Study On Surrounding Rock Mass Stability And Mechanical Behavior Of Shallow Mining Tunnel With Miscellaneous Filling

In the urban construction of underground rail transit,it is inevitable to encounter problem of shallow buried excavation,miscellaneous fill soil and large section excavation.Compared to the general soil,the miscellaneous fill soil has the characteristics of non uniformity,self weight compaction,collapsible,low strength and high compressibility,which makes the excavation of the tunnel has a lot of uncertainty.For the theoretical and technical difficulties in the construction of shallow buried tunnel construction,the comprehensive utilization of theoretical analysis,numerical simulation and field test method,is used to the systematic analysis of the construction mechanics behavior of miscellaneous fill tunnel.Through the study on engineering characteristics of miscellaneous fill,mechanical properties,loading,tunnel pre reinforcement measures and large section excavation method,thus formed a set of miscellaneous fill the reasonable theoretical system and scientific construction method.At the same time,the results of the study will be a positive feedback to the actual construction in the field,and be the scientific and effective guidance of the construction tunnel.The main research results are as follows:1.Through the investigation of a large number of documents and geological survey data,the author summarizes the macro structure characteristics,distribution characteristics,the forming law and mechanical properties of the artificial miscellaneous fill soil layer.After the analysis of the general nature of miscellaneous fill,there is a detailed research on the project of Central Park station,which is based on the project of Chongqing rail transit line ten,provides the theoretical basis for the following research.2.Through the study of the influence of miscellaneous fill on the load factor,the stress state of surrounding rock after excavation is analyzed,and the critical buried depth of the pressure arch in the miscellaneous fill soil layer was proved.Then the load calculation formula is proposed for the miscellaneous fill soil layer by comparing and analyzing the commonly used load calculation formula,and the comparison with the field test data proves that the formula is scientific and reasonable.3.Based on the analysis of the deformation characteristics and deformation mechanism of the shallow buried tunnel,the reasonable pre reinforcement measures are put forward,and the different measures with different measures are compared and analyzed,finally,the optimization measures are put forward.4.With analysis of the construction method of large section shallow mining tunnel in the miscellaneous fill layer,reasonable excavation method of large section tunnel construction is proposed,through to the surrounding rock displacement and internal force of lining as the index,combined with field test data,the applicability of different excavation method was studied,summarize and optimization suggestions the suitable for shallow buried excavation of miscellaneous fill of large section tunnel construction method are put forward.