The Seepage Model Analysis And High Slope Stability Estimation Of Left Embankment In Jinping Stage One Hydropower Station

The seepage is commonly existed in rock mass, the hydraulic head is a key factor in bodily sliding-proof stability judgment. So we investigate the seep way of groundwater and the force on the rock mass aroused by the groundwater, in order to judge the bodily sliding-proof stability with rock mechanics. The conceptual models on seepage flow in the fractured rock mass can be classified as three basic types: equivalent continuum models, discrete fractured network models and conceptual frameworks.The discrete fractured network model is on the basis of truly distributing of fractured network. It indicates the defined distribution in permeability space with fractured rock mass's hydraulics parameter and geometry parameter. When only the permeability of fissure is taken into account, the flow model in fractured network system can be founded according to the actually geometry distribution of fissure and the discontinuity.In recent years, the 3D network computational simulating technique for random discontinuities develops and grows up rapidly, it can simulate random discontinuity such joints, fissure etc in rock mass, can construct the distributing state of random discontinuity in 3Dspace and supply the physics foundation for the researching to the problem of the seepage in fractured rock mass.The FEM has more difficult in disposing discontinuous models problems mentioned above due to it is displacement compatible element, so it will create great error. Interface stress element can cover the shortage in solving discontinuous models problems.The author concluded systemically the research history and actuality on seepage in fractured rocks in the paper. By connected with the truly example of Jinping stage one hydropower station on Yalong river in Sichuan province, the author has introduced the general situation of the engineering and the engineering geological condition, besides these, the author also has performed the following work on five aspects:1. On the basis of great geological investigation outdoors, the author has stated the attitude of discontinuous joints and size of traces in number 38 tunnel, which is on the left bank of dam site. By utilizing the 3D network computational simulating technique for random discontinuities, the author has founded the space construction, provided the porositystructure's physics background in rock mass for the research to rock mass hydraulics problem and got the distribution of jointed trace in 3D space.2. Basic theory of interface stress element method is systemically formulated, which include mathematics foundation, mechanical foundation, stress model, displacement model, dominant equation, formula, solution method of discontinuous models and simulation of discontinuity of interface stress element method.3. The utility of interface stress element in seepage flow is formulated, and the difference of head is assumed to be accumulated on interface, so establish discrete model with block element and interface stress element to discrete the seepage flow into platelet. ? when interaction of seepage flow and displacement fields is no consideration, it should calculate the displacement fields at first, then look at osmotic pressure as a kind of extra pressure and make stress analysis of structure. For joint network, the osmotic pressure usually operate on the top and bottom surface as dint and it will vertically operate on the joint surface. (2) when proceeding coupling analysis of two fields mentioned above, the seepage flow and displacement fields arrange the same mesh reign the calculation scope of displacement fields, because the calculation scope of seepage flow is larger than calculation scope of displacement fields. But beyond the reach of that district out of the scope, a mesh of seepage flow is only arranged. When proceeding the seepage flow, the block element material in mesh is used as equivalent continuum models, then adopt permeability tensor of anisotropy to modify by iterating because of influence of deformation. (3) In this paper, interface stress element method and 2D fractured network is used to process discontinuous models seepage problem. It is the first time to construct a program with interface stress element method, 3D network computational simulating technique for random discontinuous and rock mass hydraulics to get the seepage path and water head in the fractured rock mass, which is innovational theoretically. The program is efficient and the result is correct by which used in rock mass of left dam shoulder in Jinping stage one hydropower station and the result is correct. The interface stress element method can establish the seepage model with divided mode and it also can establish a modeconsistent with actual head of water. It can get seepage path of fractured network and distribute of head of water, which have important meaning to searching and stability judge of key blocks.4. An 3D—FEM analysis of high slope excavation in Left Abutment of Jinping stage one hydropower station is carried out with a program 3D-a, and stress and displacement of high slope is modeled in detail at spandrel groove and cable-crane platform of left abutment. (D The result of analysis shows that tensile stress zone exists at top of slope surface after excavation. The transform from high distance to the low distance become large one by one in order. The biggest deformation rebound of two sides is 14mm, the biggest deformation to slope outside is 5 mm, the biggest deformation rebound in the slope excavation is 6mm, the biggest deformation to slope outside is 3 mm. the rock mass deformation in the horizontal direction and vertical direction appears at the bottom of spandrel groove and the cable-crane platform;excavation of spandrel groove leads to unloading relaxation and deterioration of surface rock mass in the mountain No. 5, and the large block above the fault F42-9 will be a potential threat, all the above will be the focal point of slope support at excavating step by step.the biggest deformation rebound of two sides is 14mm, the biggest deformation to slope outside is 5 mm, the biggest deformation rebound in the slope excavation is 6mm, the biggest deformation to slope outside is 3 mm. (2) after excavation of spandrel groove, the tensile stress zone exists in each step the most deep of tensile stress zone is 7m;the biggest tensile stress is 0.2 MPa, which appears 1885m platform. The tensile stress magnitude is 0.1 MPa, its depth is 3~4m, which appears big area in upstream slope, the stress is distributed again in cable-crane platform, the biggest deformation rebound increase to 21mm, the biggest deformation to slope outside is 8 mm;the biggest deformation rebound from 1960m to 1885m with slope excavation is 30mm, the biggest deformation to slope outside is 17 mm, the biggest deformation rebound at upstream slope and downstream slope is 30~34mm;the biggest deformation rebound at bottom of spandrel groove is 41mm. After slope excavation of upstream slope and downstream slope, the displacement from upstream slope to downstream slope is 5—10mm,VIthe displacement from downstream slope to upstream slope is 8— 16mm.5. According to stability analysis of slope excavation above, supporting measures after slope excavation is carried out, include combination supporting measures of pre-stressed cable, the piles with pre-stressed anchor cables, anchorage hole and Drain to cut the water.