlayer will affect the stability of surrounding rock The more influence degree is,the more soft interlayer is close to the excavation contour of the cavern,the greater the influence degree of the surrounding rock stability.(3)Indoor physical model experiment,by similarity theory to establish a reasonable similarity relation,and through a series of similar experiments conform to the requirements of the surrounding rock similar material proportion,weak interlayer and lining,studied with weak inter layer tunnel excavation on the internal forces of the lining structure stress and the influence law of distribution characteristics,from the experiment the findings: The values of internal force and stress on the lining of a fixed section increase with the excavation of the tunnel.The first principal stress is the largest at the waist of the left arch of the tunnel,and the third principal stress is the largest at the vault.The maximum internal forces of the lining are all near the weak inter layer.(4)Using FLAC 3D software established a three-dimensional numerical model of rock tunnel with weak inter layer to simulate the actual excavation process of tunnel.It mainly analyzes the distribution of surrounding rock stress,surrounding rock displacement and surrounding rock plastic zone,as well as the distribution of stress and internal force of supporting structure with tunnel excavation.Through numerical simulation,it is found that the stress of surrounding rock and supporting structure on a certain section changes with tunnel excavation The larger the distance from the face,the slower the increase. |
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