In-situ investigation of problematical soils

摘要

Problematical soils occur in many parts of the world, both naturally and as a result of man-made activity, thus making their behaviour a truly global problem. In-situ properties are often variable and difficult to predict, so effective site investigation is essential for the optimum characterisation and prediction of soil behaviour. Commonly, site investigations favour established techniques such as penetration tests, trial pits and boreholes. These provide useful but limited data, being obtained at discrete points on a site. Similarly, and as a consequence of disturbance, laboratory testing of soil samples often does not truly reflect the in-situ properties of the soil. The use of in-situ geophysical investigation is suggested as a possible solution to this problem. This paper highlights the potential of geophysics, with illustrated examples of recent work where geophysical methods have successfully assessed tropical red clay and brickearth soil properties. Information can be gained on both the general physical properties and the properties relating to failure of the soil (e.g. collapse or landslides), such as moisture content and presence of voids. It is also possible to assess the effectiveness of ground improvement engineering work undertaken on such soils. Geophysical investigations, characterising whole volumes of ground can be conducted rapidly and cost effectively, helping to provide the best approach to gain knowledge of in-situ collapsible soil conditions.