Mechanical Properties of Brown Coal under Different Loading Conditions
Publication: International Journal of Geomechanics
Volume 17, Issue 11
Abstract
The Latrobe Valley in Victoria, Australia has the largest brown coal deposit in the world, where large-scale brown coal mines were established in the early 1970s. The geotechnical stability of mining batters requires a comprehensive understanding of the mechanical behavior of the brown coal. Therefore, an experimental study was undertaken to evaluate mechanical properties of brown coal in different loading conditions. In doing so, effects of intermediate loading histories on the mechanical properties of brown coal in a multistep loading (ML), consolidated undrained (CU), triaxial compression (TC) test using a single specimen were evaluated. A set of single-step loading (SL) tests at different confining pressures, with postpeak ML with unload/reload cycles, were also performed. It was found that peak and residual strength and stiffness values and stress–strain relations of brown coal can be estimated accurately by a relevant ML test. Therefore, cyclic loading and accumulated irreversible axial strain do not have any significant influence on the mechanical properties of brown coal. By observing pore-pressure behavior of samples during SL loading, it was found that, with an increase in confining pressure, the amount of damage to the specimen as a result of axial loading decreases, and therefore, the sample experiences contraction even after the peak stress is achieved. The ML increasing-confining-pressure test was found to generate more accurate peak and residual strength values as compared with the ML decreasing-confining-pressure test. In addition, it was concluded that, during the ML decreasing-confining-pressure test, maintaining undrained conditions through the entire test will produce more accurate results.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The authors thank Amin Soltani, Ph.D. student, for his kind help in editing the paper and the figures.
References
Anderson, W. F. (1974). “ Technical note. The use of multi-stage triaxial tests to find the undrained strength parameters of stony boulder clay.” Proc. Inst. Civ. Eng., 52(2), 367–372.
ASTM (American Society for Testing and Materials). (1988). “ Standard test method for consolidated-undrained triaxial compression test on cohesive soils.” ASTM 4767 -88, Philadelphia.
Brown, A. (1969). “ Earth movement and batter stability in the Latrobe Valley coalfields.” M.Eng.Sci. thesis, Monash Univ., Clayton, VIC, Australia.
Brown, E. T. (1963). The engineering behaviour of Morwell brown coal, Dept. of Civil Engineering, Univ. of Melbourne, Melbourne, Australia.
De Beer, E. E. (1950). “ The cell-test.” Géotechnique, 2(2), 162–172.
Green, D. C. (1971). “ Aspects of the consolidation of Morwell brown coal.” Proc., 1st Australia-New Zealand Conf. on Geomechanics, Institution of Engineers, Melbourne, Australia, 119–126.
Kavvadas, M., Papadopoulos, B., and Kalteziotis, N. (1994). “ Geotechnical properties of the Ptolemais lignite.” Geotech. Geol. Eng., 12(2), 87–112.
Kenney, T. C., and Watson, G. H. (1961). “ Multiple-stage triaxial tests for determination c′ and α′ of saturated soils.” Proc., 5th Int. Conf. on Soil Mechanics and Foundation Engineering, Vol. 1, Dunod, Paris, France, 191–195.
Kim, M., and Ko, H. (1979). “ Multistage triaxial testing of rocks.” Geotech. Test. J., 2(2), 98–105.
Kovari, K., Tisa, A., Einstein, H. H., and Franklin, J. A. (1983). “ Suggested methods for determining the strength of rock material in triaxial compression: Revised version.” Int. J. Rock Mech. Min. Sci., 20(6), 283–290.
Mackay, R., Xue, J., Powrie, W., and Dent, B. (2012). “ A new ring shear apparatus for determination of the residual shear resistance of remoulded brown coal.” Aust. Geomech., 47(4), 79–84.
Raisbeck, D. (1980). “ Settlement of power station structures in the Latrobe Valley.” Proc., 3rd Australia-New Zealand Conf. on Geomechanics, New Zealand Institution of Engineers, 33–38.
Raisbeck, D., Newcomb, J., and Ferraza, A. (1984). “ Yallourn open cut, stability of permanent batters in the Hernes Oak and Yallourn township areas.” Rep. No. DD200, State Electricity Commission of Victoria Fuel Dept., Melbourne, VIC, Australia.
Rosengren, K. J. (1963). “ Consolidation of some Victorian brown coals.” Australasian Institute of Mineralurgy and Metallurgy, Carlton, VIC, Australia, 208, 157–93.
Skotnicki, A. L., and Raisbeck, D. (1985). “ Rep. on Yallourn Open Cut, earthmovement analyses for the western and northern batters.” Rep. No. GD32(2), State Electricity Commission of Victoria Design Engineering and Environment Dept., Melbourne, VIC, Australia.
Taheri, A., Sasaki, Y., Tatsuoka, F., and Watanabe, K. (2012). “ Strength and deformation characteristics of cement-mixed gravelly soil in multiple-step triaxial compression.” Soils Found., 52(1), 126–145.
Taheri, A., and Tani, F. (2013). “ Developing a damage model to simulate multiple-step loading triaxial compression tests in rocks.” Geotech. Geol. Eng., 31(2), 541–556.
Taheri, A., and Tani, K. (2008). “ Use of down-hole triaxial apparatus to estimate the mechanical properties of heterogeneous mudstone.” Int. J. Rock Mech. Min. Sci., 45(8), 1390–1402.
Taheri, A., and Tatsuoka, F. (2012). “ Stress–strain relations of cement-mixed gravelly soil from multiple-step triaxial compression test results.” Soils Found., 52(4), 748–766.
Taheri, A., and Tatsuoka, F. (2013). “ A new method to simulate stress-strain relations from multiple-step loading triaxial compression test results.” Geotech. Test. J., 36(6), 799–810.
Trollope, D. H., Rosengren, K. J., and Brown, E. T. (1965). “ The mechanics of brown coal.” Géotechnique, 15(4), 363–386.
Verheyen, T. V., and Perry, G. J. (1991). “Chemical structure of Victorian brown coal.” The science of victorian brown coal structure: Properties and consequences for utilization, R. A. Durie, ed., Butterworth-Heinemann Ltd., Oxford, U.K., 279–321.
Woskoboenko, F., Stacy, W. O., and Raisbeck, D. (1991). “Physical structure and properties of brown coal.” The science of Victorian brown coal structure, properties and consequences for utilization, R. A. Durie, ed., Butterworth-Heinemann Ltd., Oxford, U.K., 151–246.
Youn, H., and Tonon, F. (2010). “ Multi-stage triaxial test on brittle rock.” Int. J. Rock Mech. Min. Sci., 47(4), 678–684.
Information & Authors
Information
Published In
International Journal of Geomechanics
Volume 17 • Issue 11 • November 2017
Copyright
© 2017 American Society of Civil Engineers.
History
Received: Jul 2, 2015
Accepted: May 9, 2017
Published online: Sep 7, 2017
Published in print: Nov 1, 2017
Discussion open until: Feb 7, 2018
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.