Probe On Mechanism Of Seepage Evolution For Rock Mass In High-steep Slope

With the construction of large-scale water conservancy and hydropower project, the instability of slope failure has become the focus of public attention. The seepage is the main reason for the destruction and instability of hydropower projects. rock mass damage caused by excavation will locally induce obvious change of permeability coefficient in the slope, and Permeability is one of the important parameters for seepage control of the high hydropower slope, which accurate or not directly related to the reliability of the results of seepage analysis.Thus, the studies of permeability coefficient weakened and permeability characteristics changed of rock slope cased by eacavation unloading, which is one of the important issues discussed by seepage mechanics and rock engineering, and is important for the stability assessment of high steep slope and the safe operation of hydropower projects. Dagangshan right bank slope as the research object. In this paper. Based on the microseismic results from Dagangshan right bank slope excavation, the evolution of released microseismic energy is analyzed, the spatial distribution of permeability change amount is studied, and analyze the variation of seepage field of the right bank slope under the conditions of reservoir water level fluctuation. Mainly done the following work in this paper:(1) Based on the microseismic results from the LPV-LPV cross section of Dagangshan right bank slope excavation, the evolution of released microseismic energy is analyzed and the spatial distribution of permeability change amount is studied. The results showed that The main factors which induced microseismic events of the slope is excavation unloading activity,and the variation of microseismic events changes with the construction activities carried out and stop. The extent of regional monthly cumulative microseismic released energy, whose spatial distribution of different regions in contour map can be quantitatively identified,the rock mass damage deeply underneath slope and adverse geological structure of the surfer location and direction is delineated. The microseismic released energy during rock mass damage evolution turns to be intense along deteriorated geological stripes as well as excavation unloading induced fissure zones. It follows the accumulation, releaseand transfer regularity of energy.(2) Based on the size of the energy released microseismic results from the LPV-LPV cross section of Dagangshan right bank slope excavation, Through studying the relationship between microseismic energy changes and rock permeability, it shows that the released microseismic energy due to rock damage is consistent with the extent of rock permeability change and get a space distribution of permeability changes of different spatial locations within the slope caused by excavation unloading, in order to mark the penetration factor of the slope after the excavation.(3) Establishment of a two-dimensional LPV-LPV cross section model of Dagangshan right bank slope through CAD, then geological model was generated in ANSYS and unit meshed, finally,the model is imported FLAC3D to simulate.In the analysis variation of the pore water pressure contour map and flow vector of slope under the conditions of the water level suddenly lift. The results show that reservoir water level fluctuation have a significant impact to changes of pore water pressure of the slope, especially to the upper body of rock slope. The contours of Pore water pressure distribution within the slope are differences under the same water level, but different conditions. Stable pore water pressure contours are more gentle and parallel to its base under conditions of rising water level. Stable pore water pressure contours has convex trend under conditions of reservoir drawdown. When a sudden change in water level, whether it is to store water or drawdown, the seepage velocity in the rock of upper slope is larger than deeper part and base of the slope, the change of pore water pressure in the slope body has hysteresis phenomenon. The existing of adversely geological surface has great influence on the change of seepage field in the slope, such as the unloading fractured zone.