Shear Response of Lime/GGBS-Stabilised High-Sulphate-Bearing Clay under Consolidated-Undrained Conditions

This study investigated the consolidated undrained shear behaviour of a stabilised high-sulphate soil system. Lime was used to stabilise the soil with the inclusion of ground granulated blast furnace slag (GGBS) as an ettringite suppressor. Both volumetric changes and shear strength responses of the stabilised soil containing various proportions (10%, 20%, and 30%) of sulphates were examined with corresponding pore pressure developments and stress path changes using a modern computer-controlled stress-path triaxial system. Results indicated greater volume change for the non-stabilised soils containing lower amounts of sulphates. This shows that calcium sulphate, which is a soluble salt with relatively less alkalinity, is capable of binding particles of soils together. The amount of volume change increased with the quantity of sulphates in the stabilised soil even though the quantity of GGBS utilised as an ettringite suppressor was twice more than that of the lime. This was attributed to the unreacted gypsum (calcium sulphate) used, which resulted in a decrease in the overall specific weight, thus affecting the texture of the stabilised mix and causing an increment in pore sizes. Generally, the stabilised sulphate soils showed some initial ductile responses with the yielding followed by an almost perfectly plastic behaviour up to about 6-8% of the strain before finally undergoing small amounts of strain-softening. Lastly, higher levels of plastic failure were achieved and at higher constant effective stress for the stabilised soils containing lower percentages of sulphates.

Automated summary

The study found that non-stabilised soils with lower amounts of sulphates exhibited greater volume changes, indicating that adding sulphates can promote the bonding of soil particles. Increasing the amount of sulphates in stabilised soil led to a greater volume change, which was attributed to the use of unreacted gypsum in the stabilisation process.