Curtailing the Adverse Effects of Expansive Soils on Roads

Hadi Khabbaz

The seasonal moisture variations in expansive soil deposits lead to their subsequent movements resulting in structural damages. A large part of coastal regions in Australia are recognised as expansive soils and effective treatment of expansive soils is a national and worldwide challenge. The hazards, posed by expansive soils to civil infrastructure (e.g. roads, railways, pavements, buildings, pipelines and canals) are high and costly in coastal regions. Excessive swelling, settlement, low strength, insufficient shear strength, high compressibility and internal erosion are typical characteristics of reactive soils resulting in damage to many civil engineering structures due to volume change.

Advances in characterization and treatment of expansive soils using agricultural and industrial wastes are presented, in particular, the prospect of employing bottom and fly ashes and sugarcane bagasse fibre and ash to solve the reactive soil problems are discussed. Bagasse is a fibrous by-product of sugarcane refining industry (an agricultural waste). Bottom and fly ashes are produced as by-products of coal-fired electricity generation (industry wastes). Sugarcane ash is easily available at a lower cost in QLD, creating threat to the environment and needs attention on its safe disposal. Bottom and fly ashes are provided by Eraring Power Station in NSW. Large amount of bottom ash goes to a tailings dam at the station, reaching fast to its maximum capacity.

The experimental results of this investigation indicate that employing these by products can reduce the required amount of lime, cement or natural sand for improvement of expansive soil properties to support infrastructure foundations.

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