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Grouping discontinuities in representative sets: influence on the stability analysis of slope cuts

A. T. Nguyen
V. Merrien-Soukatchoff
M. Vinches
M. Gasc-Barbier
Journal / Anthology

Bulletin of Engineering Geology and the Environment
Year: 2016
Volume: 75
Page range: 1429-1444

Based on their orientation, different methods of grouping discontinuities in sets can be used; thus, three grouping methods and their influence on subsequent stability analyses are compared in this study. The first method combines the approaches of Priest, Shanley, Mathab and Yegulalp; the second method consists of grouping discontinuities manually based on an examination of density contour plots; and the third method is based on the spectral method. Unlike the others, the first method allows for the automatic determination of the number of discontinuity sets. The first and third methods were programmed in the Mathematica software environment, while DIPS software was used for the second method. Depending on the grouping process used, each discontinuity or only a portion of all discontinuities is assigned to a set. Therefore, the results in terms of the number of sets; the mean and dispersion of the sets; and the spacing of a given set differ with different methods. The consequences of a statistical analysis of orientation on the stability analysis were studied with simulations using RESOBLOK software, which couples the construction of 3D geometric block systems and a quick, iterative, limit-equilibrium stability analysis. Different fracture networks were generated with variable input parameters that were derived from previous statistical analyses of orientation and spacing. The software provides statistical outputs, such as the number and volume of unstable blocks, that can be compared across different cases. An application in a cutting slope near Ax-les-Thermes is presented; the influence of the grouping methods and of the uncertainty of slope orientation on stability indicators is presented. A synthetic indicator of global stability is also proposed.

*Science > Geology and Geophysics