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By John Kuyt, Zili Li, Michael Mooney, Michele Mangione

"INTRODUCTIONTwin bored tunnels are commonly used for a variety of road and tunnel projects throughout the world. A major component of these twin tunnel projects is the construction of connecting cross passages that provide emergency access between tunnels and space for tunnel service equipment. Cross passages can present significant geotechnical risk and technical challenges to a project – support systems must be considered for redistributing loads around the mainline tunnel openings and supporting new loading resulting from excavation activities. Additionally, cross passages pose risks to construction schedule and cost because of their sequencing at the end of construction, so mitigation of schedule overruns can be critical. By observing field instrumentation data records from completed projects, a betterunderstanding of the force development in each temporary structure can be achieved with indication of which structures are the most critical to support ground loads.This paper discusses the data obtained during the Brisbane Airport Link construction project, a road tunnel located in Brisbane, Australia. Strain gauge instrumentation data from the precast segmental lining and propped opening steel sets is presented with relation to the construction sequence and local geology. Interpretations and conclusions based on the observed trends are proposed, with several key mechanisms affecting the loading and unloading identified.Brisbane Airport Link Project OverviewThe Brisbane Airport Link project in Brisbane, Australia, connects central Brisbane to the airport located northeast of the downtown with over 7km of twin-bore road tunnels, two lanes each, with several caverns, interchanges, and access ramps constructed along the alignment to connect to other key routes in the city. The project was executed under a Public-Private Partnership (P3) scheme, funded and operated by the consortium BrisConnections. The main contractors were a joint venture of John Holland and Theiss, while the design was carried out by Arup and Parsons Brinckerhoff.Construction of the tunnels was conducted using a combination of 17 roadheaders and two 12.5m double-shield Herrenknecht TBMs [1]. The TBMs were used in EPB-type closed mode for the initial portion of their drive, starting at the northeast end of the alignment. Tunneling started in soft ground, weathered rock, and mixed face conditions initially, progressing to competent sedimentary rocks as the drive continued. Support was accomplished using a 12.1 m diameter steel fiber reinforced concrete (SFRC) segmental lining installed behind the TBMs in a 9 segments + 1 key arrangement. The innovative design of these segments is detailed in the paper by Harding and Francis [2]. Ancillary roads and underground interchange caverns were constructed by sequential excavation techniques using roadheaders, accounting for nearly half of the total underground excavations."

Jan 1, 2016

By C. Sun

The Leeville underground mine has been in operation since 2006 and currently produces 3,200 tons of ore per day with an average gold grade of 0.4 opt. The mine has a large horizontal extent of 2,500 feet by 500 feet and a vertical extent of 20 to 200 feet. High density of joints occurs within the host rock. Based on Rock Mass Rating and field observation, the Leeville ground conditions are characterized as poor to very poor. As such, heavy ground support is required for the mining operation in Leeville. Ore zones with a height in excess of 10 m (35 feet) are considered for longhole stoping. A typical stope measures 6.0 m (20 feet) wide, 30 to 55 m (100 to 180 feet, depending on the ground conditions) long and 10 to 30 m (35 to 100 feet, depending the thickness of ore body) high, yielding 10,000 to 20,000 tons when completed. Narrow ore zones, less than 10 m (35 feet), are mined using cut and fill. These drifts are 4.6 m (15 feet) wide by 4.6 m (15 feet) high. Based on the afore-mentioned poor ground condition, the establishment of a ground control monitoring system is key to operating both safely and successfully. The ground control monitoring system is composed of comprehensive instrument design and installation. Instruments include Multi-Point Borehole eXtensometers (MPBX) and Stretch Measurement to Assess Reinforcement Tension (SMART) cables. The monitoring system covers the mining zones and infrastructure openings. After about two year?s applications and measurements, useful data has been and continues to be collected to use in future stope and infrastructure structure design. The system provides the information making engineer and operation teams to do their job more confident and efficiency. Keywords: Ground control, Monitoring system, Long hole stope, Instrumentation.

Jan 1, 2009

By S.K. SHARMA, ANKUSH GALAV, G.S.P. SINGH

This paper proposes a hydromechanically coupled numerical modeling approach to quantify the influence of various parameters on the mechanical and hydraulic performance of protective water barrier pillars (PWBP). The results are validated for two case studies having pillar widths of 16 and 42 m at cover depths of 136 and 190 m and water heads of 25 and 141 m. The outcome can be significantly helpful in the rational design of these pillars in underground coal mines.

Mar 1, 2023

By Jr. Raleigh

Three run-of-mine bituminous coals, which ranged in rank from low volatile to high volatile A, were floated at nominal -28 mesh (590 µ m), -100 mesh (150 µ m), and -400 mesh (37 µ m) feed particle sizes with selected pyrite depressants and a dispersant. For the coals tested, pyrite and ash-forming minerals were usually rejected best at a -100 mesh feed particle size. Depressant additions tended to improve flotation selectivity between pyrite and coal. When joint dispersant-depressant systems were used at -100 mesh (150 µ m) feed particle sizes, the total sulfur content of the clean coal decreased further. For a comparable coal yield, less fuel oil collector was required for the flotation of -100 mesh coal than was required for the flotation of either -28 or -400 mesh feed.

Jan 1, 1990

By Adolf J. Jonaitis

Outokumpu developed TankCell flotation cell technology beginning in 1990, following 35 years of successful flotation cell experience and application. In 1994, Outokumpu proved favorable operating success of 100-m3 (3,500-ft3) TankCells for porphyry copper and zinc flotation. In 1995, evaluation of a 150-m3 TankCell led to the successful application of these large cells in several operations. More than 350 TankCells of 100 m3 and larger in volume have been installed and are in operation. Key features of the Outokumpu TankCell design will be described. In addition, discussion of operating data from various metallic mineral flotation operations worldwide will be presented. Large flotation cell development continues today, with operating cell volumes of up to 160 m3 (5,500 ft3) in operation.

Jan 1, 1999

By Colin Rawlings, Simon Pepper, Maria Karakitsiou, John Mathews, Peter Townsend, Russell Bowler, David Keeble, Christopher Darton, Scott Sadler

National Grid needs to maintain a connection between two existing electricity sub-stations (Beddington & Rowdown) in the Croydon (south London) area, and allow the replacement of two 275 kV cable circuits that are buried under roads. This is to be achieved using a single 400 kV cable circuit within a 10 km (6.25 mile) long, 3 m (9.8 ft) diameter high voltage cable tunnel which is being driven through water bearing Chalk, at depths ranging from 5 m (15 ft) to 80 m (262 ft), with four access shafts(12.5 m (41 ft) in diameter) ranging in depth from 10 m (31 ft) to 40 m (131 ft). The Chalk in this area acts as a source of public drinking water supply (PWS) and is protected by areas designated Groundwater Source Protection Zones. To minimise the groundwater risk the design and construction of the cable tunnel and shafts has paid particular attention to the construction materials used, including testing of these construction materials prior to use, developing construction methods (including the design of the Earth Pressure Balance TBM) and maintaining a groundwater monitoring & testing programme prior to and during construction to ensure the integrity of the Chalk aquifer is maintained as a drinking water source. This paper describes the tunnel &shaft design and construction in relation to these particular groundwater environmental issues which set new precedents for tunnel assessment, design and construction requirements in the United Kingdom.

Jan 1, 2007

By Miles L. Silberman

Three major suites of igneous rocks were erupted in the Great Basin in middle and late Cenozoic time. The first, most likely, resulted from sub- duction of a Pacific plate (Farallon plate) beneath the North American plate, resulting in eruption of andesitic rocks in the northern Great Basin between 42 and 43 m.y. ago. Between 34 and 17 m.y. ago, igneous activity migrated to the southwest, largely as eruption of volumincus rhyolite-quartz latite ash-flow sheets, ending about 17 a.y. ago with the onset of crustal extension and north-south-trending Basin and Range (rift) faulting. The second volcanic suite erupted between 17 and 8 m.y. ago in the northern Great Basin; is mostly basaltic or bimodal basalt-rhyolite. The third volcanic suite consists of andesitic and rhyolitic lavas and some basalt erupted between about 22 to 6 m.y. ago in the western Great Basin along the northwest-trending Walker Lane fault zone. Hydrothermal ore deposits are associated with all suites of igneous rocks, but the largest production has come from mines associated with andesitic rocks of the third (western Great Basin) suite. The oldest (34 to 42 m.y.) andesitic rocks (first suite) of the northern Great Basin have produced some large deposits; slightly younger silicic rocks of this suite are mostly barren. Many small ore deposits are associated with the 17- to 8-m.y.-old basalts (second suite) of northern Nevada.

Jan 1, 1976

By J. Launay

In order to control and dispatch the sewage water coming from 3 tunnels toward 2 downstream sewage tunnels, a large cavern has been excavated in a suburb of PARIS. Located at a depth of 47,00 m, it has been excavated using the NATM procedure through swelling clay, weathered sandstone, and marl and chalk. It is 16,50 m high, 12,40 m wide and 60, 00 m long, with an elliptical cross-section and its two ends are egg-shapped. The final lining of the cavern is composed of 30 to 40 cm of shotcrete, steel ribs and passive anchor bars. The excavation stages and related movements were surveyed by extensometers, pressure cells and convergence devices. The design, method of construction of the cavern and the results of the measurements made are commented.

Jan 1, 1989

By Mike S. Ness, Allan G. Provost

High speed drilling, mucking, and hauling equipment was used in driving approximately 2.16 km(7100 ft) of lower power tunnel in quartz diorite for the Tyee Lake Hydroelectric Project near Wrangell, Alaska. The .91 m(36 in.) guage rail mounted equipment included a Tamrock 2-boom electric/hydraulic drill jumbo, a Haggl and 8HR mucker , and 3 Hagglund 115C shuttle cars. Several other innovative techniques allowed maximum advance rates of up to 17.5 m/day(57ft/day) in the 3 m(10ft) horseshoe section. Average tunnel advance was approximately 11 m(day(35.4 ft/day). The primary difficulties preventing full utilization of the equipment potential were the operators' "learning curve", the need for complete retraining of all personnel in the new methods, and minor sections of faulted ground.

Jan 1, 1983

By Nilabjendu Ghosh, Satyendra Kumar Singh, Gautam Banerjee, Harshit Agrawal

High-production methods like longwall mining with hydraulic powered supports are necessary to increase underground coal production in India. Longwall mining had a mixed success record for Indian geo-mining conditions. In this paper, an analysis is presented to optimally design an array of chain pillars in multi-seam longwall mining panels in the deepest coal mine in India. The study found that a chain pillar of 80-m width and 195-m length is necessary for long-term stability without any reinforcement. It was also observed that an optimum chain pillar can be designed by providing suitable side reinforcement (side bolting) which will reduce the chain pillar dimensions to 55-m width and 160-m length. Optimum design of chain pillars will reduce the coal locked up in these chain pillars by ~ 77%. This will also reduce the gestation period of longwall mining panel development. This paper also evaluates the maximum tensile subsidence strain induced at the surface and finds that the values are within the safe working limit of 3 mm/m. Thus, this paper finds direct application in the design of future multi-seam retreating longwall mining panels in Indian geo-mining conditions.

By Nilabjendu Ghosh, Satyendra Kumar Singh, Gautam Banerjee, Harshit Agrawal

High-production methods like longwall mining with hydraulic powered supports are necessary to increase underground coal production in India. Longwall mining had a mixed success record for Indian geo-mining conditions. In this paper, an analysis is presented to optimally design an array of chain pillars in multi-seam longwall mining panels in the deepest coal mine in India. The study found that a chain pillar of 80-m width and 195-m length is necessary for long-term stability without any reinforcement. It was also observed that an optimum chain pillar can be designed by providing suitable side reinforcement (side bolting) which will reduce the chain pillar dimensions to 55-m width and 160-m length. Optimum design of chain pillars will reduce the coal locked up in these chain pillars by ~ 77%. This will also reduce the gestation period of longwall mining panel development. This paper also evaluates the maximum tensile subsidence strain induced at the surface and finds that the values are within the safe working limit of 3 mm/m. Thus, this paper finds direct application in the design of future multi-seam retreating longwall mining panels in Indian geo-mining conditions.

By Robin B. Dill, Mark Pelletier, Daniel J. Dobbels, Subodh Bhaumik, Daniel J. VanRoosendaal

Although primarily cut-and-cover excavations are required for replacement of the existing elevated I-93 interstate highway through the heart of Boston for the Central Artery/Tunnel (CA/T) project, some mined tunnel construction was also undertaken. The mined tunneling conducted was the 22-m-wide northbound roadway structure which passed below a 20-m-deep operating underground subway station that was built in 1913. The innovative underpinning scheme used to support the subway station during construction resulted in the successful mining beneath the subway station with negligible vertical settlement. Two grouting galleries were carefully mined below the subway structure, and pre-grouting of the granulary, pervious glacial soils and weathered bedrock was carried out from these galleries. The reinforced concrete walls of the underpinning structure were constructed within three stacked drifts that were sequentially mined below each grouting gallery. After 11 cross adits were mined between the grouting galleries, cast-in-place post-tensioned girders that spanned between the stacked-drift walls were constructed to support the subway station. The stacked-drift walls also provided lateral support for the 22-m wide by 29-m long by13-m high opening beneath the girders.

Jan 1, 2001

By R. D. Miller

Application of shallow seismic reflection to problems associated with mineral exploration, mine planning, abandoned-mine detection, and environmental evaluation has been successful in a variety of geologic settings. Increased dynamic range of recording equipment and decreased cost of processing hardware and software have made shallow seismic reflection a cost-effective means of imaging geologic targets significant to mining operations. Seismic data possess sufficient resolution in many areas to detect faulting with displacement of less than 3 m in coal seams as thin as 2 m at depths of 200 m. Subsurface voids associated with abandoned mines at depths of less than 20 m can be detected and mapped. Seismic reflection has been successful mapping disturbed subsurface associated with dissolution mining of salt Complex geologic features associated with deposition of various hydrothermal minerals have been effectively mapped with high resolution seismic reflection at depths from 80 to over 300 m. Faults in sulfur-bearing cap rock over salt domes have been accurately located, allowing improved efficiency of the dissolution mining process. Shallow high-resolution seismic reflection has the potential to significantly enhance the economics and safety of mine operations.

Jan 1, 1993

By Brian Fulcher

The Fort Lawton Parallel Tunnel was built in 1990 - 1991 by Morrison Knudsen Corporation (MK) as an integral part of Seattle METRO's planned expansion of the Westpoint Treatment Plant. The project included a concrete lined 2542 m (8,340 ft) long tunnel bored in sands and clays under the presence of methane gas and over 27.4 m (90 ft) of ground water table. The tunnel roughly paral¬lels an existing and still operating 3.65 m (12 ft) diameter tunnel originally completed in 1909. The parallel tunnel was constructed using a Lovat 4.72 m (15 ft-6 in) earth pressure balanced TBM with ribs and timber lagging as primary support. The tunnel alignment crossed under as much as 91.4 m (300 ft) of overburden as well as twin mainline railway tracks; terminating in a shaft adja¬cent to the Seattle ship canal. The project was completed in June, 1991 after a final "wet-tap" tie-in to the existing brick-lined sewer; over five months ahead of the contract schedule. This paper will describe the construction methods, job site conditions and difficulties encoun¬tered on this very challenging and successful project.

Jan 1, 1993

By J. G. Groppo, A. E. Bland, B. K. Parekh, W. F. Stotts

Many coal preparation plants discard fine coal (generally minus 100 mesh) because it is difficult to beneficiate economically. At the Kentucky Energy Cabinet Laboratory (KECL), the waste streams from several Kentucky preparation plants were evaluated for cleaning with counter-current column flotation. A series of performance evaluations were conducted using a 0.05 m (2 in.) internal diameter (I.D.) 7.9 m (26 ft.) high laboratory column. The objectives of these tests were to assess the performance in terms of recovery and percent ash in clean coal and to optimize the operating parameters relative to combustible recovery and grade. Refuse streams containing 30-50 percent ash were upgraded to 2-8 percent ash with Btu recoveries of nearly 90 percent. A pilot scale column flotation cell was installed at the Bell County Coal preparation plant. This pilot plant utilized a 5.79 m (19 ft.) high and 0.15 m (6 in.) I.D. column to verify the performance data of the 0.05 m (2 in.) I.D. column for two different waste streams. Performance evaluation and pilot plant testing results related to scale-up are discussed.

Jan 1, 1988

By Dennis Molvik, Roberto J. Guardia, Brad Cowles, Rick Andrews, Robert A. Robinson

A 220-meter (m) segment of the Henderson/ ML King Combined Sewer Overflow(CSO) consists of two 1.8-meter-inside diameter (I.D.) pipe-jacked tunnels that pass beneath Interstate-5 and the BNSF and UPRR railroads. A seismic tomography survey was conducted to develop a 3-dimensional profile of the tunnel zone and better define potential obstructions. The tomography was conducted through three 11 cm high-density polyethylene (HDPE) pipes installed in a triangular pattern around the future tunnel alignments using horizontal directional drilling methods. The pipe-jacked tunnels have been successfully completed, thus permitting a comparison between the predicted obstructions and those actually encountered. The top HDPE tomography pipe was also used to monitor settlements with an experimental horizontal profiler above the advancing tunnels during construction and located two areas of ground loss beneath I-5 that were subsequently grouted.

Jan 1, 2005

By S. Ersayin, I. Iwasaki

Application of a magnetic field was shown to be effective in controlling iron losses in pilot-scale cationic silica flotation in the processing of magnetic taconite concentrates. The design of a magnetic field distribution device and batch flotation test results using a 1.42m3 (50 cu. ft.) WEMCO cell are reported. Major losses of iron units in froth products were in the -25µm (500 mesh) fraction, and the application of a magnetic field decreased the flotation of fine magnetite, thereby improving the selectivity of separation. The “as received” sample was sufficiently magnetized and no further benefit was gained by magnetizing treatment. Selectivity was somewhat adversely affected by demagnetizing the sample, though its effect was minimal due to the magnetic field. The device is simple in construction, low cost and may be installed readily in existing equipment.

Jan 1, 2002

By Michael J. Friedel

The permeability and flow capacity in unsaturated media is investigated by the Bureau of Mines for application to in situ copper leach mining at the Cyprus Casa Grande mine site. Moisture retention properties are derived and combined with scanning electron microprobe data to characterize the mineralogy, texture, pore size, distribution, and permeability of the host rock. Finite element modeling is used to derive a saturated permeability, ambient degree of saturation, and assess various injection-recovery schemes. Recommended design modifications for optimization of solution distribution and maximum recovery from the rock matrix requires either (1) the injection pressures on the order of 1500 psi and recovery wells operating in a suction mode, or (2) performing permeability enhancement, through rubblization. By producing a maximum block diameter of 4 m, injection pressures can be reduced to 500 psi with improved recovery and containment of solutions.

Jan 1, 1991

By A. R. MacPherson

The procedure to arrive at an energy efficient autogenous grinding plant is carried out in the following steps: First Step - Determine power requirements to grind a particular ore. This work carried out on small samples ground in a 450 mm diameter Aerofall Hill and the results are checked against a standard Bond Index test. Second Step - A bulk sample from the ore zone is ground in a 1.8 m diameter pilot mill. This work is carried on until the power objectives as indicated from the first step have been realized. Third Step - Correlate the pilot mill data, with the data from the numerous samples ground in the small 450 mm mill and arrive at design criteria for the commercial plant. Ensure commercial mill design will be suitable to obtain similar results as those obtained in the pilot mill.

Jan 1, 1981

By S. R. Dismuke

Ore at the Magmont Mine in southeast Missouri is extracted by the room and pillar method on two and sometimes three horizons. In 1991, an innovative plan was formulated for recovery of high grade ore in pillars using cable bolts to accommodate spans of more than 27 m (90 ft). A test area was subsequently selected and a recovery plan developed. A cooperative rock mechanics study effort by COMINCO METALS, the U.S. Bureau of Mines and the University of Utah was later established. When initially opened in 1968, the planned production rate was about 1,000,000 tons per year. Due to declining reserves, the production rate was decreased to 630,000 tons per year in November 1992. Pillar recovery now accounts for approximately 40%-50% of the mined tonnage and plays a vital role in allowing Magmont to continue to operate.

Apr 13, 2011