Experimental study on swelling behaviour and microstructure changes of natural stiff Teguline clays upon wetting

Abstract

This paper addresses the microstructure change induced by swelling for natural stiff Teguline clays. The predominant clay mineral measured by X-ray diffractometry was identified to be illite and no swelling clay minerals were found. Significant swelling occurs upon wetting, illustrating the process of suction release from a nearly fully saturated condition. Mercury intrusion porosimetry (MIP) and scanning electron microscopy were used to identify the change in microstructure with swelling during wetting. It is found that the soil swelling mainly leads to an increase of macropores (0.15–350 μm), and a slight decrease of micropores (0.006–0.15 μm) and inaccessible pores (<0.006 μm and >350 μm). Furthermore, swelling was found to occur in the direction perpendicular to the bedding plane, indicating an anisotropic swelling behaviour. The creation and development of cracks during wetting were also investigated. It appears that most cracks caused by swelling have the size of macropores (0.15–350 μm) identified by the MIP test. These findings call enough attention to the significant change in microstructure by wetting-induced swelling that can strongly influence the thermohydromechanical properties of stiff clays.

Changes of small strain shear modulus and microstructure for a lime-treated silt subjected to wetting-drying cycles

“…Wang et al (2014) on compacted bentonite, byZeng et al (2020) on compacted bentonite/claystone mixture, and byZeng et al (2017) on stiff Teguline clay. This phenomenon was attributed to the division of aggregates with wetting.…”

The Role of Superabsorbent Polymer on Strength and Microstructure Development in Cemented Dredged Clay with High Water Content

“…Then, the small specimens were submerged into liquid nitrogen and vacuum cooled to approximately −210 °C. Finally, the frozen samples were put into the vacuumed chamber of a freeze dryer for sublimation for approximately 24 h. It has been proven that this procedure minimizes the disturbance of the soil microstructure [37,38,39].…”

Effects of technological voids and hydration time on the hydro-mechanical behaviour of compacted bentonite/claystone mixture

“…With the transformations of inter-aggregate and intra-aggregate pores into the medium-pore population, a significant increase in the medium-pore void ratio was observed. Additionally, fissure-like 2-dmensional (2D) pores with a mean pore size of 20 μm appeared, explaining the increased void ratio of large pores (Wang et al, 2014;Zeng et al, 2016). At the homogenization stage, the large pores and medium pores of the compression zone were compressed gradually by the swelling pressure, leading to decreases in large-pore and medium-pore void ratios.…”