A Method for Determining Yield Stress of Unsaturated Soils from Lateral Pressure

ABSTRACT Predicting the stress–strain behavior of unsaturated soils is essential for determining yield stress. This paper explores a new method for determining the yield stress of unsaturated soils from the lateral pressure curve. A series of earth pressure at rest (K0) ondometer tests were conducted on unsaturated Yangqin silt clay. Lateral stress was obtained under different saturations and compactness. The relationship curves between lateral and vertical net stress were drawn for each condition. An obvious turning point was observed in the curve, which can be used to determine the yield stress. The oedometer tests were conducted, and the Casagrande and the bilogarithmic methods were used for comparison purposes. The difference between the proposed and traditional methods was less than 17 %. The initial saturation and compactness influence on the yield stress was discussed. The yield stress increased with the decrease in saturation and increases in compactness, which is consistent with that of the classic method. The test results and comparison prove the rationality of the proposed method. No coordinate transformation is required in the proposed method, which is more convenient for data processing. It can be used to determine the yield stress of unsaturated soils from another perspective.