- Title
- Unsaturated shear strength of coal mine spoil
- Creator
- Fityus, S.; Robertson, H.; Bradfield, L.; Simmons, J.
- Relation
- 6th International Conference on Unsaturated Soils, UNSAT 2014. Unsaturated Soils: Research and Applications (Sydney 02-04 July, 2014) p. 1335-1340
- Publisher Link
- http://dx.doi.org/10.1201/b17034-195
- Publisher
- Taylor and Francis
- Resource Type
- conference paper
- Date
- 2014
- Description
- Coal mine waste rock (spoil) is a weak granular material derived from rocks of sedimentary origin. There are plans for mining operations to construct piles of spoil up to 400 m high. Under the consequent burial stresses, the spoil materials undergo substantial compressions, characterised not only by compaction but also by particle breakdown/disintegration. This leads to significant decreases in void ratio with consequent increases in the degree of saturation (Sr) at constant water content. In this study, a series of direct shear tests was undertaken on a typical mine spoil derived from Permian-aged sandstones and mudrocks, compressed under stresses of 1 and 3 MPa, with water contents from 0 to 17%. The samples, with different water contents but compressed under the same stress, all attained similar void ratios, but with degrees of saturation ranging from 25 to 100%, and corresponding suctions from 140 MPa to 6 kPa. When sheared, these differences in suction produced a difference in measured shear strengths of up to 400%, with a consistent trend of decreasing shear strength with decreasing suction. By fitting the measured shear strengths to an extended Mohr-Coulomb shear strength framework, both φ and φ b are found to be highly non-linear and suction dependent. Interestingly, when shear strength is plotted against suction on a log scale, the relationship is approximately linear. There is an observed tendency for friction angles to decrease with decreasing suction, and this is shown to be consistent with values back-calculated from spoil pile failures, with the “unsaturated” value of 28° found in the literature being consistent with the values interpreted in this work.
- Subject
- coal mine spoil; shear strength; Mohr-Coulomb shear strength framework; suction
- Identifier
- http://hdl.handle.net/1959.13/1293690
- Identifier
- uon:18668
- Identifier
- ISBN:9781138001503
- Language
- eng
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