Study On Key Construction Techniques Of Tunnel With Miscellaneous Filling In Complex Urban Environment

With the development of modern urban underground rail traffic,more and more urban tunnels will be built in the miscellaneous soil.Miscellaneous fill has the characteristics of low bearing capacity,high compressibility,collapsibility and poor uniformity,and often in under consolidation state,its engineering properties is a bit different from the normal consolidation soil's.For the theoretical and technical difficulties in the construction of shallow buried tunnel construction,the present paper studied the engineering characteristics,the constitutive model,the tunnel excavation method of miscellaneous fill and analyzed the construction mechanics behavior of miscellaneous fill tunnel,structural safety under blasting vibration by the comprehensive utilization of experiment and theoretical analysis,numerical simulation and field measurement.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 present paper analyzed the general nature of miscellaneous fill.Based on the modified cam-clay model,the paper established the elasto-plastic constitutive model of miscellaneous fill which is in under consolidation state.The various mechanical parameters of the miscellaneous fill are obtained through laboratory experiments,which are used in numerical simulation.2.With analysis of the construction method of shallow mining tunnel in the miscellaneous fill layer,reasonable excavation method of 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 tunnel construction method are put forward.3.According to the requirements of related design and blasting,in the consideration of geological situation and characteristics of blasting construction in section tunnel which is from the central garden to the western garden.In order to select rational blasting parameters and blasting way,the present paper studied the cutting hole's influence on tunnel initial support,excavating face and nearby buildings in the process of blasting;In order to choose the reasonable blasting sequence and guide the engineering construction,this paper researched the different blasting sequence's influence on tunnel construction in large-span tunnel excavation by steps.4.By using the method of field test,this paper researched the surrounding rock stress and deformation rule of the shallow tunnel which is built in the miscellaneous fill,and mechanical properties and load conversion law of retaining structure.The present paper analyzed the change law of monitoring section crown's pre-displacement and convergence displacement and the influence scope of surrounding rocks in the process of tunnel face advancing of miscellaneous fill tunnel.;In order to evaluate the safety of retaining structure,the paper analyzed the distribution of the surrounding rock stress and contacting pressure.