This paper aims to determine a non-liquefiable domain corresponding to the threshold of saturation degree where liquefaction does not occur under cyclic loading. To determine this threshold, sample volumetric strain at liquefaction state of unsaturated soil was modeled considering the suction. In low saturation degree zones, capillary suction is taken into account. In a high saturation degree zone, spherical suction caused by surface tension of air bubbles is considered by using its microscopic analysis and its equivalent size. Finally, three series of experimental tests have been made to give the data and verify the presented model.

Alkali-silica reaction (ASR) is a chemical reaction between alkaline ions (Na+, K+), silicon phases and aluminum phases in the aggregate, causing volume expansion and cracking of the concrete, leading to a deterioration in the mechanical properties of the structure. In previous studies, microbially induced carbonate precipitation (MICP) technology had been demonstrated to be effective in inhibiting ASR. In this study, in order to explore better inhibition effect, MICP treatments of alkali active aggregates under different saturation degrees were tested. The results showed that when treated at a low-saturation degree (35 %), the inhibition effect of ASR was better comparing with that obtained at higher saturation degrees in the presence of same CaCO3 content. When the CaCO3 content was about 6 %, mortar bar specimens made of low-saturation treated aggregates possessed a 75 % reduction in the expansion and a 37 % increase in the compressive strength compared to the control group. In addition, through microstructure and component analysis of the aggregate surface, it was found that under the low-saturation treatment, the CaCO3 layer could be formed on the surface of the aggregate more uniformly and efficiently, with a higher binding strength to the aggregate and a greater Vickers hardness. Thus, it could better block the invasion of external alkaline ions to react with the active SiO2 inside the aggregate, leading to a better inhibition of ASR.

Directional-dependent properties of the soil, like shear strength, stiffness and hydraulic conductivity, are known as anisotropy in soils. Shape and size of the soil particles and void distribution as microstructure characteristics and external factors such as stress history, environmental and geological conditions, and present stress condition can be the causes of the anisotropy in soils. In this paper, the behaviour of soil has been studied in stress-strain plain under monotonic anisotropic loading to investigate the effect of induced anisotropy on brittleness index of soil sample. The brittleness index of the soil is defined as the difference between the ultimate and peak shear strength divided by the peak shear strength of the soil. The two major parameters describing induced anisotropy or anisotropic loading are intermediate principal stress (b) and principal stress direction (alpha) which are representative of the difference between intermediate, maximum and minimum principal stresses and the rotation angle of the principal stresses' axis, respectively. This paper only takes the effect of intermediate principal stress with the values of 0.25, 0.5, 0.75. In addition, the soil is in the unsaturated state with the saturation degree of 80% using the constant water (C.W.) method.