Quantitative Classification Study Of The Characteristics Of Cataclastic Structure Rockmass In The Bedding Shear Zone Of Daguangbao Landslide

The structural plane of rockmass is the indispensable premise of studying and understanding the cataclastic structure rockmass(CSR),and it is the main reason for the intense heterogeneity of CSR.It is also the key to classify the characteristics of CSR and quantify the degree of fragmentation.In this paper,the CSR in the bedding-parallel shear zone of Daguangbao landslide induced by Wenchuan earthquake in the Longmen Mountain Fault Zone,which is researched as a representation.Through the refine investigation of structural plane characteristics,statistical analysis of the geometric characteristics of structural plane plane,test for the in-situ borehole shear and laboratory,3D network simulation and analysis of structural plane,which obtain some results in the structural characteristic,the quantitative evaluation and quantitative classification of CSR in Daguangbao landslide,as follows:(1)Structural plane characteristic analysis and 3D network simulation of CSR(1)Combining the manual contact measurement(method of scan line)with close-range photogrammetry,the refine investigation of geometrical characteristics of structural plane of CSR is carried out in two points that locate in Daguangbao landslide.The structural characteristics and the cataclastic extent of CSR have been preliminary understood.According to the investigative data,the characteristic database of the occurrence of structural planes,trace length,width of aperture and spacing are built.(2)Structural plane classification is researched by stereographic projection and the scatter plot of the dip,so the structural plane can be divided into 3 big groups and 5 small groups:(1)I,350°~15°?25°~45°;(2)II-(1),60°~100°?60°~90°;II-(2),240°~280°?60°~90°;(3)III-(1),120°~150°?60°~90°;III-(2),300°~330°?60°~90°?(3)The probability distribution model of sample data such as occurrence of structural planes,trace length,width of aperture and spacing are studied by frequency distribution histogram,the maximum likelihood method and least square fitting method to determine the characteristic parameters of the sample data.The study finds the occurrence of structural planes obey normal distribution.While the width of aperture and the trace lengths distinctively comply with exponential index distribution,and spacing submits to normal distribution or log-normal distribution.(4)Based on the theoretical analysis,the radius and density parameter of the structural plane are determined through the probability distribution and characteristic parameters of trace length and spacing of structure in the two investigative points.It is found that the difference of spacing is the main reason leading to the difference in degree of fragmentation and weathering between the two research sites,and the primary cause is that the two research sites are different in stress accumulation,dissipation and release.(5)Based on the statistical analysis of geometrical features of structural plane,using the software package based on Monte-Carlo method to generate the spatial coordinates and structural plane characteristic data which accord with the distribution rules of structural plane on a certain spatial scale.Using GeneralBlock software package to realize 3D visualization,the dynamic checking,verification and confirmation of the structural plane on the 3D model,which are carried out to ensure the high reliability and practicability.(2)Quantitative evaluation and quantitative classification of CSR(1)Using the 3D network model to generate the view profile of the two studying sites in Daguangbao landslide.The quantitative evaluation and quantitative classification of CSR in those sites are analyzed from the “Point-Line-Surface”.The finding reflects that different indexes in structural characteristics and fragmentation degree of the two studying sites.It shows that the relevant indexes can effectively distinguish the structural characteristics and fragmentation degree of the CSR.(2)The Borehole Shear Test and Hoek–Brown criterion are used to analyze the shear strength of the CSR.The shear strength parameters of two studying sites show significant differences and great similarities with its fragmentation degree of the CSR.The proposed quantitative index has certain applicability in geometrical features of structural plane and fragmentation degree of the CSR.(3)Based on the quantitative evaluation exploration of the CSR,Three Dimension System of the quantitative description and quantitative evaluation index system is proposed.Trace Node Density(TND),Trace Segment Length(TSL)and Trace Polygon Area(TPA)are proposed from structural characteristics of CSR.Aimed at the evaluation of fragmentation degree,Nodes Trace Rate(NTR),Trace Crack Index(TCI)and Surface Crack Index(SCI)are proposed.(4)According to the dual-track approach of “classification from the environmental and structural plane characteristics of rockmass ”,“classification from the structural characteristics and fragmentation degree of rockmass”,the CSR classification method is improved,and the classification method is proposed-CSRCM(Cataclastic Structure Rockmass Classification Method).Taking account of the characteristics of geological environment and quantitative structural plane,the classification method is applied to effectively solve the problem of quantitative classification of CSR.(3)The main innovation of this paper(1)Combining the manual contact measurement(method of scan line)with close-range photogrammetry,to obtain the structural plane of geometrical features,and it provides a practicable method for refine investigation and analysis of structural characteristics of CSR.(2)The statistical law of structural plane geometric characteristics of typical CSR is discussed.Monte-Carlo method is used to build network model of Daguangbao CSR.A preliminary exploration is made for the construction of mechanical and geological models of CSR.(3)The quantitative description and quantitative evaluation index system of CSR were established initially.According to the dual-track approach,it improves the CSR classification method,and proposes the classification method-CSRCM to build a foundation for further study of CSR.