Study On The Deformation And Failure And Rockfall Movement Characteristics Of Potential Unstable Rock In The Yiwan Section Of Zhengwan Railway

The collapse of dangerous rock is one of the common geological disasters in the mountainous areas.Infrastructure construction represented by high-speed railways continues to advance into the mountainous areas.There are often more dangerous rocks and rockfalls on both sides of the route,posing a greater threat to the construction and operation of railway safety.This article takes the dangerous rock falling rock along the railway of Yiwan Section of Zhengwan Railway as the research object,based on the on-site investigation,the statistical analysis of the distribution law of rockfall rock in the study area and the classification according to the dangerous rock movement pattern,and analyzes and studies the danger from a mesoscopic point of view.Rock fissure development and expansion to study the mechanism of deformation and failure of unstable rocks,according to the different instability mechanism using damage-taking fracture mechanics method to evaluate the stability of unstable rock,through the combination of theoretical kinematics and discrete element method on the stability of dangerous rock after rockfall Conduct the analysis to provide technical support for reducing disaster losses.The specific results are as follows:(1)Through the preliminary on-site geological survey and data collation,the engineering geological conditions of the unstable rock in the investigation area were identified,the development and distribution rules of the unstable rock along the railway line were summed up,and the influencing factors of the stability of the unstable rock were analyzed,mainly including internal factors(topography).Geomorphology,formation lithology,rock structure,geological structure)and external factors(rainfall and groundwater effects,weathering and unloading,earthquakes,and human engineering activities).And the geological structure plays a leading role.(2)The three-dimensional laser scanning technology was applied to the unstable rock survey method to obtain the specific size of the high-steep unstable rock mass,the occurrence of important structural planes,and the profile.According to the unstable rock model,the unstable rock in the investigation area can be divided into five categories: compression-shear-sliding type,split-pile type,pressure-shear type,falling-fall type,and isolated-type dangerous rock,and the potential mechanism of instability for different types of unstable rocks is analyzed.(3)By using numerical experiments to fit the parameters of the rock chamber experiments,the development of internal microcrack development at different stages was analyzed.It was concluded that the microcrack started to occur at the elastoplastic stage,the microcrack developed rapidly during the loss of strength,and the microcracks in the complete destruction stage were concluded.It penetrates and analyzes the microcrack development process from the aspects of normal contact force and tangential contact force between particles.The corresponding microscopic parameters are applied to the deformation and failure process of unstable rock.According to the microcrack accumulation curve in numerical experiments,the deformation and failure process of dangerous rock is divided into the initial stage of crack development,rapid development stage,and crack penetration failure stage,which expands from the crack development for directional analysis of the mechanism of the instability of typical rock.(4)The stability of the unstable rock is controlled by the structural plane of the rock mass that is continuous or intermittent behind,the damage and fracture process is the root cause of the unstable collapse.In this paper,Chen Hongkai et al.used the fracture mechanics method considering damage to analyze and study the tip crack development and extension behavior of the critical rock face of the critical rock under load conditions.The stability evaluation method of the dangerous rock was established to evaluate the stability of the dangerous rock within the study area.The analysis results show that the dangerous rock in the area is in a basically stable state under natural conditions,and the stability is differently reduced under the conditions of heavy rain or earthquake,and the stability is reduced.The impact of heavy rain and earthquake forces must be taken into account when formulating prevention and control measures.(5)From the point of view of kinematics,the initial sliding stage,ejection stage,collision stage,and rolling stage of the motion process after the instability of dangerous rock are analyzed,and kinematic formulas are established for each stage.Through the analysis and comparison of the theoretical calculation method and PFC simulation of the B-B' engineering geological profile of the Shenlongjia Bridge,the rockfall motion process path is calculated for the slope model and the characteristics of the motion process are summarized: Since the rockfall is simplified to a spherical shape in the theoretical process,the block collision is ignored.In the course of its impact,the calculated collision speed and rebound height are larger.