CROSSHOLE SONIC LOGGING - CSL

Integrity testing of concrete piles by ultrasonic crosshole logging

Variations in the concrete in deep and setup even in locations with The transducers consist of a 25 foundation piles and concrete limited access. mm diameter piezo ceramic emit- walls can be determined by using ter probe and a 25 mm diameter a crosshole sonic logging system. The logging unit is a rugged note- receiver probe. These transducers book that handles all the incoming are connected to an emitter and a data. Furthermore, the logging receiver cable, accordingly. unit supplies the entire system with power for up to 8 hours. If Software more is needed the system can The intuitive software enables the run on external power from either production of complete pile data a car charger or generator. sheets which show references to tube top level, tube toe level, The electronic winch unit displays calculated tube lengths, tested depth, amplitude and profile ref- lengths of each profile, pile cut-off erence. From the winch it is pos- level, pile toe level and the com- sible to reset depth and change plete profiles of each test includ- profile reference for fast opera- ing first arrival time and energy. tion. On these profiles it is possible to add potential changes in first arri- val time. This visualizes in an easy way the proportions of any de- fects. Prompted by industry demand for a method to test the structural integrity of concrete in foundation piles Rambøll has invested in the SCXT3000 crosshole sonic logging system developed by Testconsult Equipment.

Hardware The crosshole sonic logging sys- tem consists of a rugged notebook If all pile data is supplied prior to used as logging unit, an electronic the site visit a first impression of winch unit and two ultra-sonic the acquired data can be assessed transducers. This simple system and discussed with the client on makes it very easy to transport site.

Crosshole Sonic Logging (SCXT3000) specifications:  Ultrasonic frequency: 50-60 KHz  Signal measurement for every 1-2 cm depth  Calculation of First Arrival Time (FAT) and Energy changes  Measures concrete piles up to 150 m  Time base 200 to 1000 sec  Path length up to 3 m in hardened concrete  2D & 3D tomography  Strengths: A strong tool for quick assessment of deep concrete foundation piles and concrete walls.  Weaknesses: Requires tubes (Steel preferred) installed in piles and walls

The CSL methods The transit time of sound in con- crete is measured using ultra son- ic transducers. The transducers are lowered into the steel (pre- ferred) tubes installed in the con- crete piles. The transducers are aligned for best signal before start of test. The cables are placed over the electronic winch which is reset to depth zero and the desired profile.

When the measurement is com- menced the cables are manually pulled over the winch. As the winch turns the emitter probe sends a signal for every 1-2 cm Based on the collected data which is stored in the logging unit. Rambøll performs a thorough In the logging unit the traces are interpretation of each pile. This is compiled into a combined profile. gathered in a complete report This sequence is repeated for all where all interpretations are high- possible tube combinations. If a lighted in text in addition to the pile consists of four tubes there interpreted individual profiles. are six combinations. These six profiles are shown as waterfall Besides the crosshole sonic log- plots in the software program ging system Rambøll offers many where it is possible to manually or CONTACT other kinds of geophysical meth- Palle Peter Lindegaard automatically select threshold ods and survey opportunities. Geologist levels for optimization of first arri- Mobile: +45 5161 6789 val time. The profiles can be Please contact us for references [email protected] shown together enabling a differ- on this system and questions entiation between features like about other services. We will be Uffe T. Nielsen tube debonding or true concrete pleased to guide clients to the Project Director Mobile: +45 5161 6782 defects. best possible survey programs [email protected] whether it may be piles, walls, The software contains a 2D & 3D geophysical borehole logging, or Rambøll Danmark tomography module which provide subsurface measurements such as Hannemanns Allé 53 a visual change in first arrival MEP, TEM, 2D & 3D georadar, DK-2300 København S time and energy throughout the reflection and refraction seismics www.ramboll.com/geophysics concrete pile. or cable tracking – both onshore and offshore.