Investigation of Elastic Properties of Fine-Grained Soil Stabilized with Lime and Fly Ash

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Investigation of Elastic Properties of Fine-Grained Soil Stabilized with Lime and Fly Ash

ارائه دهنده: Provider: Javad Mortezaei

اساتید راهنما: Supervisors: Mohammad Maleki (Ph.D)

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: دکتر وحیدرضا اوحدی دکتر قدیمی

زمان و تاریخ ارائه: Time and date of presentation: March, 16, 2021

مکان ارائه: Place of presentation:

چکیده: Abstract: For several decades, the amazing role of lime and cement in soil stabilization; has been studied, proven and used in practice in various projects. However, due to various technical, economic and environmental reasons, a variety of additives in soil stabilization operations based on lime or cement have been considered by researchers. Review studies show that these additives in some cases increase the unconfined compressive strength of stabilized soil and in some cases do not have a significant effect. One of the additives for soil Stabilization is fly ash and its admixture with Lime in stabilization operations has recently made lots of interest to researchers. According to review studies, the addition of aly ash to lime increase the unconfined compressive strength (UCS) and rupture strain of stabilized soil. The seismic design of buildings based on the lime and fly ash stabilized soil bed depends on proper estimation of the parameters indicating the bed Stiffness. Stiffness changes as a function of the deformation field are usually provided by the shear modulus change curve as a function of shear deformation. The maximum shear modulus (G_max) has a key role in this regard and has been less considered by researchers based on review studies in the past. Therefore, the study of the behavior of deformation modulus and maximum shear modulus of the lime stabilized soil with 3, 5 and 7%; class F fly ash with 5, 10 and 15% and in unconfined and confined condition with stresses of 100, 200 and 400 kPa were among the goals pursued in this study. For this purpose, in this study, G_max of the soil stabilized with lime and fly ash with 28 days of curing under different influential factors has been studied using a triaxial device equipped with bender element. In addition, the correlation of G_max modulus has been investigated by measuring the deformation modulus (E_(s-50)) obtained from triaxial stress-strain curves. The results of this study showed that the resistance of fine-grained soil with a pulp sign of less than 10, has a 240% increase over the base soil in unconfined conditions in its optimal composition, i.e. soil stabilized with 5% lime and 15% ash. Also, in compounds containing 7% lime, the resistance compared to samples containing 5% lime, initially decreased, but it has taken an upward trend with an increase in ash content from 5 to 10 and 15. This shows that fly ash is able to reduce the harmful effects of lime in high percentages. On the other hand, the amount of deformation modulus is directly related to the amount of lime and fly ash. The highest values of modulus of deformation have been observed in the combination of 7% lime plus 5% and 10% fly ash. The maximum shear modulus increases with increasing fly ash content in all specimens. A noticeable decrease in the maximum shear modulus occurs by increasing the amount of lime from 5 to 7%. The maximum amount of shear modulus is found 654.3 MPa for stabilized soil related to the sample containing 5% lime and 15% fly ash at a confined stress of 400 kPa. The deformation modulus as well as the maximum shear modulus have direct relationship with the confined stress, and the highest values of this modulus have been reported in the confined stresses of 200 and 400 kPa. The stiffness ratio ( G_max/E_(s-50)) decreases as the confined stress increases in most specimens. The results show that soil stiffness at the level of large deformations arising from the results of static triaxial experiments correlates with the stiffness obtained from small strain experiments. Key Words: Stabilized soil, Maximum shear modulus, Deformation modulus, Lime, Fly ash, Bender element

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