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Shear Strength of Sand-Gravel Mixtures: Laboratory and Theoretical Analysis
Many natural slopes and rock fill structures are made of a mixture of dispersed rock fragments (gravel) and sand-size particles. To analyze the stability of such structures, the shear strength of the sand-gravel mixtures is needed. For this purpose, direct shear tests were carried out on mixtures of Ottawa sand (d50 = 0.59 mm) and fine gravel (d50 = 5 mm). The shear strength of the sand and the sand-gravel mixtures was measured under two normal stresses. These normal stresses were equal to 52 kPa and 103 kPa. During the tests, the initial void ratio of the matrix was maintained relatively constant at a value equal to 0.8. The concentration by weight of the gravel in the mixtures tested varied between 0 and 30%. These concentrations by weight correspond to a concentration by volume equal to 0 and 19.3%. The results of the direct shear strength tests indicated that the angle of internal friction improved with an increase in the concentration of the gravel in the mixtures. The angle of internal friction was equal to 40.40 for the sand alone. The friction angle increased to 46.90 for the sand sample with a concentration of gravel by weight equal to 20% (12.1% by volume). It was determined that the shear strength of the sand-gravel mixtures can be determined from the shear strength of the sand matrix alone and the concentration by volume of the gravel in the mixtures if one uses the equation: Sc = Sm (1+2.5 C). In this equation, Sc is the shear strength of the sand-gravel mixture, Sm is the shear strength of the sand matrix alone, and C is the concentration by volume of the gravel in the mixture. However, the validity of the equation has not yet been determined to be general and has only been shown to apply to the type and size of materials, stress conditions, and type of equipment used in the reported testing program.
Shear Strength of Sand-Gravel Mixtures: Laboratory and Theoretical Analysis
Many natural slopes and rock fill structures are made of a mixture of dispersed rock fragments (gravel) and sand-size particles. To analyze the stability of such structures, the shear strength of the sand-gravel mixtures is needed. For this purpose, direct shear tests were carried out on mixtures of Ottawa sand (d50 = 0.59 mm) and fine gravel (d50 = 5 mm). The shear strength of the sand and the sand-gravel mixtures was measured under two normal stresses. These normal stresses were equal to 52 kPa and 103 kPa. During the tests, the initial void ratio of the matrix was maintained relatively constant at a value equal to 0.8. The concentration by weight of the gravel in the mixtures tested varied between 0 and 30%. These concentrations by weight correspond to a concentration by volume equal to 0 and 19.3%. The results of the direct shear strength tests indicated that the angle of internal friction improved with an increase in the concentration of the gravel in the mixtures. The angle of internal friction was equal to 40.40 for the sand alone. The friction angle increased to 46.90 for the sand sample with a concentration of gravel by weight equal to 20% (12.1% by volume). It was determined that the shear strength of the sand-gravel mixtures can be determined from the shear strength of the sand matrix alone and the concentration by volume of the gravel in the mixtures if one uses the equation: Sc = Sm (1+2.5 C). In this equation, Sc is the shear strength of the sand-gravel mixture, Sm is the shear strength of the sand matrix alone, and C is the concentration by volume of the gravel in the mixture. However, the validity of the equation has not yet been determined to be general and has only been shown to apply to the type and size of materials, stress conditions, and type of equipment used in the reported testing program.
Shear Strength of Sand-Gravel Mixtures: Laboratory and Theoretical Analysis
Vallejo, Luis E. (author) / Lobo-Guerrero, Sebastián (author) / Seminsky, Leanna F. (author)
Geo-Congress 2014 ; 2014 ; Atlanta, Georgia
2014-02-24
Conference paper
Electronic Resource
English
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