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Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Sadrekarimi, Abouzar

Abstract

Geotechnical engineering design and analysis require sound identification and characterization of in-situ soil. To characterize is to gather information about the engineering properties of a particular soil which will affect the performance of any structure built on it. As a result of complications associated with the retrieving of undisturbed samples of cohesionless soils, calibration chamber-based experiments under controlled laboratory settings are used for the determination of several geotechnical engineering parameters. The capability of a reduced-scale calibration chamber-based cone penetration testing system along with shear wave velocity and electrical resistivity measurements, to better characterize in-situ soil is examined in this study. Reconstituted clean sand specimens are anisotropically consolidated to different levels of consolidation relative densities to ideally simulate in-situ field conditions. This measured parameters such as cone tip resistance (qc), sleeve friction (fs), shear wave velocity (Vs) and bulk electrical resistivity of soil (ρs) at different consolidation stresses and relative densities have been used to establish improved characterization techniques for any site-specific pre-design geotechnical engineering analyses on silica-based cohesionless soil.

Summary for Lay Audience

This study is an attempt to characterize silica sands under different conditions of loading, vibration, etc. This behavioural analysis or characterization, therefore, provides, an insight into its overall strength, stiffness, rigidity, etc. in the form of engineering parameters. The obtained parameters are again correlated with each other to develop new relationships for a particular soil type or to compare them with previous relevant studies to confirm the potency of the methods that were used to obtain them. This study is one such example of laboratory-controlled testing of a particular sand.

Soil specimens are prepared to a particular uniform dimension. The mass of soil used in the specimens is varied in order to obtain loose, medium dense and dense specimens. Following a water saturation process, the specimens are exposed to high pressures. During the pressurization, the specimen loses a certain amount of water and as a result of the decrease in pore volume, the height of the specimen decreases. Under such stresses, a thin metallic rod with a cone at its tip is mechanically pushed into the soil as we record the resistances felt by the cone penetrometer. During the penetration, resistance is felt at the tip of the cone (qc) and along the sidewalls of the probe due to the friction it overcomes while on its way (fs). If we cause a vibration in the form of a wave, on the top layer of the specimen, the bottom layer will experience the force wave as it is transmitted through the adjacent particles, and the corresponding speed of travel is known as shear wave velocity (Vs). Moreover, if we apply a source of electric current to pass through a soil specimen, the charge will be transmitted across the specimen through the pore water between the particles, unlike the Vs, giving a measure of the electrical resistivity of the soil specimen (ρ) at that particular loading condition.

Therefore, these parameters have been investigated and explored in detail in this study to have a better understanding of the behaviour of the tested material under different conditions of loading.

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