Numerical Simulation Study On Slope Reinforced Mechanism And Mechanical Response Of Seepage

The geogrid reinforced slope is one of the new composite structures in civil engineering. It has a series of characters, such as low cost, convenient construction, optimal land utilization and flexible structure. It has been applied widely in highway, water conservancy, railway and seaport etc., and obtained great economic and social performances. The Three Gorges Reservoir is one of the gretest engineering in China and World. The bank protecting system is an important challenging work. Taking it as the background, the interaction mechanism of soil and reinforced material has been studied, the unsteady seepage is calculated and slope stability with the seepage force is analysed. Based on the above analysis, the test engineering is simulated by the numerical methods. Analysing the variation of the displacement, stress, plastic failure fields and factor of safety in the the water level changing process, the failure mechanism of the reinforced slope in the process are studied. The reasonable evaluation of the protecting effect and bank slope stability is carried out. The main work in the thesis is as following:Study on the Reinforced mechanism and numerical simulation methods of geogrid-reinforced slope. The contact interface conditions are introduced in the control equations of the Lagrangian grid. The classical Coulomb's rule is adopted as the constitutive model of the interface tangential force. Then the weak formulation of the control equations considering the contact constraint conditions has been developed. Combined the Lagrange multiplier and penalty function methods, the augmented Lagrangian method is used to treat the contact constraint and solved the non-linear and non-smooth problems of the mechanical response perfectly. A finite element model has been applied for the test project of the reinforced slope and to study the mechanism of the interaction of the soil and reinforced material. The calculated results show that the contact friction forces on the surface of the slope are varied in the parabolic form. When the geogrid bears small tension force, the interface friction force is mainly located at the section near the sloping surface. As long as the tension force becomes large, the frictional force at the inner section of the geogrid will begin to play role and become the major region. The stability of the reinforced slope will increase greatly comparing with the non-reinforced one. The reinforced materials will insist the extension of the sliding plane behind the slope and ensure the stability of the slope. 2. Study on the numerical simulation methods of the seepage and slope stability. The mathematic model of the unsteady seepage is carried out and the calculation formulas are derived using the variational principle. The technique of deactivate and reactivate element is applied to simulate the free surface which are the most difficult problem in the unsteady seepage analysis. Based on the previous results, the disadvantages of the traditional slope stability analysis method considering the seepage force are indicated. An improved method by using seepage body force has been posposed to instead the peripheral water pressure. In this method the influences of the soil gravity and seepage direction are considered.3. Mechanical response analysis of the geogrid-reinforced slope in the Three Gorges Reservoir. Using the proposed theory and analysis methods the numerical simulation of the large test project in the Three Gorges area has been carried out. The variable procedures of the displacement and stress fields are simulated in the condition where the water level is dropped suddenly. The results show that in the process of the water level falling, the hydraulic gradient in the region of reinforced soil will increase quickly. The increase of the horizontal displacement is less obviously than the total displacement. The geogrid provides effective lateral restraint to the sloping surface. The failure zone will extend step by step and the plastic zone is mainly in the filled soil zone. The seepage and...