Title:
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The influence of fine platy particles on the behaviour of a rotund sand
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A recent investigation into the behaviour of gold mine tailings (Vermeulen, 2001) showed that the particle shape of the fines tailings is predominantly platy whilst that of the coarse particles are angular. Various researchers have demonstrated that platy particles markedly influence the behaviour of sand. Consequently, research has been undertaken to establish whether the platy fines might govern the behaviour of the mine tailings. A laboratory investigation was conducted on an artificial soil namely Soton Soil, of which the particle shape and relative particle sizes were similar to those investigated by Vermeulen (2001). The Soton Soil consisted of coarse rotund particles containing various amounts of platy fines in the form of mica. The compressibility, stiffness and shear behaviour of the Soton Soil were measured in the laboratory. Stiffness measurements included both small strain shear stiffness and Young's modulus. Although the former are commonly measured in the laboratory using bender elements, several uncertainties are associated with the technique. Consequently a bender element new configuration and novel interpretation technique was developed that yielded repeatable results. The observed behaviour of the Soton Soil was compared with the characteristic behaviour of mine tailings as documented in the literature, especially that by Vermeulen (2001). The mean diameter of the coarse rotund sand employed in the research was lmm whilst that of the mica 0.1mm. The relative sizes of the Soton Soil particles compared well with the gold tailings tested by Vermeulen (2001). The percentage of platy fine particles (mica) (by weight) present in the Soton Soil varied between 5% and 20% which falls within the typical range found in mine tailings. A good correlation was found between the mechanical behaviour of mine tailings and Soton Soil. The unique behaviour of the mine tailings might thus be attributed to the particle shape of the fines.
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