Determination of dynamic behavior characteristics of silty soils during and after earthquake
Project no. 22457 · Status: Kapanmış · 2021
Summary
<p>In the past years, it has been observed that non-plastic and low plasticity silts liquefied as well as sands during earthquakes. However, testing on siltY soils is very difficult compared to sand and clay soils. Generally, silts is thought to behave like sand or clay, however it is a transition material between sand and clay so does not behave exactly like clay or sand. Compared to this complex structure of silty soils, studies on the dynamic behavior of silt are still limited today. During the earthquake, excess pore water pressure is formed on the soils due to dynamic effects and this excess pore water pressure formed after the earthquake is drained. However, the fact that the hydraulic conductivity and permeability of silts are quite low compared to sands causes the excess pore water pressure formed during the earthquake to be drained later than sand soils. This excess pore water pressure causes delay of settlements and decrease in shear strength after earthquake and causes bigger structural problems. For this reason, it is important to examine the behavior of silts after dynamic effects. In addition, the effect of foreshocks and aftershocks on the dynamic behavior of silt has not been investigated in the literature.</p><p>Within the scope of this project, small strain tests with increasing stress amplitüde, liquefaction tests and post-liquefaction monotonic tests were carried out on silt soils with 4 different index properties at two different density (void ratio). The specimens were prepared by moist tamping method. Some of the experiments were carried out in accordance with JGS- 0541-2000 and JGS- 0542-2000 (Japanese Geotechnical Society) standards, and on some specimens, deformation and liquefaction tests were carried out in accordance with JGS standards after 20 cycles of loading at different amplitudes in order to simulate the earthquake. In addition, in order to determine the shear strength change after liquefaction, monotonic loading was carried out after liquefaction. Although the dynamic behavior of fine-grained soils is generally evaluated depending on the plasticity index, it has been observed that mineralogy and activity rather than plasticity are also of great importance in dynamic behavior.</p>