Predicting the average size of blasted rocks in aggregate quarries using artificial neural networks

The prediction of the average size of fragments in blasted rock piles produced after blasting in aggregate quarries is essential for decresing the cost of crushing and secondary breaking. There are several conventional and advanced processes to estimate the size of blasted rocks. Among these, the empirical prediction of the expected fragmentation in most cases is carried out by Kuznetsov’s equation (Sov Min Sci 9:144–148, 1973), modified by Lilly (1986) and Cunningham (1987). The present research focuses on the effect of the engineering geological factors and blasting process on the blasted fragments using a more powerful, advanced computational tool, an artificial neural network. In particular, the blast database consists of the blastability index of limestone on the pit face, the quantities of the explosives and of the blasted rock pile, assessing the interaction of these parameters on the blasted rocks. The data were collected from two aggregate quarries, Drymos and Tagarades, near Thessaloniki, in the Central Macedonia region of Greece. This approach indicates significant performance stability, providing the fragmentation size with high accuracy.

     

Décroissance de la perméabilité dans des roches cristallines en fonction de la profondeur d’après des données d’Elassona (Grèce)

In crystalline rocks of Elassona area (Greece) 31 exploration drillings were constructed, for engineering purposes. Water injection tests allowed us to calculate the permeability coefficient K (m/sec) for every 3 meters of depth. The permeability values, which were determined, decrease in relation to the depth. The decrease of the mean values of K, in relation to the depth was expressed by an exponential regression, with a correlation of high significance. However the standard deviation σ of K, (at the same depth) is large and the changes of the variation coefficient V are independant of the depth.     

Non destructive methods for investigation of some mechanical properties of natural stones in the protection of monuments

The investigation of the physical and mechanical properties of stones in monuments needs non-destructive methods and small quantity of testing material. The non-destructive methods can be divided into laboratory andin situ techniques. P P S wave ultrasonic velocities and Schmidt hammer can be used for bothin situ and laboratory measurements, in contrast to the mechanical resonance frequency and abrasion resistance that can be used only for investigation in the laboratory. In the present paper the above methods were used for the study of properties such as mechanical anisotropy, weathering degree, mechanical strength and deformation ability of stones, using data from Italy, France, Malta and Pacific Ocean.     

Méthode d'évaluation de l'altération et modification des propriétés mécaniques des granites en Grèce du Nord

The effects of weathering on the mechanical behaviour of different granites from Northern Greece are investigated and a mathematical expression of these relations, is given. The collected samples are examined mineralogically by means of polarized microscope and their weathering degree is estimated by means of point counter method. Then the physical features of the rocks (bulk specific gravity, water absorption, ultra-sonic velocity) as well as the mechanical properties (compressive strength, tensile strength, angle of shearing resistance) are determined. Diagrams showing the change of the physical and mechanical behaviour in relation to its weathering degree is given in relative mathematical expressions.     

Durability of building stones and weathering of antiquities in creta/greece

In the present investigation building stones from the archaeological sites of Knossos, Festos and Malia in Creta are studied with regard to their weathering condition and to some of their physical and mechanical properties. For this purpose studies were made of: a) the mineralogy with a semi-quantitative composition of the materials by microscopic and X ray diffraction methods, and in situ observations b) the weathering condition either under the microscope or with ultra-sonic velocity measurements c) weathering resistance by salt crystallisation methods d) dry density and water absorption and e) unaxial compressive strength. All test results were interpreted statistically and the relationships were expressed mathematically: correlation diagrams are also given.     

Slope stability problems in the area between St. George and St. Herene villages and their significance for the main road Argostoli–Poros on Kefallonia Island, Greece

The serious landslide phenomena manifested between St. George and St. Herene villages and affecting the main road on Kefallonia Island are reported. The site investigation included four sampling boreholes and a series of slope stability analyses. The data obtained provided further information on the geotechnical–geomechanical characteristics of the Neogene bedrock and assisted in the determination of the causes of the instability. Measures are suggested to avoid a re-occurrence of such failures. Electronic Publication     

Technological characteristics of the calcined limestone from Agios Panteleimonas, Macedonia, Greece

The gray-green limestone from Agios Panteleimonas is studied in this paper after submitting it in special technological analyses in order to determine the possibility for quicklime production. Cubic test specimens with mean 50 mm edge length were calcined at 850, 950 and 1,050°C, with 150 min preheating time and 120 min retention time at each calcination temperature. At the dissociation temperature of pure calcite (898°C) only one half of the initial limestone has been calcined. The dissociation of the specimens started at 740°C and almost completed at 1,050°C. Probably, the large edge length of the cubic specimens and the low retention time are responsible for the incomplete calcination at 1,050°C. The dry apparent weight of the calcined lime-stone (1.577 g/cm³), its low shrinkage (0.1–0.3%), the 2% impurities content and the 24% value of the attrition and abrasion resistance, characterize this quicklime and classify it to the high quality products.     

Determination of the moduli of elasticity of rocks. Comparison of the ultrasonic velocity and mechanical resonance frequency methods with direct static methods

In the present investigation, dynamic methods for the determination of moduli of elasticity were compared with direct static methods. The dynamic moduli of rocks, such as Young's modulus (E) and Poisson's ratio (v) were determined, using both mechanical resonance frequency and classic P and S wave ultrasonic velocity techniques. For this purpose rock samples from different areas of France, covering a wide range of velocity values, were used. The mechanical resonance frequencies were investigated using a Grindo-Sonic machine while the P and S wave ultrasonic velocities were measured using a Pundit ultrasonic machine, connected to an oscilloscope. The static moduli were determined using deformation gauges. Statistical interpretation of the test results indicated significant correlation between these dynamic and static methods. Accordingly, the above non-destructive dynamic methods are suitable for the determination of static moduli of elasticity.

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Resume Dans la présente étude, les méthodes de détermination du module d'élasticité dynamique sont comparées aux méthodes de calcul statique direct. Les modules d'élasticité dynamique des roches tels que le module de Young (E) et le coefficient de Poisson sont déterminés en utilisant à la fois une méthode de résonance en fréquence et la méthode classique de mesure de la vitesse des ondes P et S. Pour cette recherche, différentes roches de France, couvrant un large éventail de vitesses des ondes, ont été choisies, la méthode de résonance en fréquence a été établie en utilisant un appareil Grindo-Sonic, tandis que pour la mesure des ondes P et S, nous avons utilisé un Pundit et les lectures ont été effectuées sur un oscilloscope. Le module d'élasticité statique a été déterminé en utilisant des jauges de contrainte. L'interprétation statistique des essais fournit une bonne corrélation entre les méthodes dynamiques et statiques utilisées. En accord avec nos recherches, le module d'élasticité statique peut être déterminé avec une bonne approximation en utilisant des méthodes dynamiques non destructives.