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By Helmut Hass, Michael B. Gilbert

The extension of the commuter railway system (S-Bahn) in Leipzig, Germany willrequire the construction of an underground line crossing the downtown area of thecity to tie the Bavarian Station in the South to the Main-Station in the North. The City-Tunnel-Leipzig is currently one of the largest infrastructure projects in Europe. This system extension will have a length of approximately five kilometers. 3.9 kilometers of that length are currently being constructed using either cut & cover construction or tunnelingmethods. The design and construction of this project currently is and will continue facing very significant challenging urban and demanding geotechnical conditions.

Jan 1, 2007

By H. Yavuz

Closed form solutions assume opening shape to be circular to simplify the calculation of the ground response curve for the design of underground openings. However, in mining and civil engineering works, non-circular openings are commonly excavated. Therefore, there is a need to estimate the ground response curve for such openings. In this respect, a simple model for circular, arch and rectangular shape underground openings subject to a hydrostatic stress field is the aim of this study. A comprehensive numerical modelling, using the finite difference method, based on numerical modelling code FLAC version 4.0, was carried out. In addition to shape of an opening, the effect of rock mass strength, opening size, in situ stress on strain (tunnel deformation to tunnel radius) of the opening in response to applied support pressures was investigated parametrically by developing models for each specific condition. The strain results for each excavation shape obtained from this large number of models against the normalized strength of rock mass and internal support pressure with in situ stress magnitude were evaluated by multiple regression analysis. As a result, a model that was well correlated to data was developed for an overall estimate of the ground response curve depending on relevant effecting parameters. The regression coefficients of the model were given for estimating both roof and sidewall response curve of each excavation shape. The model was verified by statistical tests and by an analytical solution. Diagrams were also established to highlight the influence of relevant parameters and to estimate the support pressure for a stable opening staying within the acceptable limits of strain. Strains occurring in a rectangular opening are found to be larger than those in the arch and circular openings for the other fixed parameters. In the mean time, larger strains occur around an arch shape opening than a circular opening.

Jan 1, 2006

By Erdal Ünal

The computer program introduced in this paper is based on design guidelines developed for selection of support systems used in mine roadways. The support types considered include rock bolts as well as rigid and yieldable steel arches. Using the computer program, the design engineer can select the type, pattern and specifications of the support systems suitable for various roof conditions. The concepts utilized, assumptions made, support selection criteria and description of the computer program, developed for the PC, are included.

Jan 1, 1989

By X. Q. Cao, D. S. Zhang, L. Q. Ma

To solve the support stability control problem for a coal face with large angles along both strike and dip (CLSD), the ’support-surrounding rock’ mechanical model has been developed, which takes into account the impact of the dip angle of the seam on the stability of the support in the strike direction. The mechanical relationships of the critical topple angle and critical slip angle of the support along the strike of the coal face with large dip angle and the support height, support resistance, friction coefficient, and other factors have been derived through the mechanical analysis of support stability in the strike direction of CLSDs in the free state, the operating state, and the special state. The research findings were applied to a fully mechanized CLSD in Xinji Coal Mine. The maximum underhand angle and overhand angle in strike are 42° and 25° respectively, and the maximum dip is 39°. It is calculated that during underhand mining and overhand mining, the critical support resistances for avoiding support toppling are 3723 kN and 1714 kN respectively, and the critical support resistances for avoiding slipping of the support are 7405 kN and 6606 kN respectively. Thus, the selection of type ZZ7600/18/38 hydraulic roof support for the coal face is justified. Measures to prevent sliding of the support and the installation of a limiting stop maintain the support runs in good condition and ensure safe and efficient mining of CLSD.

Jan 1, 2015

This paper reports on recent field observations on the performance of support systems under different corrosion environments in Canadian underground mines. Phenomenological data are used to gain a better understanding of the main causes of corrosion in underground metal mines. Preliminary field data collected from five metal mines have been complemented by atmospheric and water sample analysis as well as fractography and metallographic studies. This has identified dominant factors that control the corrosion of support systems. The data are analysed in order to develop a support strategy for mines operating in corrosion environments.

Jan 1, 2008

By Eric R. Borys, Amaneh E. Kenarsari, Brett Gitskin

This case study discusses impacts of excessive Earth Retention System (ERS) lateral movement at a project in city of Chicago. The ERS (cantilevered sheeting) moved inward towards the excavation and caused lateral displacement and cracks in six drilled shafts located about 1 to 2 lateral feet (0.3 to 0.6 m) from the face of the sheet pile wall. Up to 9 inches (23 cm) of horizontal movement was observed on top of the supporting sheet-pile. Similarly, survey measurements showed the top of the drilled shafts moved laterally up to 8 inches (20.3 cm). To evaluate the cause of failure and determine a remediation solution, the soil, shaft and site conditions were investigated. Pile Integrity Tests (PIT) were conducted at the affected drilled shafts. The shafts with identified anomalies were cored and video-recorded. The cause of the failure was determined to be related to variable soil conditions across the site, deeper excavation (i.e., increased effective ERS wall height), and other differences between design and as-built conditions. Internal bracing, in the form of walers and rakers, was installed to limit further movement of the sheet pile as a short-term solution, with additional grade beams framed into the basement slab-on-grade as a long- term solution. Five of the six cracked shafts were spliced with reinforcing bars and high strength grout and one shaft was replaced. INTRODUCTION The subsoil in the Chicago Area mostly consists of glacial till clays underlain by water-bearing granular soil over bedrock. The glacial clays have very soft to medium consistencies for a typical thickness of 30 to 50 feet (9.1 to 15.2 m) below which hard clays (Hardpan, i.e., heavily over-consolidated clay soils) are encountered. The soft clays are often referred to as the “Chicago Blue Clay”. Beach Sands are also found above upper soft clays in several areas, especially within a three-mile strip near Lake Michigan (Peck and Reed 1954). Due to the existence of soft clay in Chicago area, supporting the mid to high rise buildings on drilled shafts extended to Hardpan is a common practice in modern building design. In the early 19th century it used to take about 3 weeks to excavate 1 shaft hole and about 1½ days to fill the shaft with concrete in Chicago (Manierre 1916). The early 19th century methodology of excavating a shaft consisted of hand digging the shaft, installing wood lagging as temporary shoring with spoils removed with a rope and pulley system from the surface. Today, the excavation of a typical drilled shaft in Chicago uses heavy drilling equipment and requires much less time for excavation and concrete placement. It is not uncommon for contractors to excavate shafts and place concrete at a rate of about 2 to 5 drilled shafts per day (with one drill rig).

Jan 1, 2018

By Tarrant Elkington

Underground mine planning practices are typically manual and time consuming and will often produce sub-optimal solutions due to the application of generic rule-of-thumb assumptions or ?tried and tested? choices. The development of computer-automated tools for underground mine planning enable a wide range of scenarios to be considered rapidly in arriving at an optimised solution, subject to input assumptions. We have applied these tools to demonstrate ?optimised? solutions that challenge industry standard practices. Further, we have incorporated grade and price/cost uncertainty into these tools to gain an understanding on how the consideration of uncertainty may further alter strategy selection. Finally, we enable the tools to dynamically adjust cut-off grades in conjunction with the evolution of prices/cost.

May 1, 2010

By Haruka Takeura, Tomoaki Murata, Kazunari Yoshida, Masato Adachi

"Pure magnesium is a material with high functionality, however, the cold drawing of this material is very difficult, that is why, until this day there are no optimal cold drawing conditions. Furthermore, cold drawing of pure magnesium wire shows a problem with internal defects that occurs under certain conditions. In this research, the aim is the suppression of internal defects, and final target is to create the optimal cold drawing conditions for pure magnesium wires. The first step is the investigation of the drawing limit by using 250°Cannealed wire. As a result, reduction of 10% per pass was chosen for stable wire drawing. However, in this case, it was found that internal defects occurred at total reduction of over 45% during drawing. Investigation of intermediate annealing conditions that can suppress internal defects, and influence on internal defect that the die half angle and reduction per pass. As a result, it was found that the drawing condition capable of suppressing internal defects most efficiently was 13% reduction drawing by using under 6°half angle die. Consequently, it’s possible to manufacture a cold fine drawn pure magnesium wire of 100µm, without defects in the center of the wire and hindering its mechanical properties.INTRODUCTIONMagnesium is a light and high functionality material that has high vibration absorbency, heat dissipation, electromagnetic wave-shielding and recycling efficiency (Conruy, 1989). However, proper cold wire drawing conditions haven’t been established, that is why warm or hot processing is commonly used (Oishi, Mori, &Kawabe, 2005). As a result, strength improvement of the wires is not possible, that is why the production of medical tools is disregarded. If it was possible to cold draw magnesium wires, the applications for material products would expand. Further, in wire drawing such difficult processing material, if appropriate processing conditions are not selected, defects will be generated inside the drawn wire."

Jan 1, 2017

By D. M. Sloan

While surety capacity for the mining industry continues to shrink, States are demanding greater financial certainty for closure/post closure obligations. To combat these demands, larger mining companies are pursuing a Mining Surety Reinsurance Program that requires a significant up front capital contribution. This paper outlines an alter-native program for middle market mining organizations. The program utilizes a “Blended Finite Risk” environmental insurance solution with surety acting as the “front” in states where insurance is not an acceptable form of collateral. Marsh proposes creating separate programs for each State requiring surety. The reason for separate programs stems from each states’ different surety rules. Insurance companies typically require at least $5 million in future value remediation liabilities for finite risk programs. Since most middle market mining companies have obligations that fall below this threshold, the Blended Finite Risk Program contemplates combining several companies closure/post closure liabilities to accomplish the minimum amount required by the insurance company. Why use a Blended Finite Risk Program? One of the primary benefits is the financial assurance that funds will be available for planned remediation. For example, the financial assurance may be required by a government agency. The certainty may help facilitate a merger or acquisition. Additionally, the funds may be part of a CER-CLA PRP settlement. In all cases, the insurer providing coverage would be a secure independent 3rd party. A Blended Finite Risk Program also provides a long-term solution – up to 30 years and in some select cases longer. The benefit to a state or the BLM is the removal of financial uncertainty. An insurance company writing the policy would have an AA or AAA balance sheet. The hardening of surety markets coupled with the tightening of financial assurance requirements in many states have necessitated the posting of 100% collateral. This program substantially reduces these collateral requirements.

Jan 1, 2004

Magnetic anomalies in the Southern Coalfields have been subdivided into two characteristic types. Each type is attributed to a separate cause, one being basement structure, and the other near-surface igneous intrusions.Detailed geological mapping of the area and the ability to sample throughout the coalmines greatly assisted in this subdivision.The Triassic sequence contributes no magnetic effect of its own except to diminish the effect of sources within the underlying formations by raising the level of observation.Detecting the presence of igneous intrusions ahead of colliery working faces by magnetic observations within the coal mines may be of value in preventing accidents caused by gas outbursts and in planning the workings so as to avoid loss of production time.

Jan 1, 1967

By M. J. Lukhele

Paper written on project work carried out in partial fulfilment of B. Tech (Mining Engineering) degree A number of high wall mining methods were developed over the years to mine coal reserves exposed on the high walls created during surface mining. The auger mining system was initially developed in the early 1940s in the United States of America. High wall mining is a method of recovering coal from seam exposed either by mechanical excavation methods or natural erosions. This is usually associated with strip-mining (opencast) where the stripping ratio is high and uneconomical to mine using the opencast mining method. This paper discusses the surface auger mining as deployed at Rietspruit Mine Services Proprietary Limited.

Jan 1, 2002

By S. Uddin

An integrated device has been developed to measure sedimentation potential, conductivity and pH simultaneously of particulate systems. Maxwell?s model was used to calculate volume fraction of solid from the conductivity data. In this approach, all system variables are known and zeta potential can be calculated from Smoluchowski?s equation. The technique is validated by comparing zeta potential vs. pH for alumina and silica suspensions with electrophoresis measurements. The technique was extended to mixed alumina/silica systems. Sufficient column height along with size difference between the two minerals allowed gravity fractionation during settling. Sedimentation potential measured over time identified the transition from one mineral to the next. Using XRD analysis the results supported the correlation between surface charge and sample composition. This is a step towards characterizing surface charge of mixed systems of interest in mineral processing.

Jan 1, 2010

By Taisuke Sakakibara, Shinya Suzuki, Tatsuya Kato, Chiharu Tokoro, Kenichi Muto

Surface complexation using a diffuse layer model were constructed for arsenic (As(V)), zinc (Zn(II)) and silicate (Si(IV)) for aluminum hydroxide in the co-precipitation process. From experimental investigations using isotherms, zeta potential measurement and XRD analysis, it was confirmed that co-precipitation involved not only surface complexation but also surface precipitation. However, surface complexation was major mechanism for As(V), Zn(II) and Si(IV) removal under the target removal level of the Japanese effluent standard. In surface complexation modeling, exchange capacity of aluminum hydroxide was determined from specific surface area obtained from experimental measurement and site density obtained from reference. Surface complexation coefficients were determined by fitting the removal property and sorption isotherm obtained from co-precipitation experiments. These parameters were in agreement with the numerical parameters found by Karamalidis and Dzombak (2010) who reported a database of adsorption equilibrium constants for gibbsite. The surface complexation models constructed in this study were applied to neutralization process of an actual AMD treatment. Our model could successfully represent the pH edges for As(V), Zn(II) and Si(IV) in the neutralization of AMD.

Jan 1, 2015

By P. M. Lin

A subsidence monitoring program over a longwall panel was established (1) to explore the impacts of dynamic subsidence on the ground surface and structures and (2) to correlate the movements between the structures and their corresponding points on the ground. The program consisted of a transverse line survey and a series of survey points around the structures on the ground surface and their corresponding survey points on the exterior walls of the structures. The vertical displacement of each point can be expressed as: where Si is subsidence at i point; Sif is the final subsidence at i point; F is face location in terms of distance from the i point and SD is seam depth. The development of subsidence can be divided into five stages. Damage to the structures starts at the beginning of the second stage, The maximum damage developed in the middle of the third stage. The relationship of the vertical displacement between ground surface and structures can be expressed as: G = aH + b where G is ground displacement, H is structures displacement, and a and b are constants. The relationship is linear. However, the strain is non-linear and more complicated because of the interaction of the ground surface and structure.

Jan 1, 1989

By Christopher J. Bise

INTRODUCTION The level of analysis for the selection of extraction practices and equipment for surface mining differs significantly from that found in underground mining. In underground mines, manufacturers establish the operating ranges of the equipment, such as continuous miners, loaders, and boring machines, based upon required clearances. Even in conventional mining, the drilling and blasting operation is usually based upon experience. The selection of extraction methods and equipment for surface mining is more complex. Since the equipment is not as confined as in deep mining, and the topography tends to be highly variable over the limits of the mining property, primary extraction equipment must be sized according to reach and capacity. Further, due to the depositional characteristics of the over- burden, drilling and blasting patterns must be well- designed to provide proper fragmentation. The following sections provide a general outline for the selection of surface excavation practices and equipment. The topics covered include drilling and blasting and the selection of both primary extraction equipment (draglines and stripping shovels) and secondary extraction equipment (bulldozers, scrapers, and front-end loaders). EXCAVATION FUNDAMENTALS Before discussing surface excavation, a few concepts need to be defined. A bank cubic yard of material is equal to one cubic yard as it lies in its natural or undisturbed state. A loose cubic yard is that portion of a bank yard that after being disturbed has expanded to measure one cubic yard. Swell is the volume increase of a material when it is removed from the natural state. Finally, load factor is the percentage decrease in the density of a material from its natural state to a loose state. Table 1 summarizes these concepts for various materials. When the amount of overburden to be removed to meet a predetermined production rate is established, a suitable bucket size for the primary stripping equipment must be calculated. The following equation can be used: NBSIZE = TBC/[(OF) (BF)] (1) where NBSIZE is the actual bucket capacity after considering the swell percentage, the bucket fill factor, and the operating efficiency; TBC is the theoretical bucket capacity (TBC = COB/NTCPM); OF is the operating efficiency; BF is the bucket fill factor; COB is the cubic yards of overburden to be removed; NTCPM is the number of theoretical cycles per month [NTCPM = (SMH) (3600)/(CT)]; SMH is the scheduled monthly hours; and CT is the cycle time in seconds. FRAGMENTATION PROCEDURES Drilling Where the strength of overburden material is such that blasting is required prior to excavation, drilling is conducted before using explosives. Two methods of drilling are found in mining-percussion and rotary. Penetration of overburden by percussion drilling is carried out by successive impacts of the bit into the rock. Emphasis in this section will be placed on rotary drilling, because for surface mining it is the most versatile form of overburden penetration. Rotary drilling is conducted by rotating a rigid string of tubular rods to which a rock-cutting bit is attached. The drilling energy is supplied by rotation as well as thrust and the cutting action consists of abrasion, scraping, spalling, or chipping. The size range for rotary-drilled blastholes is from 4 in. to 15 in., with 9 in. and 12 in. being common sizes. There are two types of bits used for rotary drilling-drag and rolling cutter. Drag bits are applicable in soft to medium-soft shales or their equivalents. Since their effectiveness is dependent upon a successful scraping action, drilling thrust is lower for drag bits than for rolling cutter bits; the opposite is true for torque requirements. The bits are usually fitted with replace- able tungsten-carbide cutters. Rolling cutter bits, though available in a two-cone configuration, are usually of the three-cone style (Table 2). The rolling cones have either large steel teeth for drilling through soft formations or small tungsten-car- bide inserts for drilling through hard formations. Table 3 relates bit size and weight to the strength of the rock. The major advantage of rotary drilling is its rapid drilling rate. This is due to the fact that, unlike percussion drilling, rock penetration is uniform with depth. Blasting Effective bank preparation deals not only with the fragmentation of overburden but also with the mini-

Jan 1, 1986

By Daniel P. Lathrop, Leslie C. Taylor, William L. Fourney

Except when the target is on the surface, e.g. a tank track, the most important loading mechanism from a buried charge on a target above it is the impact of soil propelled at the target by the expanding gas from the explosion. Detonation of a shallow buried explosive generally yields an unstable interface between the rising soil and the air which appears to be the result of Richtmyer-Meshkov instability. Irregular “fingers” of saturated sand extend into the air above a more generalized dome of soil. These fingers move at a much higher velocity than the material between them at smaller stand off distances. As a result, the local load on the target at positions on the target at the same distance from the charge may vary by 50% or more from shot to shot or even within a single shot. This variation requires a large design safety factor to assure the integrity of design of mine-resistant vehicles.

Jan 1, 2009

By William A. Hustrulid

The subject of surface mine development is large. This section covers the fundamental concepts involved in both the open pit mining of thick or steeply dipping deposits as well as the strip mining of thin, shallow, and relatively flat-lying seams or beds. Design involves the marrying of geometries, ore and waste characteristics, equipment, and economics so that the desired result is achieved. Generally, there are many possible combinations from which to choose. For example, extraction over a short time period requires one strategy while quite another is applied for longer times. Variations in supply and demand require some flexibility of operation. Customer requirements impose certain constraints regarding the set of possible designs. Over recent years, planning and operating considerations for surface mining imposed by environmental requirements have increased markedly. There have, at the same time, been enormous advances made in the design aids available to the mine planner. Computer simulation of the various options, whether it be for mine design or equipment selection, provides detailed information for decision making in real time. A significant challenge to the engineer/planner is how to best use the aids avail-able. Because of the widespread use of commercially available and in-house computer software by industry, this section does not deal with the details of planning (for basic coverage of mine development, see Section 7). Rather, some of the basic concepts are stressed. The principles involved in equipment sizing and selection are discussed. A highly important but sometimes over-looked aspect of planning, haul road design, is also covered. For surface mining operations of the future, in-pit crushing and conveying will become even more important. Some of the considerations for application evaluation are included. The section concludes with some future concepts for surface mining.

Jan 1, 2008

By Steven J. Page, Andrew B. Cecala, John A. Organiscak

In This Chapter [Drill dust control: wet and dry Enclosed cabs on drills and mobile equipment Haul road dust control] Overburden drilling generates most of the respirable dust that affects workers at surface mines. Both wet and dry methods are available to reduce this drill dust. Overburden removal by mobile excavation equipment such as bulldozers, front-end loaders, and haulage trucks can be dusty, particularly under dry and windy conditions. Tightly enclosed cabs with dust filtration systems can substantially lower the dust exposure of both drill and mobile equipment operators. Haul road dust control can be achieved by water application or chemical application. DRILL DUST CONTROL [Drill dust is controlled with wet or dry systems. Wet systems can be more efficient, but may freeze in the winter. Dry systems require careful maintenance of the drill deck shroud. An improved deck shroud is shown.] Wet Suppression. Wet drilling systems pump water into the bailing air from a water tank mounted on the drill. The water droplets in the bailing air trap dust particles as they travel up the annular space of the drilled hole, thus controlling dust as the air bails the cuttings from the hole [Page 1991]. In wet drilling systems, typical water flow rates are 0.1 to 2.0 gpm depending on the size and type of drill and the moisture level of the overburden. The drill operator controls the flow using a control valve located in the cab. Some drills are equipped with a flow meter to give the opera-tor a visual sign of the flow rate. Raising the water flow will improve dust capture, but too much water causes operational problems. Because of this, the drill operator must exercise care in find-ing the best water flow rate.

Jan 6, 2003

By Tegner C. Johnson

Just a few years ago my company was referred to as the Marion Steam Shovel Company. We still make shovels, both two and eight crawler types. The eight crawler stripping shovel appears to have been replaced by the walking dragline for overburden removal and in some cases for the mineral as well. The walking dragline appeared in the coal fields in the early 1930's. It owes its popularity today to the fact that it can cope with overburden depths in excess of 100 feet and with blasted sedimentary rock, all at an 0 & 0 cost of ± 10¢/BCY.

Jan 1, 1974

By Irwin H. Reiss

Gentlemen, the title of my paper is Surface Mining An Interim Land Use. Surface mining has become one of the major controversies of our time. This has happened in spite of the fact that all surface mining to date has involved only 6 million acres out of a total of 2300 million or approximately one-fourth of one percent of the total land area in the United States. I'm not going to dwell on whether peoples' perspectives are out of focus in light of the area involved, the energy crisis, national security, or the international balance of payments problem. While these things are all critically important, it is not the function of this paper to relate to them. Maybe the amount of attention attracted to surface mining is out of proportion to a lot of other things, but I don't feel that we should use that as a basis for procrastination. However, let me categorically state that anything that affects the surface of the earth is a form of land use --- be it an interstate highway, a power plant site, a golf course, a corn field, a strip mine, or the plot of ground on which your house is located.

Jan 1, 1974