Behaviour of clayey soils overlying cavities

clayey_soilsThe appearance of many sinkholes has become a hazard for their instantaneous development and for the damages they can produce to infrastructure. The term sinkhole indicates a location in which the ground is sinking in cavities and this process is mainly caused by water penetration into the ground. Water causes dissolution of the soluble rocks of the bedrock resulting in the creation of a void and the consequent collapse of the overlying soil. Despite the increasing interest on this phenomenon, rarely the geotechnical aspects of the event are studied especially in relation to the characteristics of the soil that stands on a cavity.

The research aims to find a set of parameters which can be used to predict the likelihood of sinkhole appearance. The project is divided in two parts: the first is based on the collection of data of previous events, the second is related to laboratory tests performed on small clay models.

The creation of the historical database will allow the comparison of the results of the tests with the past data, to study similar characteristics or conditions in which the failure takes place. The additional laboratory tests will further understanding of the effect of soil properties in which failure mechanisms take place. Two types of experiments will be performed on clay beams: centrifuge tests to investigate the progressive failure caused by the slow ravelling of the soil and bending tests to study the instantaneous failure caused by cracks propagation. Geotechnical properties will be varied throughout the tests, such as the plasticity, water and clay contents for covering different situations of sinkholes formation. Attention will be also paid to the triggering factors that cause the initiation of the process, like rainfall and soil softening.