Optimization Study On The Feature Of Slope Of Rocfall Threatening Sections

With the support of the National Natural Science Foundation of China(grant number:51108488), the paper analyzed the rocfall movement parameters under the different factors including rocfall quality、slope height、slope angle、character of slope、 slope-combination through rocfall calculation software(RocFall),and found out the sensitive factor of movement character of rocfall and explored the laws of rocfall movement, and provided a basis for passive prevention optimization. The main results can be obtained as follows:1、Assuming all other things being equal, the paper developed the conclusions through single factor analysis on the case of different rocfall quality、slope height、slope angle、slope pavement、slope-combination,etc.(1) Based on the different quality, the maximum kinetic energy increased with the increase of the quality of rock fall, and the average of final position、the maximum bounce height、the maximum velocity were varying in different slope with quality. The average of final position and the maximum bounce height increased with the increase of the quality of rock fall on the single slope. However, there was no regularity with quality on the composite slope.(2) Based on the different slope height, the average of final position increased with the slope height between20m and80m and the regularity was opposite between80m and100m on the slow-steep-slow composite slope. Under other circumstance, the average of horizontal motion final position、bounce height、kinetic energy、velocity increased with the increase of slope height.(3) Based on the different slope angle on the single slope, the average of horizontal motion final position increased with the increase of slope angle between45°nd55°, and the regularity was opposite between55°and85°; the maximum bounce height、the maximum kinetic energy and the maximum velocity increased with the increase of slope angle between45°and75°and the regularity was opposite between75°and85°.The average of horizontal motion final position、bounce height、kinetic energy、velocity increased with the increase of slope angle on the composite slope.(4) Based on the different slope pavement, if the recovery coefficient of slope pavement was smaller, the impact of rocfall motion characteristics was greater. There was more obvious impact on rocfall motion characteristics when the pavements were set up on the whole single slope、the upper steep slope and slow slope of steep-slow-steep composite slope、slow slope of slow-steep-slow composite slope and slow slope of negative relief-slow composite slope. For different slope types, respectively, it can be set shrubs、soil and vegetation、gravel and a small amount of vegetation、rubble、etc. And the influence of rocfall movement characteristics with the pavement was reduced in turn.(5) Based on the composite slope type with the slope angle chose to90°,the rocfall maximum kinetic energy and maximum velocity on the slow-steep-slow composite slope were larger than steep-slow-steep composite slope. Under other circumstance, the average of horizontal motion final position、the maximum bounce height、the maximum kinetic energy、the maximum velocity on the steep-slow-steep composite slope were larger than on the slow-steep-slow composite slope.2、Different slope optimization designThe single slope. When the safe net system was set up on the slope, the height of safe net system was set3.0m because the rocfall bounce height was Om.As well as setting step+pavement on the step+safe net system on the side slope or stone falling channel on slope toe(height:1.5m～2.0m;width:1.0m～1.5m) can effectively intercept rocfall.The composite slope. When the composite slope angle was relatively small, measures can be taken by pavement or setting step+pavement on the step+safe net system on the side to prevent the rocfall effectively; Stone falling channel was set up between steep and slow slope on the steep-slow-steep composite slope. The size of height was1.5m～2.0m, and the size of width was1.0m～1.5m;Stone falling channel was set up on the upper slow slope on the steep-slow-steep composite slope. The size of height was0.5m-1.5m, and the size of width was1.0m～2.0m.The step、pavement and safe net system were set up on the slow slope on the negative relief-slow composite slope.