1,875 research outputs found
Petrophysical and technical properties of dimensional stones: a statistical approach
No full textThe efficient use of natural building stone is immediately connected with the cost-intensive investigation of technical properties of a rock, considering different standardizations. Hence, there are number of paper in the literature dealing with the extrapolation of technical parameters (e.g. compressive strength) based on easily ascertainable properties, like density or porosity. Consequently, well-founded statistical analyses about corresponding prognostic feasibilities as partial alternatives to laboratory analyses may be of great economical interest. The presented statistical analyses are based on a dataset, including around 2100 commercial grades of dimensional stones from more than 70 countries. Specific features in technical behaviour of single varieties, peculiar to any particular small datasets due to e.g. location details or laboratory conditions, could be eliminate as far as possible. The statistical behaviour in the different correlations between the basic parameters density and porosity, respectively, with the parameters of strength is described broadly for the main rock types (plutonic rocks, volcanic rocks, elastic sediments, carbonatic rocks, metamorphic rocks). Based on this, detailed examinations of the different interrelations are given exemplary for the plutonic and carbonatic rocks as well as the elastic sediments. In addition different approaches of regression analysis are evaluated. Furthermore the calculation of confidence regions gives a significant tool to visualize the theoretical population of the connection of two parameters. Finally the interrelations between the petrophysical/technical parameters and the ultrasonic wave velocity, as a non-destructive method for material examination, are specified
Optimized extraction of dimension stone blocks
No full textThe profitable production of dimension stone mainly depends on the extractable block size. The regularity and volume of the blocks are of critical importance, and are controlled by the three-dimensional pattern of the discontinuity system. Therefore, optimization of block size has to be the aim when quarrying for natural stone. This is mainly connected to the quantification of joints and fractures, i.e., their spacing and orientation. The problem of finding unfractured blocks within arbitrarily oriented and distributed planes can be solved effectively by a numerical algorithm. The main effects of joint orientations on block sizes and shapes will be presented in this article. Quantification of unfractured blocks with the aim of optimization is illustrated by detailed studies on several quarries. The algorithm used in this study can be applied as a powerful tool in the planning of a quarry and the future exploitation of dimension stone. Application of the described approach is demonstrated on practical examples of quarrying natural stones, namely, sandstone, granite, rhyolite, etc. Block quarrying can be optimized by using the new 3D-BlockExpert approach. The quantification of unfractured rock masses is also shown to contribute to a more ecological protection and the sustainable use of natural resources
Modell-based prediction of unfractured rock masses
No full textProfitable dimensional stone production mainly depends on the effective number of extracted blocks with a predefined size. The regularity and volume of the blocks are of critical importance. Optimization of the defined block size is therefore the most economically important task in quarrying of natural building stone. This problem is mainly connected to the quantification of joints and fractures, i.e. their spacing and orientation, since these tectonic elements affect the fragmentation of a deposit generating several blocks, not necessarily cubic in form. The problem of detecting unfractured blocks within arbitrary oriented and distributed planes (e.g. joints) cannot be solved analytically, but only effective through numerical analysis. In this article we present a brief description of a new computer program based on a numerical algorithm. The program determines the distribution, the individual shapes, and volumes of in-situ blocks. The quantification of the blocks is illustrated by a number of model examples and detailed studies of quarries, which help to demonstrate that the application of the computer program could be a powerful tool for the future in exploiting dimensional stones
Dimensional stones in Argentina
No full textDimensional stone material for use in constructions and monuments is common worldwide and can be traced back to the dawn of human civilization. During the last three decades the market for dimensional stones has grown rapidly, which is connected to the demand for high-quality material. Every ten years a duplication of the accession rate can be assumed in the use of ornamental rocks. Between 1998 and 2002 the Argentine industry passed through a deep economic slump. Although the dimensional stone sector has also been affected, a light continuous rebound can be recognized, which began at the end of 2002. Like other South American countries, Argentina has a large resource potential in regards to dimensional stones, due to its multifaceted geological origin. Reopening closed quarries would be advisable, because the resources can be more efficiently exploited using modem-day extraction techniques. An overview on the inventory of dimensional stones and the corresponding commercial grades in Argentina are outlined in this study. The investigation includes the unique rocks known worldwide, rocks which show a high variability in structure and colour, as well as rocks that are generally in demand at the international market. For the different commercial grades brief descriptions of lithology, quarry situation as well as variations in colour and decor, and the petrophysical and mechanical properties of the rocks are presented
The bowing potential of granitic rocks: rock fabrics, thermal properties and residual strain
No full textThe bowing of natural stone panels is especially known for marble slabs. The bowing of granite is mainly known from tombstones in subtropical humid climate. Field inspections in combination with laboratory investigations with respect to the thermal expansion and the bowing potential was performed on two different granitoids (Cezlak granodiorite and Flossenburg granite) which differ in the composition and rock fabrics. In addition, to describe and explain the effect of bowing of granitoid facade panels, neutron time-of-flight diffraction was applied to determine residual macro- and microstrain. The measurements were combined with investigations of the crystallographic preferred orientation of quartz and biotite. Both samples show a significant bowing as a function of panel thickness and destination temperature. In comparison to marbles the effect of bowing is more pronounced in granitoids at temperatures of 120 degrees C. The bowing as well as the thermal expansion of the Cezlak sample is also anisotropic with respect to the rock fabrics. A quantitative estimate was performed based on the observed textures. The effect of the locked-in stresses may also have a control on the bowing together with the thermal stresses related to the different volume expansion of the rock-forming minerals.BMBF [03-DU03X4, 03-DU03G1
Ask questions, get sales : close the deak and create long-term relationships / Stephan Schiffman.
No full textIncludes index.v, 168 pages ;In Ask Questions, Get Sales, the author and sales guru Stephan Schiffman helps readers boost their careers to the gold-medal level by teaching them how to strengthen their questioning skills during the sales process. The premise is simple yet effective: In order to be successful, salespeople need to change their mindset from "need-orientated" to "do-orientated". The message of the book centers around six core "do" questions: What do you do? How do you do it? When and where do you do it? Why do you do it that way? Who do you do it with? How can we help you do it better? With this indispensable guide in their briefcase, salespeople will have information at the ready to score big sales over the short term and the long term
Stability assessment of sandstones from the St. Servatius Church in Quedlinburg (UNESCO's World Heritage Site, Germany)
No full textThe St. Servatius Church in Quedlinburg (UNESCO's World Heritage Site, Germany) is characterised by long-standing stability problems and structural damages, which have been known over the last several centuries. The monotonous Cretaceous sandstone with its poor lithification is considered to be the main factor. The sandstone is characterised by a high porosity of around 30 Vol.% (max. ca. 35 Vol.%) and a corresponding high w-value. The porosity and the degree of cementation are responsible for the very low compressive strength of around 8 MPa at maximum, whereas under moisture these values are significantly reduced up to 40%. The freeze-thaw tests indicate a very poor resistance to frost weathering, which may explain the near-surface softening of the sandstone. Direct shear experiments with an approximate 60A degrees angle of friction on the sandstone clearly demonstrate the safety margins. Initial geotechnical modelling does not favour the hypothesis that a landslide of the hill parallel to the southward dipping bedding planes (i.e. shear failure along weak zones) can occur. A prominent clay layer (also with a southward dip) below the entire castle hill is monitored to determine the possible amount of movement with respect to the geological discontinuities (e.g. joints, fractures). At present, a combination of foundation problems are being considered for the stability situation at the church. These include construction deficiencies due to deformation or softening of the foundation of the forerunner churches and missing or faulty connections from building additions. Geological factors responsible for the stability problems include the softening of the sandstone by the influence of weathering and penetrating water as well as the presence of possible shear planes and joints
Unemployment Benefits and Unemployment Rates of Low-Skilled and Elder Workers in West Germany: A Search Equilibrium Approach
No full textApproach Author & abstract Download 16 References 1 Citations Related works & more Corrections Author Listed: Launov, Andrey ([email protected]) (University of Kent) Wolff, Joachim ([email protected]) (Institute for Employment Research (IAB), Nuremberg) Klasen, Stephan ([email protected]) (University of Göttingen) Registered: Stephan Klasen Abstract In this paper we investigate whether the extension of the entitlement to unemployment benefits in the mid 80s can explain the increase in the unemployment rates of unskilled and elder workers in western Germany. To answer this question we estimate a version of the Burdett-Mortensen search equilibrium model and analyze how workers’ search behaviour responded to these reforms. We try both nonparametric and fully-parametric estimation methods and identify the cases in which the nonparametric approach cannot be applied. We find that the entitlement reforms are largely responsible for the increase of unemployment among unskilled workers
Unemployment Benefits and Unemployment Rates of Low-Skilled and Elder Workers in West Germany: A Search Equilibrium Approach
No full textApproach Author & abstract Download 16 References 1 Citations Related works & more Corrections Author Listed: Launov, Andrey ([email protected]) (University of Kent) Wolff, Joachim ([email protected]) (Institute for Employment Research (IAB), Nuremberg) Klasen, Stephan ([email protected]) (University of Göttingen) Registered: Stephan Klasen Abstract In this paper we investigate whether the extension of the entitlement to unemployment benefits in the mid 80s can explain the increase in the unemployment rates of unskilled and elder workers in western Germany. To answer this question we estimate a version of the Burdett-Mortensen search equilibrium model and analyze how workers’ search behaviour responded to these reforms. We try both nonparametric and fully-parametric estimation methods and identify the cases in which the nonparametric approach cannot be applied. We find that the entitlement reforms are largely responsible for the increase of unemployment among unskilled workers
Anisotropic behaviour of White Macael marble used in the Alhambra of Granada (Spain) The role of thermohydric expansion in stone durability
No full textOne of the most commonly used marbles in Spain is "White Macael" marble, quarried in the Macael area of Almeria. Throughout Spanish history, White Macael has been in great demand as an ornamental stone and was used to build pieces of great importance and artistic beauty, such as the Fountain of Lions in the Alhambra (Granada). Over the centuries, such pieces have suffered from decay due to exposure to the elements, as has happened in many other marbles all over the world. The main purpose of this paper was to determine the durability of White Macael marble when subjected to changes in thermal conditions. It was observed that these changes in the presence of humidity were an important factor in marble decay. They produce a progressive loss of cohesion along grain boundaries and an increase in porosity, which are starting points for marble degradation and facilitate the development of other pathologies. (C) 2009 Elsevier B.V. All rights reserved.FQM [1635, HA 2007-0012]; Junta de Andalucia RNM [179
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