Before the advent of the present day man equilibrium conditions had been established in many phases of nature. One of the phases which had reached this equilibrium condition was the coal and mineral deposits. As they stand, the stresses acting on coal and mineral deposits are in equilibrium,—any underground mining operation upsets this equilibrium. Shocks due to the unbalancing of stresses often time cause catastrophic roof-falls which kill and injure miners and damage equipment. Attempts are made to control these unbalanced stresses by choosing the proper method of mining and suitable method of roof support.

About 20 years ago, the St. Joseph Lead Company in Missouri, in an attempt to get away from the awkward, bulky and expensive method of supporting roof by timber or steel and concrete, tried a new method of roof support.⁽¹⁷⁾ The new method was named “roof-bolting”. As the name implies, the lower exposed strata of the roof are bolted to the stronger less exposed strata above the mine opening. This new method has been used more and more in the past three years. At the present time over 200 companies are using this method of roof support.⁽¹⁶⁾

The roof bolting method of roof support has presented many problems which have to be solved before definite procedure for its use can be established. Some of these problems are:

1. How long should the bolt be.

2. At what angle should the bolt be inserted.

3. What should be the longitudinal and transverse center-to-center distance between the bolts.

4. What stress should be applied to the bolt when installed.

5. How often should the bolt be retightened.

This thesis will be an attempt to solve some of these problems.