Deep Foundation Difficulties Solved by Custom Grouting-Paper

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The paper describes customized grouting as a flexible way to manage difficult ground conditions that exceed the limits of conventional deep-foundation methods. Rather than relying on a fixed technique, crews combine or adapt methods such as permeation and compaction grouting as conditions change.<br /><br />The approach uses two grout components, typically cement–bentonite slurry and sodium silicate solution, mixed at the drill rig before injection. Adjusting their proportions in real time changes grout mobility and gel time, allowing the same system to fill voids, permeate ground, or compact it. Drilling and grouting observations—including pressure, flow, and grout take—inform ongoing changes to the mix and hole sequence.<br /><br />Two projects illustrate the method. At Snowy 2.0 in New South Wales, an 11-metre open-faced tunnel boring machine became stranded in saturated, heavily weathered ground beneath a sinkhole. Grouting from angled, cased boreholes formed a stabilizing canopy and improved ground ahead of the machine, enabling it to advance and switch to closed-face slurry operation. The team adapted the work based on grout performance; thermal profiling also helped verify treated zones.<br /><br />At Lihir Gold Mine in Papua New Guinea, pretreatment grouting stabilized porous, sea-dumped mine waste before construction of a diaphragm cutoff wall. The improvement reduced the risks of slurry loss, trench instability, and boulders collapsing onto the trench cutter.<br /><br />The authors emphasize that successful grouting depends on an observational, responsive approach. In the TBM recovery, treatment progressed from more stable areas toward the most voided ground, rather than targeting the largest voids first. Comparing pressure and flow responses across successive holes provided practical, real-time evidence of improvement. Together, the cases show how hybrid, adjustable grouting can address highly variable ground conditions and reduce construction risk.

Keywords

customized grouting

deep foundation

permeation grouting

compaction grouting

cement-bentonite slurry

sodium silicate

TBM recovery

ground stabilization

diaphragm cutoff wall

observational method