[1] Laboratory analysis of single-phase water and airflow through a real rock joint under increasing confining pressure was carried out in order to assess the linearity or otherwise of the Reynolds number (Re) versus pressure change relationship and to also test the applicability of Forchheimer's relation. These tests were conducted on a granitic specimen, 110 mm high and 55 mm in diameter, with a single natural fracture running the height of the specimen, which had a matrix permeability of approximately 10 À18 m 2 . The single-phase Re versus pressure change relationship using water was confirmed as being quadratic in nature. This same relationship held for single-phase airflow but only for confining pressures below around 2.0 MPa. At confining pressures !3.0 MPa the relationship shifted in form to a cubic fit. In analyzing the application of Forchheimer's transmissivity relation to single-phase water flow it was concluded that the model was appropriate for all tested confining pressures (0.55-3.0 MPa). When assessing its applicability to single-phase airflow, the model was only accurate at low-confining pressures (<1.0 MPa). Further, it was found that an increase in confining pressure shifted the Forchheimer's transmissivity curve downward.

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The stability of mine waste dumps is of critical importance and an issue, the mining industry of Goa, India is continually facing. The State of Goa receives high rainfall of around 3,000 mm annually. This heavy monsoonal rainfall is often believed to be the cause of dump slope instability. In light of several dump collapses encountered in the State and their damaging effects on both mine operations and local geo-environmental conditions, this paper examines their stability considering various geotechnical factors and the downstream environmental effects of a slope failure. The mechanical properties of dump waste material are reported at different compaction levels. The effect of these properties and changes in porewater pressure are specifically examined using limit equilibrium analysis. An empirical formula is developed relating dump height, material mechanical parameters and pore-water pressure to the factor of safety of the slope. It was found that the level of compaction experienced by the material had a significant effect on the factor of safety.

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