Research On Earth Pressure For Shield Tunnel Lining

With large-scale application of shield tunnel in our country, it's urgent to draft out a standard for shield tunnel tunneling. Because of lack of the standard for shield tunnel, the design of shield tunnel lining is blind, which doesn't take into account the reality of shield engineering in China. Without the guidance of the standard for shield tunnel, the results of shield tunnel lining lead to waste or haphazard of design. The results are not benefic to strategic implement of subway project of vital and lasting importance, can avoid haphazard design of shield lining. So the study for the design of shield lining is very valuable for academy and application.In the view of the key problem for design of shield lining, the thesis has laid an emphasis on the earth pressure, from the numeric analysis for earth pressure, in-situ monitoring for segment working performance to back analysis for segment earth pressure. The main works are following:1. In order to back analyze the earth pressure more accurately, the thesis has studied the stiffness of segment joint and found the bilinear model for joint stiffness on the basis of the test of pad and the result of the analysis of joint analysis. The bilinear model for the stiffness of segment joint is also applicable to determine the stiffness of segment joint without pad.2. Based on the model of joint stiffness, the thesis has found the method to determining the effective bending stiffness of segment lining. In the view of the general lining segment pattern in China, a empirical formula to calculate the effective bending stiffness is also present. Considering the bending stiffness of segment joint and the shearing stiffness of lining joint, the thesis has brought forward the method to calculating the segment. Finally, the thesis analyzes the factors affecting the stiffness of segment joint, which is benefic to select the details of segment joint.3. On the basis of the two monitoring cross-section in Nanjing city and the three monitoring cross-section in Guangzhou city, the thesis has found the back analytic method to earth pressure on segment and finished computing programming.4. On the basis of the result of back analysis of earth pressure for the monitoring cross-section, the thesis has studied the method to determining vertical pressure, and the span of horizontal pressure on shield lining.The calculation of the vertical pressure on the segment needs consider the geological conditions, and appropriately evaluate the arching of soil. When the depth of tunnel is probably single diameter of tunnel, the vertical pressure is dead load of overburden soil. When the depth of tunnel is twifold diameter of tunnel and the geological conditions are rigid, the vertical pressure is the loose pressure of overburden soil. When the depth of tunnel is twifold diameter of tunnel and the geological conditions are ordinary, the vertical pressure is the partly loose pressure of overburden soil.According to the results of back analysis, the coefficient of horizontal pressure is the standstill coefficient of horizontal pressure in clay soil; the coefficient of horizontal pressure is between the standstillcoefficient and active coefficient of horizontal pressure in weathered rock; the coefficient of horizontal pressure is near the active coefficient of horizontal pressure in sand soil.5. Optimum analysis for the back-ward earth pressure has been studied, the best monitoring scheme of shield lining and the worst monitoring scheme of shield lining has also been acquired.