Browsing by Author "Fedakar, Halil I."

Now showing 1 - 2 of 2

Evaluation of Deformation Behavior of Sand-Clay Mixture under Traffic Loads
(AMER SOC CIVIL ENGINEERS, UNITED ENGINEERING CENTER, 345 E 47TH ST, NEW YORK, NY 10017-2398 USA, 2020) Fedakar, Halil I.; Cai, Wenjing; Rutherford, Cassandra J.; Cetin, Bora; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü
Vehicle traffic loading induces a heart-shaped stress path in deviatoric stress space [tau z theta to (sigma(z)-sigma(theta))/2], causing the rotation of principal stress direction acting on a soil element. A conventional triaxial test is not capable of applying the principal stress rotation induced by heart-shaped stress path and therefore, is not able to evaluate the behavior of soils accurately under traffic loads. However, a hollow cylinder test can simulate heart-shaped stress path imposed by traffic loading. In this study, the effect of heart-shaped stress path on the vertical deformation behavior of sand-clay mixture including 20% of clay by mass was experimentally investigated through hollow cylinder test. The tests in this study were conducted at three stages: i) saturation, ii) consolidation, and iii) shearing. The specimens were first saturated until Skempton's B >= 0.95 and then consolidated with K-0=0.5. Thereafter, the specimens were sheared under cyclic loadings involving vertical stress and shear stress. Experimental results indicate that the principal stress rotation induced by traffic loading significantly influences the permanent strain development in sand-clay mixture.
Unconfined compressive strength and freeze-thaw resistance of sand modified with sludge ash and polypropylene fiber
(TECHNO-PRESSPO BOX 33, YUSEONG, DAEJEON 305-600, SOUTH KOREA, 2017) Gullu, Hamza; Fedakar, Halil I.; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü
In recent years, the amount of sludge ash (SA) has considerably increased due to rapid urbanization and population growth. In addition, its storage in landfills induces environmental pollution and health problems. Therefore, its disposal in an environmentally friendly way has become more important. The main goal of this study is to investigate the reusability of sludge ash as an additive with polypropylene fiber (PF) to stabilize marginal sand based on the compressive strength performances from UCS tests. For this purpose, a series of UCS tests was conducted. Throughout the experimental study, the used inclusion rates were 10, 15, 20 and 30% for sludge ash and 0, 0.5 and 1% for polypropylene fiber by total dry weight of the sand+sludge ash mixture and the prepared samples were cured for 7 and 14 days prior to the testing. Freezing and thawing resistance of the mixture including 10% sludge ash and 0, 0.5 and 1% polypropylene fiber was also examined. On the basis of UCS testing results, it is said that sludge ash inclusion remarkably enhances UCS performance of sand. Moreover, the addition of polypropylene fiber to the admixtures including sand and sludge ash significantly improves their stress-strain characteristics and post-peak strength loss as well as UCS. As a result of this paper, it is suggested that sludge ash be successfully reused with polypropylene fiber for stabilizing sand in soil stabilization applications. It is also believed that the findings of this study will contribute to some environmental concerns such as the disposal problem of sludge ash, recycling, sustainability, environmental pollution, etc. as well as the cost of an engineering project.