CSL Defines CIDH Defects; Coring Confirms Result

Abstract

Crosshole sonic logging (CSL) is a reliable, accurate, and cost-effective quality assurance (QA) based tool to investigate the integrity of cast-in-drilled-hole (CIDH) shafts. Through implementation of a nondestructive testing (NDT), CSL program, drilled shaft integrity can be evaluated shortly after concrete placement. Potential shaft anomalies can be detected and defects can be remediated before completion of the structure. The following case history includes CSL data, concrete core logs, compressive-strength test results, and postremediation CSL data. CSL identified the locations of anomalies within tw 2.1 meter (7-foot) diameter, 20.7-meter (68 foot) long shafts that provide the foundation support for a vehicular bridge over the Muddy River in Overton, Nevada. The anomalies were subsequently confirmed as defective areas with concrete coring and laboratory testing. Early detection of the defects provided by CSL testing allowed the contractor to develop methods to mitigate the defects without drilled shaft replacement or major modifications to the bridge superstructure design. The structural engineer was able to evaluate those methods and their effects on the structure, and postremediation CSL testing in combination with construction observation and materials testing were used to assess the results of the remediation work. Detection and remediation of the defective areas before bridge completion avoided a potential structural failure and reduced the potential for future distress to the structure.