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By R. S. Olsen

The Bureau of Mines is engaged in research to recover aluminum from kaolinitic clay and other nonbauxitic domestic resources. As part of this work, calcined Georgia kaolin was prepared by a process that prevents slime formation and makes the leached residues fast settling and easy to filter. The leaching reaction for calcined kaolinitic clay in a 5 pct stoichiometric excess of boiling 23-to 26-pct HCI was found to be zero order. Rate constants based on the weight-fraction of aluminum in the clay were found to be between 0.095 and 0.15 min-1 depending on feed preparation and leaching parameters. The mathematical relationships between aluminum extraction and time for both batch and continuous, stirred-tank operations were derived and verified experimentally.

Jan 1, 1983

By D. H. De Jager

Fluorapatite is an important constituent of the greater part of the basic and ultra-basic rock members of the Complex. The evidence for and role of primary magmatic processes in the development of concentric zones of dunite, pyroxenite, syenite and carbonatite and its consequent bearing on the distribution of apatite are discussed. The presence of at least two generations of each of the latter three rock types indicates the cyclical nature of magmatic activity. Pegmatitic-metasomatic phases corresponding to the major magmatic cycles resulted in emplacement of pegmatoidal assemblages. The abundance of apatite in the pegmatoid can be traced to the composition of its parent magma and its cooling history. Approximately 2.5 million tonnes of phosphate concentrate are produced annually from ores containing from 10 percent to 25 percent apatite.

Jan 1, 1978

By Robert J. Evans

Reclamation costs were estimated for 20 coal surface mining operations in the Appalachian and Midwestern Coal Supply Districts (these two districts were divided into three multi-State regions). The cost data were obtained through onsite observations, interviews with mining company personnel, and the authors' cost estimating procedures. The cost data are presented in terms of dollars per acre, dollars per ton of coal produced, and dollars per cubic yard of overburden moved during backfilling. The reclamation process is divided-into three cost categories: Premining planning, backfilling, and revegetation. The average total reclamation costs for the three regions are $2.77 per ton of coal produced and $8,168 per acre. As the result of comparisons of reclamation costs by region, by mining method, by slope, and by size of operation, the most important reclamation cost difference is between area mining methods ($1.73 per ton) and contour mining methods ($3.81 per ton). The Federal Bureau of Mines conducted this study to determine as accurately as possible the actual costs involved with the reclamation of coal surface mined land done in conjunction with active mining operations.

Jan 1, 1975

By S. M. Cohen

Roll crushers had been used in the past ahead of existing milling systems in order to obtain additional production from such mills in both the mining and the cement industries. Historically, a roll crusher as a preliminator to a ball mill has been used for a number of industrial mineral applications. Flowsheets, from Taggars(1) show systems for fluorspar, graphite, lead and zinc to name a few, which are shown in Figures 1 to 4. These units applied, (in some cases still in service), prior to 1950 and as early as the 1920's, were of two general types, rigid rolls and spring rolls. The rigid rolls were phased out in favor of the spring rolls. The spring force related to the linear inch width of the rolls, ranged from 500 to 50,000 lbs/linear inch(1) on units up to 90" diameter. With choke feeding, the rolls were spread against the spring force during crushing keeping the system under high pressure to obtain high effectiveness.

Jan 1, 1986

By K. J. K. Weglo, M. U. Savich

"At the Falconbridge Limited, Canadian Nickel Division, Sudbury Operations, we investigated the ""NO NOISE"" ear muffs model NN3-F which is a Swedish product with foam-filled sealing rings (the Hellberg Standard Volume Hearing Protector). It is used extensively at Falconbridge mines in Sudbury.The research which was carried out in the four Falconbridge mines was conducted under three different headings: manufacturer's attenuation data (psychophysical method), clamping force and head size (bizygomatic diameter), and attenuation tests (physical methods) under working conditions.Manufacturers of hearing protectors claim their products offer noise reductions of 23 decibels (NRR) or more, but they fail to point out that this reduction is obtainable only under ideal conditions. The reality of attenuation under working conditions, as several studies have found, is quite different.Methods for using short measurements to determine the noise exposure index, and for controlling muff-wearing habits, were developed at the Elliot Lake Laboratory. Measurements taken at Falconbridge on ""NO NOISE"" ear muffs revealed that they have a practical attenuation of some IO to 13 decibels. It is important to note here that measurements also revealed that clamping force (thus attenuation) was in an inverse relationship with ear muff comfort. Measuring attenuation using noise dosimeters was a difficult job. Not a single surveyor would accept these measurements (physical method) for absolute accuracy. Apart from that, it was impossible to measure, in one shift, more than two work stations. Because of this, we sought a solution: measuring head size and clamping force in relation to actual attenuations.A detailed analysis of the relationship between attenuation and head size/clamping force was done at four mines. Standard deviation ellipses (standard error ellipses) for head size versus clamping force are in close agreement with measurements that were carried out. In order to measure clamping force an apparatus was constructed and a method for measuring suspension system durability is described in Appendices Band C of this report. At the same time we sought to reduce deterioration of ear muffs in mines as well as to put in place a system whereby attenuation can be controlled and improved. The clamping force apparatus can be operated automatically. The proposed control system is quick, simple and efficient . This system is equally applicable in small and large mining operations, and it can be totally automated and the data computerized for audit of the results. This control system is a new step in controlling ear muff attenuation in working environments.From these measurements of NN3-F ""NO NOISE"" muffs it can be concluded that ear muffs are not the total solution to protect the worker from noise.As the results were evaluated folio wing measurement, Falconbridge switched from the NN3-F ""NO NOISE"" muffs to approximately 90% Mark V ""NO NOISE"" muffs and 10% Mark V MSA muffs. These new muffs showed much better head size versus clamping force relationship and can be expected to produce 14 dBA or better attenuation of noise. RESUMEUne étude des casques antibruit ""NO NOISE"" modèle NN3-F, de fabrication suédoise, avec anneaux d'étanchéité en mousse (dispositif de protection contre le bruit ""Hellberg "" pour volume ordinaire)a été effectuée Ii la Falconbridge Ltd. , Division canadienne du nickel aux installations de Sudbury . Ces casques sont largement utilisés dans les mines de la Falconbridge Ii Sudbury.Cette étude aeu lieuen milieu de travail dans les quatre mines de la Falconbridge sous trois rubriques différentes soit: les données d'atténuation du bruit du fabricant (méthode psychophysique), la force de serrage et la taille de la tète (diamètre bizygomatique), et les essais d’atténuation de bruit (méthodes physiques). Les fabricants de dispositifs de protection contre le bruit prétendent que leurs produits offrent une réduction du bruit s'élevant Ii"

Jan 1, 1986

By Walshe J. M.

The slow-speed compressor is giving place to the high-speed type, with its greater economy of material and space; and, where very large units are required, the turbo-compressor is supplying the need. In the very large air-supply stations on the Rand, turbocompressor units of a capacity of 20,000 and even 50,000 cubic feet, requiring 4,000 to 13,000 horsepower, are quite a commercial proposition, and have proved a practical success. Air-compressors of this size are, however, very exceptional, and the high-speed reciprocating compressor is quite capable of dealing with the highest outputs so far required in this country and, in the hands of manufacturers experienced in the design of high-speed steam-engines, a very high standard of reliability and efficiency in operation is obtained. The so-called “high-speed” or more correctly quick-revolution type of compressor is now extensively used in mines and collieries; for the air-pressures required for power purposes in mining work, two-stage compression, with an intercooler between stages, is the design usually adopted in best practice. It is not the writer’s intention to describe a variety of high-speed air-compressors but to select as an example of this type of compressor the one with which he is most familiar, and which is probably more largely used than any other, namely, the double-acting two-cylinder two-crank type with automatic light-plate air-valves, and with the working parts lubricated on the forced-lubrication principle. Sectional drawings, efficiency curves, air-cylinder diagrams and other data accompany the descriptions and photographs of compressor design, components and mine applications

Dec 1, 1916

By Whitman E. Brown, Louis J. Erck

The installation in 1948 of a Hum-phrey~ spiral concentrator section at the Hill-Trumbull plant of The Cleve-land-Cliffs Iron Co. is the latest commercial method on the Mesabi Range being used for the recovery of fine iron ore. In two stages of concentration 84 spirals treat approximately 120 long tons per hour of minus ? in. ore. These spirals augment the production of the heavy-density plant which recovers the plus 36 in. iron from the plant crude ore. Structure of the ore is such that, when crushed, about 50 pct of the plant crude is minus ? in. size. After de-sliming in a 66 in. Akins classifier, grinding the classifier product in a ball mill and again desliming in a 78 in. Akins classifier about 15 pct of the crude ore remains to be treated in the spiral plant. Overall recovery of the ball mill feed in the Hill-Trumbull spiral plant during the 1948 season was about 53 pct of the weight and 66 pct of the total iron content. Of the actual feed delivered to the spirals from the 78 in. classifier 64.9 pct of the weight was recovered containing 73.7 pct of the total iron. The average analysis of the spiral concentrate is 55.05 pct Fe and 14.83 pct SiO2. An average of mill assays during the 1948 season is given in Table 1. The Hill-Trumbull plants treat both wash ore and jig-type ore. During the 1948 season spirals were used only on the fine sizes of jig-type ore. At times the deslimed minus ? in. size is of sufficient grade to warrant bypassing the spirals but in the main the fine size is delivered to the 48 first stage spirals and thence to the 36 cleaner or second stage spirals. In the past several years numerous Mesabi Range ores in the fine size cate- gory have been tested by a wide variety of beneficiating equipment. The prodigious amount of research devoted to the recovery of values in the fine ore reflects the dire need of the iron industry to squeeze the last possible unit of iron from the mined ore and to develop suitable equipment and processes to satisfactorily concentrate the leaner horizons as they are encountered in the process of mining. Large governmental and private appropriations have been allotted, new laboratories built, research and technical staffs increased, and operator-manufacturer cooperative agreements applied to hasten the solution of the problem. The University of Minnesota, at its Eighth Annual Mining Symposium in January 1947, dedicated as its objective the bringing to light of technological developments in iron ore beneficiation. Papers were given at that time relating to processes being developed. Specifically, these papers reviewed flotation, Baum jig, selective media concentrator, Hardinge concentrator, Dorrco sizer, heavy media concentration, Hydrotator, and the Humphreys spiral. The Cleveland-Cliffs Iron Co., after encouraging results from tests in a small pilot plant using one full size spiral, made the first commercial installation of Humphreys spirals on the Mesabi Range at their Hill-Trumbull mine, Taconite, Minn. This company

Jan 1, 1950

By Raymond A. Povirk, David L. Bartsch, James V. Hamel

The Ohio Valley Coal Company is expand- ing its Powhatan Mine No. 6 near Alledonia, Ohio. This expansion includes a 20 rn (65 ft) height in crease for an existing 44 rn (145 ft) coal refuse - slurry impoundment dam. The dam is being raised by upstream construction which will involve placement of more than 15 m (50 ft) of new fill over an existing reinforced concrete decant structure. This structure is 0.76 rn (30 in.) square inside and its deepest portion was under 24 m (80 ft) of coal slurry and water. The top of the decant structure was not strong enough to safely support the new fill and, because of the slurry and water, there was no way to reinforce the structure from the outside. The structure was reinforced frorn the inside by sliplining 73 m (240 ft) of 0.66 rn (26 in.) OD, 0.53 rn (21 in.) ID polyethylene pipe, grouting around this pipe with cellular concrete. and constructing a steel-fiber reinforced micro-silica concrete transition at the upslope end of the pipe. Rehabilition of the decant structure was completed in August 1989. The rehabilitated decant structure is now performing satisfactorily as fill is being placed over it for raising the dam.

Jan 1, 1991

In many base metal sulphide concentrators reagents such as collector and cyanide are often added to the grinding mill as well as to the flotation circuit. Whilst good reasons can be cited for splitting the reagent addition in this way, the benefits of such are rarely quantified and the complex reagent-mineral-media interactions occurring during milling are often poorly understood in terms of pulp chemistry. A new laboratory batch grinding mill designed by Magotteaux allows the user to measure, monitor, and control the pulp chemical conditions during grinding when testing different ores and media. Some of these parameters include pulp pH, pulp Eh, temperature, gaseous atmosphere, and dissolved oxygen concentration. In a recent development, the mill has been coupled with a simple on-line reagent monitoring system, designed by CSIRO, which allows the levels of species such as xanthate and cyanide in the grinding pulp to also be measured continuously during milling using a robust UV detection system. In this way the uptake of collector during grinding and the rate and ex-tent of cyanide interaction with the minerals and media can be determined as a function of grinding time. A series of grinding tests using an Australian nickel sulphide ore was conducted with the coupled system in which the cyanide dose, xanthate dose, and media type were systematically varied. The xanthate and cyanide levels were monitored as a function of grinding time and the data collected are discussed in terms of the pulp chemistry of the system and implications for plant reagent dosing strategies.

Jan 1, 2014

By George Delorme

"AbstractThe basic intention of this paper is to present, from a practical viewpoint, a thorough outline of all the sound and accepted principles connected with attaining satisfactory rope performance from multi-rope friction winders.In order to emphasize the importance of some aspects of rope maintenance, a limited amount of hoist rope theory has been included, a s it is felt that without this, some of the more critical, but nevertheless practical, aspects would perhaps pass without full appreciation of their individual merit.It is very much appreciated that many of the maintenance topics and practices discussed herein are already being observed with a high degree of skill among those already involved in modern friction winding. The hope is expressed, however, that the paper will be of additional assistance, and of particular help in introducing sound maintenance principles to those who are moving into this field of operation for the first time.Hoist RopesWITH a multi-rope friction winder system, structural upset within the hoist rope's cross section can occur if the ropes slip in the drum treads. This upset will usually appear at either end of the rope at the tangent point of the drum or deflection sheave with the respective conveyance in the normal uppermost position. This slipping action on the drum causes the outer cover of a Full Locked Coil or the strands of a stranded rope to shift, leading to structural upset. The result very often means that the ropes have to be withdrawn from service before completing their maximum service potential.The cause of any rope slipping in its tread can be associated with a discrepancy in tension of that rope between one side of the drum and the other."

Jan 1, 1977

By Iván Aguirre Palacios, Jean Guiroux Toro, Eduardo Valdés Guerra

Currently, mining operations seek to be competitive in the market. To achieve this, one of the relevant factors is to maintain and improve the productivity of the extractive processes, mainly the loading from the point of opening of the mineral bodies. To do this, many techniques suggest reducing production costs, with the first opening of your free-face up raises. However, there are different ways to carry out these open-face raises up opening processes, where the balance of costs and construction time must be well planned to meet production plans. Operationally, there are different techniques for its construction, the most common being Blind-Hole up Raises and those with drilling with current production equipment that operates mining operations. This study shows a methodology and the results of the implementation of access stack drilling with production drilling rigs for a maximum height of 15 m with electronic detonators in production blasting. Within the methodology used, Qa/Qc processes were considered in cargoes with explosives, instrumentation for monitoring (vibrations), VOD registration, among others. As a result, of a total of 12 raises up blasts, construction time was reduced by 45% and the cost of drilling and blasting (P&V) was reduced by 50%, for up raises with a maximum height of 15 meters. Regarding the efficiency of the heights, this was 97% compared to the planned drilling design.

Jan 26, 2026

[Early in 1936 the Interstate Oil Compact Commission and other groups interested in forecasts of demand .for petroleum requested the Bureau of Mines to make a physical inventory of crude-oil stocks in the United States. Accordingly, the 74th Congress appropriated funds for conducting such a survey during the fiscal year ended June 30, 1937. In the discussions and hearing2/ relative to the need for the sway, the opinion ms expressed that crude oil held in storage for long periods had lost so much of its gasoline content that he economic significant of total stocks should be discounted materially. Therefore, a primary objective of the survey was to]

Jan 1, 1938

By John B. Knaebel

Hammer machines are now widely used for underground sampling and exploration. Their application to such work can be divided into two classes - sampling and testing with ordinary drilling equipment to shallow depths of 22 feet or less, and "long hole" drilling with heavy machines and special equipment to depths of as much as 250 feet or more. In the first category hammer drills are employed for either of two distinct purposes: first, as a means of checking the results of grab or cut samples or, in certain types of ore deposits, as a substitute for these methods; and second, as a method of sampling the ground 5 to 20 feet beyond existing faces and thus aiding in the control of stoping operations or in the direction of development headings, as the case may be. The deep-hole drill, in the second category, has proved to be a valuable adjunct to the old established methods of exploring, end developing ore, provided it is employed under natural conditions to which it is suited, handled by men thoroughly familiar with the technique of its operations, and used with its possibilities and limitations clearly understood.

Jan 1, 1932

By J. H. Stears

Increasing use of Birmingham and other roof trusses prompted a Bureau of Mines study of support forces produced on a mine roof by these members. Equations, obtained from laboratory and field tests, are given for calculating the contact forces between the roof strata and a typical truss. Actual contact forces for a specific truss are difficult to estimate because of variable friction loss at the contact points. A finite-element analysis, using typical contact forces, indicated that trusses have a negligible effect on the stress field in massive, competent roof strata. The effectiveness of trusses in supporting broken rock strata was not analyzed. However, experience has shown that trusses are effective in supporting incompetent roof.

Jan 1, 1988

By Alok Tripathy

A simulation code called SIMJIG and the user interfaces have been developed using discrete element method (DEM) and the .NET platform respectively for the jigging process. DEM platform is used for tracking of particles in the jigging operation. DEM uses the net force balance on the particles to track the trajectory of the particle. Simulation results are compared with experimental results obtained by jigging of low grade iron ore lumps. Two different iron ore samples one from Chatishgarh and one from Odisha were used for the experimental studies. The Alljig? stratification test rig meant for batch laboratory experimental studies has been used in the present work. The behavior of different sizes of material on jigging has been examined. Later, the particle size behavior during jigging at different layers of the jig bed has been studied. Further stratification profile across the jig bed has also been studied. It was observed that simulation results are matching quite nicely with the experimental results. The SIMJIG simulator developed in the present study could be used for predicting the performance of the jigging operation effectively. Keywords: DEM, gravity concentration, jigging, iron ore, simulation

Sep 1, 2012

By K. Boakye, T. Newman, P. Bláha, M. B. Toelle

"This paper presents a quarry optimization plan using a block model and an in-house development quarry scheduling and optimization software (QSO Expert) to help improve quarry operations at Crystal River. The Crystal River Quarry is an underwater quarrying operation that barges limestone via the Gulf of Mexico, as the main source of raw material to a cement plant in Theodore, Alabama. To improve the quarry operation, an evaluation was completed to optimize the quarry planning and extraction procedures of the quarry. In order to achieve this, additional exploration drilling campaign was implemented, a new block model was re-calculated and the latest version of QSO Expert software was used. The primary economic impact is a higher recovery of limestone reserves; sustainability of resources, corresponding longer quarry life. Secondarily as the limestone is mined underwater and stockpiled above water, drainage reduces moisture content achieving direct cost reduction on limestone shipping. In addition, a considerable reduction in operational cost was achieved due to a significant decrease in consumption of electrical energy, reduced dragline maintenance costs and reduced dragline movements within the operation. INTRODUCTION Holcim is a Swiss-based global building materials and aggregates company. Founded in 1912, the company expanded into France and then throughout Europe and Middle East during the 1920s. In 1922, Holderbank, as the company was then known, expanded beyond the Swiss borders into France. By the end of the decade Holderbank held stakes in Belgium, Germany, the Netherlands, and Egypt (Holcim History 1912-2012) Positions in Lebanon and South Africa soon followed.. Holder bank later expanded in North America in the 1950’s. In the late 1970s and early 1980s, Holderbank continued its expansion in Latin America, Asia and Spain for the first time. The company expanded into Eastern Europe and experienced a boom in Spanish construction preceding the 1992 Summer Olympics. By 1986, Holderbank was the world's largest cement manufacturer. In the 1990s, the company consolidated its European holdings as the American market drove growth. Expansion into Eastern Europe and Russia continued (Holcim History 1912-2012). In 2001, the company changed its name from ""Holderbank Financière Glaris"" to Holcim (short for Holderbank ciment) (Holcim History 1912-2012). Holcim expanded by purchasing Aggregate Industries entering into the United Kingdom for the first time. That year, the company also expanded into India by acquiring a stakes in The Associated Cement Companies (ACC) and Ambuja Cement Eastern. In 2008, Holcim became the largest shareholder of China's Huaxin Cement with a 40% stake. In 2009, they acquired Cemex Australia. In 2014, Holcim and Lafarge announced they had agreed to terms on a ""merger of equals"" valued at nearly $50 billion in 2015. The new company LafargeHolcim based in Switzerland has a manufacturing capacity of 427 metric million tons a year."

Jan 1, 2017

By Longworth C. R

Competing requirements for land usage sometimes make the correct all- ocation difficult. The decision can be complicated by many factors such as local resident pressure, previous government decisions, economic pres- sures and the duration or permanency of the competing land usages. This problem often confronts the extractive industries with consequent delays in granting leases and some- times considerable local dissension. A proposal to extend the high grade silica sand quarry of the Wamberal Sand Company Pty. Limited is a microcosm of these competing requirements. The sand quarry is located on the New South Wales central coast. It is an open pit operation on a near beach deposit of silica sand suitable for flint glass manufacture.

Jan 1, 1976

By F. A. Forward

Introduction The main line of ascent in the development of the nickel industry may be traced back through the International Nickel Company of Canada, Limited, to its earliest antecedents, the Canadian Copper Company and the Orford Copper Company. Mining geology is but one aspect of the overall development of this organization, and the stress it has placed on geology grew according to the need. In the early days, intensive geology was not required because ore supply was not one of the main problems of this or any of the pioneer companies. The difficulty then was to find economic methods for reducing the ores to nickel and copper, and markets for absorbing nickel in the face of a limited demand from consumers heavily prejudiced in favour of the New Caledonia product. "Very early in the history of the region it was patent to everyone that to share in the full benefits of the industry the same individuals or company must control the whole of the operation necessary to manufacture the finished product' (1, p. 45). These conditions were fulfilled for the International Nickel Company in 1902 when the Canadian Copper Company (incorporated 1886), with its ample ore supply, took the initiative to merge its interests with those of the Orford Copper (Refining) Company (incorporated 1887) to form the new company which, with reorganizational changes, emerged as the producer of the overwhelming bulk of the world's nickel. The Mond Nickel Company, Limited, entered the field in 1899 with a refining process, and over a period of years acquired ore through purchase of mining properties. This Company operated successfully and independently until 1929 when its assets were joined with those of the International Nickel Company in order to permit the most economic exploitation of the Frood-Stobie orebody in which both Companies were interested.

Jan 1, 1948

By Charles A. Kliche

INTRODUCTION The Northern Great Plains Coal Province which occupies approximately 36.6 ha contains about one-half of the nation's total coal resources. About one million ha are underlain by coal that is considered to be mineable from the surface. The topography of the province is predominately plains, rolling hills, and some badland areas characterized by breaks or sharply eroded hills. Elevations range from about 1500 m above sea level on the west to about 600 m above sea level on the eastern boundary. The average slope of the ground is approximately 2 m per km. Streams in the province drain generally easterly and southeasterly (1). In the United States, the Northern Great Plains Province lies within the states of North Dakota, South Dakota, Montana, Wyoming, Nebraska, and Colorado. The coal within the province is located almost entirely in the states of North Dakota, Montana, and Wyoming. Although it is relatively low rank, the coal within the province encompasses a large portion of the total remaining U. S. reserves. The U. S. Geological Survey estimates the total remaining coal resources of the United States to be 2.6 trillion mt within 1000 m of the surface, and 2.9 trillion tons within 1830 m of the surface. Of this total, only about 177 billion mt are classified as reserves meaning that they are (1) known in location, quantity and quality from geologic evidence supported by engineering measurements, and (2) economically recoverable based on currently available technologies and current market value (2).

Jan 1, 1983

By Xiaochun Xiao, Xin Ding, Yishan Pan, DI WU, Xiangfeng Lv

Rockburst is a sudden disastrous instability of coal mass that poses a serious threat to underground exploitation of coal resources; therefore, approaches of prediction and control methods are valuable for improving mining environments. The mechanical properties and bursting liability of coal with drying, under-saturated, and saturated moisture content under uniaxial compression are investigated, and the charge induction signal during coal deformation both in the laboratory and on-site is recorded in this study. The presence of water reduces the cohesion and increases the internal stress caused by non-uniform deformation of minerals, resulting in the strength, elastic modulus, and bursting liability being weakened. The charge induction precursor main frequency band is 1–100 Hz and belongs to the very-low-frequency signal regime, and it indeed varies with the loading stage, leading to specimen failure owing to changes in amplitude and continuity of the charge pulse in both the time and frequency domains. Water inhibits the richness of charge induction and reduces the bursting liability, and the earlier the precursor appears, the more total charge emerges. Moreover, measurement results indicate that the amplitude and continuity of the charge pulse decrease over a longer time, as recorded in a coal seam with water injection, further verifying the weakening of the coal dynamic characteristics. Charge induction can be a valuable tool with which to obtain the precursors for rockburst and to aid the evaluation of water injection.

Dec 26, 2022