Multiphase flow processes in unsaturated cohesive soils are often affected by deformation due to swelling and shrinking as a result of varying water contents. This paper presents a model concept which is denoted 'phenomenological' in terms of the processes responsible for soil deformation, since the effects of deformation on flow and transport are only considered by constitutive relations that allow an adaptation of the hydraulic properties. This new model is validated in a detailed intercomparison study with two state-of-theart models that are capable of explicitly describing the processes relevant for the deformation. A 'numerical experiment' with a state-of-the-art reference model is used to produce 'measurement data' for an inversemodelling-based estimation of the model input parameters for the phenomenological concept.
Die vorliegende Veröffentlichung behandelt die Entwicklung eines elasto-plastischen Stoffmodells für teilgesättigte bindige Böden. Abweichend von den aus der Literatur bekannten Stoffmodellen für teilgesättigte Böden sind Änderungen von Zustandsgrößen unmittelbar in den Modellparametern erfassbar und nicht mit der Saugspannung gekoppelt. Der Einfluss der Zustandsgrößen Anfangsporenzahl, -sättigungsgrad sowie Spannungsniveau auf das mechanische Verhalten eines mittel bis ausgeprägt plastischen Tons wird untersucht. Zur Ermittlung der relevanten Stoffparameter werden triaxiale deviatorische Kompressions-und Extensionsversuche in einem speziellen Triaxialgerät durchgeführt. Das aufgestellte Stoffmodell wird in das FEM-Programmsystem Abaqus implementiert und damit das Verformungsverhalten einer Flachgründung bei Aufsättigung des Bodens untersucht.
Mechanical behaviour of a partially saturated kaolinite-clay:Experimental investigation, constitutive model, and implementation. The present publication deals with the development of an elasto-plastic constitutive model for partially saturated cohesive soils. In contrast to the constitutive models available in the literature for unsaturated soils, changes in the state variables are explicitly included in the model parameters and uncoupled to the suction value. The influence of the state parameters initial void ratio, initial degree of saturation, and stress level on the mechanical behaviour of a common medium to high plasticity clay is investigated. The relevant constitutive parameters are determined from triaxial deviatoric compression and extension tests carried out in a custom-built triaxial apparatus. The constitutive model is implemented in the FEM code Abaqus, and applied to investigate the deformation of a surface foundation during saturation due to irrigation.
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