ABSTRACT: The computer program introduced in this paper is based on design guidelines developed for selection of support systems used in mine roadways. The support types considered include rock bolts as well as rigid and yieldable steel arches. Using the computer program, the design engineer can select the type, pattern and specifications of the support systems suitable for various roof conditions. The concepts utilized, assumptions made, support selection criteria and description of the computer program, developed for the PC, are included.
The main objective of the design process in mining is to devise a support system which will meet the safety requirements within economical limits. A complete design process includes three stages, namely: preliminary design stage, performance monitoring, and feedback. The computer program introduced in this paper provides outputs associated with support recommendations that can be utilized during the preliminary design stage.
Consideration of the engineering constraints and the objectives, determination of the input data, and utilization of the available design approaches are the steps involved in the preliminary design stage. The basic assumptions associated with roof and support interaction and with support loading is usually analyzed during this stage. The output specifications provided in the preliminary design stage include the suggested roof-support options, the support details and patterns, and the supplementary support needs.
Supports are essentially required for the following purposes:
to control the gravitational effect of loosened rock;
to control the envelope of fractured rock;
to transfer the high abutment pressures to the deeper zones of the rock mass.
The behavior of the strata around a roadway depends on the type of ground, size and depth of the opening, method of excavation, and the type and amount of support which is provided in the excavated opening. The support types considered in this study include rock bolts rigid steel arches, and yieldable steel arches.
Figure 1. Flow charts showing contents and main sequences of roadway-support program. (available in full paper)
The function of the rigid steel arch is to render the strata to build-up a resistance against it and finally to reach an equilibrium state. The function of the yielding arches is to control the block movement of the rock mass, but not to eliminate the lowering or convergence of the strata around the opening. With strata bolting, however, an opposite situation is aimed; namely, the competence of strata is desired and given the rock mass a choice to support itself. In this study, the supporting action was assumed to be provided by the roof arch, transferring the major portion of the strata pressure to the sides of the opening and by the rock bolts carrying (by suspension) the weight of the rock arch plus the portion of the rock load actively transferred on this arch. The total load that should be carried by rock bolts is defined by rock-load height equation given in this paper.