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1. Choose anchor site carefully. Rock anchors will only perform effectively in solid competent rock (Class 0 Soil).

"Proper alignment" and "down pressure" are simple phrases to summarize proper anchor installation technique. The Power Installed Screw Anchor (PISA®) wrench transmits torque from the digger’s Kelly bar to the anchor hub. Note: The anchor rod only has to be of sufficient diameter to support the guy load.

It is essential to use installing tools and anchors that are properly rated for trucks during the installation of power-installed screw anchors (PISA®). The high torque energy used in installing high-strength anchors requires the control of hazardous torque, which can be safely completed by proper tools. 

The CHANCE® grouted rock anchor is designed to be used in situations where the soil is too rocky to use screw anchors, and the rock is fractured preventing the use of wedge style rock anchors. The forged knob on the end of the anchor along with any extension couplings provides the interference fit with the grout. The holding capacity of the anchor is dependent on the bond stress between the rock and the grout. The grouted rock anchor is designed to be used in line with the guy. Failure to install within 5° of alignment with the guy load will significantly lower strength.

Historical Analysis

During the early development of the screw anchor, the load resistance of an installed anchor could not be predicted with adequate accuracy. Specific information on soil conditions was lacking, making anchor selection more or less a guess. With little consideration for soil variations, the effects of seasonal weather changes or drainage, soils were classified as: either sand, clay, hardpan or swamp. At that time, there was not a definitive explanation for the soil conditions.