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By Yu. A. Polozov, V. A. Lagunov, O. Yu. Lushinkova, Yu. I. Svirskiy, Eh. Ya. Kipko, Roy A. Williams

4.1 THE GENERAL COMPOSITION AND PROPERTIES OF CLAY-BASED GROUTS Clay-based grouts are visco-plastic systems; they are made by adding structure-forming reagents to a clay mineral mortar. Small amounts of cement and various chemical ad¬ditives constitute the reagents. If necessary, fillers also are added. The distinguishing feature of clay-based grouts is that throughout their entire stabilization period they do not form a crystallized structure as does cement grout. The structure of stabilized clay-based grouts does not deteriorate during minor rock movement or upon the initiation of blast¬ing during the construction of a shaft or a drift. Because they can possess good rheological properties during the ini¬tial structure-forming period relative to cement grouts, clay¬based grouts are not easily eroded from large fractures and karstic cavities by flowing ground water. In addition, their finely dispersed clay particles facilitate a greater fracture penetration capacity, especially in dual porosity rocks. Numerous investigations of the structural-mechanical and rheological properties of clay-based grouts by STG have demonstrated that the most effective grouts for pre¬venting the inflow of ground water into underground work¬ings are grouts that have a cement content of 8 to 10% (90 to 120 kg/m3) of the clay grout by mass. The grout should have a density of 1.18 to 1.30 T/m3. Various additional substances and chemicals can be added as additional fillers and structure-forming reagents. In pure ground water at temperatures above freezing, sodium silicate in the amount of 0.8 to 1 % by mass normally is the only structure-forming reagent that is necessary if the proper clay is selected and if it is available. The production process for making clay-based grout is divided into two stages: 1) the production of an initial clay mortar with specified properties and 2) the production of a clay-cement additive grout mixture using the initial grout along with the structure-forming reagents, including the ce¬ment. The properties of clay-based grouts depend on the phys¬ical-mechanical properties of the initial clay mineral, the properties of the cement and the properties of the chemical reagents that are added. 4.1.1 TECHNOLOGICAL PROPERTIES OF CLAY-BASED GROUTS The dynamic shear stress' To, the viscosity 11, the static shear stress2 0, the maximum shear stress of the structured that the rheological and structural-mechanical prop¬erties of clay-based grouts must fall within the following limits: the dynamic shear stress To = 50 to 200 Pa; the viscosity -9 = 0.02 to 0.07 Pa sec; the static shear stress 0 = 150 to 600 Pa; the plasticity strength Pm of the structure one minute after preparation (according to P.A. Rebinder's method) equals 150 to 500 Pa. The plasticity strength 10 days after preparation is ? 0.15 MPa. The general relationship of the change in the structural strength of clay-based grouts relative to stabilization time is shown in Fig. 32. The figure shows that the structure-form¬ing process for clay-based grouts is characterized by three stages. These stages correspond to the time periods required for conducting the principal operations during the injection of the grout into a fractured aquifer as described below. Stage I, corresponding to the time period T1, reflects the small development of structural strength during early stabi¬lization. During this time, the structural strength must not preclude the capability to pump the grout. The time Tl must correspond to the length of pumping time from the moment water is shut off and mixing occurs until the pump stops forcing the grout through the manifold block and pipeline into the fractured rock as described subsequently herein. Stage II, corresponding to the time interval T2, reflects a sharp but controllable increase in the structural strength of the grout. The length of time period T2 is controlled by the addition of appropriate reagents. Stage III produces the final value of the structural strength. This final strength is used to design the dimensions of the isolation curtain. Consequently, the development of grouts is guided by two principal criteria: 1) the grout must develop the highest possible structural-mechanical properties and 2) it must be able to be pumped by a piston pump prior to final stabili¬zation. Successful grouting depends to a large extent on the correct design of a grout for each specific case. It is impor-

Jan 1, 1993

By Sureshan K. Moothedath

This paper provides a mechanistic representation for floc formation, growth and degradation and presents results from an experimental study of batch flocculation in which step changes were made in the impeller speed, flocculant addition, and slurry concentration. A discussion of the experimental results is included in terms of the mechanisms of floc formation and size-change.

Jan 1, 1993

By S. O. Moshier, L. S. Barron, J. C. Hower

The Hardgrove grindability test, commonly used in coal characterization, was conducted on 13 Mississippian carbonates from Kentucky, Tennessee and Illinois. The results demonstrated that the grindability increases with a decrease in the Si02/(MgCO3+CaCO3) ratio, with fine-grained and petrographically-complex stones having lower grindabilities. Also, the relationship between the Bond work index and Hardgrove grindability is significant.

Jan 1, 1993

By R. J. Wesely

It is obvious from recent events in The Peoples Republic of China that a major effort is underway to increase trade with the Western World. The production of Gold contributes to China's ability to participate in international trade and consequently they place a high priority on increasing gold production. Many of the operating gold mines in China contain refractory ores which to date have not been efficiently treated. Figure 1 illustrates the description and location of some of the major gold mines in China. Recognizing that the technology necessary for the economic treatment of this ore has been developed in the United States and other Western Countries, China has begun to seek assistance in evaluating several potential projects. This paper will examine the recent history and current trends in developing a refractory gold treatment project in China.

Jan 1, 1993

By Justus B. Deen, Randy Peterson

INTRODUCTION The General Chemical Soda Ash Operation located near Green River, Wyoming produces about 4.5 Mt of trona per year. In July 1989, Mine Ventilation Services Inc. performed a ventilation survey of this complex trona mine which had thirteen active panels spread over 36 square kilometers. The ventilation survey and subsequent study showed that the intake shaft air velocities were at their practical limits (Wallace and Rogers, 1987). The need for additional intake capacity was immediate. The ventilation network modeling delineated the best location for this new intake shaft as it applied to the 5 year ventilation plan. Unfortunately, this location, 6.5 kilometers from the soda ash processing plant, would make heating this intake air very costly. Presently, the intake air is heated by heat exchangers which use waste heat from the plant. Air heating during the winter months is necessary for miner comfort and to prevent potential freezing of water lines in the mine. It was decided to examine the feasibility of heating the air geothermally by coursing it through an old production panel. This method of air heating has been used in this region with good results at the Stauffer Chemical Operation (now Rhone-Poulenc) (Moore, 1985). In 1990, a geothermal heating study examined four different production shaft/panel configurations and a workable design was found. The operators at the General Chemical Soda Ash Operations acted on this design and began raise boring a ventilation shaft in the Spring of 1991. This paper describes the ventilation system, briefly, and the geothermal heating studies performed. Findings of the 1990 geothermal studies are then compared to field data acquired in the Winter of 1992. THE VENTILATION SYSTEM The ventilation system at General Chemical had four shafts serving the mining horizon in July 1989; three of these shafts are located at the Northwest end of the mine. The active work areas had progressed to the South over the past years and supplying ventilation has become increasingly difficult. The 6.1 meter diameter #3 Production shaft and the men and materials compartment of the 6.1 meter diameter #2 Split Shaft had reached their air velocity limits. Conversely, the 4.6 meter diameter #5 Exhaust Shaft was under utilized. Ventilation studies showed the conversion of the 3.7 meter diameter #1 Exhaust Shaft to an intake would provide adequate intake capacity for two years. The next option to improve ventilation was the addition of an intake shaft at the southeast part of the mine at the intersection of H Mains South(H-M-S)and J Mains East(J-M-E) (See Figure 1). A service shaft has been planned for the extreme Southeast end in the late 1990's. Ventilation network analyses showed this interim intake shaft would have to be at least 2.5 meters in diameter to postpone the service shaft construction beyond 1995. The greater the size of the borehole, the further the construction could be postponed. In October 1991, General Chemical commissioned the 4.57 meter diameter #4 Ventilation Shaft near the junction of H-M-S and J-M-E as shown in Figure 1. The L95 panel would be used for air heating as described in the geothermal heating section to follow. GEOTHERMAL STUDIES Geothermal heating studies were performed by MVS Inc. in May 1990. Using a modified code of CLIMSIM, an underground mine climatic simulation model, several different shaft/panel configurations were examined to see which would provide adequate air heating during the winter months. CLIMSIM simulates heat flow into a single underground airway. The program was used to evaluate the heat flow to and from the airway surface and to calculate the resulting change in dry bulb temperature of the ventilating air. CLIMSIM uses inlet air conditions, airway characteristics, and rock thermal properties input by the user to predict the variation of psychrometric and thermodynamic parameters along an underground airway.

Jan 1, 1993

By P. R. Taylor

A cyclone reactor system for the partial reduction and melting of taconite concentrate fines has been engineered, designed and operated. A non-transferred arc plasma torch was employed as a heat source. Taconite fines, carbon monoxide, and carbon dioxide were fed axially into the reactor, while the plasma gas was introduced tangentially into the cyclone. The average reactor temperature was maintained at above 1673 K (1400 C), and reduction experiments were performed under various conditions. The influence of the following parameters on the reduction of taconite was investigated: carbon monoxide to carbon dioxide inlet feed ratio, carbon monoxide inlet partial pressure, and average reactor temperature. The interactions of the graphite lining with carbon dioxide and taconite were also studied.

Jan 1, 1993

By D. T. Iseley, David Bennett, Christopher Norris

The microtunneling test program is one of three main elements of the research project, "Trenchless Construction: Evaluation of Methods and Materials to Install and Rehabilitate Underground Utilities." The other elements of this project include an evaluation and demonstration of horizontal directional drilling technology and pipeline rehabilitation systems. The research is a Corps and Industry cost-shared project funded under the Construction Productivity Advancement Research (CPAR) program. The laboratory partner is the U.S. Army Engineer Waterways Experiment Station (WES), Geotechnical Laboratory. The industry partner is the Louisiana Tech University's Trenchless Technology Center. Industry participants are contributing over half the total cost of this research. The overall objective of the CPAR program is to improve productivity in the U.S. construction industry, thereby enhancing the competitiveness of the U.S. industry in domestic and overseas markets. The Corps and other federal and state agencies will benefit by realizing reduced costs, enhanced safety and better products and services as the products of this research program are developed, tested, and pushed into the market place. The microtunneling demonstrations and evaluations were performed during September and October 1992 at a specially constructed test facility built at WES in Vicksburg, MS. The test facility is 104 m (340-ft) long, 5 m (16-ft) wide, and 4 m (13-ft) deep. It was constructed, ironically, by first excavating a trench into which 6 different types of soils were placed and compacted in approximately 18.3 m (60-ft) long sections. The soil profiles include a lean silty clay (loess), a dry sand, highly plastic buckshot clay, wet sand, clay gravel and silt. The interfaces between soil profiles were sloped to simulate mixed face conditions as the machines exit one zone and enter another, and provided challenges to ground control and alignment and grade control during these transitions. Moisture and density tests were performed on all materials in each lift to assure uniformity. Horizontal inclinometers and 3 levels of settlement plates were installed at key locations in the test bed. The settlement plates and rods and the horizontal inclinometers, together with surface survey points, provided data to evaluate settlement and heave along the test section. Penetration resistance was measured in each section of the completed test bed. Strain gages were installed in 8 of the 0.6 m (24 in.) diam. Hobas pipe sections to measure strains in the pipe as it was being jacked into place. Steering jack loads, jacking thrust loads, and cutterhead torque were also measured during the drives. The results of these tests will be used together with other information to develop guidelines for conducting feasibility studies and selecting proper methods compatible with anticipated conditions.

Jan 1, 1993

By R. D. Beard

Puerto Rico lies within the remnants of a deformed Cretaceous island arc system in the northeastern Caribbean. The Island can be divided into three broad geologic provinces: the Central Volcanic-Plutonic Province (Lower Cretaceous to middle Eocene), and the Northern and Southern Limestone Provinces (early Oligocene to middle Miocene). Known precious metal deposits are generally small and occur in veins and shear zones within Lower and Upper Cretaceous volcanic and plutonic rocks. Some Tertiary igneous rocks are also mineralized. Selected indications of disseminated lithology-controlled mineralization could represent larger deposits. Associated metals in some deposits include copper, zinc, and lead. At present, tax policies, population density, political outlook, and lack of proven significant precious metal deposits discourage the establishment of a metal mining industry.

Jan 1, 1993

By Shuyu Qin, Shujiang Sun, Jingfu Zhao

The three key parameters of mine fires are local airflow velocity, temperature and oxygen concentration. According to the theories of seepage in porous media, heat transfer and heat dispersion, mathematical models were constructed based on the three parameters. The models can be used for early prediction of mine fires and for estimation of the level of spontaneous combustion. Proper use of the models can assist in preventing and controlling mine fires. KEY WORDS: airflow velocity, temperature, oxygen concentration, numerical modelling, mine fire prediction.

Jan 1, 1993

By Frank H. Blair

A study of paleogeography and paleo-environment, coupled with modern geochemical techniques and geologic inference, points to the presence of unconventional platinum group metal deposits in domestic and foreign ultrabasic terranes. During the laterisation of the tectonized and serpentinized mafic and ultramafic rock units, onshore winds provided abundant low temperature chloride to the laterite-saprolite profile. Here, an environment formed where gold, silver and platinum was dissolved, transported and redeposited. Changes in climatic conditions have helped preserve the redeposited metals in fossil laterites. The definition of "unconventional mineral resources" used here is taken from the Cameron Volume of Unconventional Mineral Deposits published by SME-AIME in 1983: "Unconventional mineral resources represent materials of possible economic importance that occur in geological or physical environments that have not been successfully exploited for the particular mineral." (van Rensburg, 1983). Chromite-rich rocks worldwide contain high platinum group metal concentrations. This feature is found in ophiolitic sequences, Alaskan-type ultrabasic complexes or statiform intrusions. Association of platinum group metals with chromite has received much attention. The reason for that associa¬tion, however, is not clear. Much has been written about how and where the platinum group metals occur. It is known that they are present in the spinel lattice, as solid solution elements in sulfides and as discrete platinum group minerals. This article outlines the reasons geologists should be looking at lateritic terranes to determine the feasibility of searching for undiscovered, low-grade platinum group metals amenable to openpit, bulk mining. Laterite-saprolite horizons could contain significant platinum group metals and location of anomalous values on the surface and in the weathered profile can lead to discovery.

Jan 1, 1993

By Frédéric Flament, Daniel Hodouin, Claude Bazin

A control strategy is proposed to meet the following specifications of flotation control: minimize the variations of concentrate and tails grades and recovery while limiting the amplitude of variations of the manipulated variables. The strategy consists of determining future control actions which optimize a performance criterion over a limited time horizon. The desired dynamic behaviour of the controlled flotation plant is specified using reference models. The strategy is tested on a 2-computer plant simulator working in an environment which emulates the industrial conditions.

Jan 1, 1993

By Richard R. Klimpel

During the last 28 years, I have had the very challenging and rewarding experience of working as an engineering professional in a large multinational company, both as a manager of engineers and engineering projects as well as an inventor and generator of new engineering processes and products. Due to the diversified geographic and tech¬nical nature of my employer's business, my responsibilities have taken me all over the world. This has included interactions with people in different industries including minerals, coal, chemicals, petroleum, pulp and paper, agriculture and pharmaceuticals. As diverse as my experience may seem, it has always amazed me how common the basic underlying technology and economic trends are that shape the working environment that any given engineer in any given geographic loca¬tion will experience. I would like to discuss the industrial evolution from micro to macro engineering. One of the basic truths behind how industry must and will operate is "change," including: • the creation of conditions for change, • the anticipation of change, • the resistance to change, • the rewards that being part of a change can bring and • the destruction that change can bring to the unprepared. This fact was well stated by Heractitus around 500 BC.: "There is nothing permanent except change." This simple truth has been valid since the dawn of time and, if anything, is accelerating in nature every decade.

Jan 1, 1993

By G. Ferrara

During several years of operation in Europe, South Africa and other countries, the Tri-Flo has demonstrated to represent a substantial improvement of the dense medium dynamic separation systems. The reasons are: (1) high sharpness separation due to the multistage system and the application of new concepts in designing the regeneration circuit and controlling the medium rheology; (2) the possibility of performing two cuts at different densities using a since separation device and a single regeneration circuit. The paper discusses in detail the above mentioned points, with particular reference to the multistage technology, based on the circuit analysis theory, and to the control of the medium rheology based on recent work in the modelling, and simulation of the rheological behavior of dense suspensions.

Jan 1, 1993

By Michael Gay

Right in the heart of Boston Harbor lies Deer Island, where a ten-year, 6 billion dollar sewage treatment plant is under construction. The 9.5 mile long, 25.5' diameter Effluent Outfall Tunnel is the center piece of this program. A Robbins double-shielded TBM is currently driving this challenging tunnel some 400 feet below sea level. This paper will discuss the set-up and operation of this Tunnel Boring Machine in driving the longest single heading tunnel ever built in North America.

Jan 1, 1993

By Mike Horn, Keith Meade, Marvin L. Smallwood

Technological changes in programmable logic controllers (PLC)'s and the need to improve the architecture of Mine Wide Monitoring Systems (MWMS) has resulted in the design of a PLC based system at the Virginia Division of Island Creek Coal Company. The system which is presently in the installation phase, is a joint effort of Island Creek Coal Company, Westinghouse Electric Supply Company and Mining Controls Incorporated. The system uses an ethernet based network for graphic display of system data operating under the Genesis software package. Telemetry for the system utilizes the Seimens/Westinghouse L1 network operating over two twisted pairs. Remote telemetry uses fiber optic links and modems operating over standard telephone lines. 500 and 2000 series PLC's provide distributed data processing for the system with hierarchial processing operating under the Genesis software on the ethernet network for individual mine site monitoring along with the remotely located division office monitoring. System control and data acquisition is provided for underground MWMS operations and on the surface for a vast methane gathering system that is used for degasification of the mines and collection of pure methane for sale to the Columbia Gas Company as natural gas. The inability of industrial MWMS companies to keep up with the vast changes in technology, along with economic considerations associated with expanding the existing MWMS created the need for the development of the PLC based system to replace the older industrial monitoring systems.

Jan 1, 1993

By D. S. Ramey

In-situ leaching of the oxidized copper mineral resource at the San Manuel mine has proven to be a technically and economically viable method of copper extraction. Although this leaching method has been modeled to predict future production capabilities, the expected magnitude of the ultimate recovery from any portion of the present mine is not fully understood. A closely controlled test has been designed, constructed, and is now operating to determine the rate and magnitude of copper recovery. The test, initiated in June 1992, is scheduled to operate for approximately 18 months. This paper presents an overview of the test design and current results.

Jan 1, 1993

By R. J. Piniazkiewicz

Talc orebodies are mined in Asia, Australia, Europe, North America, and South America. Operators in North America must be efficient quality suppliers to thrive in a talc market in which many overseas suppliers have advantages such as lower hourly wages, shorter distances to ports, and less government regulation and intervention. Continuous improvement through teamwork and innovation is needed in the following areas to thrive amidst worldwide competition: 1) Maximization of the in-place value of ore. 2) Research and development to yield new processes and products. 3) Safe productivity. 4) Involvement in legislative processes. 5) Wellness programs to lower health care costs.

Jan 1, 1993

By R. E. Nivens

In the past, Newmont Gold Company relied on cement for their ore agglomeration process. With assistance from Betz Industrial, Newmont began Investigating the use of polymers for ore agglomeration. If gold recovery would not be jeopardized, then polymers could replace cement and possibly reduce operational costs associated with cement agglomeration. The following outlines the preliminary testing conducted to determine the feasibility of polymer agglomeration with Newmont's ore and the results of the test heap, which was constructed so the program could be examined under actual operating conditions. Similar polymer agglomeration testing has been successfully performed in other Nevada gold operations. By eliminating the need for cement, a polymeric agglomeration program could improve material handling operations, as well as offer the following additional savings. First, the polymer application uses only lime for adjusting basicity, the polymer does not contribute any alkalinity to the heap. Because lime is more soluble than cement, detoxification of the heap becomes much faster and less costly for the mine relative to rinsing cement alkalinity. The following graph compares the detoxification rate of cement and polymer over a 33 day cycle.

Jan 1, 1993

By W. C. Hirt

Selective flocculation was used to produce superclean zinc concentrate with minimized silica contamination. Research was carried out on a flotation concentrate from the Jersey Miniere Zinc Company (JMZ) in Gordonsville, Tennessee. The material was first dispersed with sodium silicate and then causticized tapioca starch was used to selectively flocculate the sphalerite, leaving the silica in suspension. This technique has been applied commercially to iron ore beneficiation but has never been used for processing zinc. The feed material assayed 0.45% Si02. Use of 0.56 kg/tonne (1.13 lb/st) of sodium silicate and 0.070 kg/tonne (0.141 lb/st) of causticized tapioca starch resulted in 98.2% zinc recovery in a purified zinc concentrate assaying 66.0% Zn and 0.24% silica. The present target level for silica contamination in JMZ zinc concentrates is 0.3% Si02. This work has shown that selective flocculation offers a potential method for cleaning flotation concentrates, particularly where low silica products are required.

Jan 1, 1993

By B. Devulapalli

A mathematical model of the industrial hydrocyclone based on fluid dynamics is a better alternative to the currently existing empirical models. The swirling-flow velocities are determined by solving the Navier-Stokes equations with an appropriate turbulence model. The solution of the momentum-balance equations yields the flow field inside the hydrocyclone which determines the particle trajectories, and subsequently the classification curve. The essence of the model is that the physical dimensions of the hydrocyclone and the slurry characteristics can be incorporated, and the influence of these parameters reflects on the flow predictions. The predicted tangential and axial velocities in a 250-mm hydrocyclone are in good agreement with the laser-Doppler velocimetry measurements. Finally, the predicted classification curves show good agreement with experimental data measured on a KREBS Dl0B hydrocyclone.

Jan 1, 1993