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The physical and mechanical behavior of soil polymer composites tightly depends on the properties and structures of both soil and polymer. This study aims to investigate the effect of glass transition temperature as one of the most important characteristics of adhesive resins of acrylic polymers on the geotechnical behavior of soils that have not been fully covered by previous studies. To achieve that, three similar copolymers of methyl methacrylate-co-butyl acrylate with different glass-transition temperatures of 1°C, 33°C, and 51°C were synthesized, and two representative specimens of cohesive (kaolinite clay) and noncohesive (sand) soils were chosen to perform a full investigation of the consequential changes in the physical and mechanical behavior. A series of laboratory tests, including the Atterberg limits tests, the unconfined compressive strength tests, direct shear tests in soaked and unsoaked conditions, swelling tests, and odometer tests, were conducted on untreated and treated soils with synthesized polymers. The results showed a salient enhancement in the cohesion and the unconfined compressive strength value of both soils. However, the polymer with a glass-transition temperature near to ambient temperature led to a greater increase in the compressive and shear strength of stabilized soil among its peers. Samples treated with the polymer having the lowest glass transition temperature revealed a more compression index (i.e., obtained from odometer tests) and lower unconfined compressive strength. It is also observed that the swelling index and swelling pressure decreased marginally with increasing the glass transition temperature. [ABSTRACT FROM AUTHOR]

Mechanical behaviour of the soil–structure interface plays a major role in the shear characteristics and bearing capacity of foundations. In thermoactive structures, due to nonisothermal conditions, the interface behaviour becomes more complex. The objective of this study is to investigate the effects of temperature variations on the mechanical behaviour of soils and the soil–structure interface. Constant normal load (CNL) and constant normal stiffness (CNS) tests were performed on the soil and soil–structure interface in a direct shear device at temperatures of 5, 22, and 60 °C. Fontainebleau sand and kaolin clay were used as proxies for sandy and clayey soils. The sandy soil was prepared in a dense state and the clayey soil was prepared in a normally consolidated state. Results show that the applied thermal variations have a negligible effect on the shear strength of the sand and sand–structure interface under CNL and CNS conditions, and the soil and soil–structure interface behaviour could be considered thermally independent. In clay samples, an increase in the temperature increased the cohesion and consequently the shear strength, due to thermal contraction during heating. The temperature rise had less impact on the shear strength in the case of the clay–structure interface than in the clay samples. The adhesion of the clay–structure interface is less than the cohesion of the clay samples. [ABSTRACT FROM AUTHOR]

There are various methods for improving the engineering properties of weak soils among which the usage of chemical additives is one of the most important ones. Considering sepiolite as an environmental friendly material and its unique physiochemical characteristics, this substance has been used as an additive for soil improvement in this study. For this purpose, in addition to soil identification tests, in order to examine the effect of changes in the percentage of sepiolite additive, a set of tests has been done including Atterberg limits, modified compaction, uniaxial compressive strength, pH, direct shear and permeability test on sandy clay and clayey sand soils. Furthermore, scanning electron microscopy (SEM) and x-ray diffraction (XRD) tests have been performed to investigate the microstructure of non-stabilized and stabilized soil. According to the results, with increasing the additive percentage and the curing time, the uniaxial compressive strength of the soil increased. The uniaxial strength in the clayey sand soil rose up to six times larger than that of the initial strength of the soil. However, the maximum strength enhancement in the sandy clay soil was up to three times the initial value. Sepiolite (above 5%) has improved soil shear strength parameters including cohesion and internal friction angle. The increase in the additive content led to diminished permeability in soil. Further, the elevation of the sepiolite content in the soil resulted in enhanced liquid and plastic limits of soil. Microstructural investigations indicated that the reason of improvement in strength parameters of soil was the incidence of chemical reactions including ion exchange, flocculation and production of calcium-silicate-hydrate (CSH) and calcium-aluminate-hydrate (CAH) gels. Further, sepiolite fiber resulted in enhanced strength by filling the pores and void spaces of soil. • Sepiolite is an environmentally friendly material to stabilize the soils. • Increasing the sepiolite content during the curing time, increases UCS of the soil. • Sepiolite fibers act like bridges and connect different parts of soil. • CSH and CAH are products of chemical reactions between sepiolite and soil. [ABSTRACT FROM AUTHOR]

Focuses on a study that discussed a four-parameter model that can represent the shear modulus factors and damping coefficients for granular soils. Information on nonlinear soil behavior; Effect of confining pressure on modulus and damping; Experimental data on cohesionless soils; Details on the MIT-S1 stress soil model for clays and sands.