Evaluation of Jet Grout Column Formation based on Undrained Shear Strength-Video

Video Transcription

Video Summary

The speaker presents a method for estimating jet-grout column diameter from undrained soil resistance. They argue that rapid, high-velocity jetting creates undrained conditions even in sands and silts, because pore water cannot drain quickly enough. A hydrodynamic model treats soil as a fluid entrained by the expanding jet; the jet’s cutting distance depends on nozzle pressure, jet characteristics, and soil bearing resistance.<br /><br />Laboratory and field results show reasonable agreement with the proposed equations. For cohesive soils, conventional undrained shear-strength estimates are suitable. For granular soils, however, sampling and laboratory testing are difficult, so the speaker recommends using CPT data. Case studies suggest that granular-soil undrained strength may be approximated as half the CPT sleeve friction, or that sleeve friction can be used directly as the bearing resistance. These approaches predicted column diameters better than standard CPT cone-based estimates. The speaker emphasizes that further field data are needed to validate the method.

Keywords

jet grouting

column diameter estimation

undrained soil resistance

CPT sleeve friction

hydrodynamic soil model

granular soil bearing resistance