Swell-shrink Cycles of Lime Stabilized Expansive Subgrade

Subgrades of expansive nature are one of the main causes of damage to road network in Australia. Consequently, lime stabilization has been widely used to reduce the swell- shrink potential of these types of soils and thus reduce the associated damage. After stabilization and compaction, the subgrade will naturally be exposed to cycles of full swell and or partial shrinkage due to climatic cycles. This paper investigates this behaviour for lime stabilized compacted expansive soil from weathered Quaternary Volcanic geological deposits located in Western Victoria; Australia. These soils were stabilized with varying percentages of hydrated lime (2, 3, 4, 6 and 8 percent) and the swell-shrink paths of both untreated and treated soils were studied. Test specimens were compacted at optimum moisture content and maximum dry density. The samples were subjected to full swell-shrink cycles under a surcharge of 25 kPa to reach structural stabilization and to simulate the impact of climatic wetting and drying cycles. Vertical deformation and swell-shrink cycle relationships for untreated and treated samples were obtained and analyzed. The results of lime stabilization indicate that equilibrium is reached after three cycles for both untreated and treated samples. In addition, results suggest that maximum deformation occurs in the second swelling cycle. Vertical deformation of untreated sample was reduced to a third after adding 2 percent lime and reduced to a sixth after adding 3 percent lime. The gradient of swelling and shrinkage path reduced to about a sixth and third when it is treated with 2 and 3 percent, respectively. The treated samples reached maximum swelling at a higher degree of saturation than the untreated sample.