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

PPT Presentation

Pdf Summary

The presentation develops a framework for predicting jet-grout column formation from the interaction between a high-velocity fluid jet and soil. Jetting is treated as turbulent excavation: soil at the jet front is assumed to fail under undrained conditions, and the jet’s decreasing velocity with distance is compared with the soil’s bearing resistance to estimate penetration.<br /><br />The approach builds on laboratory jetting tests and generalized models for single-, double-, and triple-fluid systems. It is evaluated against shallow and deep field trials, including columns in fill, organic soil, silty sand, and varved silt. Comparisons examine predicted and measured penetration or column diameter under different grouting pressures, flow rates, air pressures, and operating settings.<br /><br />A central challenge is estimating undrained shear strength, especially in cohesionless soils, where sampling and laboratory testing may not reproduce field conditions. The presentation reviews laboratory tests, SHANSEP relationships, and CPT-based estimates, while noting that soil anisotropy and post-liquefaction strength can affect interpretation.<br /><br />The field-trial analysis considers alternative estimates of soil bearing resistance derived from CPT tip resistance or sleeve friction. Its key conclusions are that undrained bearing failure occurs at the jet front in both cohesive and granular soils, and that for vertical jet grouting, undrained shear strength can be estimated as approximately half the CPT sleeve friction. The corresponding soil bearing resistance may be taken as the sleeve friction itself. These estimates can support predictions of jet penetration and grout-column diameter.

Keywords

jet grouting

jet-grout columns

turbulent excavation

undrained shear strength

soil bearing resistance

CPT sleeve friction

bearing failure

penetration prediction

single double triple fluid systems

field trials