| With the rapid development of Chinese economical construction,the scale of the infrastructure and resources exploitation are increasing,which are faced by plenty of engineering problems.Especially in the process of mining activities,high slope with complicated engineering geological conditions and large scale are common.It is also the jointed rock mass that controls the high slope stability.Jointed rock mass is complex which is formed by structural plane and intact rock mass.It is the complexity of jointed rock mass that determines the heterogeneous,nonlinear and anisotropic mechanical properties of rock mass.The strength characteristics of jointed rock mass is not only influenced by the strength of internal rock and structural planes,but also by the structural planes of different combinations of strength degradation at the same time.The study of the jointed rock mass structure characteristics and strength parameters are significant parts for rock mass stability evaluation and analysis of mechanical properties.In this paper,using the Esheng limestone mine open-pit mining high slope rock mass as the research object,a systematic study on the characteristics of jointed rock mass strength parameters was conducted.Based on the field investigation and data collection,the anisotropy and scaling effect of jointed rock mass were discussed using the 3-Dsimulationtests and experience estimation method,which further provided the reference for the reasonable selection of jointed rock strength parameter.The results of the research are summarized as follows:(1)Field engineering geological investigation was done to further regionalize the research area based on the rock structure differences.Based on the scan-line method,field data about discontinuities was gained as follows: 50 discontinuities were investigated in area ?,with one set of preferred discontinuity;106 discontinuities were investigated in area ?,with two sets of preferred discontinuities;323 discontinuities were investigated in area ?,with four sets of preferred discontinuities.(2)With the combination of the traditional plots analysis method and the modified fast clustering method,the preferred discontinuities in the research area were divided into groups.The probability distribution modes of the geometric characteristic parameters of discontinuities were obtained using the probability graph method,the results of which revealed that for most discontinuities,their dip direction and dip angle conformed to the law of normal distribution,while few discontinuities were uniformly distributed;what's more,the spacing and the half-length of the discontinuities were consistent with the negative exponential distribution.(3)Based on the probability distribution models gained above,Monte Carlo method and Fish programming language were applied to the establishment of 3-D joint network model in 3DEC software.With the analysis of the 3-D joint network model,it can be concluded that rock structure in area ? was complete with few surface cutting;rock was cut by two sets of vertical joints,leading to the blocky structure in area ?;rock structure in area was unfavorable,which was cut by four sets of preferred discontinuities ?.(4)3-D simulation tests were conducted on three kinds of rock structure;with the combination of DFN fissure network model and Monte Carlo method,the numerical tests could well simulate the field stress condition of the rock mass.Research on the anisotropy and scaling effect of rock mass strength parameters indicated that anisotropy and scaling effect differed with different rock structure.With higher cutting degree,the scaling effect of rock mass would be more obvious while the impacts of anisotropy would lessen.(5)Joint strength parameters were selected with the comprehensive comparison of numerical simulation?RMR rating system and GSI rating system,it turned out that the strength parameters gained,in decreasing order of values,were 3DECsimulation?GSI rating system and RMR rating system. |
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