Development Characteristics And Countermeasures Study Of Potential Unstable Rock Masses Along A High-speed Railway In Chongqing

The typical lithologic association characteristics of Chongqing area is interbeding of sandstone and mudstone, and soft rock account for a large proportion in the interbeds. The distribution and engineering properties of the weak intercalation largely controls the deformation and failure mechanism of rock mass, so potential unstable rock can easily be seen along those slopes.The existence of potential unstable rock becomes a main threaten to the safety of railway lines in southwest China.Taking the potential unstable rock mass along a high-speed railway in Chongqing as a example, based on rock mass structure control theory, numerical simulation, static analysis method and three-element method, this paper studied the classification, failure mode, failure mechanism and evolution process,stability and risk assessment of the potential unstable rock masses of alternating layers of hard and soft rock slopes, and finally presented simple control measures for dangerous rock masses in different situations.Following are the achieved results and understandings.(1) Based on the data collection and detailed field investigation of the natural and geological conditions of the study area, an initial understanding of the regional geological setting and geological conditions were formed.Chongqing lays in the transition zone of the Yangtze River Basin and the Qinghai-Tibet Plateau, where has a mild climate, abundant rainfall, geological structural develops and has strong weathering and unloading, provides good natural and geological conditions for the formation of dangerous rock masses.(2) Analyzed the influencing factors of dangerous rock masses, and classified the potential unstable rock masses by failure mechanisms into seven types, which are creep-crack, slip-crack, dumped-crack, plastic flow-crack, rifting relaxation, falling and boulder, and among which slip-crack can be divided into wedge slip-crack and planar slip-crack. Various types of unstable rock formatted in different geological environments, and sometimes their modes can transfer into each other.(3) Based on the detailed analysis of instability mechanism and evolution process of all kinds of dangerous rock masses in the study area, this paper described the control factors of all kinds of dangerous rock masses, and simulated and evaluated the failure mechanism and deformation evolution of several typical dangerous rock masses by Discontinuous Deformation Analysis method.The controlling factor of the stability of the dangerous rock mass is not an independent existence. Various dangerous rock masses have various influencing factors.(4) Described several commonly used stability evaluation methods of potential unstable rock mass, which including geological-process-mechanism method, graphic method, engineering geological analogy method, rigid body limit equilibrium method, and evaluated the stability of typical dangerous rock masses by rigid body limit equilibrium method. According to the classification method and failure mode of the dangerous rock mass in the study area, they can be divided into there types, which are unstable, stable and basic stable.(5) Described the commonly used three-element method for risk assessment of potential unstable rock masses, and used this method to assess the risk of some typical dangerous rock masses. The three-element method can evaluate the risk of potential unstable rock masses by three factors, which are the size, the steady-state and the movement path of the rock masses after falling. The evaluation method is very simple and practical.(6) Elaborated the countermeasures of the dangerous rock masses in the study area, and put forward treatment measure suggestions for the potential unstable rock masses. This paper described the active control principle, passive control principle and active combining with passive control principle, and also illustrates the active control measures, passive control measures and alarm measures in potential unstable rock masses prevention.