Borehole breakout and fracture analyses: Jwaneng kimberlite mine, Southern Botswana, Africa

Borehole breakouts, so named by Babcock (1978), are enlargements and elongations of a borehole in a preferential direction. These are formed by spalling of borehole fragments in a direction parallel to the minimum (least) horizontal stress. The breakouts are typically elongated in the direction of the borehole axis and can be expressed by three parameters; orientation in the borehole, the opening angle and the radial depth. Knowledge of the …