Improvement of Problematic Soils by Lime Slurry Pressure Injection: Case Study

Lime slurry pressure injection (LSPI) is a stabilization operation used in problematic soils by transportation industries with the aim of improving the geotechnical properties and bringing excessive maintenance costs to an acceptable standard. This paper presents detailed field and laboratory studies of a lime/fly ash stabilized site at Breeza, NSW, Australia. The mixing of slurry into the soil with depths was investigated by excavating a trench while the improvement of geotechnical properties was determined in detailed field and laboratory tests. Visual observations of the surfaces of an excavated trench showed slurry to be distributed within the shrinkage cracks in the desiccated upper soil horizon whereas slurry was conveyed through planes of hydraulic fracture in the soils at greater depths. Laboratory swell tests on the stabilized soils demonstrated a statistically significant reduction of the intrinsic swell properties in the upper horizon of highly plastic clayey soils by LSPI. A gain in soil strength was observed in cone penetrometer test soundings conducted in stabilized soils. Scanning electron microscope and x-ray diffraction studies proved the underlying physicochemical and cementitious reaction processes in stabilized soils. Aggregation of the soils was observed with the outward diffusion of calcium cations within proximity of slurry seams and resulted in a subdued shrink/swell propensity.