Probabilistic Estimation Of Discontinuity Size In Rock Mass And Study Of Application For Three-dimensional Network Model

The paper is based on the key project of the National Natural Science Foundationof China (Grant No.41330636). And it proposes new methods to estimate the size andtrace length of discontinuities and applies the results to establish a three-dimensionalnetwork model of dam abutment rock mass in Songta hydroelectric station. And theconnectivity rate of bottom slip surface of dam abutment rock mass is the final resultof this paper. Four main conclusions are drawn as follows:(1) The widely used Kulatilake’s method for estimation of mean trace length is only aspecial case of the proposed method. Specifically, the proposed method can besimplified as Kulatilake’s method when the four sides of the rectangular samplingwindow are considered to be the scanlines. The limitation of Kulatilake’s methodis limited spatial coverage. Hence, the results of Kulatilake’s method are not verystable and accurate in some cases.The proposed method has better spatialcoverage and therefore provides a better measure of trace length. The proposedmethod is verified with five simulated cases, and applied to a practicalengineering situation. The proposed method is shown to be more stable andaccurate than Kulatilake’s method.(2) The paper proposed a new method to estimate the probability density function oftrace lengths. Through simulated traces by exponential and lognormaldistributions, the proposed method is verified and the proposed method is shownto be more stable and accurate.(3) By establishing and solving discontinuities intersecting with scanlines,discontinuities intersecting with a rectangular sampling window anddiscontinuities intersecting with a cuboid spatial models, the rock discontinuitymean diameter can be obtained directly. In the practical rock engineering,sometimes the number of discontinuities intersecting with a cuboid is difficult tobe obtained. Hence, an approximate method by the situation of discontinuitytraces in the rectangular sampling window to estimate the number is advised forwide application of the proposed method. Finally, the proposed method is verified with a simulated case and applied to a practical engineering situation. Theproposed method is shown to be more stable and accurate than Kulatilake’smethod.(4) The discontinuity size and probability density function can be got and the resultsare applied to establish a three-dimensional network model of dam abutment rockmass in Songta hydroelectric station. And the connectivity rate of bottom slipsurface of dam abutment rock mass is the final result of this paper. Compared withthe connectivity rate in traditional method, the results in the proposed method hassome differences with them, but the maximum of the connectivity rate is veryclose.