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A mesoscopic model of sand-gravel stratum in Beijing based on fractal theory |
DU Xiuli,ZHANG Pei,JIN Liu,ZHANG Renbo |
(Key Laboratory of Urban Security and Disaster Engineering,Ministry of Education,Beijing University of Technology,
Beijing 100124,China) |
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Abstract The mechanical properties and deformation behavior of soil-rock mixture and underground structure in soil-rock mixture stratum are influenced by the particle size distribution. The mesoscopic structural characteristics of soil-rock mixture were analyzed based on the fractal geometry theory and the relationship between the quality-particle size grading curve and the fractal dimension was determined. The fractal analysis on grain-size of 34 groups of sand-gravel soil in coordinate system was conducted and the results indicated that the sand-gravel in Beijing has the characteristics of self-similarity. The range of the fractal dimension of sand-gravel in Beijing is 2.4–2.6. The variation of the quality-particle size grading curve with the fractal dimension and maximum grain size were analyzed,yielding some new findings regarding the mechanical behavior of soil-rock mixture. It is clear that the whole grading curve can be obtained by combining the fractal geometry theory and the laboratory test on grain size distribution. A program generating the model of sand-gravel stratum is compiled based on the Monte Carlo method using the sphere to represent the shape of stone. Then,3D numerical analysis on tunnel excavation were carried out.
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[2] |
MEDLEY E. The engineering characterization of melanges and similar block-in-matrix rocks(bimrocks)[ Ph. D. Thesis][D]. Berkley:University of California,1994.
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