Terminology and Evaluation Criteria of Crosshole Sonic Logging (CSL) as applied to Deep Foundations

Nondestructive testing of drilled shaft foundations via Crosshole Sonic Logging (CSL) is often performed as part of the quality assurance process to assess the soundness of concrete. The intent of CSL testing is to identify irregularities such as soil intrusion, necking, soft bottom, segregation, voids and other defects that could result in poor structural performance of the foundation. Over time, CSL rating criteria based on first arrival time and relative energy have incorrectly evolved to often be the sole means of determining the acceptability of a shaft. Some of these criteria have found their way into regulatory agency specifications, with acceptance values often differing from agency to agency.The purpose of this document is to review the state of the practice (including experience gained over the past 20 years), propose improved CSL rating criteria and make recommendations for additional assessment, as well as educate the industry on the proper interpretation of CSL test. CSL test results alone should not be the sole means of rejecting or accepting a shaft. A task force of industry exerts was formed to review the existing CSL rating criteria and propose improvements where appropriate. The recommendations presented herein are the consensus of the task force, which believes that they should be incorporated into future criteria, codes and specifications. This paper was produced as a joint effort between the Codes and Standards Committee, the Drilled Shafts Committee and Testing and Evaluation Committee. A task force was authorized under Testing and Evaluation Committee. The task force contributed their expertise in web-based discussions often every two weeks over a period of three years. Interested participants were invited to participate at any time. The document had two rounds of broad industry review, two rounds of DFI Technical Advisory Committee reviews, and a Public Comments process. All comments were considered in producing the final document.