Berna Unutmaz

Soil Uncertainty and Its Influence on Simulated G/Gmax and Damping Behavior

In this paper, recently developed probabilistic elastoplasticity was applied in simulating cyclic behavior of clay. A simple von Mises elastic–perfectly plastic material model was used for simulation. Probabilistic soil parameters, elastic shear modulus (Gmax) and undrained shear strength (su), needed for the simulation were obtained from correlations with the standard penetration test (SPT) N-value. It has been shown that the probabilistic approach to geo-material modeling captures some of the important aspects—the modulus reduction, material damping ratio, and modulus degradation—of cyclic behavior of clay reasonably well, even with the simple elastic–perfectly plastic material model.

Simulation of contaminant migration through a soil layer due to an instantaneous source

Analytical and numerical simulation models help civil and environmental engineering students to understand the physical and chemical processes that influence contaminant transport through a saturated soil layer, including advective and dispersive transport as well as sorption. The basic principles for simulation of contaminant migration through a saturated soil were introduced. Using the spreadsheet program MS Excel, based on existing analytical solution for two‐dimensional transport of contaminants in a saturated soil layer, concentrations at several coordinates at several times were calculated. A MATLAB code was developed using finite difference approach for numerical solution. The programming steps followed for analytical and numerical solutions were explained. The analytical and numerical solution was compared. An example of the simulation models for the contaminant transport through a saturated soil layer is given. The study shows that the analytical solution and the numerical solution, for the given problem, match in an acceptable range.

Liquefaction Triggering Response Under Wave-Induced Cyclic Loading

Cyclic response of saturated sands has become one of the most popular topics in geotechnical earthquake engineering due to the consequent damages of earthquakes. Related to this topic, detailed performance of offshore structures founded on saturated sands under the effect of cyclic loads carries vital economic importance. It is well-known that besides seismic loading; storm, wind and/or submarine slope failures have direct effect on the strength and deformation behavior of soils through induced sea-level variations. This study summarizes the results of a series of cyclic triaxial tests performed to simulate the behavior of fully-saturated coarse grained sands under wave-induced cyclic loading. Evaluating the excess pore water pressure generation and shear strain accumulation response along with the number of cycles required for liquefaction triggering for sands, having different relative densities, and being subjected to various cyclic shear stress ratios (CSR), the following observations are made; i) number of cycles to liquefaction increases with increasing relative density and decreasing CSR, ii) for medium dense foundation and backfill soils, liquefaction is not triggered for CSR values less than 0.1 under reasonable number of cycles, and iii) number of cycles to liquefaction decreases significantly for soils subjected to CSR values exceeding of 0.25. These results were used to express the effects of the variation in water level and liquefaction triggering response in terms of in-situ test data, wave height and number of waves for the granular backfill of a sample offshore structure.Copyright

Assessment of Structure -Induced Liquefaction Triggering

Although there exist s some consensus regarding seismic soil liquefactio n triggering assessment of free field soil sites, assessing liquefaction triggering potential beneath building foundations still stays as a controversial and a difficult issue. Liquefaction triggering potential under building foundations is affected by bot h the static and cyclic stress state of the soil medium. As part of these studies, conventionally used