Analysis of Roof Bolting Systems Based on Model Studies

Most roof bolts are used in mines with bedded roofs, but it has not been determined to what degree thin-bedded roofs can be reinforced by bolting if there is no thick member in which to anchor the bolts, or what function the bolts must perform in such a case. Owing to widespread practice of systematic bolting to support thin-bedded roofs, moreover, it is desirable to design roof-bolting systems on a quantitative basis. Specifically, a solution to the following problem is required: For a roof composed of beds of given thickness and physical properties, what is the optimum length, spacing, orientation, and tightness of bolts consistent with safety and economy? The investigation reviewed here has produced a functional equation to evaluate these variables and establish basic principles of roof bolting.