Permeation Grouting using Polyurethane and Acrylate Resins in a Silty SAND (SM); Injection Methods, In-situ Verification Testing Methods and Laboratory Results.-PPT Presentation

PPT Presentation

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The demonstration evaluated polyurethane and acrylate grouts for permeation grouting in compacted silty sand (SM), using a large soil container, staged injections, and laboratory and in-situ testing. The polyurethane grout (CUT PURe) was a single-component product capable of expanding up to 30 times; the acrylate grout (AC-400) was a low-viscosity, non-expanding gel. Injection pressures generally targeted 5–15 psi.<br /><br />Polyurethane treated up to about five times its injected liquid volume under shallow, unsaturated conditions. Although some soil fracturing formed thin grout veins, permeation spread from these veins and produced a relatively uniform composite with a diamond-grid injection pattern. Higher polyurethane flow rates increased back pressure, with fracturing observed above roughly 1.5 bar. Acrylate flow rates up to about 9 L/min did not similarly increase back pressure, and the grout permeated without fracture planes.<br /><br />Tests indicated that polyurethane treatment substantially improved soil resistance and strength. Dynamic Cone Penetrometer results were, on average, double those of untreated soil; estimated correlations showed increases of 33% in SPT N-values, 133% in CBR, and 80% in bearing capacity. Laboratory testing reported average unconfined compressive strength of 1,225 kPa and confined-undrained triaxial strength of 1,175 kPa, with 870 kPa of cohesion attributed to polyurethane cementation.<br /><br />Acrylate-treated soil had DCP resistance similar to untreated soil but could support a 4-foot excavation and remained readily excavatable. The study also found that acrylate could permeate weaknesses in polyurethane grout, potentially improving water cutoff. The authors recommend further testing, particularly for acrylate applications in shallow excavations.

Keywords

polyurethane grout

acrylate grout

permeation grouting

silty sand

soil stabilization

injection pressure

soil fracturing

dynamic cone penetrometer

bearing capacity

water cutoff