BUCKET WHEEL EXCAVATORS FOR SEMIHARD ROCK AS AN ALTERNATIVE TO BLASTING

Wherever hard rock has to be excavated as a valuable mineral or as overburden it has always been drilled and blasted. Theses procedures are expensive in time and materials, so they involve high costs. One possible way to reducing or even avoiding this high expenditure has been taken at the Mae Moh opencast lignite mine in Thailand by using a powerful bucket wheel excavator. When this opencast mine was opened up in the 70 s the solid unstratified clay rock was blasted so that it could be transported to stockpiles by heavy dumpers. The first economic improvements were made in the mid 80s by the introduction of an in-pit crushing system. This made it possible to reduce costs by transferring much of the bulk transport to conveyor belt systems. The first bucket wheel excavator has been working in the overburden since the beginning of the 90s, followed at the start of 1993 by two more machines of the same model after the cost-effectiveness of direct extraction had become rapidly apparent. The method used in Thailand can also point the way for the cement industry. For example. a compact bucket wheel excavator has been working very successfully in Teutonia Zement AG's limestone quarry in Hannover since 1991. The decision to use a bucket wheel excavator in solid rock requires extensive rock investigations. A comprehensive report is given of the special technical features of this digging equipment known as a compact bucket wheel excavator.