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By J. E. Gray

Before specifications are discussed it may be well to define the term "Mineral Aggregates." Professor K. B. Woods (1) defined "Mineral Aggregate--An aggregation of sand, gravel, crushed stone, slag, or other material of mineral composition used in combination with a binding medium to form bituminous and portland cement concrete, macadam, mastic, mortar, plaster, etc., or alone as in railroad ballast, filter beds, and various manufacturing processes, such as fluxing, etc. " This definition is too all inclusive for the purposes of this paper; therefore, this discussion will be confined to specifications for natural aggregates which means sand and gravel and crushed stone, and limited primarily to coarse aggregate which is aggregate larger than one-quarter inch in size. To the uninitiated, this may seem to be a very limited subject on an unimportant material. However, aggregates are essential in all types of construction. The tonnage and value of these two aggregates produced in the United States during 1959 as reported by the Bureau of Mines were as follows: Sand and Gravel 729,895,000 tons valued at $728,527,000 Crushed stone 581,721,000 tons valued at $824,411,000

Jan 1, 1961

By Bond. F. C.

Introduction Although autogenous grinding applications date back to the early years of mineral processing when tumbling-type mills were first used, there has been a renewed interest in this type of grinding over the past few decades. A review of the historical aspects of autogenous grinding is provided which follows the development of the various types of mills and processes. Wet and dry grinding operations using either autogenous or semiautogenous mills, including the Aerofall mill, are described. Em¬phasis has been placed on the test work required to evaluate the feasibility of using autogenous or semiautogenous grinding for a spe¬cific application. The factors which must be considered to establish the appropriate design criteria for these types of grinding circuits are discussed in detail. Successful application of these grinding circuits results from a thorough test program, a careful analysis of the test results, and a practical engineering approach to the design of the process flowsheet and milling equipment. Certain pebble milling applications, where the pebbles consist of the ore or rock itself, can be classified as autogenous pebble mill grinding, or better known as ore-pebble mill grinding. In the generic sense, pebble milling includes those grinding operations using a tum¬bling mill in which the grinding media consists of various types of pebbles, either ore or other pebbles, instead of metal balls. Conse¬quently, this subject is covered separately in Chapter 5, Pebble Mills. Operating data from many of the installations located throughout the world are included in this chapter. Our appreciation is extended to those companies who contributed this important information. History of Autogenous Grinding F. C. BOND Autogenous grinding, the grinding of ore by itself rather than by special metallic or nonmetallic grinding bodies distinct from the ore, has an old and honorable place in the art of mineral processing. It antedates the use of the rod mill and is only a few years younger than the development of the continuously fed rotating tumbling mill in which it is accomplished. Its history71, 72 is inextricably bound up with that of gold mining. Every important early development of autogenous grinding took place on ores of gold, except in one case of silver ore. In common with many other features of modern mineral processing, autogenous grinding would have been greatly retarded if the winning of gold had been so small a part of mining in the past as it is today. Gold unlocked the secrets of rock-on-rock grinding. In years past gold ores were crushed in stamp batteries and then flowed over copper plates covered with mercury which amalgamated the gold. The McArthur Forrest cyanide process for the dissolution of gold in a dilute alkaline cyanide solution appeared in 1890. With finer grinding it recovered more gold than could be won by amalgama¬tion alone. The first response was to stamp in cyanide solution and finer mesh screens guarding the stamp discharge. However, the fine screens greatly restricted the tonnage stamped, and they wore out rapidly. Rotating tumbling mills70, 73 were the obvious choice to grind the coarse product from stamps. Many of these were Gates tube mills; more than 1,000 of these were sold between 1907 and 1913. They were made in 6, 51h, and 5 ft diam, with lengths of 20 and 22 ft. The 5 x 22-ft size was the most popular. The term tube mill did not refer to the mill shape, but included all tumbling mills using grinding pebbles. The flint or chert rocks found along the coasts of Denmark and Normandy are probably the most durable and resistant to abrasive and tumbling wear of any on earth. They were much used in the early tube mills. The early linings were all silex or Danish flint blocks, cemented into place with portland cement. Local hard stones or cast iron blocks were also used later. The cast iron liners carried lifters and were not bolted to the shell, but were held in a tight circle against it by steel wedges hammered home between them. The first ribbed metal liners designed to hold grinding pebbles pounded into them by the mill action were developed at El Oro, Mexico, about 1905. These and the Forbes, Komata, and Tonopah types, as well as the Osborne type developed in South Africa within about five years, were very successful in reducing liner wear. They sometimes lasted two years or more, and equalled or exceeded the life of silex lining at a lower cost. Some of the types were patented. The pioneer name recorded in the history of autogenous grinding is that of Kenneth L. Graham. In 1907 at the Geldenhuis Deep Ltd. mine near Johannesburg, he ran a comparative test on two tube mills. One mill used pieces of the common gold ore, or banket, and the other used the customary imported Danish pebbles as grinding media. He published the first account of autogenous grinding.'' In a test lasting 81 days the ore pebbles showed a definite saving over the Danish pebbles. Graham's historic paper also describes the invention of B. Chew of the Crown Deep Mines of the first trammel to be attached to a grinding mill discharge. The first known account of autogenous grind¬ing printed outside of South Africa was the description of the Graham test in Mining and Scientific Press's The use of grate- vs. overflow¬discharge was also described at this time." The news of this successful test appears to have had immediate effect, for by the end of 1908 the number of tube mills on the Rand had increased from 72 to 120.76 Presumably, most of these mills were now using autogenous grinding. The ore was principally a hard conglomerate of quartz peb¬bles cemented by silica, and was eminently suitable for use as a grind¬ing media. It is unfortunate that in South Africa the new autogenous process continued to be called by its old name of pebble milling, since the name does not distinguish between grinding with ore and grinding with extraneous pebbles. For increased clarity the former is called rock pebble milling. The first historical stage in the development was what is now designated as secondary autogenous grinding, or rock pebble milling. It consists of grinding a feed all passing 'A in. or finer with ore pebbles about 2 to 4 in. in diameter. The next stage to develop was that now called intermediate autogenous grinding, where larger amounts of larger pebbles about 5 in. in size were used to grind ore which had been crushed to about rod mill feed size or somewhat finer. It was developed on the Rand and in other places where coarse stamp screens were used to increase mill tonnage. In many cases the early secondary and intermediate autogenous mills have now been replaced by conventional ball mills and rod mill-ball mill circuits, with the object of further increasing grinding capacity. The third stage to develop is designated as wet primary autogenous grinding, in which run-of-mine ore or a primary crusher product is all fed to the autogenous mill together. It developed many years later indepen¬dently in the United States and in South Africa. The fourth and most recent stage is that of dry primary autogenous grinding, which developed in the United States and Canada. All four stages originated in gold mining. The first use of commercial autogenous grinding outside of the Rand apparently took place five years later in 1912 at the Santa Gertrudis gold mine at Pachuca, 55 miles northeast of Mexico City. This was followed closely by an installation at Goldfields, Nevada, in 1914-1915. The first name associated with autogenous grinding

Jan 1, 1985

By S. Lefond

A glance at the accompanying table and a review of contributors' comments suggest that the industrial minerals industry is recovering from the recession of the past few years. Actually, the total value of nonmetal production in 1983 was $15.5 billion, up 10% over 1982. Nonmetallics still have not recovered to 1981's high of $25.3 billion, but at least it is on the way up. It is significant that cement (+20%), clays (+13%), gypsum (+16%), sand and gravel (+12%), sodium carbonate (+7%), and crushed stone (+11%) are up. These commodities are largely used in the housing and construction industries. Raw steel and steel mill products, iron ore production and castings, and purchased scrap are showing improvement and increased in value last year. They are, however, still not up to the high of 1981. These industries consume considerable amounts of many industrial minerals, such as limestone, dolomite, fluorspar as fluxes, and many types of refractories.

Jan 5, 1984

By James R. Brown

Mount Isa Mine should be regarded as a large mining complex rather than one mine. This arises from the geography, variety and extent of the orebodies, the mining methods, and the use of 14 shafts for ventilation distribution. A brief resume is presented here since comprehensive descriptions of lead-zinc mining methods {11}, copper mining methods {2 }{3}, geology 241, stope fill {5} and ventilation techniques {6}{7}, have all been published in the last five years. Mining extends over a north-south strike length of 2.5 miles (4 Ian) with a maximum width across dip approaching 3 200 ft (1 Ian). Current mining is to a depth of 3 150 ft (960 m) with the ore hoisting shafts extending 660 ft (200 m) deeper. The composite longitudinal section, Figure 1, shows a representational disposition of the copper and lead-zinc-silver orebodies in the central shaft complex where the main service and hoisting shafts are located. To the south the X41 man and materials shaft provides access to the copper area. The mine layout is typical of high tonnage track- less mines, utilising a large diesel fleet, raise- borers and some large diameter hole stope drilling. Mining methods include sublevel open stoping, slot and massfire, and a trial vertical crater retreat in the copper ore, and sublevel caving, sublevel open stopes with and without rib pillar recovery, and mechanised cut and fill in the numerous lead orebodies. All ore reports to one of the three crushing systems located below 19 level in the central shaft complex. Copper ore is hauled exclusively along the 19 level computer assisted Rockflo haulage system, and lead-zinc-silver ores report via central orepasses from Granby haulages on 13 level and 15 level. Tonnages hoisted during the 1977178 financial year were 5.0 million for copper at 3.2%. and 2.3 million for lead-zinc-silver at 7.8%. 6.3% and 7.06 oz/ton (216 g/tonne) respectively.

Jan 1, 1980

By Sol Ribakoff

In 1973, the Subcommittee on Contracting Practices, U. S. National Committee on Tunneling Technology, National Academy of Sciences, under the able chairmanship of A. A. Mathews, Engineering Consultant, now residing at Kaunakokai, Hawaii, undertook the task of developing recommendations for improving the performance of underground construction work, reducing the costs of such work and minimizing the adverse atmosphere in which owners and contractors were performing their respective functions. The author of this paper and C. F. Palmetier, a highly qualified engineer, were thereupon appointed as staff assistants to the Subcommittee, to conduct a study of existing practices and relationships in Western Europe and in the United States, to formulate recommendations, for consideration by the Subcommittee and the participants in a future workshop, as to desirable improvements in United States contracting practices and relationships. The study, conducted during 1973 and 1974, involved personal interviews of a total of 162 owners, engineers, contractors, lawyers, and educators throughout the United States and in 7 European countries, the analysis of 178 replies to questionnaires sent to individuals and firms involved directly or indirectly in construction, and a workshop, near Napa, California, attended by 53 representatives of all segments of the construction community. The resulting report, entitled "Better Contracting for Underground Construction", was submitted by the Subcommittee to the National Academy of Sciences, which approved its publication in 1974 by the National Technical Information Service. It may be obtained from that Service at Springfield, Virginia, 22161, as Accession No. PB-236 973. It was recognized-during the course of the study that while contracting practices and owner-contractor relationships were the

Jan 1, 1981

By R. G. L. McCready, G. Dr. Heinrich, V. I. Lakshmanan

The objective of this study was to prove repeat loading capacities of physically stabilized fungal biomass from Penicillium sp. for the removal and recovery of uranium from mine water (Denison Mines). The testwork was carried out on a bench scale in small columns and proved that it is possible to stabilize the biomass in an inorganic compound. A lifetime of 10 loading-eluting cycles of the stabilizer biomass product was obtained by additional pretreatment. Sodium carbonate proved to be an effective elution medium. Loading and elution can be controlled by the pH values of the column. The effective loading capacity until the breakthrough point is approximately 70 % of the overall loading capacity. The loading capacities of the stabilizer biomass product are comparable to that of the original biomass. Uranium recoveries of 90 to 99 % were achieved during the loading and eluting under optimized conditions. Depending on the used biomass the described process might be applicable to remove uranium or other dissolved heavy or rare metals from effluents.

Jan 1, 1989

By Linda Frederick

In July 1997, Krupp Canada obtained the contract to design and supply the conveyor system for Chile's Los Pelambres copper mine expansion project. Progress on the overland conveyor system is currently on schedule. It is a challenging task to convey copper ore from an open-pit mine located on a mountain site 3,000 m (9,840 ft) above sea level down 1,300 m (4,265 ft) to the processing plant at the valley floor below. The Los Pelambres conveyor system moves copper ore at a rate of 8.7 ktlh (9,600 stph) and at a speed of 6 ml sec (1,180 ftlmin) for 12,750 m (41,830 ft). The distance is divided in three conveyors, each 1,800 mm (71 in.) wide. The largest conveyor is 6 km (3.7 miles) long. To protect against avalanches and rockslides, the conveyors run through a 12-km- (7.4-mile-) long tunnel system. The lowest of the three conveyors is equipped with a shuttling head end. With this, the conveyor discharge point can be moved back and forth by 100 m (330 ft), allowing it to build up a longitudinal stockpile at its end. To meet the extreme design parameters, the limits of conveyor design had to be pushed to record-setting marks. For instance, the ST-7800 steel cord conveyor belt is the strongest belt ever installed in a conveyor system. A total drive power of 25 MW (33,535 hp), consisting of 10 2.5-MW (3,352-hp) drives, is included in the design plans. In loaded condition, the electric motors act as generators and feed electric energy back into the power grid. The motors are controlled by variable frequency inverters that provide an infinite adjustment of motor speed. This technology allows starting and stop- ping the conveyors precisely along predetermined acceleration and deceleration ramps. This is done so harmful belt jerking and stress waves can be avoided.

Jan 1, 1999

By Jim W. Rosteck, Anthony Del Vescovo

In December of 1992, the City of New York, Department of Environmental Protection, solicited bids for Contract 543B. The low bidder was a joint venture of Schiavone Construction Co., Inc. and the J. F. Shea Co., Inc. When completed, the project provides a 4.88 meter diameter water tunnel 8,840 meters long. This paper presents a case history of the equipment and construction methods utilized for this, the first portion of the New York City Water Tunnel constructed by use of a tunnel boring machine.

Jan 1, 1997

By J. E. Moyle

Introduction In October 1983, Rio Algom Ltd. decided to develop the East Kemptville tin deposit. This decision was the result of intensive geological and metallurgical evaluation work, as well as careful studies of environmental and marketing aspects. The property is located about 54 km (34 miles) northeast of Yarmouth, Nova Scotia, near the village of East Kemptville. Geology The geological setting is a granitic intrusive at the contact with metasediment. The tin mineralization is in the form of cassiterite (SnO2), which is about 80% tin. Sulfides are associated with the deposit containing silver, copper, and zinc, which are recoverable as byproducts. The mineralization is associated with quartz veins and greisen alteration. In the center of the deposit, the zones are so close together they have the appearance of a massive or porphyry type deposit. Ore Reserves The mine plan is based on 56 Mt (62 million st) at 0.165% tin. Up to the ninth year, mill feed will average about 0.2% and lower grade material will be stockpiled. In later years, the average grade will be 0.16% tin. A 0.08% cutoff grade is planned for the entire 17 years of production. East Kemptville is a relatively low grade tin deposit, and only a combination of favorable circumstances has made it economic. • The ore body is situated at, or very close to the surface, permitting mining by open-pit methods at a very low stripping ratio. • The tin occurs in relatively large crystals that allow for good recovery by gravity techniques. • It is ideally located in a well-settled area, with all essential infrastructural requirements already in place. • The positive and cooperative response from various governmental agencies involved are encouraging. Mine Plan The mine plan incorporates an initial pit, followed by three expansions to the ultimate pit. Mining will be at 14 kt/d (15,000 stpd) and will include 9 kt (10,000 st) of ore plus 5 kt (5,500 st) of waste and low grade. After five years, the mining rate will increase to 21 kt/d (27,500 stpd). It is planned to drill vertical 165-mm (6.5-in.) blast holes on a 6-x 6-m (20- x 20-ft) pattern. Bulk slurry explosives will be used to break the rock. Loading will be with hydraulic shovels into 70 t (77 st) haulage trucks. The trucks will deliver the ore to a 13 x 20 m (42 x 65 ft) gyratory crusher, where it will be crushed to 150 mm (6 in.). Secondary and tertiary cone crushers will be used to further crush the ore to 13 mm (0.5 in.). Process Design Tin extraction technology is practically unknown in North America, but Rio Tinto Zinc, which has a 53% ownership in Rio Algom, is involved in tin production in the UK. Rio Algom has used this experience and expertise in metallurgical evaluation work and in tin-related aspects of plant design. Mineralogical and metallurgical test work have been performed, both on laboratory and pilot plant scales. Mineralogical work was done largely in the UK, the laboratory test program was carried out at the Lakefield research facility in Ontario, and pilot plant work was conducted in Australia. This program has resulted in significant improvements in recovery and concentrate grades, over best projections that could be made before this work was carried out. Concentrating Process The concentrator is being designed to process about 9 kt/d (10,000 stpd). The first step is to reduce the size of the ore to -700 µm (-24 mesh) in a rod mill/ball mill grinding circuit. The ball mill will operate in closed circuit with high capacity banana-type screens. The screened product will be deslimed to 30 µm (560 mesh) with cyclones, then passed over the pri-

Jan 4, 1984

By S. Komar Kawatra, Henry J. Walqui, Timothy C. Eisele

Population balance models were used to model the grinding action of industrial scale coal pulverizers. Experimental work was conducted with two different coal samples to determine the values of the appearance and selection function. These functions were determined for vertical mills by using s 6-inch by 10-inch laboratory roll mill to represent the action of a vertical mill. Two very important operating variables were identified for vertical mills: feed rate and roll spacing. Factorially designed experiments were used to analyze .and quantify the effect of these two variables. The models were then adapted to represent changes in operating conditions by incorporating the effect of the feed rate and roll spacing effects. This resulted in a simulation model able to respond to changes in operating conditions, by providing corrected predicted values for the product size distribution.

Jan 1, 2002

By R. J. Gary

Why would a company in its right management mind risk a fuel conversion program on a fuel that can't burn if it's too wet or too dry, too hot or too cold, too coarse or too fine, or doesn't have enough Btu's to supplement good combustion? On December 23, 1981, two months ago, we finished our first ten years of burning lignite -- this unconventional coal. It is from that experience that I am qualified to address you today. As some of you here probably already know, my company, Texas Utilities Generating Company, has pioneered the utilization of Texas lignite for electric power generation on a large scale, and I think it is fair to say that we have done this pioneering work largely on our own. Some of us feel like Noah did when he built the arc! I have titled this presentation "The First Lignite Decision" because our company was the first to make this major decision in Texas in the mid-1960's. It was a big decision, and at the time, perhaps a bold one. When you look at the conditions that existed in the mid-1960's, you can see why.

Jan 1, 1982

By John E. Pavlick

The availability of concentrated brines rich iodide, bromide, chloride, sodium, magnesium and calcium ions has led to extensive chemical manufacturing operations in Michigan. The brines, ranging 1,000 to 8,000 feet below the earth's surface, are the remnants of ancient oceans which periodically covered and receded over the land area which is now Michigan. After pumping the brine to the surface, iodine and bromine are extracted via an oxidative process. Iodine and bromine find application in catalysts, disinfectants, flame retardants, oil field fluids, film, and gasoline additives. Addition of alkalinity to the brine precipitates magnesium hydroxide, used in high quality refractories needed for steel manufacture. The brines are also the country's primary source of calcium chloride, employed in ice and dust control.

Jan 1, 1984

By V. F. Hollister

Computer programs developed as part of the PROSPECTOR project at SRI International can indicate where the highest grade hypogene copper occurs in porphyry copper prospects. The programs are useful in selecting drilling targets in untested porphyry deposits. Because of mineralogic, structural and lithologic variations in porphyry-type deposits, three distinct computer programs have been constructed; however, this paper considers only the stockwork type in homogeneous rock (similar to the Lowell and Guilbert model). The programs represent models in the form of inference networks that utilize the mineralogic, alteration, lithologic, structural, geochemical and geophysical data normally collected prior to a drilling decision. One example of an application of the PROSPECTOR program for a stockwork-homogeneous porphyry is given: Island Cooper in British Columbia. Computations based on the surface geologic, geochemical and geophysical data for Island Copper clearly disclose the best hypogene grade of the deposit. Other deposits were tested in the programs as well, and in each case PROSPECTOR programs indicate the region with the highest hypogene grade.

Jan 1, 1983

By W. R. SHAHAN, W. R. Reed, J. P. Rider

Roof bolter operators may be exposed to high respirable dust concentrations on continuous miner sections with blowing face ventilation when bolting is performed downwind of the continuous miner. One solution to reduce the high respirable dust concentrations is to use a canopy air curtain (CAC) to deliver clean air from a filtered blower fan directly to the bolter operators under the canopies. The influence of CAC installation on the airflow and dust dispersion around the location of the roof bolter operator can be evaluated by using computational fluid dynamics (CFD). 

The Bagdad mill, built in 1977, was de-signed for a mill capacity of 36,300 tpd. An ABC (Autogenous Mill-Ball Mill-Crusher) grinding circuit was chosen. The original mill contained three completely independent grinding circuits, each containing one 9.75 m diameter by 3.96 m long fixed speed autogenous mill, one 4.72 m diameter by 6.71 m long ball mill and one 2.13 m diameter short-head cone crusher. Total installed power per grinding circuit was 8,464 kw with 5,966 kw in the autogenous mill, 2,237 kw in the ball mill and 261 kw in the crusher. (See FIGURE I--Major Equipment Flow Diagram.) The autogenous mills were designed to be able to operate semi-autogenously but were never converted to SAG. As a result of this design, only about 4,100 kw of the designed power is utilized in the autogenous mills. The grinding circuits are closed with 2.44 m by 6.10 m double deck vibrating screens. Screen oversize is returned, by a series of conveyors, underneath the mill coarse ore stockpile to feed the crushers. Variable speed belts feed the crushers and control power draw. Crusher product reports directly to the tail end of the autogenous mill feed belt. (See FIGURE 2--Typical Crusher Feed and Product Size Distributions.) Tramp iron in the autogenous mill-crusher circuit is handled in a unique way. A magnetic sensor detects the metal. This closes a gate which directs the crusher feed onto a separate belt which bypasses the crusher and returns the material to the autogenous mill feed belt.

Jan 1, 1992

By Haia Roffman, Amiram Roffman

A gas company operated more than 100 distribution stations. Mercury filled manometers were used for years in these stations to measure the flow of natural gas through the system. Use and handling of these manometers resulted in mercury spills and ground contamination. To assess the human health and environmental effects of these spills and the need of remediation, it was important to determine mercury specific species present and their concentrations. Soil samples were analyzed for total mercury, methyl mercury, inorganic mercury and elemental mercury. These analyses served as important input in the risk assessment performed for these stations.

Jan 1, 1998

By J. C. Weimer

The goal of Bethlehem's mining research program is to improve both the safety and productivity of our mines through the use of new equipment, new technology and new mining methods. Although we can all agree on the value of such goals, achieving them can be a costly, time-consuming and sometimes frustrating experience. However, the potential benefits of lower costs per ton and better safety in an increasingly more stringent and confusing regulatory environment make the expended effort worthwhile. At Bethlehem we feel that the mining companies are in the best position to determine the needs of the industry, and coal companies have the incentive as well as mine sites at their disposal for testing. Therefore, the mining industry should be leading the research effort

Jan 1, 1979

By Kirk Carlton

The Athabasca tar sands of Alberta are an increasingly important source of crude oil for the North American continent. Published figures indicate estimates of recoverable resources in the tar sands at some 300 billion barrels of synthetic crude of which some 86 billion barrels can be recovered by surface mining techniques. At the present time, two commercial plants are in operation, Great Canadian Oil Sands Limited and Syncrude Canada Ltd. Their present combined capacity is approximately 150,000 barrels per day. Some of the factors which will make this oil expensive will be noted here. The location of the present producing plants is 500 kilometres north of Edmonton at an elevation of approximately 320 metres. Recorded temperatures range from +38 to -55 degrees Celsius. Wind velocities are not high but the chill factor with even a slight breeze and minus 40 degrees is very uncomfortable.

Jan 1, 1979

By Wendell H. Wiser

A comparison is presented of coal pyrolysis at temp¬eratures ranging from 4090 to 497°C and thermal dissolution of coal in tetralin at temperatures ranging from 350° to 450,°C, both utilizing a Utah high-volatile bituminous coal. The initial coal pyrolysis reactions are second order with an enthalpy of activation of 35.6 kcal per mole. The fraction of total product yield produced under second order conditions ranges from 67% at 409°C to 96% at 497°C. The process then gradually deteriorates to a first order reaction in the later stages with enthalpy of activation of 4.1 kcal, per mole. The initial reactions of solution of coal in tetralin are second order with an enthalpy of activation of 28.8 kcal per mole. The fraction of total product produced under second order conditions ranges from 63% at 350°C' to 94% at 450°C. The dissolution process then gradually changes to first order in the later stages with enthalpy of activation of 15.6 kcal per mole. A model is presented which relates the two processes and explains, the significance of the above similarities.

Jan 1, 1967

By Jozef Descour, Kazunori Nishioka, David M. Neil

Designers, engineers, and contractors are using three-dimensional seismic tomography for geotechnical site investigations and during tunnel excavation for hard rock and soft ground applications. Utilizing multiple types of seismic signals produced by a TBM, drill, or impact breaker, the reflection of different velocity features are processed into a holographic image of the actual structure to be encountered. The Mill Creek Phase 3 alignment in Cleveland, Ohio, was imaged to define existing conditions along a 1,200-ft section of a proposed 6.1-m (20-ft) diameter CSO tunnel and, specifically, a zone of expected anomalous conditions where drilling was inconclusive. In Japan, Kajima Corporation used TRT™ to image a number of tunnels including the Fujikawa and Kanaya tunnels in a combination of methods to map structural features along the alignment.

Jan 1, 2001