The basic correlation that determines the mechanical and hydraulic characteristics of unsaturated soils is the Soil Water Characteristic Curve (SWCC). Critical synthesis The present review brings forth the latest developments in SWCC modeling, measurement and application, with a more specific interest in determining the factors that question the financial forecasting properties of current simple models, especially with dynamic environmental circumstances. In our analysis, we have found that current empirical models are frequently ineffective because they lack the explicit ability to integrate the complex/coupled nature of microstructural properties (e.g., fractal geometry and nano-porosity) and compositional differences (e.g., organic matter). More so, the synthesis shows that there is a fundamental conflict in modeling, whereas the more intricate a conventional empirical model gets, the less accurate it becomes, whereas sophisticated data-driven methods such as Deep Learning are much more effective at making predictions. As a consequence, this review confirms that one of the main future research needs should be the creation of coherent constitutive models that will combine mechanistic controls (fractal theory) and advanced AI prediction. Most importantly, the implications in practice reveal that the neglect of such coupled considerations directly compromises the validity of long-term geotechnical performance forecasts, that is, in relation to slope stability and foundation resilience to moisture changes caused by climate change. The review gives the conclusion by recommending that laboratory results should be immediately validated at a field scale to bring together the gap between theory and engineering design.
Deep mixing technology is used to improve the engineering properties of soil. In this review, previous studies on the properties and problems of weak soils were collected and explained, focusing on silty soils found globally and locally. The study also includes a discussion of physical and chemical improvement methods, specifically (cement columns). The advantages of deep mixing technology are also covered from an engineering and economic point of view, as well as its relationship to the environmental impact, as it is one of the sustainable development techniques due to its use of environmentally friendly materials. In addition, one of the objectives of this research is to study the methods of adding cement, whether in the form of powder (dry method) or mortar (wet method). A comparison was made between them to clarify the advantages and disadvantages. It was found that what distinguishes the use of the dry method from the wet method is that the former is more common. The method's effectiveness depends on the soil's moisture content, so the technique is ineffective in soils with less than 30% water content. As cement hydration produces a cementitious gel (CSH) that binds soil particles together, leading to early strength gain, pozzolanic reactions cause increased shear strength and decreased soil compressibility. Finally, some recommendations are included in this article to understand the behavior of cement columns in improving soil and avoiding problems