Final Report Summary - LIQUEFCTN SILTYSANDS (INFLUENCE OF SILT CHARACTERISTICS ON LIQUEFACTION BEHAVIOR OF SILTY SANDS)
The main goal of this research project is to investigate the role silt size grains available in many natural sand deposits on liquefaction behavior of those sandy soils. This is especially important considering that there had been many liquefaction cases involving silty sands in different parts of the world after various earthquakes including 1980 Chlef(Algeria), 1989 Loma Prieta(California), 1999 Chi-Chi(Taiwan), 1999 Kocaeli(Turkey), 2011 Tohoku(Japan) and 2011 Christchurch(New Zeland) earthquakes. It is also important to note that liquefaction could occur under both static and/or dynamic loading conditions.
It was shown that gradation of silty sands influence their volume change behavior in drained conditions [Monkul (2013),“Influence of gradation on shear strength and volume change behavior of silty sands”, Geomechanics and Engineering, 5(5), 401-417]. Later, it was also shown that volumetric compressibility (mv) of silty sands can be used as an indicator for their static liquefaction potential [Monkul et al. (2014),“Compressibility as an indicator of liquefaction potential”, Geotechnical Engineering Journal of SEAGS-AGSSEA, 45 (4), 73-77]. As project progressed, it was found that base sand gradation had a significant effect on the static liquefaction of clean and silty sands as well. Furthermore, two equations were developed and proposed to show the relationship between undrained shear strength with coefficient of uniformity depending on the liquefaction response of soils (i.e. one for stable and temporarily liquefied soil specimens, the other for liquefied ones) [Monkul et al. (2016a),“ Influence of coefficient of uniformity and base sand gradation on static liquefaction of loose sands with silt”, Soil Dynamics and Earthquake Engineering, in review]. Meanwhile, it was discovered that variations in shape characteristics [e.g. angularity] of silt grain matrix in sandy soils could also influence their liquefaction behavior [Etminan et al. (2015),“Silt influence on static liquefaction of sands”. Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, Edinburgh, U.K.]. It was also found that there is a coupled relationship between various silt characteristics (i.e. fines content (FC), shape, gradation) and liquefaction [Monkul et al. (2016b),“ Coupled influence of content, gradation and shape characteristics of silts on static liquefaction of loose silty sands”, Soil Dynamics and Earthquake Engineering, in review; Etminan et al. (2016),“Effect of silt size and gradation on cyclic liquefaction of sands”, Proceedings of the 4th International Conference on New Developments in Soil Mechanics and Geotechnical Engineering].
The re-integration of Dr. Monkul to Europe and his host institution Yeditepe University is going well. Dr. Monkul has formed a compact research group involving himself and a graduate research assistant researching full time on this project. The graduate research assistant, Mr. Etminan, is also doing his Ph.D. at Istanbul Technical University, where this project became his Ph.D. topic. Dr. Monkul is co-supervising Mr. Etminan’s Ph.D. studies with Dr. Aykut Senol and meanwhile developing collaboration with Istanbul Technical University.
During this period, Dr. Monkul became the director of the Soil Mechanics Laboratory at Yeditepe University. Dr. Monkul was also promoted to Associate Professor, and continues his teaching activities and research at the Civil Engineering Department.
It was shown that gradation of silty sands influence their volume change behavior in drained conditions [Monkul (2013),“Influence of gradation on shear strength and volume change behavior of silty sands”, Geomechanics and Engineering, 5(5), 401-417]. Later, it was also shown that volumetric compressibility (mv) of silty sands can be used as an indicator for their static liquefaction potential [Monkul et al. (2014),“Compressibility as an indicator of liquefaction potential”, Geotechnical Engineering Journal of SEAGS-AGSSEA, 45 (4), 73-77]. As project progressed, it was found that base sand gradation had a significant effect on the static liquefaction of clean and silty sands as well. Furthermore, two equations were developed and proposed to show the relationship between undrained shear strength with coefficient of uniformity depending on the liquefaction response of soils (i.e. one for stable and temporarily liquefied soil specimens, the other for liquefied ones) [Monkul et al. (2016a),“ Influence of coefficient of uniformity and base sand gradation on static liquefaction of loose sands with silt”, Soil Dynamics and Earthquake Engineering, in review]. Meanwhile, it was discovered that variations in shape characteristics [e.g. angularity] of silt grain matrix in sandy soils could also influence their liquefaction behavior [Etminan et al. (2015),“Silt influence on static liquefaction of sands”. Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, Edinburgh, U.K.]. It was also found that there is a coupled relationship between various silt characteristics (i.e. fines content (FC), shape, gradation) and liquefaction [Monkul et al. (2016b),“ Coupled influence of content, gradation and shape characteristics of silts on static liquefaction of loose silty sands”, Soil Dynamics and Earthquake Engineering, in review; Etminan et al. (2016),“Effect of silt size and gradation on cyclic liquefaction of sands”, Proceedings of the 4th International Conference on New Developments in Soil Mechanics and Geotechnical Engineering].
The re-integration of Dr. Monkul to Europe and his host institution Yeditepe University is going well. Dr. Monkul has formed a compact research group involving himself and a graduate research assistant researching full time on this project. The graduate research assistant, Mr. Etminan, is also doing his Ph.D. at Istanbul Technical University, where this project became his Ph.D. topic. Dr. Monkul is co-supervising Mr. Etminan’s Ph.D. studies with Dr. Aykut Senol and meanwhile developing collaboration with Istanbul Technical University.
During this period, Dr. Monkul became the director of the Soil Mechanics Laboratory at Yeditepe University. Dr. Monkul was also promoted to Associate Professor, and continues his teaching activities and research at the Civil Engineering Department.