Stresses around a single circular opening.

The stresses analysis for estimating the stress concentrations around a mine opening is based

on a few assumptions. These are as follows:

1. The cross section of the opening can be represented bya simple geometrical shapes,

namely, a cricle, ellipse, ovaloid, and rectgangle with rounded corners

2. The length of the opening is horizoantall and the axes of the cross section are

horizantal and vertical

3. The vertical stgress is equal to the weight of the overlying rock and thus

=

Where is the vertical stress, is unit weight of the rock formation, and Z is the

depth of consideration and the horizontal stress is assumed to be less than the vertical

stress and it is computed as follows

=1

.

= 1

horizontal stress.

4. The different types of insitu stress fields are assumed to be represented by the

following figure., where mis 0, 1/3, and 1 , representing shallow condition,

moderately deep and very deep ( where hydrostatic stress condition is assumed to be

present)

Fig Three assumed types of stress fields

Circular Openings