http://iye.savviihq.com/kenworth-pintura-de-manual-de-mquina.php In Australia the producers of quarried products are known collectively as the extractive industries. Geomaterials differ from other mineral commodities in many ways: their widespread, though uneven, distribution; the large volumetric demand for them, concentrated around urban areas; their low ex-pit value, because substitutes can always be found; and, consequently, their sensitivity to transport costs. Large and high-quality geomaterial deposits far from cities are worthless, while inferior materials close to customers are often upgraded.
The traditional task of geologists in this industry was to locate and prove up deposits meeting specified criteria within acceptable hauling distance of the construction site. With the increasing scale of quarry operations and rising public concern over landscape degradation, this role has expanded. Geologists are now generally part of a project team, in which they may be asked to give advice on the geological aspects of product quality control, blast design, crusher selection, quarry restoration and so on.
They will be expected to know enough about downstream processing to prepare a preliminary pit layout and to suggest how the properties of the raw material are likely to influence this. The geologist should certainly take these things into account when planning a quarry investigation, and attempt to map, sample and log drillholes with a wider view than simply evaluating quality and reserves.
At a later stage the person responsible for laboratory testing and quality control in a large quarry is also, more often than not, likely to have been originally trained as a geologist. McNally the site environmental officer—responsible for matters such as blast vibration monitoring, dust control and pit restoration. Big quarries offer economies of scale: a variety of products, more elaborate processing facilities, large reserves, continuity of operation and access to specialist skills.
These operations are better equipped, financially and technically, to meet increasingly stringent environmental and specification requirements, and to accommodate fluctuating market demand. There is a price to be paid for this producer concentration, of course: big quarries are more intrusive within a landscape than small ones; haulage to distant construction sites is more expensive; and price competition is diminished.
Maximum use of existing quarries The second development is towards maximum use of existing quarries, even where only inferior materials remain. This alluvial gravel pit near Urana, New South Wales, has been simply abandoned. Note that some natural revegetation has occurred, despite a poor soil and gully erosion. On a positive note, this quarry offers a wildlife refuge in an otherwise monotonous farmland plain, and is the only surface exposure of these Late Tertiary gravels in the State.
Greater use of upgraded materials The third trend, which is a corollary of the above, is greater use of upgraded marginal materials or simply non-standard materials, and even wastes to extend the life of the limited reserves of first-class rock. This can be achieved by blending, stabilization and careful quality control.
In effect, the trend is away from natural deposits that happen to have suitable properties, and towards materials that are processed or even manufactured to meet a specification. It is also desirable that a material not be overspecified, to a standard above what the end-use demands, because this is wasteful of resources.
Temporary land-use Finally, it is emphasized that quarrying is only a temporary use of the land, and that reclamation of mined-out land should be planned well before abandonment Figures 1. Because old quarries are commonly enveloped by urban growth, this may be self-financing in two ways: first, because the voids can be used as waste disposal sites; and, secondly, the land may be later Figure 1.
At this stage the ferricrete surface has just been exposed; topsoil and vegetation mulch are stockpiled on the left, thin subsoil overburden in the other two mounds. Low soil fertility and low rainfall inhibit site rehabilitation, and the shallow depth about 1. Usually the time interval between stripping and restoration is 6—12 months. McNally sold for industrial or other higher-value end-uses.
In other cases, restoration may be paid for by a levy on existing producers, who benefit from restrictions on competitors entering the market, before being returned to public ownership as recreational facilities. Emphasis is placed on methods of evaluating rather than searching for these materials, since in most cases their general location will be known beforehand. There appears to be a worldwide trend towards increased production from hard rock quarries at the expense of sand and gravel pits, partly because these are better suited to large-scale extraction and partly because they cause less environmental damage per tonne mined.
However, crushed rock sources are more likely to be weathered or altered, and hence to produce stone of suspect durability. They also require blasting, which increases extraction costs and creates vibration nuisances. Chapter 3 also discusses two important developing sources of sand and gravel—marine dredging, and weakly consolidated sandstone and conglomerate. These offer very large reserves, but present problems of salt content and fines disposal, respectively. Though formerly favoured because they occurred close to construction sites and required minimal processing, their use in this form is declining.
Instead, they are increasingly being upgraded by crushing and stabilization to meet heavier traffic requirements Figure 1. Chapters 5 and 6 discuss the extraction and processing of hard rock and granular materials. Processing is taken to include crushing, particle shaping, screening, sizing, beneficiation and de watering. These techniques—mostly borrowed from mineral processing—are becoming more important as premium sources are exhausted and inferior deposits have to be worked. The chief technical issues here are: in blasting, the replacement of nitroglycerine-based explosives by ANFO, watergels and, most recently, emulsions; in crushing, the wider use of impact crushers, even in moderately strong and abrasive rock, and especially for product shaping; and in sand workings, more extensive application of size classification techniques Figure 1.
Chapter 7 describes the testing and specification of aggregate and prepared roadbase. The principal categories of laboratory test methods, and their applicability, are summarized. McNally Figure 1. This is typical of duricrust road gravels still used with minimal processing in this case grid rolling, but elsewhere single-stage crushing for secondary road pavements. The coarse fragments in the foreground have been moved to the edge of the road shoulder during construction, and the roadbase material beneath the seal is somewhat finer. Another innovation has been the move from prescriptive specifications to ones based on quality assurance and more refined sampling techniques.
The use of coarse and fine aggregate in Portland cement concrete, asphaltic concrete and bituminous surfacing—and their differing requirements—are the subject of Chapters 8 and 9. In concrete aggregates Chapter 8 , intact rock strength is now thought to be less important than the tenacity of the cement-aggregate bond, especially where tensile strength is at a premium. In concrete mix design, there is now a wider acceptance of slag and fly ash as cement extenders and fillers, and not just because they are cheap.
In bituminous surfacing, asphaltic veneers are progressively displacing sprayed seals, and more emphasis is being placed on skid resistance, low tyre noise and fatigue life in mix designs. Earth embankment materials, compaction and road pavement design are discussed in Chapters 10 and In Australia at least, earthfill compaction standards have not improved over the past 30 years, though lift thicknesses and roller sizes have both doubled. A tailings pond allows process water to clarify before discharge to the Murray River just beyond top edge of photo.
The feed is very silty but well-graded Parilla Sand Pliocene. Modern deep cuttings produce less-weathered rock and hence a requirement that rockfill, with its attendant problem of settlement, be accepted in highway embankments. This in turn has dictated that a form of fill zoning be adopted to encompass common fill, select fill, transition zones and rockfill materials.
The double requirements of allowing for settlement of high fills and heavier traffic loadings have dictated that pavement thickness and stiffness be greatly increased in freeway-standard roads. This has been achieved partly by the wider use of crushed and bound roadbases, including deep lift asphalt, and partly through the re-introduction of concrete pavements.
The effects of cyclic loading, especially by heavy trucks, are now fully appreciated in road design, where pavement life is expressed in equivalent standard axles ESAs rather than years. Analytical design methods based on triaxial testing and numerical modelling are gradually supplanting the former empirical approach. Railway ballast, rockfill and macadam pavements are discussed in Chapter These are all open-graded, free-draining broken rock materials, but of different maximum particle size and durability. The solidity of the abutments is deceptive: the cladding slabs are simply slotted together and held in place by steel tendons embedded in the dune sand backfill.
This replaces strong end-dumped rockfill, which was sluiced but otherwise compacted under self-weight, resulting in large and long-term settlements.
Chapter 13 deals with the even coarser stone used in shoreline protection works. The main geotechnical challenge here is devising blasting procedures for generating armour blocks around 10 tonnes weight and zoning the breakwater to use this stone most effectively. Another problem lies in testing such unwieldy materials; ultrasonic velocity measurements appear to offer much potential. Rock cut and split for use as dimension stone is the topic of Chapter Dimension stone is experiencing a worldwide architectural revival, and indeed it is the only extractive industry with a significant export component, though facing stone has long displaced block masonry as the dominant application.
The use of stone veneers as thin as 20—40 mm in facing panels places considerable emphasis on flexural tensile strength and durability, favouring granites over sandstones or limestones. Another important development in this area has been the growth of the stonework preservation and restoration sector, and the emphasis on stone salvage and matching.
McNally construction materials. This is especially true of limestone, which, though a versatile source of aggregate, crushed roadbase, armourstone and dimension stone, is most valuable as a raw material in cement-making and other chemical processes. Carbonate rock terrains also give rise to unique landforms, soils and faunal assemblages—and therefore to a disproportionate share of environmental opposition to quarrying Figure 1.
The continued use of carbonate rock for aggregates, where other rock Figure 1. The kiln was built out of offcuts from Gambier Limestone used primarily as sawn dimension stone. McNally types would do as well or better, and of high-calcium limestone for cementmaking, is not easy to defend. In both applications the natural materials are heavily modified and blended, becoming less dependent on the source rock mineralogy and particle composition.
Environmental aspects of the construction-materials industry are the themes of the last five chapters. These include wastes, whose exploitation can both remove landscape eyesores and reduce pressure on natural resources. However, they are not equally prized: most are inhomogeneous and therefore only usable as common fill close to the dump site. By far the most valuable are iron and steel slags, which are today classified as byproducts rather than wastes and are produced to specification.
Indeed, blast furnace slag in granulated or pelletized form is more valuable as a cement extender or lightweight aggregate than as roadbase. Demolition materials crushed bricks, concrete masonry and asphalt pavements are now being widely recycled, partly in response to Government directives and partly as a means of avoiding tipping fees.
The upgrading of inferior pavement materials by means of granular or chemical stabilization is the subject of Chapter In the past, stabilization always performed better in the laboratory than on the road, but modern purpose-built equipment has improved the mixing consistency.
Cement and lime-fly ash pozzolans are the most common additives, though foamed bitumen is making a comeback. One important application is the in situ renovation of over-age natural gravel pavements, which in Australia alone could be needed for thousands of lane kilometres on rural highways over the next 20 years. Chapter 19 deals with the principal environmental problems of establishing new quarries, with particular emphasis on their geological justification—to counter the argument that, although the need has been established, a better site is available elsewhere.
Minimization of blasting nuisances Chapter 20 is an important issue during the working life of a quarry, especially since statutory limits for air and ground vibration are now being set far below damaging levels, to where the blast is scarcely noticeable. Ground vibrations are satisfactorily controlled by interhole delays, but airblast suppression presents more difficulties. Face reorientation is one palliative, along with more effective stemming.
Blast monitoring is now routine, and the results can be used to improve fragmentation as well as meeting regulatory conditions. The final chapter is concerned with reclamation, with the theme that quarries can no longer be simply abandoned at the end of their economic life. McNally extraction throughout the working life of the pit. However, most pits can be profitably backfilled with waste prior to final reclamation, though this must take into account the prevailing hydrogeological conditions.
The materials are categorized in terms of product size, method of processing, end-use and whether they are soil i. Many of the material classes are produced in parallel, such as washed sand being sold for concrete fine aggregate and unwashed sand from the same pit used for Table 1. McNally bricklaying mortars. Specification requirements vary with the proposed end-use; hence rock crushed for use as sealing aggregate is required to meet more stringent test criteria than that accepted as road sub-base, even though both may come from the same quarry and even from the same parent rock.
The amount of selection, winning, processing and quality control required to meet the specification is naturally reflected in the price demanded. In general this product is cobble-sized to bouldersized, with minimal fines. Very durable rock is preferred for breakwater stone and rip-rap, but lower-quality stone is acceptable for rubble and rockfill. Cut stone is rock that has been split, sawn, wire-cut or otherwise extracted in block form. These blocks are further sawn, dressed and finished for sale as dimension stone.
Crushed rock Coarse crushed rock ballast is of similar quality to concrete aggregate, but made up of coarser particle sizes and devoid of fines. Sands and gravels Sands and gravels are primarily of alluvial origin, although other sources such as dunes, marine deposits and weathered sandstone are also worked.
The results show that the maximum size of coarse aggregate rises with the decrease of the concrete compressive strength; Concrete compressive strength of coarse aggregate size affects more apparently as the ratio of water-cement decrease; with the increasing of age, concrete compressive strength of the aggregate size effect has no significant changes. Once bricks are sufficiently cured, they can be set on end to continue drying. All soils originate directly or indirectly from rocks and these are classified according to their mode of formation. The first complete handbook for every aspect of grouting technology The Practical Handbook of Grouting offers the most comprehensive, single-source reference covering all facets of grouting technology, including its application for control of water movement, strengthening of both soil and rock, and a wide range of structural applications. If you have or need soil or fill material in an area not listed, please contact us directly to be added to our database. Intact rock and hardened concrete.
Granulated slag is an artificial sharp sand produced by rapid water cooling. Soil materials The soil materials listed in Table 1. Most naturally occurring roadbase materials and select fill are used with little or no processing. McNally is an industrial raw material and may be ground, blended, moistened and chemically modified. Between these extremes are the stabilized soils, to which sand, cement, lime or bitumen are added to improve their strength, stiffness and durability. The uncertainty is due to different methods of reporting and categorization in different states, and to under-reporting of some materials such as unprocessed roadbase.
The volcanic breccia is a marginal-quality material, but it is relatively abundant and closer to markets than the basalt. River gravels and coarse sand are currently extracted from the Nepean-Hawkesbury River floodplain and blended with dune sand for concrete-making. Reserves of both coarse and fine aggregate are declining, and future supplies of the former are being sought from microsyenite intrusions and basalts more than km distant from the city centre where superquarries capable of producing 5—10 million tonnes per annum Mtpa have been proposed.
Future sources of fine aggregate are from crushed sandstone and offshore sand bodies. Most of the non-basalt production is supplied from acid volcanic and hornfels quarries.
Adelaide Coarse aggregate for the Adelaide metropolitan area is mostly obtained from seven quartzite and six carbonate limestone, dolomite quarries, which together produce about 5 Mtpa. The carbonate rocks are considered to be the best available aggregate sources here, and are mainly used for sealing and concrete batching. The quartzites, which vary between hard sandstones and true silicified arenites, are used for roadbase. Large reserves of construction sand are contained within Tertiary basins to the south and northwest. Brisbane Brisbane derives most of its aggregate from river gravels dredged from the Brisbane River and the North and South Pine Rivers, but the former is rapidly being depleted and has to be supplemented with crushed basalt, acid volcanics, granite and metamorphics.
Roadbase is also obtained from the hard rock quarries. Sand comes mainly from alluvial sources, supplemented by dune mining on North Stradbroke Island. Although Sydney is undoubtedly the worst-served in geological terms, all four cities have problems in meeting the demand for soil and rock construction materials. All have environmental problems arising from quarrying, such as the conspicuous Hills Face quarry sites in Adelaide or the presumed connection between dredging and flood damage along the Brisbane River.
The expansion of each city has in the past engulfed operating or potential quarry sites, particularly sand deposits.
Strong rocks also tend to have very low porosity hence superior durability , high elastic modulus hence toughness and high specific gravity. Durability This must be sufficient to resist breakdown during the working life of the road pavement or concrete structure. Durable rocks are generally composed of tightly interlocking grains of stable minerals i.
Shape and size The material must possess satisfactory particle shape and size distribution. These qualities influence the workability of concrete mixes the ease with which they can be poured, pumped and compacted , their cement demand and durability. In the case of roadbase, poor grading i. Unsatisfactory particle shape and grading can increase bitumen requirements for sprayed road seals and asphaltic mixtures, or cause excessive aggregate stripping under traffic.
Surface properties The material must also possess satisfactory surface properties, which include bitumen and cement adhesion, chemical non-reactivity and polishing resistance. These characteristics are related to particle mineralogy, surface roughness, adhering moisture films and dust coatings. Unfortunately, good adhesion is often best displayed by porous lithologies, while wear resistance has to be sacrificed to polishing resistance.
Economic hauling distance The source should be located within economic hauling distance of potential users and capable of being worked without undue mining or processing costs. Uniformity A source must be capable of producing a uniform product or, better still, a range of products , which is within specification or can easily be upgraded. This is often as much a function of the processing equipment as of the in situ rock. The requirements for quarried rock products will be discussed further in subsequent chapters, but are included here to highlight differences between them.
It should be emphasized that, although similar general properties for example, strength, durability and near-cubic shaped particles are required from most of the material categories, the specification limits imposed for these can vary with the proposed end-use and are not applied with the same rigour in all cases. Though these might be located at relatively isolated inland sites or in remote coastal areas, it is the latter, typified by Glensanda in western Scotland, which have received most attention.
Such a pit can replace about 20 medium-sized quarries—neatly increasing production efficiency through economies of scale, while greatly decreasing the overall environmental impact. By using large self-loading bulk carriers, stone can be transported km by sea at less cost than for 50 km of road haulage, making an international trade in aggregates feasible. Assuming a nominal quarry depth of m, a deposit of this size would occupy about 4 km2.
This would most likely be a large unaltered intrusive igneous body capable of being crushed with minimum waste and fines generation. A near-shore location adjacent to deep water, preferably screened from view and with a sheltered anchorage capable of handling ocean-going ships in the to tonne class. Although remote from residences, the site would have to be easily accessible to its small workforce. The success of such a venture would also require suitable terminal depot facilities for unloading, temporary stockpiling and possible further processing at coastal ports close to urban markets.
McNally deep-draught wharves, a sufficiently large waterside storage area and good access to trunk rail and road connections might prove difficult to obtain. It could also incur opposition from nearby residents, not to mention predatory pricing from established local producers! Furthermore, the demand for first-class aggregate for road sealing, highstrength concrete and railway ballast is only a small proportion of the total aggregate and roadbase market, most of which would continue to be met by abundant but somewhat inferior local materials.
When the superquarry concept was first mooted, it was suggested that up to 40 such pits could be developed in Scotland alone, but only one has eventuated, and more realistic projections suggest perhaps 10 worldwide by the end of the century though the number of inland 5—10 Mtpa quarries could be much greater. More specific references on individual topics are listed at the end of each chapter.
Collis, L. Dutton, A. Fookes, P. Quarterly Journal of Engineering Geology, 24, 3— Institution of Mining and Metallurgy, London. Kirk, M. A review of strategy for hard-rock coastal quarries. Quarry Management, August, pp. Knill, J. Oxford University Press, Oxford. Lay, M. I, 2nd edn, Chs 8, Gordon and Breach, New York. Manning, D. Chapman and Hall, London. McNally Orchard, D. Applied Science, London. Prentice, J. MacDonald, London. Selby, J. Smith, M. Weinert, H.
Academia, Pretoria and Cape Town. Wylde, L. Though more costly to extract than the naturally occurring gravels, quarried hard rock can be processed to deliver a variety of consistent-quality products. These include breakwater stone, ballast, aggregate and roadbase.
Inferior materials can also be upgraded by careful blending of screened fractions, using rock either selectively mined from different parts of the quarry or imported from distant pits. Although the geological and economic aspects of quarry site selection and evaluation are emphasized in this chapter, environmental factors are Table 2. McNally nowadays of equal or greater importance. The first two are summarized in Table 2. Hard rock quarry sites tend to occupy hilly land of little agricultural value— though not necessarily of low scenic value. Three common types are illustrated in Figure 2. Figure 2.
See text for explanation. The main problems are concealment, particularly in the early stages of development, and groundwater inflows below the water table which may also cause nearby wells to dry up. Irregular weathering profiles and altered zones between flows also cause quality control difficulties.
Furthermore, the unweathered flows themselves may vary in quality; some are glassy and some contain more deleterious secondary minerals than others. Hillside type This is cheap to develop, weathering depths are minimal and rock quality—in boldly outcropping and homogeneous intrusives—is generally very good.
However, this sort of quarry is most conspicuous and would rarely be approved for development these days unless the faces could be concealed behind ridges, or at least oriented away from the public gaze. Composite type This represents a quarry where extraction is confined to a particular layer; for instance, a quartzite bed, a major sill, a limestone layer, or a very wide dyke. In this situation the quarry shape is dictated by the geology to a greater degree than the previous two categories. Extraction has to be carried out along-strike, and because of the narrow pit width available careful slope design is required to ensure maximum product yield.
Rock quality in layered deposits is usually variable—more so vertically than horizontally—hence different products are mined on different benches, and blending may be desirable to make best use of the deposit. With bed strike lengths of many kilometres and generally rugged surrounding topography, opportunities for concealment are good. One visual screening technique that is widely used in both composite and hillside quarries is to work downwards from the top, leaving a facade of undisturbed rock around the pit and only an inconspicuous slot for road access to the workings inside the hill.
Relative to their output of crushed stone, hard rock quarries are smaller consumers of land than sand and gravel pits, but generate the additional nuisance of blast vibration. They also tend to be longer-lived, over years in some cases, and require more capital. Among the economic site selection factors listed in Table 2. The likelihood of consent from planning and environmental authorities also looms large in the site selection process; sites likely to be the cause of administrative delays or litigation will be discarded wherever possible.
McNally 2. Old pit faces can provide a good idea of the rock types present, their structure and weathering patterns, and bulk sampling locations. Even where old workings are no longer accessible—where, for example, they have been backfilled or built over—local geological knowledge based on their records may be helpful.
Background geological data The background geological data on a particular area may be published or unpublished; the more general investigations tend to be published, but more specific information usually remains in geological survey open-file reports.
Construction-materials resources on the outskirts of major cities have been the subject of planning studies by public authorities worldwide over the past decades. These investigations have included geological mapping, scout drilling at selected sites and limited suites of testing. Their aims were to identify and classify the principal deposits in a region, and to preserve these as long-term extractive resources by restrictive zoning before they could be sterilized by urban expansion. The primary source in a new area will usually be the regional geological map. In Australia these are mostly at scale, with selected areas mapped at ; in the UK resource maps are at or larger scales.
The larger-scale maps will not necessarily be in published form— many are available only as dyeline plans from mapping authorities. In many undeveloped areas good-quality regional geological maps are a legacy from colonial administrations keen to develop mineral resources, or from previous aid projects. Because most of these maps were not compiled with constructionmaterials exploration as their principal aim, they have to be carefully interpreted.
Generally they show bedrock geology well but ignore superficial deposits unless these are thicker than say 3—5 m. The legend and accompanying notes if any can be used to identify potentially quarryable formations, but very often hard and soft units are lumped together within these formations on the basis of their stratigraphic continuity rather than their economic potential. Formations with definite quarrying potential include limestone and quartzite beds, granite stocks, lava flows and intrusions wider than say 50 m.
Maps will probably be much less useful for pinpointing thin dykes, minor intrusions and hard quartzite beds or lava flows in otherwise non-prospective sedimentary rock formations. Even where these features are shown, they may be much more numerous than the map indicates, or areally more extensive. McNally suggest large areas where further investigation is not warranted and a few sites worth a closer look. Topographic maps Although the regional geological map may suggest prospective hard rock formations, it will not give any indication of their state of weathering Figure 2.
These will have to be resolved by inspection, initially by driving around the area and subsequently on foot at selected sites. At this stage medium-scale topographic maps say or may be useful for supplementing the geological map. Orthophotomaps—cheaply prepared topographic overlays on enlarged and tilt-corrected airphotos—are likely to be even more help. These large-scale to maps, in conjunction with airphotos, are more likely to show abandoned quarries, excavations, scrapes and large outcrops—all signposts to prospective sites.
Airphoto interpretation is also helpful for locating access roads, drilling water points, fence lines and other vehicular barriers and not least important! Airphotos are usually flown every few years, so their information is more up-to-date than maps. Lithology is only a rough guide to suitability; dolomitic shale, for example, would be considered an unlikely aggregate source in Canada where some varieties are reactive in concrete but it supplies the best-quality stone in Adelaide. Worldwide, the most common source of aggregate is undoubtedly carbonate rock, which is discussed in Chapter In the USA, the largest single market for aggregates, limestone and dolomite make up about two-thirds of the quarried stone.
Basic lavas Basic lavas are probably second only to limestone as a hard rock source, owing to their wide distribution and volume sometimes hundreds of metres thick and covering thousands of square kilometres. They can be variable in quality due to weathering along joints and flow surfaces, because of a vesiculate or brecciated fabric, and as a consequence of high olivine or secondary mineral content.
McNally Figure 2. Note that, whereas weathering intensity decreases with depth, the alteration state may remain constant in affected rock. Each column is about 0. Note faint bleaching due to alteration at the top of the flow. Similar non-durable basalts are common in the northwest of the USA. Thick non-glassy basalt flows are preferred for crushing, although scoria may be useful as a low-grade sub-base.
Two significant quarrying benefits found in basalt flows are their non-abrasive mineralogy and the presence of closely spaced columnar joints Figure 2. Basic intrusives Basic intrusives such as dolerite are less abundant, but are often superior in quality due to slower cooling and less severe weathering effects. However, deuteric alteration, magmatic differentiation and multiple intrusions can result in several different lithologies of varying quality within a large quarry.
Gravity settling of olivine-rich phases can give rise to smectitic alteration products, rendering much of the rockmass useless for concrete aggregate and suitable only as lower-quality roadbase. Thick sills and dykes, say 20 m or more in width, can provide good quarry sites where their strike length is sufficient. McNally to altered or weathered margins and mineral layering. Dolerites are the most widely quarried rocks in South Africa, where their properties have been described by Weinert Granites Acid igneous rocks are generally less suitable for quarrying than basic lithologies.
Granites and related plutonic rocks tend to be more pervasively weathered due to kaolinization within feldspar grains, and to be very abrasive because of their quartz content. Very small increases in porosity, say from 0. This is often due to hydrothermal alteration rather than weathering, and the distinction can have important practical consequences: weathered rock quality improves with depth, but altered rock remains inferior. The wide spacing between joints, compared with columnar-jointed basalt, greatly increases the required powder factor and hence blasting costs.
Mica and clay liberated during crushing may coat particle surfaces and resist bitumen adhesion. Nonetheless, granites have been quarried successfully in Hong Kong, where they are the main sources of aggregate Irfan, Porphyries and microgranites Medium-grained porphyries and microgranites Figure 2. This is possibly due to the presence of late-crystallizing potassic feldspars, which are more stable than early-stage calcic plagioclases, but may also be related to tighter grain-to-grain bonding than is the case with coarser-grained granite and granodiorite. Fine-grained acid extrusives rhyolite, dacite tend to vary in strength and durability, and are sometimes flaky due to flow banding or reactive because of the presence of glass.
Good polishing resistance is a bonus in some cases. Intermediate igneous rocks diorite, syenite, trachyte and andesite are similar to acid rocks in their aggregate-making properties, but are less common. Metamorphic rocks Of the metamorphic rocks, the most attractive quarrying propositions are high-grade gneisses, greenstones metabasalts and some hornfelses. Gneiss is widely distributed in high-grade metamorphic terrains, generally Precambrian in age, and is favoured because of its relatively stable mineralogy and subdued foliation.
Its geomechanical properties are similar to those of granite. Greenstones are similar, possibly less abrasive but denser. Some varieties contain a proportion of fibrous minerals, the most objectionable of which is asbestos. Hornfels is quarried simply because of its hardness, which may be such that the crushed aggregate is too harsh for roadbase without the addition of fines.
Quartzite Quartzite is widely exploited for roadbase, aggregate and breakwater stone, despite its variable properties. The degree of cementation, reflected in its particle specific gravity, can be quite inhomogeneous. Other varieties are thinly interbedded with phyllite and metasiltstone, or are actually silicified greywackes and arkoses. Patchy silicification may be due to groundwater movement rather than metamorphism, producing silcretes rather than true quartzites. Even massive and well-cemented quartzites can be difficult to blast without generating oversize or excessive dust which is a health hazard , and will be the cause of abrasive wear in crushers.
Finally, quartzites tend to be either too brittle or too soft for surfacing aggregate, though some gritstones are very skid-resistant. McNally where no better rock was available. Apart from the obvious problem of platy particles, these rocks often contain small quantities of sulphide minerals, which oxidize to sulphuric acid proportions as low as 0. Indurated sedimentary rocks Some indurated sedimentary rocks are quarried for roadbase and aggregate.
By far the most important of these is limestone, which is discussed in Chapter 15, and others include orthoquartzite and silicified greywackes, shales and mudstones argillites. None is entirely satisfactory as highquality aggregate, due to variable cementation and hence variable strength and durability , a tendency to polish, and the risk of alkali-silica reaction ASR in concrete.
They perform better as roadbase, because more fines are produced in crushing and their lack of durability is less critical in this application. Compared to foundation investigation and mineral exploration, the amount of drilling performed at quarry sites is remarkably small—only about one cored drillhole per million tonnes of resource in Australia. Some augering and backhoe pitting is generally carried out, mainly to probe the depth of weathered overburden and to fill in detail between outcrops. Geophysical techniques, chiefly seismic refraction and magnetometry, are occasionally used.
Core drilling Core drilling is usually performed by truck-mounted wireline rigs using triple tube barrels and water flush. Skid-mounted drills are used on steep slopes and for angled holes. The largest possible core diameter is desirable, both to ensure maximum recovery and to supply the largest possible volume of rock sample per metre drilled. In Australian practice this means HQ core 62 mm diameter , but in the UK core diameters up to mm P and S sizes may be possible in weaker and non-abrasive rock.
Vertical holes are most common, except in steeply dipping beds or where joint spacing and orientation information is required. Ideally, quarry sites should be drilled on a systematic grid, at about m centres. Once the overall geological structure of the deposit is established by coring, fill-in holes can be drilled by cheaper open hole methods. McNally well. Drilling monitors are available to record penetration rate, machine torque and thrust and hence rock hardness, but do not appear to be widely used. Core logging Core logging is based largely on visual impressions and semiquantitative test data.
A checklist for quarry drillhole logging is presented in Table 2. The main purpose is to develop a Table 2. McNally three-dimensional geological model of the proposed quarry site, with emphasis on the classes of rock material present and the distribution of weathering and alteration within the rockmass. Core samples will be taken for petrographic examination and for limited geomechanical testing, but the quantity of drillcore available will usually be insufficient for routine aggregate testing. Sometimes additional holes are drilled alongside the first if extra rock is needed for this purpose.
In any case the laboratory-crushed samples may bear little relationship to the shape and grading of the eventual quarry product, though they should be a good indicator of its durability. Geological mapping Geological mapping, typically at or , may be used to supplement the drilling data, although it must be remembered that surface outcrops are likely to be both more weathered and more closely jointed than the rockmass at depth. On the other hand, the visible rock exposures may represent the only really strong and unweathered material present within the deposit!
Similarly, some hill-capping basalt remnants may appear to be much larger in volume than in reality because of downslope movement of their copious scree. At the reconnaissance stage this mapping may be done using airphoto and topographic map enlargements as a base, but by the time detailed drilling is under way contoured photogrammetric plans should be available. At a later stage a preliminary quarry plan showing the bench and face layout, haul roads, processing plant and stockpile locations will be drawn up. Interactive PC-based mine planning software packages allow a variety of layouts to be tried out.
This computer modelling should identify possible mining and environmental problems, and help to plan further investigations to solve these. The main features that might be recorded on site investigation maps are listed in Table 2. Trial blasting and crushing Occasionally, trial blasting and trial crushing will be carried out as a final investigation stage. This would usually only be done—because of expense— when there is some doubt about marginal-quality material, to investigate blast vibration magnitudes, or where the quarry product has to meet a particularly strict specification.
McNally Table 2. McNally systematic extraction and correctly matching product quality to end-use. In other words, fresh rock should be used as first-class aggregate and not as rubble, and lesser rock grades designated as upper course roadbase, subbase and select fill as their quality decreases see Figure 2. This not only makes economic sense, it is becoming a condition of consent by environmental regulatory authorities. Previous to drilling, the site would have been regarded as a hard rock resource, in other words an area believed on good geological evidence such as outcrop patterns, presence of nearby quarries in the same rock formation, regional mapping and so on to be underlain by workable rock in economical quantities.
Although these cannot be regarded with the same confidence as proved reserves, it is expected that they will be upgraded once additional drilling is carried out. Although the determination of rock quality and quantity will always be the principal aim of quarry exploration programmes, much additional information for pit design and for planning can be obtained at very little extra cost during site investigation. Joint orientation and spacing measured during outcrop mapping, for example, is useful for blast design and face slope stability studies see Figure 2.
Groundwater depth and quality measured in exploratory drillholes, and rockmass permeability estimated from falling or rising head tests in the same drillholes, can influence the choice of explosive, pump capacity required in deep pits and the likelihood of future aquifer pollution. Much of this sort of information will be required in any case as input for the Environmental Impact Statement EIS , which must be submitted before developmental approval for the quarry can be obtained from the regulatory authorities see also Chapter McNally case of a large quarry development proposal, a Public Enquiry may be convened, at which the quarrying company will be expected to answer a wide variety of objections.
The intrusion covers ha and is one of about a dozen in the area, not all of which break the surface. It is a complex igneous body, the greater part of which consists of a microsyenite laccolith about m thick. This has been intruded by gabbro plugs and faulted, and is overlain in places by extrusive basalt. At this stage only the microsyenite is proposed for quarrying, and its importance lies in the fact that it is the closest unexploited large source more than Mt inferred reserves of aggregate-quality hard rock for the developing southwestern fringe of Sydney.
It is also located a few kilometres from a freeway and a main-line railway, and in a sparsely populated area of no particular scenic significance though close to a proposed national park. These factors have caused it to be regarded as a potential quarry site for at least 20 years, and three phases of investigation had been completed prior to , when development was finally approved. McNally The drilling outlined 32 Mt of probable reserves within the proposed quarry area, itself divided into two pits by a faulted and weathered zone.
Much larger inferred reserves, totalling about Mt, are available for future development if required. The most unusual feature of the investigation was the extensive use of seismic refraction. Although this technique only penetrates to a depth of about 10 m, it was considered cost-effective for rapidly assessing what is by quarrying standards a very large site, and for estimating depth of weathered overburden and the likely quality of the nearsurface rock.
The main problem that the investigations revealed was the extent of deuteric alteration in the upper layers of the intrusion. The economic result of this is that the upper benches of the proposed quarry will be used mainly for roadbase and concrete aggregate, while better-quality sealing aggregate will be obtained at depth as the proportion of secondary minerals diminishes.
The hill owes its form to the presence of a dish-shaped layered basic intrusion about 2 km long by 1 km wide and covering ha. Its average thickness is about m, and quarry development has been carried out down to about half this depth. The intrusion forced its way between flat-lying shales and sandstone, both uplifting and thermally metamorphosing these. A geological section through the deposit is shown in Figure 2. The Prospect laccolith is the largest body of igneous rock in the Sydney metropolitan area and the site of the largest hard rock quarry in the region.
Indeed, though quarrying has been carried out at Prospect Hill since the s, more than half the present pit—actually two quarries operated by rival companies—has been excavated since Production is now in decline due to depletion of the best materials, and Prospect quarry is due to be superseded by Mount Flora and other new hard rock sources over the next decade.
In fact, this decline was one of the main arguments put forward in the Mount Flora EIS and at the environmental enquiry in order to justify approval of that project. McNally where these are few and widely spaced. Though large, about 3 km3, much of the intrusion is very poor-quality rock by aggregate standards, and almost all of the superior upper material has been extracted. Despite these limitations, the site is centrally located in a growing city of three million people, adjacent to a freeway, and has the most extensive quarrying facilities in the state.
With selective mining and careful blending, a variety of roadbase mixes, sand and select fill are produced. Furthermore the alternative near-city sources, mainly volcanic breccia pipes, are smaller and also considered to be of only marginal aggregate quality. The geological section Figure 2. A thin chilled margin of basalt plus small amounts of late-stage differentiates pegmatite, aplite and syenite are also present.
The laccolith has also been subjected to extensive deuteric alteration, which has caused all rock types present to contain between 20 Figure 2. The dark rock is olivine-rich picrite, which disintegrates within weeks of exposure, hence the smooth, rounded exposure. In practical terms, this means that much of the Prospect rock is potentially non-durable and the quality becomes worse with depth.
Only small quantities of first-class aggregate are now produced from the remnants of the chilled margin basalt and the less olivine-rich dolerite. With hindsight, the quarry might have been developed in a different fashion, the betterquality rock reserved for use as aggregate and the middlings for roadbase. This would have required extensive drilling and quarry planning, which is scarcely an option in a century-old quarry that has passed through the hands of many operators. Quarterly Journal of Engineering Geology, 12, — Quarterly Journal of Engineering Geology, 13, — Haines, A.
Quarry Management, April, pp. Hawkins, A. Engineering Geology Special Publication No. Hoek, E. Irfan, T. Quarterly Journal of Engineering Geology, 27, 25— Oberholsen, R. Quarry Management and Products, 9 April , —6. Van Schalkwyk, A. Quarry Management and Products, 8 June , — Engineering Geology, 2, — McNally CHAPTER 3 Sand and gravel Sand and gravel deposits are normally considered together as sources of naturally occurring fine and coarse aggregate found mainly in alluvial environments.
In former times they constituted the largest mineral commodity extracted in developed countries, but are now being overtaken by crushed rock production. Their popularity stems from being close to users, cheap to extract and easy to process by minimal crushing, washing and screening. They are well suited to small-scale quarrying operations, providing concrete aggregates and sealing aggregates to local markets. Their present decline in many areas is partly because the best deposits have been worked out or built over, and partly a response to environmental restrictions, which tend to bear more heavily upon sand and gravel operations than on hard rock quarries.
The soundness and stable mineralogy of sand and gravel deposits result from their having been subjected to comminution and sorting by natural— mainly fluvial—processes of erosion and transportation. These selectively eliminate weak or porous lithologies and concentrate different size fractions in distinct geological locations.
Gravel is more heterogeneous, but is still largely made up of siliceous metamorphic and igneous rocks. Many alluvial gravels are in fact reworked older conglomerates or terrace deposits, in which the clasts have been subjected to at least two cycles of erosion, transport and deposition. Consequently, only the hardest and most durable stone survives.
The best deposits are usually gravel-rich remnants from pluvial stages within the Pleistocene, reworked Pleistocene glacial materials, or alluvial fans close to active faults along mountain fronts. The best deposits are those laid down by meltwater streams beneath the glacier or close to the ice front Figure 3. McNally Figure 3.
Aeolian dune sands are composed of uniformly sized, clean and wellrounded grains that improve the workability of concrete mixes. They are often used in gap-graded mixes with crushed coarse aggregate for this purpose, or blended with crusher grit to achieve a more even fine aggregate grading. Strandline deposits of beach sand and shingle gravel mark higher sea and lake levels in tectonically active or formerly wetter areas.
They tend to be smaller in volume and coarser in grain size than dunes, but otherwise well sorted like them. Salt and shell concentrations are sometimes a problem. Marine sources are largely drowned Pleistocene alluvial, fluvioglacial and littoral deposits Figure 3. As a client you can expect fast individualized response and defensible accurate results when engaging for construction materials testing.
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Summary. An introduction to the investigation, extraction, processing and specification of natural soil and rock materials, with an emphasis on why particular. Soil and Rock Construction Materials© ykoketomel.mly For Maria© G.H. McNally Soil and Rock Construction Ma.
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