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By Joshua Farmer, Mike Gianforte, Tao Jiang, William Gettings

The Two Rivers Water Reclamation Authority (TRWRA) in Monmouth County, New Jersey, is replacing its aging Pleasure Bay Interceptor (PBI) with a new 54-in interceptor in a 3,250-foot long 8 to 10-foot diameter tunnel and a new 50-mgd main pump station (MPS). A comprehensive phased geotechnical investigation was performed, including SPTs, CPTs and geophysics. A channel filled with soft marine sediments was identified. The tunnel is set in stiff to hard marine soil to enable using a less expensive open-face TBM. The thickness of tunnel cover under the channel is optimized through numerical analyses to avoid a deeper pump station yet maintaining tunnel stability with controlling seepage.

Jun 13, 2021

By N. Paas

Diesel powered equipment has been operated in underground coal for more than 50 years. According to the Mine Safety and Health Administration (MSHA), there are approximately 3,000 diesel units operating in underground coal mines in the United States. This number is expected to reach 5,000 diesel units in 250 coal mines by the year 2000. Also, there are approximately 5,000 diesel units operating in metal/nonmetal mines such as trona, potash and salt mines: and more than 3,000 diesel units operating in Canada. This increased popularity of diesel powered equipment over trolley wire, electric trailing cable or battery powered equipment is because of improved safety, greater mobility, higher productivity and increased power of diesel equipment.

Jan 1, 1997

By E. Galán

The largest Spanish kaolin deposits formed on granites occur in Galicia (NW Spain) due to a widespread kaolinization of Variscan granitoids. This paper provides insight of the origin of this kaolinization process on the basis of a mineralogical and geochemical study carried out in two kaolin deposits, presently mined to be used in the paper industry. Mineral composition of the deeply kaolinized rocks is dominated by well-ordered kaolinite with minor quartz, K-feldspar, mica (illite/muscovite), locally gibbsite, and traces of resistant accessory phases (rutile, ilmenite, zircon and monazite). The content and structural order of the kaolinite decrease with depth. Kaolinite formed by extensive replacement of feldspars (plagioclase). Differential mobilization of major and trace elements during kaolinization has been inferred by using a mass-balance approach. Significant amounts of Na, Ca and minor Mn, Sr, P and U were removed from incipiently leachable minerals (plagioclase and apatite), and K, Rb, Cs and Ba were released from K-feldspar and mica. On the contrary, Ti, Zr, Th, Hf and the REE are retained in the resistant trace minerals that are concentrated in the fine fractions of the kaolins.

Jan 1, 2010

With mine activity dating back to 1792, the Lehigh Valley, about 80 km (50 miles) northeast of the historic Allentown/Bethlehem steel mills and about 160 km (100 miles) northeast of Philadelphia, PA, defined early-day coal mining. Coal mining began just nine years after the end of America?s Revolutionary War. The high-carbon, clean-burning anthracite coal that was hand-dug from the Pennsylvania hills fueled the steam engines that powered the Industrial Revolution, helping build early steam ships and even the first automobiles. Around 1910, at the peak of the U.S.?s early mining effort, there were more than 250,000 men working underground ? 10,000 of them in the Lehigh Valley.

Jan 1, 2012

By Richard Kastner, Emilie Vanoudheusden, Fabrice Emeriault, Jacques Robert

INTRODUCTION The subway line B of Toulouse (France) has been realized with three different tunnel boring machines (TBM) techniques: Contracts 2 and 5 are excavated with earth-pressure balanced TBM, Contract 4 with a slurry shield TBM, and Contract 3 with a compressed-air TBM. The first three machines are around 7.7 m in diameter, while the last one is 5.3 m. Moreover, a small part of the line (50 m) has been excavated by a conventional method. The tunnels run through the Toulouse molasses, composed of hard sandy clay with pockets and lenses of dense sand. Geotechnical investigations have shown that in these formations, K0 is greater than 1, around 1.8 at a depth of 25 m (Serratrice,2005) and that geotechnical characteristics are homogenous on the whole layout (? =22 kN/m3, Su = 300 kPa, c' = 30 kPa, F' = 32°). The water table is found between 2 and4 m below ground level. As geology, stratigraphy and tunnel cover (between 10 and 20 m) are almost identical, a comparison of movements induced by the excavation by each of the four excavation techniques is possible. This paper presents the soil mass movement measures in the case of the conventional excavation method and in the case of TBM sections. It shows how tunneling parameters may explain the different surface movements observed during excavation. For the sake of simplicity, only the results of Contract 2 (earth pressure balanced TBM)will be presented. MONITORING Monitoring for the Conventional Method Section For the conventional method section (Vanoudheusden et al. 2005) the mass soil movements are measured with two inclinometers and one multi-point extensometer borehole with automatic data acquisition (Figure 1). The monitoring devices include

Jan 1, 2007

By B. Beatty

Discussion by B. Beatty This is a response to M.J. Hrebar's paper, which tracks in detail the highly productive stripping capabilities of modern large bulldozers at two separate installations. It proves the old adage "economies of scale" and quantifies the advantage of being able to move large loads of dirt over comparatively short haul distances by sliding rather than carrying the load. This discussion examines whether a bulldozer is the most efficient way of using this geotechnical principle. Case 1 - Study eastern US: Contour coal stripping application The energy consumption for the Case 1 mining method (eastern US contour stripping operation) shows the D11 averaged 117 L (31 gal) of diesel fuel per scheduled hour, and produced 333.3 bank m3 (436 bank cu yd) per scheduled hour (0.351 L/m3). Assuming 1 L (0.26 gal) of diesel fuel contains 10.4 kW-hr of energy, the unit expenditure of fuel energy for Case 1 Study was 3.66 kWh/m3. Another way of shifting this material is by using an overburden slusher (OS), as shown in Fig. 1. The OS as shown in Fig. I. The OS is electrically powered and consists of a manned low wall winch (LW ), a remote controlled (radio telemetry) highwall winch (HW) and a hoe. The winches operate to pull the hoe back and forth across the pit. The hoe carries load in the forward direction ahead of a rear mounted blade and returns empty. A spreadsheet (Lotus 123) simulation package, BOSSIM, models the OS operation on a load by load basis over a wide range of pit configurations. The geometry shown in Fig. 2 of the paper was modeled using BOSSI M and the results are summarized in Table1. Table 1 shows a LW with 150 kW (200 hp) and a HW of 120 kW (160 hp) installed power, towing a 15-m3 (19-cu yd) hoe, would accomplish the Case 1 stripping task at about the same scheduled stripping rate (D11=333 m3/hr or 433 cu yd/ hour, OS=342 m3/hr or 447 cu yd/ hour). It was assumed the winches in this equipment have an electromechanical efficiency of 90%. This gives an average electrical energy expenditure rate of 151 kW-hr, and a unit energy expenditure level of 0.44 kWhr/m-3(0.57 cu yd/kWh)-an improvement of 8291%- over the D11 alternative. The energy comparison illustrates the importance of using more efficient electric power if possible, ahead of the internal combustion engine, and delivering power from a fixed ground position rather than through a moving track system. Another important energy observation is the comparative action of the dozer blade and the OS hoe. The former implement continuously digs and spills as it works the load forward. The OS hoe digs the load until full, the blade then lifts due to the contained load pressure and a shear plane forms under the mass, enabling it to slide forward in a force reduced - transporting mode. Economic comparison Table 2 operating cost per scheduled hour and unit cost comparison follows a format used in Tables 2 and 3 of Hrebar's paper and compares Case 1 Study with the OS alternative. Drill and blast costs are kept constant in both cases, although when larger OS units are considered, it is expected these costs will reduce because bigger hoe sizes will permit larger rocks to be transported efficiently.

Jan 1, 1995

By O. K. Olawale, G. O. Edaogbogun, B. N. Ben‑Festus, F. Ben, F. R. Amodu

The environmental and health implications of artisanal gold mining activities at mining sites across Nigeria have rekindled research interest. This study aimed to assess the scalability of naturally occurring radioactive materials in gold mining sites in Iperindo, Nigeria. Soil samples were collected from three different mining sites and control locations and analyzed for natural radionuclides, mainly 238U, 232Th, and 40K, using gamma spectrometry having a sodium iodide detector. The average activity concentration values of 61.55 ± 3.71, 72.65 ± 4.45, and 1134.99 ± 38.12 Bqkg− 1 obtained from within the mining sites for 238U, 232Th, and 40K, respectively, were above the world permissible values of 33.0 Bqkg− 1 for 238U, 45.0 Bqkg− 1 for 232Th, and 420.0 Bqkg− 1 for 40K. The average activity concentration values of 15.26 ± 3.19, 21.46 ± 4.27, 381.04 ± 23.36 Bqkg− 1 estimated for 238U, 232Th, and 40K, respectively, for the control location were, however, lower than the global permissible values. The study also evaluated other radiological parameters such as radium equivalent, dose rate, annual effective dose rate, internal and external hazard indices, and alpha and gamma indices. The obtained values were 252.83 Bqkg− 1, 119.98 nGyh− 1, 147.15 mSvy− 1, 0.85 Bqkg− 1, 0.68 Bqkg− 1, 0.31 Bqkg− 1, and 1.89 Bqkg− 1 respectively. Except for radium equivalent, external and internal hazard risks, and alpha index, which were significantly lower than the recommended threshold, all other radiological parameters were higher than the recommended global limits. Moderate data reproducibility and a p-value of 0.000574 further reinforced the robustness and reliability of the results obtained in this study.

Feb 22, 2024

By Steve Skelhorn

Edmonton South LRT is the latest expansion of the Subway system in Edmonton, Alberta, Canada: Consisting of twin 5.8m segmental lined tunnels, 280m long, driven by a Lovat EPB machine. The key challenges were as follows. A 6% downhill grade. Tight radius curves of 250m.Overlying structures within 3m of the tunnel. Strata consisting of sand above the water table, glacial tills and bed rock below the water table. Located within The University of Alberta Campus and adjacent to a hospital. Northern Alberta climate with winter temperatures routinely falling below—minus 30 degrees Celsius. This paper provides a case history and outlines the challenges involved in completing this project.

Jan 1, 2005

Microprocessor-based balances are helping Keffler & Rose Coal Preparation Co. to test and ship coal faster than the competition. They provide a high level of accuracy in meeting Environmental Protection Agency standards and customer specifications .and help minimize "bad" coal. The combination of speed and accuracy has helped increase K&R's sales, while improving the company's reputation for meeting precise client requirements. The quality of coal that is assured by the company's testing-at an in-house lab using fast, precision weighing, and a computerized sulfur test-has assured K&R of a good price for its products. Recent EPA standards have strained the testing capabilities of coal suppliers. Companies involved with high-sulfur coal often use outside laboratory services that can take three to four days to report test results. Since the coal business moves much faster these days, some coal companies cannot afford that kind of time. Too much coal not up to specifications could be produced within a three or four day period. Keffler & Rose took a novel approach to this problem, installing its own in-house laboratory. The test situation immediately improved with this step. However, one bottleneck persisted for a time: the weight measurement procedure for ash, moisture, and energy content. The company first employed a mechanical balance that required time for setting up and taring. The balance provided readings on a conventional scale that was not very precise and allowed for error through subjective readings by the operator. The balance bottleneck was broken when K&R applied new technology to meet its needs: microprocessor-based weighing. The result has been a 75% reduction in weighing time and a sharp increase in accuracy. This has contributed to the test speed needed to keep up with 227-t/h production and precise K&R coal specs.

Jan 11, 1980

By Erik Westman, Brandon Stables, Benjamin Mirabile

"Standing support is often used in conjunction with underground retreat mining. Knowledge of the load-displacement behavior of standing support and loading induced by the mine opening is critical to proper support selection. The NIOSH STOP database contains load-displacement laboratory test data for most commonly used standing supports. Hydraulic load cells currently used to measure in-situ loading of standing supports have exhibited leakage under load, producing irregularities within the dataset. An improved hydraulic load cell eliminates leakage and produces more consistent data.INTRODUCTIONA hydraulic load cell, more commonly known as a flat jack or JackPack, is a device installed to determine the loading characteristics of the roof-to-floor supports. These standing or roof-to-floor supports include, but are not limited to pumpable cribs, cans, wooden cribs (4-point, 9-point, etc.), metal props, wood timbers, concrete donut cribs, and other variations of these standing supports.Flat jack devices have been used previously to determine the loading of such roof to floor supports. The most commonly used load cell for standing supports is based on a design intended for pre-stressing standing supports, not load measurement. Preloading helps to keep the supports, such as timbers props and cribs, in place during the dynamic loading associated with blasting (Barczak and Tadolini, 2004).Flat Jacks are manufactured in various shapes and sizes depending on the application; common shapes are square and round that are 25.4 mm (1.0 inch) thick when collapsed, as shown in Figure 1. These load cells are produced in South Africa and can be formed into several different shapes depending on the application (Barczak, 2003). The sheet metal that makes up the bladder is comprised of 19-gauge or 1.11 mm (0.04 inch) thickness; the top and bottom pieces of sheet metal are resistance-seam welded around the perimeter. There are two different ports installed on one of the bladder skin corners of the flat jacks; these ports allow fluid to fill the unit, and the other port has a relief valve. The fill port is comprised of a check valve. The pressure relief valve is located in the second port; preset to 1,724 kPa (250 psi), the pressure relief valve keeps the load cell from bursting. Bursting of these load cells typically causes a small tear in the metal skin allowing the fluid to leak out without a large catastrophic failure.The effective inflation range of these load cells is between 25.4 mm (1.0 inch) to 254.0 mm (10.0 inches) thick. Different types of fluids can inflate these load cells but the most common and easily accessible fluid for testing applications is water. Water pressure from the mine supply line can inflate these load cells to the desired load. Depending on the pre-stressing requirements, a pneumatic powered pump, hydraulic pump, or hand pump may be required to inflate the load cells."

Jan 1, 2019

By A. J. Lewis, P. J. Hutcheson, M. E. Robertson, P. A. Moir, K. M. Barfoot

With the content of gold and platinum in the vast majority of ore deposits typically averaging 6 parts per million and less, the accurate and precise measurement of these metals in samples of ore and mining process streams has proven very difficult to achieve by modem spectroscopic analytical techniques. Largely because no other technique has proven suitable, the basic fire assay process has become the accepted international standard for these metals. Fire assay, however, suffers a number of disadvan­tages in the modem, competitive, high technology, and increas­ingly environmentally aware world. It is a labour intensive technique that is difficult to automate, and requires high levels of skill to ensure accuracy and consistency of results. Potentially hazardous chemical reagents are employed, of which, lead, in particular, can be a serious source of contamination to both personnel and the environment if not effectively controlled. Other dangerous elements, such as mercury and arsenic, liberated in high energy furnace operations, are further sources of possible health and pollution hazards. n contrast, the energy dispersive K X-ray fluorescence (K­XRF) technique devised by K X Technology Ltd overcomes many of the technical constraints of conventional low energy X­ray analysis, and has the potential to revolutionise assay opera­tions in precious metal mining. The technology is simply automated, requires basic operator skills, uses no chemicals, consumes less than 20kW, and is capable of detecting gold and platinum to an accuracy of O .1 parts per million by mass. The new third generation design of AZTEC laboratory instrument, released in 1994, is the result of significant technical development. Capable of analysing over 1200 samples per day, and developed primarily for grade control sampling, its applica­tions have spread to gold ore accounting from on-line conveyor belt sampling; screening of exploration samples; measurement of gold in carbon granules for Carbon-in-Pulp process control; and for conducting rapid checks to support key managemen decisions. The economic, rapid, and non destructive analysis ofup to 80g of ore for large numbers of samples, reduces sampling and sub-sampling errors, and provides improved grade estimates for ore bodies. When interfaced to a LIMS, laboratory automation and cost-savings can be further enhanced. The AZTEC design is also being modified for the analysis of platinum. The GOLDSTREAM on-line analysis system is an important new application of K-XRF to the continuous monitoring of process streams in gold ( or platinum) plants and mills. Integrat­ing the technologies of K-XRF to measure total gold, and dissolved gold spectroscopy to measure gold in solution, the insoluble fraction of gold can be deduced, and the effectiveness of the extraction process determined. Slurries are sampled automatically from selected points of the plant and pumped to the system for analysis. The information produced forms the basis for plant control and optimisation.

Jan 1, 1995

By J. A. Procarione

Introduction Ventilation engineers have always felt somewhat uneasy when, in the normal course of their work, they are forced to consider the flow in any mine entry as "wholly rough." Under such conditions in pipes, friction factor is no longer a function of Reynolds' number. This assumption serves to simplify the problem and overcome an evident lack of information concerning the variability of K-factors. During the summer of 1985, a unique opportunity to investigate the reaction of friction factor to changing flow rates presented itself. A Utah coal mine was temporarily directing a substantial airflow through a single entry. By regulating the quantity, it would be possible to obtain a wide range of Reynolds' numbers in an entry composed of two distinct coal thicknesses. This paper describes the conducted study. The theory covering basic fluid flows in pipes that led to the questioning of constant K-factor is presented first. Experimental procedures are then described, including the use of a view camera in determining entry area and perimeter. Finally, a discussion of the observed variations in friction factor versus Reynolds' number is given. Changes of 34% and 45% in K-factor were seen in this study for the two entry heights. The implications of ignoring the relationship in this case and a call for an expanded research effort are also presented. Theory Since a gas is a fluid, the general principles of fluid mechanics are equally applicable to airflow in a mine entry as they are to the flow of water in a pipe. The Darcy equation is, therefore, equally applicable to pressure drop calculations in both situations. This famous formula was originally derived for use in circular cross sections and may be modified for any other shape by the use of hydraulic radius (defined as the area divided by the "wetted" perimeter). The Darcy equation relates the physical parameters of the pipe (diameter, length, and resistance to flow) and fluid velocity to the energy needed to create the flow. A study by Nikuradse (1933) brought to light the suspected dependency of the friction factor term in the Darcy equation upon Reynolds' number. By performing a large number of laboratory experiments, he established some basic concepts upon which other researchers built. Chief among these contributors was Colebrook (1939). Using commercial-grade pipe, he established an empirical relationship between Darcy's friction factor and Reynolds' number that is still in use today. If Colebrook's system of equations is plotted on log-log paper (as was done by Moody, 1944), the curves have some very distinct features. Of importance to the subject at hand is the relative response of friction factor to Reynolds' number at a given relative roughness. Simply stated, a pipe can appear to be either smooth or rough, depending on the flow conditions. As the Reynolds' number increases, the friction factor decreases at a decreasing rate until it becomes nearly a constant value. At this point, the flow is said to be "wholly rough." It is upon this condition that many traditional ventilation solution methods depend. For calculating pressure drops in a mine entry, Atkinson's equation is much more popular than the Darcy equation. Both of these formulas describe the same phenomenon and so have similar forms and functions. The K-factor in the Atkinson equation is equivalent to the Darcy friction factor and can be related by simply changing units, equating the pressure drops, and canceling like terms. A generalized form of this relationship is presented below as equation 1. K = yf/28,800g = [q]f/28,800 (1) where K is Atkinson's friction factor in kg/m3 (lb - min2/ft4), Y is the specific volume in Nt/m3 (lb per cu ft), p is the fluid density in kg/m3 (slugs per cu ft), g is the acceleration due to gravity (9.8 m/s2 or 32.2 fpsz), and f is Darcy's friction factor, which is unitless. The objective behind Eq. 1 is to show the strong correlation between K and f. Since these two quantities differ only by a constant (q]/28,000), the assumed independence of K-factor and Reynolds' number is suspect in light of the known response of f. Unfortunately, the formulation does not provide information concerning the actual relationship, as entry geometry likely plays a major role in the response curve. Only an indirect indication that such a relationship might exist is provided. Previous work on this subject was performed by Thomas Falkie (1958). The study involved a laboratory model composed of sections of straight, steel duct and a range of Reynolds' numbers from 15,610 to 137,200. Results from this work show a variation in friction factor with Reynolds' number in much the same way as it was found to vary in pipes. Over the range of velocities examined, a decrease of approximately 38% in K-factor was observed. This previous experience provides additional incentives to investigate the phenomenon under field conditions. Past model studies done at the University of Utah by Ozukurt (1945), Biron (1944), and Greenhalgh (1942) present similar evidence of this variability. More recently, Kharkar's (1974) study of coal mine friction factors contains similar indications that K-factor is not constant in all situations. Taken together, the data

Jan 1, 1988

By M. McPherson, G. Danko

Methods of measuring in situ rock thermo-physical properties are rapidly evolving. Among those existing in the literature, a particular measurement procedure was selected for further development. The measurement is based on creating a spherical temperature field in a drill hole using a point source heater of constant heat flux. The bivariate temperature distribution 0 (r, t) is measured at several points along the length of the drillhole, radius r from the heater and at particular time intervals (t). A number of different evaluation methods were tested for calculating the unknown thermal conductivity (k) and diffusivity [] from the measured temperature and the known heat flux. The results showed that evaluation using the finite difference scheme and small temperature differences measured at points close together, cannot give a reasonable result. In order to solve the problem a new general analytical evaluation method is developed. Using an appropriate technique, it is possible to simultaneously obtain values for k and [], incorporating a semi least square technique to reduce the uncertainty in the evaluation. The new device and evaluation method makes it possible to obtain from a single drill hole highly precise k and [] values within an 8 hour period. The method has been used in several underground mines in the U.S. with good results.

Jan 1, 1987

By R. K. Rajamani

The theoretical model based on fluid mechanics, in conjunction with the laser-Doppler velocimetry (LDV) measurements, elucidate the size-classification mechanisms in an industrial hydrocyclone. The model has no adjustable parameters and involves solving the Navier-Stokes equations to predict the liquid-phase velocities. The spatial-concentration gradients were determined considering the particle phase in the Lagrangian frame and the classification curve was determined by balancing the forces acting on the particle. The force balance requires liquid velocities, which in turn depend on the local volumetric concentration of the particles. Hence, complete modeling work involves coupling both the concentration and liquid-phase velocity calculations until convergence is reached. Finally, the experimental and predicted classification curves were presented for 250-mm hydrocyclone operating at high-percent solids.

Jan 1, 1994

By D. W. Fuerstenau

One of the more energy-efficient methods for size reduction, namely particle-bed comminution under high compressive loads, was employed to grind eight minerals and ores, using up to 250 MPa pressure. A new approach based on the self-preserving character of the ground product size distributions and a linear energy-reduction ratio relationship is proposed for analyzing this mode of size reduction. The grind ability of the material when comminuted in a particle bed is about one-half that of the single-particle crushing mode, which is in agreement with previous estimates of the relative efficiencies of energy utilization based on direct measurements of surface area produced. The loss of efficiency may be attributed to energy dissipation by particle interaction phenomena in compressed beds.

Jan 1, 1993

By P. Kim Carroll, D. Nick Tiffany, Doyl M. Fritz

Thunder Basin Coal Company received the 1987 Wyoming Excellence in Surface Mining Award for construction of the State's first major sediment control reservoir to be designed using the new settleable sol ids standard. Use of this standard resulted in construction cost savings of more than $250,000; reduced water quality monitoring; enhanced downstream channel stability because of more natural sediment loading; allowed simultaneous establishment of permanent waterfowl and fisheries habitat; and provided a quality recreational site. This article will address factors associated with the design and construction of that sediment reservoir and the benefits that were realized. (Note: This paper was originally published in the proceedings for the 1988 National Symposium on Mining, Hydro1ogy, Sedimentology and Reclamation held in Reno, Nevada, December 5-9, 1988.)

Jan 1, 1989

By M. Sinirkaya

The dissolution process of phosphate rock from the Semikan area (Mardin-Mazidagi, Turkey) using dilute phosphoric acid has been investigated. The work involved studying the effect of important variables, such as reaction time, stirring speed, particle size fraction, phosphoric acid concentration and temperature. Van der Sluis et al.?s model was used to determine the rate of the partial dissolution of phosphate ore. Mass-transfer coefficients (kL) varied between 2.8 and 28.5.10-3 m.s-1. The activation energy of the process varied between 16 and 20 kJ.mol-1. It has been found that the dissolution process is controlled by calcium ion diffusion, rather than by chemical reaction.

Jan 1, 2010

By G. S. Austin

New Mexico produced 83% of domestic potash and 27% of domestic consumption in 1992. The potash industry of New Mexico produces sylvite (KCI), langbeinite (K2SO4-2Mg(SO4)2), and artificial K2SO4. Average sylvite grade in New Mexico today is about 14%. The average grade of langbeinite is 8-10% Kp. Commercial potash occurs in the middle or McNutt Member of the Salado Formation (Upper Permian Ochoan Series). The 120-m-thick McNutt Member dips about 1° east and contains 11 of 12 potential ore zones in the Salado. The mineralogy and proportion of clay minerals, up to 7% of the ore, influence optimum milling procedures and ore grade cutoff.

Jan 1, 1994

By C. W. Schultz

The distribution of material passing a screen, or a set of screens, is described by the equation [ ] where p = the probability that a single particle will pass the screen on a single presentation k = number of layers of screen cloth n = distance from head of screen expressed as number of screen openings. This model can be used to predict the performance of conventional screening operations (i.e., k = 1) as well as the so-called "statistical screening" operations. Using this technique, in which multiple identical layers of screen cloth are employed, screening can be carried out at a finer size than is possible with conventional techniques with no loss of separation efficiency.

Jan 1, 1969

By G. D. Mainwaring, Weng L. W, Lam Y. K.

The first power transmission cable tunnel in Singapore was the 2.6km long undersea tunnel between Pulau Seraya and mainland Singapore, constructed in the1980s. Ten years later, similar concepts were used for the Tuas Cable Tunnel. The tunnel, which includes a 2.2km long immersed tube section, was designed to accommodate 10power circuits of 400kV and 230kV capacity. It is fully equipped with sophisticated control and communication equipment, fire suppressant and life safety systems plus a maintenance vehicle which runs on tracks through the length of the tunnel. The paper discusses the planning, design, and construction of the Tuas tunnel, and the development of these concepts for future tunnels.

Jan 1, 2001