ABSTRACT
Friction Rock Stabilizers were invented by the author in 1973 and, in cooperation with Ingersoll-Rand Co., were developed and introduced to the mining industry in 1977. This radically new concept of interior rock reinforcement has been widely accepted by the mining and construction industry both in the United States of America and in the rest of the world. Approximately 25 million fixtures have been used.
This paper will cover the past history of interior rock reinforcement with the most commonly used rock anchors described. Emphasis will be placed upon the interaction and compatbility of the anchor device as it relates to the geologic deformation of the host rock mass. The rock anchor fixture must have a modulus of elasticity which is compatible with the rock deformation or a mismatch will occur which will cause a breakdown at the rock/anchor interface. It is possible to produce the desired yield in a rock fixture to match the yield in the rock by changing its geometry by doing such things as limiting the anchor length along the fixture. The success of combination roof bolts in controlling severe ground conditions in American coal mines is an example of this practice.
When it is not possible to match the modulus of the anchor to the modulus of the rock a stick-slip interface may be used to allow slippage of the fixture which prevents overloading of the anchor rod and serves to match the yield of the rock. In the case of the Friction Rock Stabilizer and the Swellex anchor system, radial loading along the axis of the borehole occurs. This mechanism can stiffen the geologic structure which reduces deformations and enhances stability.
Case histories will be presented which will support the theories put forth in this paper in regard to the manner in which various interior rock support systems function. Field examples will be cited. Friction Rock Stabilizers and wire mesh have been substituted for heavy steel and timber supports with total cost of support being reduced 70%. Examples will be cited where Friction Rock Stabilizers have been used in undercuts of block caving mines and development headings and stopes of uranium mines. They have also been used as initial support to be followed by concrete in the deepest vertical shaft in North America and in railroad and water tunnels in Australia and Canada.
The Friction Rock Stabilizer is a low initial anchorage ground control fixture which provides the utmost in compatbility between the steel of the anchor and the deformation of the rock. Anchorage increases with time and with rock movement so that anchorage is enhanced at the time it is most needed. It is a truly intelligent roof support system. It is the author’s hope that this paper will serve to inspire others to develop new rock anchor systems which will use the principles of the Friction Rock Stabilizer in new and unique ways.
