The Evolution Of Permeability And Analysis Of Seepage Field In High-Steep Slope Based On Microseismic Monitoring

The instability problem about high-steep slope of large-scale hydropower engineering caused huge losses to human production and life safety. However, the seepage is one of the critical factors that affect the stability of high-steep slope. Some rock mass damaged caused by construction disturbance, whose permeability changed significantly, and then the seepage field altered on high-steep slope. Therefore, more accurate permeability of rock mass can be more realistic to simulate the slope seepage field, which provides a more effective reference for the analysis of slope stability. So the study about evolution of permeability and seepage field for rock mass has important practical significance under construction disturbance. Based on the microseismic monitoring data from Jinping ? left bank slope on construction process, mainly done the following work in this paper:(1) Based on the microseismic monitoring data from left bank slope in the course of construction, microseismic events can be show on quasi-three-dimensional model of II,-II, cross section in the form of microseismic energy by coordinate transformation. Then the evolution law of spatial and temporal distribution of microseismic energy could be analysed with the construction disturbance. Results show that agglomeration region of microseismic activity and construction conditions have a strong correlation, meanwhile,microseismic events mainly distributed around discontinuous structure surface such as major faults or lamprophyer X. In the end there is a study on the earthquake mechanism of microseismic events on the left bank slope. And we find that failure by shear is the main damage in rock mass on the left bank slope. The results lay a theoretical foundation for analysing the evolution of rock permeability based on microseismic monitoring.(2) Two methods to determine the permeability of rock mass is proposed based on microseismic monitoring data. They are the theoretical method based on the cubic law and the empirical method based on microseismic energy. Through comparing these two methods, the final decision is to choose the experience method based on microseismic energy, then protract the spatial distribution map of permeability coefficient increment. After protracting the space distribution of rock permeability coefficient increment of each construction stage, spatial and temporal evolution law of seepage coefficient increment of slope rock mass can be analysed. Results show that the variation of permeability coefficient of slope rock mass is mainly affected by construction condition and discontinuous structure surface(major faults or lamprophyer X). The slope excavation make the permeability coefficient of the slope shallow rock mass change significantly, but these construction disturbance like excavation of dam foundation or grouting for weak rock mass in slope make the permeability coefficient of rock mass near the discontinuity in slope change significantly.(3)After established quasi-three-dimensional numerical model of ?1-? 1 cross section, divided each block emerging microseismic events into a new group, and assigned it to the permeability coefficient increment, the new permeability coefficient of each group can be obtained. And then simulate the seepage field of the slope under the condition of water level fluctuation,meanwhile, analyse the transient process of the seepage field. Analysis results show that:Faults and other geological structures control the migration of the seepage field and the distribution of pore pressure. Lamprophyre X, which is water resisting rock mass,has a barrier effect to the slope seepage field and the distribution of pore water pressure. The slope seepage field and the distribution of pore pressure on consideration of microseismic events have obvious difference with that on no consideration of microseismic events. According to the time, space and intensity of microseismic activity, the slope seepage field can be more accurate monitoring, and the seepage control measures can be reasonable optimization.In brief, this paper builds up a method about reflecting permeability evolution of slope rock mass based on microseismic monitoring data, which is an innovative attempt in this paper. The results explore a preliminary approach for analyzing permeability and seepage field based on microseismic monitoring data in order to gradually validate, improve and develop this method in engineering practice.