Borehole Extensometer Model WR-FLEX

The WR-FLEX borehole extensometer consists of anchors spaced along a protective plastic tube. The anchors are located at elevations where displacement measurements are required. One end of a spring-steel measuring rod is attached to the inside of each anchor. The rods extend through the protective tube and are terminated within the head assembly. The rods are free to move within the head assembly and protective plastic tube. As relative displacement between the anchors and head assembly occurs, the location of the free ends of the rods in the head assembly move the same amount. By measuring the displacement between the free ends of the head assembly, the displacement of the anchors relative to the head assembly is obtained.
Displacement can be measured either manually, using a depth gauge, or remotely, by converting the head using the elec trical head assembly and installing linear potentiometer displacement transducers. The head assembly can be installed fl ush with the rock or ground surface and can be extended at a later date, for example, through a concrete tunnel lining. Extension rods can be added to the installed rod to extend the measuring range of the extensometer. Groutable ribbed-steel anchors are used in rock and mechanical leaf-spring anchors are used in soft soils.