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A Novel Yield Surface for Unsaturated Soils

Somjai Yubonchit, Avirut Chinkulkijniwat


This paper presents yield surface of unsaturated soils on a net stress - suction plane. A proposed model was developed based on a combination of soil structure and elasto-plastic theory. The soil structure is employed to establish an initial yield surface. The soil structure is normally represented via the soil water characteristics curve (SWCC). Hence, the initial yield surface could be derived by mathematic manipulating with the SWCC. A subsequence yield surface was derived by equality of plastic volumetric strain between two stress paths traveling along the same yield surfaces. For a given yield surface, yield stresses provided from the derived yield surface remain constant if a soil suction does not reach an air entry suction. Once, the soil suction develops beyond the air entry suction, the magnitude of yield stress increases with suction.


constitutive model; yield surface; unsaturated soils

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