Laser Based Roughness Measurement for Design and Verification of Rock Socketed Piles

The importance of socket roughness to side resistance development in rock socketed piles has been well established. Roughness levels have been observed to vary considerably with rock strength, rock fabric, and drilling technique. The corresponding variability in the ultimate side resistance which is mobilised along a pile can be significant in magnitude. Recent advances in rock socket design methodology allow the effect of socket roughness to be routinely evaluated and incorporated in pile design. In order to effectively use a design method incorporating socket roughness, a prediction of the level of roughness which will be produced during construction must be made. Verification of assumed socket roughness parameters during construction is also necessary. The current understanding of socket roughness production is poor because of a shortage of data. This is primarily due to the difficulties associated with roughness measurement in the field. In order to allow a widespread investigation of socket roughness, a laser based socket profiler has been developed. Known as the Socket-Pro, this device is able to quickly and accurately record the sidewall profile of a borehole with minimal disruption to construction activities. The capabilities and operation of the Socket-Pro are described, and the application of a laser distance sensor to roughness measurement is discussed. The Socket-Pro is being deployed on a range of construction projects for roughness verification and data gathering which will allow the development of roughness guidelines for use in design.