Study On Characteristics And Stability Evaluation Of Collapse In Hongshiyan Water Hydro-junction Slope

China is a country with lots of collapses which have caused great losses and threats to people's life and property safety,particularly in the southwest.These place have high mountains,deep valleys,geological structure,large regional faults,earthquake disasters,so that there are many collapse disasters in the region with large volume.An earthquake(M=6.5)occurred on August 3,2014 in Ludian of Yunnan Province.The earthquake caused great collapse on the north bank of Niulan river in Hongshiyan village of Huodehong town.The collapse accumulation truncated Niulan river and formed a barrier lake.Carefully surved by experts,they agreed that let the barrier lake become a useful project.They think that we can build Hongshiyan Hydro-junction using the barrier dam.Because of earthquake and perennial weathering denudation,reservoir area have high and steep slope,serious collapses.There were several collapses in one year after August 3,2014 and the largest quantity reached 70 thousand stere.These become the most serious hidden danger for the construction and operation of hydraulic engineering.This papper take reservoir slope collapse as research object and systematically analysis ancient collapses,8·3 earthquake collapse,after the earthquake collapse and potential collapse.This paper detailed analysis the development characteristics of collapse,instability mode and assess the stability of potential collapses.We studied the motion feature of rockfalls in the hydro-junction area.The main research results are as follows:(1)The distribution of collapse development is analyzed.Based on the characteristics of time,space and movement,we studied the distribution law of the development of ancient collapse,earthquake-induced collapse,post-earthquake the inlet of spillway hole collapse,it can be found that the collapse scale decreases and the right bank is more than the left bank.(2)The instability mode of collapses is analyzed in detail combined with the collapse of the reservoir area.According to the collapse of the formation mechanism and instantaneous form in instability,it is classified into five basic types: toppling,sliding,distending,pull-splitting and sluggered collapses.(3)8.3 earthquake(B1)was simulated Using the discontinuous deformation analysis(DDA)method.The instability mode and properties of collapses were analyzed,the results demonstrated that instability mode of the collapse under earthquake action has unique characteristics of shattering and mass ejection,and the movement distance of the rockfall block is far,meanwhile the energy is huge,which is different with the collapse under normal gravity.(4)The factors that affect the stability of collapse are analyzed according to the conditions of reservoir area.The result indicated main influencing factors include topography and geomorphology,earthquake,geological structure,action of water,formation lithology and its combination.Moreover,earthquake is one of the most critical factors in the study area.(5)The stability of ZZWY1,the potential collapse of perlite slope considered the natural conditions and rainfall conditions,was studied by the limit equilibrium method and universal distinct element code(UDEC).The result showed that the native state of ZZWY1 was stable,however,ZZWY1 has poor stability under the heavy rainfall,and the safety coefficient is less than 1.1.Taking into account the safety margin,the potential collapse body should be effectively treated.(6)Use Rockfall software to analyze the movement of rockfall and collapses in reservoir slope.Research on the trajectory of collapse rockfalls of traffic hole at the top and the ancient cliff collapse at left bank.The corresponding passive protection measures are given by numerical analysis.The impact force of the rolling stones on the shed and the stone wall is calculated by using the method of subgrade code method,tunnel manual method and Japan Road Group method.The above results are of practical significance to the project of Hongshiyan water hydro-junction project.Through the study of bank development and distribution rules,obtain the development and distribution characteristics of potential collapse.Combined with field investigation,the key control areas were delineated.This paper makes a detailed evaluation of the stability of the potential collapse(ZZWY1)in the region with poor stability and high hazard.It is considered that the ZZWY1 stability is poor and should be reinforced or removed.The characteristics of the rolling motion of the left and right sides of the dam site are studied.The setting position and height of the stone wall and the length of the shed hole are given.At the same time,the suggested impact force number of stone wall and shed hole is calculated.