The Indoor Model Experimental Study On Rockfall On The Rock Slope

More geological disasters often happen in the mountainous of southwest China which is because of the complicated terrain and geological conditions.Rockfall hazards, one kind of geo-hazards in mountains of southwest China, often causes national economy and casualties losses quite serious every year which caused by the various linear engineering and banded structure especially the railway as an important tool of the main modes of transport and national passenger and cargo turnover.According to statistics of the Ministry of Railways, thousands of rockfall hazards happen along the national railway every year. As a result, the severe and widespread damage rockfall hazards becomes one of the major hazards of the traffic engineering.Because of the complexity, uncertainty, sudden and many factors of rockfall hazards,many issues especially how to design for protection against rockfall in the engineering applications need to be resolved by analyzing problems, finding out the law, and proposing appropriate measures.The rockfall on the rock slope are chosen as research object. Rockfall model tests, rockfall trajectory and theoretical analysis about key parameters and sensitivity analysis about the run-out distance were carried out, then analysis the rockfall geo-hazards of the Yangjia tunnel which is located at the Guizhou-Guangzhou high-speed railway.Following results have been carried out:1.The compound slope which is common along the railway in the mountainous were used as prototype. The following conclusions are obtained: ①The horizontal movement distance of the plate-like block whose starting mode is scrolling vertically comes the first following with the spherical and square block,then the horizontal movement distance of rod-like block is minimal. ②The quality of the block and the characteristics of the covering of the slope on the influence of the horizontal movement distance was not significant,but the correlation between the quality of block and the horizontal movement distance is positive certainly.③The Shape of the blocks affect the lateral migration ability directly.The lateral migration ability of the rod-like and plate-like block is stronger than the spherical and square block,however the randomness of the former is also larger. ④The impact of the spherical block is the largest, the second is square, and there is not much difference between the rod-like and plate-like block.The correlation between the quality of block and impact coefficient is negative.2.It’s showed that the lateral offset capability of rod-like block and plate-like block is stronger than spherical block and square block.What’s more,there are 99.38% rockfall coming with lateral displacement less than 0.25,97.22% rockfall coming with lateral displacement less than 0.2,78.70% rockfall coming with lateral displacement less than 0.1.The transverse distance ratio are given a suggested coefficient:0.3.3.Artificial neural network was applied to predict run-out distance of rockfall.The trained artificial neural network that achieves instant prediction of run-out distance takes slope angle,slope height, slope surface conditions, mass and shape of rock block into account.Sensitivity analysis based on the parameter changes shows that:①As to the angel of slope,the run-out distance decrease with it in the range of 41.08°to 46.98°.②As to the height of slope,the run-out distance is proportional to it.③As to the covering of slope, the run-out distance decreases sharply when the covering of slope in the rang of 1.0 to 1.6. The run-out distance is proportional to the the covering of slope when the covering of slope in the rang of 1.6 to 3.0. The run-out distance increases mildly when the covering of slope in the rang of 2.6 to 3.0.④As to the quality of rockfall,the run-out distance is proportional to it. The run-out distance increases mildly when the quality of rockfall in the rang of 0.22kg to 0.30kg.⑤As to the shape of rockfall, spherical rockfall come with longer run-out distance, then followed by square block;rod-like block come with shortest run-out distance but the run-out distance of plate-like block does not show apparent difference due to their run-out distance affected by motion model strongly.What’s more, the analysis of connection weights indicate that decreasing order of relevant parameters affecting run-out distance is as following:slope surface condition(34.69%), slope height(23.05%), slope angle(18.45%), shape of rock block(14.55%) and mass of rock block (9.26%).4.As the research object to the Yangjia tunnel slope which is located at the Guiyang to Hezhou section(DK171+774-DK172+041)of Guizhou-Guangzhou high-speed railway, The tunnel entrance passage rockfall risk level is evaluated as dangerous system with Rock Hazard Rating System of Tunnel Portal Section.Then the comprehensive prevention of rockfall hazards can be conducted which according to the bounce height, kinetic energy and velocity of rockfall motion with RocFall.