Anthropogenic Broken Condition of Stone in the Course of Its Extraction and Treatment

Facing products are fabricated from blocks which are extracted from the pit. At the end of the past century the main factor of violation of the stone quality is blasting works at the pit. At present, the use of explosives when extracting blocks is limited by auxiliary functions. At one of the pits for extracting granite blocks Sunset Gold located in China, the separation of a sawn block from the massif is made with the help of the stone-cutting machine and explosives “Purry Roche” produced in France. According to the measurement of the velocity of an ultrasonic impulse, the thickness of the zone of technogenic fissuring from the effect of explosives is about 50 mm, and at cutting technologies – 6–7 mm. It is established that granite details have a pronounced anisotropy according to UZI when it is absent on the blocks that is connected with the appearance of micro-fissuring due to the use of the diamond tool. This leads to reducing physical-mechanical properties of the stone of facing details by 10–15%. Ultrasound examination of slabs made of granite “Flower of Ural” shows that reducing strength properties of the stone in the course of its thermal treatment can reach 22% (GOST 30629–2012 permits not more than 20%), and the zone of such technogenic violations extends to the entire thickness of the slab (80 mm). Besides, thermal treatment reduces the abrasion index by 22.2%. The table of capacities of the zones of technogenic disturbance when treating the stone by mechanical means is presented

N.I. MOTORNY, Candidate of Sciences (Geology and Mineralogy), (This email address is being protected from spambots. You need JavaScript enabled to view it.)

Research and Design and Survey Institute for Problems of Extraction, Transport and Processing of Mineral Raw Materials in the Industry of Construction Materials (VNIPIIstromsyryo) (1 Volokolamskoye Shosse, 125080, Moscow, Russian Federation)

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