Fluid-solid Coupling Analysis Of Surface Settlement In The Whole Process Of Shield Construction

Shield method is widely used in urban tunnel construction because of its advantages in construction,but shield excavation will inevitably affect the deformation of surrounding soil.The main cause of deformation is the formation loss and soil re-consolidation of disturbed caused by shield.When the deformation of the local layer beyond a certain range will endanger the surrounding building(structure)and underground pipelines indirectly,resulting in greater economic losses.Especially the geological conditions of Taiyuan are water-rich and weak strata,the disturbance of shield construction is accompanied by fluid-solid coupling effect,and relatively lack of construction experience.Therefore,it is great significance to analyze the soil deformation caused by shield construction,using the principle of soil and water fluid-solid coupling.Taking Taiyuan Subway Nanneihuan station to Shuangtaxi station section as an engineering background,and the law of ground subsidence caused by shield tunneling parameters is analyzed by means of theoretical analysis,orthogonal test and numerical simulation.In the process of analysis,the influence of fluid-solid coupling is fully taken into account,and the orthogonal test method is used to provide a set of relatively perfect parameters of shield propulsion combination for Taiyuan Metro.At the same time,the disturbance to soil in the whole process of shield machine construction from the initial surface of the model to the complete stripping out of the rigid shell is studied systematically under this parameter,and the measures to control the surface settlement are put forward.The main contents of this paper are as follows:(1)This paper summarizes the research methods used in shield construction at home and abroad,expounds the mechanism and disturbance range of soil deformation caused by shield construction in detail,and deduces the analytical formula of maximum ground settlement caused by non-uniform grouting pressure considering gravity.Furthermore,it shows the importance of this factor.The existing numerical simulation factors are improved,that is,considering the shell length of shield machine,the supporting pressure of excavation surface,the non-uniform distribution of grouting pressure on the top and lower,the fluid-solid coupling,etc.,the calculation model which is more in line with the actual engineering is established.The necessity of considering the fluid-solid coupling model and the correctness of the numerical simulation are proved by comparing and analyzing the measured data of a certain interval in Ningbo.(2)By analyzing the law of the factors affecting the surface settlement and considering various construction factors synthetically,the calculation formula of surface settlement is fitted out by software and the combination form of the better parameters is found by the method of orthogonal test.It is concluded that the main influencing factor of surface settlement is grouting amount.(3)Based on the orthogonal test,the optimal combination parameters are obtained.Through the establishment of fluid-solid coupling model,when the number of excavated rings is 6,12,18,24 and 26,the distribution of displacement field,stress field,seepage field and plastic zone are observed.The influence of shield propulsion on soil disturbance is analyzed,in order to master the development law of the whole process of surface settlement and to prove the rationality of the selected parameters.