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By Terry Medhurst

Geophysical logging is routinely undertaken as part of most Australian coal mining exploration programs. Typically, the main application is the determination of coal seam depth and the qualitative estimation of coal quality, lithology and rock strength. For rock strength estimation, sonic transit times relate to the elastic properties of the rock and provide a general correlation with uniaxial compressive strength. However, experience has shown that site-specific relationships are necessary to account for different geological environments. In this paper we describe results from a series of recent studies that have provided a more comprehensive method of geotechnical strata characterisation using detailed lithological interpretation and rock property estimation from borehole logs. This has resulted in an improved method of estimating rock strength via the determination of the proportions of quartz and clay plus the porosity. We also propose a rock classification scheme based on geophysical log analysis. This builds on the existing acceptance of the sonic log as an indicator of rock strength and adds scores according to the moisture, cohesion, porosity and quartz content inferred from the geophysical logs. The new scheme can be related to existing mapping based schemes such as CMRR and the Q-system.

Jan 1, 2005

By T Medhurst

Recent developments in geophysical borehole log analysis using the Geophysical Strata Rating (GSR) are now routinely used in a number Australian coal mining operations. This allows development of 3D geotechnical strata characterisation models for a range of purposes. The availability of this data provides a means to identify relationships between ground conditions and ground behaviour. As a result, several new design methods have been developed to assist in the strata management process such as roof support, longwall shield design and shaft stability assessment. This paper outlines these methods and provides examples of their application. CITATION:Medhurst, T, 2018. Geotechnical strata characterisation using geophysics and its application for coal mine design, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 420–433 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By Clinton Strachan, Rob Dorey

10.1 INTRODUCTION This chapter presents considerations which should be applied to heap leach pad site selection, site evaluation, and design, relative to the geotechnics of the site and ore. 10.1.1 General Guidelines are presented covering the topics encountered in design and construction of heap leach faci1ities. Because geotechnical characteristics vary from site to site, not all geotechnical topics associated with a specific heap leach facility are presented, and there may be exceptions to some of these guidelines. The general features of a heap leach facility (from Chapter 1) to be discussed in this chapter are: • Leach pad (including leach pad foundation and liner); • Heap; • Solution storage faci1ities (for pregnant and barren process solutions) ; and • Solution collection facilities (which collect and convey solutions in the heap and convey them to solution storage facilities). These general features are illustrated in Figure 10.1. Liners for these facilities are discussed in Chapter 11. Solution application systems and the sizing aspects of solution storage facilities are discussed in Chapters 6, 7, and 12. The general features listed above are constructed with and overlie naturally occurring materials (such as ore, borrow soils, and subsurface soils and rock). These natural materials are relied upon to perform in an acceptable manner as a component of the leach facility (such as the liner, drain material, and foundation).

Jan 1, 1988

Recent operating experience from West Australian open pit gold mines has shown that geotechnical input into initial design is rare. As a result, ground stability is poor - almost half the pits designed in this way suffer major failure.West Australian experience shows that geotechnical studies for individual mines are site specific, and therefore empirical experience cannot be transported from site to site. Geotechnical studies performed prior to design have resulted in significantly improved pit stability.

Jan 1, 1990

By Fabio Amaya, Andrés Marulanda, Ramiro Gutiérrez, Alberto Marulanda

The behavior of a salt rock mass is strongly related to a creep phenomenon. The amount of creep depends on the level of stress generated in the underground excavation. Additionally, security conditions and the lifespan of an underground cavern excavated under this geological conditions depend on the evolution of creep. Based on the experience of the failure of the Old Underground Salt Cathedral of Zipaquirá(Colombia) and the construction of the new one, the theoretical framework to predict the creep behavior of a salt rock mass is explained. The theoretical formulations are calibrated based on actual observations of the material behavior to predict the lifespan of this striking structure.

Jan 1, 2003

By M. B. Haggerty, R. J. Sheets, F. Abbasy

To address coal refuse tailings storage needs for a mine operation in western Canada, a feasible solution was to convert excavated open pits into tailings cells. A slope stability investigation and design study were completed to determine the necessary width and slope geometry for in-situ native plugs as the impoundment embankment. The native plugs separate the previous open pit from the current active open pit. This configuration allows for the deposition of refuse tailings in the previous pit while allowing mining to safely continue “downstream” of the temporary impoundment. As mining progresses, each subsequent pit will be filled with refuse tailings; thereby, buttressing the upstream slope of the previous native plug. Although these cells are excavated, and the timeframe for downstream exposure is relatively limited, the native plugs are classified as dams and must be designed to meet applicable safety of dam standards since they impound water and tails above mining personnel in the subsequent open pit. The presentation and paper will discuss the investigation and analysis conducted to develop the geotechnical and hydrogeological design recommendations.

Mar 2, 2022

By David E. Thompson, Daniel J. Dobbels

INTRODUCTION The planning process for projects requiring construction of tunnels in urban environments can be highly complex and involves interaction with professionals of many disciplines. Typically the initial step in the planning process is to establish basic design criteria for the tunnel or tunnel system consistent with its intended purpose. Such criteria might include acceptable tunnel geometry, minimum and maximum slope or other associated criteria. Ideally, once the basic criteria have been established, the next step in the process might include establishing technically feasible horizontal and vertical alignment and shaft siting alternatives and developing "ball park" construction and operational cost estimates for the alternatives. Comparisons can then be made regarding the relative technical and economic merits of the alternatives and the most favorable alignment(s) are selected for further study or preliminary design. Typically the last and perhaps the most important task that is conducted during the planning stage includes identifying issues and potential problems to be addressed during the design and construction stages of the project. Many issues warrant consideration during the planning phase of a tunneling project. For the purposes of this paper, these issues can be divided into two broad categories: technical and non-technical. Important technical issues include, among others, general design criteria, geotechnical and geoenvironmental issues, and constructibility issues. Important non-technical issues include, among others, right-of-way and easement related considerations, project scheduling constraints, both short and long term environmental impacts and overall cost/benefit aspects of the project. With respect to influence on the planning process, these two groups of issues often cannot be separated completely. For urban tunneling projects, however, it is most often the case that the non-technical

Jan 1, 1991

By Luis Maldonado

El presente trabajo señala el desarrollo y aporte de la geotecnia en la minería subterránea, particularmente de la mina Ares, así como define algunos conceptos importantes empleados para determinar los diferentes tipos de refuerzo y/ o sostenimiento utilizados.También evalúa la estabilidad de las labores subterráneas y la elección de un sostenimiento apropiado por zonas delimitadas en los planos geotécnicos. En ese sentido, para la sistematización, cuantificación y calificación de las características geomecánicas de los macizos rocosos, se evalúa las propiedades del macizo como la combinación entre las características de las rocas y sus discontinuidades. De forma que se pueda determinar una cuantificación geomecánica que dilucide el sostenimiento y el método de excavación en base a la más adecuada clasificación requerida.

Sep 13, 2001

A new classification of subduction related (epithermal- / mesother-mal) gold mineralisation styles based on the tectonic framework they occur in, has been found helpful in practice. It offers a ratio-nalisation of exploration efforts during all stages of work.Methodology on the ground during first pass- and follow up explo-ration which has been found effective for the various mineralisa-tion styles is being briefly outlined.

Jan 1, 1990

Modern plate tectonic reconstruction of Mexico and Central America shows that the southeast-extend ing Precambrian backbone of Mexico, together with the east-flanking accreeted Huastecan (Appalachian-Caledonian) orogenic belt, are geotectonic elements practically absent in Central America, except west-ern and northern Guatemala and Belize, and contrib-uted little to the mineral potential of the entire region.The gradual accretion of the Cordilleran oro-genic belt took place against the western-south-western margin of the Precambrian backbone, and its consolidation required several tectonic events from the medial(?) Paleozoic to the end of the Mesozoic. The striking features of this "long-lived" orogenic belt are the massive sulphide min-eralization in the upper Paleozoic eugeoclinal as-semblage, the widespread gold occurrence in quartz veins in the lower Mesozoic volcanics and related intrusives, the carbonate-hosted silver-bearing lead-zince deposits of the Mississippi Valley-type (or Pine Point-type) around carbonate banks within the Lower Cretaceous back-arc miogeocline, that de-veloped over the Precambrian backbone and deeply-eroded Huastecan orogenic belt, the massive sul-phide (Pb-Zn) deposits in the Upper Jurassic-Lower Cretaceous sequence, transitional from miogeocline to eugeocline, which carry high grades in silver, and the iron deposits in this transitional facies, which are described in the literature as related to dioritic intrusives of Late Cretaceous age. Central America, south and southeast of the Mota-gua-Polochic fault system, forms part of the in-ternal zones of this orogenic belt.

Jan 1, 1990

The Ida Valley in Central Otago is one of series of parallel basins filled with freshwater sediments. The basins are in fact tectonic depressions superimposed on NE trending grabenlike structures which occur in the area and are the result of block faulting possibly initiated in Cretaceous times and concluded in late Tertiary and early Quaternary. In Central Otago this tectonic event affected metamorphosed rocks belonging to the eastern facies of the New Zealand Geosyncline and collectively known as the Haast Schist Group. These rocks constitute the basement and the shoulders of the tectonic depressions. The Ida Valley occupies the depression wedged in between the Raggedy Range to the NW and the North Rough Ridge in the SE. The valley is approximately 38 km long, 3 to 7.5 km wide and is drained by the NE flowing Pool Burn, which meets the SW flowing Ida Burn. The resulting unified stream flows into the Manuherikia river which drains the next door depression to the NW. The present work deals with the Ida Valley basin and more specifically with the geology studied within two Prospecting Licence areas held by Gold Mines of NZ Ltd on the southeastern flank of the valley.

Jan 1, 1977

By Charles E. Michener

This paper deals with the occurrence of basic and ultrabasic rocks and their relationship in space and time to major structures of the earth. In order to introduce the paper properly, I must go back a little and try to put the subject in perspective. In the brief time that geology has been a scientific occupation, ore deposits have been grouped and classified in various ways depending on the theories that happened to be popular at the time. Some of the early scientists said that ore came from fire, other schools argued that ore originated from water. Then came the lateral secretionists and in later years the hydrothermalists led by the Lindgren school and the latter has largely been accepted as the modern concept of ore deposits. It now seems apparent that the hydrothermal school is being seriously challenged by other schools of thought. It also seems that we have reached the point where we should be willing to admit that we do not really know in most cases how the ore got to its present position. However, for practical purposes, we can classify ore deposits as to the environment in which they do occur. This is not difficult and gives the field geologist and the mining engineer something to work with and to believe in, and it gives them a basis for carrying out their field work. On the screen, Figure 1, there is a classification of ore deposits based on the environment. Under each classification is listed the more prominent metals which are characteristic of that

Jan 1, 1971

By Marc Raithel, Sven Schröer, Lilma Schimmel, Dimiter Alexiew

"The Geotextile Encased Columns (GEC) deep foundation system for embankments and dikes on soft soils was introduced some 20 years ago and is now considered State-of-the-art in Germany, Europe and, step by step, worldwide. The GECs consist of compacted non-cohesive granular fill similar e.g. to common gravel columns with one decisive difference: they are confined in a high-strength, high-modulus, flexible geotextile “cylinder” (encasement). This engineered element with parameters being adaptable in a wide range provides a decisive tool to control and optimize the behavior of the GEC foundation system. Consequently, the GECs work properly even in extremely soft soils, and a wide range of fills inclusive of sands can be used. In the meantime vast design and technological experience is available and codified design methods exist. Initially the paper briefly describes the general idea, the basics and specifics of design, construction technology, materials, restrictions and optimal application areas. Then it focuses on three informative case studies. They are briefly presented focusing for brevity only on the most important facts and experience inclusive of the most meaningful data of short- and long-term measurement programs.INTRODUCTIONWhen considering embankments on soft soils, generally two groups of solutions exist:Unsupported embankments; there are four main options:a) build up embankment extremely slowly waiting for sufficient consolidation after every stage;b) replace the soft soil partially or totally;c) install a high-strength basal reinforcement providing overall and local stability and allowing much faster embankment construction;d) combine c) with strip drains to accelerate consolidation and thus the construction process additionally (Fig. 1, left).Today, practically only option ""d"" is of practical relevance. Despite all the pros and cons, the common attribute of all non-supported options is that local and overall stability (Ultimate Limit State-ULS) can be achieved and controlled, but not the short- and long-term settlements (Serviceability Limit State-SLS). The latter can be significant, e.g. up to 30% of the nominal planned embankment height. Supported embankments (Fig. 1, right): the main common idea is to over-bridge the soft soil layers by supporting vertical elements of different types: rigid piles, trench walls etc. or by ""softer"" solutions of different column types (compacted, cemented, mixed-in-place etc.). Herein the borderlines between “piles”, ""pile-similar elements"" and ""soil improvement” are fluent and depend on country, traditions, codes etc. The common attribute of the “supported” schemes is a minimized settlement. Twenty years ago a new specific solution was launched: the Geotextile Encased Columns (GEC), which is discussed in more detail below."

Jan 1, 2017

By Mark C. L. Patterson

Hydrothermal brines are extracted from significant depths below the surface of the earth and arrive at the surface at elevated pressure and temperature. The exact chemistry and conditions of these brines depends upon the rock formations through which the water travels, but many of the brines are rich in dissolved minerals especially silica which is often saturated in the brine. At pressure and temperature the minerals remain in solution but in order to extract heat from the brines, they need to be cooled and during which many of the minerals precipitate causing problems. Where precipitation is a problem in the downstream processing, the brines are maintained at a high enough temperature and pressure so as to avoid precipitation and injected back into the geothermal formation. This results in a significant loss in potential energy that could be recovered from the geothermal brines. If left to precipitate in an uncontrolled manner, many of the minerals will precipitate as gels, in a high surface area form which is difficult to extract from the liquor and which can causes problems. Precipitation in this manner often builds up on the inside of pipes, reducing the pipe cross-section available for fluid flow and reducing the overall efficiency of the plant. If the brines are seeded at the appropriate time or the precipitation conditions are changed, mineral particles can be grown and separated more easily from the brine. During this precipitation and growth phase the chemistry of the local environment can also be altered to grow more valuable particulates. Some of the specific chemistries will be discussed with reference to known geothermal brines and what needs to be done to precipitate value added products. A theoretical approach to the complete extraction of minerals from geothermal brines is also discussed with the goal of extracting more heat from the brine prior to reinjection into the well.

Jan 1, 2006

By G. I. Karydakis

Geothermal energy is an important energy asset which can play a significant role in providing energy resources to cover energy needs of a country while it can play a primary role in a particular region where it is abundant. Greece is especially rich in geothermal energy. The collision of Euroasiatic and African plates coupled with the strong tectonic tension, particularly in north Greece, resulted in the formation of important geothermal fields of low, medium and high enthalpy. These fields are in the Aegean islands, in central and east Macedonia, in Thrace and in central Greece. This work presents and analyzes information about the drilling activity for exploration and production of geothermal fields of low, medium and high enthalpy in Greece for the past thirty years. The number and type of wells drilled together with the spatial and the yearly distribution are given. Depth data has been analyzed according to the fluid temperatures and to the geological formations. Cost data are presented and analyzed for the total number of wells drilled giving also the cost per meter drilled.

Jan 1, 2006

By Anthony J. Chasteen

Although geothermal energy has been used by mankind for thousands of years and has even been used to generate electricity since the turn of the century, it is only in the last few years that the threatened energy crisis has focused attention on this resource. Geothermal exploration and development is being carried out in at least thirty-five countries on five continents. The status of geothermal energy production, however, is rudimentary with about 800 MW installed generating capacity worldwide, equal to about 0.1% of the world's total energy production.' The world's first (1904) commercial generating site at Lardarello, Italy, will soon be surpassed by developments at The Geysers, Calif. There are other successfully operating geothermal power projects in New Zealand, Japan, USSR, Mexico and Iceland with pilot plants planned or under construction in Chile, El Salvador, Nicaragua, Turkey and the Philippines. The preponderance of exploration and development is being sponsored or assisted by individual governments, by the UN or by the U.S. Agency for International Development

Jan 10, 1972

By F K. R Klose

Malmberget is a sublevel caving mine owned and operated by Luossavaara-Kiirunavaara Aktiebolag (LKAB), a Swedish state-owned iron ore mining company, in northern Sweden. The mine has an annual iron ore production of approximately 15 Mtpa. The current strategy foresees an expansion which will increase the mine’s depth considerably. Ventilation and air conditioning modelling for the planned expansion is ongoing. One of the most influential parameters for ventilation planning anddesign for a deep mine is geothermal gradient, which is crucial for the design of the refrigeration system. It is determined through virgin rock temperature (VRT) measurements carried out at various depth below the surface. This paper details these measurements and the determination of geothermal gradient for Malmberget Mine for the expansion study, which were necessitated by thelack of information for the focus depth and area.

Oct 12, 2022

By J. N. Munro

At the present stage of geothermal technology and the still limited applications of geothermal energy, most of us consider any use of "things geothermal" to be something out of the ordinary. If in such a situation there can be a use of geothermal energy which is even more unusual, then the utilization of geothermal energy-or more precisely, geothermal heat--for the manufacture of salt is just such a use. This is the essence of investigations in the Fiji Islands, where experiments in the evaporation of seawater to product, salt have been conducted using geothermal heat emanating from the ground in an area of hot springs. The hot springs are located on the coast at Savusavu in a depression about GO ft wide. There are ten individual springs, but most of these are small and insignificant. The temperature of the water from these springs reaches 100°C.

Jan 9, 1964

By Herbert E. Hawkes

“For his Pioneering leadership in the science and technology of mineral exploration, especially in the development and world-wide application of geochemical methods as major exploration tools, and for his lecture ‘Geothermal Hydrogen’.”

Jan 1, 1981

By J. Michael Canty

Over 25 years of US research in Mineral Recovery from Geothermal Solutions have lead to few commercial applications. With the World Bank program in Kamchatka, Russia in September 2005 a step was taken to vitalize and coordinate the many efforts to advance economic mineral recovery systems worldwide. The US Department of Energy is helping to spur on the interest and research needed to realize the many benefits of extracting minerals from geothermal solutions. The excitement of recovery of minerals from geothermal brines has many positive angles. The economics of certain geothermal site is improved if a revenue is arrived from a sellable commodity with the geothermal power. The use of cleaner geothermal brines also improves the capable use of the brine before reinjection. We will review the history of Geothermal in the USA and the opportunities for recovery of different minerals and the markets for them.

Jan 1, 2006