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Wallrock reactions to mining beyond a preconditioned zone at the star mine, Burke, Idaho
60A
Preconditionlr~ in 8 and 12 crosscuts on the 7900 level of the Hecla Mining Co's Star Mine involved about 7,232 feet of drillir~ ard the blasting of about 10,055 pomps of ~ explosives to precondition a block of ~ro~md aloDg the realm vein of about ~50 feet lomb, 50 feet above, and ~O feet below the level. The s l ~ t smour~ of seismic energy accoml~a~i~ the i~itial raiseup in the prmcouditioned stopes indicates that this precor£1itioming was successful. Continued moniturlng s h o u l d b e carried out to determine whether the prec~itionir~ remains effective over the le~Eth of time required fur the c~mpletion of m i n i ~ in a stope block. Avail: NTIS, Sprir~field, Va, 22161 USA (PB 81-21~983 ) 823091 WAIIROCK REACTIONS TO MINING BEYOND A PRECONDITIONED ZONE AT THE STAR MINE, BL~(E, IDAHO Blake, W US Bureau of Mimes report (~R 52-81, April
l~0, ~SP Rock precorditionir~ in advance of mir~r~ has been an effective means of rock-burst control based on the results of field demonstrations carried out on the 7700 level of the Hecla Mini~6 Co's Star Mine. Mini~g through the precolrlitioned zone was characterized by greatly reduced rates of released seismic energy ar~ no bumping cr rock burstiDg occurred within the preco~itioned zone. Mining above the ;reconditioned zone was characterized by greatly increased rates of released seismic energy and rock bursting, particularly where the vein became very narrow in waste zones. This increased incidence of rock bursting points out the need for ,tope precomdltloning to be carried out on an entire stope block basis. A~th. Avail: NTIS, Spri~6field, Va, 22161 USA
(FS 81-21~355)
82309~ DEPENDENCEOF SEIS~OAC(YJSTICAOTIVITYOF A COAL FACE ON MINING I~IENSITY (IN RUSSIAN) Ivanov, V S; Ivanova, G M UgOl Ukr, NI0, Oct 1980, P33"3~ Investigations carried out at the Donbass mines have shown a relation between seismic activity and intensity of miuiDg. It is then suggested that mor~tcrir~ seismic activity can be used to regulate face machine wcrkiD6 time to help reduce the risk of rock burst. 823093 MINING OF COAL SEAMS IN A SAFETY PILLAR UNDER A
LARGE I~DUSTRIAL PLANT ( ~ ~ S ~ ) Ligeza, J Z Ochr Terenow Gc~n, N~9, 1979, PS-8 8230~4 ANALYTICAL MOD~ING OF COAL MINE ROOF ~AVI(~R Ea1~a~l, R T US Bureau of Mines rel~srt OFR ~i-81, Oct
1978, 99P Using a finite element co~puter code developed far the Bureau of Mines to calculate roof sag, convergence, roof bolt load change, and standard engineerir~ property information, a comprehensive series of three-dlmensiorel calculations at three different sites in a rocm-and-l~llar coal mine were performed. The calculated results were then compared with experimental results obtained from an extensive in-slte field measurement programme. General agreement was obtained between the analytical amd field results showing
that three-a~-~nsional finite element modelling of mlniD6 can be an axtremmly useful tool for ur~lerstar~i~6 mine behaviour. A series of parametric studies were also performed that examined the effects of chamgimg the viscoelastic time l~rameters, varyi:~ the preload on the bolts, and chamgi~g the effective stiffness of the bolts. Auth. Avail: NTIS, Springfield, Va, 22161 USA (UCRL52586 )
823095 STUDY OF THE BEHAVIOR OF ~ O I / N D
OPENINGS DURING ~ CAVING 0P~RATIONS Barla, G; Boshkov, S H US Bureau of Mines report OFR 7~-81, June
1979, 4cop This report describes studies of the i~luence of block-cavlr~ operations on uA~der~our~ openIngs, ar~ attempts to correlate observed ~ v i o u r with mathematical models developed to explain this behaviour. The studies proceeded by obtainir~ in situ stress measmcements amd attemptiDg to relate the measured stress to field cor~itiorm by finite element modelli~. A principal objective was to develop the capability to predict ground movement based upon stress measurement and an aPl~Ol~iate model" however, predictive capability is stror~ly influenced by the proper choice of rock strength properties used i n the model, some conclusions in the repo~t~ particularly those relatiDg to stress distribution in supports, are potentially useful to mine designers. For example, a delay in support installation and better control of urdercuttlng c o u l d be b e n e f i c i a l durir~ mining by the blcck-cavir~ ~ e d . Auth.
Tunnels 823096 ON THE NON-LINEAR 'SQUEEZING' EFFECTS AROUND CIRCULAR TUNNELS Gieda, G Int J Num Anal Meth Gecmech, V6, N1, JanMarch 1962, P21-46 An ar~lysis is presented of the non-linear creep effects arour~ a deep circular tunnel driven in 'squeeziz~' grou~i. The time-dependent behsviour of the geotechnlcal medium is described by means uf a simple viscoplastic rheological model capable of aPl~oximati~6 l~imery, s e c o n d a r y and tertiary creep behaviours. It is shown that tertiary creep can be allowed for by providir~ a suitable law governing the variation of some material parameters (such as viscosity) with stresses and strains. The basic operations of the 'evolutive' procedure adopted fur time integration are outlined. The results of various finite element analyses are presented concerning both lined ar~ unlined cases. Far the lined cases the influence of the liner stiffness and of the time elapsed between the end of excavation and the liner installation is considered.
823097 SOIL MECHANICS ASPECTS OF SOFT GROUND TUNNELLING Hight, D W Ground Emgr~, V15, N1, Jan 1982, 1%-7 RepOrts an informal discussion by the British Geotechnical Society on a paper of the above title, by Dr J H Atkinson and Dr R J Mair (see item 324098).
Preconditionlr~ in 8 and 12 crosscuts on the 7900 level of the Hecla Mining Co's Star Mine involved about 7,232 feet of drillir~ ard the blasting of about 10,055 pomps of ~ explosives to precondition a block of ~ro~md aloDg the realm vein of about ~50 feet lomb, 50 feet above, and ~O feet below the level. The s l ~ t smour~ of seismic energy accoml~a~i~ the i~itial raiseup in the prmcouditioned stopes indicates that this precor£1itioming was successful. Continued moniturlng s h o u l d b e carried out to determine whether the prec~itionir~ remains effective over the le~Eth of time required fur the c~mpletion of m i n i ~ in a stope block. Avail: NTIS, Sprir~field, Va, 22161 USA (PB 81-21~983 ) 823091 WAIIROCK REACTIONS TO MINING BEYOND A PRECONDITIONED ZONE AT THE STAR MINE, BL~(E, IDAHO Blake, W US Bureau of Mimes report (~R 52-81, April
l~0, ~SP Rock precorditionir~ in advance of mir~r~ has been an effective means of rock-burst control based on the results of field demonstrations carried out on the 7700 level of the Hecla Mini~6 Co's Star Mine. Mini~g through the precolrlitioned zone was characterized by greatly reduced rates of released seismic energy ar~ no bumping cr rock burstiDg occurred within the preco~itioned zone. Mining above the ;reconditioned zone was characterized by greatly increased rates of released seismic energy and rock bursting, particularly where the vein became very narrow in waste zones. This increased incidence of rock bursting points out the need for ,tope precomdltloning to be carried out on an entire stope block basis. A~th. Avail: NTIS, Spri~6field, Va, 22161 USA
(FS 81-21~355)
82309~ DEPENDENCEOF SEIS~OAC(YJSTICAOTIVITYOF A COAL FACE ON MINING I~IENSITY (IN RUSSIAN) Ivanov, V S; Ivanova, G M UgOl Ukr, NI0, Oct 1980, P33"3~ Investigations carried out at the Donbass mines have shown a relation between seismic activity and intensity of miuiDg. It is then suggested that mor~tcrir~ seismic activity can be used to regulate face machine wcrkiD6 time to help reduce the risk of rock burst. 823093 MINING OF COAL SEAMS IN A SAFETY PILLAR UNDER A
LARGE I~DUSTRIAL PLANT ( ~ ~ S ~ ) Ligeza, J Z Ochr Terenow Gc~n, N~9, 1979, PS-8 8230~4 ANALYTICAL MOD~ING OF COAL MINE ROOF ~AVI(~R Ea1~a~l, R T US Bureau of Mines rel~srt OFR ~i-81, Oct
1978, 99P Using a finite element co~puter code developed far the Bureau of Mines to calculate roof sag, convergence, roof bolt load change, and standard engineerir~ property information, a comprehensive series of three-dlmensiorel calculations at three different sites in a rocm-and-l~llar coal mine were performed. The calculated results were then compared with experimental results obtained from an extensive in-slte field measurement programme. General agreement was obtained between the analytical amd field results showing
that three-a~-~nsional finite element modelling of mlniD6 can be an axtremmly useful tool for ur~lerstar~i~6 mine behaviour. A series of parametric studies were also performed that examined the effects of chamgimg the viscoelastic time l~rameters, varyi:~ the preload on the bolts, and chamgi~g the effective stiffness of the bolts. Auth. Avail: NTIS, Springfield, Va, 22161 USA (UCRL52586 )
823095 STUDY OF THE BEHAVIOR OF ~ O I / N D
OPENINGS DURING ~ CAVING 0P~RATIONS Barla, G; Boshkov, S H US Bureau of Mines report OFR 7~-81, June
1979, 4cop This report describes studies of the i~luence of block-cavlr~ operations on uA~der~our~ openIngs, ar~ attempts to correlate observed ~ v i o u r with mathematical models developed to explain this behaviour. The studies proceeded by obtainir~ in situ stress measmcements amd attemptiDg to relate the measured stress to field cor~itiorm by finite element modelli~. A principal objective was to develop the capability to predict ground movement based upon stress measurement and an aPl~Ol~iate model" however, predictive capability is stror~ly influenced by the proper choice of rock strength properties used i n the model, some conclusions in the repo~t~ particularly those relatiDg to stress distribution in supports, are potentially useful to mine designers. For example, a delay in support installation and better control of urdercuttlng c o u l d be b e n e f i c i a l durir~ mining by the blcck-cavir~ ~ e d . Auth.
Tunnels 823096 ON THE NON-LINEAR 'SQUEEZING' EFFECTS AROUND CIRCULAR TUNNELS Gieda, G Int J Num Anal Meth Gecmech, V6, N1, JanMarch 1962, P21-46 An ar~lysis is presented of the non-linear creep effects arour~ a deep circular tunnel driven in 'squeeziz~' grou~i. The time-dependent behsviour of the geotechnlcal medium is described by means uf a simple viscoplastic rheological model capable of aPl~oximati~6 l~imery, s e c o n d a r y and tertiary creep behaviours. It is shown that tertiary creep can be allowed for by providir~ a suitable law governing the variation of some material parameters (such as viscosity) with stresses and strains. The basic operations of the 'evolutive' procedure adopted fur time integration are outlined. The results of various finite element analyses are presented concerning both lined ar~ unlined cases. Far the lined cases the influence of the liner stiffness and of the time elapsed between the end of excavation and the liner installation is considered.
823097 SOIL MECHANICS ASPECTS OF SOFT GROUND TUNNELLING Hight, D W Ground Emgr~, V15, N1, Jan 1982, 1%-7 RepOrts an informal discussion by the British Geotechnical Society on a paper of the above title, by Dr J H Atkinson and Dr R J Mair (see item 324098).