ABSTRACT:

The four major unit operations in mining are drilling, blasting, loading and hahling. The immediate operation that follows is crushing of ore before they are sent to the processing plant. These operations require considerable amount of energy and crushing is considered to be in excess in the energy budget as it is a secondary sizing (after primmy fi'agrmntation resulted by blasting) of ore as required by processing. To improve energy efficiency, particularly of crushing, it is very important to understand the behavior of rock under cyclic loading as it experiences one complete cycle of loading-unloading during blasting and another during crushing. This paper investigates the rock behavior under cyclic loading and presentsome pre 'hminav] data fi'om laboratory experiments on Basalt samples.

INTRODUCTION

Mining is one of the most energy intensive industries as classified by the Department of Energy. The most important unit operation in mining i.e. the fragmentation of rock mass is done by blasting. In the downstream processes, the rock f?agments resulted from blasting are crushed for efficient processing operations. Both of these processes are extremely energy intensive and need to be looked at to achieve an overall reduction in energy consumption in this energy intensive industry.

In both the occasions, rock is subjected to enormous loading and subsequent unloading to achieve the desired fragmentation during blasting or the desired size distribution during crushing. The previous studies point out a typical behavior of rock when rock is subjected to cyclic loading. Since rock is not a perfectly elastic material, it tends to retain a portion of the total deformation caused by the loading cycle when it is unloaded completely. So in a typical stressstrain curve of a loading-unloading cycle, the unloading path is always different than the loading path and it intersects the strain axis at a different point indicating retention of the portion of the total deformation caused by the loading.

This paper discusses some preliminary studies of this typical behavior of rock under cyclic loading and conceptualizes its utilization in reducing the energy consumption particularly during rock crushing that is considered as the secondary sizing procedure in the downstream processes.

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