An important part of bored pile/drilled shaft construction is the cleaning and inspection of the bottom of the hole for cleanliness prior to the placement of reinforcement and concrete. Once drilling is complete, any material unsuitable for end-bearing support is removed. Bottom inspection is then performed, often by lowering a camera down the borehole, a procedure that gives a rough idea of the thickness of any debris left at the bottom.
SQUID assesses cleanliness by measuring the thickness of the debris or non-competent material remaining at the shaft base, and can also provide a quantitative evaluation of the strength of the bearing layer.
A drill stub column adaptor allows for a quick pinned connection to the kelly bar of any drill rig; the rig itself lowers the SQUID body to the base of the shaft. The SQUID body includes three retractable contact plates attached to displacement transducers, and one instrumented cone penetrometer for each contact plate.
The penetrometer cones move through the debris layer and into the bearing material under the weight of the kelly bar and measure pressure, while the transducers measure displacement. The SQUID body connects by cable to a wireless transmitter at the edge of the borehole; the transmitter sends pressure and displacement data to the SQUID tablet.
The wireless data transmission to the tablet - where data is visualised - allows for the person holding it to be positioned at a safe distance from the borehole. The tablet displays, among other information, the depth of the non-competent layer and the maximum penetrometer cone tip pressure.