Two novel instrumentation systems have been responsible for the successful development of the Stress Control Technique for designing deep mine entries. The Stress Control Technique provides a method for stabilizing failing mine roofs and floors. At the same time it can greatly improve mining economy by virtually eliminating the need for roof bolting and other forms of artificial support. One of these systems is the Microcreepmeter, designed to measure the microcreep velocity distribution characteristics of underground structures so that their safety may be rapidly assessed. The other system is the Rheological Stress meter which was developed to quickly and effectively determine in situ stress conditions in both elastic and non-elastic ground. It uses a single borehole without requiring overcoring.
The Stress Control Technique was originated and established in the Saskatchewan - potash field. Over the past fifteen years, use of the technique has overcome serious roof failure and floor heave problems in these deep mines¹. It utilizes the load bearing capacity of existing ground media rather than relying upon artificial ground supports such as anchor bolts and concrete linings to support mine entries. The success of the Stress Control Technique is due to its effective use of the yield and failure properties of earth materials properties which are common to all forms of solids. In the Stress Control Technique, earth material properties are represented by rheological constitutive models of the type shown in Figure. 1. These models include elasticity, visco-elasticity, visco-plasticity, dilatancy, strength, and strength deterioration, brittle failure, and post yield behavior in terms of hydrostatic and octahedral tensors. The REM computer program has provided the basis for both the design analysis of underground openings and the analysis of instrument data. In practice, the REM program is used to project prospective behavior of an underground opening.
