Seismic CPT & CPTu (SCPT & SCPTu)

MEASUREMENT OF COMPRESSION AND SHEAR WAVE VELOCITIES

Legion Drilling uses Marchetti’s SPDMT system for seismic CPT. This module adds measurement of both compression and shear wave velocities (Vp, Vs) to the parameters obtained with CPTu (cone tip resistance, sleeve friction and pore pressure).

Wave velocities are typically measured at 0.5-m or 1-m intervals. Shear wave velocity can be calculated on real time thanks to the true-time configuration of our dual array SCPTu system.

In the case of non-penetrable formations, shear wave velocity values can be obtained using backfilled boreholes.

Samples can be rapidly collected using direct push technology in adjacent locations upon request.

MAJOR BENEFITS OF LEGION DRILLING’S SEISMIC CPT SYSTEM

  • Collection of CPTu parameters along with compression and shear wave velocities.

  • True-time interval method enabling real-time calculation of shear wave velocity.

  • Assessment of soil behaviour in terms of age and cementation effects. Most traditional geotechnical correlations have been developed for relatively young, uncemented soils only.

  • Enhanced estimation of stiffness parameters like Young’s, shear, and small strain shear moduli (E, G and G0).

  • Possible estimation of other parameters such as undrained shear strength, soil unit weight, void ratio and peak friction angle.

  • Identification of water-saturated intervals thanks to the measurement of compression wave velocities (Vp).

  • Operable on light track-mounted machines for difficult access locations.

SOME SEISMIC CPT APPLICATIONS

  • Foundation design (deep and shallow).

  • Liquefaction evaluations and earthquake engineering.

  • Determination of water-saturated intervals (including perched water).

  • Monitoring of water conditions in Tailings Storage Facilities.

  • Estimation of stress-strain relations for numerical modelling.

BENEFITS OF GEOPROBE MOUNTED SCPTu

  • Access almost any location with small track mounted machines.

  • Use augers and rotary air to predrill through ballast and fill.

  • Case SCPTu locations with the same machine.

  • Complete installation of other geotechnical instruments with the same rig saving on costs.

  • Use any of Legion Drillings Geoprobe machines located in Brisbane, Sydney and Townsville.

FURTHER INFORMATION

Our field technicians will be happy to provide further information and discuss in detail any specific project requirements.

In the meantime, we recommend you consult the following documents: