Study On Mechanics Behavior For Shield Originating On Surrounding Soil And Retaining Structure Of Construction

Shield originating occupies the proportion of space in the process of shield tunnel is very small, but it is one of the most dangerous section of construction. Research of shield originating security is particularly important. Based on the basic theory of classical mechanics, the article used finite element software ABAQUS to numerically simulate the shield originating process on the basis of summarizing a large number of research experience.The simulation results compared with actual construction cases monitoring results, so it could be used to verify the validity of the numerical simulation results.The finite element model of shield originating was established and the calculation results were analyzed. We can get the relationship the change of the stress and displacement in retaining structure、tunnel structure and surrounding rock with the expansion coefficient of grouting unit、the strength of soil 、the tunnel span and space effect. The concrete conclusion is as follows:(1) The greater the soil strength, its resistance strata disturbance ability is stronger and the formation damage is smaller. With the increase of soil strength, the surface subsidence 、displacement and stress of strata and segment will decreases. Shield disturbance radius decreases with the increase of soil strength in the silty clay.(2) New tunnel has of a greater influence on the change of displacement and stress in surrounding rock and existing structures. The smaller tunnel spacing, the more displacement and stress of segment changed under the influence of new tunnel. the displacement direction has changed from both sides of the direction by pointing to the left. The stress of vault and inverted arch increased so much, the hance by contrast. On the X axis and Y axis, the direction of displacement of surrounding rock has changed. On the Z axis, the displacement line changed from "single hump" to "double hump" shape. The in-situ stress distribution type of surrounding rock in vault has changed from "funnel" into "double funnel"; Scope of retaining structure affected by new tunnel are mainly distributed in the left corner. The stress of section in retaining structure above the hole showed a trend of decrease, the stress of section in that below the mouth of the cave in contrast.(3) Spatial effect is the main factors that different parts of segment structure has different stress distribution. The inverted arch and vault of segment show tensile state, the arch waist in compression state, the stress value is bigger; The stress value of wall corner is greater than the central.(4) If grouting pressure is set too small, formation damage is bigger and the surface subsidence is bigger. If it is set too large, it will lead to ground surface uplift. Through the model calculation results compared with the actual situation, the reasonable expansion coefficient value is 1. E- 04.By comparing the change rule of segment convergence and surface settlement curve in the measured and calculated results, we can know that the calculation model can truly reflect the actual situation of the scene, the result of calculation is reliable...