RMZ – MATERIALI IN GEOOKOLJE

Izbira tehnološkega procesa in opreme za pridobivanje naravnega kamna ...431Until a few decades ago, the exploitationof stone was based on makinguse of its natural properties, mainlythe cracks which were used for breakingthe stone into smaller pieces. Allworks were done on the surface,manually, with primitive tools suchas mallets, chisels, picks and varioussimple levers. The pieces of stoneappearing on the surface were carvedby picks and mallets until they broke.The work was long-lasting and strenuous.A true revolution in the quarry workwas brought about by boring drills. Thework was still manual. Natural featuresof sites were exploited. In winter, peoplepoured water in cracks. Freezingwater expanded the cracks and madebreaking of stone easier. Hazelnut rodsand oak wedges were also used; theywere hammered into cracks and moistenedwith water. [2]The development of pneumatic drillingtools additionally changed andincreased the production. Using pneumaticdrilling equipment, people drilledunder and around the rock mass whichwas then split into smaller blocks bymeans of wedges and heavy mallets. Inmost cases, they made use of naturalfeatures of the sites (discontinuities,stratification, etc.), but they also usedvarious emulsions, gunpowder anddetonating cord to split the rock massapart. [3]The development of quarry equipmentcontinued with helicoid wireand quartz sand. This method was firstused in the year 1854. In our country,it continued to be used by mid-1980s.At cutting sites, vertical bores with adiameter of 240 mm and 360 mm andhorizontal bores with a diameter of 90mm were first drilled. A 5.8 mm helicoidwire was threaded through thebores and used, together with quartzsand, for cutting of stone. An engineroom with a diesel aggregate was requiredfor the start-up. Water was usedas an additive and a coolant. The cuttingefficiency was low, amounting to1.5 m 2 /h to 2.0 m 2 /h, depending on thehardness of the stone. The length of thewire system line was sometimes up to2.5 km. [2] In the present time, helicoidwire has been replaced by diamondwire.A new revolution in quarry mining wasintroduction of diamond wire saw. Thefirst diamond wire saws came into operationin the 1970s. The cutting processis similar to the preceding technology;i.e. a combined method withpreviously drilled bores (34–90 mm indiameter) and diamond wire saw. Thespeed of cutting ranged from 8 m 2 /h to12 m 2 /h, which meant new possibilitiesin exploitation and processing of naturalstone. In the beginning, diamondwire saws with 30 kW (40 hp) motorswere used, which allowed cuttingof surfaces of up to 150 m 2 . [2] Today,RMZ-M&G 2012, 59