913516 Modelling of outbursts at No 26 Colliery, Glare Bay, Nova Scotia. Part 2: proposed outburst mechanism and model Barton, K; Kullmann, D Min Sci Tedmol VII, N3, Nov 1990, P261-268

A mechanism is proposed to quantitatively model the previ- ously described outburst. Burst is treated as a series of instanteous static events driven by tensile failure within the rock mass around a spalling cavity. Stress redistribution caused by cavity shape change with spalling may result in ter- mination of the outburst, but the outburst may continue indeflnately until terminated by a change in geology. The main parameters influencing outburst are rock tensile strength and gas pressure. Final cavity shape depends on in situ stress field. Sensitivity analysis is presented to demonstrate these influences.

913517 Modelling of outbursts at No 26 Colliery, Glace Bay, Nova Scotia. Part 3: comparison of model results and field data Kullmann, D; Barton, K Min Sci Techaol Vii, N3, Nov 1990, P269-280

The previously proposed outburst mechanism is seen to rea- sonably simulate recorded events. Shape and size of the carl- ties predicted by the model are compatible with those found. A siltstone bed often occurs between the sandstone channel and the coal seam. If the sandstone is not penetrated, the silt- stone must fail prior to outburst in the sandstone. This is analysed as cutter roof failure of a beam loaded by gas pres- sure at the sandstone/siltstone interface. Potential remedial measures are discussed, the most important of which is thought to be early installation of active support as close to the face as possible.

913518 Innovative micro-seismic source location technique Ge. M; Kaiser, P K Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P43-50. Publ Rotterdam: A A Balkema, 1990

Monitoring of rockburst related seismic activity is routine in many mines to help assess stability of mine openings, evaluate preventative measures,and study causes of rockburst. An event based velocity model for source location is described, which is implemented with the GRC Source Location System, a computer code for analysis of MP250 microseismic monitor- ing system data. Applications are described, validation and accuracy discussed.

913519 Geomecbunical evaluation of escarpments subjected to mining induced subsidence Ahola, M P Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P129-136. Publ Rotterdam: ,4 A Balkema. 1990

The effect of extraction of Iongwall panels from a seam beneath massive sedimentary layers is examined using two dimensional boundary element analysis. Ground movements related to mining subsidence may destabilise jointed and weathered rock masses and promote sliding or toppling fail- ure. The procedure is illustrated for the Cottonwood mine, Utah, which underlies the Massive Castlegate Sandstone. Stress and displacement plots are presented, and effect of panel layout on slope stability examined.

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913520 Mechanism of caving in Iongwnil mining Salamon. M D G Rock Meclumics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P161-168. Publ Rotterdam: A ,4 Balkema, 1990

Longwali mining with caving is one of the more widely used extraction methods, but there has been little quantitative mathematical study of it. The caving and reconsolidation processes involved are examined first for the case of a reasona- bly uniform roof mass, one where each stratum readily con- forms with the deflection of its underlying layer, then for the case where a massive bed is present. Computer predicted con- vergences and settlements are compared to some field observations.

913521 Determination of an intensity function for subsidence prediction Triplett, T L; Yurchak, D W Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P169-175. Publ Rotterdam: A ,4 Balkema. 1990

Empirical profile functions or influence functions are widely used to predict subsidence over underground mines. Shape of the subsidence curve predicted by the profile function is lim- ited by the form of that function,hence the influence function is the more promising approach. Research by the USBM to modify the influence function for application in Illinois is described. Surface movement is considered the effect, extrac- tion at seam level a cause of certain intensity. An intensity field must be defined to represent the magnitude of these causes. It is demonstrated that accuracy of prediction is improved by inclusion of a reasonable intensity field.

913522 Violent stress relief of pillars due to blasting at Macassa Mine, Canada Jeremic, M L Strata Control in Deep Mines: Proc I Ith Plenary Scientific Session of the International Bureau of Strata Mechanics, World Mining Congress, Novosibirsk, 5-9 June 1989 P31-38. Publ Rotterdam: A ,4 Balkema. 1990

The Macassa mine lies in the Canadian Precambrian shield, and has quartz veins localized in silicified and carbonatised rocks. Elastobrittle behaviour is predominant. Extraction is mainly by cut and fill. Substantial energy can be stored in the ore blocks above the stope backs. Production blasting can supplement this to a sumcient level to initiate rockburst. Destressing using camouflet blasting is suggested as a means of rockburst control.

913523 Fault-slip rockbursts at the Falconbridge mine Hedley, D G F: Bharti, S; West, D; Blake, W Proc 4th Conference on Acoustic Emission/Microseismic ,4ctivity in Geological Structures and Materials, Pennsylvania, 22-24 October 1985 Pi59-170. Publ Clausthal-Zellerfeld: Trans Tech Publications. 1989 ~

Source locations from the mine microseismic network and vis- ual observations suggested a fault-slippage mechanism for the 20 June 1984 series of rockbursts. A circular fault model used to estimate stress drop,average slippage, and radius over which slippage took place predicted values respectively of I- 7MPa. 3-26mm. and 87-128m for rockbursts of magnitude 2.2-3.5. These are consistent with areal extent of damage seen, but slippage may be underestimated.

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