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Temperature significantly affects the mechanical properties of geomaterials, particularly the creep behavior of soft clayey soils. Thus, an appropriate constitutive model to describe the time-dependent stress-strain behavior of clayey soils at various temperatures is necessary. This study performed temperature-controlled oedometer tests on two clayey soils: Hong Kong marine deposit (HKMD) and kaolinite clay (kaolin). The thermally-induced strain and creep strain rates under different temperature paths were investigated and discussed. A novel one-dimensional (1D) thermal elastic viscoplastic (TEVP) model was developed based on an existing 1D elasto viscoplastic (EVP) model. In the proposed model, the viscoplastic strain rate of soils can be described using three state variables: effective stress, strain, and temperature. The proposed model can be conveniently implemented in creep analysis with the equivalent time concept. The prediction results of the TEVP model were consistent with the experimental data for HKMD and kaolin. [ABSTRACT FROM AUTHOR]

In most marine reclamation projects, sand fill is placed directly on soft marine seabed soils. The sand particles can easily penetrate into the soft marine soils, and the soft soil can also move into the pore spaces inside the sand at the initial contact interface between the sand and the soft marine soil. In this case, the permeability and the volume of the sand above the initial surface are reduced. To avoid this problem, a geotextile separator is often placed on the surface of the soft marine soils before placing the sand. In this study, a two-dimensional physical model is utilized to study the geotextile separator effects. The initial conditions of a clayey soil, sand fill, and surcharge loading were kept the same in the physical model test with the only difference being that a geotextile separator was either placed on the clay surface or omitted. The settlements of the initial interface were recorded and compared for the two cases without or with the geotextile separator. The particle size distribution of the soils taken across the interface zone for different time durations was then measured, analyzed, and compared. Based on an analysis of the results, the sand percolation depth was 40 mm and fine particle suffusion was apparent when the sand was placed directly on the marine slurry surface without a geotextile separator. However, when a geotextile separator was used sand percolation was avoided, and the fine particle suffusion was effectively diminished. A relative fine particle fraction is defined to illustrate the migration of fine particles from the clay to the sand soils. The fine particle percentages of the Hong Kong Marine Deposits–sand mixtures were calculated for the cases with and without a geotextile separator using an empirical formula and micromechanical modeling to obtain a better understanding of the effects of geotextile separators in practice. [ABSTRACT FROM AUTHOR]

The thermal effects on geomaterials, especially on clayey soils are getting increasing concerns in many geotechnical applications. To study the effects of temperature on the stress-strain behaviour of Hong Kong marine deposits (HKMD), a series of temperature-controlled experiments were carried out. Oedometer and constant-rate-of-strain consolidation tests under temperatures from 10 °C to 60 °C were conducted on both intact and reconstituted HKMD considering different temperatures and stress paths. The effects of temperature history on the compression curves, thermally induced strain, and the characteristics of creep are revealed and discussed. The concept of virgin heating is proposed for interpreting the thermal plastic deformation. With increasing temperature, the creep coefficient is found to decrease while the creep strain rate increases. Consolidated undrained triaxial tests were performed on intact and reconstituted HKMD under different strain rates and temperature conditions. Under constant temperature, the undrained shear strength of HKMD is not significantly influenced by temperature. In triaxial tests subjected to step-changed temperature, the undrained heating causes a significant reduction of effective stress and rise of porewater pressure in HKMD. Finally, microscopic investigations with mercury intrusion porosimeter and scanning electron microscope are presented and discussed in this paper. It is found that the micropores of HKMD are evolutional with temperature. • Temperature and time dependent behaviour of HKMD is investigated. • Compression curves and shear strength are related to temperature conditions. • Thermal elastic visco-plastic correlations are developed from the test results. • Micro-pores are influenced by temperature according to SEM and MIP tests. • The study will be useful for understanding the thermal effects on clayey soils. [ABSTRACT FROM AUTHOR]