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Abstract Semi-trace scanline survey is one of the most widely used method to measure discontinuity geometrical parameters in field，while it is hardly to find some correlative researches on discontinuity based on semi-trace scanline method in literature. Technique of determining probabilistic distribution of discontinuity trace length and estimating of mean trace length based on semi-trace scanline surveys was improved. By considering the influence of the discontinuity orientation，three new types of traces and scanline?s intersection probability models and one type of semi-trace length cumulative probability model were built. Hence the probability density functions of trace length and the value of mean trace length with the influence of joints? orientation were obtained. With different types of probability density functions of semi-trace length，the probability density function of trace length expressed with explicit formula by semi-trace length probability density function was determined. Then the geometrical parameters of Laohuzui rock slope discontinuities in Wenchuan area were used to prove the new method. Results of network were compared with the real measured semi-trace length sample. It showed that the average simulative semi-trace lengths from improved model were much closer to the field semi-trace length data than the results obtained by previous method，which indicated the superiority of the proposed method. Finally several suggestions about discontinuities sampling by using scanline surveys were given according to the analysis result of the relationship between the mean trace length and discontinuity orientation.
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Received: 05 February 2012
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2013, Vol. 32 
