Expansive soils, or reactive soils, experience moisture changes under the prevailing climate conditions, leading to shrink during dry periods and swell in wet months. Houses founded on such problematic soils are subjected to considerable ground surface movements, which can greatly affect the function and performance of buildings. Such movements will increase with the presence of a tree or tree groups nearby since tree roots can extract considerable amounts of water from soils, resulting in localized shrinkage settlement. In this study, a field site was selected with a large native spotted gum tree in a well-established eastern suburb of Melbourne, Victoria. The site and tree are fully instrumented. Surface and sub-surface movement pads, in situ soil psychrometers and neutron moisture meter access holes were installed to evaluate soil moisture/suction changes and subsequent ground movements. A sap flow meter that incorporated the heat ratio method was installed on the north side of the main trunk of the tree at breast height to enable sap velocity and sap flow volume to be closely monitored. Soil types, degree of reactivity and capability of soil water retention have been evaluated through a number of laboratory soil tests including shrink-swells, Atterberg limits, and soil water characteristic curve determination. This paper presents the preliminary monitoring results for a period of 6 months. Valuable field data such as this can help geotechnical engineers and practitioners to get a better understanding of the physical processes that drive tree root-expansive soil interaction and in time improve the current footing design guidelines.

膨胀土或反应性土壤在主要气候条件下经历水分变化，导致在干旱时期收缩并在潮湿月份膨胀。建在这些有问题的土壤上的房屋会受到相当大的地表移动，这会极大地影响建筑物的功能和性能。这种移动会随着附近一棵树或树群的存在而增加，因为树根可以从土壤中提取大量的水，导致局部收缩沉降。在这项研究中，在维多利亚州墨尔本东部郊区的一个成熟的东郊选择了一个带有大型本地斑点胶树的现场。该站点和树已完全检测。表面和亚表面运动垫，安装了原位土壤干湿计和中子湿度计检修孔，以评估土壤湿度/吸力变化和随后的地面运动。结合热比法的树液流量计安装在树干北侧胸高处，以密切监测树液速度和树液流量。土壤类型、反应性程度和土壤保水能力已通过许多实验室土壤测试进行评估，包括收缩膨胀、阿特伯格极限和土壤水分特征曲线测定。本文介绍了为期 6 个月的初步监测结果。