Research And Analysis On Calculation Of Shallow Thickness Covering Shield Tunnel Under Inland River

Due to the continuous development of China’s economy, the need of city tunnel construction is becoming more and more significant, tunnel construction has become an important topic in current research, China’s complicated geographical environment constantly development of tunnel technology put forward higher requirements. Shield tunneling under the inland river, as the tunnel slope is too large will generally lead to overburden thickness is small, the larger the shallow overburden soil disturbance by construction, improper handling may cause engineering accident is not necessary, therefore the research of the shallow soil is the key to solve the engineering problem. In this paper, based on Chengjiang road in Jiangyin City, the two phase of the project, a large number of relevant literatures, the discussion and Research on Mechanism of shield tunnel passing through the inland shallow soil, and the tunneling process was simulated by the finite element analysis software Abaqus, and with the actual engineering are compared, is to put forward the operation of upper soil reinforcement measures. The specific work is as follows:First of all, to explore the upper shallow overburden tunnel by shield construction disturbance mechanism and its failure mechanism, to verify the four stages of soil disturbance caused by based on the previous studies, the soft soil layer in different stages of construction disturbance to soil ratio.Secondly. Engineering tunnel in shallow soil divided into "static float" and "dynamic floating". The thickness of covering soil shallow layer on the existing calculation formula calculation only considered the stress state of soil under static state after construction, does not take into account the grouting pressure of overlying soil disturbance during the construction, in practical engineering is dangerous, may cause engineering accident is not necessary. In this paper, based on the formula of soil by increasing grouting pressure and the calculation formula improved in the existing minimum overburden thickness calculation, discussion, segment diameter, grouting, grouting pressure on severe and improved the calculation formula and the influence of the existing formula, and demonstrates the rationality.In addition, through the finite element analysis software based on the stiffness transfer principles, simulation of tunnel excavation process, calculate the stress and deformation distribution in the process of tunnel excavation, to explore the different thickness of covering soil tunnel excavation influence on the upper cover soil, different soil thickness under the open cut tunnel stress and deformation distribution, the minimum thickness of covering soil of this project, and compared with the theoretical calculation.Finally, the construction technology of reinforcement of shallow soil, and puts forward the technical measures for the reinforcement project of the shallow soil, and has been verified in practice.