| Rumei Hydropower Station is located in the upper reaches of Lancang River.And Lancang River,with the maximum annual discharge of about 676 m3/s,has ideal construction conditions for hydropower projects.However,the dam site area of Rumei Hydropower Station planned to be built is not only very complicated in geological structure,but also very serious in unloading of slope rock mass.In addition,the variation of seepage field may affect the slope stability under the condition of spillway atomization.In this paper,the influence of atomization rain on slope stability and the change law of slope stability in the process of flood discharge atomization are studied,which has certain reference significance for the prediction and prevention of slope instability caused by flood discharge atomization.From the field survey results,the following aspects are obtained: the rock mass of the spillway slope is strongly weathered,and the unloading phenomenon is also serious.There are a large number of collapse deposits,which are more in the slope toe and the gentle slope area of the bank slope.With the effect of flood discharge atomization and taking into account the above adverse conditions,the hydrogeological conditions along the bank will further change significantly,resulting in a corresponding strong change in the stability of the slope.In this paper,the slope of the discharge outlet of Rumei Hydropower Station in Tibet is taken as the object.Following the idea of field investigation,engineering geological condition analysis,deformation mechanism analysis,atomization rain slope seepage field,stress field analysis and stability quantitative evaluation,the influence of atomization rain on slope stability is analyzed by using numerical simulation method.Then the following research results are obtained:(1)The structural plane of the slope at the outlet is graded.Through field investigation,it is found that there are grade III,grade IV and grade V structural planes on the slope of the discharge outlet.Furthermore,the development characteristics of structural planes are analyzed in detail,and the dominant occurrence of various structural planes is obtained.(2)Based on the BQ method of rock mass quality classification,the rock mass quality grades of the outlet slope are divided into four categories: grade I,grade II,grade III and grade IV.(3)The exposure of various structural planes in the adit is as follows: the average connectivity rate of rock mass discontinuity is 36.3% by using the window method,which has certain reference value for the reduction calculation of rock mass strength parameters of discharge outlet slope of Rumei Hydropower Station.(4)Based on the drilling water pressure test,it studies the permeability characteristics of rock mass in the study area.Then,according to the permeability grade,the rock mass of the outlet slope is divided into following three types: micro permeability,weak permeability and medium permeability.Moreover,the distribution law is further analyzed.(5)The seep calculation software is also used to calculate the seepage of the slope under the circumstance of atomization rain,and the variation characteristics of the seepage line and pore water pressure contour of the slope under various working conditions are obtained.Furthermore,the influence of atomization rain on the seepage field of the outlet slope is explored.(6)On the basis of the analysis of the structural characteristics of the slope rock mass,the potential sliding surfaces before and after the excavation are further analyzed.Besides,the stability of the slope before and after excavation and under different working conditions is calculated.It is found that the stability of the slope decreases significantly during the atomization rain process.When the atomization rain stopped,the stability increased.The influence of atomization rain on the stability of the slope after excavation is greater than that of the natural slope,which has been in the state of instability.(7)The stability of natural slope and excavation slope is calculated by threedimensional numerical simulation method,and the influence of atomization rain on slope is considered.Also,the slope stability is analyzed respectively,and the overall stability of excavation slope under support condition is evaluated.Then it is found that the stability of the slope after support can be basically stable under the condition of atomization rain,and it is suggested that the strength of the support should be increased. |
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