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Figure 2 - Concrete Cone
A concrete cone is constructed and attached to the under-surface of the load cell in the following
manner: The load cell is manufactured at Geokon so that it has threaded lugs welded to the
underside. Pieces of rebar, supplied with the load cell, are threaded at one end and are threaded
into the lugs so that they form two circles of rebars; short rebars on the outside circle and longer
ones nearer the center. A hole is excavated in the ground in the shape of the desired cone and
then it is filled with concrete. The pile tip load cell is then placed over the top of the hole so that
the rebars poke down into the concrete. After the concrete has set up then the load cell with the
concrete cone attached is welded to the bottom of the rebar cage.
Take readings of pressure and temperature at regular intervals throughout the installation
process. It should be possible to monitor the pressure of the wet concrete as it is poured.
Allow the concrete set up and cool to a temperature close to ambient. It may be observed that
there is a drop-in cell pressure from the value observed with the wet cement when the hole was
filled. Connect the cell re-inflation line to a hydraulic hand pump filled with de-aired oil and
pump oil into the cell while observing the pressure reading. The cracking pressure of the check
valve is set so that it will open at a higher pressure than the static head of oil in the re-
pressurization tube plus any suction that will be generated by the weight of the concrete attached
to the lower plate. As soon as the pressure begins to rise sharply above this value and reaches the
wet cement value then stop pumping. Disconnect the pump from the hydraulic line and cap the
end of the re-pressuring tube.