Numerical and experimental studies of influence of trees on ground movements in expansive soils

In Australia, distortions of buildings caused by tree roots are widely reported, particularly in areas of expansive soil. Often such damages are attributed to tree root absorption which changes the soil water content and causes settlement of soil foundations. This research focuses on the interaction between tree root and expansive soils. A numerical model has been developed for analysing root-water-soil interaction. The model is incorporated in an ABAQUS pore fluid diffusion and stress analysis. As well as numerical modelling work, the research encompasses field investigation and laboratory testing. A full-scale test site has been established in an urban environment, in Melbourne, Victoria. The site has been extensively instrumented to allow relative humidity, solar radiation, wind direction and speed, rainfall, sap flow of trees, soil moisture conditions and ground movements to be closely monitored. A series of laboratory tests have also been performed on soil samples collected from the test site, which include soil suction measurement, soil consolidation tests, soil water characteristic curve tests and soil swelling and shrinkage tests. Two case studies were conducted in this research project as well. The research has shown that the proposed numerical model is capable of modelling the climate-tree root-water-expansive soil interaction to a degree of sophistication that has not previously been so readily achievable.