Characterisation of rock aggregate breakage properties using realistic texture‐based modelling

Realistic texture‐based modelling methods, that is microstructural modelling and micromechanical modelling, are developed to simulate the rock aggregate breakage properties on the basis of the rock actual microstructure obtained using microscopic observations and image analysis. The breakage properties of three types of rocks, that is Avja, LEP and Vandle taken from three quarries in Sweden, in single aggregate breakage tests and in inter‐aggregate breakage tests are then modelled using the proposed methods. The microstructural modelling directly integrates the microscopic observation, image analysis and numerical simulation together and provides a valuable tool to investigate the mechanical properties of rock aggregates on the basis of their microstructure properties. The micromechanical modelling takes the most important microstructure properties of rock aggregates into consideration and can model the major mechanical properties. Throughout this study, it is concluded that in general, the microstructure properties of rock aggregate work together to affect their mechanical properties, and it is difficult to correlate a single microstructure property with the mechanical properties of rock aggregates. In particular, for the three types of rock Avja, LEP and Vandle in this study, crack size distribution, grain size and grain perimeter (i.e. grain shape and spatial arrangement) show good correlations with the mechanical properties. The crack length and the grain size negatively affect the mechanical properties of Avja, LEP and Vandle, but the perimeter positively influences the mechanical properties. Besides, the modelled rock aggregate breakage properties in both single aggregate and inter‐aggregate tests reveal that the aggregate microstructure, aggregate shape and loading conditions influence the breakage process of rock aggregate in service. For the rock aggregate with the same microstructure, the quadratic shape and good packing dramatically improve its mechanical properties. During services, the aggregate is easiest to be fragmented under point‐to‐point loading condition, and then in the sequence of multiple‐point, point‐to‐plane and plane‐to‐plane loading conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

The use of low-grade and unsound crushed rock aggregates in Ghana for construction

Summary Ghana and many developing countries have relied heavily, in the past, on hard granites and granitic gneisses for the production of rock aggregates and rock products for civil engineering works including the construction of roads and buildings. Experience in Ghana has shown however, that the quantity of crushed rock aggregates produced from hard rocks have proved insufficient for the needs of the country. This situation has called for engineering geological studies into the use of rock types and rock formations previously designated as low grade and unsound for the production of aggregates. The major objective of this study was to review the occurrences of non-conventional hard rocks and gravels such as quartzites, silicified sandstones, metagreywackes, dolomitic limestones and quartz gravels. This was followed by the application of appropriate standard specification tests to establish criteria for the selection and recommendation for the use of low grade and unsound rocks and gravels for various civil engineering projects in Ghana and other developing countries, especially those of the subregion with similar geological formations.     

Petrologic variations in quaternary volcanic rocks,British Columbia,and the nature of the underlying upper mantle

Volcanic activity has produced Late Tertiary and Quaternary cinder cones and flows between the Snake River Plain, U.S.A. and the Yukon Territory, Canada. The rock types include basanites, alkali olivine basalts, high-iron basalts, hawaiites, ankaramites, nephelinites, and olivine tholeiites. The alkali olivine basalts, basanites and hawaiites sampled are chemically similar to rocks from the mid-Atlantic islands. Associated with the volcanic rocks are xenoliths of ultramafic rocks, gabbros, granites and granulites.Seismic data indicate that the Moho throughout the region dips eastward at a very shallow angle. The low velocity zone has been located beneath southern British Columbia and displays a topographic high trending northwest-southeast. The nephelinite was erupted from near the crest of this high with less undersaturated lavas erupted from along its flanks.The suite of ultramafic xenoliths spans a greater variety of rock types than can be generated by maximum amounts of partial melting of a uniform source material to produce the lavas in the region. Calculated residual olivine compositions in equilibrium with the magmas at low velocity zone depths and liquidii temperatures are more iron-rich than the typical lherzolite xenolith olivine. This suggests that the residua from the partial melting episodes which produced the volcanic rocks are different from the upper mantle lid above the low velocity zone as represented by the ultramafic xenoliths.     

Cenozoic basalts in North China—Their distribution,geochemical characteristics and tectonic implications

Epuptions of alkali and subalkali basalts occurred respectively during Paleogene, Neogene, and Quaternary in North China. They are interplate, non-oceanic basalts. The alkali basalts range from Ne-normative to Hy-normative basalts and the subalkali basalts belong to the continental tholeiites. Based on their distribution, geological ages and petrographic series the magmatic evolution of Cenozoic basaltic rocks in North China can be divided into three stages. Geochemical data from this study indicate that Cenozoic basaltic magmas of North China were derived from two different mantle sources.     

青藏铁路块石气冷结构路堤下冻土温度场变化分析

基于青藏铁路沿线多年冻土区温度监测断面,选取了不同冻土分区中的8个块石路堤结构(块石路基、块石护坡、块石路基加块石护坡)断面,对其下温度场的变化分析研究.结果表明:经过2~3个冻融循环后,块石结构路堤下冻土上限已抬升了1.4~5.3 m,说明块石路堤结构已起到了积极调节下伏冻土温度的作用.结果也显示,在上限抬升的同时,其下部的冻土地温也在升高,但是这种过程已逐渐被块石路堤结构的降温所抑制,而这种抑制程度受控于不同的冻土区域.在不同的冻土分区中,无论是何种形式的块石路堤结构,其降温趋势是不同的.Ⅳ和Ⅲ冻土区块石路堤基底的负温积累比较明显,而I和Ⅱ区的较弱.     

The origin of the Naturaliste Plateau,SE Indian Ocean: Implications from dredged basalts

Although a 1972 dredging by USNS Eltanin from the submarine Naturaliste Plateau was reported to yield rocks of continental origin, a re‐examination of the dredge haul shows that the rock clasts are in fact altered tholeiitic basalts. They have affinities both with MOR basalts and, especially, within‐plate basalts. Petrographically they correlate most closely with the Bunbury Tholeiitic Suite on the Australian mainland to the east. The basalts are reworked cobbles in a manganiferous Quaternary slump mass, which contains a quartz‐rich, felsic, detrital mineral suite with a granite‐gneiss provenance. The basalt cobbles were part of a basal conglomerate, which covered large areas of the Plateau. It is suggested that this was laid down from nearby elevated volcanic structures formed during the inception of seafloor spreading and the separation of Greater India from Australia at about 122 Ma BP.     

Acidic Rocks as Aggregates in Concrete: Engineering Properties,Microstructures and Petrologic Characteristics

In this research, the possibility of replacing different portions of the normally used aggregate by acidic rocks was investigated. These rock types outcrop at the northern part of Eastern Desert, southwest Ras Gharib area where large quantities of good quality acidic rocks are available their. Portland cement concrete is a composite material made up of the hydrated cement matrix, fine aggregate and coarse aggregate. The scanning electron microscope equipped with an energy dispersive X-ray analysis system (EDX) has been applied to investigate several aspects of Portland cement concrete microstructure. The topics investigated so far include the influence of aggregate composition on the development of the cement paste-aggregate interface and the formation of calcium silicate hydrate CSH/calcium silicate aluminate CSA formation. The silicate gel coated the aggregates in the concrete paste and crystallized into well defined needle like shape, cotton shape as well as euhedral to subhedral crystals of silicate/alumiante and ettringite minerals with free lime librated from the hydrolysis process. The free lime can react again with the aggregates leading to the formation of cementing materials which increase strength and durability of the concrete paste by increasing the interfacial bonds between the used aggregates.     

Assessment of excavatability,abrasivity and slope stability in a sandstone quarry in Istanbul,Turkey

The Cebeci region is characterized by outcrops of Carboniferous sandstone, including diabase dykes. This region is very important area for aggregate production in Istanbul, Turkey. The aim of this study is to determine the engineering geological properties of sandstones to assess the excavatability, abrasivity and stability of cut slopes in a quarry site. Firstly, the sandstone samples were used to determine their petrographical and mineralogical characteristics. Then, physico-mechanical tests were performed on these samples. In order to determine rock mass properties, scan-line surveys were performed, and the major orientations of discontinuities were analyzed through the stereographic projection technique. Kinematical analyses were also made to determine the potential failures at the quarry site. According to the results obtained, excavatability is changed from easy ripping to hard ripping on sandstones; the carbonated sandstone is less abrasive than other sandstones. Based on the field studies and stability analyses of the cut slopes, optimum slope geometry and necessary support measures, such as wire mesh and rock fall barriers, are suggested.     

辽西及邻区中-新生代火山岩的时空对称分布及其启示

辽西中生代火山活动之后,老第三纪、新第三纪和第四纪玄武岩的喷溢依次向东、西两侧对称扩展,其范围从内蒙古阿巴嘎至辽东宽甸,长800km。相应地,火山岩从中-酸性的粗面质岩石变成碱性玄武岩,表明岩浆来源越来越深。Sr-Nd同位素特征显示从白垩纪末到第四纪,岩浆源区从EMI型富集地幔转向亏损地幔。根据火山岩时空对称分布的格局,本文提出了两个值得深入研究的问题:大陆板块与大洋板块的扩张与增生方式为什么不同?辽西乃至中国东部有小型地幔柱存在的可能性吗?     

Study on the geochemical characteristics of ocean-ridge and oceanic-island volcanic rocks in the Nan-Uttaradit zone,northern Thailand

Field investigations and laboratory integrated research as indicated that ophiolite mélange in the Nan-Uttaradit zone, northern Thailand, consists of fragments of tectonites such as metamorphic peridotite (extremely silicified serpentinite), cumulates (pyroxenolite, gabbro, and gabbro-diorite), ocean-ridge basalt, oceanic-island ba-salt and radiolarian silicalite, and it was formed during D3-P. The rock series, rock types and petrogeochemical characteristics of metamorphic tholeiites in the Nan area of the Nan-Uttaradit zone are similar to those of ocean-ridge basalts (C1) in China's Ailaoshan zone. As for the Hawaiites in the Nan area of the Nan-Uttaradit zone, their major elements, REEs and trace elements are similar to those of oceanic-island basalts in China's Jinshanjiang zone (P11). In the Uttaradit area of this zone the metamorphic alkaline basalts show transitional petrogeochemical characteristics between ocean-ridge basalts and oceanic-island basalts, which were still formed in oceanic-island environments. The above-described basalts are all oceanic volcanic rocks and they are the most important part of the Paleo-Tethys oceanic crust in the Nan-Uttaradit zone.     

Laboratory Characterization of Cemented Tailings Paste Containing Crushed Waste Rocks for Improved Compressive Strength Development

This paper aims at investigating some physical and mechanical characteristics of cemented tailings paste incorporating different amounts of crushed waste rocks (hereinafter called paste aggregate fill, PAF) for underground stope filling. Different mixture formulations were prepared with three classes of crushed waste rocks (or aggregate) grain size, namely 0/10, 0/15 and 0/20 mm. The amount of crushed waste rocks in the PAF mixtures ranges from 10 to 50% by volume (% v/v) (or 8–45% by mass, %m) of dry mill tailings and crushed waste rocks. The results show that the addition of crushed waste rocks in cemented tailings paste mixtures allows a significant unconfined compressive strength (UCS) development after 28 and 90 days of curing. The highest UCS was obtained from the mixtures containing 50% v/v of crushed waste rocks of class of size 0/15 mm. The PAF mixtures with the coarser crushed waste rocks (class of size of 0/20 mm) exhibit some particles segregation.     

Geology and geochemistry of metabasalts of Shimoga schist belt,Dharwar Craton: implications for the late Archean basin development

The late Archaean Shimoga schist belt in the Western Dharwar Craton, with its huge dimensions and varied lithological associations of different age groups, is an ideal terrane to study Archean crustal evolution. The rock types in this belt are divided into Bababudhan Group and Chitradurga Group. The Bababudhan Group is dominated by mafic volcanic rocks followed by shallow marine sedimentary rocks while the Chitradurga Group is dominated by greywackes, pillowed basalts, and deep marine sedimentary rocks with occasional felsic volcanics. The Nb/Th and Nb/La ratios of the studied metabasalts of the Bababudhan Group indicate crustal contamination. They were extruded onto the vast Peninsular Gneisses through the rifting of the basement gneiss. The Nb/Yb ratios of high-magnesium basalts and tholeiitic basalts of Chitradurga Group suggest the enrichment of their source magma. Based on the flat primitive mantle-normalized multi-element plot with negative Nb anomalies and Th/Ta-La/Yb ratios, the high-magnesium basalts and tholeiitic basalts are considered to have erupted in an oceanic plateau setting with minor crustal contamination. The high-magnesium basalts and tholeiitic basalts formed two different pulses of same magma type, in which the first pulse of magma gave rise to high-magnesium basalts which were derived from deep mantle sources and underwent minor crustal contamination en route to the surface, while the second pulse of magma gave rise to tholeiitic basalts formed at similar depths to that of high-magnesium basalts and escaped crustal contamination. The associated lithological units found with the studied metavolcanic rock types of Bababudan and Chitradurga Groups of Dharwar Supergroup of rocks in Shimoga schist belt of Western Dharwar Craton confirm the mixed-mode basin development with a transition from shallow marine to deep marine settings.     

Geochemistry and tectonic significance of metamorphic sole rocks beneath the Beyşehir–Hoyran ophiolite (SW-Turkey)

The Beyşehir–Hoyran ophiolite is situated in the western part of the Tauride belt (SW Turkey) and crops out at two localities north of the lake Beyşehir. It mainly comprises harzburgitic peridotites that were tectonically emplaced to their present position during the Late Eocene. The ophiolites themselves are tectonically overlain by either slope basin deposits with lava blocks (Eğirler formation) or massive Triassic limestone blocks (Deliktaş formation). High-grade sub-ophiolitic metamorphic rocks, i.e. epidote amphibolite, amphibolite, and pyroxene amphibolite, together with minor quartzite and calcschist, are observed at the base of the ophiolite sequence, where they occur as thin tectonic slices with an inverted metamorphic gradient. Average P–T conditions of 630–770 °C and c. 6 ± 1.5 kbar are calculated for the metamorphism of the amphibolites by conventional geothermobarometry, corresponding to a burial depth of 18–20 km. Both the sub-ophiolitic metamorphic rocks and the overlying mantle tectonites were intruded by isolated tholeiitic (Nb/Y = 0.041–0.108) diabase dikes, which do not transect the tectonic contact between the two units. Geochemical investigations of the amphibolites of the sub-ophiolitic rock suite show two different geochemical affinities, with the first group being alkaline in character (Nb/Y = 1–3.86) and the second one being tholeiitic (Nb/Y = 0.064–0.13). REE patterns, trace element plots and tectonomagmatic discrimination diagrams indicate that the most probable protoliths for alkaline amphibolites are within-plate type alkali basalts, whereas those of the tholeiitic group resemble tholeiitic island arc basalts. Similarities between the geochemical characteristics of the amphibolites and those of the volcanic rocks of the Eğirler formation strongly suggest that the latter are the protoliths of the amphibolites.     

Relationships between texture and mechanical properties of hybrid rocks from the Jaala–Iitti complex, southeastern Finland

The relationships between petrographical and mechanical properties of rock aggregate raw materials from the hybridised, subvolcanic Jaala–Iitti complex, southeastern Finland, were investigated. Petrography was quantified from polished thin sections with a polarising microscope to determine the modal composition and grain size distribution, and resistance to fragmentation and abrasion were determined. Abundance of fine-grained minerals (especially of hornblende), fine grain size-dominated grain size distribution, uniform spatial dispersion of hornblende crystals, and intense micrographic intergrowth texture with interlocking grain boundaries were found to have the greatest positive influence on the mechanical properties. The results showed the potentiality of hybridised rocks as raw materials for high quality aggregates that can resist fragmentation and abrasion.     

Investigation of the effect of aggregate shape and surface roughness on the slake durability index using the fractal dimension approach

Argillaceous rocks cover about one thirds of the earth's surface. The major engineering problems encountered with weak- to medium-strength argillaceous rocks could be slaking, erosion, slope stability, settlement, and reduction in strength. One of the key properties for classifying and determining the behavior of such rocks is the slake durability. The concept of slake durability index (SDI) has been the subject of numerous researches in which a number of factors affecting the numerical value of SDI were investigated. In this regard, this paper approaches the matter by evaluating the effects of overall shape and surface roughness of the testing material on the outcome of slake durability indices.

For the purpose, different types of rocks (marl, clayey limestone, tuff, sandstone, weathered granite) were broken into chunks and were intentionally shaped as angular, subangular, and rounded and tested for slake durability. Before testing the aggregate pieces of each rock type, their surface roughness was determined by using the fractal dimension. Despite the variation of final values of SDI test results (values of I_d), the rounded aggregate groups plot relatively in a narrow range, but a greater scatter was obtained for the angular and subangular aggregate groups. The best results can be obtained when using the well rounded samples having the lowest fractal values. An attempt was made to analytically link the surface roughness with the I_d parameter and an empirical relationship was proposed. A chart for various fractal values of surface roughness to use as a guide for slake durability tests is also proposed. The method proposed herein becomes efficient when well rounded aggregates are not available. In such condition, the approximate fractal value for the surface roughness profile of the testing aggregates could be obtained from the proposed chart and be plugged into the empirical relation to obtain the corrected I_d value. The results presented herein represent the particular rock types used in this study and care should be taken when applying these methods to different type of rocks.     

Geochemistry of the Eocene Jijuntun Formation oil shale in the Fushun Basin,northeast China: Implications for source-area weathering,provenance and tectonic setting

Within the fault-bound Fushun Basin of northeastern China, the Eocene Jijuntun Formation hosts extensive deposits of thick lacustrine oil shale. Systematic sampling and geochemical analysis of these deposits has revealed that the parent rocks of the oil shale underwent moderate chemical weathering; and that its mineralogy and trace and rare earth element geochemistry were mainly controlled by parent rock composition, with no synsedimentary changes in the source terrain. Based on source rock and tectonic setting discrimination diagrams, we concluded that the parent rocks of the oil shale were mostly basalts of the Paleogene Laohutai Formation. These basalts originated in a continental back arc environment and contain abundant nutrient elements such as Fe, P, Ni, Cu and Zn, all of which are essential for the growth of aquatic photoautotrophs in lakes. Continuous, high primary productivity in the Jinjuntun lacustrine depocentre, combined with a stable tectonic setting and underfilled sedimentary environment, were key factors in the genesis of its oil shale.     

渤海海峡跨海通道围岩条件探查与施工方法分析

渤海海峡跨海通道是连接中国山东半岛与辽东半岛重要的交通运输干线工程,该通道的建成对于推动环渤海地区经济的快速发展及振兴东北老工业基地具有重要意义。而通道区域的围岩条件及岩石的力学性质对于该工程施工方案的优选十分重要。通过区域地质调查、海域地层钻探和地层剖面实测以及岩石力学性质分析表明:通道区域内出露的地层从上到下依次为第四系、新近系与上元古界;其中第四系厚10~120 m,主要是一些松散的沉积物,没有隔水层,稳定性差;新近系不发育,仅在局部地区零星分布,主要由大孔隙的玄武岩构成,其抗压强度等岩石力学性质指标偏低,且低于正常值;而上元古界则由石英岩与石英岩互层的板岩和千枚岩构成,石英岩稳定、坚硬,抗压强度和抗剪强度大,板岩和千枚岩属于软质岩石,遇水易软化。因此,在已有的"全隧道"和"南桥北隧"两种方案基础上,建议渤海海峡跨海通道"北隧"段采用深埋隧道法,即该隧道不仅应穿越上部的第四系和新近系,还要穿越上元古界与石英岩互层的的板岩和千枚岩,而设置于石英岩中。根据通常采用的利用围岩确定隧道最小埋深的挪威法,建议北段隧道的最小埋深应在65 m左右。另外,由于石英岩比较坚硬,因此,渤海海峡跨海通道工程宜采用钻爆法和TBM法进行施工。      

Investigation on the usage of different rock aggregates as abrasive materials in natural stone aging process

The process of giving an antique look, a worn and “old” appearance, to natural stone surfaces, which can be observed by abrasion in natural ways through a long time, is called artificial aging. Natural stone processing facilities that involve mass production usually prefer vibration aging machines. This study examines the utilization of various rock aggregates and abrasive residuals instead of synthetic abrasives used in aging machines. Natural stone samples with different properties were aged in a vibration aging machine using andesite, granite, sandstone, pebble stone, abrasive stone residuals, and ceramic abrasives. At the end of the study, the aging performance of different rocks was determined; granite was found to be the most effective. Rock aggregates were ranked in terms of their abrasiveness (aging) performance, from the most effective to the least effective as: granite, ceramic abrasive, sandstone, andesite, pebble stone, and abrasive stone residuals. It was observed that rock aggregates can be used in the aging process instead of synthetic ceramic abrasives, with desired performance.     

Influence of physico-mechanical properties of Indian dimension stones on cutting rate of diamond wire saw

Cutting performance of diamond wire saw is a key factor influencing mine planning, production scheduling, and equipment selection for dimension stone quarries. It is normally measured in terms of cutting rate. Rock samples collected from various granite and marble quarries in India were tested in laboratory to determine their physico-mechanical properties. Cutting rate of diamond wire saw was measured in the field studies during the actual cutting process in quarries. Using these laboratory determined properties and the cutting rate, a multiple linear regression model has been developed to predict the cutting rate of diamond wire saw. Physico-mechanical properties of rocks determined in laboratory are used as independent variables and cutting rate as predictor variable in the regression model. The study indicates that the cutting rate increases with a decrease in most of the hardness and strength parameters of rock. The final model is tested for its goodness of fit indicating a significant linear relation between cutting rate and physico-mechanical properties, namely tensile strength, slake durability index, and Cerchar hardness index with regression coefficient of 94%. The resulting model can be used suitably for different types of hard to medium hard and soft dimension stones. The generalized model for estimating the cutting rate becomes a handy tool for mining engineers to work out operating efficiency, expenses, planning etc. of the dimension stone block cutting.     

冲绳海槽火山岩岩石系列的厘定及构造环境意义

冲绳海槽是一个处于弧后扩张作用早期的年轻的弧后盆地,是研究弧后扩张作用早期盆地演化和壳幔过程的天然实验室.随着调查研究工作的逐步展开和深入,也发现了一些新的、重要的、亟待解决的科学问题,而火山岩岩石系列归属的厘定又是其他研究工作的基础.在系统收集和整理迄今已有冲绳海槽火山岩资料的基础上,结合近期分析测试数据, 对冲绳海槽火山岩的岩石系列归属进行了重新厘定,探讨了火山岩的构造环境指示意义和浮岩与玄武岩之间的成因联系.研究结果表明:冲绳海槽火山岩分布具有以基性玄武岩和酸性(流纹)英安岩为主的双峰式特征,中性火山岩稀少,基性的玄武岩属于亚碱性系列的橄榄拉斑玄武岩,酸性浮岩可归属为亚碱性岩系的流纹英安岩或流纹岩;在构造环境判别上,冲绳海槽玄武岩表现出大洋中脊和岛弧构造环境的特点,既有别于大洋中脊扩张中心,也有别于成熟型弧后盆地,呈现出弧后早期扩张阶段盆地独特的构造环境特征;广泛分布于冲绳海槽的酸性浮岩表现出一定的岛弧环境的特点;酸性浮岩与玄武岩具有同源性,酸性岩是基性的玄武质岩浆经不同程度结晶分异和同化混染作用的产物.