Experimental Validation of Effective Stress Concept in Partially Saturated Soils; Suction, Shear Strength and Tensile Strength

• Applicants: Professor Dr.-Ing. Gunnar Heibrock; Dr.-Ing. Diethard König, since 3/2018
• Subject Area: Geotechnics, Hydraulic Engineering
• Term: from 2016 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 283176637

To date there is an ongoing discussion how to describe the effect of soil water interaction (in terms of suction) when dealing with the mechanical behavior of partially saturated soils. One approach is to describe the macroscopic effect of suction in terms of effective stress. This approach has the fundamental advantage that classical soil mechanic principles can be applied to partially saturated soils. A growing number of lab tests indicates that the effective stress concept is sufficient to describe macroscopic effects from soil water interaction when dealing with limit state e.g. shear strength related problems. However a systematic experimental validation taking into account the full mechanical stress and suction range as well as different failure modes is still missing. Thus the purpose of the project is to experimentally validate the effective stress concept with respect to shear strength of partially saturated soils. Different kinds of shear tests (triaxial, direct shear, water content and suction controlled tests) and tensile tests (direct and hollow-cylinder) using fine grained soil samples will be performed. Unlike existing works the proposed experimental study takes into account tensile and low to high mechanical stresses as well as dry to saturated conditions and therefore the full suction range. In addition comparison of the results from the different kinds of tests allow to investigate possible differences resulting from different failure modes. Test results will be used to derive closed form effective stress equations describing the shear strength of partially saturated soils as a function of suction, saturation and soil structure parameters.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Tom Schanz, Ph.D., until 2/2018 (†)