Indraratna, B 1994, 'Geotechnical characterization of blended coal tailings for construction and rehabilitation work', Quarterly Journal of Engineering Geology, vol. 27, no. 4, pp. 353-361.
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Coarse and fine refuse is produced by various coal processing equipment. The relatively wet fine tailings have limited use in construction activities and they are generally pumped as slurries into tailings ponds. The coarse rejects have a greater engineering applicability and are utilized in the construction of tailings dams and mine access roads as well as for landfill and ballast. This study investigates the fundamental engineering properties of blended tailings, whereby appropriate fractions of flotation tailings are mixed with cyclone rejects to produce an acceptable construction or rehabilitation fill. In particular, a practical procedure to optimize the blended ratios, is proposed on the basis of fundamental geotechnical testing. The applications of relevent tests are described, including Proctor compaction, California Bearing Ratios, triaxial and consolidation tests. The results confirm that blending of fines with coarse rejects enables enhanced dry densities associated with reduced permeabilities, higher shear and compressive strengths, lower consolidation settlements and increased bearing capacities. The addition of a small quantity of cement (2-5%) further improves the engineering properties of the blended matrix. -from Author
Indraratna, B 1994, 'The effect of normal stress-friction angle relationship on the stability analysis of a rockfill dam', Geotechnical and Geological Engineering, vol. 12, no. 2, pp. 113-121.
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Accurate stability analysis must consider the variation of the angle of friction of rockfill with the confining pressure. In reality, with increasing depth of a rockfill dam, the apparent friction angle decreases, whereas near the surface it tends to be higher. Conventional methods which employ a constant friction angle throughout the depth of a rockfill shell often yield a lower factor of safety (conservative) for shallow slip planes. On the contrary, they produce a higher factor of safety for deepseated slips subjected to increased normal (confining) stresses. This paper compares the constant friction angle approach with the variable friction angle method based on the stability analysis of a large rockfill dam, and the associated practical implications are discussed. In the latter analysis, the effect of normal stress on the friction angle of rockfill is incorporated through experimental observations. © 1994 Chapman & Hall.
Indraratna, B, Balasubramaniam, AS & Ratnayake, P 1994, 'Performance of Embankment Stabilized with Vertical Drains on Soft Clay', Journal of Geotechnical Engineering, vol. 120, no. 2, pp. 257-273.
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Indraratna, B, Gasson, I & Chowdhury, RN 1994, 'Utilization of compacted coal tailings as a structural fill', Canadian Geotechnical Journal, vol. 31, no. 5, pp. 614-623.
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Detailed laboratory investigations were conducted on coal tailings produced at Westcliff Colliery, New South Wales, Australia. Geotechnical tests were conducted to determine the particle-size distribution, mineralogy, compaction characteristics, compressive strength (California bearing ratio), shear resistance, and collapse potential. The tests show that compacted tailings have good potential as effective fill for embankments, tailings dams, mine access roads, and pavements. Large-scale utilization of these tailings for rehabilitation of subsidence-affected areas and mine backfill is particularly encouraging. It is demonstrated that this waste material can be efficiently compacted to produce acceptable engineering properties over a wide range of water contents. Although the behaviour of one specific type of tailings cannot be generalized to the diverse composition of other coal tailings, the results of this study assist in the interpretation of geotechnical data associated with nonconventional fill. The use of geotextiles in the stabilization of tailings is presented. The effect of moisture content and the number of geotextile layers on the shear strength parameters is investigated, and the influence of geotextiles on the failure modes of triaxial specimens is also discussed. Key words : California bearing ratio, coal tailings, compaction, geotextiles, structural fill, triaxial testing.
Indraratna, B, Wijewardena, LSS & Balasubramaniam, AS 1994, 'Discussion: Large-scale triaxial testing of greywacke rockfill', Géotechnique, vol. 44, no. 3, pp. 539-543.
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Sheng, D, Axelsson, K & Knutsson, S 1970, 'Estimation of frost heave for stratified soil profile', GROUND FREEZING 94, 7th International Symposium on Ground Freezing, A A BALKEMA, LAB REG PONTS & CHAUSSEES, NANCY, FRANCE, pp. 129-141.
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An operational model for estimation of frost heave in field where stratified soil profile occurs is presented. The model is developed from the research model described and verified by Sheng and Knutsson (1993). Soil layers are first classified into frost-susceptible layers (FSL) or non-frost-susceptible layers (NFSL). In an FSL, both heat flow and water flow are considered and ice lensing can occur. In a NFSL, only heat flow is possible and no ice lensing is allowed. The governing equations for heat and mass transfer are established for the time period when the frost front is moving within FSL. Capillarity and unsaturation are also considered. The operational model is verified by field measurements of heave amounts. The computed values of heave are in good agreement with the measured data. The applicability of the model to solving practical problems is demonstrated through example problems. The effectiveness of the commonly-used insulating materials in reducing frost heave is evaluated. The differential frost heave caused by the snow cover on road shoulders is estimated, as a function of the snow thickness. The effect of the ground water table on frost heave is also studied.
