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By Ralph S. Mattson, Frederick T. Hancock

GENERAL DESCRIPTION The Granduc mine is situated on the west side of Granduc Mountain in the Leduc River area of north¬west British Columbia about 51 km (32 miles) north¬east of the town of Stewart. Entry is by means of a 16.6-km (10.3-mile) long haulage adit from the concentrator site at Tide Lake. The principal ore mineral is chalcopyrite. Ore mineralization varies from dis¬seminated to irregular semimassive stringers generally associated with highly folded and sheared biotite-rich sections of metasediments. The ore bodies vary in width from 3.6 m (12 ft) to over 18 m (60 ft) in a zone some 800 m (2600 ft) in length dipping at an average of 75° to the west and plunging steeply to the south. Capping varies in thickness from 0 to over 300 m (1000 ft). SELECTION OF MINING METHOD In the early stages of planning the primary require¬ments to be met by the mining method were: (1) suit¬ability to high output and productivity, (2) adaptability to mechanization in order to minimize operating costs, and (3) minimization of the costs and the development period for preproduction. Considering these, the selection of a mining method was narrowed to a choice be¬tween sublevel long-hole stoping or sublevel caving. A method utilizing backfill was ruled out as uneconomical, especially since mill tailings would not be readily available. At the time, the following facts about the ore body were recognized: (1) the average width of the ore body was 12 m (40 ft), (2) 30% of the stoping blocks were in areas of 6 m (20 ft) or less in width; (3) in many cases, ore zones were located in parallel lenses or were irregular in shape; (4) major faults were present in the hanging wall close to the ore, with minor faults within the different ore zones; and (5) the ore itself was lami¬nated with fractures and jointing crossing such bedding planes. Considering these factors, the two stoping meth¬ods were compared. Sublevel Open Stoping The characteristics of sublevel open stoping are: 1) It is generally not used for widths below 6 m (20 ft) since the ratio of waste development increases as level intervals are reduced to insure good control of long-hole drilling. 2) This method is used where ground is relatively competent. Otherwise more pillar support is required, increasing ore losses or mining costs with pillar recovery. 3) The method is not easily adaptable to parallel ore zones separated by relatively narrow waste bands. 4) Close control of pillar and stope design will per¬mit some degree of dilution control. Sublevel Caving Sublevel caving is characterized by the following: 1) The method can be used for a variety of ore widths, recognizing that 3 m (10 ft) in width may be an economical minimum. 2) It is particularly favorable where wall rock is weak. 3) The method has flexibility so that irregular ore bodies or parallel lenses can be mined. 4) The need to leave pillars for support is eliminated 5) Dilution and tonnage recovery are interrelated. With concern about the stability of the hanging wall and the geometry of the ore bodies, there was a growing favor to choose the sublevel caving method. However, this method was relatively new to Canadian mining practice. Teams were sent to Sweden to tour mines using sublevel caving and to study their methods and any extraction and dilution problems. The objective was to develop cost and performance data and ore recovery grades and tonnages for feasibility comparisons. Next, detailed mine plans were developed covering a three-year period using sublevel caving and sublevel open stoping. Extensive analyses of the development and production costs for each method were made. With sublevel caving, ore losses of 10% with a 20% dilution rate were used. The same ore loss was estimated for sublevel open stoping with dilution varying from 11 to 15%. As a result of these studies, the decision was made to use sublevel caving partly because slightly lower op¬erating costs, together with higher productivity, offset the adverse effects of higher dilution; and partly be¬cause, at the start, there would be less risk in being able to handle the ground, and the method offered more flexi¬bility. Open stoping was not ruled out for testing at a later date. It was recognized that some other method of mining would be required for mining the ore extensions below the glacier, where surface subsidence must be avoided. During the operating life of the mine, open stoping was tested in narrow width ore zones and found un¬satisfactory due to wall failure. A cut-and-fill stope, utilizing run-of-mine waste from development, was also operated on a trial basis. A sequence was finally estab¬lished that permitted ground control; however, produc¬tivity needed considerable improvement in order for open stoping to be considered as a sole alternative for mining below the main haulage level. At the termination of operations in June 1978 over 13 000 000 t (14,500,000 st) had been extracted from above the main haulage level at production rates varying from 3270 to 7250 t/d (4000 to 8000 stpd). Sublevel Caving Methods Two basic methods were used, transverse and longi¬tudinal. The transverse method was used mainly in the upper C ore body in widths greater than 18 m (60 ft), and occasionally as an alternative to the longitudinal method in localized areas where strike faulting inter¬fered with normal development. The longitudinal method was used in ore bodies varying in width from 3.6 to 18 m (12 to 60 ft), with a multilongitudinal varia

Jan 1, 1982

By Michael A. Linkous, Mark J. Zdunczyk

Silica in the form of sand and sandstone is one of the most common, and at the same time, unique industrial minerals. Found in every rock type of every geologic age and virtually everywhere in the world, silica is used in products that touch just about every aspect of daily life. Imagine a world in the 1990s without computer chips, fiber optics, or glass, and you have just begun to understand how important silica is to the quality of life we enjoy. The elements silicon (Si) and oxygen (0) comprise roughly 60% of the earth's lithosphere to a depth of about 16 km. The crystal structure of silicon dioxide consists of one atom of silicon bonded to four surrounding atoms of oxygen to form a three-dimensional network of SiO, tetrahedra. This network makes up the mineral quartz (Murphy and Henderson, 1983), the most common detrital mineral in most sandstones. Quartz is also a major constituent of many igneous and metamorphic rocks and is widespread as a siliceous cementing agent in various rock types. Although quartz is common, sandstones, quartzites, and pegmatites and the unconsolidated sediments derived from them that have a silica content high enough and pure enough to meet today's market demands for quality and consistency are not common. USES AND SPECIFICATIONS Silica sand that is mined and processed for industrial uses must conform to the chemical and physical specifications set by customers. In the United States almost half of the silica sand produced is used in the manufacture of glass. Other important products include foundry sand, ground silica, blasting sand, and fracturing sand. Glass Sand Silica is the principal glass-forming oxide in a glass batch. Glass manufacturers develop model specifications for each source of silica sand used. These specifications broadly define the limits and ranges for chemical and physical properties of the sand and are used by the manufacturer in calculating the desired batch mix or formula. Some specifications may be critical to a glassmaker and require very stringent limits on the quantity of impurities in the sand. For example, the total iron oxide content of a batch is extremely crucial when making white or flint glasses (Mills, 1983). Iron is present in almost every raw material used in a glass batch and must be carefully controlled in order to obtain a consistent color in the finished product. It is difficult, however, for a raw material supplier to tightly control the chemistry of a naturally occurring material such as silica sand. To a great extent the commercial quality of a sand is determined by its geologic history. Realizing this, glass producers tailor their model specifications to each source of approved material. In general, a glass company is concerned most about the consistency of raw materials on a day-to-day basis. Soda-lime-silica glass was the earliest type of manmade glass (Baker-Can, 1967) and still accounts for most of the glass manufactured for commercial use today (Mills, 1983). It is relatively easy to melt and shape and is less expensive per ton to produce than most other types of glass (Baker-Can, 1967). Soda-lime-silica glass is used in fabricating containers, flat glass products, incandescent and fluorescent lamps, glass fiber, and many other products. Heavy minerals such as ilmenite, leucoxene, kyanite, and zircon are impurities on which strict limits are placed for a glass batch. Because of their refractory nature they either do not melt or only partially melt, which results in stones or feathers in finished glass. Aluminosilicates such as kyanite also contribute unwanted alumina to the batch as they partially melt. Limits are especially rigid for refractory mineral grains coarser than 0.60 to 0.425 mm (30 to 40 mesh). [Tables 1 and 2] present typical specifications for silica sand used in flat glass and container glass products. The percentages shown represent an average of many companies7 specifications.

Jan 1, 1994

By J. D. Miller

Fluid flow phenomena and therefore the flotation efficiency of air-sparged hydrocyclone (ASH) flotation are strongly dependent on operating and design variables such as air and slurry flow rates, underflow and overflow opening areas, percent solids of the feed, reagent levels, particle size and ASH length. Time-averaged multiphase flow characteristics, as determined by X-ray CT (described in a previous publication), are used to understand and explain the steady-state ASH flotation of quartz. A detailed parametric study of quartz flotation by a nominal 2in. diam. air-sparged hydrocyclone (ASH-2C) revealed the influence of these variables on the flotation response, which is discussed in terms of the multiphase flow characteristics. Thus, a phenomenological description of quartz flotation has been established to assist in the further development and utilization of the ASH technology.

Jan 1, 1996

By A. Ligorio Pires de Carvalho

The main potash deposit at Taquari-Vassouras is contained in cycle VII, and consists of several sylvinite bodies. Cycle VII belongs to a sequence of nine cycles defined by Szatmari (1974) in the Sergipe-Alagoas basin. The sylvinite layers are separated by halite beds. They are seated on or may be laterally in discordant contact with other lithologies such as the tachyhydrites at the base, and the limestone breccia at the top. The main structural features in the deposit include numerous synclines and anticlines, salt dissolution phenomena, and open fractures associated with the axes of the anticlines.

Jan 1, 1995

By Peter C. Busse, Henry M. Giegerich, Ronald K. Netolitzky

Zimbabwe The Republic of Zimbabwe is situated in south central Africa and north of the Tropic of Capricorn. The country is land-locked, bounded on the north by Zambia, on the south by the Republic of South Africa, on the east by Mozambique and on the southwest by Botswana. Nearly 400,000 sq km in area, Zimbabwe is bigger than both France and Spain and nearly three times the size of England. The outstanding physical feature is the central plateau, known as the highveld, which is about 650 km long and 80 km wide at an elevation of +1,200 m, and on which the Jena Mines is located. Because of its elevation and inland position, Zimbabwe's climate is temperate, generally drier and cooler than is normally expected in the tropics. Zimbabwe's population is in excess of 10 million. English is the official language, with Ndebele and Shona being the main ethnic languages. About one million people live in Greater Harare, the capital city. The basic unit of currency is the Zimbabwe dollar, which has depreciated substantially over the past few years. Currently (November, 1995), the exchange rate is $US 1.00 = $Zim 9.00, compared with $US 1 .OO = $Zim 2.50 in 1991. Project Area The Jena Mines Complex is situated in central Zimbabwe (Figure 1), in the Silobela area of the lower Gweru River valley. The mine site is 270 km from Harare by paved and gravel road. The Jena Mines property consists of a single rectangular (8 km by 5 km) shaped mining lease with an area of approximately 40 sq km (Figure 2). Annual average precipitation is 720 mm falling in the summer months between October and April. Mean daily maximum temperature is 24°C in October and mean minimum is 14°C in July. The southern parts of Zimbabwe have experienced drought conditions over the past four years which has affected water and power supplies. The countryside in the Jena area is generally low relief with a gentle slope to the northwest. The mine site topography is flat with an average elevation of 1,210 m. Zimbabwe Mining Industry Zimbabwe has a long mining tradition, particularly for gold. In the 1,200 years preceding European colonization, it is estimated that about 4,000 ancient mines produced between 600 and 800 tonnes of gold. Since the turn of the century more than 1,700 tonnes of gold have been produced. An excellent infrastructure has developed to support the mining industry. This includes a well- maintained system of paved roads, railway links to major mining areas, an electricity grid covering most of the country, and numerous industries manufacturing a wide range of mining supplies. Jena History The claims in the Jena Mines area are among the earliest registered in Zimbabwe. The gold potential was easily recognized because of extensive ancient (pre-European) workings. European trading beads from the 14th Century have been recovered from anthills in the mine area. Development of the Jena Mines commenced in 1898 and several mines have operated intermittently over the past 90 years. The recorded cumulative historical production from the significant producers of Jena is tabulated in the following:

Jan 1, 1996

By J. F. Rakszawski, Robert P. D'Orazio

The use of cyanide in the processing of gold has been documented for over a century. It is still one of the more effective methods of isolating gold, as witnessed by the fact that in 1987 cyanidation was used in the processing of 91.5% of the gold produced in the United States.

Jan 1, 1990

By P. Massacci, F. La Marca, G. Bonifazi

Some deposits of inhomogeneous materials, which occur near the surface and are exploitable by open-pit mining, may he characterized in real time prior to mining through groundsurface imagery. If the slice to be stripped is not overly thick, surface texture and color properties may be extrapolated to its entire thickness. Image-analysis techniques for processing ground-surface images acquired in situ or in the laboratory shortly after their acquisition have been developed. These images yield pattern vectors representative of red, green and blue (RGB) color component distributions and hue, saturation and brightness (HSB) texture parameters. The techniques were applied to a sandy ore deposit containing three lithotypes. Geostatistical analysis indicated that the data used to characterize the lithotypes were reliable. The correct recognition of the lithotypes was carried out using a multibarycenter classification algorithm. Such in situ image-analysis procedures provide a means for selecting the ore to be mined, selecting the proper ore-processing method and determining the appropriate blend to he processed. This can be done either before or during mining.

Jan 1, 2000

By Ke Yang

In Chinese coal mines, extraction of deep, highly gassy soft coal seams sandwiched between soft floor and soft roof in complicated geology is commonly encountered. How to safely and efficiently excavate such seams is a very significant and important problem. It has been a focused research area in recent years. By combining the characteristics of fully mechanized longwall mining methods such as large cutting height and mining along the dip, an integrated method and technologies for the Zhangji Coal Mine were developed. This technology includes the design of a complicated geological exploration system, optimization of mining method and working face parameters, control of rock pressure and high levels of gas, reliability model of the production system, and selection and compatibility of equipment. Engineering practice shows that the integrated technology was successful in mining these complicated seams. This study not only enriches the mining method, but also improves the coal mining practice, especially ensuring both safety and productivity under complicated geological conditions.

Jan 1, 2009

By C. K. Skokan

Various geophysical tools have been tested over the last eight years to evaluate their usefulness in defining damaged rock zones in an underground facility at the WIPP site in New Mexico. These tools include direct current and frequency domain electrical methods and seismic tomography. The electrical measurements show a "drying rind" to exist around older excavations. Seismic tomography confirms that a rind of lower velocity has developed along walls. In combining these tools, a monitoring program has been proposed to observe long-term changes in bedded salt. Results from the monitoring of electrical data over a 2-year time period illustrate the applicability of the technique in an underground environment.

Jan 1, 1993

By J. B. Ackerman, C. S. Bucans

The Sunshine Mining Co. has recently started up its new silver refinery in Kellogg, ID. The new plant recovers silver anc copper values from a high grade tetrahedrite concentrate using hydro- metallurgical processes. The plant and process are both new and have gone through the initial startup phase during the first six months of 1985. The full scale plant was developed from laboratory test work. While the metallurgy of the process worked as expected, the material handling problems were difficult to over-come. As might be expected, those parts of the plant that represented available technology started up easily, while the parts that represented new technology presented the most difficulty. Topics covered in this paper include: 1) insufficient type and amount of agitation in the leach vessels, 2) discharge of a non- homogeneous slurry from the leach vessels, and 3) problems associated with very low flow rates in slurry lines.

Jan 1, 1987

By Jr. Neudecker

Rock melting technology can provide in-situ glass liners in nuclear waste package emplacement holes to reduce permeability and increase borehole stability. Reduction of permeability would reduce the time and probability of groundwater contacting the waste packages. In-creasing the stability of the storage boreholes would enhance the retrievability of the nuclear waste packages. The rock melting hole forming technology has already been tested in volcanic tuff similar to the geology at the proposed nuclear waste repository at Yucca Mountain, Nevada.

Jan 1, 1989

By David R. Klug, Chris Gause, Troy L. Page

The Inter-Island Tunnel is one of two undersea tunnels which are part of the Boston Harbor Clean-Up Program. The tunnel is 7.7 km (25,160 ft) long, bored to a 4.3 m (14 ft) diameter in the Cambridge Argillite Formation and was finished to a 3.5 m (11.5 ft) diameter final concrete lining. The owner is the Massachusetts Water Resources Authority (MWRA) who is a regional authority responsible for overall design and construction. The tunnel's primary purpose is the transport of untreated effluent from Nut Island facility in Quincy, MA to the new treatment plant at Deer Island. Two sludge lines are installed for the transport of sludge from Deer Island to Nut Island. During construction the contractor encountered fault zones, fractured strata, and soft ground tunnel sections which liberated more ground water than was originally anticipated by the project designer. Ground water was controlled during mining and the placing of the final lining. The final lining of cast-in-place concrete had to be backfill grouted to cut off water inflows and provide contact for equal tunnel loading which is critical in long-term design. This paper deals with an engineered backfill grouting system which was the first of its type to be used in North America. It discusses the geological conditions encountered, the design criteria used in the evaluation process, and an indepth review of the various system components. It demonstrates how contractors can use knowledgeable and professional industry suppliers to solve difficult construction problems.

Jan 1, 1999

By Austin Whillier

INTRODUCTION Use of air-cooling or refrigeration equipment in underground mines is needed when conventional ventila¬tion techniques do not maintain acceptable environ¬mental temperatures in working areas. Because refrig¬eration can be very expensive, it should be implemented only after all possible and practical steps have been taken to eliminate or reduce heat sources in the mine. As an example, to prevent the main ventilation fans from contributing heat to mine air, they should be located in the air return and not in the air intake. It is particularly important to prevent any direct contact between hot water and ventilation air, especially in mines which encounter large flows of hot fissure water. Any water hotter than the prevailing wet-bulb temperature of the ambient air must be removed by pipes located as close as possible to the water source. This hot water must not be allowed free contact with the incoming ventilation air at any time during the water's passage out of the mine. Although insulation of the pipes carrying the hot water is seldom necessary, direct contact between the air and the water must be prevented so the warm water cannot evaporate. REVIEW OF COOLING PRACTICES Spot Coolers vs. Centralized Refrigeration To eliminate a few specific hot places in an otherwise cool mine, it is possible to use devices known as "spot coolers." A typical spot cooler that uses chilled water is shown in Fig. 1. These devices consist of self-contained refrigeration units that are often mounted on rail cars for haulage to hot spots. The cooling capacities of such spot coolers usually are limited to about 100 kW or 30 "refrigeration tons." A refrigeration ton represents a cooling rate that produces 1.0 st of ice in 24 hr; that is a cooling rate of 3.517 kW (200 Btu per min). Typically, the electric-power consumption to drive the compressor motor of the refrigeration plant in mines is 1.0 kW per refrigeration ton, corresponding to a coefficient of per¬formance of about 3.5. The principal difference between spot coolers and centralized refrigeration plants is the method of re¬jecting heat from the refrigeration system. Centralized refrigeration plants always discharge heat into the reject or return airflow of the mine; often that is the primary influence in selecting the location for the underground refrigeration plant. Heat from spot coolers usually is rejected into drain water or into air that is not flowing to the location requiring the cooling. As a result, spot coolers remove heat from troublesome hot spots in the mine, injecting that heat-plus the electrical energy used by the cooling unit itself-into other working areas where the ambient conditions are cooler. In effect, this is "robbing Peter to pay Paul." In deep, extensive mines, spot coolers usually pro¬vide only temporary and, over the long term, expensive solutions to localized cooling problems. Centralized re¬frigeration plants are preferred for such mines, with cooling distributed throughout the mine as required. Fig. 2 illustrates a typical underground centralized re¬frigeration plant. Centralized plants lend themselves to improved maintenance at reduced costs while offering the economy of size. Refrigeration plants of larger unit sizes have considerably lower initial costs than smaller unit sizes. The remainder of this chapter is devoted to large refrigeration plants, with no further consideration of spot coolers. Cost of Refrigeration Total Cost: The total cost of refrigeration amounts to about $200/kW of cooling per year (1981 US $). This total cost breaks down into approximately three equal parts: 1) Financial charges, which include the interest and amortization on the capital cost of the initial installation, and the cost of necessary underground excavations. 2) Operating and maintenance costs which include the cost of the electric power to drive the refrigeration plant's compressors. 3) Distribution costs which include costs for pump¬ing, insulated piping, and air-to-water heat exchangers. The local cost of electric power, the number of operating months per year, and the method of refrigera¬tion distribution all contribute to the actual costs in¬curred in a given application. However, the variations usually are limited to no more than ±30% of the $200/ kW per year total cost figure. Cost Per Ton: Refrigeration cost per ton of mineral production can be calculated if the annual production tonnage from the refrigerated section of the mine is known. In most cases, this cost will be less than $1 .00/t. However, in deep mines with high rock temperatures, such as those found in South Africa, the total cost of refrigeration can increase to several dollars per ton of broken rock. Distribution In deep extensive mines, distributing refrigeration often accounts for about half the total cooling costs. As a result, careful consideration and planning must be

Jan 1, 1982

By P. A. Anderson

Innovative solution management is being used at Coeur-Rochester, Inc. to increase bullion production and decrease overall costs. New operating programs call for reduced solution application rates to the heap to increase pregnant stream values at a lower and less costly plant flowrate because silver and gold extractions are equal regardless of leach solution application rate. Solar heating is used in the summer months to increase the core temperature of the heap for use in the winter months thus increasing silver extraction rate. This paper outlines the programs now in effect and the savings incurred because of them.

Jan 1, 1989

Many of the deeper ore reserves in current gold operations as well as new gold deposits consist of refractory ore types. As process development for these mineralizations remains time-consuming and costly, minimization of exploratory testwork and the early identification of feasible process routes is critical. Since most of the processing parameters are related to the mineralogy of the ore (Marsden & House, 1992), thorough mineralogical analyses during exploration and development phases have become a technical and economical requirement. The determination of mineralogy-related processing parameters and especially the gold mineralogy is even more important for these ore types because refractory gold ores consist of many transitions from partially leachable to totally refractory. In addition to sulfide and gangue encapsulation, various other refractory conditions may exist. Together with accessory mineralogical detriments (e.g., alteration/ slimes, reagent consumers, scale formation, mineral preg robbing) they may complicate process selection and hamper optimal plant operation.

Jan 1, 1993

By Ricardo D. Presnell, Erich U. Petersen, William J. Tafuri, Donald M. Hausen, Russell C. Babcock, William L. Gunter, Thomas R. Gibson, Douglas N. Halbe, Jay W. Hammitt

The Barneys Canyon orebody is a sediment-hosted disseminated gold deposit located 8 km (5 miles) north of the Bingham Canyon porphyry copper mine. Mineable oxide reserves are 8.6 million tonnes (9.5 million short tons) grading 1.64 g/tonne (0.048 oz/ton) gold. Host lithologies are carbonates and siliciclastics of the Park City and Kirkman-Diamond Creek Formations of Lower Permian age. Gold distributions are controlled by favorable stratigraphic units and associated alteration, and structures. Dominant alteration is decalcification and bleaching of carbonates, and argillization and bleaching of sandstones. Gold to silver ratios are greater than 1:1. Anomalous trace metals include arsenic, antimony, mercury and thallium. The Melco deposit lies 2.4 km (1.5 miles) southwest of the Barneys Canyon deposit. It is spatially associated with a steeply northwest-dipping siliciclastic breccia in the Kirkman-Diamond Creek Formation at the contact with underlying orthoquartzites of the Freeman Peak Formation. Both gold-bearing oxidized and sulfide lithologies are present, often in sharp contact. Mineable oxide reserves are 2.8 million tonnes (3.1 million short tons) grading 2.40 g/tonne (0.07 oz/ton) gold. Anomolous trace metals include arsenic, antimony, mercury and thallium, which are generally present in concentrations greater than those at Barneys Canyon, particularly in sulfide-bearing material. A spatial, temporal and genetic relationship is proposed between the Melco deposit and late-stage gold mineralization at Bingham Canyon, although both the Melco and Barneys Canyon deposits have many similarities to Carlin-type gold deposits.

Jan 1, 1990

By Erhard M. Winkler

The rapid decay and disfiguring of stone monuments in urban and desert rural areas has challenged conservators to protect stone surfaces from premature decay. They attempt to halt the natural process of stone decay and possibly to restore the original strength lost mostly by chemical weathering and the loss of binding cement. Ageneral solution is not possible because the physical and chemical characteristics must be considered for different stone types. The failures of stone preservation and restoration are greater in number than the cures. The need for repair of stone decay goes back to evidence of Roman replacement of decaying stone. The presence of excess water in buildings has long been recognized. Moisture tends to enter masonry from air in humid climates, a most important but often underrated factor (Fig. 1) suggesting that sealing should be the answer. Undesirable staining and efflorescence result in accelerated scaling. Today, the great variety of chemicals available to the modem conservator for sealing. consolidating, or hardening stone fall into two very different categories: surface sealers and penetrating stone consolidants, or a combination of both. SEALERS Sealers develop a tight, impervious skin which prevents access of moisture. Surface sealing has saved monuments from decay by eliminating the access of atmospheric humidity. Pressure tends to develop behind the stone surface by moisture escape. Efflorescence, crystal growth action, and freezing can cause considerable spalling (Anderegg, 1949). Flaking results when moisture is trapped behind the sealed surface. Yellowing and blotchiness are also frequently observed. The following sealants are in common use today: linseed oil, paraffin, silicone, urethane, acrylate, and animal blood on stone and adobe. Extensive cracking and yellowing has resulted soon after application. In the past many such treatments have created more problems than cures: 1. Linseed oil and paraffin have been in use for centuries. Embrittlement and yellowing occur rapidly because these are readily attacked by solar ultraviolet radiation. 2. Animal blood as paint has temporarily waterproofed adobe mud and stone masonry. The origin of blood paint has a religious background rooted in the Phoenician and Hebrew cultures. Instant water soluble dried blood can substitute for fresh blood. Winkler (1956) described the history and technique of the use of blood. 3. Silicones have proven very effective and are long lasting. In contrast, acrylates, urethane, and styrene are generally rapidly attacked by UV radiation (Clark et al., 1975). Sealing of Different Rock Types Granitic rocks have a natural porosity traced to 4.5% contraction of quartz, during cooling of the parent magma, compared with only 2% contraction of all other minerals; protection against the hygric forces may require waterproofing of granite in some in- stances. The Egyptian granite obelisk in London is an example. Soon after its relocation from Egypt to London, Cleopatra's Needle was treated, in 1879, with a mixture of Damar resin and wax dissolved in clear petroleum spirit; surface scaling became evident after half a year of exposure to the humid London atmosphere. The treatment of the ancient granite monument from Egypt has denied access of high relative humidity (RH) in London to the trapped salts inherited from the Egyptian desert and has protected the monument from decay (Burgess and Schaffer, 1952). The sister obelisk set up in Central Park, New York City, has fared less favorably because similar treatment was done too late, only after the salts hydrated and hundreds of kilograms of scalings disfigured the obelisk surface (Winkler, 1980). Surface coating of other common stones may be needed. Crystalline marble absorbs moisture from high RH atmospheres: dilation may ensue when curtain panels bow as the moisture starts to expand during daily heating-cooling cycles. A good sealer may prevent the moisture influx provided that no moisture can enter from the inside of the building. Limestones, dolomites and all carbonate rocks are subject to dissolution attack by rainwater, especially in areas where acid rain prevails (Fig. 2). The interaction of sulfates in the atmosphere with the stone can be halted by waterproofing to avoid the formation of soft and more soluble gypsum. The stone surface attack can be diminished if nearly insoluble Ca-sulfite crusts can form, instead of Ca-sulfate. Replacement of fluorite or barium compounds at the stone surface acts as a hardener, rather than a sealant. Sandstones have generally high porosity and rapid water travel can occur along unexpected routes and from any direction. Any surface sealing may do more damage by scaling and bursting than if the stone is left without treatment. Sealing of sandstones is therefore not advised at any time. Testing the efficiency of sealants: Several authors discuss waterproofing materials, silicones, urethanes, acrylates and stearates, as to their water absorption, spreading rates of water on the treated surface, water vapor transmission, resistance to efflorescence, and general appearance (Clark et al., 1975). De Castro (1983) measured the angle of contact of a microdrop (0.004 cm3) on a stone surface as characteristic of the wettability. Laboratory tests and limited field performance are described by Heiman (1981). The crest of a Gothic sandstone arch, which was sealed with silicone,

Jan 1, 1994

By Thomas Schultheis, William Heron, Paul Watson, Colin Warren

This paper describes the geology and geotechnics associated with construction of the Thames Tunnel, part of the UK’s Channel Tunnel Rail Link (CTRL). The 2.5km long twin tunnels run beneath the river Thames at depths of up to 40m and are currently under construction. They pass through varying geology comprising alluvium, terrace gravels and chalk with flints and are currently being bored using Herrenknecht mixshield slurry tunnel boring machines (TBM’s). This paper outlines the lithology and engineering properties of each geological formation and describes the geotechnical processes, potential hazards and difficulties experienced in the works. A summary is given into the extent of the investigative work in terms of route selection, tunnel design, TBM optimisation and further details are provided on the geotechnical aspects associated with the construction of the tunnel approach structures and the tunnels.

Jan 1, 2003

By P. Aparicio

The rheological properties of five kaolins, isostatically pressurized at 4 x10 Pa for 10 min in the presence/absence of water, was determined. Under dry conditions, measured viscosity values either decreased or remained the same. After treatment under wet conditions, measured viscosity values were 30-60% higher at high shear and 50-60% higher at low shear. These results correlate with variations in nanomorphology and structural order. Dry compaction degraded kaolinite crystals but wet-pressing appeared to cause an increase in the proportion of euhedral crystallites and a decrease in deformed crystals. Dry compaction decreased the low-defect phase proportion (ldp), but in contrast, the ldp in wet-treated kaolins remained constant or increased. Results show that hydrous pressure treatment produces a change in viscosity of kaolin suspensions, yielding the potential for improving paper coating performance, whereas anhydrous pressure treatment decreased or maintained the viscosity.

Jan 1, 2010

By Michael M. Maier

The manuscript of this paper was not available for publication when the Proceedings went to press. Should the author elect, he may distribute copies at the time of the Symposium.

Jan 1, 1986