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Expansive soils are extremely susceptible to swelling and shrinkage associated with seasonal changes in their moisture content. This can cause serious damage to structures constructed on expansive soils. Stabilization using additives is widely used to mitigate the concerns of expansive soils by controlling the changes in volume, thereby increasing the strength and durability of the soils. Multistabilizers, including a low percentage of conventional additives with nonconventional additives, can reduce the costs of stabilization. The performance of the stabilized soil can be enhanced by admixture optimization to ascertain that the agent's ratios are quite adequate to meet the optimal levels of modification. Unfortunately, despite the development of advanced techniques for investigating the stabilization of expansive soil, limited studies are devoted to the optimization of admixture to soils. Hence, in this research, an approach based on rough set theory, a mathematical data mining approach, is presented for multiagent optimization for efficient treatment of expansive soils. The multiadditives used in this study are almond shell ash (ASA), volcanic rock dust (VRD), and portland cement (PC). The differential free swell test, the California bearing ratio test, and the unconfined compressive strength test were applied for assessing the characteristics of the stabilized soil specimens. The obtained results and the confirmatory tests demonstrated that a combination of 20% ASA and 20% VRD with 8% PC provides the optimum results in the properties of expansive soil. The microstructural analysis denoted an enhanced modification of the soil engineering properties. The outcomes of this research confirm that the rough set optimization procedure is highly suitable for application in multiagent optimization for the efficient treatment of expansive soils. [ABSTRACT FROM AUTHOR]

A method for an a priori estimation of the frost heave ratio for clayey soils, considering the degree of their water saturation upon a closed system of freezing, is proposed. The proposed approach involves the introduction of a new parameter in the mechanics of frozen soils, namely, the frost heave index of clayey soils, which characterizes the degree of frost heaving of soil relative to the maximum height of the frost heave of soil that is fully saturated with water. An introduced parameter is used in the final formula to estimate the frost heave ratio of clayey soils. Laboratory experiments were performed to determine the height of frost heaving of clayey soils with a variation in their moisture and porosity to verify the proposed approach. A comparison of the experimental and calculated results showed a suitable convergence sufficient for the practical use of the formula to determine the frost heave ratio in a closed system of freezing. An example of a calculation to justify antiheaving measures using the proposed estimation of the frost heave ratio is given. [ABSTRACT FROM AUTHOR]

This paper examines the accuracy of a new elastic–thermoviscoplastic (E-TVP) constitutive model developed based on critical state soil mechanics. The model can be used for simulating the temperature-dependent and strain-rate-dependent behavior of clay soils. The study compares the E-TVP behavior of a single soil element with previously published thermo-mechanical experimental results performed on saturated clay specimens at different temperatures. Suggestions regarding unloading and reloading at constant temperatures as well as thermal consolidation under constant loads are presented. A modification for unloading–reloading adds a new criterion to the volumetric thermoviscoplastic strain rate formulation. A physics-based term is added to the current specific volume of the soil to include the viscous effect induced by temperature change. These modifications improve the convergence of laboratory data and simulated model responses. Comparisons of results from an earlier E-TVP model and the newly improved model provide evidence of improved predictive capabilities. [ABSTRACT FROM AUTHOR]

A new analytical method for investigating the stability of unsaturated soil slopes was developed by considering a 3D failure wedge under different steady-state infiltration and evaporation. In this light, the general limit equilibrium approach and concept of effective stress in unsaturated soils were implemented. An extensive parametric study was performed as well, to study the effect of slope geometry, unsaturated soil properties and/or state/material variables, position of groundwater level (GWL), and infiltration and evaporation flow rates on the stability of soil slopes against failure and landslide. In addition, a quantitative comparison was made between the safety factors obtained from the proposed unsaturated 3D analysis and those obtained from two-dimensional (2D) and three-dimensional (3D) classical slope stability analysis. It was revealed that the steady-state infiltration/evaporation has a significant influence on the stability of the silty and clayey soil slopes. In addition, the geometrical aspects of the slope and the hydromechanical parameters of the soil largely affect the safety factor of soil slopes against failure. Results show that the safety factors obtained from unsaturated 3D analyses for the silty and clayey slopes are remarkably different from those obtained from 2D and 3D classical calculations; however, negligible differences were found for the sandy slopes in that respect. In addition, a comparative study was performed on the impact of governing parameters on the safety factors of unsaturated slopes under infiltration and evaporation using an unsaturated 3D column method. It was revealed that infiltration has a pronounced effect on the safety factor compared with that for evaporation and that silty and clayey slopes are more affected by evaporation and infiltration than sandy slopes. In general, this study showed that applying unsaturated soil mechanics concepts to 3D stability analysis not only leads to more precise safety factors against the slope failure and landslide initiation but may also reduce the uncertain conservatism considerations in some practical problems. [ABSTRACT FROM AUTHOR]