An investigation into the effect of joint frequency and spatial positioning on pre-splitting

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:400834

Tariq, S M; Worsey, P N ^[1]

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1. Univ. of Missouri, Rolla, MO (United States)

Pre-splitting is now widely used to minimize overbreak and to protect final surface rock excavation profiles in large scale civil construction projects, open pit mining and quarrying. Jointing has been shown to affect the success of pre-splitting and the smoothness and integrity of the resulting rock face. Many facets of jointing have been investigated in detail, including the inclination of joints with respect to the desired pre-split plane, the effects of various filling materials, etc. However, the effects of joint frequency and spatial positioning has been paid little attention. The paper addresses this issue. The results of experimental model testing carried out in concrete blocks are presented. The program consisted of modeling closed joints with varying frequency between two 3/8 inch boreholes, drilled in 12 x 9 x 6 inch concrete blocks charged with 15 grains per foot PETN cord. It was found that by increasing the joint frequency from zero to two between boreholes decreases the maximum successful split-hole spacing. However, with increasing joint frequency the trend is reversed. These results are attributed to the overall rock mass being weakened by the slabs between the discontinuities becoming thinner with increasing discontinuity frequency. It was also revealed that the spatial positioning of discontinuities plays an important role in pre-split formation and integrity.

• OSTI ID: 400834
• Report Number(s): CONF-950247--
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
42 ENGINEERING
BOREHOLES
DESIGN
DISTRIBUTION
EXPLOSIVE FRACTURING
GEOLOGIC FISSURES
POSITIONING
PROCESS CONTROL
SCALE MODELS
SURFACE MINING