Numerical study of bending test on compacted clay by Discrete Element Method: tensile strength determination

The study of the tensile behaviour of clay is one of the topics which requires a specific lighting especially when one pays a close attention to the pathology of work built with or on clays subjected to significant tensile forces. Therefore, failure or damage of clay, under specific conditions, can be related to tensile stress limit and not to shear stress limit. It is the case of compacted clay liners in landfill cap cover subjected to differential settlements within the waste. In order to study the tensile compacted clay behaviour, a series of laboratory bending tests were carried out. The analysis of the results and the determination of relevant parameters are difficult. Extrapolation to mechanical clay behaviour could not be directly obtained. On the basis of the test results, different numerical simulations using Discrete Element Method were performed and compared with an analytical model, which seems to be the most suitable to interpret bending tests results for the clay soils. As main result, the Discrete Element Method confirms that the compression stress remains linear function of the strain during the bending test until the failure. However, the tensile stresses increase as a non-linear function. For the tensile strength determination, the analytical differential model remains efficient only when the tensile strain field is well measured.