Abstract: A new method for the determining the thickness of drilling debris at the bottom of the cast-in-place reinforced concrete pile boreholes is proposed combined with testing practice in this paper. Based on the borehole drilling inspection, this device can visually reproduce the interface conditions of the “pile-end concrete-drilling debris layer of rock or soil” at the bottom of the borehole by using borehole imaging technology. Thus, image analysis technique can be applied to accurately measure the drilling debris thickness at the bottom of the drilled pile. Through expanding the cylindrical imaging of the borehole to a panoramic plane, the operator can directly measure the drilling debris thickness under the side wall corresponding to various azimuth angles. “N equal-point average” and “integral average” algorithms are recommended to achieve the representative drilling debris thicknessat pile bottom, which can be used to evaluate whether it meets the design requirement.According to on-site tests of 10 large-diameter rock-socketed cast-in-place piles form different projects, the drilling debris thicknessobtained by this new method is proved to have the advantages ofaccurate,reliable and simple operated.

Key words: Borehole, Imaging Technologies, Thickness of Drilling Debris