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By M. R. Henzinger, G. Lenz, A. Gaich, Pötsch, W. Schubert, P. Wagner

"The better the information on the rock mass and its fracture system, the better is the basis for any rock mechanical decision that is required during the excavation process. While in conventional tunnelling free view to the tunnel face is available, possibilities are limited for mechanised tunnelling using a tunnel boring machine (TBM). An approach, already formulated in 2005, is used that produces digital photographs through openings in the cutting wheel of a TBM and merges them into a circular three-dimensional image. The 3D image is then used for geometric rock mass characterisation purposes including geological mapping, for example to measure spatial orientations or determine joint spacing. In the paper the basic concept is described together with first results from a pilot test.INTRODUCTIONA three-dimensional image unites digital photographs with spatial information on the objects/surfaces it shows. Since they combine geometric and visual information they are a straightforward source for geometric rock mass analysis and geological mapping. Their obvious benefits among others are: (i) they allow spatial measurements even in inaccessible regions, (ii) they provide objective and reproducible records of the rock mass conditions, and (iii) they increase working safety (Gaich et al. 2004).Pre-requisite for the generation of 3D images is the acquisition of at least two photographs from the region of interest. From the photographs the imaged object surfaces are reconstructed by means of image analysis using methods from photogrammetry (Slama, 1980) and computer vision (Hartley & Zisserman, 2001). See also Figure 1."

Jan 1, 2015

By Håkan Schunnesson, Kirsten Holme

"When mining high grade, narrow ore bodies, the mining method often implies a very detailed knowledge of the ore contacts to avoid unacceptable ore loss and waste rock dilution. During the past decade, the use of microprocessor based drill monitoring equipment has become an accepted technique, even for percussive drilling. On the basis of the recorded drill performance, such as penetration rate, torque pressure, thrust etc., a fast evaluation of the lithological sequence of the ore zone can be made. In order to evaluate the potential of percussive drill monitoring to pro-vide detailed information of the geometry of the ore body, the technique was tested in the Viscaria copper mine in Sweden during 1996.To provide understandable information to the mine geologist, great emphasis was placed on the separation between the drilling response generated by variations in rock conditions from variations caused by the operator and the drill system. Due to the complicated geology in Viscaria, the drilling response presented to the geologists was separated in two independent signals, one representing the hardness of the rock and one representing the in homogeneity(fracturing) of the rock. With those signals a good separation between different rock types in the ore horizon was achieved.The experience from the Viscaria copper mine is that drill monitoring not only can be used to locate contacts between rock types, but also to characterize rock conditions and, often, also to specify the exact rock type present. Because it is possible to get the drill monitoring information very quickly it is a valuable complement to diamond drilling for increasing the specific knowledge of the geology and the ore body."

Jan 1, 1997

By Sydney C. Mifflen

COAL MINING, with its some 15,000 employees, is directly responsible for the livelihood of one-fifth of the population of the Province of Nova Scotia and indirectly so for that of possibly another fifth. Deposits of coal are known and worked in four counties of the Province, from which is being produced yearly tonnages as noted below: Cumberland County 750,000 tons Piccou County 400,000 tons Inverness County 100,000 tons Cape Breton County 5,250,000 tons TOTAL FOR NOVA SCOTIA 6,500,000 tons Production in Cape Breton county is entirely from the one source, the Sydney coalfield, and not only is this field the most important in respect to output, as is disclosed above, but it is also the largest presently known deposit in the Province and holds the greatest tonnage yet in reserve for future mining. In the light of the above more or less generally known facts, it is trite to remark on the importance of the Sydney coalfield in the internal economy of the Province. On the other hand, not nearly as well-known nor as frankly recognized is its significance in the national life of Canada, for from this field is produced not only 80 per cent of the Nova Scotia coal but over 40 per cent of all coal mined in the Dominion. Another noteworthy comparison can be made from the fact that the Sydney field contributes 22 per cent of all the bituminous coal consumed in Canada, the remainder being made up of 7 per cent mined elsewhere in Nova Scotia, 27 per cent from other parts of Canada (British Columbia and Alberta, principally), while the remaining 44 per cent is imported, practically wholly, from the United States of America.

Jan 1, 1941

By J. Ouellet

The authors participated in a study for a new mine shaft in Saskatchewan?s Athabasca Basin where ground freezing is desired to reduce water inflows. Constraints were imposed on the design in terms of permissible water leakage (less than 10 m3 / hour) inside the shaft. Since the shaft goes through highly permeable formations, water control measures had to be incorporated into the design. Ground freezing was selected as the most reliable and proven method for the sinking and a hydrostatic liner design was implemented. While exploring various technological options available for providing a fully hydrostatic liner, the authors came up with a new design concept that offers a more cost effective solution while meeting all the design constraints. The new liner concept is a composite design using concrete and a sprayed-on membrane system. A proof of concept program comprising laboratory testing and field testing was successfully implemented. This paper presents the innovative liner design, as well as the adapted sinking methodology, developed for this type of project. The new concept offers a new cost effective high performance hydrostatic mine shaft liner comparing favorably with traditional methods. RESUME: Les auteurs ont réalisé une étude pour un nouveau puits de mine dans le Bassin de l?Athabasca en Saskatchewan. Des limites sévères sont imposées sur le design en terme de volume d?infiltration d?eau acceptable (moins de 10 m3 / heure). Comme ce puits de mine traverse des formations très perméables la congélation des terrains a été sélectionnée, une méthode éprouvée et fiable. Un design hydrostatique a été choisi pour le revêtement du puits. Dans le processus de design, les différentes technologies disponibles ont été étudiées. Les auteurs ont développé un nouveau concept de revêtement composite offrant un rapport performance/prix plus avantageux que les technologies conventionnelles. Le nouveau design proposé est composé de béton et d?une membrane projetée. Un programme expérimental a été réalisé pour démontrer la faisabilité du concept. Cet article présente le nouveau concept ainsi que la méthodologie de fonçage de puits adaptée. Ce concept innovateur offre un revêtement hydrostatique performant à un cout avantageux par rapport aux techniques de construction utilisées jusqu'à maintenant.

Jun 1, 2012

By N. W. Xu, C. Sha, F. Dai, Y. G. Zhu, B. Li

Underground caverns stability and excavatability of rock masses are of significance in geotechnical engineering, in both design and construction stages. Risks associated with underground group caverns of Houziyan hydropower station in southwestern China are growing as a result of continuous excavation-induced unloading. To improve our understanding of the underground caverns instability and resolve the complex subsurface conditions of the highly fractured rock mass, a high resolution microseismic monitoring system was established in the deep underground caverns, pursuing the relationship between the measured data about microseismic activity and excavation damage zones of surrounding rock mass. Through analyzing the tempo-spatial distribution of microseismic activity, excavation damage zones and potential risk regions in underground caverns were identified. Furthermore, the correlation between microseismic activity and pre-existing geological structures, as well as traditional monitoring was analyzed. In order to validate the correlation between seismicity and potential slip surface of underground caverns, a model was implemented into numerical code to further evaluate the deformation and stability of surrounding rock mass. The monitoring results demonstrate that microseismic events mainly occur at high stress concentration regions, which coincides with the results obtained from numerical analysis. Therefore, the comprehensive method incorporating microseismic monitoring and numerical analysis, as well as traditional monitoring and filed observation has been proven to be very promising in deformation and even instability prediction of surrounding rock mass in underground caverns subject to delineation of potential slip surfaces and excavation damage zones.

Jan 1, 2015

By M. Pötsch, A. Kluckner, P. Söllner, W. Schubert

"The in situ block size is a key parameter in the geomechanical characterization of rock masses. It describes the fracturing of the rock mass and thus is a measure for the degradation of the rock mass strength. Several classification systems use the in situ block size. For instance, the Geological Strength Index (GSI) requires the “blockiness” and joint surface condition factor as key input parameters. The “blockiness” has recently been related to the in situ block volume (Cai et al., 2004). Due to the limited information about the internals of a rock mass, it is not possible to determine the in situ block size directly. Currently, the in situ block size is determined by calculations using oversimplified models, vague estimations or, due to the lack of relevant information, it is neglected. As remote measurement systems have become available for rock mass characterization, a more comprehensive record of discontinuities can take place. Measurements can be performed on exposed rock outcrops and in particular on tunnel faces and walls, delivering the location, orientation, spacing and persistence of discontinuities at an arbitrary number and locations. An estimation of the in situ block size at the same level of sophistication is still not available. This paper aims at examining the relationship between visible and measureable information at the rock surface, and the in situ block size. Three-dimensional block model simulations were performed using the block model engine of the distinct element code 3DEC. Initial investigations focussed on the minimally required observation area in order to obtain reliable block size distributions. Based on a representative volume element, a reference distribution of the block area at the observation area for a specific discontinuity system was determined. Subsequently, the size of the observation area was decreased stepwise and each new distribution was compared to the reference distribution. For all analyzed systems, it turned out that the mean block area must be smaller than 1% of the observation area to achieve a reliable block size distribution. Further simulations focussed on discontinuity systems with three non-persistent sets. The results were compared to the formula proposed by Cai et al. (2004). A transformation factor T was introduced which replaces the persistence terms in Cai et al.’s proposed formula. The factor describes the correlation between block volumes generated by persistent and corresponding non-persistent discontinuity sets. The simulations included the variation of the discontinuity set spacing, persistence, and orientation. The mean and additionally the 25%-, 50%- and 75%-quantiles of the block size distribution were analyzed. Examining all values for the transformation factor the distribution can be described by a power function with a negative exponent. The function depends on the persistence only. Finally, the results of random simulations were compared to the analytical formula using the transformation factor. The predicted mean and selected quantiles show a good agreement with the simulation results. It gives a comprehensive picture about the block size distribution in discontinuity systems with three non-persistent sets."

Jan 1, 2015

"With the globalization of the mining industry, many companies are now seeking to invest in underground diamond mines, with the purchase of small diamond pipes being seen as particularly attractive. However, recent experiences in South Africa have shown that many projects fail due to a lack of awareness of the hazards associated with diamond mining. In this paper three significant hazards are dealt with — mud rushes, block crushing, and implementation of an inappropriate mining method. Measures that assist in the prevention of these three hazards are given.IntroductionFor over a hundred years, South Africa has been seen as the centre of the diamond mining industry, possibly having the largest number of operational underground diamond mines in the world. Despite the fact that this industry has been dominated by large mines of De Beers Consolidated Mines Limited, many small underground mines have operated profitably for a number of years, exploiting diamondiferous fissures and pipes. In the last decade there has been renewed interest in these small operations from international companies. However, many of these projects have not realized their full potential owing to a lack of appreciation of the hazards inherent in the operation of a diamond mine.Hazards Associated with Diamond MiningIn the development of a diamond mine, the mining company must be aware of the hazards associated with diamond mining. There are three main hazards: (1) mud rushes; (2) block crushing; and (3) selection of an inappropriate mining method (not a natural hazard, but a planning induced hazard). Each of these hazards will be dealt with in turn in the following sections."

Jan 1, 2000

By Jos. Kalbhenn

MR. G. G. BOWSER: Mr. Kalbhenn's paper is an excellent one and is a concise description of a very interesting piece of work. It is well known that a great deal of preliminary study was given to this job before the final plans were made. It is due to this thorough preparation .chat the work progressed so satisfactorily, smoothly, and safely. The ideas carried out in the construction of the hardwood pack, timbered compartment, inclined raise, loading chute, and steel-boomed room, all contributed to a successful conclusion of the work. The extra care in being certain that the compartment shafts were well timbered was especially necessary on account of the difficult blasting conditions. In other words, the foundations .of this job were well and truly laid. The blasting in this work was very difficult due to the nature of the Strata. Working under an ever precarious roof condition and completing .this job with only two lost-time accidents is a record of which to be proud. The shaft men engaged on this work are also due for praise. I regret I did not visit this work while it was in progress. It was not in lack of interest. This, however, more or less proves that the blasting end .of this job went along with practically no trouble. I have seen the nature of the rock, as I made several visits to the tunnels while they were being put through from the Phalen to the Harbour seam. According to figures in Mr. Kalbhenn's paper, the explosives consumption works out to 1.61 pounds per cubic yard of rock in the solid, or 0.8 pounds per ton. The explosives consumption in the tunnels ran from 2.86 to 3.46 pounds per cubic yard or an average of 1.58 pounds per ton of rock. Of course, the rock in the shaft was blasted in the most economical way possible, as far as powder costs are concerned, as the face advanced at close -wright angles to the strata and gravity was acting with the explosive. The tunnels were driven nearly 'end on' the strata and bottom holes had to be lifted, and I believe there was some re-drilling of ribs left in the floor. I would like to congratulate Mr. Kalbhenn on his very fine paper.

Jan 1, 1944

By C. R. Tang

The respirable dust real-time monitoring equipment export information is complex, and electromagnetic wave wireless transmission is affected largely under mine conditions. The respirable dust concentration information transmission method based on led light equipment is proposed. The respirable dust concentration data of the individual real-time monitoring equipment is encoded to fit the system transmission; the encoded signal is modulated onto the LED mine lamp; the light signal is transmitted by the spatial channel; the signal is received by the receiver to the photoelectric conversion to restore the respirable dust concentration data for subsequent processing. Simulation and verification experiments showed that the respirable dust concentration information transmission method based on led light equipment can achieve the LED miners? lamps visible light wireless data transmission.

Aug 1, 2013

By S. Shimaya, T. Maejima, M. Shimo

"The authors conducted the in-situ gas-tightness tests in a fractured rock at the Namikata underground LPG storage site in Ehime prefecture, Japan. The test consisted of two independent setups, a gas-tightness test that used boreholes, and a chamber-scale test that used a horizontal drift sealed with a concrete plug. In each test, the gas pressure was increased up to the onset of the measurable gas flow to obtain the maximum containment pressure. This paper discusses the hydraulic conditions for gas leakage initiation and the importance of the pore pressure measurement for monitoring the gas-tightness of the LPG storage cavern based on the test results.INTRODUCTIONJapanese first underground LPG storage plant was constructed by JOGMEC, the Japan Oil, Gas and Metals National Corporation, at Namikata in Ehime prefecture in granitic rocks (Kato et al., 2007). The “hydraulic sealing principle” (Åberg, 1977) that utilizes groundwater flow into an unlined cavern to prevent the leakage of gas through fractures in the surrounding rock mass was employed for storage of LPG. This paper describes the results of the in-situ tests performed at the Namikata Site to obtain information on fundamental gas-tightness characteristics of fractured rock. Two types of in-situ tests, a borehole gas-tightness test and a chamber gas-tightness test, were carried out near the storage caverns. Figure 1 shows the cavern layout of the Namikata underground storage plant and the test locations. The storage facilities consist of three caverns (W26m×H30m×L485m). The cavern crown lies at a depth of 150m below the sea level in Cretaceous granitic rock (Figure 1). Water curtain boreholes excavated from the water gallery tunnel at EL-125m level are located above and side of the caverns to prevent water drainage from fractures during the construction stage as well as during operation. The borehole tests were performed from a drilling adit excavated from the eastern end water gallery tunnel, while the chamber test was conducted at the southern edge of an exploratory drift extending from the central water gallery tunnel."

Jan 1, 2015

By L. H. Van Loon, E. G. Crayston, A. F. Heather

"IntroductionTHE PROPERTY of Madsen Red Lake Gold Mines. Limited. comprises fifty-eight claims located between Russet and Faulkenham lakes in Baird and Heyson townships of the Patricia portion of the District of Kenora. The mine is seven miles •by road from the hamlet of Red Lake. This latter centre is .connected to the Trans-Canada Highway at Vermillion Bay, Ontario, by provincial highway No. 105 which has a total length of one hundred and thirteen miles.The Madsen property went into production on August 11th, 1938, with a milling plant rated at 300 tons per twenty-four hours. Changes made in the crushing plant during October, 1938, allowed a •finer feed to be delivered to the mill and increased the milling •capacity to 400 tons per twenty-four hours. During 1948, steps were taken to add an additional 400-ton capacity unit to the milling plant. This latter work was completed by May, 1949, giving the present total milling .capacity of 800 tons per twenty-four hours.It was realized in the early 1940's that, eventually, considerable material suitable for backfilling in the mine would be required. As there were no large deposits of gravel or sand anywhere near the mine, officials of the Company considered it advisable to investigate the feasibility of using mill tailings for mine •backfill. Since Madsen mill tailings contain approximately 80 per •cent of minus-200-mesh material, it was not considered practical to use them for underground backfill without first removing the finer material. as the slimes present in a product of this fineness would without doubt preclude any drainage whatsoever. Table I gives a sizing analysis of Madsen mill tailings and Table II a quantitative chemical analysis of the ore."

Jan 1, 1954

By I. Pérez-Rey, J. Arzúa, L. R. Alejano

"The decrease in strength with increasing rock specimen size is usually associated to the increase in the number of defects inside the specimens at small scale (centimeters) but also to the role of the rock mass structure at the rock mass scale (meters to decimeters).This matter of concern was particularly focused when determining the size of pillars in underground mines. Some formulae regarding strength of pillars have been proposed but they usually consider only the size and shape of the pillars and the strength of the intact rock. The structure tends to be overlooked or hidden behind the scale, but it is probably very relevant. For standard tunnel design, the approach by Hoek and Brown (1997), taking the structure into account in terms of the GSI, is commonly used. However, this approach does not specifically consider the size of the tunnel. Thus, a size larger than the so-called representative elementary volume is implicitly contemplated.The authors have recently performed a lab study on the effect of the structure in the strength, deformability and post-failure characteristics of granite at lab scale (NX size) extended here. This experimental program included intact and artificially jointed rock specimens. Obtained results permit to observe the changes in strength, deformability and post-failure behavior of this “small scale rock masses”, associating the role of the structure to the observed complete stress-strain response of the specimen, which can improve our understanding of the actual complete mechanical response of rock masses."

Jan 1, 2015

By M. G. Beukes

"In South Africa most of the large gold mines operate between 1500m and 4500m below surface where reef is accessed initially through a vertical shaft system then via a network of tunnels and mined in either a longwall, sequential grid or scattered mining configuration. Due to the complexity of the ventilation networks used to ventilate these mines and the potential disastrous consequences associated with underground fires, it is of utmost importance that these mines are managed in such a way that underground fires are prevented. However, if they do occur the fires are managed to firstly prevent the loss of life and secondly protect the infrastructure and viability of the mine. The aim of this paper will be to: • Discuss current SA mining legislation regarding underground fire prevention and control. • Examine these fires from a risk management perspective by means of a bowtie assessment. • List and discuss the major Threats and Consequences as determined by the bowtie assessment. • Discuss the various prevention and consequence controls for deep level underground fires. • Examine how to effectively run an emergency control room. From this, a practical way of designing, implementing and managing an underground fire management system is explored. Lastly, the paper identifies new technology and ways of thinking and how these can be used to combat underground fires. INTRODUCTION The orebodies of South African gold mines are generally narrow tabular structures that vary in thickness between 0.8m and 1.2m with an inclination of between 200 and 700. This, coupled with depths of between 1500m and 4500m, as well as the unpredictable geology, creates unique challenges and significantly impacts on mine designs and mining methods. In general, gold bearing reefs are accessed initially through a vertical shaft system then via a network of tunnels and mined in either a longwall, sequential grid or scattered mining configuration (Figure 1). Mining is very labour intensive with very limited mechanisation opportunities and this increases the risk to human life if an underground fire occurs. On 16 September 1986, one of the worst mining disasters in SA mining history took place when 177 mineworkers were killed at Kinross Mine. An acetylene tank sparked flames that swept through the mining tunnel igniting plastic covering on the wiring and the flames also set fire to polyurethane foam. The burning plastic combined with polyurethane and the toxic fumes that filled the shafts caused the miners death. This incident was a stark reminder of the serious consequence that underground fires can have on human life as well as the crippling financial and asset impact for the mining companies. Over the past thirty years, the SA mining industry reduced the number of mine fires significantly by replacing normal timber support with fire retardant treated timber, alternative support systems such as backfill and elongate support and many other fire prevention initiatives. Although the number of fire incidents and number of fatalities due to fires does not show a direct correlation because of various factors, the controls put in place against fires has had an impact on the number of fire and explosion fatalities (Figure 2)."

Jan 1, 2019

By Sang-Kyun Woo

The electric power conduit (EPC) in Korea has been constructed since 1978. Facing the challenge of safety and sustainability of the EPC, it is urgent to develop an inspection strategy and maintenance system for the structure based on the concept of life-cycle management. This paper introduces the newly developed mobile inspection and diagnostic system of the EPC. The novel aspect of this particular system is the integration of non-destructive mobile inspection techniques with BIM (Building Information Modeling) and LBS (Location-Based Service). BIM is an ideal tool and platform for developing an inspection and diagnostic system, and RFID (Radio Frequency Identification) is a useful tool to construct USN (Ubiquitous Sensor Network) for LBS. The goal of this research is to establish an EPC inspection and diagnostic system concept based on BIM and LBS using RFID. In this research, a BIM model of OPENTBM tunnel for EPC will be established to show the integration of 3D CAD with the inspection data. An EPC?s maintenance database, which includes the deterioration types of the structure, inspection records, and repair methods, was designed to interact with the BIM. The system will be implemented by the BIM with the related database, in which the construction geometry and all related information are stored. The proposed system was designed to utilize the inspection and diagnostic system under the USN environment using RFID in EPC directly.

Aug 1, 2013

By B. R. MacKay

Introduction During the past six seasons the writer has been engaged in semi-detailed investigations on the coal areas lying along the front of the Rocky mountains between the Brazeau river and the Smoky River Coal Reserve (see Map, Figure 1). The purpose of this paper is to present some observations pertaining to the stratigraphy and structure of the district, touching especially upon the lithological units into which the Lower Cretaceous sediments have been divided, the thicknesses of the formations at different localities, the number, thicknesses and horizons of the principal coal seams, and the structural conditions which exist in the various fields.

Jan 1, 1930

By Victor Dolmage

Introduction Although gold production in British Columbia began in 1859, lode gold was not produced till 1893. Since 1900, the annual production of lode gold has fluctuated between $3,000,000 and $6,000,000. About twenty per cent of this production may be regarded as by-product gold from base metal mining. The remainder comes from a few isolated but important mines, such as the Rossland mines, Nickel Plate, Surf Inlet, Premier, Pioneer, Bralorne, Reno, and Cariboo Gold Quartz, and from several less important mines. All of the above, except Pioneer, Bralorne, Reno, and Cariboo, are approaching or have reached the point of exhaustion, but all are now receiving, under the stimulus of the. present gold-mining boom, drastic resuscitative treatment, with, in some cases, signs of resurrection. Notwithstanding this, however, the main interest at the present time is focussed on the Bridge River and Cariboo fields. Both these fields were discovered in the early 'sixties' and, apart from the Cariboo placer production, both have from time to time contributed small amounts of lode gold; but it is only during the last two years that the real possibilities of these areas were discovered. and that they began to assume the appearance of goldfields of major importance. The two fields are sorme three hundred miles distant from one another and contain deposits of distinctly different types, so that the only reason for including them in one article is the fact that they came into prominence more or less simultaneously and at a time coinciding with, but not otherwise related to, the present gold-mining boom.

Jan 1, 1934

By C. E. Lancelle, J. T. Volk, H. F. Wang, D. Fratta

"The Main Injector Neutrino Oscillation Search (MINOS) Near Detector Hall at Fermilab and the Lafarge – Conco Mine are located approximately 100 meters underground in the Galena-Platteville dolomite just below its contact with the overlying Maquoketa shale in Northeastern Illinois, USA. A new cavern was excavated adjacent to the MINOS Near Detector Hall at Fermilab to house the near detector for the Off-axis Neutrino Appearance Experiment (NOvA) program. During this excavation approximately 1150 cubic meters of shale rock were removed. Tiltmeter arrays consisting of a series of hydrostatic leveling sensors (HLS), which are spaced regularly over a total distance of 50-to-100 meters, were used to monitor subsurface deformations. The tiltmeter response in the MINOS Near Detector Hall due to the NOvA cavern excavation is approximately thirteen times the estimated response based on using laboratorydetermined properties. The discrepancy between modeled and measured tilt is likely due to differences in Young’s Modulus in the rock mass versus in a small laboratory sample. Amplitudes of measured solid earth tides differ from the amplitudes of theoretical solid earth tides by up to 40 percent for both arrays. This is likely due to a local heterogeneity or discontinuity.INTRODUCTIONLong baseline tiltmeters have been used to record small earth movements since the early 1900s. One of the first studies using long baseline tiltmeters to measure earth tides was published by Michelson (1914). He used a leveled 152-meter long, 0.15-meter diameter tube half-filled with water connecting two concrete-lined pits. The pipe was trenched 1.75 meters underground in Williams Bay, Wisconsin in a sandy-clay soil. Initially only an east-west line was used, though a north-south line was added after it was seen that viable results were obtained. Measurements were made by hand either hourly or once every two hours depending on the time of day. When compared to 0.7 times the calculated earth tides, the tiltmeter signal matched almost exactly. This excellent result began the use of long baseline tiltmeters to measure small earth movements."

Jan 1, 2015

By S G. Bergdahl

Underground mining in Sweden is today characterized by mechanization and automation, owing to the rising cost of labour. Drilling in drifts and tunnels is still essentially done with jackleg drills, but rigs wh1ch make it possible for one man to operate two or more drills are now frequently used. Large jumbos for longhole drilling, with two drills operated by one man, are used, especially in sub-level caving. A special drill-rig for drilling through overburden and blasting without removing the overburden has been successfully used in canals and also in ports, where blasting is per-formed under water. The increased use of mining methods based upon long blastholes is a result of the development of equipment for drilling long straight holes. The most common mining method in Sweden is sub-level caving. Extensive research, with model tests, has been carried out in order to determine suit-able dimensions of drifts, sub-levels and drilling patterns. The results have been tried in practice and have given increased yield and less waste rock in hoisted ore.

Jan 1, 1963

By Y. W. Pan, Y. R. Liu

The disturbed natural rock mass tends to equilibrium state accompanying with non-equilibrium evolution process which has significant influence on the long-term stability of engineering structure. The deformation development in the non-equilibrium evolution is determined by two intrinsic processes, trend to equilibrium and damage development, which can be illustrated by evolution of excavated tunnel. Thus the creep and damage must be taken into account in study of non-equilibrium evolution process. Within Rice’s irreversible thermodynamics with internal state variable (ISV), the conjugate force function which equals to zero is a convex surface which divide the stress space into two parts, called equilibrium and nonequilibrium stress space respectively. The concept of effective stress of non-equilibrium has been proposed, in which the stress difference (d - d ) are the effective driving forces of non-equilibrium evolution process with hardening and damage effective. The formulations of inelastic strain rate and energy dissipation rate have been recast in the form of effective stresses. The inelastic complementary energy (ICE) is proposed to measure intensity of non-equilibrium evolution of material system. The specific equations of conjugated forces and kinetic equations of internal state variables are presented. The ICE and rate of energy dissipation are all calculated to be used to evaluate long-term stability of geo-engineering. The results show that rate of energy dissipation may be more convenience and flexible than ICE for internal state variable constitutive equation of rock mass.

Jan 1, 2015

By M. R. Henzinger, W. Schubert

"The quality of the backfill applied at a shield driven tunnel is of significant importance failure of the lining. The used material also affects the interplay between support and excavation behaviour.In this research the state of the actual bedding situation is investigated by an analytical approach, laboratory tests and numerical simulations. The numerical simulation using continuum methods have shown shortcomings. These shortcomings regarding the instability of large strain simulations restrict the possibility to reproduce the relocation of the backfilling material. The performed scaled model tests have shown that the regripping process of a double shielded tunnel boring machine affects the soil failure within the gap. With the analytical results the influence of the wall friction can be predicted. Therefore the angle of the failure surface can be determined. The results have shown that the wall friction significantly increases the failure angle. INTRODUCTIONFor tunnel boring machines (TBM) with single (SM) or double (DSM) shield, precast liningsegments are used as rock support. These segmental linings are installed within the protection of the TBM shield. In order to reduce the friction while advancing, the shield diameter is smaller than the diameter of the cutter head and therefore also smaller than the excavation boundary. The difference depends on the expected radial convergences. Since the lining segments are mounted within the shield the steering gap between the shield and the excavation boundary increases and is hereinafter called annular gap.In the process of tunneling in hard rock, the annular gap is usually filled with fine grained and closely graded gravel, termed as pea gravel. The backfilling process starts as soon as possible after the shield tail passes the lining. Due to the operational procedure within the working area of a TBM, a fully backfilled annular gap might not be established after every ring closure. This leads to an unfavorable distribution of the pea gravel leaving the segmental lining partially without bedding. Segmental linings can develop sufficient resistance only when properly bedded."

Jan 1, 2015