الفهرس 
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Abstract
Soil liquefaction is the term used to describe the transformation of granular soils from a solid state to a viscous state due to a reduction of strength resulting from increased pore-water pressure. A study of soil liquefaction induced by the Vision Cone Penetration Test (Vis-CPT) is presented in this study which named as The CPT-Induced Liquefaction. The CPT-Induced Liquefaction is caused by the Vis-CPT advancing through loose saturated sand. During penetration through saturated loose sand, the soil skeleton contracts and due to impeded drainage the pore pressure increases. These conditions lead to soil liquefaction and flow of particles. The CPT-Induced Liquefaction can be seen clearly by using Vis-CPT camera through a sapphire window. While the Vis-CPT is advancing, soil particle motion can be observed and the particle velocities can be calculated. The Vision Cone Penetration Test (Vis-CPT) allows soil to be observed in-situ. Since the first generation of the Vis-CPT, Hryciw and Raschke (1997) observed liquefaction during Vis-CPT advance. The CPT outputs include pore water pressure, tip resistance, and sleeve friction. All those obtained data build a strong data bank about the soil behavior which helps to study the causes of Vis-CPT-Induced Liquefaction. Actually the idea of this research has been activated during the using of Vision Cone Penetration technique at field, an important observation was revealed during the field study at Griffin site (Indiana State) which may give a greater potential value of the Vis-CPT to soil liquefaction assessment. This study can mainly be divided into three research mainstreams, namely field testing by the Vis-CPT, numerical analysis, and experimental verification. The fist stream is the field testing; many vision cone penetration (Vis-CPT) tests were performed to develop a data base. The Vis-CPT tests were performed at different sites including, Griffin, Indiana, Azalia, Indiana, and Lawrence, Kansas. Soil particles movements in many directions were observed in the vision data. The second stream of this study is numerical simulation using the finite element method (FEM). Abaqus is the commercial finite element software which was utilized in this study. A previously developed elastic-plastic constitutive modelby Susila (2005) was used to model the soil. The numerical study included the effects of cone advance velocity on excess pore water pressure development and tip resistance. Also a parametric study of permeability, void ratio, and angle of internal friction was performed. The numerical results for CPT advance through saturated soil are presented. The reason for the numerical analysis was to determine if the CPT velocity increases the excess pore water pressure as well as to study the occurrence of the liquefaction phenomenon. The tip resistance and excess pore water pressure are two important factors in determining if a soil is liquefiable or not. So another goal of this study is to proof if the CPT advance can liquefy the soil under a given set of material and state parameters. The answer for that argument is that the CPT velocity is the main factor which increases the pore water pressure. The third and last stream of this research is experimental verification. The observed CPT-induced liquefaction phenomenon needs to be verified using experimental simulation. This involved the modification of a previously built large Half-Axisymmetric Triaxial (HAT) calibration chamber and performing half-CPT tests in semi-cylindrical inclusions in Ottawa 20-30 sand. The HAT uses a half cone which helps observation of soil particle motion through a plexiglas plate. The geometric shape and dimensions of the half cone are the same as used in the field and in numerical simulations. Video images of the experiments were recorded using high resolution digital camera so that the displacements or travel distances of individual soil particles in the vicinity of the CPT probe could be observed. Consequently, the experimental tests are very important to observe particles motion during advance in the lab and hereby confirmed field observations. Tests were performed of various soil relative densities, confining pressures, and moisture conditions.