A new approach for characterising expansive clay sites

Highly expansive soils are common throughout the world. In Australia more than 20% of the near-surface soils are considered moderately or highly expansive, many are in large cities. The Australian standard (AS2870) recommends 3 methods to ‘characterise’ a building site and in each case some form of regular laboratory testing is required to test the soil indices. To do so this the Standard recommends any of the following: Shrink/Swell, Loaded Core Shrinkage, or Unloaded Core Shrinkage test. The most common of these is the shrink/swell test (S/S); however in this test soil suctions are not measured and instead assume certain parameters. This paper presents a new Conditioned Core Shrinkage test (CCS) with suction measurements. This test is performed in the suction range of 3-7pF and provides the soil shrinkage index values (Iss) along this range to calculate the ‘characteristic surface movement’ (ys). The test can be carried out in 4 -7 days depending on the type of soil and recent climate.