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Mechanical precutting. A tunnel technique rediscovered
395A scree. Access for site investigation was limited and drilling through the scree to bedrock slow and difficult. Slope instability required rock fall protection be installed before overburden removal and portal construction could start. Rock between portals is classified using Q and R M R systems. Because of the clay joint fill, initial construction is by a hydraulic nose breaker, but drill and blast many be possible once the fissured zone is passed. Support and progress to date are described.
916506 Mechanical precutting. A tunnel technique rediscovered Walsum, E Tuan Tannlg V23, N5, May 1991, P60-62
Precutting, first used in the 1950s, was forgotten until applied in the 1970s in France. An arch shaped slot is cut ahead of the tunnel face using a machine similar to a giant chain saw. In soft ground this is filled with cement to form a preliminary arch support, beneath which excavation can take place. In harder ground, the slot acts as a vibration damper when excavating by drill and blast, minimising overbreak damage. In either case tunnelling can continue where cover is inadequate for conventional techniques.
916507 NATM ground support concepts and their effect on contracting practices Sauer, G; Gold, H
Proc 1989 Rapid Excavation and Tunnelling Conference, Los Angeles, 11-14 June 1989 P67-86. Publ Littleton: SME, 1989 Flexibility is the main advantage of the NATM over other underground construction methods. It can use different support concepts to adapt to changes in geometry and geologic conditions. The design phase is extended into construction, and in situ measurements applied in specifying support type for subsequent advances. Case examples are used to illustrate the diversity of conditions in which NATM can be employed. Contractual practices, in particular risk allocation between client and contractor, and tender details are discussed.
9165O8 Large cross section tunnels in soft ground Heinz, H; Eisenstein, Z Proc 1989 Rapid Excavation and Tunnelling Conference, Los Angeles, 11-14 June 1989 P94-109. Publ Littleton: SME,
1989 Many major underground excavations for transit systems include large cross sections at shallow depth in soft ground, which require staged construction. NATM techniques are widely applied. Typical excavation schemes for large cross section tunnels are described, with an overview of current practice. Empirical design recommendations are made considering various classes of ground conditions. Construction parameters and initial support requirements are discussed on the basis of examination of a catalogue of case histories.
Groundwater problems See also: 916092, 916370 916509 Prevention of water hazards in coal mines Milkowski, W
Colliery Guard V239, N4, May 1991, P112-116 Complicated hydrogeological conditions are found in Poland's Upper Silesia coal basin. Low strength, water bearing rocks overlie some seams and there are many water bearing fractures. Exploration methods suggested include rotary core drilling and seismic and resistivity surveys to detect water bearing and fractured zones. Drainage may control water flow in some cases. Sealing of headings by resin grouting and temporary support by freezing during development work are groundwater limitation methods used. 916510 Water control measures, North Shore Inline Interceptor Phase IA tunnel, Millwaukee water pollution abatement program Ramage, R; Olson, D J; Lutzenberger, T J Proc 1989 Rapid Excavation and Tunnelling Conference, Los Angeles, 11-14 June 1989 P129-148. Publ Littleton: SME,
1989 The 8.5km long, 9.8m diameter tunnel is being excavated by TBM in Silurian age dolomite, about 90m below ground surface. When the Waubakee Formation (thinly bedded and readily separable along partings) was encountered, increases in water flow of approximately 0.75 cubic m/min per 30m of tunnelling were found. Total inflow of 12 cubic m/min occurred 200m into the Waubakee, necessitating remedial measures, including increased pumping capacity, grouting ahead of the tunnel from the surface and the tunnel face, and panning to improve the environment for support installation.
Surface subsidence, caving and rockbursts See also: 916087, 916261, 916531 916511 Analysis of three-dimensional ground movements: the Thunder Bay tunnel Lee, K M; Rowe, R K
Can Geoteeh J V28, N1, Feb 1991, P25-41 The Thunder Bay tunnel, of 2.47m mined diameter, was driven by shield TBM at depth 10m in soft to firm silty clay and clay overlain by 7m of sand and silty sand. 3D settlement distribution and horizontal displacements at various distances from the face were monitored during driving. These measurements are compared to predictions of the three dimensional finite element code FEM3D, applied with soil parameters taken from stress-dependent triaxial tests. Overall displacements are in good agreement, suggesting the procedure is applicable to similar cases of soft ground tunnelling, provided reliable soil parameters are available. 916512 Outbursts and their causes in shaft sinking in stable rock (In German) Exner, K; Aldorf, J; Ciganek, J
Glackanf V127, NIl~12, June 1991, P480-484 Incidents during shaft sinking at two Czechoslovakian collieries are reported. At Frenstat, two shafts were sunk through 800m of overburden. At depth 778m in one shaft, the monolithic lining fractured at 660m and 120m of shaft fell in. A
© 1991 Pergamon Press plc. Reproduction not permitted
916506 Mechanical precutting. A tunnel technique rediscovered Walsum, E Tuan Tannlg V23, N5, May 1991, P60-62
Precutting, first used in the 1950s, was forgotten until applied in the 1970s in France. An arch shaped slot is cut ahead of the tunnel face using a machine similar to a giant chain saw. In soft ground this is filled with cement to form a preliminary arch support, beneath which excavation can take place. In harder ground, the slot acts as a vibration damper when excavating by drill and blast, minimising overbreak damage. In either case tunnelling can continue where cover is inadequate for conventional techniques.
916507 NATM ground support concepts and their effect on contracting practices Sauer, G; Gold, H
Proc 1989 Rapid Excavation and Tunnelling Conference, Los Angeles, 11-14 June 1989 P67-86. Publ Littleton: SME, 1989 Flexibility is the main advantage of the NATM over other underground construction methods. It can use different support concepts to adapt to changes in geometry and geologic conditions. The design phase is extended into construction, and in situ measurements applied in specifying support type for subsequent advances. Case examples are used to illustrate the diversity of conditions in which NATM can be employed. Contractual practices, in particular risk allocation between client and contractor, and tender details are discussed.
9165O8 Large cross section tunnels in soft ground Heinz, H; Eisenstein, Z Proc 1989 Rapid Excavation and Tunnelling Conference, Los Angeles, 11-14 June 1989 P94-109. Publ Littleton: SME,
1989 Many major underground excavations for transit systems include large cross sections at shallow depth in soft ground, which require staged construction. NATM techniques are widely applied. Typical excavation schemes for large cross section tunnels are described, with an overview of current practice. Empirical design recommendations are made considering various classes of ground conditions. Construction parameters and initial support requirements are discussed on the basis of examination of a catalogue of case histories.
Groundwater problems See also: 916092, 916370 916509 Prevention of water hazards in coal mines Milkowski, W
Colliery Guard V239, N4, May 1991, P112-116 Complicated hydrogeological conditions are found in Poland's Upper Silesia coal basin. Low strength, water bearing rocks overlie some seams and there are many water bearing fractures. Exploration methods suggested include rotary core drilling and seismic and resistivity surveys to detect water bearing and fractured zones. Drainage may control water flow in some cases. Sealing of headings by resin grouting and temporary support by freezing during development work are groundwater limitation methods used. 916510 Water control measures, North Shore Inline Interceptor Phase IA tunnel, Millwaukee water pollution abatement program Ramage, R; Olson, D J; Lutzenberger, T J Proc 1989 Rapid Excavation and Tunnelling Conference, Los Angeles, 11-14 June 1989 P129-148. Publ Littleton: SME,
1989 The 8.5km long, 9.8m diameter tunnel is being excavated by TBM in Silurian age dolomite, about 90m below ground surface. When the Waubakee Formation (thinly bedded and readily separable along partings) was encountered, increases in water flow of approximately 0.75 cubic m/min per 30m of tunnelling were found. Total inflow of 12 cubic m/min occurred 200m into the Waubakee, necessitating remedial measures, including increased pumping capacity, grouting ahead of the tunnel from the surface and the tunnel face, and panning to improve the environment for support installation.
Surface subsidence, caving and rockbursts See also: 916087, 916261, 916531 916511 Analysis of three-dimensional ground movements: the Thunder Bay tunnel Lee, K M; Rowe, R K
Can Geoteeh J V28, N1, Feb 1991, P25-41 The Thunder Bay tunnel, of 2.47m mined diameter, was driven by shield TBM at depth 10m in soft to firm silty clay and clay overlain by 7m of sand and silty sand. 3D settlement distribution and horizontal displacements at various distances from the face were monitored during driving. These measurements are compared to predictions of the three dimensional finite element code FEM3D, applied with soil parameters taken from stress-dependent triaxial tests. Overall displacements are in good agreement, suggesting the procedure is applicable to similar cases of soft ground tunnelling, provided reliable soil parameters are available. 916512 Outbursts and their causes in shaft sinking in stable rock (In German) Exner, K; Aldorf, J; Ciganek, J
Glackanf V127, NIl~12, June 1991, P480-484 Incidents during shaft sinking at two Czechoslovakian collieries are reported. At Frenstat, two shafts were sunk through 800m of overburden. At depth 778m in one shaft, the monolithic lining fractured at 660m and 120m of shaft fell in. A
© 1991 Pergamon Press plc. Reproduction not permitted