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By G. Heiken

On the Earth's Moon, obvious hazards to humans and machines are created by extreme temperature fluctuations, low gravity, and the virtual absence of any atmosphere. The most important other environmental factor is ionizing radiation. Less obvious environmental hazards that must be considered before establishing a manned presence on the lunar surface are the hazards from micrometeoroid bombardment, the nuisance of electro-statically-charged lunar dust, and an alien visual environment without familiar clues. Before man can establish lunar bases and lunar mining operations, and continue the exploration of that planet, we must develop a means of mitigating these hazards.

Jan 1, 1991

"The dust/lung research of the Center has several long-range objectives:* better methods for the early diagnosis of coal workers' pneumoconiosis (CWP);* methods to modify the disease process;* tests to identify toxic products; and* tests to identify individuals with heightened susceptibility to pneumoconiosis.A major immediate objective is to define the mechanism of dust-induced lung disease. This means determining:* dust characteristics that are important in causing lung diseases;* important interactions between dust and lungs; and* earliest detectable stages of the disease.Several of the Center's projects involve exposing lung cells in culture (in vitro) or animal lungs (in vivo) to samples of the suite of characterized mineral dusts described earlier. The responses of the lung cells or tissues to the dusts are being studied in order to better understand how inhaled dusts cause lung disease.One project is studying the effect of dust exposure on the production of mucus by rat tracheal explants in vitro. Mucus is a major factor in clearing inorganic dusts from the lung. Results thus far have shown that exposure of tracheal cultures to coal dust caused a decrease in micin production in comparison to parallel cultures without dust. To examine the effect of in vivo coal dust exposure, rats were maintained in an inhalation chamber for two weeks, and control rats were in an identical, but dust-free chamber. Tracheal explants results indicate that the effect of in vivo dust exposure is similar to that noted in the in vitro experiments.Pulmonary alveolar macrophages (PAMs) are a key component of the lung's response to inhaled particulates, and they play several important roles in pulmonary inflammatory and repair processes. PAMs are the cells that actually ingest dust particles. Other studies have shown that they play a critical role in the development of silicosis and asbestosis. The Center is studying the effect of dust exposure on the release of oxygen free radicals (superoxide) by PAMs. Intercellular production of superoxide occurs when PAMs phagocytize particles, such as inhaled bacteria, and is an essential mechanism by which PAMs kill ingested, bacteria. A number of complex physiological events occur during this process which are not clearly understood. It is thought that PAMs containing indigestible materials, such as mineral dusts, overproduce superoxide, or inappropriately release it into the surrounding tissues. If true, this would cause toxicity to surrounding lung cells by peroxidation of the lipids in the cell membranes. In vitro exposure of PAMs to low or high doses of kaolin is inert. Preliminary studies indicate that coating the quartz particles with a surfactant reduces toxicity."

Nov 1, 1988

By Geo. T. Lynch

PALEOLITHIC MAN, laboriously shaping a stone implement in his cave, discovered that the dust irritated his eyes and nostrils and hindered his labors, whereupon, muttering a few incantations, forerunners of modern profanity, he removed himself and his work outside. There, ignoring the jeers of the hairy ?old-timers,? he turned his back to the wind and resumed operations in comparative comfort. Thus originated the dust problem in the mineral industries, and its solution. Despite long familiarity with the annoyance, danger, and loss occasioned by dust, little progress was made in the engineering solution of its problems until recent years. Some advance can now be reported but too many traces of ancient tradition and practice still remain. Considerable published information is available but only a part of this is of proved accuracy and utility. The greater portion is either misleading, being derived from too few cases to be of general application, or entirely erroneous, originating in guesswork, legend, or individual inspiration, divine or otherwise. The engineer, confronted with a dust problem, has neither the time nor the special training required to extract the values from this mass of low-grade. It is, therefore, desirable that we attempt to correlate the known values and to put them into a form upon which actual progress can be based. This discussion is, then, for the benefit of that engineer, particularly the engineer in the mineral industries and more particularly in ore-dressing plants, and is merely a gathering of facts already known but difficult to segregate.

Jan 1, 1938

By Cody Giroux, Homer Scurlock, Michel Wasag

Silica and Crystalline Quartz exposure continues to be a serious health threat to nearly 2 million workers in the United States, including more than 100,000 working in high risk jobs such as abrasive blasting, foundry work, stonecutting, rock drilling, quarry work, mining and tunneling. The primary focus of this study is to identify the best methodology to reduce particulate-laden air and limit/eliminate exposure to respirable dust with silica/crystalline quartz during tunneling operations. This study focuses on two de-dusting systems employed on similar tunnel construction projects. The first project is the Coxwell Bypass Tunnel located in Toronto, Ontario Canada. The second project is the Westerly Storage Tunnel located in Cleveland, Ohio. The Toronto project is utilizing a wet de-dusting system. The Cleveland project is using a dry de-dusting system. The objective is to determine which system provides the best protection and suitability to capture, remove and ultimately reduce respirable concentrations of silica/ crystalline quartz to safety and healthy levels in underground tunneling activities.

Jun 13, 2021

"As stated earlier the primary goal of the Generic Mineral Technology Center for Respirable Dust is to reduce the incidence and severity of respirable dust disease through advancing the fundamental understanding of all aspects of respirable dust associated with mining and milling and the interaction of dust and lungs. While initial work was directed to coal dust the charge to the dust center has been expanded to include diesel particulates and asbestosis, the latter of deep concern not just to workers in the mineral sector of the economy but also to the general populace.A major facet of Dust Center research has been the analysis and documentation of comprehensive research protocol and procedures that are appropriate state-of-the-art in the various areas of respirable dust. In addition to definition of standardized research protocols and procedures which would be utilized by center personnel for uniformity and reproducability there is a considerable need for utilizing standardized respirable dusts in experiments with consistent, reproducible characteristics which simulate those of actual mine dust. This respirable dust needs to be available in large quantities for a wide variety of research uses that include animal and medical experiments. The dust must be free of the lubricating oils and grinding wheel contaminants that are frequently encountered in laboratory generated dusts.The holistic approach to establishing standardized protocols and procedures applicable to the five major research areas of the center is presented in Figure 5.In one hypothesis, range in coal volatility is considered to be a major causal factor in the incidence and severity of pneumoconiosis. Therefore a suite of characterized standard respirable dust samples have been prepared for researchers from coals representing the western (high volitile A bituminous), central (medium volatile bituminous) and eastern (anthracite) mining areas of Pennsylvania. Quartz, limestone (rockdust) and kaolin clay samples, representing important mineral constituents of coal dust have also been prepared.A suite of medical investigations have been developed utilizing small and medium size animals as well as non-human primates in a variety of dust/lung interaction projects which will be discussed in the next section. A number of respirable dust sampling and dust generation methods have been investigated and selected techniques utilized for both in-mine and in-laboratory research investigations. These will also be discussed in more detail later. A wide range of respirable dust size, chemical and mineralogical analyses have been investigated, standardized and documented for use in various research investigations.This interaction and documentation of various respirable dust sample procedures, animal and medical tests, sampling and dust generation methods, plus size, chemical and minerological analysis applied in the five major areas of research investigation have served to create a very favorable synergism and rapid technology transfer in the respirable dust center."

Jan 1, 1988

By Mike Cammack, Logan Huppert, Gustavo Azpilcueta

During the summer of 2015, Unisea Inc. sought proposals for the G1 Dock Replacement Project in Dutch Harbor, Alaska. It would be a one year project and construction was scheduled to begin in the spring of 2016. One aspect of the project was the requirement for a layer of armor stone to protect part of the dock. An estimated 30,500 tonnes (37,670 t) of armor stone were needed for the project. The source of rock was the Unisea Quarry due to its proximity to the project and the quality of the stone meeting all the required technical standards.

Jan 1, 2018

By AIME AIME

IN an address before the New York Section. A.I.M.E., Oct. 20, Alex L. ter Braake, speaking on the tin industry of the Netherlands East Indies, interjected a few remarks, at the chairman's request. on the mineral stock-piling project now before Congress in a bill sponsored by Senator Scrugham. The full text of Mr. ter Braake's paper was published in the Nov. 6 issue of the American Metal Market. Following mention of the buffer stock scheme as applied in the tin industry, Mr. ter Braake continued:

Jan 1, 1943

Duval Corporation, the owners of the Sierrita, Esperanza, and Mineral Park copper operations in Arizona, first acquired the mineral rights to their Battle Mountain, Lander County, Nevada, property in 1962. Development of the mine commenced in mid - 1965, and the copper operation began at the end of 1968. The ore, a mixture of chalcocite and chalcopyrite, was milled and floated at a rate of 3, 175 mtpd (3,500 stpd). Because of low copper grade and price, the plant was shut down after about ten years of operation. Attention was then turned to an adjacent low-grade precious metal ore body which contained 2.74 g Au and 3.4 g Ag per mt (0.08 oz Au and 0.10 oz Ag) and minor amounts of copper. Test work revealed recovery by Carbon-In- Pulp treatment would amount to approximately 2.8 mt (90,000 oz) each of gold and silver per year. A rapid engineering and construction schedule resulted in the world's largest, as of late 1980, Carbon-In- Pulp plant being put on-stream in January 1979, with a capacity of 2.720 mtpd (3,000 stpd). Fortunately, the original crushing and grinding plant with all its infra structure was available, and the only modification needed was the addition of a gravity circuit to remove coarse free gold ahead of Carbon- In-Pulp treatment. One of the four primary 500 mm (20 in.) cyclone underflows in the primary ball mill circuit is directed to a secondary ball mill where its product is again cycloned. The cyclone underflow is screened at 3,360 microns (6 mesh) with the undersize being treated on two Pan American 1.07 m by 2. 14 m (42 in. by 84 in.) jigs. Hutch product is further concentrated on two Wilfley tables, a magnetic separator, and on a third Wilfley table where approximately 930 g (30 oz) of gold are recovered each day for amalgamation, retorting, and smelting. Returning to the grinding circuit, the final cyclone overflow is sent to the original plant tailings thickener to obtain proper pulp density for Carbon-In-Pulp treatment. Thickener underflow, at about 40% solids, is then conditioned with air and lime in a series of two 8.5 m by 9.75 m (28 ft by 32 ft) 15O cone bottom Pachucas for oxidation of pyrrhotite. The pulp is then split into two streams for cyanidation for 48 hours in two lines of eight Pachucas of the same size. Pulp is transferred from tank to tank by auxiliary air lifts. Cyanided pulp is then sent to a series of six C. I. P. mechanically agitated tanks with one hour retention in each tank. Originally these

Jan 1, 1981

By Dennis V. D’Andrea, Joseph L. Condon

Laboratory crater tests were performed in two-dimensional plates and three-dimensional .blocks of Holston Limestone. Fractures in the blocks were exposed by sawing through the crater region, and a technique employing dye penetrants is described for examining the resulting fracture systems in both blocks and plates. Crater fracture patterns changed from extension of radial fractures to spa11 fractures parallel to the free face as charge depths were increased. The amount of fractured rock was found to be greater than the amount determined from standard crater volume measurements. Graphs and photographs illustrate these findings.

Jan 1, 1971

By Shahid Islam, Lucian Bogdan

"The maintenance of infrastructures has been of particular concern to the engineering community. As the world’s infrastructure expands and existing infrastructure ages, monitoring and evaluation of the structures have become more critical than ever. A large number of retaining walls, tie backs, slope stabilizations and piles are designed using pre-stressing steel. Many piles and drilled shafts are designed using reinforcing steel. There are few testing methods available to assess these tension and compressive forces. High cost, complicated equipment and limitation of space often prevent these methods from being implemented. DYWIDAG-Systems International (DSI) has been involved in the development, testing and utilization of DYNA Force® sensors to measure the force in the anchors during construction and at any time during the lifetime of the structure. They can be used for bare, epoxy-coated, galvanized and greased-sheathed steel in the bonded, un-bonded, grouted or un-grouted length of the anchor. The sensor is robust and requires no maintenance. Sensors have received attention in terms of accuracy, performance, ease in installation, durability, and cost effectiveness. This paper describes its application in tie-back and anchor force monitoring of retaining walls and bridge abutment and compression forces in drilled shaft reinforcing steel where the data were collected manually, automated and remotely.INTRODUCTIONOur infrastructure is expanding and the existing infrastructure is aging. Some structures are expensive to maintain and some occasionally fail. There is a large demand for implementing health monitoring of structures. Many tie-backs, retaining walls, dams and other geotechnical structures are post-tensioned and many of them need repair using a post-tensioned system. On many occasions during construction and service life of the structure, it is useful to know the force in the post-tensioning and anchor system. Many piles and drilled shafts are designed using reinforcing steel and the compressive forces in reinforcement are unknown. Although there are many methods to measure the tendon force, most of them are cumbersome, expensive, and the accuracy varies depending on the method used.The elasto-magnetic (EM) technology is a novel approach to monitor forces in steel elements. The DYNA Force sensor is built based on EM technology (See Fig. 1). It is composed of a primary coil and a secondary coil (sensing coil). By passing current through the primary coil, ferromagnetic material is magnetized. The sensing coil picks up induced electromotive force that is proportional to change rate of applied magnetic flux (Faraday's law) and relative permeability. As permeability of core changes, output voltage changes. The output voltage is calibrated to measure the force. A readout unit is designed to magnetically energize the steel through the sensor and measure the response of the steel to the process. The readout unit then converts the response into a direct force reading. The sensor has an embedded thermistor which allows for temperature compensation. Due to the diversity of the magnetic property of steel, calibration is done for each type of steel allowing the sensors to perform at their highest accuracy."

Jan 1, 2017

By G. B. Walker

The success of Heavy Media Separation, the static sink-float process, is evidenced by the operation of an estimated 300 installations treating many millions of tons per year of a wide variety of mineral products ranging in value from gravel to diamonds. The static heavy media process is usually limited to the treatment of plus 1/4 inch material. Mr. Victor Rakowsky, who was largely instrumental in the development and application of heavy media separation, recognized the need for a new apparatus and process which would extend the application of heavy media into the finer size range without placing a restrictive limit on the top size of the feed. He recognized the requirement for the application of centrifugal force to augment the force of gravity in separating fines by sink-float techniques.

Jan 1, 1966

By Ramon Augusto Moretti, Henrique da Rocha Severino, Renato Nascimento de Castro, Fernando Cesar Sousa

Rolling stand 12 (LTx) of long steel, installed in the company A, Piracicaba - SP unit, had presented high levels of vibration, which affected its internal components, such as: shaft, gears and bearings, generating downtime. To evaluate this equipment a study was proposed by the following engineering techniques: Conventional Vibration Analysis, Operational Deflection Shape (ODS) and numerical simulation by the Finite Element Method (FEM). In the Conventional Vibration Analysis, high levels of vibration were observed during manufacturing process, especially when the material reaches the equipment. Impacts generate high values in acceleration, on average 80 m/s² peak to peak. In the moment of impact, misalignment of internal components was observed by ODS. Field results were correlated to those obtained by the Finite Element Method, which allowed to calibrate FEM model. Thus, the most effective structural modification already numerically evaluated was implemented in the system. Afterwards, new measurements by vibration and ODS techniques were performed, and attenuation of vibrational levels and operational mode, which overloaded the internal components rolling stand, were verified.

Oct 1, 2019

By Jeremy Butkovich

Dynamic soil-structure interaction (DSSI) analyses are becoming more common in bridge designs, especially in seismically active areas. Because of its proximity to two active fault zones, the Evergreen Point west approach bridge replacement will be base isolated, and will be designed using DSSI. The project team completed two independent bridge designs to satisfy peer review requirements. The designs required substantial characterization of the soil dynamic behavior using both laboratory and in-situ testing. The analyses made use of earthquake time histories spectrally matched to conditional mean spectra. This led to reduced, and more realistic seismic demands on the structure, compared to conventional uniform hazard spectrum matching. The bridge analyses suggest that the preliminary bridge design is relatively conservative. This will allow the design team to potentially reduce shaft/column diameters and reinforcement. The design team estimates that the dynamic analysis design could represent a net savings of around $60 to $90 million compared to a conventional design.

By Greg Nutson, Jeremy Butkovich, Bill Perkins, Hollie Ellis, Paul Bott

"Dynamic soil-structure interaction (DSSI) analyses are becoming more common in bridge designs, especially in seismically active areas. Because of its proximity to two active fault zones, the Evergreen Point west approach bridge replacement will be base isolated, and will be designed using DSSI. The project team completed two independent bridge designs to satisfy peer review requirements. The designs required substantial characterization of the soil dynamic behavior using both laboratory and in-situ testing. The analyses made use of earthquake time histories spectrally matched to conditional mean spectra. This led to reduced, and more realistic seismic demands on the structure, compared to conventional uniform hazard spectrum matching. The bridge analyses suggest that the preliminary bridge design is relatively conservative. This will allow the design team to potentially reduce shaft/column diameters and reinforcement. The design team estimates that the dynamic analysis design could represent a net savings of around $60 to $90 million compared to a conventional design.INTRODUCTIONThe Evergreen Point Bridge conveys State Route (SR) 520 2.6 miles (4.2 kilometers [km]) from Seattle to Medina across Lake Washington. The bridge is located in a seismically active area, and the Washington State Department of Transportation (WSDOT) has determined that the western half of the 1960s-era bridge (the “west approach”) is vulnerable to earthquake damage. WSDOT has begun preliminary design to replace the west approach bridge.The west approach extends about 6,100 feet (1,900 meters [m]) east from Seattle’s Montlake neighborhood, over Union Bay and Foster Island, then into Lake Washington proper (Figure 1). Approximately 5,600 feet (1,700 m) of the replacement bridge would be constructed over water. Subsurface conditions along the bridge alignment consist of 5 to 80 feet (2 to 24 m) of very soft peat and clay, over very dense/hard sand and clay. Multiple pile supported columns support the existing bridge. The new bridge would be supported by 8- to 10- foot-diameter (2.4 to 3.0 m) drilled shafts that extend about 50 feet (15 m) into the underlying very dense/hard soil. To reduce seismic demands on the bridge superstructure, WSDOT has decided to incorporate a base-isolation system into the bridge design."

Jan 1, 2017

By J R. "Dick" Daniel

One of the more common tasks in blast management is the adjustment of: shot geometry, explosive energy, and shot timing parameters to achieve changes in blast outcomes and costs. Many of these shot parameters, once a delayed blast is initiated, are modified by the development of new free faces which change the original or static input values to dynamic values. These newly generated dynamic values are easily calculated and find use in fine tuning shot adjustments and in rationalizing blast outcomes in a systematic manner.

Jan 1, 1996

By J R. "Dick" Daniel

One of the more common tasks in blast management is the adjustment of: shot geometry, explosive energy, and shot timing parameters to achieve changes in blast outcomes and costs. Many of these shot parameters, once a delayed blast is initiated, are modified by the development of new free faces which change the original or static input values to dynamic values. These newly generated dynamic values are easily calculated and find use in fine tuning shot adjustments and in rationalizing blast outcomes in a systematic manner.

Jan 1, 1996

By Tsuda Wakaki, Naoki Takahashi, Natsuki Okuno, Hidenori Takahashi, Ikuo Towhata, Yoshiyuki Morikawa

"Deep mixing (DM) method has been increasingly employed as a countermeasure against subsoil liquefaction in recent years. Pile-type DM, however, is considered to have little effect as a liquefaction countermeasure, because the shear deformation of unimproved soil around the piles cannot be reduced. However, experimental results, which imply that shear deformation of unimproved soil around DM piles can be reduced, were reported. Furthermore, a new plane-arrangement of DM piles has been proposed to mitigate lateral flow induced by liquefaction. The DM piles in this arrangement confront the lateral flow in any direction, compared with the piles arranged in conventional pattern such as square and triangular arrangements. In this study, a series of dynamic centrifuge model tests was conducted to verify the lateral flow resistance of DM plies in the new arrangement. The results indicate that the DM plies can reduce the lateral flow of liquefied ground when the pile displacement and the pile head rotation are restricted. In addition, lateral load acting on DM pile from liquefied ground, which is required for design strength of the DM pile, was investigated.INTRODUCTIONDeep mixing (DM) method has been increasingly employed as a countermeasure against subsoil liquefaction in recent years. The solidified body formed by the deep mixing method is usually block or lattice shape, composed of solidified columns that overlap each other horizontally. Lattice-type solidification has been shown to be effective as a liquefaction countermeasure despite the presence of unimproved soil inside the lattice wall, because the shear deformation of the interior soil is restrained by the wall (Suzuki et al., 1989). On the other hand, it has been thought that pile-type DM cannot reduce shear deformation of unimproved soil around the piles, because the displacement of the pile is less restricted than that of the lattice wall. DM piles have been reported to have little effect as a liquefaction countermeasure, but to be superior in terms of construction cost and applicability around existing underground structures (Koga et al., 1986). However, there are experimental results implying that DM piles have reduced the shear deformation of unimproved soil and mitigated its liquefaction (Yasuda et al., 2003; Tanaka et al., 2003). Yamamoto et al. (2006) conducted dynamic analyses of ground improved with lattice- and pile-type DM. Their results showed that pile-type DM with an improvement ratio of more than 35% reduces excess pore water pressure generated by earthquakes. Furthermore, the new pile arrangement shown in Fig. 1(a) has been proposed to mitigate lateral flow induced by liquefaction. It was developed and has been verified using dynamic model testing in a 1 g field (Takahashi et al., 2010a; 2010b; 2013; Towhata et al., 2010, Morikawa et al., 2014). The DM piles in this configuration interrupt lateral flow in any direction, unlike those placed in square and triangular arrangements."

Jan 1, 2015

By B Darlington, L Sandberg, O Vallati

The D47 and D39 Mechanical Dynamic Extra bolts (D47 MDX and D39 MDX) have been developed in response to the ever-increasing demand from the mining industry for rock bolts with high dynamic capacity. To prove such capacity, Sandvik has performed numerous in situ dynamic testing with the unique Dynamic Test Rig (DTR) (Darlington, Rataj and Roach, 2019; Roach, Rataj and Darlington, 2019). To complement the collection of testing data, Sandvik, in collaboration with the Swedish Research Institute for Mining, Metallurgy and Materials (Swerim) have performed additional experiments in laboratory condition using Swerim’s new drop test rig. This rig utilises a momentum transfer method to apply a dynamic load to the bolt. The sample falls together with the mass until the support beam impacts stationary dampers and the momentum energy is transferred to the bolt. Part of the charged energy is released by the dumpers while the remaining portion is absorbed by plastic deformation and/or displacement of the ground support element. The D47 and D39 MDX bolts have been tested at Swerim’s test facility with different levels of input energy. Six tests were performed at the specification energy of 36 kJ and six tests were carried out with the maximum allowable energy from the facility, ie 44 kJ. The bolts confirmed their dynamic performance absorbing the input energy without failure. The D47 MDX bolt absorbed up to 33 kJ with 150 mm displacement while the D39 MDX bolt absorbed up to 35 kJ with 162 mm displacement. This work will present an overview of the drop test rig at Swerim’s facility and a collection of results of the test performed on the D47 and D39 MDX bolts. The test method and results will be analysed and compared to the tests carried out with the in situ DTR.

Nov 29, 2022

Rendering a solid hydrophobic and solid-fluid particle* attachment in flotation are recognized as not necessarily related (1,2). The attachment is governed by forces of attraction and repulsion which need to be considered. The induction time required for attachment after solid and fluid particle are brought into proximity (3-8) illustrates the point. Laskowski(8) showed that a reduced induction time favoured flotation but detected no change in contact angle, a standard indication of solid surface hydrophobicity. Induction .time is observed in fluid-fluid particle coalescence, there being called a rest time (9-11) The induction time phenomenon is related to the presence of a metastable liquid film (disjoining film (2)) of the continuous phase (water in flotation) which must thin and rupture to permit attachment. The lifetime of this film, which is governed by the rate of thinning and the probability of rupture with thicknesss, depends on a complex interaction of forces. Investigating these forces should help clarify the attachment process. Practical benefits would be improved understanding of slimes flotation (12,13) This paper is concerned with the role of the mobile fluid particle-water interface on the film lifetime, in particular, the role of time-dependent or dynamic interfacial properties resulting from deformation of this interface.

Jan 1, 1975

By J. Drzewiecki, J. Kabiesz

Coal mining using longwall methods of mining can lead to intense disturbances of undermined roof strata. The disturbances may extend beyond the extraction area and the resulted rock mass deformations will appear differentiated. In the case of stiff and undermined roof strata, the energy stored in these rock masses may be frequently dissipated in the form of high-energy seismic tremors. Such events can occur if these strata should fail or „free themselves” either from the constrainment of rock environment or from adjacent strata. It has also been found that the amount of the stored energy closely depends on the size and/or slenderness of these strata. Thus, it would be possible to apply specific preventive measures to reduce the energy of mining – induced seismic tremors. The methods are based on artificial disintegration of the structure of energy – storing strata. One of the most efficient methods is a method of directional hydraulic fracturing, which is regarded as an alternative solution from the traditional blasting and hydraulic methods.

Jan 1, 2003