Borehole Inclination Testing (Piletest BIT)

Borehole inclination testing (BIT) measures the verticality of a borehole and its existing piles. BIT uses the auger/bucket itself as a centraliser. This results in the elimination of a heavy to move system. The BIT enables fast and accurate determination of inclination in both dry and wet boreholes. Large boreholes and diaphragm walls can be quickly tested several times during drilling. This allows for real time corrective action while drilling. When testing existing piles, a special centraliser attached to the BIT sensor and lowered into a standard access tube. Importantly, this cuts out the need for expensive inclinometer tubes. The BIT sensor includes a gyro which constantly measures and compensates the rotation of the sensor in the tube.

BIT testing is important as all piling specifications prescribe the allowable deviation of the pile axis from the vertical.

  • FHWA rules, for instance, limit the pile inclination to 20 mm/m, or 2%.
  • The ICE (UK) specifications allow a deviation of not more than 1:75 or 1.33%.

Similarly, these documents also set down the allowable deviation of raked piles. In diaphragm and secant walls, the specification is typically even more restrictive.