Study On Coupled Solid-fluid Problem Of Shield Tunnel During Construction Period

Construction of shield tunnel generally is closely related to ground water. Its location is usually located in the rivers, lakes, sea bottom where exist the complex engineering geology and hydrogeology environment. Through the strata both soft ground and hard fractured rock, shield tunnel will inevitably encounter the problem of coupled solid-fluid during tunnel construction period. For shield tunnel engineering, the load value is the design and construction of key parameter, the coupling effect on surrounding rock and groundwater will bring the distribution of load changed significantly. Therefore, the problem of coupled solid-fluid during construction period is a complex and important issue in the research on shied tunnel with ground water.According to the National Natural Science Foundation of China project'study on solid-fluid coupling of large-scale shield tunnel during construction period', cooperating the drain tunnel project crossing Yangtze River in the downtown of Chongqing city and shield section tunnel in Chendu metro line1as the engineering background, by means of theoretical analysis, numerical simulation, in-situ testing, laboratory tests and other methods considering the problems of coupled solid-fluid caused by shield tunnel construction and slurry shield machine simulation test, the internal forces of segments lining and reliability are studied systematically during construction period of the different soil layers. In order to make up the limitation about theoretical analysis and numerical calculation, a set of slurry shield simulation test system is developed, as a supplementary means of other studies. The main results are as follows:1. For the problem about coupled solid-fluid during construction period, using rock mechanics, seepage mechanics and elastic-plastic theory, the calculation formulas of seepage field and stress field for surrounding rock and structure is deduced. Through analyzing different plasticity yield criterion, Drucker-Prager criterion is selected as the basis of analytic method for calculating the internal force of surrounding rock and the lining. In light of the different soil and rock mechanical properties, the formula of the permeability coefficient and the corresponding stress furthermore, analytical solution of shield tunnel lining internal forces is obtained by coupled solid-fluid theory.2. Based on coupling mechanism between seepage field and stress field, using finite element software, for the surrounding rock that consists mainly of rock strata, combined with high pressure water shield tunnel of the drain tunnel project crossing Yangtze River in the downtown of Chongqing city, this paper carried out the construction of tunnel surrounding rock and the main structure of the seepage field and stress field analysis of two-dimensional coupled solid-fluid. The effects on surrounding rock and the main structure of coupled solid-fluid problems under high water pressure and under different pressure conditions during tunneling period were studied respectively, the research gives the water pressure having effect on the segment of lining structure, and the result is testified by field test data. For the ground consisting of mainly sand and gravel with rich groundwater of the shield interval tunnel in Chengdu metro line1, the two-dimensional and three-dimensional coupled solid-fluid calculation are carried out, the internal force distribution of lining structure and the impact on the surrounding structure caused by excavation the tunneling are studied.3. This paper put forward a method which combining FEM and interval solution method for getting the tunnel lining internal forces. A single random variable internal force of the impact of the level of the tunnel lining is analyzed. Parameters of random variables are treated by the most unfavoured combination. Finite element program is called to solve the interval values of lining internal force.4. In order to solve the tunneling control of slurry shield machine and mechanism of slurry balanced, a physics simulation device is developed that it can realize the simulation of the real groundwater pressure. On the basis of complete functional verification-based simulation of slurry shield tunneling process of testing, analysis of the shield tunneling having effects on the surface, as a result, the paper draws conclusions regular rules of slurry shield testing.Through the membrane formation mechanism of mud, the test that filter-cake for a fundamental impact on the formation permeability is carried out. Based on above, the simulation soil is manufactured cooperating the sand and gravel parameters in Chengdu characteristics. The slurry material is determined by test methods, and the formation of filter-cake simulation test film is completed. The states corresponding different strata is revealed.With the rapid development of transport, the growing shield tunnel, the results about coupled solid-fluid has important significance for the protection of shield tunnel construction safety. The slurry shield micro simulation test system is not only to study the problems of slurry shield construction for all types of conditions, but also to provide an important reference value for the construction of shield tunnel and design of machines.