Search

Unlike other thermo-mechanical soil responses, the effects of temperature on residual shear strength of soils are not well understood. Previous studies on temperature effects on residual shear strength show some contradictory findings that might be attributed to the sample's mineralogical composition and the testing procedure. This thesis aims to contribute to the understanding of (1) the temperature effects on the liquid limit of cohesive soils, (2) the impact of testing procedure on temperature-dependent residual friction angle, and (3) temperature effects on residual friction angle of soils. The fall cone tests are used to determine temperature effects on the liquid limit, while a temperature-modified ring shear apparatus is used to evaluate the residual friction angle in this study. To assess the impact of the testing procedure, the temperature is changed to 50°C at three different instants: before consolidation, before preshearing, and after preshearing; the resulting residual friction angles are assessed and compared. The effects of temperature on residual friction angle of soils are also investigated by changing the temperature in the ring shear apparatus to 10°C, 20°C, 40°C, and 50°C before consolidation. The study found that the impacts of temperature on liquid limit is mineralogy dependent. Also, the instant at which temperature change occurs in ring shear tests was found to be insignificant in terms of the residual friction angle. Moreover, the findings of the ring shear experiments suggest that clay mineralogy is important in the study of temperature-dependent residual friction angle of cohesive soils. Antigorite-rich soils may experience up to 50% changes in their residual friction angle, while soils with other clay minerals may experience less than 20% variations over a temperature range from 10 to 50 °C.

Success in geotechnical analysis, design, and construction invariably requires that we have proper knowledge and understanding of (1) the strength, (2) the fluid flow properties, and (3) the stress-deformation behavior of the earth materials. These important engineering properties are primarily determined by the components and structure of a soil, which also dictate the soil's responses in an electromagnetic field. As a nondestructive technique, the electromagnetic property measurement offers a promising approach to characterize earth materials and identify the effects of changes in environments. However, despite many investigations in the last several decades, the relationship between the frequency-dependent electromagnetic properties of soils and their components and structure are still not well understood. Hence, estimation of engineering properties of a soil in a quantitative way from electromagnetic measurements can be uncertain. In this research several tasks have been accomplished: (1) Development of a physically based model that provides a means of investigating the coupled effects of important polarization mechanisms on soil electromagnetic properties, and a means of relating the electromagnetic properties of a soil to its fines content, clay mineralogy, anisotropy, degree of flocculation and pore fluid chemistry; (2) Proposal of a practically applicable method to determine the volumetric water content, specific surface area and pore fluid salt concentration simultaneously from the dielectric spectrum; (3) Deduction of the wide-frequency electromagnetic properties of a soil by measuring its responses to a step pulse voltage using time domain reflectometry (TDR); (4) Establishment of the relationships between the specific surface area and compressibility, residual shear strength and hydraulic conductivity. This study establishes a framework for quantifying soil engineering properties from their electromagnetic properties. If properly determined and interpreted, the electromagnetic properties can also provide insights into the causes of soil property changes over time and can be very useful in studying the effects of biological factors in geotechnical engineering, a field that may offer great potential for future advances.