Fracture Mechanics Applications to Drilling and Blasting

Abstract

This paper gives a brief review of research in rock fracture mechanics as conducted at the Fracture and Photo-Mechanics Laboratory (FPML) at Vienna University of Technology. The mechanisms pertaining to percussion drilling and blasting are investigated, with specific reference to the application of fracture mechanics. In order to gain an improved understanding of the mechanisms controlling rock fragmentation, a multidisciplinary approach is followed which includes laboratory experiments conducted in plexiglass and rock, in-situ field experiments and analytical/numerical modelling techniques.Field experiments revealed that percussively drilled holes exhibit a very shallow region of damaged rock. An analytical model to simulate damage accumulation and crack initiation due to elastic waves generated by impacting drill bits was developed. This model, based on damage and fracture mechanics, was incorporated into a numerical finite difference code. Fracture and damage mechanics parameters are related to the moment tensor which is determined experimentally by means of acoustic emission. Small scale model blasts were used to investigate the blast-induced fractures in the near-borehole zone as well as in the far field. Analytical and numerical investigations give insight into stress wave and gas driven fracturing. The applicability of the dynamic finite difference program SWIFD to the interaction between stress waves and cracks is illustrated.

The effect of a pre‐existing crack on a running crack in brittle material under dynamic loads

“…Therefore, it was selected to make the DCSC specimens. Furthermore, the property of PMMA is similar to rock, which has been confirmed by a number of researchers …”

“…Furthermore, the property of PMMA is similar to rock, which has been confirmed by a number of researchers. [42][43][44] The DCSC specimen in Figure 1 is 325 mm in height, 200 mm in width, and 15 mm in thickness. The semicircular diameter is 75 mm, and the two crack lengths are the same 25 mm.…”

Polarization-depolarization process in glass during percussion drilling

“…Fractographic examination showed that, in addition to glass powder and a network of small cracks (Rossmanith et al 1997), some large 'chips' were formed. These are large cracks, which originated at some depth and propagated until reaching the surface of the sample.…”

A study of the impact of blast induced conditioning on leaching performance

“…Authors such as Rossmanith et al (1997), Rathore and Bhandari (2007) and Katsabanis et al (2008) have demonstrated that fracturing can be partially controlled through the application of suitable blast design parameters such as type of explosive, energy distribution and timing.…”