Oedometric compression and thermal volume behavior of compacted Gaomiaozi bentonite saturated with salt solution

Abstract

Abstract Saline solution has considerable influence on the thermo-hydro-mechanical behavior of compacted bentonite. In this study, the effects of NaCl solution on the swelling deformation, oedometric compression, and thermal volume behavior of compacted Gaomiaozi bentonite were investigated. Results show that compressibility of the specimens decreases with increasing NaCl concentration of the presaturation solution. At an overconsolidation ratio OCR = 1 with a vertical pressure σ v = 0 . 1 \xa0MPa and at OCR = 3 with σ v = 0 . 1 \xa0MPa, the specimens exhibited contraction during heating below the transition temperature, followed by dilation. A larger vertical pressure led to a higher transition temperature (at which the thermal strain turns from contraction to dilation). However, the specimens exhibited only thermal dilation at OCR = 10 with σ v = 0 . 1 \xa0MPa and at OCR = 2 with σ v = 0 . 5 MPa . Additionally, for a given vertical pressure and presaturation solution, the specimens with a higher OCR exhibited a larger irreversible dilation after a thermal cycle. Moreover, the influence of the presaturation solution on the thermal volume change is non-monotonic. A dilute solution (NaCl solution of 0.1 mol/L) and high salinity solution (NaCl solution of 1.0 mol/L) markedly promote the thermal expansion. These experimental trends can be attributed to the fact that attenuation of the diffused double layer repulsion and electrostatic interaction as well as the reduction of the free water at high saline conditions harden the soil.