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The molecular form of aliphatic amines precipitates in alkaline solutions when the amine solubility limit is exceeded and forms a typical colloidal system. The zones of mines precipitation and micellization are defined and it is shown that the appearance of a colloidal system in a certain pH range is a unique feature that makes weak electrolyte type surfactants differ from strong electrolytes. The formation of iono-molecular complexes reported in the literature is shown to be a pre-precipitation phenomenon. The zeta potential - pH curves for minerals and bubbles in the presence of amines in the pH range where the amine forms a colloidal precipitate are entirely determined by the precipitate. The pH dependence of the flotation of certain minerals using amines is discussed in the light of these findings.

Jan 1, 1989

By John K. Adams

Phosphorus may be incorporated into sedimentary rocks in at least four different ways: (1) by the accumulation of detrital mineral fragments, (2) by the accumulation of phosphatic organic debris, (3) by diagenesis and (4) perhaps by the primary precipitation of calcium phosphate. Based-on the petrographic examination of Cretaceous and Tertiary sediments from the northern and central parts of the Atlantic Coastal Plain, Diagenesis is the most important of these mechanisms. Both syndiagenesis and epidiagenesis are required to explain the origin of all the diagenetic phosphate mineral species which occur in the northern and central parts of the coastal plain. Syndiagenesis produced much of the coastal plain's apatite. It was operative below the sediment-water interface while the substrate was being compacted. Compaction forced pore waters, which were enriched in phosphate by the decomposition of organic matter, upward through calcareous sediments. The PO43- radicle replaced the CO23- and calcareous nodules, pellets and shell fragments were converted to apatite. Epidiagenetic reactions occurred in the subaerial environment where downward percolating meteoric waters carried phosphate in solution to cites where cation activity was sufficiently high to form new minerals. Vivianite may form where ferrous iron is available and wavellite and variscite may form in the presence of aluminum rich minerals. Textural evidence suggests that many of the reactions were repeated. The present day appearance of apatite, vivianite, wavellite and variscite in the coastal plain may represent several generations of diagenesis.

Jan 1, 1972

By R. G. Johnston

Minerals have many uses in paint systems. These roles include use as primary and extender pigments, sheen control, film durability enhancement, and rheology control. These and other uses of minerals in paints, and the effects of mineral quality variations on coatings performance are discussed. As coatings performance requirements become more demanding, tighter consistency of important mineral properties, such as particle size distribution and purity, is becoming increasingly vital. Future directions of mineral use to meet projected environmental restrictions and performance demands on coatings, including the use of advanced minerals technologies, are examined.

Jan 1, 1993

By Gunnar Nord, Per-Anders Persson, Duri Prader

The paper gives a short resumé of the findings of the joint US - Swedish "Mechanical Boring (MB) or Drill and Blast Tunneling (DB) ? Workshop" in Stockholm December 1976. New developments and trends in both MB and DB techniques in Europe since 1976 are described, and information is given on some interesting new projects. Differences in contracting principles between the US and Europe lead to different practices for preinvestigations, design, excavation and arbitration and legal affairs. It is shown that this often leads to a higher cost in the US than in Europe for similar excavation jobs. A typical US tunnel job also has more men on the site than a similar job in Europe. This adds to the cost difference and is only partly balanced by a slightly higher rate of excavation in the US. A comparison is made between two quantitative methods of predicting MB penetration rates. These are in reasonable agreement. A probable future development in machine design is an increase in cutter load towards perhaps 25 tons per disc where the tunnel diameter is large enough to house the machine size dictated by the size of the very large electric motors required. Recent European developments in drill and blast technique include improved methods for cautious blasting, precision hydraulic drilling of small diameter holes, and non-electric interval blasting techniques. These developments still keep the drill and blast method ahead of mechanical boring costwise for tunnels in igneous rock whereas for most sedimentary materials mechanical boring has a lead, particularly for long tunnels.

Jan 1, 1979

By J. Patrick Powers

In tunneling through water-bearing formations, the expense of controlling the water can have a major impact on overall project cost. The author has seen the cost of an eight-foot, finished sewer tunnel rise from under $500 per foot to over $1,000 when a water problem, anticipated as modest, became severe. There is need for greater professionalism in the approach to groundwater control. The days of the forked stick should be behind us. The basic technology exists. Its application is not yet widespread. This paper discusses predrainage; that is, the lowering of water in advance of tunnel excavation. Both free air and compressed air tunnels are considered. Examples from recent tunnel projects are described. SPECIAL NATURE OF TUNNEL DEWATERING Tunneling is unlike other excavations below the water table in a number of significant ways. The tunnel excavation is always on the critical path; if production slows or stops, there is no other work for the heading crews, no other work to carry the cost of service crews and job overhead. The dewatering commitment must be made well in advance. Construction of wells, and pumping down take time. After the heading reaches a trouble area, time is not available

Jan 1, 1997

By Bruce K. Cantrell, Stephen W. Stein, Kenneth L. Williams, David Hassel, Harvey Patashnick

In June 1992, the Mine Safety and Health Administration (MSHA) published the 'Report of the Coal Mine Respirable Dust Task Group; Review of the Program to Control Respirable Coal Mine Dust in the United States." As one of its recommendations, the report called for the accelerated development of two mine dust monitors: (1) a fixed-site monitor capable of providing continuous information on dust levels to the miner, mine operator, and to MSHA, if necessary, and (2) a personal sampling device capable of providing both a short-term personal exposure measurement as well as a full-shift measurement. In response to this recommendation, the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Center, initiated the development of a fixed-site machine-mounted continuous respirable dust monitor. The technology chosen for monitor development is the Rupprecht and Patashnick Co., Inc. tapered element oscillating microbalance. Laboratory and in- mine tests have indicated that, with modification, this sensor can meet the humidity and vibration requirements for underground coal mine use. NIOSH is continuing that effort by developing prototypes of a continuous dust monitor based on this technology. These prototypes are being evaluated in underground coal mines as they become available. This effort, conducted as a joint venture with MSHA, is nearing completion with every promise of success. The immediate benefit of this effort will be to researchers, regulatory personnel, and mine personnel, by permitting evaluation of specific mining practices to see which expose mine workers to excessive dust levels. Using this information, mine personnel can optimize mining procedures to reduce dust exposure. MSHA and the operators will also be able to use the dust concentration data to judge whether dust plan parameters are adequate to continuously maintaining environmental dust levels below the applicable standard. The second development recommended by the Dust Task Group was a person-wearable version of the continuous dust monitor. It will be a monitoring system designed to provide a measurement of worker exposure to respirable dust, both during and at the end of the shift.

Jan 1, 1997

By Deepak Malhotra, William F. Riggs, Edward C. Dowling

INTRODUCTION Mining companies are In the business of making an acceptable profit on their Investments, It became obvious in the recent recession that economic profitability/viability depends on being the lowest cost producer In order to compete on a global basis. The burden of achieving this objective falls on the mineral manager. He must strive to produce a salable product in an environmentally acceptable process while continuously Improving the profit margln.(1,2) Metal prices fluctuate on a regular basis. They directly Impact revenue and hence operating philosophy. The mineral engineer needs to develop an optimum operating strategy to meet his overall objectives, One would expect that, In the modem era of complex computer models, it would be easy to develop an economic model to maximize profits and/or cash flow. Discussions with mill managers Indicate that one mine/corporation's optimum operating strategy is not necessarily optimum for another. This paper approaches the problems from basics "Economics 101" and Illustrates the complexity of developing a universal model which can be applicable to all mines. Case examples are used to illustrate the need for better communication to avoid the basic economic fallacy “that optimization of segments leads to optimization of the whole system.” TECHNICAL MODELS Technical models are a prerequisite to the development of economic models because they provide the necessary Input data to these models, The flow of material from a mine through the sale of the finished product is shown In Figure 1. The ore Is mined and milled, and the concentrate can be stored for sale or smelted and refined In-house or at a toll facility. The finished product(s) are held In Inventory until sold either through existing contracts or in the spot market. [ ] Fairly reliable technical models have been developed for mining, milling and smelter operations. Mine plans are developed to provide a good Indication of the relationship between production and cut-off grade. It is easier to change surface mine plans than plans for underground mines. However, there are limits to maximum production that can be achieved with existing equipment. It Is possible that mine benches may not be developed to handle additional equipment, even If It was purchased to enhance production. More often than not, the cut-off grade Is lowered to Increase throughput goals.

Jan 1, 1993

Gaby Copper Mining?s Gabriela Mistral property is located in the Antofagasta region of northern Chile, at an altitude of 2,660 m (8,727 ft) above sea level. The reserve contains an estimated 562 Mt (620 million st) of oxide ore with an average grade of 0.41 percent total copper. The mine went into production in 2008. Gaby Copper faced the problem of having no reliable way to measure the solids level. This is a challenge that exists throughout the mining industry, where dust in the air and accumulation of solids on a sensor make accurate measurements difficult in areas such as transfer chutes, the rock box underneath crushers, silos and anywhere else that information is needed on the level of solids. The next-generation technology in the Sitrans LR560 radar from Siemens addresses this challenge. With a frequency of 78 GHz ? higher than previous generations of radar ? it provides a more robust signal for measuring in areas where there are high levels of dust accumulation. The Sitrans LR560 provides a signal beam angle of four degrees, significantly narrower than any other product on the market can offer.

Jan 1, 2014

By S. J. Parkin, P. Shead

Extraction of coal at Harworth Colliery is undertaken in the Deep Soft seam at roughly 1000m depth where the strata temperature is 42 "C. Production employs the longwall retreating method using high powered mechanised methods to extract coal at a rate of approximately 40,000 tonnes per week from a single face. This paper describes the climatic conditions encountered on a typical district , 6's district, where the initial ventilation set-up was as a typical U-type district which was antitropally ventilated. Under this initial set-up climatic conditions in the intake typically exceeded 30 "C effective whilst in the face area and in the return airway effective temperatures in excess of 32 "C and 33 "C were common . The paper then proceeds to describe the methods employed to attempt to improve the climatic conditions on the district, especially with regard to the coal face and return airways and describes in detail the effects of reversing the district airflow direction, employing homotropal ventilation, on the climatic conditions. The results of this reversal have been dramatic and have resulted in a substantial improvement in the climatic conditions experienced , however problems have been encountered with the control of methane gas since the changeover. The final part of the paper describes the results of computer simulations to analyse the effect of various ventilation designs on the predicted climate for future production districts in order to de- fine a district layout which will produce acceptable climatic conditions in the working zone without the need to use refrigeration techniques and which will improve methane gas control .

Jan 1, 1997

By Ward Sumner

The Jones Hill prospect is a Proterozoic age, volcanogenic, semi-massive to massive sulfide deposit. The deposit is located on the western edge of the Pecos greenstone belt in the southern Sangre de Cristo Mountains of northern New Mexico. The prospect is found in a block (West Block) of meta- igneous rocks, primarily diabase, metavolcanic rocks, and metasedimentary rocks (fig. 1). This assemblage is typical of lithologies found in the greenstone belt. Metamorphic grade is greenschist to lower amphibolite. The West Block is bound- ed on the west by Proterozoic age (1.7-1.4 b.y. by Rb/Sr), granitic plutons collectively called the Embudo granite, and on the east by Paleozoic sedimentary rocks, primarily sandstones, shales, and limestones of Mississippian and Pennsylvanian age. The mineralization occurs in a single horizon which has been overturned and cut into two blocks by a high-angle reverse fault (fig. 2). The mineralized horizon is found at the contact of felsic metavolcanic and rnetavolcaniclastic rocks with overlying intermediate metasedimentary rocks. The local stratigraphic sec- tion from bottom to top is as follows: 1) porphyroblastic quartz- sericite schist (originally a rhyolitic, subvolcanic intrusive); 2) quartz-sericite-chlorite-biotite schist (felsic metavolcanic and metavolcaniclastic rocks); 3) chlorite-talc-biotite-sulfide schist (altered felsic metavolcanic rocks); 4) carbonate-quartz-sulfide [ ] chlorite-tremolite-talc schist (mineralized exhalite); 5) quartz- chlorite schist (silicified tuff); and 6) amphibole-chlorite-feldspar- biotite schist (occasional mafic to intermediate metavolcanic flows).

Jan 1, 2013

With commodity prices rising again and market conditions stabilizing, the Metals Economics Group (MEG) found that most mining companies increased their exploration budgets in 2010. In the groups 21st edition of the Corporate Exploration Strategies (CES), MEG found a 44-percent rise in the estimated worldwide exploration total for 2010. MEG found that the estimated total 2010 budget for nonferrous metals exploration reached $12.1 billion, reinstating almost two-thirds of the industry?s $6 billion in cuts to exploration in 2009. Nonferrous exploration refers to expenditures related to precious and base metals, diamonds, uranium and some industrial minerals; it excludes iron ore, aluminum, coal, and oil and gas. In 2008, exploration budgets were at an all-time high of $14.4 billion. This capped a six-year run in which budgets rose. In 2009, nonferrous exploration budgets dropped 42 percent in 2009 as the global economic crisis and declining prices for almost all commodities took their toll on the industry. Metals prices - the primary driver of exploration spending - have improved markedly since bottoming in early 2009, and have traded well above their long-term trends throughout 2010. In response, major, intermediate and junior companies have all increased their aggregate exploration allocations in 2010. In particular, the significant improvement in the availability of equity financings for the juniors over the past 12 to 18 months has allowed this group to account for the largest share of the overall increase in exploration spending this year.

Jan 1, 2011

By Jeffrey A. Holcomb

INTRODUCTION The passage of Comprehensive Environmental Response Compensation and Liability Act (CERCLA/Superfund) as well as the Resource Conservation and Recovery Act (RCRA) and state laws, have placed added regulatory pressures on the mining industry. These laws which focus on the regulation of hazardous substances and wastes for the protection of the public health and welfare and the environment, present the potential for tremendous financial impacts and liabilities on existing mine operators and owners and/or potential mine operators/owners. This paper takes a brief look at these laws and presents an environmental audit procedure to identify environmental liabilities prior to mine land transactions. The environmental audit approach presented is an overview of the procedures that could be used to document, evaluate and inventory existing and/or potential environmental concerns. This audit procedure can be applied to developed or undeveloped properties and at active or inactive mining sites. REGULATORY OVERVIEW Mining environmental liabilities have been addressed in RCRA, Superfund, the Clean Air Act (CAA) and the Clean Water Act (CWA). Even though the U.S. Environmental Protection Agency (EPA) has determined that mining wastes will be treated as solid wastes under RCRA and not as hazardous wastes, these wastes could still bring about a great deal of financial liability under Superfund. The catch is if the mine wastes generated contain hazardous substances such as the heavy metals arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium, zinc and others as well as cyanide. Thus, it is not only important for a mine operator/owner or a potential mine operator/owner to know if the mine wastes generated are hazardous, but it is important to know if the wastes contain hazardous substances. Following is a brief overview of RCRA and Superfund and their potential implications. RCRA RCRA, which provides the basis for the regulation of solid and hazardous wastes, is applicable to active mining and milling sites. Within RCRA the definition of a hazardous waste is provided. This definition applies to owners and operators of mining and milling sites if the operator has stored, disposed or treated hazardous wastes on-site. If this is the case and if strict process control and waste management activities are not adhered to, environmental liabilities may be associated with the site. Superfund The 1980 Superfund law can be applicable to inactive mining sites or to inactive sections of an active facility. The provisions of Superfund call for the regulation of hazardous wastes and hazardous sub- stances disposal and release not only by the existing owner, but also for any previous owner. This concept of joint and several liability means that one party, as among many, can be held totally responsible for the costs of hazardous waste cleanup (Haller, 1987). Furthermore, liabilities under Superfund have also been applied back to past acts; thus, several mining properties, active or inactive prior to the 1980 Superfund law, are at risk of being placed on the EPA's National Priority List (NPL) for cleanup. Last years amendments to Superfund, known as the Superfund Reauthorization Act of 1986 (SARA), provided some significant developments for the mining industry. The major requirement of the amendments as it pertains to owners or operators of mining sites is that the EPA must revise its present Hazard Ranking System (HRS). This is important be- cause in most cases the primary reason for several mining sites having been included on the NPL was due to the large volume of wastes generated. As is typical at most mining sites, large volumes of low toxicity wastes are generated and the current HRS model prejudices against this. It should be noted that this provision only applies to sites that are not already on the NPL or have not been proposed for inclusion on the list.

Jan 1, 1987

By B. J. Arnold

Froth removal rate is perhaps the most important parameter in scaling up from laboratory tests to plant froth flotation circuits. The WEMCO froth factor, the percentage of the froth height over the lip of the cell, accounts for the difference between laboratory and plant froth removal rates. As laboratory tests are generally run with a high pulp level, laboratory results are directly comparable to plant results only when a high froth factor (high pulp level) is run in the plant. When a plant does not have a high pulp level, laboratory results must be modified by using a ratio between laboratory and plant kinetics to predict plant results. This ratio, which accounts for the froth factor is important in testing any new reagents or reagent dosage levels. CQ Inc. researchers have used predictive scale-up equations using this froth factor coupled with equations for kinetics and the residence time distribution in the froth flotation cells. These equations show that modifying the froth factor in the plant can have a large impact on flotation cell yield and reagent use. EQUATIONS DESCRIBING FROTH FLOTATION Scaling up from laboratory- to plant-scale coal froth flotation has been the subject of much research and debate over the years. Determining the proper rate equation to describe flotation kinetics and an equation to describe the residence time distribution in a bank of flotation cells have been particular areas of study. As shown in Tables 1 and 2, various rate equations and residence time distribution equations have been proposed in the literature. These equations consist of one or two parameters giving the rate constant(s) in units of time-1 and a parameter for recovery at infinite time, [Roo]. Dowling, Klimpel, and Aplan (1985) evaluated the rate equations in Table 1 for their ability to fit froth flotation kinetic data and found that all of the equations give reasonably low standard errors. Several of these equations, however, proved to have superior confidence limits for the parameters. Other equations have also been proposed to describe the recovery versus time profile. Most recently, Diao et al. (1992) proposed a first-order form with a sine wave distribution. As indicated in Table 2, investigators have suggested many equations to describe the residence time distribution in continuous froth flotation. To measure the water residence time distribution in a bank of cells, a soluble tracer is often used, with the level of tracer being measured over time at the tailings discharge. This response is then put on a dimensionless basis as described by Austin et al. (1984) in order to compare mixing behavior between cells or under different conditions. Coal flotation cells are generally of the flow-through or hog-trough variety allowing for some degree of backmixing and short-circuiting. While the water residence time distribution (see Figure 1) at the end of one cell in a bank of 1.4 cu ft WEMCO froth flotation cells may approximate perfect mixing conditions (Arnold, 1989), the water residence time distribution at the end of a bank of cells does not. Figure 2 shows the RTD for various flotation cell types compared to that for perfect mixers in series. To better describe the water residence time distribution in coal froth flotation cells, Van Orden (1986) used an equation similar to the perfect-mixers-in-aeries equation. This

Jan 1, 1993

By L. R. Freitas, A. K. Resende, J. A. Oliveria, K. L. Gonçalves, L. F. D’Assumpção, L. R. Lage, J. D. Neto, F. Viveiros

Pará Pigmentos S.A. (PPSA) is an association between the Brazilian companies CVRD and CADAM, Mitsubishi Corporation of Japan, and the IFC (World Bank) created in 1992 in order to recover kaolin from Rio Capim deposit, northern Brazil. Commercial production at PPSA started in August 1996 using a process comprising mining and beneficiation at the mine site, pumping through a pipeline and drying/loading at the port site on the Amazon river estuary. Presently, all PPSA production is concentrated on 82% <2um, high-brightness coating clay shipped in bulk. In this paper, a detailed description of the development of PPSA beneficiation process is presented. The results of laboratory and pilot plant studies under- taken to develop alternative grades of clay, such as delaminated and calcined kaolins, are also discussed.

Jan 1, 1998

By Evans U. Jegbefume

A plane strain two-dimensional finite element model employing the method of negative reaction loading has been used to model roof collapse and subsidence resulting from the underground gasification of coal in regions of soft overburden such as that found in Texas. The model included dry zones of rock around the cavity. Roof collapse was included by considering the final state of stress in the elements and removing those that had undergone tensile failure. The two-dimensional plane strain model was extended to include thermal loading and thermal softening of the roof rock. Roof collapse initiation and growth of the cavity were modelled by examining the portion of the rock immediately above the cavity under thermal and hydrostatic load. The model was extended to include linear creep using the method of incremental strains. The overburden was modelled as a generalized Kelvin material.

Jan 1, 1982

By John E. Kinnison

The Mission mine, located in southern Arizona near Tucson, is a recently developed open pit which produces 15,000 tons per day of copper ore. The mine lies on a wide and gently sloping bajada sweeping northeasterly from the Sierrita mountains. It derives its name from the nearby Mission San Xavier del Bac, built circa 1700. The ore body is everywhere covered by about 200 feet of alluvium, as are the adjacent Pima and Palo Verde mines. The geology of the Mission deposit is known principally through the study of diamond drill holes spaced 150 to 300 feet apart. The open pit is in an infant stage and has not yet revealed much of the deposit, although information obtained there by the operating staff, and from a few thousand feet of exploratory underground workings, has added significantly to the general fund of knowledge. Permission to publish was granted by the American Smelting and Refining Company. I am indebted to Kenyon Richard and J. H. Courtright for criticism of this paper and for their direction during the several years in which I studied the Mission deposit. Acknowledgment is given to consultant in petrography, Robert L. DuBois of the University of Arizona. The only previous publication pertaining directly to the geology of file Mission deposit appeared in 1959 (Richard and Courtright), and may not be everywhere readily available. Cooper (1960) has published a short paper on the district

Jan 1, 1963

By HASAN SERKAN GOKCEN, SERKAN CAYIRLI

Manufacturers have improved various stirred mill types to be well adapted to fine and ultrafine grinding applications. These stirred mills, which are operated in wet or dry conditions, may be classified as horizontal — such as AHM-horizontal agitated media mill, IsaMill and Drais mill — or vertical — such as tower mill, Vertimill, Maxmill, Stirred Media Detritor and ATR vertical agitated media mill. The main difference between vertical and horizontal structures is in their operational variations. Additionally, the scaling-up of mills is also an important parameter for selecting the suitable orientation [1]. The purpose of this study was to investigate the dry grindability of calcite powders in a vertically and horizontally orientable laboratory batch-type stirred mill. The experimental results were evaluated using stress intensity analysis. The results showed that the d50 values decreased with increasing stress energy down to a certain point and then increased for both milling orientations. Even though the optimum stress energies for both vertical and horizontal orientations were in the range of 1 × 10−3 to 5 × 10−3 Nm at 750 and 1,500 kJ/kg energy consumption, the product size was finer for the horizontal orientation at the same stress energy value.

By J. L. Hoover, P. W. Conrad, J. Downey, S. Parrow, S. Rosenthal

The goal of the drill bit consumption study was to develop an equation(s) based on various components that affect drill bit wear and use that equation(s) to estimate the consumption of bits during production drilling. Drill bit data from various geographic locations were compiled and used to develop linear regression equations using the Microsoft Excel software package. Multiple drill bit consumption equations were developed and statistical analysis was used to verify the accuracy of those equations. The equations will allow mining companies to more accurately forecast drill bit consumption when evaluating new mine properties. This capability becomes increasingly beneficial to forecasting as the cost of consumables increases.

Jan 1, 2012

By I. Nishkov, L. Alexandrova

The kinetics of froth flotation and the three-phase contact (TPC) parameters are studied at temperatures varying from 20°C to 40°C. The material floated consists of glass spheres and a quartz particles with various diameters. Dodecylamine hydrocloride (DDAHCI) is used as a collector. The equilibrium three-phase contact angle is measured with a microscope technique using the modified Mingins-Scheludko method. Using a Wilhelmy method, the temperature effect on the surface tension of the DDAHCI solution is determined. The formation of the thin film on a polished plate of vitreous silica and the expansion of TPC is monitored by means of a metallographic microscope and recorded on a attached camera at different temperatures. The experimental data show an intensification of the flotation kinetics at 30 and 40°C in the case of small particles. Such an intensification is not observed with the larger particles. The cause for intensification of the flotation kinetics is sought for in the dependence of the TPC rate of expansion and induction time on temperature.

Jan 1, 1995

By Mark E. Smith, Gerald J. Gierszewski

Introduction The purpose of this paper is to present a procedure used by the authors for evaluating and designing soil liner systems. This method is particularly valuable in evaluating various treatment schemes for chemically amended soil liners. A tabulation of laboratory test results on various soil types are presented to quantify the effectiveness of certain treatments. A typical liner design program includes developing and proving soil borrow sources, designing the cross-section of the liner system, developing construction specifications, and providing construction services to ensure the intended product is achieved. Material Source Development The first step in designing a soil liner is to identify and evaluate suitable borrow sources within an economical haulage range. This is best done in a two step approach: a reconnaissance level investigation to identify target areas and a detailed evaluation of those targets. Reconnaissance: The goal of the preliminary investigation is to locate potential borrow sources for liner quality soils. This includes all natural materials which can be compacted, chemically treated, or otherwise amended to yield an installed permeability at or below some target value. This requires utilization of all available data sources: Soil Conservation Service, BLM, aerial photos, USGS geologic maps, and project geologist records. The goal at this stage is to locate shallow deposits of favorable soil types. The Unified Soil Classification System provides an excellent first pass grouping. Clays, clayey sands and silts are the most favorable soil types, although silty sands and occasionally clayey gravels can make excellent liners, and are often amenable to chemical modification. The lowest permeabilities are generally achieved with CH, CL and MH soils. Once preliminary targets have been identified using visual examination, laboratory classification tests should be performed to further refine the selection. Testing at this stage should include gradation, plasticity and hydrometer analyses. Additionally, "preg-rob" testing should be done as early as practical. Preg-rob is a phenomenon where gold or silver ions in solution associate with the clay, or other, minerals. When this occurs, a portion of the gold or silver leached from the ore is actually tied-up by the clay and thus a reduces recovery. Testing for this consists of agitating a small sample of the soil in a solution containing dissolved gold or silver, preferably of similar chemical make-up as the solution which will contact the actual liner. The solution and soil are assayed before and after agitation to determine loss to the clay. A reliable estimate of the hydraulic conductivity, commonly referred to as permeability, can be developed from the D10 value by the use of Hezen&apos;s formula: K = 100 (D1012 This relationship is limited to soils where the finer particles do not move due to the force of flowing water (i.e.: "hydrodynamic stabilitym)(1). Additionally, the effect of platty particles on permeability is not as predictable as the effect of equidimensional particles. D10 is the sieve opening size at which 10% of the material is finer. Plasticity is also important from several standpoints. Constructability is directly related to plasticity. Very plastic clays and non-plastic silts both tend to be difficult soils, while medium plastic clays and clayey sands are generally very desirable. Post construction performance is also related to plasticity (e.g. swelling, shrinkage cracking, frost heave, etc.). Additionally, low plasticity silts and silty sands generally do not respond well to chemical amendment. Source Development: The result of the reconnaissance evaluation should be an estimate of the relative probability of developing a suitable borrow source within an economical haul distance. Of course, "economical distance" depends on the degree of handling and treatment the borrow material requires, as well as the cost of synthetic alternatives. The purpose of the detailed investigation is to prove out quantity and quality of material sources, and determine design parameters such as degree of compaction, mixing, treatment and thickness of liner. The emphasis of the testing program should be permeability and strength. Strength becomes increasingly important as the slope of the liner and the height of the heap increase. Permeability testing should evaluate the effects of compaction, water content, mixing and chemical treatment where appropriate. The effects compaction and water content during compaction have on

Jan 1, 1987