Chemical stabilizers (e.g., cement, lime, gypsum, and other alkaline admixtures) have been widely used to enhance the strength and compressibility properties of subgrade soils. However, traditional chemical stabilizers are not always acceptable in Australia because they often pose a threat to the surrounding environment. Moreover, traditionally treated soils usually exhibit excessive brittle behaviour, which is often undesirable for transport infrastructure such as rail embankments and airport runways. To establish an alternative stabilizer that could overcome the above problems, this note presents a series of experimental results on the use of lignosulfonate (by-product of timber and paper industry), an environmentally friendly soil stabilizer effective for treating fine sandy silt that formed the bulk of an embankment fill at Penrith, Australia. The effects of lignosulfonate treatment on the shear behaviour of treated soil, including the stress-strain relationships, and the corresponding development of excess pore pressure and volumetric responses under monotonic triaxial testing are discussed.