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Add to Alert PDF. The BSB used a full-face rotary cutterhead equipped with 56, Management 2 in. Drillhole surveys 1 Hendricks presents a detailed prediction of the per- Other inc. These include slip forming both bottom-up and top-down , jump forming, precast concrete cylinders, and remotely placed shotcrete. Finally, if ground conditions permit, First intro- may be used. Summary data for these case studies are presented in Table utilization. Penetration rate is, in turn, a function of the geology The equipment, shown in Fig.
Moss et al. Variations in average penetration controlled by the operator to provide the required penetration rates were smaller than expected and correlation with the index rate. Muck is removed into a pilot hole by scrapers located on was poor.
Several important observations were made as a result the cutterhead. The shaft lining is placed from work platforms of this case study: located above the gripper assembly providing a continuous exca- 1. Lower than predicted rates of penetration in clay were vationllining cycle. Services and support equipment are de- thought to be due to plugging of the bit.
Associated problems ployed using techniques traditionally associated with conven- included reduced mud circulation rates and poor control of shaft tional shaft sinking. In addition to the obvious differences in down-hole tools, 2. An increase in the rolling resistance when drilling in rock the V-mole requires a pilot hole for muck removal. The results of this study serve to illustrate the potential shortcomings in generic performance prediction systems. The operational penetration rate for a blind-shaft drilling project can System components and opera- hole components corrected for buoyancy from the drilling mud tional considerations are described below.
A generalized raise and imperfect hole cleaning Maurer, Table ConventIonal shaft to total project costs. It can readily be seen that the project costs collar excavation and lining techniques typically are used to are dominated by the acquisition and installation cost of the steel construct the raise collar.
The raise drill is positioned on a steel casing used for final lining. Blind-shalt-borer down-hole equipment courtesy: Robbins Co. It can be removed from the shaft, after the raise drill great care is taken to ensure that the pilot hole is drilled within and steel foundation are demobilized, using a small crane. Directional surveys are routinely A comprehensive paper by Worden provides a de- performed every 25 or SO ft 7.
A skid-mounted raise drill typically consists of a crosshead, Ground Support-Raises are commonly unlined since raise positioned between two cylindrical guideposts, and hydraulic boring is typically used in relatively competent formations.
How- rams that lift the head and apply thrust, via the drill rods, to the ever, if ground conditions or use dictate the installation of a final reaming head. Rotary motion is provided through a ring gear lining, there are a few rapid lining systems to choose from. A small proportion of The raise borer reaming head is transported underground raise-bored shafts have been excavated using an upward-drilled during drilling of the pilot hole. Underground set-up involves pilot hole with downward reaming to full shaft diameter.
The assembly and attachment of the reaming head to the raise drill advantage of reduced pulling capacity, associated with down- rods and preparation of the underground mucking system. Shaft size limitations in con- tor to provide optimum penetration for each stratum encoun- ventional raise boring are primarily associated with 'exponen- tered. As noted earlier in this chapter, practice involves maintaining the cutting pile flush with the mine the required torque is a function of the sum of the individual roof to reduce airborne dust levels.
Upper deck with Fig. Shaft boring machine, 20 to hydraulic and electrical panels 24 ft 6 to 7. Excavation of shaft diameters beyond the single- up to 32oo-ft m deep Schmidt and Fletcher, Many pass capability machine and drill-pipe capacity of onsite equip- of the early problems, typically associated with a protypical ment can be accomplished by reaming a smaller shaft with sec- method, have been resolved according to Schmidt and Fletcher ond-pass reaming to full size.
Reaming heads should be selected Outstanding issues, traditionally associated with large- to optimize the torque distribution and drilling load. Stabilizers diameter shaft construction, include excavation in poor quality are essential when second-pass reaming in longholes to prevent and blocky ground, presence of large groundwater influx, and drill string whip. Alternatively, the raise may be sequentially the impact of pilot hole accuracy on final shaft verticality.
This reamed in short sections. The two-stage sequential reaming head was first introduced in Blind Raise-boring-Blind raise boring, or boxhole drilling South Africa in as an alternative method of reaming larger- has been used in the South African goldfields to construct small- diameter, deeper shafts in hardrock.
In operation, the smaller diameter 5 to 6 ft [1. Raise boring can be conducted with a predrilled pilot This head is then retracted, and the remaining shaft area is hole or blind without pilot hole at advance rates between 4 and reamed by the larger head; this cycle is repeated until the raise 6 ft 1. The first sequential-head raise borer, using an 8-ft Raise-boring System Performance Estimation-System per- 2. For Areas Goldmine. Assume From Eq. Predicted performance of shaft boring machine after detailed breakdown of a raise-bore contractor's bid is presented Hendricks, Wirth V-mole-vertical mole after Raine, As previously noted, the and geohydrological conditions, design criteria e.
This analysis equipment, plus a determination of their relative impact on proj- may be supported initially by conceptual designs as described ect cost and schedule. Cost is nominally the overriding consider- in this section. However, a final decision should be made in ation; however, timing may be critical, and higher shaft construc- consultation with personnel experienced in the field application tion costs may be off-set by rapid access to the ore body.
The geotechnical Factors influencing the selection of each shaft construction data set required for shaft design and construction bid package method have been assembled and are presented in Table The site investigation program should incorporate a At a broad conceptual level, the blind-shaft drilling method is fully logged core hole located within one shaft diameter of the preferred for conditions where proposed shaft centerline. Note: a borehole on shaft centerline 1.
Freezing would be required for groundwater control dur- is preferred; however, the verticality of this borehole may impact ing conventional shaft excavation. This borehole 2. Shaft lining requirements dictate the use of a fully hydro- should be geotechnically logged e. Rapid access outweighs added cost. Disturbance of the surrounding rock is a prime criterion.
Samples may also 5. Access is not available for subsurface muck removal. Hydrogeologic data should be obtained by profiling the where borehole using a down-hole in line with drilling or straddle 1. Adverse impacts of groundwater inflow can be economi- packer test tool. Data analysis will provide the location and cally mitigated prior to construction e.
Redpath, 81 Norite, Gabbro 40, 2, 84 9. Redpath, 65 26, 1, 84 Redpath, 90 Fine-grained Calcite 14, 1, 1, 84 Redpath, 90 Quartz Diorite, Porphyry 34, 2, 96 Redpath, 90 40, 2, 96 Redpath, 90 20, 1, 1, 96 Redpath, 67 Silicified Limestone 44, 3, Redpath, Redpath, 70 Silicified Limestone 14, 1, Redpath, 65 Quartz Diorite 47, 3, Redpath, 90 Fine-grained Calcite 14, 1, Rock quality permits stand-up times compatible with the Under these conditions, raise drilling may offer a less costly V-mole's mining cycle.
Minimum disturbance of the surrounding rock is a prime criterion. Three rapid excavation systems are described in this seg- 7. Immediate access to drilled strata for geologic logging, ment, namely, full-face tunnel boring, mobile miners, and road- instrument installation, and testing is required. Data are included to 8. There are no existing mine openings BSB only.
Site conditions e. Access is available for setup and underground muck re- Full-face boring systems or TBMs have been in common use 3.
Geologic structure permits pilot-hole drilling to the toler- in civil tunneling for many years but are used less' frequently in ances required by the shaft designer. Nevertheless, TBMs in European coal mines 4. Design requirements e. Alternative raise boring methods after Friant et al. Equipment available for most required raise inclinations.
These experiences may the periphery of the cutter head, and muck is removed via a spur more widespread acceptance and utilization of this method central conveyor system. Preparations for TBM excavation typically ment and improved tooling have resulted in machines that are involve portal construction, placement of a concrete pad on capable of advancing large-diameter openings in strong igneous which the TBM will be assembled, and installation of support and metamorphic formations at rates that compete favorably, services and equipment.
Careful excavation, including the use of and in many cases exceed, conventional drill and blast methods. TBM excavation profile and minimize ground support requirements. A disadvan- is a continuous process, with cutting, mucking, and support tage of TBMs is their wide turning circle, although a range of installation proceeding concurrently.
As the cutting head rotates, mini-fullface machines are available that have smaller turning it moves forward, reacting against the grippers. The grippers are radii. The high initial cost of these machines is balanced by low repositioned periodically when they reach the limit of their running costs compared to drill and blast excavation systems. Robbins and Domag TBMs steer while boring of a hard-rock double-shield machine designed for use in using a floating main beam.
Mucking in the immediate vicinity of the face is done by The bridge conveyor allows access for track System components and operational considerations are described laying and service installation without" disrupting the mucking below. A generalized TBM equipment setup is shown in Fig. A variety of mucking systems can be used to haul Full-face boring machines consist used.
Adequate muck removal rates are critical to optimum face of a rotating cutting head. Advanced ma- The orientation of the TBM is controlled by the grippers, in chines are available on which the tool type can be changed and conjunction with a laser beam and microprocessor-controlled tool spacing varied. These developments have arisen from the guidance system. These allow precise positioning of the machine, need for machines that can cope with a variety of poor ground but problems may still be encountered in weak or soft ground in conditions.
The cutting head may be an open structure with which the effectiveness of the grippers is greatly reduced. In spoke-like cutting arms, or it may completely conceal the face these situations, 3-dimensional orientation control is facilitated except for muck-removal openings and access ways for tool by TBMs, that steer while boring. The trailing gear fol- and tools, and can be used with a forepoling arrangement.
Components, and their configura- the tunnel face. Reaction to this thrust is provided by grippers tion, are primarily a function of tunnel size and may include: mounted on the TBM body, which in turn react against the 1. Bridge conveyor required to transport muck from the tunnel sidewalls. Mucking is performed by buckets mounted on TBM to the muck cars. Dual-track rail system with remote muck car loading and handling for larger diameter tunnels.
Hydraulic power unit, transformer s , and trailing cable. Supply hoist for unloading and moving supplies. Rock drill for bolt installation , rock drill power unit, and rock bolt supplies storage. Mechanical shop and cutter and supply storage area. System components are briefly described below; more de- tailed descriptions and specifications are contained in the refer- ences cited at the end of this chapter. Various types of muck cars and trailing gear are available that facilitate continuous loading.
Additional details, regarding conventional muck haulage sys- tems, are presented in Chapter 9. Alternate muck removal systems, incorporating pneumatic or hydraulic transport of crushed muck, have been used in a small nUITlber of civil tunnel- ing projects. Ventilation System-The ventilation system typically con- sists of to in. The system is designed and deployed to max- imize the cross-sectional area available for mucking equipment and is normally configured to exhaust air to the portal Chapter Electrical System-The electrical system typically consists of a high-voltage feeder cable with stepdown transformers mounted on the trailing gear and at strategic locations along the tunnel to service ventilation fans, lighting, pumps, etc.
Chapter Total installed power requirements can be roughly approx- imated at twice the predicted TBM consumption. Rock support requirements Chapter Hard-rock TBMs are commonly equipped with a partial or slotted shield, and when support is required, conventional rock support methods are used. Both soft-rock and hard-rock TBMs can be equipped with a full shield and segmental linings installed.
As noted in These simplified formulas are consistent with the conceptual level planning approach incorpo- rated herein. However, the owner is well advised to maximize geotechnical data collection and interaction with the TBM man- ufacturer so that uncertainties in performance prediction.
System Utilization-TBM utilization is defined as the ratio of the productive TBM operating time to the total time available for tunnel drivage. An estimate of the machine cutting rate, derated for downtime using the system utilization factor, can therefore be used to provide an estimate of the project schedule. TBM system downtime has been analyzed extensively by Fig. Sequential reaming sequence after Nelson et al.
Risks can be offset by requiring manufacturers to bid cutter cost on a per foot meter basis. The following data apply to the construc- tion of a ft 7. Farmer Fe X 0. Raise costs as a function of diameter and torque modi- fied from Engineering and Mining Journal, Anon.
Conversion 0. Graham Fe X 0. Major collapses and large inrushes of mud and water, heavily squeezing 0. Case studies involving TBM excavation under 1. No labor required in ing in a controlled envi- ment. Considered to be shields. No operation of the shaft prior to shaft ronment. Considered the most dangerous of large moving equipment lining. Shaft size Depth is limited by skip- Limited by required depth, Nominally limited by avail- Limited by available equip- Required to be larger than hoist rope capacity.
Drilled shaft di- Short ft shafts diameter. Shaft depth Depth is limited by skip- Limited by required diame- Raise depths up to ft hoist rope capacity. See Table Shaft verticality Verticality can be con- Deviation can be esti- Shaft verticality is con- Shaft verticality is con- Verticality can be con- trolled within extremely mated from geological trolled by pilot borehole. Equal data. Difficult to main- Pilot hole accuracy con- However, offset reaming tight tolerances. The to or better than conven- tain an absolutely verti- trolled by directional sur- can be controlled by the most accurate shaft con- tional.
Suggested tol- practice. Design toler- tional control when fol- gard to verticality. Ground disturbance Minimal mechanical distur- Provides minimal mechani- Provides minimal mechani- Provides minimal mechani- Conventional drill-and- bance of shaft wallrock. Advance rate conventional shaft con- fph 5 ft dia. See ft dia. In gen- Table Operational considerations Groundwater Same techniques as con- Method provides superior Groundwater controlled by Large projected inflows re- Large projected inflows re- ventional sinking.
Final lining may be in- Final lining may be in- vation. May incor- tems available-see vation. Miscellaneous Requires existing under- Requires existing under- ground access. Other considerations Shaft outfitting If a final steel lining is in- Pilot hole deviation usually Outfitting in-line with exca- Outfitting in-line with exca- stalled, considerable prevents raises from be- vation and final lining if vation and final lining if time can be saved ing used for man or ma- required.
All furnish- ings can be aligned prior to welding to the down- hole liner assembly. Model Robbins hard-rock double shield Fig. This compares to a forecast rate of 55 fpd Isa mine, Australia. Con- 6. Improvements in cutterhead design Hurt et ft 3.
Redesign of the aI. Roadheaders offer a number of advantages over full-face tunneling machines, chiefly related to flexibility. Roadheaders can cut a variety of cross sections, limited only by the basic They are thus usable, for example, in room and pillar many years, and are known under a variety of names including operations.
Sectional view of tunnel boring machine. In- sequence of mining and mucking is followed. Also they have line heads rotate co-axially with the boom, and arcing forces lower initial costs than full-face machines. Latest Books Formulas Of Acoustics springer Hidden Terrors: The Truth Asia On Tour: Exploring How To Make And Epilepsy Board Quick Review Wendell Berry: Life And Concerto For The Left Origins, Imitation, Conventions: Representation On The Purity Of The World: A Brief African Ethics: Gky Traditional
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