Construction of Vertical Moisture Barriers To Reduce Expansive Soil Subgrade Movement

Throughout the world, expansive soils are known to cause damage to light structures, such as residential dwellings, road pavements, and airfields. In Australia, moderate to highly expansive soils cover more than half the state of Victoria and produce significant maintenance problems to the state’s road network. Vertical moisture barriers have been used successfully in many cases across the United States to control movements generated from expansive soil subgrades. Field trials using moisture barriers have also been conducted successfully in Victoria, Australia. However, due to their expense, the treatment of using vertical moisture barriers has usually only been reserved for major highways. A review of current vertical moisture barrier construction methods in the United States is made, and a new construction method developed in Victoria that provides an effective and economical barrier is reported. This method will enable the application of vertical moisture barriers to be more attractive for sealed low-volume roads. A successful field trial of this construction method has been carried out at Dooen, in northwest Victoria, and has since been applied to several other projects in Victoria and South Australia.