Formation Mechanism And Discriminant Of The Layered Ragstone Slopes Unloading Fracture Zone In Chongqing

There are various sorts of geological hazards in Chongqing, such as landslides,perilous rock, collapses, debris flow, and so on. There is many perilous rocks, landslidesare derived from layered ragstone slopes, which featured with complex formationmechanisms, causing large scale and consequences disastrous. There are two problemsin the type of geological hazard assessment and treatment: low convincing theoreticalbasis for the stability assessment index and not much reliability on the managementengineering design. In the current research, general identification methods of unloadingfracture zone width are drilling and trenching. However, due to diversities of landforms,complexities of geological structures and limitations of scientific researchers’experience, there are many limitations and blindness in the identification of controlfissure, stability assessment and the reliability of treatment project. Specialized researchon the formation mechanism and identification methods of unloading fracture zonewhich are derived from layered ragstone slopes is deficient，although this sort of slopefailure is frequent. Therefore, it is necessary and practical to do some further researchon the formation mechanism and identification methods of layered ragstone slopes inChongqing region.In this study, a typical layered ragstone slopes in Chongqing is choosed as theresearch object. Based on the engineering geological survey, Analytical HierarchyProcess(AHP), extension theory and numerical analysis technology are adopted to setup a theoretical model of unloading fracture zone width. The theoretical model is usd onthe example of the Huangcaoshan Slope in Chongqing-Fuling highway, in order to testthe rationality and reliability of the results of this study.The main contents and results of the study are as follows:①Based on the engineering geological survey of typical layered ragstone slopes, astatistics is implemented on geometric characteristics, slope structures, structural plane,rock mass strength and weathering degree, and an analysis is used for the deformationcharacteristics of layered ragstone slopes.②Analysis every factor act on the development of unloading fracture zone inlayered ragstone slopes. Then, the formation mechanism of unloading fracture zone isexpounded, and a verify is paid through a numerical simulation method.③Choose controlling factors in the development of unloading fracture zone as assessment indexes, built the classification standard of assessment factors. Import thesimple relational degree conception of extension theory to sequence assessment indexesabout the importance. Then use the result to construct the judgment matrix, which canmake the result of weighting calculation is objective. On the basis of that, a extensionmodel is establish.④T ook the Huangcaoshan Slope in Chongqing-Fuling highway as example, theextension assessment model was used to identify the width of unloading fracture zone,the result showed that the grade of unloading fracture zone’s width was Ⅱ, it means thatthe width of unloading fracture zone was5～10m. In the meantime, a numericalsimulation method is proposed for the development of unloading change with thewidth,through the numerical simulation, set monitoring line and put the mutation pointsof displacement as demarcation points, the conclusion that the width of unloadingfracture zone was5～10m. The above-mentioned theoretical analysis and the results ofnumerical simulation were consistent with investigation data, which indicated thattheoretical model and identification methods of unloading fracture zone’s width hadgood accuracies. And with the unloading fracture zone’s width based on the slope isdivided with strong and weak unloading fracture zone, with different levels ofunloading have different governance proposals.