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Helms underground pumped storage project shaft development
39A
822175 HEIAMS U P ~ G R O U N D ~ STORAGE ~ DEVELOPMENT AIxlersen, S F Prom 5th Rapid Excavation amd Tunnelir~ Conf~ence, San Francisco, 3-7 May 1981, V2, P887-901. PUBI New York: AIME, 1981 Briefly outlines the location and design of the excavation for this ur~e~grou~ powerhouse. The u ~ of various equipment to sir~ the different shafts is described. 822176 LARGE U ~ G R O U ~ D OPENING MEASURED V ~ S U S PREDICTED ROCK D~D~4ATIONS Swee~, N F; Hovlar~, H J PrOC ~th Rapid Excavation and Tunneling Conference, San Frameisco, 3-7 May 1981, V2, P1~73-I~89. Publ N ~ York: AIME, 1981 A finite element analysis of the H e l m s P m n p e d Storage Project ur~ergrour~ powerhouse complex, California, USA, was p e r f ~ prior to construction. This provided infcrmat~ion on the predicted rock behavio~ imcluding a e f ~ t i o n s and the resulting state of stress. Results from the monitoring Iro~ramme were compared with the predicted deformations ami there was found to be good agreement.
In-situ stresses and stress around underground openings 822177 NEOTECTONIC STRES~S IN THE REGION CF THE MINE AT BLEI~RG, CA~INTHIA (IN GERMAN) Kohlbeck, F; Scheidegger, A E Rock Mech, VI~, NI, May 1981, PI-25 In situ stress measurements at the mine of Rleiberg show extremely high stress values. Calculations by the method of finite elements prove the existence of a neotectonic stress field. Joint orientation measurements are in accordance with the in situ stress measurements. The maximum pressure is directed ~W-SE. This conforms %o the character of the European neotectonic stress field. Relaxation phenomena on drill cores are found at a depth as low as 2~Om. The relaxations show only partly a logarithmic time dependence. The d e f ~ t i o n modulus ar~ Poisson's ratio vary by more than i00 per cent within distances of some cms. The same spread is found on the in situ stresses. In some samples, the in situ stresses approach the unlaxial rock strength. The inhomogeneity of the stress field and of the material causes parts of the rock to be near the state of failure. Therefore, slight char~es of the stress field give rise to rock bursts and microselsmic phenomena. Auth.
822178 GEOIECHNICAL DESIGN OF LARGE OPENINGS AT DEPI~ Hock, E Proc 5th Ral~d Excavation and Tunneling Conference, San Francisco, 3-7 May 1981, V2, PI167-I180. PUBl New York: AIME, 1981 Two types of failure have to be consldered in desigr~fng large openir~s. This paper briefly reviews structurally con%rolled failure due to discontinuity intersections. Stress iuduced instability, usually occurring at depth, is then cousidered and the ir~ormation needed to analyse these failures is discussed. This ir~ formation includes virgin stress cor~Itions, induced stress, the rock mechanical properties, influence of faults and groundwater conditions. An example is presented for the analysis of an underground excavation.
Surfzce subsidence and caving 822179 PENNSYLVANIA'S SUBSIDENCE-CONTROL GUIDELINES: SHOULD THEY BE ADOPTED BY OTHER STATEST Bise, C J Min Engng, V33, Nil, Nov 1981, P1623-1628 Subsidence is discussed in relation to vertical and horizontal displacement caused by urderground mining. The effect of pillar size ard opening width on vertical displacements is considered. Horizontal displacement (extension or compression) is seen as primarily responsible for surface structure damage. The guidelines are outlined: 4.6m offsets, 15 deg tangents, 6.1x9.1m minimum pillar ard 50 per cent recovery, downslope stability. It is concluded that the guidelir~s do not consider the effects of depth on subsidence dmmmge, arid selection of minimg methods, and dc not take into account lomgwall mining°
82218o STABILITY OF THE STRATA OVERLYING THE MINED-0UT AREAS OF THE CENTRAL WITWATERSRAND Hill, F G J S A~r Inst Min Mstall, vSI, N6, June 1981,
P1~5 -191 Re-clews the restrictions imposed by the South African Del~rtment of M i n e s (now the Departmen, of Mineral a~i Energy Affairs) on the surface use Of grourd that has been undermined at shallow depths. The reasons for the restrictions are discussed with reference to early departmental records on subsidence ar~ fracture of the surface. The effect of mining on the hangi~ll strata is then discussed. Results from survey programmes in 9 zones in the Witwatersrand, South Africa, are given. These were to monitor the subsidence above mired out ground to see whether the surface had stabilised after initial subsidence.
822181 PREDICTION OF VERTICAL DISFLACH~ENTS IN A SUBSIDI~ ELASTIC LAYER Savage, W Z Geophys Res Let,, VS, N3, March i~81, P195-198 Subsidence over an underground cavity is modelled by assL~ing the subsiding region to be an infinitely long elastic layer that rests on a rigid base and defcrms under its own weight into an openir~ under its lower surface. An approximate analytic solution based on Fourier transform methods is found for vertical displacements of the ground surface ar~ the roof of the openir~ when the layer thickness is much greater than the width of the openimg. This model differs from p~evlous ar~ytic models in allowing both the ground surface ard cavity roof to be traction free. The shape of the surface subsidence trough is found to be controlled by the ratio of the layer thickness to the width of the opening: as the value of this ratio decreases the subsidence trough narrows a~d a peripheral ridge forms. Auth.
Temporary and permanent supports 822182 WAY AHEAD - WITH CHOCK SHIELDS Collier I L Min Engr, VI41, N2~I, Oct 1961, P235-2~I Discusses the introduction of chock shield supports Into the Main Coal Seam at the Rawdon Colliery, Derbyshire, UK, which had been wcrked prevlously.
822175 HEIAMS U P ~ G R O U N D ~ STORAGE ~ DEVELOPMENT AIxlersen, S F Prom 5th Rapid Excavation amd Tunnelir~ Conf~ence, San Francisco, 3-7 May 1981, V2, P887-901. PUBI New York: AIME, 1981 Briefly outlines the location and design of the excavation for this ur~e~grou~ powerhouse. The u ~ of various equipment to sir~ the different shafts is described. 822176 LARGE U ~ G R O U ~ D OPENING MEASURED V ~ S U S PREDICTED ROCK D~D~4ATIONS Swee~, N F; Hovlar~, H J PrOC ~th Rapid Excavation and Tunneling Conference, San Frameisco, 3-7 May 1981, V2, P1~73-I~89. Publ N ~ York: AIME, 1981 A finite element analysis of the H e l m s P m n p e d Storage Project ur~ergrour~ powerhouse complex, California, USA, was p e r f ~ prior to construction. This provided infcrmat~ion on the predicted rock behavio~ imcluding a e f ~ t i o n s and the resulting state of stress. Results from the monitoring Iro~ramme were compared with the predicted deformations ami there was found to be good agreement.
In-situ stresses and stress around underground openings 822177 NEOTECTONIC STRES~S IN THE REGION CF THE MINE AT BLEI~RG, CA~INTHIA (IN GERMAN) Kohlbeck, F; Scheidegger, A E Rock Mech, VI~, NI, May 1981, PI-25 In situ stress measurements at the mine of Rleiberg show extremely high stress values. Calculations by the method of finite elements prove the existence of a neotectonic stress field. Joint orientation measurements are in accordance with the in situ stress measurements. The maximum pressure is directed ~W-SE. This conforms %o the character of the European neotectonic stress field. Relaxation phenomena on drill cores are found at a depth as low as 2~Om. The relaxations show only partly a logarithmic time dependence. The d e f ~ t i o n modulus ar~ Poisson's ratio vary by more than i00 per cent within distances of some cms. The same spread is found on the in situ stresses. In some samples, the in situ stresses approach the unlaxial rock strength. The inhomogeneity of the stress field and of the material causes parts of the rock to be near the state of failure. Therefore, slight char~es of the stress field give rise to rock bursts and microselsmic phenomena. Auth.
822178 GEOIECHNICAL DESIGN OF LARGE OPENINGS AT DEPI~ Hock, E Proc 5th Ral~d Excavation and Tunneling Conference, San Francisco, 3-7 May 1981, V2, PI167-I180. PUBl New York: AIME, 1981 Two types of failure have to be consldered in desigr~fng large openir~s. This paper briefly reviews structurally con%rolled failure due to discontinuity intersections. Stress iuduced instability, usually occurring at depth, is then cousidered and the ir~ormation needed to analyse these failures is discussed. This ir~ formation includes virgin stress cor~Itions, induced stress, the rock mechanical properties, influence of faults and groundwater conditions. An example is presented for the analysis of an underground excavation.
Surfzce subsidence and caving 822179 PENNSYLVANIA'S SUBSIDENCE-CONTROL GUIDELINES: SHOULD THEY BE ADOPTED BY OTHER STATEST Bise, C J Min Engng, V33, Nil, Nov 1981, P1623-1628 Subsidence is discussed in relation to vertical and horizontal displacement caused by urderground mining. The effect of pillar size ard opening width on vertical displacements is considered. Horizontal displacement (extension or compression) is seen as primarily responsible for surface structure damage. The guidelines are outlined: 4.6m offsets, 15 deg tangents, 6.1x9.1m minimum pillar ard 50 per cent recovery, downslope stability. It is concluded that the guidelir~s do not consider the effects of depth on subsidence dmmmge, arid selection of minimg methods, and dc not take into account lomgwall mining°
82218o STABILITY OF THE STRATA OVERLYING THE MINED-0UT AREAS OF THE CENTRAL WITWATERSRAND Hill, F G J S A~r Inst Min Mstall, vSI, N6, June 1981,
P1~5 -191 Re-clews the restrictions imposed by the South African Del~rtment of M i n e s (now the Departmen, of Mineral a~i Energy Affairs) on the surface use Of grourd that has been undermined at shallow depths. The reasons for the restrictions are discussed with reference to early departmental records on subsidence ar~ fracture of the surface. The effect of mining on the hangi~ll strata is then discussed. Results from survey programmes in 9 zones in the Witwatersrand, South Africa, are given. These were to monitor the subsidence above mired out ground to see whether the surface had stabilised after initial subsidence.
822181 PREDICTION OF VERTICAL DISFLACH~ENTS IN A SUBSIDI~ ELASTIC LAYER Savage, W Z Geophys Res Let,, VS, N3, March i~81, P195-198 Subsidence over an underground cavity is modelled by assL~ing the subsiding region to be an infinitely long elastic layer that rests on a rigid base and defcrms under its own weight into an openir~ under its lower surface. An approximate analytic solution based on Fourier transform methods is found for vertical displacements of the ground surface ar~ the roof of the openir~ when the layer thickness is much greater than the width of the openimg. This model differs from p~evlous ar~ytic models in allowing both the ground surface ard cavity roof to be traction free. The shape of the surface subsidence trough is found to be controlled by the ratio of the layer thickness to the width of the opening: as the value of this ratio decreases the subsidence trough narrows a~d a peripheral ridge forms. Auth.
Temporary and permanent supports 822182 WAY AHEAD - WITH CHOCK SHIELDS Collier I L Min Engr, VI41, N2~I, Oct 1961, P235-2~I Discusses the introduction of chock shield supports Into the Main Coal Seam at the Rawdon Colliery, Derbyshire, UK, which had been wcrked prevlously.