Time-dependent rock-shotcrete interaction. A numerical shortcut

Time-dependent rock-shotcrete interaction. A numerical shortcut

115A 912415 Geomeehanical characteristics of a pulverised inlilling material of a shear zone Suorineni, F T; Tsidzi, K E N Proc International Symposiu...

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115A 912415 Geomeehanical characteristics of a pulverised inlilling material of a shear zone Suorineni, F T; Tsidzi, K E N Proc International Symposium on Rock Joints, Locn, 4-6 June 1990 P317-321. Publ Rotterdam: A A Balkema, 1990 Most economic minerals in Ghana occur in the Birmian system of rocks. Gold mineralization is primarily in phyllites and metagreywacke characterized by shear zones. The zones, from a few miilimetres to several metres wide, are infiUed with a friable, dark grey lustrous material, which can have significant effects on mine safety and ore dilution. Petrological examination shows the fill to be basically fine grained quartz coated with carbonaceous matter and some mica during mylonization. Shear properties are also described. 912416 Experience with weathering dolerite in sinking shafts OIdroyd, D C Proc Symposium on Rock Instability Problems in Mine Shafts, Potchefstroom,lO May 1990 P23-28. Publ Marshalltown: SA NGO RM, 1990 Dolerite intrusions occur frequently in Karoo sediments within which most of the economic coal horizons of South Africa are found. To a large extent these intrusions form competent rock types far stronger than the country rock into which they are intruded. Problems within dolerites arc usually caused by jointing and loose blocks so formed. In the metamorphosed and structurally disturbed region around dolerites, rock stability is reduced. Another phenomenon, the rapid weathering effects which are found within a small percentage of dolcrite intrusions, is discussed. Support solutions, geotechnical testing, and prediction methods to minimise problems arc considered. 912417 Countermeasures for safety construction of a tunnel originating combustible gas Sagawa, K; lto, N; Murano, S Proc International Congress on Tunnels and Water, Madrid, 15-18 June 1988 VI. P589-596. Publ Rotterdam: A A Balkema. 1988 Methane gas exceeding explosion limit density was met in construction of the tailrace tunnel of the Hondoji Power Station, Japan. Risk of high gas concentrations was considered small, but full precautionary measures were taken nevertheless. An exploration borehole ahead of the face was used to monitor and quantify gas inflow rates. Risks were minimised by ventilation, continuous monitoring, and adoption of minimum hazard drilling and blasting procedures. The safety systems installed after completion are also described.

Stresses around underground openings See also: 912314 912418 Time-dependent rock-shotcrete interaction. A numerical shortcut Pottier, R Comput Geotech V9, N3, 1990, P149-169 Rock-shotcretc interaction near a NATM tunnel face is governed by the nonlinear time dependent material behaviour of the shotcrete and the time dependent excavation process. Three dimensional finite element analysis with a time stepping

procedure is one approach to the problem, but is expensive and time consuming. An attempt is made to simplify the problem by analysing the influence of essential parameters in the rock-shotcrete interaction at an early stage and deriving a hypothetical modulus of elasticity of the shotcrete lining. An approximate solution may then be obtained using a 2D finite element analysis with no time stepping. 912419 Analysis of tunnel distortion due to an open excavation in jointed rock Carter, J P; Aiehossein, H Comput Geotech V9, N3, 1990, P209-231 Tunnel deformation due to the nearby excavation of a basement for a rock mass containing two orthogonal joint sets is examined. The boundary element formulation for plane problems in anisotropic elasticity is used for the analysis. Distortions of the tunnel as the basement is excavated to a range of depths can be predicted. The solutions are illustrated using data pertinent to conditions in the central business district of Sydney, Australia. 912420 Development at Selby Houghton, A Colliery Guard V238, N8, Aug 1990. P200-204 The Selby concept, with output from 5 mines delivered through 2 spine tunnels, required development of 25km of main spine tunnels plus 64km of face and gate roads. Geological problems, including shear zones and high in situ stresses, have been encountered. Face roadways are driven in the direction of maximum horizontal stress where practicable. Roof bolting was adopted after initial trials, resulting in earlier and more positive support, reduced costs and increased driving rate. Dummy (sacrificial) tunnels are Used to allow stress relief and protect mine roads. Details for each colliery are outlined. 912421 Analysis of tunnels built by the cut and cover method (In German) Duddeck, H; Stading, A Felsbau I/8, N3, Aug 1990, PIII-II7 Cursory examination suggests analysis of cut and cover tunnels should be simple as geometry, soil conditions, and loading conditions are precisely known. Further examination using finite element analysis, however, indicates only slight deviations from design assumptions can result in significant changes in forces and moments on the tunnel. An example of a twin track rail tunnel is presented. Parameters are varied within reasonable limits. Sensitivity of the basic values for lining design to these variations is large. 912422 Roadway support and design in the new UK coal industry Frith, R C; Reddish, D J; Watson, T P g i n Engr VI50, N349, Oct 1990. PI24-128 Finite element analysis has been used to study the influence of mine roadway shape on its stability. Increasing the width to height ratio decreases the compressive stress in floor and roof and the size of the destressed zone in the sidewall. This must be balanced against effects of decrease in confinement and increased self weight of the roof strata. Use of active support can minimise the latter drawbacks. Similar analysis is applied to sacrificial roadways. Contributions of shape, support, and in situ stress to stability should be considered together.

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