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By Jim Dunn

For decades many of us who are associated with the mineral industry have tried to show the public its economic and strategic importance. Some of the mineral industry's proponents have been politically powerful figures and have been widely quoted. Yet, as measured by public opinion, legislative support, or almost any other standard, our efforts have been inadequate. It is apparent that a set of environmental beliefs that discredit industry, firmly held by a number of idealistic persons, has had wider coverage in the media and in schools than has the mineral industry's message. Although the fervor of our idealistic friends is often unfounded and, their stands unscientific, they must be considered seriously. Unless we address the issues in terms the idealists will understand, the mineral industry will have little influence on them or on the general public. A. striking thing is that, quite often, translation of idealists' views into action has been counterproductive. The reason is obvious. Excessive amounts of money and energy have been spent on relatively minor problems. The common result is that larger problems have been created. It may be possible to help anti-industry idealists understand their own dependence on minerals, and thus render their views more realistic, if they are shown more effective ways to reach their stated goals. If those goals can be shown to be held in common by all sensitive human beings -- including those in business and industry - the dialogue becomes one of how to achieve common ends. Individual mining companies acting by themselves have little possibility of success, and companies working in unison through trade associations have not been successful. Further, it is unlikely that industry in general can be successful in changing minds unless it seeks outside help. But friends among those who influence public opinion have been hard to find. Historically, help from media has proven difficult to get. Nor has enough help from educators been forthcoming. Yet, a war is going on in the technological, philosophical, and political trenches, even though much of the public is not aware of it. For the first time in years, there is row a significant and growing number of eloquent and brilliant thinkers on the side of free enterprise and industry, many of them environmentalists, but without the anti-industry mind-set. They have had remarkably little help from the private sector or even from the present administration. Industry may do far more for itself in the long run by encouraging these brave but bruised individuals and their organizations than by trying to work alone. These friends of free enterprise are working against a seemingly stacked deck relative to much of the media, the bureaucracy, and the educational system. However, despite their problems, their success to date has been remarkable. With more cooperation from industry they should do even better.

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 K. Saberyan

A technique is described for the solvent extraction of zirconium. In this method, zirconium has been extracted quantitatively from 0.005 M sodium salicylate solution at pH 2.5 - 3 using 0.01 M triphenylphosphine oxide dissolved in toluene as an extractant. Zirconium has also been recovered quantitatively from 0.2 M potassium thiocyanate solution, but extractions in nitric and hydrochloric acids (as media) were negligible. The resulting extracted metal ion has been stripped with sulfuric acid (0.5 M) and determined with inductively coupled plasma atomic emission spectrometry. This method has been applied successfully to achieve 95% recovery of zirconium from zircon concentrate.

Jan 1, 2010

By John F. Shea

When Dick Robbins asked me to give a keynote address, I felt it might be in order to review some of the practices and techniques used in tunneling and work up to some of the concepts now used to mine and construct tunnels. Needless to say, there have been many changes in tunneling technology and also many changes in the Safety Codes controling them. An example of this latter change was the fact that in 1931, my father excavated the Owyhee Tunnel No.5 with gas locomotives. He was able to do it because there was no natural gas in the rock and the ventilation system was designed to free the tunnel atmosphere from powder and exhaust fumes. Today OSHA rules would never permit gas locomotives underground, although there were no incidents on this particular project. One of my first tunnels, as Project Manager, was the Clear Creek Tunnel for the Bureau of Reclamation. Our method of handling muck was the Conway Muckers. This unit was a valuable improvement to the hand mucking of previous generations. The Conway was also used in our Navajo Project, in New Mexico. Unlike the Clear Creek project, where water was one of our main problems - up to 7,200 gallons per minute, at a pressure of 395 pounds per square inch - in the Navajo Tunnel, we had a mixed face which caused a major problem with our support system. In one of the Navajo Tunnels, there was a major cave-in, when the squeezing shale came in during an attempt to strengthen the support system. Although moving shale was not a constant problem, there were areas where the shale was five to six feet above the spring line.

Jan 1, 1976

By Carl G. Bock

INTRODUCTION Rapid transit systems involving near surface tunneling in hard rock are becoming more numerous, especially along the northeast corridor of the East Coast. Tunneled systems are under construction in Washington, D.C. and are being planned for Atlanta, Buffalo and Baltimore. Near surface tunneling is defined for this paper as being that in which the crown is 100 feet or less below ground surface. For Rosslyn Station, the total cover ranged from 52 to 70 feet. The rock cover, however, ranged from 40 to 50 feet which is slightly less than the station height and about two-thirds of its width. Rosslyn Station (Fig. 1) is the only station excavated completely in hard rock in the Virginia portion of the 98.5 mile Washington Metropolitan Area Transit Authority's (WMATA) rapid transit system. The station site, oriented in a north-south direction beneath a main thoroughfare and flanked by multistory office buildings, was fixed by the need to serve a dense population center at a specific location and geologic conditions were a secondary consideration in siting. There was no previous underground rock excavation in the Washington Metropolitan Area of the size and scope of Rosslyn Station that offered a practical case history guide to the geologic conditions and excavation problems to be encountered. GEOLOGY The regional geology of the Washington Metropolitan Area is divided into two physiographic provinces by the northeast trending Fall Line (Fig. 2). Northwest of this boundary is the Piedmont Province

Jan 1, 1974

By S. Rezaei

Moving ground in the mining industry is almost inevitable; however comprehensive awareness of these movements is necessary to mitigate risk. Monitoring of displacements caused by mining is a key tool for geomechanical risk management. Good monitoring may prevent unexpected failures and protect personnel and equipment. Many displacement monitoring techniques are available, however not all are reliable, accurate, and cost effective. Close range photogrammetry (CRP) is a monitoring method with high accuracy, reliability, and cost effectiveness; and has the ability to measure places that are inaccessible. In CRP, some series of photos are taken in different positions with different angles at different time intervals depending on the displacement rates. These photos are processed using PhotoModeler software and 3D models are made. By comparing 3D models, displacements can be measured. This method has been demonstrated at the Freeport-McMoRan Safford Mine in Arizona. A fault related instability in part of the pit is reactive to mining, and provided an opportunity to compare results between traditional monitoring methods and CRP. In this project, multiple series of photos were taken at different times using a Canon 5D Mark III digital camera, then PhotoModeler software used to make 3D models for each specific measurement event. Movement rates were determined by comparing different 3D models. These results are then compared to results of other monitoring methods to validate the CRP displacement method.

Feb 27, 2013

By William R. Groseclose, Cecil E. Tackett

Since 1965 when the first mole was used on Bureau work, the Bureau of Reclamation has completed 17 tunnels of over 5,000 feet in length. The longest was 12.8 miles. Total length of the 17 tunnels was 376,207 feet, or over 71 miles. The finished diameter varied from 7 feet 0 inch to 18 feet 0 inch with 82 percent (58 miles) being less than 12 feet 0 inch in diameter when lined. All of these tunnels except one are gravity flow, water conveyance tunnels with relatively flat gradient. One is a low-head pressure tunnel. All were constructed by contracts resulting from fixed-price bids. Starting in 1964 the Bureau of Reclamation initiated the practice of giving several options in the specifications on methods of tunnel excavation. Since that time, construction work has been completed on 17 tunnels. Of this number, 11 were mole excavated and 6 were excavated by conventional drill and blast methods. In general, there has been 2 feet of mole excavation for every 1 foot of drill and blast. Cost comparisons are based on only 13 tunnels because the Bureau has 4 recently completed tunnels that have pending claims; therefore, final cost data are not available. Some definite trends show from the data available; however, the number of completed tunnels in some categories is so small the results cannot really be considered a trend. As more data become available, the indications will become more reliable. The information is presented to indicate general trends and comparisons and cannot be meaningfully used for a one-on-one comparison because of individual tunnel differences not considered.

Jan 1, 1974

By Robert L. Llewellyn

The Wharton No. 2 Mine of Eastern Gas and Fuel Associates is located about 60 miles south of Charleston, West Virginia in Boone County. Daily production is 6,000 T.P.D. on a two-shift basis. The Hernshaw Seam is mined by conventional equipment with one continuous miner in areas where conditions are suitable. The plant is on Cow Creek .Branch of Pond Fork, which in turn flows into the Little Coal River at Madison, West Virginia. When the mine was opened in 1948, plans were developed to build a dual Baum jig plant complete with mechanical and thermal drying, and because full production would not be reached for several years, it was decided to install only one Baum jig setup although the complete structure was erected. This phase of the plant was placed into operation early in 1949, The rated capacity was about 300 T.P.H. of 5" x 0 raw feed to the jig. Being a drift mine, the 10-ton mine cars are dumped at the Headhouse, crushed to 8" in a double roll crusher, conveyed 780 feet downhill to the picking .house where the +5" slate is removed by pickers. All coal is crushed to 5" and 5" x 0 is conveyed 150 feet to the cleaning plant. Further describing the plant growth, the second jig setup was installed in 1954 to clean the increased production. During this operating period, exhaustive tests had ,been run on the plant bleed which was an overflow from the large sludge tank located inside the plant, When the second jig addition was undertaken, 5-14' diameter and 12-8" diameter cyclones with a 9-disc filter were installed for the solids recovery and water clarification system, However, the circuit was not closed and a bleed of part of the overflows from the 8" diameter cyclones was still necessary, To comply with the State Water Commission regulations on stream pollution abatement, four pumps in series were installed to discharge the waste water behind the refuse pile.

Jan 1, 1959

By John S. Egbert

Many of you are familiar with the Washington Metro Project. However, inasmuch as some may not be, and others may want to refresh their memories regarding certain facets of the project, I will cite a few summary details about the rail transit system we are constructing. That summary will also give each of us a common point for departure as I develop the principal thoughts that I want to leave with you. The Washington Metropolitan Area Transit Authority (WMATA) is an interstate agency established by Compact between the District of Columbia, Maryland and Virginia and approved by the United States Congress. Currently, the Authority has approval to build and operate a 101-mile (162.5 km) regional rapid rail transit system as shown on Appendix A. Of that total, 38 miles (61.2 km) will be in D. C., 32 miles (51.5 km) in Maryland and 30 miles (48.3 km) in Virginia. (Mileage figures, because of rounding error, do not add to 101 miles.) Referring again to the 101-mile total, 48 miles (77.2 km) will be underground, 42 miles (67.6 km) on the surface and 10 miles (16.1 km) on aerial structures. Of the 48 miles (77.2 km) that are underground, 15 miles (24.1 km) are rock tunnel, 14 miles (22.5 km) are earth tunnel, 0.5 miles (0.8 km) 9.s sunken tube and 19 miles (30.6 inn) are cut-and-cover construction. The system will include 86 stations, with 51 of them underground. Referring again to the full 86 stations, 43 will be in D. C., 23 in Maryland and 20 in Virginia. We currently have 37 miles (59.5 km) of line and 41 stations in operations as shown on Appendix B. Also shown on Appendix B is another 16 mile (25.7 km) increment and 13 stations which have been substantially completed, but are not yet in service. Additionally,

Jan 1, 1981

By Brain W. Lawrence

Sublevel stoping generally is a large-scale open stoping method. It sometimes is referred to as long-hole or blasthole stoping. This method usually is applied to strong ore bodies that require minimal support and are surrounded by strong country rock. The ore body should be fairly regular in shape and well-defined. The dip of the footwall normally should be sufficient to allow broken ore to gravitate freely, although the method has been adapted successfully to mine some of the flatter ore bodies. Sublevel stoping is not dependent on the width of the ore body. Widths of less than 6 m (20 ft), however, make the utilization of long-hole drilling techniques more difficult. The main criteria for sublevel open stoping are competent ore and stable host rock, regular ore boundaries, and a footwall dip that exceeds the angle of repose of broken ore. Basically, the method entails providing access to the ore body at various subintervals between the main haul- age levels in order to drill and blast the intervening ore. Stope drilling is carried out from drilling drifts on the sublevels, and the ore is blasted in slices towards an open face, which generally is vertical on the downholes and may be inclined towards the open face for the up holes. The blasted ore gravitates to the bottom of the stope and is collqcted through drawpoints. Fig. 1 illustrates a typical sublevel stoping mine. The method requires extensive ore body development with relatively high capital expenditures. How- ever, much of the development is in ore, and production costs are comparatively low. Productivity rates are in the 13.6 to 27.2 t (15 to 30 st)/manshift range. The drilling, blasting, and loading operations are performed independently, and equipment utilization is high. Large outputs can be obtained with few units and limited personnel. Dilution with waste rock may occur if ore boundaries are irregular or if caving occurs, but 100% of the ore within the stope usually is recovered. Pillar recovery sometimes is a problem. It is at this point that most of the waste dilution occurs. At the time data was gathered for this report (1973), the sublevel open stoping method was used by more than 21% of the metallic ore mines in the US (9 out of 42 mines producing 1088 + t/day (1200 + stpd) and provided more than 12% of the total metallic ore production from these mines. DEVELOPMENT Access to a sublevel open stope mine is gained by a slope or shaft that is normally sunk in the footwall of the ore zone, away from any possible effects from blasting or other production operations in the stoping process. Main level interval is selected and usually varies from 45.7 to 121.9 m (150 to 400 ft), depending on the vertical extent of the ore body, the number of drawpoints required to maintain output, and the eventual stope height. The main haulage drifts are located at the bottom of the stope horizon, either directly in ore or in the footwall, with access crosscuts at intervals. Raises are driven up through the ore to connect to the level above and provide access and ventilation to the sublevel drilling drifts, which are driven horizontally in the ore for the length of the stope. Depending on the drawpoint system to be used, the stope is either undercut by a raise-and-cone system, from a scram or slusher drift, or simply provided with a drilling drift from which access is made at intervals to the main haulage level. A raise driven either at the end or in the middle of the stope (if stope access is from both ends) provides a start for opening up a vertical slot across the stope to establish a free or open face for long-hole drilling and blasting. Sublevel stoping has proved to be a relatively safe and economical system.

Jan 1, 1982

By W. J. Maloney, H. E. Tuneblom, A. J. Smith

The development of a large regional water supply in Southern West Virginia faced several hurdles. This paper deals with the design and construction of the intake shaft where a combination of cutting edge mechanical excavation technologies were utilized to produce a world class project.

Jan 1, 1999

By Martha McJunkin, Lawrence Pietrzak

This paper describes and demonstrates the application of systems analysis and mathematical modeling techniques in the planning of actual tunnel projects and research and development to improve tunneling techniques. A recently completed tunnel project located in Utah is used as an example. Although cost estimating computer programs are used in tunnel project planning, the introduction of performance modeling, simulating the time to excavate, has added advantages that are explored here. The performance/cost tunneling model (TM) described herein mathematically simulates on a high-speed digital computer the important activities of a number of tunneling techniques accounting for activity interactions, variable external environments, mechanical failure, and other uncertainties. A cost accounting segment is included to facilitate cost-effectiveness comparisons. It is shown that, when combined with informed judgment and appreciation of limitations, the TM can be a useful tool that may help improve tunneling operations and cost estimation, for example, by achieving more balanced system designs or bounding the performance/cost implications of geologic and other uncertainties. Ultimately, this might lead to more competitive bids and greater profits. The need for systems analysis and modeling in tunneling research and development (R&D) is well recognized and documented.(1-5) In R&D one must seek broadly useful solutions to the basic problems of face fragmentation, materials handling, ground support, and environmental control. These solutions must take account of the interdependence of these elements and, for a variety of ground conditions, the limitations or constraints that any innovation in one element may impose on total system performance and cost. In this regard the structure and logic of the TM has been kept as simple and modular as possible so

Jan 1, 1974

By A. L. Wilder

Coeur d'Alene Mines Corporation's newest precious metals property is located in the old Rochester Mining District approximately twenty-five miles northeast of Lovelock, Nevada. Built at an elevation in excess of 6 000 feet, the Coeur-Rochester gold silver heap leach property encountered cold weather operational problems typical of most northern Nevada heap leach properties, soon after the start-up of operations last fall. Due to the size of the heap area under leach at Rochester, it was decided that 1 the usual practice of spraying to an "ice field" and waiting for the spring thaw was impractical. Further, the delivery schedule for a solution heating system of the size required was unacceptable. Accordingly, Rochester personnel embarked on a program to seek out a leach solution distribution system that would enable an operation through the winter and yet be cost effective. The findings of this program were rather dramatic and, as a result, the whole perception of heap leach solution application at Rochester has changed forever.

Jan 1, 1988

By Thomas C. Atchison, James J. Olson

INTRODUCTION Technologic progress depends on new and innovative ideas, the practical application of these ideas, and finally as the technology is developed and demonstrated, the engineering improvement or replacement of existing capabilities. In many areas the new ideas, although known, are not immediately put to practical use in all applicable fields. Good technologic forecasting for research and development within the excavation field coupled with adequate technology transfer is necessary to ensure timely application of innovative ideas to remove bottlenecks in the total system. The purposes of this paper are (1) to show the potential ability of technologic forecasting to meet future demands in rapid excavation through the acceleration of excavation rates by research and development in several related technologic fields, (2) to provide a brief review of the initial development of the ARPA (Advanced Research Projects Agency) Rock Mechanics and Rapid Excavation Program, (3) to draw attention to the research projects completed or underway in the FY 1970-1972 ARPA program and explain where information or program results can be obtained, (4) to summarize the progress and accomplishments of applied research contracts in the rock disintegration element of the ARPA program, and (5) to discuss the research directions planned for the remaining years of the program. The Advanced Research Projects Agency (ARPA) is a group within the Defense Department responsible for conducting basic and applied research and development for advanced projects assigned by the Director

Jan 1, 1997

By Thomas M. Larimer

Prior to April, 1961, the coal charge to Clairtonts coke oven batteries was 3" x 0" mine waslied coal having approximately 6.0% to 7.0% moisture. Even at this size and moisture content, the arching, rat-holing and hang-up was excessive and the effective live storage of coal was only 60% to 70% of the rated capacity of the coal bunkers, depending upon the moisture of the coal. In addition, many production delays were encountered in the time and methods required to fill the larry cars. The need for an improved metallurgical coke led to the introduction of pulverized coal to a portion of the plant in 196 1. When the full potential of the pulverizing equipment was realized, we were able to serve seven batteries in our second unit of batteries with pulverized coal through two coal bunkers. The discharge hoppers of these bunkers were equipped with air vibrators to assist the flow of pulverized coal into the larry cars. The vibrators were helpful in this respect but required considerable maintenance and caused damage to the bin plates.

Jan 1, 1968

By Corby G. Anderson, Sheikh Abdul Rezan Sheikh Abdul Hamid, Sanjith Udayakumar, Ahmad Fauzi Mohd Noor, Teuku Andika Rama Putra

Chemical and mineralogical characterization of Malaysian monazite, a phosphate mineral, bearing rare earth elements separated from the tin tailings originated from Ipoh, Perak, Malaysia, was performed in this paper. The study aims to collect detailed information on the chemical composition, crystal phases, and microstructure of the mineral monazite concentrate that would aid to optimize the subsequent hydrometallurgical processes for high-efficient separation of thorium and other associated rare earth elements. A systematic characterization study of the concentrate was conducted using techniques such as optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR). These techniques analyzed the morphological details on the surface, elemental analysis, and mineral association assessment and identified the surface functionalization groups. The bulk composition and the mineral phases in which the elements are present were studied by wavelength-dispersive X-ray fluorescence (WD-XRF) and X-ray diffraction (XRD) studies respectively. The XRF analysis confirmed the presence of Ce, La, Nd, Pr, and Y (rare earth oxides: REO’s ~ 60 wt.%) while thorium dioxide (ThO2) accounted for 7 wt.% of the total composition. Traces of Ca, K, Al, Fe, Ti, and Mn were also confirmed by SEM elemental mapping. The XRD results confirmed that the concentrate was primarily composed of monazite (Ce, La, Nd, Th (PO4)) along with minor impurity phases of quartz. Automated mineralogical analysis was used as a confirmatory tool to corroborate the preliminary evidences. Based on the particle size distribution analysis supported by SEM, the majority of monazite grains were found to be present in the size range of 170–210 μm. Strong bands of PO4 and SiO4 were observed in the IR spectra corresponding to the phospho-silicate matrix of the REE mineral.

By Terry B. Linde, William M. Dowall

The recently completed In-Pit Crushing and Conveying Project at Phelps Dodge's Morenci Mine is rated among the world's leading materials handling projects. The operation involves the crushing and transport of more than 109,000 tonnes per day of copper ore, utilizing regenerative conveyors capable of providing over 5.5 megawatts (7,000 hp) of equivalent electrical energy. This paper describes the key aspects of the project and includes: Original project objectives; System design criteria; System description; Optimization studies; Major design features; Equipment description; and System commissioning.

Jan 1, 1993

By Bert C. Morrison

In 1961. American Smelting and Refining Company was conducting exploration for lead in southeastern Missouri using several geophysical methods. Electrical methods were used in almost every hole drilled during this period. These methods met with only limited success, with one exception. This paper deals with that exception: An Electrical Potential Method used at a single hole to indicate direction to better mineralization. This method was notably successful in the program.

Jan 1, 1970

By Quispe Mamani, Mayra Casas Azañero

The research is located within Asuncion and Cospan districts, which according to their geological features in contrast with previous studies pointing out Au, Mo and Pb anomalies create an environment of prospective interest. The objective is to use ASTER Satellite Images to identify ore-bearing hydrothermal alteration zones. To do this, processing techniques such as the combination of bands by RGB 943 and 461, band ratio 4/6, 4/5, 5/8 and 2/1 to identify advanced argillic, argillic to phyllic and propylitic alterations. In addition, indices defined by Ninomiya were used as a third technique in order to reinforce the data obtained from the previous techniques. The results in the study area are confirmed by the SAM spectral mapping technique using spectral signatures from the USGS library. Identifying kaolinite, alunite and pyrophyllite, assemblages of the advanced argillic alteration. Concluding in 3 areas of interest with the band ratios, 5 areas with the Ninomiya indexes and 9 areas validated with SAM, which were contrasted in 13 areas of prospective interest with well-marked argillic alteration.

Feb 1, 2025

By James R. Fahy, Lawrence A. Hansen, J. David Deatherage

A laboratory testing program was con- ducted to investigate the shear strength along specific soil-liner interfaces for five types of liners of varying thicknesses. Results indicated a bilinear relationship between shear stress and applied normal stresses ranging from 276 to 1000 pKa (40 to 145 psi). Friction angles along the soil- liner interface below the break point normal stress (7.5 to 19 degrees) were lower than those recorded above the break point normal stress (14.5 to 39 degrees ).

Jan 1, 1987