Theoretical and Practical Aspects of Jet Grout Plug and Cut-Off Design-PPT Presentation

PPT Presentation

Pdf Summary

The presentation examines the design and construction of jet-grouted cut-offs and plugs, drawing on the author’s experience with projects worldwide. Statistical analysis is used to assess how column diameter variation, drilling deviation and column spacing affect the continuity and permeability of the grouted barrier.<br /><br />For linear cut-offs, two rows provide greater security than one: water must pass through multiple gaps to breach the barrier. Even a small proportion of ungrouted area can substantially increase overall permeability. Column diameter variability of up to 20% is generally less consequential than a consistent reduction in diameter.<br /><br />Base plugs are more challenging because their edges must also be sealed. Their design requires intensive computational checks, and successful construction depends on very high workmanship standards to avoid significant leakage.<br /><br />Practical measures to improve sealing include sequencing column construction, jetting closure columns at higher energy, ensuring overlap at the top and bottom, and using slower withdrawal rates—particularly for secondary columns in the plug’s centre—to accommodate drilling deviation.<br /><br />The key message is that geometry and construction methods must be considered together, and clients should be warned that leakage may still occur and should be prepared for it.

Keywords

jet grouting

cut-off walls

base plugs

permeability

column diameter

drilling deviation

column spacing

grouted barrier

construction methods

leakage control