Proceedings of the 37th Annual Conference on Deep Foundations, 2012, Houston, TX, USA, (DFI)
Uncertainties in CSL Test Interpretations and Recommendations toward a More Efficient Process
Mark A. Rohrbach, Timothy R. Kovacs, Fadzilah (Dila) Saidin
Crosshole Sonic Logging (CSL) testing is commonly used to verify the integrity, quality and ultimately the acceptability of the concrete in structural elements such as drilled shaft foundations, secant pile cutoff walls, and secant/tangent pile earth retention structures. Besides concrete quality, many factors can impact CSL test results (e.g. laitance, air temperature, access tube spacing, access tube debonding, etc.). Effective use of CSL testing requires fully informed qualified practitioners capable of distinguishing between abnormal readings unrelated to deficiencies in the drilled shaft concrete and similar readings indicating the presence or possible presence of drilled shaft defects. Based on data and experience gathered from CSL testing of thousands of drilled shafts across North America, this paper discusses such factors and other information useful when evaluating CSL test results, and provides practical recommendations intended to reduce the potential for incorrect test data interpretation. The CSL testing industry is lacking in a clear, universally accepted guideline for the interpretation of CSL data and acceptance criteria of these concrete elements. This paper proposes terminology and a streamlined process for use when atypical results are obtained. The proposed terminology and method are intended to simplify and expedite the submittal review and approval process. Because construction activities for these elements are often on the projectís critical path, the benefits obtained in terms of project savings and reducing costly delays are undoubtedly valule.
|article #1874; publication #99 (AM-2012)|