Effect of clay minerals on the suction stress of unsaturated soils: Fid-Bau Portal

Effect of clay minerals on the suction stress of unsaturated soils

Song, Young-Suk / Hong, Seongwon

Abstract The primary objective of this study is to investigate the characteristics of suction stress in two types of unsaturated weathered soils with different clay minerals. To obtain the mineralogical properties of the two samples, X-ray diffraction and scanning electron microscope analyses were conducted, and a large amount of kaolinite and montmorillonite was subsequently contained in the granite soil and mudstone soil, respectively. The granite soil was first remolded to obtain the same relative density and particle size distribution as the mudstone soil, and an automated soil-water characteristic curve (SWCC) apparatus was used to measure the water content and matric suction. The weathered granite soil had a higher air-entry value, and the volumetric water content was significantly changed by small changes in matric suction. The weathered mudstone soil showed a large hysteresis in the SWCCs between drying and wetting processes because of the ink-bottle effect, contact angle effect, and trapped air. The suction stress characteristic curve (SSCC) demonstrates that weathered mudstone soil had a larger magnitude of suction stress. The SSCCs of the weathered granite and mudstone soils display similar tendencies to the SSCCs of silt and clay, respectively. Therefore, the unsaturated characteristics considerably depend on the clay mineral composition and particle size distribution.

Highlights • Weathered mudstone and granite soils were used as the test materials. • The mineralogical properties of two samples were obtained using XRD and SEM. • Granite soil was remolded to have the same relative density and particle size distribution as mudstone soil. • SWCC and SSCC were drawn based on experimental data. • The characteristics of the suction stress of unsaturated soils depend on the clay minerals.