DCP Investigation of Strength Increases in Polyurethane and Acrylate Treated Soils-Paper

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The study evaluated strength changes in silty sand treated with polyurethane or acrylate grout using a full-scale soil mock-up designed to approximate regional ground conditions. Compacted soil was injected at low pressure, in roughly 0.3 m lifts, through a grid of PVC probes. Dynamic cone penetrometer (DCP) tests compared treated areas with untreated soil; correlations were used to estimate SPT blow counts, California Bearing Ratio (CBR), and bearing capacity.<br /><br />Polyurethane-treated soil showed approximately twice the DCP penetration resistance of untreated soil. Derived estimates indicated about a 33% increase in SPTn, a 133% increase in CBR, and an 80% increase in bearing capacity. The authors conclude that the polyurethane and injection methods tested may improve the bearing capacity of sandy soils.<br /><br />Acrylate-treated soil showed no increase in DCP penetration resistance relative to untreated soil. However, both acrylate- and polyurethane-treated sections remained unsupported at heights greater than 1.2 m when the container gate was opened, suggesting potential for excavation support. The study notes that further direct shear testing is needed to assess acrylate’s shear-strength contribution.<br /><br />Core samples were collected for laboratory testing, including triaxial and unconfined-strength tests on polyurethane-treated soil and direct simple shear tests on acrylate-treated soil. These tests were delayed by COVID-19 restrictions, so the reported findings rely on mock-up observations and DCP-based correlations; laboratory results were not yet available.

Keywords

polyurethane grout

acrylate grout

silty sand

soil stabilization

dynamic cone penetrometer

bearing capacity

California Bearing Ratio

SPT blow count

excavation support

soil injection