CROSSHOLE SONIC LOGGING VERSUS PERIMETER SONIC LOGGING: WHAT HAVE WE LEARNED?

摘要

Crosshole Sonic Logging (CSL) only evaluates concrete on the inside of reinforcing cages leaving theoutside unevaluated unless other types of testing are performed such as Perimeter Sonic Logging (PSL).While there have been some reports of PSL testing having accurately identified anomalies (e.g. Samtani etal 2005), experience by Case Foundation Company has indicated otherwise where false positives weredetermined with subsequent coring. Numerous cases of PSL false positives are presented as well as a studywhere a shaft was installed with both inside and outside tubes, and CSL and PSL data were compared.To date, there is very limited data published on perimeter sonic logging, or Gamma-Gamma Logging (GGL)with tubes on the exterior of drilled shafts. Several cases will be presented where false positives wereexperienced where PSL testing was performed. In addition, a direct comparison will also be presentedwhere a shaft was installed with both tubes on the inside and outside where CSL and PSL data is compared.