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By Nikolaus Schneider

"Abstract: The combination of failure in joints of diaphragm walls and their exposure to water pressure may have far reaching effects ranging from water leakage to the risk of catastrophic loss of stability for the retaining wall and civil structures behind it. Investigations of imperfect joints in diaphragm walls have led to the development and testing of a quality tool to monitor the joint integrity of diaphragm walls during construction. By applying independent mechanical sensors (“joint inspector”) to the steel frame of hydraulic or mechanical grabs, it is now possible to record the surface conditions of exposed primary joints during the construction of secondary panels. This allows for the implementation of corrective action during the construction process should joint quality not indicate a watertight connection to the adjacent panel. The joint inspector, used for different types of stop ends, was tested on a full scale test field at several construction sites. The implementation of this new quality tool drives a new quality standard for deep excavations in inner city areas.General introduction to diaphragm wallsDiaphragm walls are reinforced concrete elements constructed using bentonite slurry to temporarily support an open trench in the ground. They are used in two main fields of application in civil construction, as foundation elements for vertical and horizontal loads (barrettes) and as retaining walls for excavation pits.Particularly for deep excavation pits in inner city areas, diaphragm walls are used as temporary or permanent walls of retaining walls. Alternative retaining wall systems would be secant pile walls, sheet piles or soldier piles, but these have disadvantages in structural strength when compared to diaphragm walls. If the vertical load of existing buildings next to the excavation pit has to be accommodated, the most practical solution can be found using diaphragm walls supported by prestressed anchors, steel struts or slabs."

Jan 1, 2014

By N. Kumar Kittusamy

ALTHOUGH MANYSTUDIES HAVE SHOWN an association between operating heavy construction equipment and symptoms of musculoskeletal disorders (MSDs), little research has been performed that systematically characterizes the exposure of operating engineers to ergonomic hazards. This study evaluated: 1) vibration at the seat/operator interface;2) transmissibility of vibration in the Z-axis; 3) psychophysical ratings of vibration level and vibration discomfort; and 4) postural requirements of the job. Results indicate that the digging operation had higher levels of total weighted acceleration than high- or low-idling conditions. Transmissibility data showed that the seat amplified vibration, particularly in the lower frequencies. Seats demonstrated that they may not be sufficient in protecting operators from long-term effects of vibration exposure. High positive correlation was found among subjective ratings (vibration discomfort and vibration level), but moderate positive correlation was found between subjective ratings and quantitative vibration levels. Postural evaluations revealed that the operators were required to assume awkward postures of the neck, shoulder and trunk while performing their jobs. Work-related injuries and illnesses pose a continuing threat to the health and well-being of American workers. The construction industry has been historically recognized as having higher rates of fatality, injury and illness than other industries (McVittie285+; BLS). In 1994, an estimated 218,800 lost-work-day injuries were reported in the construction industry (BLS). Construction also had the second-highest incidence rate for sprains and strains. Although the industry has made progress since then, injuries and illnesses, including MSDs, continue to because for concern.

"Air Products approached LAC Minerals in 1987 to initiate trials with pure oxygen in the leach circuit at several LAC facilities in Canada. This paper gives an overview of oxygen use and covers specific operating data from the Doyon and Terrains Aurifères mills near Val D'Or in northwestern Quebec. LAC also uses oxygen at the Macassa mill in Kirkland Lake, Ontario.In addition to the LAC facilities, oxygen is currently in use for test purposes at the Holt McDermott mine in Kirkland Lake, Ontario and the Camflo mine near Val D'Or.There are two requirements for oxygen in the cyanide leach mill. Firstly, oxygen is required in the familiar gold dissolution reaction as follows:(1) 4 AU (s) + 8 NaCN (aq) + 02 (aq)+ 2H 20(aq) - 4NaAu(CN) 2(aq)+ 4Na OH(aq)Of the reagents on the left side of the equation, the availability of gold is fixed by the ore in question. Obviously, water is available in excess, 1eaving cyanide and oxygen as the limiting constituents in the process. Most mills operate with an excess of cyanide, which is fairly closely monitored. Dissolved oxygen levels, however, are not normally watched very closely and find their own level based on the temperature, the availability of compressed air and the ability of the ore to consume oxygen.Typical D.O. levels are in the 3-8 ppm range, however levels less than 1 ppm are not uncommon for refractory ores.With pure oxygen, dissolved oxygen levels as high as 30 ppm can be achieved. (Figure #1). This greatly accelerates the kinetics of the leach reaction and may also shift the reaction further towards completion thus increasing gold dissolution slightly."

Jan 1, 1990

By Reda M. Bakeer

"An approach slab is the roadway segment that immediately follows a bridge intended to provide a smooth transition between the two elements. Some approach slabs have developed rough rideability with time due to differential settlement between the roadway embankment and the bridge. Soils in south Louisiana are generally poor and highly compressible and, therefore, pile-supported approach slabs were occasionally used. Timber piles of variable lengths are driven into the soft soils where no appreciable toe support exists. This resulted in the soils both supporting loads through shaft resistance and yet experiencing long-term consolidation settlement. Field testing and review of the records of over 120 approach slabs constructed in south Louisiana yielded the conclusion that their performance is primarily governed by negative skin friction (downdrag) imposed on the relatively short timber piles. A software (TU-DRAG) was developed to evaluate the deflection profile of a pile-supported approach slab based on its geometry and conditions of the underlying soils. It evaluates the effect of dragload considering the number and spacing of the piles at each transverse row and their variable lengths along the approach slab. TU-DRAG was utilized in the design of two transportation related projects which have been in service for more than 10 years.INTRODUCTIONThe problem of differential settlement at bridge approaches or “the bump at the bridge” has been recognized for many years. Research studies (1986, 1989, 1997, 2009 and 2013) by the Transportation Research Board (TRB) and the Federal Highway Administration (FHWA) provided comprehensive evaluations of the performance of bridge approach slabs by assessing their field conditions and construction and maintenance records. Various states have also performed their own studies to investigate the performance of bridge approach slabs. The studies considered various types of structures including soil- and pile-supported approach slabs, integral bridge abutments and open-end abutments. Recommendations were provided for the design of new structures and for maintaining and repairing existing structures. Guidelines were offered regarding tolerable movements of bridges and their foundations based on measurements of vertical and horizontal movements of 580 bridges Moulton (1986). Vertical and horizontal movements greater than 102 mm (4 inches) and 51 mm (2 inches), respectively, were considered intolerable. Tolerable limits for angular distortion (differential settlement to span length) were suggested to be 1/250 and 1/200 for continuous and simple spans, respectively. It was reported that a differential settlement greater than 13 mm (0.5 inch) at the bridge interface would be sufficient to constitute a “bump” requiring mitigation."

Jan 1, 2017

By Peter Radziszewski

"Comminition process costs, which typically represent an important contribution to mining operating costs, can themselves be divided roughly between energy and liner /charge wear. As such, developing the ability of predicting mill wear will allow a more accurate estimation of wear costs and therefore their control. In this paper and based on the possibility of estimating energy dissipated in impact and abrasion by using a discrete element charge motion model for mill charge motion simulation, media wear will be investigated principally as a function of three wear mechanisms : impact, abrasion and corrosion. Experimental results will be used to identify a total media wear model. Model results will be compared with real mill data from three operating Australian mines. These preliminary results show for the cases tested that the overall average error, as compared with the observed cases, is 0 % with a standard deviation of 66.1 %. Results from the Bond abrasion index tests, for the same cases investigated, give an overall error of 73 % and a standard deviation of 192.5 %. Further work is in progress to improve test procedure, validity and confidence.INTRODUCTIONComminition process costs, which typically represent an important contribution to mining operating costs, can themselves be divided roughly between energy and line / charge wear. In Greenfield situations where the estimation of operating costs is critical in determining project feasibility, the level of confidence in such estimates becomes quite important. With regards to media wear, the Bond abrasion test currently serves as the standard media wear prediction device. However, as shown [l, 21 test results once compared with actual wear rates can vary greatly. Figure 1 shows test results as compared with 15 cases. Average error over this data is 73 % with a standard deviation of 192.5 %. As such, developing the ability of more accurately predicting mill wear will allow greater confidence in wear cost estimation and therefore their control."

Jan 1, 2001

By I. Matsunaga, K. Aoki, W. -j. Jung

Blasting is widely used in mining and basic construction because of its speed and economy to destroy the rocks. Blasting has the advantages of reduced excavation costs and shorted construction time when compared to the use of heavy machinery for excavation and cutting such as that with a tunnel boring machine. There are numerous problems with blasting, including the noise, vibration and fly rock. So it is necessary to accurately evaluate fracture mechanics of rocks on the dynamic loading condition to control the fracture process of the blasting. The tests using Hopkinson's effect for the dynamic condition using the precise detonators were performed for various strain rates on three different kinds of rocks. In the tests using Hopkinson's effect for the dynamic condition, the high-speed camera was used to observe the fracture process of the test sample rocks. As the results of experiments there was an increase in the tensile strength of rock with an increase in the strain rate for three kinds of rock on the dynamic loading. The tensile strength of rocks with high porosity on the water saturation condition was decreased on the both static and dynamic condition. It is clear that the strain rate and water saturation were influenced to the tensile strength of the rocks.

Jan 1, 2003

By Jochen Belz, Allan Henneker, Nod Clarke-Hackston

For the construction of tunnels and other underground structures, extraction of the exact amount of material is of paramount importance both economically and for engineering purposes. In the Sequential Support Method (NATM) immediate (sequential)and smooth support by means of shotcrete, steel arches, lattice girders and rockbolts, either singly or in combination are used; cutting of the precise (albeit sometimes of complex geometry) profile is an integral part of the method. In order to save unnecessary excavation and provide better information to the machine operator, VMT GmbH has developed a system to support precise excavation of the tunnel profile when using road headers or other partial face cutting machines. This paper outlines the principles of this system with examples from Australia, Ger-many, Sweden and Spain and will cite examples of typical savings achieved.

Jan 1, 2007

By M. H. Pelkki, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Research has shown that excessive soil compaction is detrimental to the establishment of trees in reclaimed soils. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed soils. It is believed that reclamation practices which minimize soil compaction will produce better results when forestland is the intended post-mining use. The University of Kentucky has developed reforestation test cells on reclaimed soils at a surface mine in eastern Kentucky to test this hypothesis. Each test cell has been planted with various species of trees, and since 1997, data have been collected at these test cells for soil average dry bulk density, average penetration resistance, average depth to refusal, and average survival rate of trees. These data have been correlated to determine the relationship between soil compaction and tree survival rate. It is believed that the two soil compaction parameters may ultimately be used to predict tree survival rates on reclaimed surface mined lands.

Jan 1, 2001

By P. V. Chandramohan

"In ports, piled berths are designed and constructed for berthing of ships with a finite draught. Piles in a bridge foundation also have a large free stand above scoured level. The piles of these structures have to withstand large horizontal forces imparted by the impact of the approaching vessels or due to longitudinal and transverse action in a bridge. It is also imperative that these piles have to project out of the dredged / scoured bed. These piles are normally designed as slender compression members subjected to bending also. They are subjected to vertical load tests for assessing the soil resistance. Lateral load tests, as a rule, are also stipulated. IS and IRC codes stipulate a deflection criteria for lateral load test to arrive at the capacity. These tests are usually conducted on a working pile by jacking out two piles. At the time of the test, pile will be free headed. But in service, piles are fixed head. There is a large difference in deflections between a fixed head and a free headed pile. Besides, a free headed pile will be subjected to a much higher bending moment than the fixed head one. This will put the working test pile under risk of breaking during the test. The problem is analyzed with case studies. INTRODUCTION Vertical capacity of piles is assessed by static formulae. This formula is based on the soil properties obtained from random soil exploration and laboratory and in-situ testing. Since soil is not a homogeneous medium, properties can vary. The design parameters taken for computations may be different from the ones at the interface of the pile with the soil. The best way is to find out is by a load test. The code IRC:78-2014 has rightly stated that initial load test is part of the design process. This is true with the vertical load test. But there are certain problems with the purpose and inference of the lateral load test. In both the tests the criteria for acceptance is the quantum of movement of the point of application of the load. In the former, the movement is vertical and depends more on the compression of the soil than the compressive strain in concrete. But in the latter, this movement is partly on account of the flexural rigidity of the pile and partly due to the horizontal compressibility of the soil. The role of rigidity of the pile is more when compressibility of the soil is higher. Lateral load test is done by jacking one pile against another because it is difficult to get an independent horizontal reaction. Please see Fig.1 Photo."

Jan 1, 2015

By Qing Bo

In this study, the cobalt oxide precursor was prepared in open-style reactor in the condition of high reactant concentration, and then the precursor was decomposed to obtain the cobalt oxides (Co3O4). The effects of some factors on the cobalt precipitation, the particle size and size distribution, and the micro-morphology were addressed. The factors studied include cobalt concentration, initial pH of solution, temperature and time for the reaction, the charge amount of urea, and the temperature for decomposition. It is determined that the precursor particle is in the chemical composition of Co2(OH)3Cl with fine crystalline. By calcinations under proper conditions, the mono-dispersed cobalt oxide particles were prepared with fine crystalline, about 2 µ m in particle size and regular shape in morphology.

Jan 1, 2006

By Roozbeh Afzali

Designing an appropriate tunnel blasting pattern reduces the cost of rock breakage and subsequent operations such as loading, haulage and support of tunnels. For that reason, we developed a software that designs tunnel blasting patterns. Using this software, three different tunnel blast design models based on parallel hole cut, namely, Swedish, Konya and Energy Balance, were investigated and compared for a virtual tunnel. Accordingly, blasting patterns were designed, for different cross sections. The trend of parameters such as specific charge and specific drilling as functions of tunnel cross-section was determined for each model. Our results show that, in general, The Swedish model gives lower specific charge and specific drilling compared to other models.

Jan 1, 2008

By D. Su

This paper presents the details and results of a preliminary investigation into the response of borehole pressure cells (BPCs) in soft coal. Two parallel approaches, laboratory calibration and nonlinear finite element simulation, were adopted for deter- mining the BPC K-factor, which was defined as the ratio of cell pressure change to the corresponding change in external pressure. Results from both the laboratory calibration and the nonlinear finite element simulation revealed a nonlinear response of cell internal fluid pressure to external loading. The K-fact& also is shown to increase with increasing setting pressure and decreasing medium modulus. -Depending on the setting pressure, the K-factor for coal having a Young's modulus of 1.6 x lo5 psi ranges from nearly 1.2 at 2,000 psi of external pressure to 1.485 at 8,400 psi of external pressure. The improved under- standing of BPC behavior leads to the more accurate calculation of BPC K-factor in coal which significantly improves the correlation between pillar pressures measured in underground coal mines and those predicted by nonlinear finite element simulations of these pillars.

Jan 1, 1990

By Himanshu Dehra

The pre-fabricated outdoor rooms are often utilised near the mines and construction sites for office purposes. The paper has presented modelling and simulation results of the integration of commercially available glass coated photovoltaic (PV) energy technology and solar ventilation technology into a pre-fabricated outdoor room. The pre-fabricated outdoor room has been setup at Concordia University, Montréal for full scale testing of the glass coated PV modules with solar air ventilation. The computer simulation model has been developed for PV modules installed on a double wall wooden frame in an outdoor room based on its preliminary field testing. The testing apparatus was a wooden frame assembly of double wall with solar air ventilation: two adjacent glass coated PV modules, air column and plywood board filled with polystyrene. The measurement data collected from various sensors were: solar intensity, ambient air temperature, room air temperature, electric power, surface temperatures of PV modules and plywood board, air velocities and air temperatures in the air column. The enhancement in the air velocity of the air column was achieved with an exhaust fan fixed in an outdoor room. The simulation model is used to perform the two dimensional energy analyses with applied one dimensional solution of steady state heat conduction equations. The simulation model is based on conjugate heat exchange paths with network boundary conditions of convection, radiation heat exchange and solar air ventilation heat transport. The model parameters are based on measured values of ambient air temperature, room air temperature, air velocity at outlet of air column in double wall, electric power and available solar intensity. The model has predicted fairly well energy performance of glass coated PV modules with solar air ventilation installed on a wooden frame. The model is also useful for predicting heating, ventilating and air-conditioning (HVAC) requirements for the pre-fabricated outdoor rooms.

May 1, 2007

By A. P. Squelch

The question of what stress condition exists in the hangingwall of tabular stopes remains topical and largely unanswered. Limited field data exist to quantify the situation and provide calibration for investigative computer modelling exercises. Work conducted in1989 and 1990 under a Chamber of Mines Research Organization (now the CSIR: Division of Mining Technology) programme of research into the behaviour and benefits of backfill may assist with this situation. The original work was motivated by the premise that the improved hangingwall stability in backfilled panels (identified by rockfall accident analyses) is due to a change in the hangingwall stress regime. Current, largely theoretical, studies into mechanisms of stope hangingwall behaviour and support interaction could benefit from considering these data. Keywords: Backfill, horizontal stress, stope hangingwall, hangingwall stability, support interaction.

Jan 1, 2002

By Francisco Cabrejos

"El acopio de minerales a granel en pilas genera una forma de almacenamiento segura para grandes cantidades de minerales chancados gruesos o finos. En este sentido, el principal objetivo de los stockpiles es proveer una capacidad pulmón entre la mina y la planta de chancado, y asegurar un flujo de alimentación contínua, uniforme y controlada a los equipos aguas-abajo. Por ello, el presente trabajo describe el diseño y operación de los stockpiles en algunos yacimientos de Chile y Perú. El primer paso para el correcto dimensionamiento de un stockpile y su respectivo sistema de extracción de material, es determinar las propiedades de fluidez del mineral manejado bajo condiciones similares a las que será sometido el material en la mina, una vez que entre en funcionamiento el proyecto. Asimismo, se recomienda realizar ensayos de fluidez a varias muestras representativasdel mineral, las cuales deben ser cuidadosamente seleccionadas para que representen fidedignamente las condiciones que se encontrarán en la mina durante su vida útil, de forma que sus resultados permiten un correcto diseño y dimensionamiento del stockpile y su sistema de extracción de mineral. "

Sep 13, 2001

By J. -G. Swanson

Dust control in longwall coal mining depends primarily on the prevention of dust at the source and secondarily on the suppression of airborne dust. One of the primary methods for the prevention of dust is the wetting of the coal face prior to extraction, which can be achieved with water spray systems installed on the shield supports. The spray droplets must travel across the airway to the longwall face, where high ventilation air speeds can entrain water droplets and prevent them from reaching the face thus minimizing the dust control at the source. Through an evaluation of spray plume characteristics in a wind tunnel, the droplet size and droplet drift behavior was determined. This drift behavior was examined by evaluating the spray plume concentration drop and the droplet size shift near the nozzle exit at varying air speeds. Based on these evaluations, CFD modeling was applied to simulate the spray behavior for varying geometries. These results led to the selection of appropriate spray nozzles capable of carrying water droplets to the face at higher air speeds, resulting in an adequate wetting of the coal face and reduced dust generation.

Jan 1, 2012

By M. Abdellatif

The production of a 40% Al-Ti alloy was successfully proven at the lab scale, using pure TiO2, aluminium, and lime. These tests were conducted in an induction furnace maintained at 1600?16250C. The introduction of rutile into the feed recipe resulted in an alloy containing between 0.35 and 1.10% Zr, depending on rutile to TiO2 ratio. DC arc production of the alloy was largely accomplished at 40 and then 200kW scale. These tests evaluated various metallurgical and operational factors including target slag composition, Ti-content in the alloy, co-feeding versus sequential, furnace bath depth, and rutile as part of the Ti containing feedstock. Overall, an alloy containing 24?33% Ti was consistently produced with co-feeding of the reactants and with lower taphole tapping. When rutile was added, the zirconium analysis in the alloy remained below 0.2%. The main impurity elements were iron, silicon, carbon, nitrogen, and oxygen.

Jan 1, 2009

By Wern-ping Chen, Jean Habimana, Jinyuan Liu, Mirza M. Rabbaig, Robert Barbour

To mitigate and control the combined sewer overflows from 17 outfalls in the City of Detroit, three outfalls in Dearborn Heights and eight outfalls in Redford Township, the Detroit Water and Sewerage Department has completed the preliminary design of a storage tunnel in 2005. In 2006, a final design has revised the alignments and the inside diameter (ID) of the tunnel. The revised tunnel system includes an 11.28-km(7-miles) 9.14-m (30-ft) ID tunnel, a 24.4-m (80-ft) ID pump station, two work shafts about 15.2-m (50-ft) ID each, and 14 drop shafts with various IDs. This paper discusses the latest development of this tunnel system.

Jan 1, 2007

By George A. Savanick

The objective of this research is to develop a method for measuring the tensile strength at the interface between minerals in rock. These measurements reflect the strength of the attractive forces operating at crystalline interfaces in rock. Since these forces act in opposition to the forces set up in various rock fragmentation processes, measuring their strength may help in designing more efficient methods of rock fragmentation. The method developed for measuring the strength of intergranular adhesion in rock involves separating a bicrystal from the rock and determining the tensile strength at its solid-solid interface. This technique has been successfully applied to the study of quartz-feldspar interfaces separated from massive pegmatites, graphic granite, and the Rockville granite, yielding average tensile strengths of 5.86, 8.62, and 10.65 meganewtons per meter squared (MN/m2) (850, 1,250, and 1,524 psi, respectively). The data this technique provides indicate that the members of these bicrystals are strongly adherent. Examirtation of bicrystals broken at the crystalline interfaces indicates that the bonds responsible for this adhesion operate over only a portion of the interfacial area. This work conclusively demonstrates that tensile strength tests can be conducted on small selected areas; for example, grain boundaries in rock. The small-scale zones of strength or weakness determined in this way can be related to the overall strength of the rock.

Jan 1, 1972

By Andrew K. hg` Officer, A. L. Griffiths, J. Andrew Hindmarch, Gert Wittneben

Durban Harbour in South Africa is one of the continent’s busiest ports however the harbor entrance is currently too small for the new generation of container ships. There-fore it is to be deepened and widened by the National Ports Authority in the near future. An existing immersed tube tunnel carrying major sewer, water and other utilities under the harbor first needs to be removed and replaced by a deeper 4.4 m ID ser-vices tunnel. Construction of the deeper tunnel saw the first use of a slurry machine in South Africa and was required to negotiate grades up to 20%.

Jan 1, 2007