| With the development of social economy and the continuation of the western development strategy,the construction of state key projects such as the transmission of electricity from the west to the east,continues to move forward.The rock and soil mass are excavated inevitably,and hundreds of meters high slopes are created.It is of great significance to study the stability of high slope for the safety of engineering construction and reaping the full benefits of engineering after construction.The left spandrel groove slope of Yangfanggou hydropower station of Yalong river is taken as the study case.The first-hand data are obtained through geological sketch at project site.Lithology and rock mass structural characteristics of the left spandrel groove slope were studied.The location,mode and scope of deformation and failure of the left spandrel groove slope are analyzed.Combined with numerical simulation,as well as the analysis method of limit equilibrium and the block theory,the stability of the left spandrel groove slope is analyzed and evaluated.Based on the results of stability evaluation,targeted support measures are put forward.The main research contents and results of this paper follow:（1）Through actual measurement at project site,the structure of rock mass of the left spandrel groove slope are systematically studied.Discontinuities of rock mass of the slope are classified.The dominant orientation discontinuities of engineering slope are found out,and the main controlling discontinuities of the engineering slope are obtained.（2）According to the categorization of rock mass structure of the slope,the rock mass quality of the slope is further classified with the help of the results of rock mass classification in the early stage.Combined with the laboratory test and field test in the construction period,the physical and mechanical parameters for the stability calculation of the slope are finally obtained.（3）Based on the observation and analysis of the phenomenon of deformation and failure of the slope,failure mechanism includes sliding failure by single planar,sliding failure by double planars,step-slip failure as well as wedge sliding failure.On the basis of different deformation failure modes and development and distribution of potential unstable blocks,the excavation of the slope is divided into A,B,C,D four risk areas.（4）Following analysis method from whole to part,stability of the left spandrel groove slope is studied systematicly:（1）By using method of 3 dimensional discrete element code,the deformation characteristics of the left spandrel groove slope are analyzed.The results show that the whole excavated slope is stable and there is no large-scale displacement.（2）Based on borehole exploration and sound wave testing,the distribution characteristic of altered rock by f27 fault in dam foundation is found out and its influence on stability for the slope is analyzed.（3）Software called Slide based on theory of limit equilibrium is used to calculate factor of stability of blocks whose failure mechanism is sliding failure by single planar,sliding failure by double planars or step-slip failure.Software called Swedge based on block theory was used to calculate factor of stability of wedge blocks.（5）According to the analysis and evaluation results of stability of the slope,the corresponding treatment and supporting measures are proposed:（1）For the f27 fault alteration zone at dam foundation,the main treatment measure is"digging chute+backfilling concrete+reinforced grouting".After treatment,the dam foundation meets the requirements.（2）After the blocks which don’t meet the safety requirements completing the supporting measures,recalculation results show that the blocks are in a stable state and has a large safety margin under different working conditions.Therefore,the slope meets the stability requirements during construction period and operation period.At the same time,the monitoring data show that the deformation of the slope has been effectively controlled. |
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