Monitoring data helps to establish hypotheses of the mechanisms of degradation. However, the detail of degradation mechanisms of soils in response to cycles of pore water pressures and the effects of fabric requires carefully controlled laboratory testing. Only when the results at this scale are coupled with the field and numerical investigations can a fully developed model of the near surface processes and their effect on soil strain be developed.
Evidence from earlier centrifuge model tests and numerical models of clay slopes informs the magnitude of seasonal effective stress cycles that are likely to promote strain softening. This is used to inform the design of the laboratory investigation and ensure relevance to the development of both shear surfaces and down slope ratcheting.
Laboratory-scale data also provide soil water retention curves and stress-strain characteristics as essential inputs for numerical models, and to establish property relationships (e.g. resistivity – water content) for the calibration of field-scale geophysical images.