Variations on an NATM theme

Variations on an NATM theme

268A Underground construction methods 924484 Microtunneiling MARTA Isely, T Ci~ Engng, N Y V61, NI2, Dec 1991. P50-53 To extend the Atlanta Rapid Tra...

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268A

Underground construction methods 924484 Microtunneiling MARTA Isely, T Ci~ Engng, N Y V61, NI2, Dec 1991. P50-53 To extend the Atlanta Rapid Transit system, it was necessary to construct twin tunnels (50m long by 6.5m wide by 7m high) below a major roadway at cover depth 1,5-3.5m. Crown soils were sandy silt. A number of construction alternatives was considered: multiple pipe arch, jet grouted arch, jacked precast lining, ground freezing, and NATM. The multiple pipe arch technique was chosen, the pipes being installed using a microtunnelling machine with slurry soil removal and a jacking frame. Jet grouting was used to support the tunnel face ahead of excavation. 924485 Pilot tunnel: an economical technology? (In Italian and English) Antonioli, G Gallerie VI3, N35, 1991, P39-45 Costs of tunnelling by first driving a pilot tunnel by full face TBM then blasting for enlargement are compared to those for full face excavation by explosives. Data are presented for 12 tunnels using the pilot technique in a variety of rocks of general fairly good quality. These are examined against data for full face blasting, considering ventilation, removal of water, geological investigation, vibration levels, and progress rate. On the basis of the information presented, full face blasting is the preferred technique. 924486 State of development of boring of surface and blind shafts (In German) Henneke, J; Weber, W Gluckauf V127, N21/22, Nov 1991, P978-988 Raise boring is now the most widely used shaft boring technique, with over 200 drilling installations in use worldwide. Machines with torque up to 520 kNm and 9000 kN tensile force are available. Raises with length 500-1000m and diameter 4-6m are described. An improvement is combination of upward boring with downward reaming using a rodless shaft boring machine. Examples of this technique in coal measures and hard rocks are presented. Where cuttings are conveyed upwards, both rodless and rod-guided shaft boring machines can be used, although the former is still in its early stages of development. Air-lift drilling is still widely used in the USSR. 924487 Cellular arch technique for large-span station cavern Lunardi, P Tunn Tunnlg V23, Nll, Nov 1991, P23-26 A 22.8m span cavern is required as part of the Milan Rail Link. The shallow depth (minimum cover 4m) and unconsolidated nature of the ground preclude the formation of a natural soil arch or use of conventional pressure grouting. The construction technique adopted was that of the cellular arch. Horizontal reinforced concrete pipes have been jacked to form the basis of the support structure before excavation commenced. The semicircular cylindrical structure formed is capable of supporting the loads and generating an arch effect to ensure stability.

924488 Variations on an NATM theme Deinhard, M; Prinz, H; Zeidler, K Tunn Tunnlg V23, Nil. Nov 1991, 1'49-51 Although only 522m long, the Oberreiden road tunnel runs through a 120 year old man-made railway embankment, under a section of shallow sandy overburden, then on into Bunter sandstone. Conventional NATM was used in the sandstone. For the embankment section the barrel vault technique was used. A protective arch was formed by injecting grout into pre-installed horizontal manchette tubes. NATM tunnelling continued under this arch. In the loose sandy section, the doorframe slab method, a development of cut and cover, was applied. 924489 Development of the Hawker Siddeley Dosco microtunnelling system Washbourne, J Proe Tunnelling '91, London, 14-18 April 1991 P213-221. Publ London: Elsevier. 1991 Mierotunnelling techniques are being used with increasing frequency in trenchless construction in urban areas. A new system designed to extend the distance associated with microtunnelling projects is described. It has the boring head separated from the auger drive for diameter above about 500mm. Guidance, the cutterhead/crushing system, auger and slurry spoil removal capabilities, and the jacking station are described. Special high bentonite slurry lubrication has been developed which better protects the jacked sections. 924490 Reconstruction of London Underground's Angel Station Moriarty, J M; Cooper, M L Proc Tunnelling '91, London, 14-18 April 1991 P233-248. Publ London: Elsevier, 1991 Redevelopment of the 34m deep station includes a second tunnel and escalator access. The construction is in London Clay and clays of the upper Woolwich and Reading beds. Stepplate junctions were used to connect the new tunnel to the existing tunnel so as to allow running of existing train services. Because of the large numbers of tunnels of different sizes, hand excavation was used rather than shields. Face and crown were supported at all times. Manual and automatic monitoring of existing structures was used to ensure no damage was occurring. 924491 Submerged geo-spacing for compressed air energy storage in deep soft rock. Provisional study of feasibility relating to urban siting in future Hayashi, M Proc International Conference on Storage of Gases in Rock Caverns, Trondheim, 26-28 June 1989 P377-387. Publ Rotterdam: A A Balkema, 1989 Studies have been conducted for the design and excavation of sub-seabed spherical caverns beneath a deep shaft using robotic machines, including the application of the concrete lining. The proposed site lies in soft sedimentary rocks. The geomechanical considerations of the rock mass for the proposed site are presented. The stability of the excavations has been analysed by the finite element method. Following this analysis, detailed construction plans are presented.

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