Experimental Study Of Soil Conditioning For Epb Shield Tunnel In Water-rich Composite Stratum

The rapid economic development has brought about a sharp increase in the population of the city,the number of urban populations is increasing,and the demand for large-capacity rapid transportation in super-large cities and large cities is increasing.The shield method is widely used because of its reasonable price,high mechanization degree and fast construction speed.Whether the conditioning of soil is reasonable in the process of shield construction has great influence on shield tunneling.Therefore,in order to ensure the efficiency and safety of urban subway construction,more research needs to be done of soil conditioning for earth pressure balance tunnel.The thesis is based on the tunnel between Renmin Park Station and Ding Highway North Station of Nanchang Metro Line 4,and takes the shield tunnel method to cross the water-rich composite stratum as the research object,and adopts the method of data collection,field investigation,theoretical analysis and numerical simulation.The necessity of soil conditioning,reasonable parameters of soil conditioning and shield tunneling parameters of shield tunneling method in water-rich composite stratum are studied.The main research contents and results are as follows:(1)According to the geological characteristics of the water-rich composite strata in Nanchang,the research on the selection of the shield machine for the composite stratum was carried out from the aspects of formation permeability and particle gradation,and the type of shield machine suitable for the geological conditions was determined.Mineral composition analysis and gravel grading curve analysis showed the necessity of soil conditioning.(2)By producing foam with a self-made foam generating system and preparing bentonite mud with different proportions,the variation law of foam performance with the concentration of foaming agent solution and the change law of bentonite mud performance with mixing ratio were obtained.The laboratory experiment of soil conditioning was carried out,and the reasonable addition ratio of saturated gravel sand and moderately weathered argillaceous siltstone modifier was obtained.(3)Based on the reasonable addition ratio of the modifier obtained from the indoor soil conditioning experiment,the research on the application of the shield tunneling model and the field application research was carried out,and the driving parameters and modifier parameters were statistically analyzed,which showed the applicability of the indoor soil conditioning research results.(4)Based on the ABAQUS extended finite element model,the EPB full cutterhead driving model in subway tunnel with water-rich composite stratum was established,and the Mises stress distribution of various models and the variation law of the maximum value of Mises stress were statistically analyzed.The co MParative analysis verifies the correctness of the full cutterhead driving model.