Blast design for fragmentation of anisotropic rock mass in surface mines
- Visvesvaraya Regional Coll. of Engineering, Nagpur (India). Dept. of Mining Engineering
Joints, fractures and other structural defects bring anisotropic character into a rock mass. Conventional methods of blast design in a rock mass consisting phyllites, mica schist etc., which are characterized by the presence of closely spaced, nearly vertical planar joints, result in formation of large slabs which cannot be handled by the excavation and loading equipment without resorting to secondary blasting. Frequent secondary blasting is not only expensive but also, is a source of environmental hazard. Interruption of production cycles frequently leads to uneconomical mining. This problem could be minimized by designing blasts which produce forces whose components along and across the joints/fracture planes is just sufficient to break the rock mass in both directions. Rock mass strength can be assessed from field and laboratory tests. Projecting structural features with respect to bench orientation on a stereoplot helps in assessing magnitude and direction of force vectors required to fragment the rock mass to the desired size range. Also, any restraint that may be necessary on the free faces of the blasts, to control the tensile strain, can be introduced by selectively leaving a portion of the fragmented rockmass from the previous blast along the free face. This paper describes a procedure for use of stereographic projection of joint, fracture and slip planes to determine the optimum dip and dip direction of blast holes required to break the anisotropic rock mass into fragments of suitable size. A case study including photographic illustrations is included for greater detail.
- OSTI ID:
- 398358
- Report Number(s):
- CONF-9502142--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Field investigations into blast design parameters of highly jointed rockmass of overburden: A case study of large opencast coal mine (India)
The effects of rock mass characteristics on fragmentation in controlled blasting experiments in small development headings