Hydromechanical behaviour of expansive soils with different suctions and suction histories

Abstract

This paper presents a number of experimental results of suction-controlled triaxial tests on a compacted weakly expansive soil with different suctions and suction histories. In terms of suction control methods, the high suction level (from 3.29 MPa to 38 MPa) was realized by the vapor equilibrium technique and the low suction level (from 0 kPa to 800 kPa) was controlled by the axis translation technique. The results of triaxial tests indicate that the specimen with higher suction shows higher strength and smaller contractive and higher dilative volumetric strains and the average skeleton stress ratio (q/p') at failure deceases with increasing the suction in the high suction range (3.29 MPa ~38 MPa). Given that the suction during shearing is constant (e.g. 200 kPa), the specimen dried to higher suction in history shows higher strength and smaller contractive volumetric strain. Experimental results also show that high pre-applied suction (i.e., the maximum suction in the history) can lead to peak strength, post-peak softening and shear dilation. Three different methods (pressure plate, filter paper and vapor equilibrium methods) were employed to study the soil-water retention behaviour of the unsaturated expansive soil. The test results indicate that combining above three different methods is able to determine the soil-water characteristic curve in the entire suction range (0~367 MPa). Test results of the expansive soil also show that the void ratio keeps decreasing along with the increase of the suction in the entire suction range.

A microstructure-based elastoplastic model to describe the behaviour of a compacted clayey silt in isotropic and triaxial compression

“…However, to the authors' knowledge, limited attention has been paid to the influence of cyclic wetting and drying on the triaxial compression behaviour of unsaturated compacted soils, although it seems reasonable to infer that the fabric changes responsible for the changes in the hydraulic response will impact also on the mechanical behaviour. Experimental studies by Kemal et al (2005) (on sand samples), by Rojas et al (2010) (on clayey silt samples cored from a river embankment a few years after construction), and by Zhang et al (2016) (on a slightly expansive silty soil) remark that drying-wetting cycles tend to increase the peak soil strength and the post-peak soil brittleness.…”

Study on Soil-Water Characteristics of Expansive Soil under the Dry-Wet Cycle and Freeze-Thaw Cycle considering Volumetric Strain

“…Ma et al [21] used nuclear magnetic resonance (NMR) technology to study the change law of water content in the drywet cycle and explained the change mechanism of the pore in SWCC. Whereafter, some scholars studied SWCC under complex conditions such as dry-wet cycle and freeze-thaw cycle [22][23][24][25][26][27][28][29]. It can be seen that these studies are aimed at the expansive soil in a particular area, and the SWCCs of expansive soils in different areas have different laws under the external conditions such as dry-wet cycle and freezethaw cycle.…”

A simple and practical method for predicting soil water characteristic curve based on grading parameters

“…Five soils including expansive soil (Zhang et al 2016) [12], silty soil (Zhang et al 2018) [13] and sandy soils (Wang et al 2017) [11] were chosen for the study considering the breadth of soil types. The particle size distribution curves of five soils are shown in Fig.…”