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Fracture zones (crushing annulus, fracture zone, fragment formation zone) formed around a blast-hole. (Whittaker et al. 1992)
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The degree of induced fracturing related to bench blasting has been investigated in the Offerdal Nappe in the Landögssjö area, in the county of Jämtland, Sweden where the dimension stone "Flammet Quartzite" is quarried. Two fracture trace maps have been compiled; one from an area within the quarry, where natural and induced fracturing are analysed,...
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Context 1
... The explosion is detonated simultaneously along the entire length of the blast hole and the effects along the blast hole axis direction can be neglected. The process of the explosive blasting involves the formation of a crushed annulus immediately around the blast, followed outwards by a fracture zone into a discrete fragmented zone (Fig. 1). The degree of bedrock fracturing related to blasting can thus be estimated if the fracture and the fragment zones can be defined within an existing volume of fractured rock. In the Nya Finnsäter quarry, extraction of rough blocks is carried out by bench blasting, with a maximum bench height of up to 3.55 m. The bench is cut slightly ...
Context 2
... continuous structures, such as fracture zones and kink bands. The greater frequencies of coalescing shorter frac- tures in part of Norra Finnsäter is considered to be due to the crossing of larger fracture zones. As noted above, the fragment and fragmentation zone (Whittaker et al. 1992) define an area that is affected by the induced fracturing (Fig. 1). Figure 4 demonstrates that "longer" fracture traces have a generally straight appear- ance, with a low roughness and curvature. Shorter fracture traces are generally concentrated in areas where larger conjugate structures cross. However, they still can be described as generally straight (Fig. 4). The characterisations of fractures ...
Context 3
... be described as generally straight (Fig. 4). The characterisations of fractures related to the blasting are based on size, termination, roughness and curvature. Roughness and curvature were assessed visually. Two cases of fracture occurrence have been defined: type A with coal- escing fractures with at least one end terminating in a drill hole ( Fig. 1) and type B coalescing fractures with one end terminating in a fracture of type A contained within the fragment formation zone. Table 3 summarises the fracture terminations according to these ...
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Citations
... In quarry blasts, the conversion of chemical energy into gaseous expansion can produce a shock wave with a pressure in the range of 0.5-50 GPa, readily overcoming the tensile strength of near-surface rocks (Saharan et al. 2006). As shown in the example in Figure 8, an explosion fracturing pattern generally comprises a cavity in the epicenter, a crushed annulus with dense fractures and an exterior zone with radial cracks (Loorents et al., 2000;Mitelman and Elmo, 2014;Saharan et al. 2006). Figure 9 shows a fracturing pattern in the Maiolica limestone exposed in the Frontale locality that closely resembles an explosion fracturing pattern. ...
The formation of the "expansion breccia" observed in the Lower Cretaceous Maiolica limestone in the Umbria-Marches region of Italy is attributable to a fluid-assisted brecciation process that occurred during the late Miocene exhumation of the Northern Apennines. The hydrothermal fluids probably originated as brine solutions trapped in the Burano anhydrite while it was in a plastic state. The migration of the Burano from the plastic to the brittle domain during unroofing resulted in liberation and injection of over-pressured hydrothermal fluids into the overlying limestone, causing hydraulic fracturing. Mapping of breccia morphology along a 400-m transect showed structures produced by different flow regimes, with chaotic and mosaic brec-cia characterizing the core parts of the section and mineral-filled fractures and veins in the margins. Based on the clast size in the chaotic breccia, the estimated velocities for fluidizing the aggregates of clasts and sustaining the clasts in suspension are, respectively, 15 cm/s and 65 cm/s. Crack growth was probably the main mechanism for the fragmentation of the limestone. Explosion fracturing patterns were only sporadically observed in the breccia, indicating substantial heat loss of the over-pressured fluids during their ascent to the Earth's surface.
... In addition, the actual fracturing state of a rock mass could be a combination of the induced fracturing effect on the natural fracture system. If the extraction method causes significant fracturing, alternative methods should be considered [44]. ...
The use of natural stone has historical and environmental value that makes it strategically valuable for landscape conservation in Europe. Marble, among others, is widely spread on Earth, and it offers high-performance features in architectural applications. However, the complexity of these formations and the rock variability in different ore bodies require detailed studies of the natural and induced stress state, the fracturing degree, and the influence of external factor (such as temperature and/or chemical agents) on the mechanical properties in order to optimize the exploitation processes by reducing extractive waste. This article shows a series of studies conducted by the authors over the last 20 years aimed at making the exploitation of marble blocks in the Carrara basin safer, more efficient, and, therefore, more sustainable. In particular, studies for increasing our knowledge of the natural and the induced stress state through on-site measurements and numerical modeling, studies to improve the quality of the exploited material through improvements of cutting technologies, studies to improve the knowledge of the mechanical behavior of the material under varying loads and temperature conditions, and studies to improve the reuse of water materials and their reduction are reported.
... In addition, the actual fracturing state of a rock mass could be a combination of the induced fracturing effect on the natural fracture system. If the extraction method causes significant fracturing, alternative methods should be considered [44]. The amount of waste increases while the average extractable block size decreases due to the joint system deviating from orthogonality where the spacing pattern remains equal. ...
... In addition, the actual fracturing state of a rock mass could be a combination of the induced fracturing effect on the natural fracture system. If the extraction method causes significant fracturing, alternative methods should be considered [44]. ...
The use of natural stone has a historical and environmental value that makes it strategically valuable for landscape conservation in Europe. Marble, among others, is widely spread on Earth, and it offers high-performance features in architectural applications. However, the complexity of these formations and the rock variability in different ore bodies require detailed studies of the natural and induced stress state, the fracturing degree, and the influence of external factor (such as temperature and/or chemical agents) on the mechanical properties in order to optimize the exploitation processes by reducing extractive waste. This article shows a series of studies conducted by the authors over the last 20 years aimed at making the exploitation of marble blocks in the Carrara basin safer, more efficient, and, therefore, more sustainable. In particular, studies for increasing the knowledge on the natural and the induced stress state through on-site measurements and numerical modeling, studies to improve the quality of the exploited material through improvements of cutting technologies, studies to improve the knowledge of the mechanical behavior of the material under varying loads and temperature conditions and studies to improve the reuse of water materials and their reduction are reported.
... Wherever it was possible to obtain data, information was gathered in each area of exploitation concerning natural fracturing (30 active and abandoned quarries). In quarries for dimension stone exploitation, low-energy explosives are used; therefore, artificial fractures are not present (Loorents et al. 2000). This information comprises the strike and dip of all the visible and accessible discontinuities, the number and orientation of the joint sets present and the joint space measured in a perpendicular direction of two consecutive joints bellowing to the same joint set. ...
The most negative aspects in the exploitation of weathered granites as ornamental stones tend to be heterogenic coloration and fracturing. Therefore, an accurate study is needed for a comprehensive evaluation of the granite resources during an exploration campaign. This paper presents the results of the fracturing evaluation of a region located in north of Portugal, where the Mondim de Basto granite, a stone with a high weathering degree, is exploited. The regional fracturing was evaluated from lineaments in aerial photos and then compared with local jointing in quarries. The jointing in each quarry is characterized according to the strike and dip, joint spacing and volumetric joint count. Two indices were proposed to facilitate the jointing comparison among quarries: the joint space length (L
js) and joint set spacing (S
js). L
js is based on the sum of all the spacing values obtained perpendicularly to the strike direction. S
js is computed based on the overall mean/median spacing and on the number of joint sets observed in each quarry. The most important joint sets in the subdivision of the rock mass were found not to be in accordance with the regional fracturing patterns, highlighting the necessity of studying the fracturing at all scales.
... 반면 광물자원의 탐 사는 오늘날의 탐사자들에게는 필수적이 된 지질학적, 지화학적, 지구물리적 방법들을 이용한 정밀 과학의 일부가 되어 있다. 그러나 광상과 마찬가지로 석재자 원의 부존 역시 한정된 지질학적 조건에 의해 좌우되 며 이러한 조건들을 판별함으로서 체계적인 방법으로 석재의 유망지를 발견할 수 있을 것이다 (Taboada et al., 1997;Taboada et al., 1998;Taboada et al., 1999;Taboada et al., 2002;Loorents et al., 2000;Selonen et al., 2000;Tercan and Özçelik, 2000;Sousa, 2007;Ribeiro et al., 2007;Moreiras et al., 2008 의 남서부 그리고 1 대 50,000 거창도폭 (Kim and Kim, 1970)의 중앙부에 넓게 분 포한다. 이 곳 일대는 쥬라기 화강암 (Dale, 1923, Jahns, 1943. ...
This research are systematic and scientific approaches to obtain the distribution, occurrence and quality of granite stone for building purposes. The process of dimension stone exploration must be carried out to know the underground potentiality of granitic body using the basic data collection and study, field mapping, detailed drilling survey, televiewer technique, and physical and chemical tests in the Geochang area. Televiewer data obtained in drilling boreholes can be accurately distinguished from the discontinuous face, strike and inclination, extension which is difficult to obtain in a core logging. 3D joint images will be helpful to establish a quarry exploitation plan because the 3D joint images give quite accurate information down to depth below the outcrop surface. Through the process of the quality estimation on the Geochang site, the proven reserve estimated as dimensional building stone are calculated with good quality in petrologic and physical properties.
... This area is rich in books and research articles such as Prentice (1990) discussing the geology of construction materials, Blyth and de Freitas (1974) that is a text of geology for engineers. Other works include Shadmon (1993) on the role of geological engineering on the environmental effects of dimension stone and Loorents et al. (2000) on the natural fracture system in a dimension stone quarry in the Offerdal Nappe, ...
This study considered the enabling environment of artisanal dimension stone (i.e. blocks cut and shaped from natural rock using hand tools) for building in Nairobi, Kenya. It relied on the socio-technical system theory to capture the forces (variables) that influence the business/enabling environment of the building material. The socio-technical perspective was necessary because hitherto existing literature had only considered the archi-technical, patho-technical, geo-technical, archaeo-technical and eco-technical perspectives. The study sought to explore the organizational structure of the construction industry in Kenya and profile the internal structure and the external environment of artisanal dimension stone producing units so as to identify and ascertain the socio-technical forces (variables) influencing the production and use of the stone. The study further sought to analyse the interrelationships among the identified forces in order to suggest adjustments to the enabling environment.
The study applied PEST analysis techniques (including stakeholder and factor analyses) to characterise the enabling environment. The research took place in two main stages: exploratory and conclusive. The exploratory study involved the use of ethnographical methods (unstructured interviews and participant observation), analysis of secondary data and literature review so as to come up with theoretical propositions that further were tested conclusively through quantitative research using factor analysis. Data for factor analysis were obtained through structured interview conducted among relevant stakeholders of the building industry (i.e. stone producers, architects, quantity surveyors, contractors, and structural engineers) operating in Nairobi.
The outputs of the study include: a profile of the business of the construction industry in Nairobi (Chapter 5), a profile of the internal structure and the external environment of artisanal stone producing units (Chapter 6) and a factor analytic model of the enabling environment of artisanal dimension stone (Chapter 7). Factor analysis that forms the conclusive part of the study has demonstrated that the enabling environment is relatively hostile. Further it has established the three levels of analysis proposed by Bertalanffy i.e. the number of system elements, the typology (variability) of system elements, and the interrelations among system elements. The study has also made certain policy recommendations in response to the hostile nature of the enabling environment: including the formation of an association by the producing unit, the formation of a marketing cooperative by the producing units and the cessation of blasting as a method of cutting rock.
