Blackfriars Shaft, London - Advances in Deep Jet Grouting-Video

Video Transcription

Video Summary

The presentation described jet grouting for the 52-metre-deep Blackfriars drop shaft, part of London’s Thames Tideway sewer project. Variable soils, obstructions and increasing borehole deviation made a continuous grout wall uncertain. Rather than abandon the approach, the team used Monte Carlo modelling to estimate the likelihood, size and location of gaps, informed by trial columns and measured deviation data. They selected equipment and procedures to minimize deviation, surveyed each borehole, and adjusted grouting parameters as work progressed. As-built data identified gaps, which were assessed for acceptability or filled with additional columns; dewatering also helped manage risk. The team successfully completed the perimeter, using nearly all of the planned contingency infill columns, and the shaft was excavated successfully. Early collaboration and clear, rapid data-sharing helped engineers and commercial teams understand and manage contractual risks. The project demonstrated that quantified, manageable risks can support deeper, more cost-effective jet-grouting designs.

Keywords

jet grouting

Blackfriars drop shaft

Thames Tideway sewer project

Monte Carlo modelling

borehole deviation

dewatering