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Rapid method for an approximate assessment of the liability of coal seams to rock bursts (In Polish)
34A
79212~ T H ~ I C A L REMARK ON THE STRESS FIELD AROUND PRESTRESSED ROCK BOLTS WiJk, G Int J Rock Mech Min Sci, VIS, N6, Dec 1978 , P289-2~ The stress fi~Id in the rock aroumd a prestressed rock bolt is considered. It is shown that the stress field only a couple of hole diameters away from the bore hole is A1,~st identical to the imaginary, but m o r e easily calculahlej stress field that is created when there is no bore hole between the rock bolt forces. Auth. 792125 IN SITU STRESS D E T E ~ N A T I O N BY HYDROFRACTURING: A FRACTURE MECHANICS APPROACH Abou-Sayed, A S; Brechtol, C E; Clifton& R J J Geophys Res, V83, NB6, i0 Jkme 1978,~28512862 The in situ ~treas field was determined at a depth of 837 m in Devonian Shale in West Virginia. Logging data and laboratory observations of core samples reveal vertical cracks oriented at N 50 deg - 60 deg E. Because of these cracks and their preferred orientation a new aPlrOach based on fracture mechanics concepts is used to evaluate the in situ stresees from the field laboratory data. The resulting prediction of the maximmm horlzorf~al slm'ess is c c ~ e d to the m~xlmum horizontal stress predicted by Haimson and Fairhurst's (i~7) method: the latter method appears to overestimate the value of this stress component because the effect of loading the faces of any preexisting crack is neglected.
792126 AXISYMMETRIC D ~ I O N
792128 A m ~ I C ~ I O N OF = ~B~ST DEE~ES
~
~O (IN ~ )
RE~CH
TO G ~
Sieber s, U
Gluckauf, VlI3, NI8,
15 Sept 1977, P@99-903
Measures for preventing gas, coal ard rock outbursts are outlined. The directives considered cover methods of prediction ~ control of outburstsj add the action to be t a k e n when an outburst occurs. 792129 ROOF FALLS IN MACHINE HEADINGS (IN GERMAN) Zischinsky, U Gluckauf, VlI3, N17, i Sept 1977, P847-853 After describing the effects of roof falls in machine headings, t h e author discusses possible prediction techniques based on geological data or on experience in similar strata. 792130 D E S O ~ I C METHOD FOR D E N N I N G THE RISK OF GAS AND COAL OUTBURSTS (IN POLISH) Borowski, J Przeglad Gorn, V34, N3, March 1978, PI05-I09 Methods of determining the quantity and pressure of gas in coal h:B~e been developed, based on measurements of gas desorbed. Outbursts may occur where the content of desorbable gas is more than 4 cu m carbon dioxide per torme. The critical value of the desorption factor equivalent to the above quantitites was determined. A new desorbometer is described which can be used to monitor changes in the risk of outbursts as mining proceeds. 792131 RAPID METHOD FOR AN APPROXIMATE ASSESS~NY OF
OF AN ELASTIC MASS
CONTAINING. A HOLE Vasilev, V Z Soil Meah Found Engng, VI4, NI, Jan-Feb 1"977, P63-68 Derives expressions for all stress c~nponents and for elastic displacements in the case of an elastically isotroplc half sPace weakened by a hole. The results can be used in evaluating chamges in the stress state in ground or rock when drilling shsfts. 792127 GEOLOGICAL STRUC%K~RE OF STRATA AND THE OCCURRENCE OF GAS OUTBURSTS (IN GERMAN) Kowing s K Gluckauf, VII3, N20, 20 Oct 1977, P996-999 Discusses the geological factors which may affect gas bursts, namely depth, rank, type of formation, tectonic stresses, and the petrological form of the neighboring rock. The risk of outbursts is greater if there are dirt bands in the seam, since the coal can slide on these. Tectonically disturbed zones in seams containir~ more than 9 c u m of gas per tonne are especially dangerous. Tectonic stress is not necessarily an indication of the severity of outbursts. Gas and ear.stone outbursts do not depend on tectonic disturbance. Outburst-prone s a r d s T ~ n e s have a greater pore volume add lower stremgth than ram-real. Almost all o u t b u r s t s from the floor occur where the strata immediately below are impervious to gas and sandstone is present lower down.
~E
LI~Y
OF COAL ~ S
TO R O ~ BURSTS (ZN
POLISH) Kid~inski, A; Hladysz, Z Przegl Gorn, V34, N3, March 1978, PIIO-II2 There is an empirical correlation between the liability of a seam to rock bursts and the coal solid rebound ~ m b e r measured using Schuidt's hammer with a low impact energy. The m e t h c d , described replaces the laboratory method previously used. 792132 MECHANISM OF COAL AND GAS OUTBURSTS IN THE LIGIE OF RESULTS OF MEASUREMEBTS (IN POLISH) Tsr nuwski, J Przegl Gorn, V3~, N1, Jan 1978, PI-7 There is a depth below which the amount of energy stored in a seam exceeds the work required for destruction of the ribside coal mass. The sun of the pressure of the overlying rocks and the energy of the gas adsorbed on the coal exceeds the work necessary to break up the coal. Under these conditions the seam is in a state of unstable equilibrium add there is a risk of coal and gas outbursts. 792133 INFLUENCE OF THE KIND OF WORKINGS ON COAL AND
GAS ouTmmsT HAZARDS (IN POLISH) Szirtes, L Przegl Gorn, V34, NI, Jan 1978, P7-12 Three clasees of outburst occur: the first occurs in development work when traversing geological disturbances and opening the seam. The
79212~ T H ~ I C A L REMARK ON THE STRESS FIELD AROUND PRESTRESSED ROCK BOLTS WiJk, G Int J Rock Mech Min Sci, VIS, N6, Dec 1978 , P289-2~ The stress fi~Id in the rock aroumd a prestressed rock bolt is considered. It is shown that the stress field only a couple of hole diameters away from the bore hole is A1,~st identical to the imaginary, but m o r e easily calculahlej stress field that is created when there is no bore hole between the rock bolt forces. Auth. 792125 IN SITU STRESS D E T E ~ N A T I O N BY HYDROFRACTURING: A FRACTURE MECHANICS APPROACH Abou-Sayed, A S; Brechtol, C E; Clifton& R J J Geophys Res, V83, NB6, i0 Jkme 1978,~28512862 The in situ ~treas field was determined at a depth of 837 m in Devonian Shale in West Virginia. Logging data and laboratory observations of core samples reveal vertical cracks oriented at N 50 deg - 60 deg E. Because of these cracks and their preferred orientation a new aPlrOach based on fracture mechanics concepts is used to evaluate the in situ stresees from the field laboratory data. The resulting prediction of the maximmm horlzorf~al slm'ess is c c ~ e d to the m~xlmum horizontal stress predicted by Haimson and Fairhurst's (i~7) method: the latter method appears to overestimate the value of this stress component because the effect of loading the faces of any preexisting crack is neglected.
792126 AXISYMMETRIC D ~ I O N
792128 A m ~ I C ~ I O N OF = ~B~ST DEE~ES
~
~O (IN ~ )
RE~CH
TO G ~
Sieber s, U
Gluckauf, VlI3, NI8,
15 Sept 1977, P@99-903
Measures for preventing gas, coal ard rock outbursts are outlined. The directives considered cover methods of prediction ~ control of outburstsj add the action to be t a k e n when an outburst occurs. 792129 ROOF FALLS IN MACHINE HEADINGS (IN GERMAN) Zischinsky, U Gluckauf, VlI3, N17, i Sept 1977, P847-853 After describing the effects of roof falls in machine headings, t h e author discusses possible prediction techniques based on geological data or on experience in similar strata. 792130 D E S O ~ I C METHOD FOR D E N N I N G THE RISK OF GAS AND COAL OUTBURSTS (IN POLISH) Borowski, J Przeglad Gorn, V34, N3, March 1978, PI05-I09 Methods of determining the quantity and pressure of gas in coal h:B~e been developed, based on measurements of gas desorbed. Outbursts may occur where the content of desorbable gas is more than 4 cu m carbon dioxide per torme. The critical value of the desorption factor equivalent to the above quantitites was determined. A new desorbometer is described which can be used to monitor changes in the risk of outbursts as mining proceeds. 792131 RAPID METHOD FOR AN APPROXIMATE ASSESS~NY OF
OF AN ELASTIC MASS
CONTAINING. A HOLE Vasilev, V Z Soil Meah Found Engng, VI4, NI, Jan-Feb 1"977, P63-68 Derives expressions for all stress c~nponents and for elastic displacements in the case of an elastically isotroplc half sPace weakened by a hole. The results can be used in evaluating chamges in the stress state in ground or rock when drilling shsfts. 792127 GEOLOGICAL STRUC%K~RE OF STRATA AND THE OCCURRENCE OF GAS OUTBURSTS (IN GERMAN) Kowing s K Gluckauf, VII3, N20, 20 Oct 1977, P996-999 Discusses the geological factors which may affect gas bursts, namely depth, rank, type of formation, tectonic stresses, and the petrological form of the neighboring rock. The risk of outbursts is greater if there are dirt bands in the seam, since the coal can slide on these. Tectonically disturbed zones in seams containir~ more than 9 c u m of gas per tonne are especially dangerous. Tectonic stress is not necessarily an indication of the severity of outbursts. Gas and ear.stone outbursts do not depend on tectonic disturbance. Outburst-prone s a r d s T ~ n e s have a greater pore volume add lower stremgth than ram-real. Almost all o u t b u r s t s from the floor occur where the strata immediately below are impervious to gas and sandstone is present lower down.
~E
LI~Y
OF COAL ~ S
TO R O ~ BURSTS (ZN
POLISH) Kid~inski, A; Hladysz, Z Przegl Gorn, V34, N3, March 1978, PIIO-II2 There is an empirical correlation between the liability of a seam to rock bursts and the coal solid rebound ~ m b e r measured using Schuidt's hammer with a low impact energy. The m e t h c d , described replaces the laboratory method previously used. 792132 MECHANISM OF COAL AND GAS OUTBURSTS IN THE LIGIE OF RESULTS OF MEASUREMEBTS (IN POLISH) Tsr nuwski, J Przegl Gorn, V3~, N1, Jan 1978, PI-7 There is a depth below which the amount of energy stored in a seam exceeds the work required for destruction of the ribside coal mass. The sun of the pressure of the overlying rocks and the energy of the gas adsorbed on the coal exceeds the work necessary to break up the coal. Under these conditions the seam is in a state of unstable equilibrium add there is a risk of coal and gas outbursts. 792133 INFLUENCE OF THE KIND OF WORKINGS ON COAL AND
GAS ouTmmsT HAZARDS (IN POLISH) Szirtes, L Przegl Gorn, V34, NI, Jan 1978, P7-12 Three clasees of outburst occur: the first occurs in development work when traversing geological disturbances and opening the seam. The