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The Goodman Jack consists of a hydraulic jack with curved
bearing plates, LVDT sensors, a displacement indicator, a hydraulic pump
with pressure gauge, hydraulic hose, electrical cable, and a coupler for
drill rod.
The jack is attached to drill rod and inserted into the
borehole. A hand pump is used to create hydraulic pressure in the lines
connected to the jack, which in turn activates the pistons and produces a
uniform and unidirectional stress field at the bearing plate. The applied
hydraulic pressure is measured with a standard Bourdon-type pressure gauge.
The deformation of the rock is measured by two linear variable differential
transformers (LVDT) and data are displayed by the indicator at the surface.
After the test, the bearing plates are retracted by reversed pistons and the
jack is withdrawn from the borehole.
The modulus of deformation is calculated using formulae
derived empirically from in-situ testing and correction factors that were
developed by laboratory testing.
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