Study On The Formation Mechanism And Movement Characteristics Of The "4.20" Eagle Rock Collapse In Ganzi Prefecture

Rock avalanche is one of the geological disasters in mountainous areas with unexpected and irresistible characteristics,which has caused huge casualties and property loses each year all over the world.In order to reveal the mechanisms and laws in the whole process from the development to the instability of perilous rock,the paper studies perilous rock in Eagle Point,Guzan Town,Kangding County.The major results include the following six aspects:(1)On site engineering geological survey is employed to present the fundamental characteristics of perilous rocks in high steep slope.Three perilous rock bands and a perilous rock with a total volume of 42048 m3 are discovered in the research area,featuring an arc-shaped line from north to south in a plane.The perilous rock section,which distributed at the elevation between 1655.37 and 1984m is 737m long.Four accumulation areas of collapsed perilous rocks are inquired in the research areas,which are mainly distributed in the lower-middle part of the slopes.(2)The formation mechanisms are analyzed from the aspects of internal and external factors.Six factors are concluded,including landform,formation lithology,geological structure,hydrometeorology,seismos and weathering burden.According to the perilous rock's initial movement state,three unstable modes of perilous rock are concluded such as vertically falling,rotary toppling mode,tilt slipping mode.(3)Through stereographic projection technique analysis,three perilous rock bands and one perilous rock are located in understable state.the stability coefficient of Perilous rock is 3.794 in natural condition,1.682 in rainstorm condition and 0.958 in seismos condition through analysis according to static analytical theory.(4)Orthogonal test theory is employed to analyze the sensibility of main factors which can affect the movement features of perilous rocks.Taking the horizontal distance of rockfall as indexes,The sequence of sensibility influencing factor is slope angle of friction,normal recovery coefficient,tangential restitution coefficient,initial horizontal velocity,initial vertical velocity.(5)The values of normal recovery coefficients,tangential restitution coefficients and slope angle of friction in different position of the slopes are gotten through inverse analysis based on orthogonal test.The value for the basic rock section of perilous rock is 0.37,0.88,26°.The value for the rubble slope section with vegetation growing is 0.33,0.83,32°.The value for the rubble slope section without vegetation growing is 0.32?0.82?35°.(6)The movement features of falling rocks with different quality is simulated and calculated on the main collapsed path by Rockfall Software.It is concluded that falling rock of different quality is mainly bouncing and rolling on the slope of the researching area and the quality change of falling rock does not influence its maximum speed and bouncing speed obviously.But the quality change of falling rock does influence its maximum kinetic energy obviously.The furthest horizontal distance of falling rocks with different initial velocity is stimulated and analyzed by Rockfall Software.The furthest stop range of falling rocks is obtained,which is between 628.7m and 729.4m.