| This accumulation body located Right Abutment of Lianhe Reservoir Dam in Meigu County,Sichuan Province,with a total volume of about 609.1×10~4m~3.Along with the excavation of the slope,a small-scale landslide occurred on the abutment slope of the right bank and multiple cracks occurred at the trailing edge.As the project continued to advance,the cracks continued to expand and extend.Once the overall or partial instability occurs,it may cause disasters such as reservoir siltation and dam breakage,which seriously threatens the safety of residents and downstream camp personnel and equipment on the slope body.Therefore,the study on the geological background,basic characteristics,genetic mechanism and stability of the accumulation body of Right Abutment of Lianhe Reservoir Dam is very necessary to ensure the safe operation of the reservoir.The paper is based on the research topic of the stability of Stability Analysis of slope of Right Abutment of Lianhe Reservoir,based on a detailed review of the genetic mechanism of the accumulation body,the features of the excavation deformation,the stability of rainfall and reservoir water level changes,combined with indoor and outdoor experimental analysis,studies the geological background,material composition and structural characteristics of the deposits,and their deformation mechanism,and through the macro-geological qualitative judgment,limit equilibrium calculation and numerical simulation analysis,systematically studied the stability of the accumulation body,and provided geological basis for the safe operation of the reservoir.The contents and results are as follows:(1)The accumulation body is distributed in the direction of NWW.The height difference between the front and rear edges is up to 100m,the slope is between 14 and22°,and the total volume is about 609.1×10~4m~3.It is mainly composed of blocks and crushed soil,and it comes from the sliding of the original slope.(2)According to the composition and structure of the material and the characteristics of deformation and destruction,the deposit is divided into three regions,in which the II region is divided into two subregions II1 and II2;there are few signs of deformation in the regions I,II1,and III.The front edge of the II2 area appears landslide,cracks develop,and presents the trend of gradual extension toward the back of the deformation slope and even the accumulation slope.(3)Adopt indoor test,mathematical statistics,empirical formula and parameter inversion method were used to study the mechanical properties of rock and soil mass.Nearly 300 engineering examples with similar characteristics have been collected.Through mathematical statistics,the general representative strength parameters are obtained.A method for the inverse analysis of strength parameters based on experiment and finite element method and the empirical formula of mechanical parameters of rock fragments obtained by this method can be used as reference for similar projects.(4)The“geological process mechanism analysis”as the guiding ideology,the influencing factors and evolutionary processes of the accumulation body were carefully analyzed.The results showed that:the main influencing factors are three facing the empty topography and landforms,sandstone and mudstone interbedded layers outside the gently inclined slope,and carbonaceous shale weak zone.The formation and evolution process basically went through the following four stages:wadi’s down-cutting,unloading and rebound of rock mass,trailing edge cracking phase→pull cracking face from top to bottom continuous expansion,finally through phase→triggered by torrential rain or earthquake,the slope slides along the soft surface→the stage of late water transport,erosion and human engineering transformation,and the landslide belongs to sliding-tension type..(5)Based on geological history analysis and numerical simulation,the process of slope deformation and failure in the II2 area of the accumulation body was studied.The results show that the main influencing factors of the slope deformation in the II2area are the free surface conditions,the loose soil and rainfall,the deformation and failure process basically goes through the following three stages:excavation unloading,rebound,local fracture,creep stage→leading edge local landslide stage→trailing edge deformation stage The deformation failure mode is creepage sliding-tension type..(6)The macro-geological qualitative analysis of the geology suggests that the overall stability of I and III areas of the accumulation body is good;the II2 area may have a greater instability under the conditions of rainfall and earthquakes.Quantitative calculations by the limit equilibrium method show that the overall and local stability coefficients of the accumulation zone I area meet the safety standards under the most unfavorable conditions,and the overall stability of zone II is basically stable after the excavation of zone II.It may be unstable under heavy rainfall conditions,and it is in the limit equilibrium～instability state after the reservoir impoundment.(7)Based on finite element analysis and rigid body limit equilibrium analysis,the results show that different rainfall intensities have limited impact on the overall stability of the accumulation and have a greater impact on the stability of the L1potential landslide.With the increase of rainfall intensity,the potential sliding body stability will change from the basic stable state to the under-stable state,even the instability failure.With the increase of rainfall time,the rate of decrease of the stability coefficient of the accretion shows a slow-fast-slow trend.Under a heavy rainfall,the stability coefficient of the accumulation body shows a rapid decrease-fast increase-slow increase.The stability of the accumulative body is good during the reservoir water level rise,but after the stop of the reservoir water level rise,the stability coefficient of the accumulative body due to the increase of water saturation gradually decreases;the stability of the accumulative body is unfavorable during reservoir drawdown,and the decline occurs.After the stop of reservoir drawdown,the stability coefficient gradually increased.The effect of the reservoir level fluctuating on the overall stability is less than the effect on local stability,and the effect on local stability is hysteresis.The hydro-mechanical coupling study shows that the distribution of the stress field of the accumulation body is mainly affected by the self-weight stress,and has the general slope stress field distribution characteristics.The thickness of the deposition body is different in different positions,and the stress size and distribution status are also different;the slope deformation mainly occurs on the slope foot under the rainfall and the reservoir level fluctuating after excavation.At the same time,it is also affected by microrelief. |
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