Mechanism On Instability Of High-locality Cataclastic Rock Mass And Prediction On Its Accumulation Area

According to the continuous uplift of the Tibetan plateau and the internal and external dynamic geological processes,the geological environment in the mountainous areas of southwest China is very complex and special.After the high-locality rock mass becoming unstable,it usually has the characteristics of high speed and high potential energy.The rock debris flow formed by its impact with the mountain is a geological disaster with extremely strong destructive force and extremely wide disaster range.The debris can be transported to a great distance at high speed in a very short time and form an accumulation area with a large coverage.The instability mechanism of high-locality rock mass and the prediction of its accumulation area have become an urgent problem to be solved.This paper relies on the national science and technology support plan project “study on disasters process control theory and dynamic control technology of highway subgrade in southwest mountain area”(No.2015BAK09B01).The "6.24" landslide in Maoxian county,Sichuan province was taken as the research background,the instability mechanism of high level cataclastic rock mass and its accumulation area are studiedBased on the main factors of precipitation to induce cataclastic rock instability,using theoretical analysis,numerical calculation and simulation test method,studied the horizontal pushing integral type two kinds,behind the locking instability mechanism of fractured rock mass,and to explore its accumulation scope,combination of maoxian county new ground landslide debris flow accumulation zone migration distance optimization formula is put forward.The main research work and results of this paper are as follows:(1)The instability mechanism of high-locality cataclastic rock mass under the action of precipitation is studied.According to the occurrence characteristics of high-locality cataclastic rock mass,the cataclastic rock mass can be divided into two types: the horizontal push-type integral instability rock mass which the potential slip zone is fully penetrated and the latch-type rock mass which is locked to the bedrock.Then the rock mass instability mechanism under the two modes is analyzed respectively from the angle of hydrostatic pressure and deformation energy.The head line equation and the critical head height of the whole rock mass with horizontal thrust are obtained,then the width of the seepage in the sliding zone is discussed,and the head line equation is optimized.The elastic velocity formula for the instable moment of cataclastic rock mass is derived and the elastic velocity and acceleration of the instable moment of cataclastic rock mass are deduced.(2)Experiments were carried out on the range of unstable accumulation of high fractured rock mass.The effects of six different factors,such as the height of the cataclastic rock mass,the dip angle of the potential slip zone of the cataclastic rock mass,the elastic velocity of the cataclastic rock mass,the volume of the cataclastic rock mass,the particle size of the clastic grain and the clastic grain gradation,on the accumulation range are studied.Through multiple groups of experimental studies,it can be found that,with the change of various factors,the starting point position of the accumulation area will have a relatively obvious change,but the range and the point where the particles reach the farthest position do not have obvious change,and the accumulation area shows a law of overall forward or backward movement.(3)Numerical analysis software was used to calculate the accumulation range of fractured rock mass,and the particle distribution histogram,the particle horizontal velocity envelope,the total kinetic energy envelope and the bounce height envelope were obtained.Through the analysis of the output figures and data,the first impact point position,the range of the accumulation area and the farthest reaching position of the clastic particles between the fractured rock mass and the slope mass after the instability are obtained,and the results are compared with the simulation test results to obtain the distribution characteristics of the accumulation area.Then,through means of orthogonal analysis,the sensitivity of the three factors of the height of the fractured rock mass,the velocity of the rock mass and the dip Angle of the sliding zone to the accumulation range is evaluated.(4)The "6.24" landslide in Maoxian county,Sichuan province was taken as the research background,according to the geological characteristics of the high-locality cataclastic rock mass,its stability is analyzed,and then the elastic velocity and acceleration of the cataclastic rock mass are calculated.The maximum length of the stacking range is calculated by using Scheidegger 's formula,and the result is compared with the numerical value in the case,then the formula is optimized.