Laboratory approach for faster determination of the loading-collapse yield curve of compacted soils

A shift in the preconsolidation pressure or yield limit with suction, referred to as the loading-collapse (LC) yield curve, is an important feature of elastoplastic models of unsaturated soils. The LC curve is typically defined in the matric suction versus mean stress plane to account for the effects of matric suction. Conventional methods to determine the LC yield curve rely on a series of isotropic compression tests on specimens with identical stress history. This paper presents an alternative method to determine the LC yield curve from isotropic compression test results of specimens without identical stress history restrictions. A series of equations is proposed, derived from elastoplastic theory and incorporated into conventional compression test results, for drawing the specific LC yield curve. The advantage of the proposed methodology is that the compression tests results need not be taken from identical stress history specimens, which leads to a shorter time frame in the laboratory. Moreover, no additional parameters are required apart from those required in the conventional method. Test results from the literature are used to verify the proposed methodology, and a good agreement between the measured and calculated LC curves was found. The proposed methodology is a less time-consuming and more economical method to draw LC yield curve than the conventional method