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Collapsible soils such as gypseous soil are problematic in geotechnical engineering because their volume changes significantly upon saturation. Foundations constructed on gypseous soil undergo sudden and large settlement if the underlying soil experiences unanticipated moisture. The present study aims to improve the gypseous soil behaviour so that it can be used to support shallow foundations. To understand the mechanisms of stabilisation better, a laboratory study is performed to evaluate how polyurethane foam in different amounts influences the volumetric strain, collapse potential and mechanical behaviour of gypseous soil. Physical models of a footing on treated gypseous soil with polyurethane foam are examined to determine the effective treatment zone. Based on the obtained results, 3% polyurethane foam can be recommended to improve the gypseous soil behaviour; the particular reason is its effectiveness in decreasing the change in volumetric strain and collapse potential. The present study develops a theoretical approach that depends on a non-dimensional parameter to predict the ultimate bearing capacity for a footing on the surface of treated gypseous soil using the existing conventional theories.

Machine foundations require significant attention from designers. The main goal of the design of machine foundation is to limit the amplitude displacement and not disturb the people who work near the machine. In some cases, if the design of machine foundations does not satisfy the acceptable value of the dynamic response (such as maximum amplitude of displacement), the stabilization of soil under the machine foundation may be used to decrease the amplitude of displacement. This paper outlines effect of stabilized soil under the foundation by cement on the displacement response of machine foundations. Three-dimensional analyses by using finite element method are carried out to investigate the effect of depth of stabilized layer with different percentage of cement content on the dynamic response of the machine foundation. In addition, the effect of area stabilized by cement material on the dynamic response of machine foundation is investigated. The results shown that, the dynamic response of machine foundations generally decreases with increasing the depth of soil layer stabilized with cement. A significant decrease in the displacement of machine foundations is occurred for the stabilized soil layer with a depth of two times of the width of foundation, and the optimum percentage of cement for stabilizing is 6%.

Soil stabilization with stone powder is a good solution for the construction of subgrade for road way and railway lines, especially under the platforms and mostly in transition zones between embankments and rigid structures, where the mechanical properties of supporting soils are very influential. Stone powder often has a unique composition which justifies the need for research to study the feasibility of using this stone powder type for ground improvement applications. This paper presents results from a comprehensive laboratory study carried out to investigate the feasibility of using stone powder for improvement of engineering properties of clays. The stone powder contains bassanite (CaSO4. ½ H2O), and Calcite (CaCO3). Three percentages are used for stone powder (1%, 3% and 5%) by dry weight of clay. Several tests are made to investigate the soil behavior after adding the stone powder (Atterberg limits, Standard Proctor density, Grain size distribution, Specific gravity, Unconfined Compressive test, and California bearing ratio test). Unconfined Compressive tests conducted at different curing. The samples are tested under both soaked and unsoaked condition. Chemical tests and X-ray diffraction analyses are also carried out. Stone powder reacts with clay producing decreasing in plasticity and The curves of grain size distribution are shifted to the coarse side as the stone powder percentage increase; the soil becomes more granular, and also with higher strength.