Field monitoring of seasonal ground movements in expansive soils in Melbourne

Shrink-swell behavior of expansive soils highly influences the performance of lightly loaded structures with shallow footings. Expansive soils often undergo heave and settlement due to soil moisture variation, which may cause differential movement in the structure. This phenomenon becomes critical when the changes in soil moisture are widespread due to climatic conditions. Indeed, there have been reports in the media regarding footing movements and cracks in new houses in Victoria particularly following the breaking of the last prolonged drought. As part of an ongoing research study on damage to residential structures caused by ground movements, a field site has been established on a vacant land in a western suburb of Melbourne. Soil moisture variation and corresponding ground movements are monitored using Neutron moisture probe and magnetic extensometers respectively. Soil suction variation is also measured from undisturbed samples in the laboratory. This paper describes the site selection, instrumentation and soil classification. The variations of soil properties with depth are discussed. Soil moisture variation is compared with climate data of the site and presented along with the corresponding soil layer movements.