| The collapse of the rolling mill in Lizhou District of Guangyuan City had existed for many years before the Wenchuan earthquake.When the "5.12" earthquake occurred,many collapses took place on the mountain and the total amount of collapse was more than 80m3.Some of the collapsed bodies accumulated on the uphill road and the village road.The gentle slopes behind the farmer households are affected by weathering and rainfall.At present,some of the dangerous rock bodies are in an unstable state,which poses a serious threat to the lives and property of the people in the villages near the study area.On the basis of mastering the engineering geological conditions in the study area,this paper identifies the characteristics and distribution of dangerous rock in the study area,divides the deformed area according to the deformation conditions,and analyzes the influencing factors of the development of the collapsed body.The deformation mechanism of the collapsed bodies in the study area was used to judge and classify the instability failure modes of the dangerous rock in the study area,and the stability of the collapsed bodies in the study area was evaluated from both qualitative and quantitative perspectives,and the Rocfall was used.The simulation of the unstable motion process of dangerous rock masses shows that the simulation results are good and can be used as a reference for the design of prevention and control engineering measures.The main results achieved are as follows:(1)The study area is located in Lizhou District of Guangyuan City.It is located in the Yanshan fold area of Taibei,Taiwan,and it is a gently inclined monoclinic structure that tends from southeast to south.The high intensity rainfall in the area is unevenly distributed over time and forms large areas.Heavy rain or local storms are important causes of geological disasters such as landslides and landslides.During the"5.12" earthquake,several collapsed rockfalls occurred on the study area,and human engineering activities had little impact on the formation and development of the collapsed body.The difference in the weathering velocity of rock masses,and the formation of concave rock cavities in the collapsed body,is one of the important boundary conditions for the formation of dangerous rock masses,with typical characteristics of differential weathering.In addition to strong weathering along the unloading fissures or structural fissures in the steep slope,the rock mass is generally not strongly weathered.Some slopes in the study area are steep and steep,and the relative height difference of the steep cliffs is more than 20-40m.The natural stress is relatively high.After the formation of the steep cliffs,under the influence of long-term stress release and gravity,the cliff body is facing the air.Directional unloading rebound obvious signs of deformation.(2)According to the degree of deformation of the collapsed mountain,the collapsed mountain on the roller is divided into a strong deformation zone and a general deformation zone.The strong deformation zone extends in the direction of N34°W,showing three strips of convex strips,with the geomorphological characteristics of the cliffs distributed on the plane.The distribution is mainly controlled by the development direction of the cliffs,and the cliffs develop roughly in the plane.It has a step-like distribution and is developed in the southeast direction.The cliffs are roughly divided into two levels.Combining the location,deformation properties and the development characteristics of the dangerous sections of the deformation sections,the entire mountain strong deformation area is divided into ?,?,?.There are a total of 4 dangerous rock belts in the district and IV area.The general deformation zone is located in the middle and upper part of the mountain,except for the four strong deformation zones,including the steep cliff foot platform and the collapse accumulation slope zone,and the stability is relatively good.The factors affecting the development of the collapsed area in the study area are mainly divided into two major categories:1 Intrinsic factors:topography,lithology,structural fractures;2 external factors:earthquakes,rainfall.There are two main potential deformation instability modes in dangerous rock in the study area:1 sliding type;2 dumping type.According to the current penetrating situation of the structural plane of the dangerous rock mass,the sliding collapse can be divided into two sub-categories:the partial sliding rock mass in the surface fractured rock mass and the overall slipping rock mass.(3)The hazards of deformation of dangerous rock on the roller coast in the study area are characterized by "wide distribution and great harm".The comprehensive evaluation of the stability of dangerous rock masses was made from qualitative and quantitative aspects.For qualitative assessment,according to the actual situation in the study area,a set of stability evaluation criteria has been established;the quantitative evaluation has mainly been based on relevant national norms and regulations,and the corresponding evaluation criteria have been determined.The results showed that the slopes in the natural state are basically stable—the state of understable conditions.Under storm conditions,they are in a state of understableness,and there are local collapses(sliding)and collapse.Under earthquakes,the mountains are under-stable—unstable state.Mainly in areas ? and ?.Based on the previous studies,the process of deformation and collapse of collapsed hills is divided into three stages:initial displacement stage,collision stage,and rolling-slip stage.And simple analysis and analysis of each exercise stage were conducted to understand the whole process of collapse rockfall.The Rocfall software was used to simulate the motion path of the unstable rock mass W6 and W15 after deformation failure.The results show that it is consistent with the actual situation on the site,and the simulation results can be used as a reference for the design of prevention and control projects.(4)The method for controlling dangerous rock masses was briefly introduced from three aspects:active protection technology,passive protection technology,active-passive joint prevention and control technology,and the overall prevention and control ideas for dangerous rock mass in the study area were clarified,according to Rocfall The simulation results of rockfall bounce height and impact kinetic energy have determined the final prevention and control design scheme:manual clearance +C25 piece stone concrete support + M10 mortar closed crack + hanging net spraying+ falling stone trough + SNS passive protective net. |
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