Selection of Suitable Ground Improvement Techniques for Southeast Queensland Soft Clay

Soft estuarine clays are found in many expressway and motorway projects in Southeast Queensland. The strengths of these clays are very low and as such embankments failures can be encountered during construction. Several ground improvement techniques are available to increase the soil strength, and these techniques include the use of surcharge with stone column or vertical drains. When the coefficient of consolidation is low, the sensitivity and organic contents are high, preloading techniques with vertical drains may not be effective due to smear effects. Thus, chemical stabilisation may the appropriate alternative ground improvement technique. The cement stabilisation improves the strength of soft clay by effectively aggregating smaller particles with additional chemical bonds. A laboratory study has been conducted to examine the influence of cement additives on Southeast Queensland soft clay. Unconfined compression tests showed that, 5% cement additives cured for 7 days increased the unconfined compressive strength when compared to untreated samples. Further, cement additives was also found to increase the pre-consolidation pressure in the oedometer tests. Thus, the initial studies conducted have demonstrated its potential use in shallow and deep stabilisation for Southeast Queensland soft clay.