Review of the literature related to the mixture of shredded tire and sand shows that,despite of the increase in shear strength due to addition of tire chips,granulated rubber causes reduction in shear strength of sand...Review of the literature related to the mixture of shredded tire and sand shows that,despite of the increase in shear strength due to addition of tire chips,granulated rubber causes reduction in shear strength of sand.In this study,the shear behavior of mixtures of fine-grained sand and 1-5 mm granulated rubber is investigated.Sixty direct shear tests were conducted on sandegranulated rubber mixtures with various rubber contents(0%,5%,10%,20% and 30%) at different relative densities(50%,70% and 90%) and different normal stresses(34.5 kPa,54.5 kPa,74.5 kPa and 104.5 kPa).The obtained results show that the granulated rubber improves the shear strength of fine-grained sand at medium relative density and low normal stress.The degree of improvement in shear strength is a function of rubber content,relative density and normal stress.The results show that at relative density of 50%,by adding 5% granulated rubber,the internal friction angle of sand increases from 35.1° to 39.2°.However,at relative densities of 70% and 90%,addition of granulated rubber to sand decreases its internal friction angle.The results also indicate that the behavior of sand becomes more ductile with increasing granulated rubber content.Adding granulated rubber leads to greater yielding strain and less tangent stiffness of sand.The maximum dilation angle decreases with the decrease in granulated rubber content.The stress ratio of sample at critical state(ψ= 0°) decreases with increasing granulated rubber content.展开更多
Similar to free-standing pile groups, piled raft foundations are conventionally designed in which the piles carry the total load of structure and the raft bearing capacity is not taken into account. Numerous studies i...Similar to free-standing pile groups, piled raft foundations are conventionally designed in which the piles carry the total load of structure and the raft bearing capacity is not taken into account. Numerous studies indicated that this method is too conservative. Only when the pile cap is elevated from the ground level,the raft bearing contribution can be neglected. In a piled raft foundation, pileesoileraft interaction is complicated. Although several numerical studies have been carried out to analyze the behaviors of piled raft foundations, very few experimental studies are reported in the literature. The available laboratory studies mainly focused on steel piles. The present study aims to compare the behaviors of piled raft foundations with free-standing pile groups in sand, using laboratory physical models. Cast-in-place concrete piles and concrete raft are used for the tests. The tests are conducted on single pile, single pile in pile group, unpiled raft, free-standing pile group and piled raft foundation. We examine the effects of the number of piles, the pile installation method and the interaction between different components of foundation. The results indicate that the ultimate bearing capacity of the piled raft foundation is considerably higher than that of the free-standing pile group with the same number of piles. With installation of the single pile in the group, the pile bearing capacity and stiffness increase. Installation of the piles beneath the raft decreases the bearing capacity of the raft. When the raft bearing capacity is not included in the design process, the allowable bearing capacity of the piled raft is underestimated by more than 200%. This deviation intensifies with increasing spacing of the piles.展开更多
It is well known that the cemented sand is one of economic and environmental topics in soil stabilization. In this instance, a blend of sand, cement and other materials such as fiber, glass, nanoparticle and zeolite c...It is well known that the cemented sand is one of economic and environmental topics in soil stabilization. In this instance, a blend of sand, cement and other materials such as fiber, glass, nanoparticle and zeolite can be commercially available and effectively used in soil stabilization in road construction. However, the influence and effectiveness of zeolite on the properties of cemented sand systems have not been completely explored. In this study, based on an experimental program, the effects of zeolite on the characteristics of cemented sands are investigated. Stabilizing agent includes Portland cement of type II and zeolite. Results show the improvements of unconfined compressive strength （UCS） and failure properties of cemented sand when the cement is replaced by zeolite at an optimum proportion of 30% after 28 days. The rate of strength improvement is approximately between 20% and 78%. The efficiency of using zeolite increases with the increases in cement amount and porosity. Finally, a power function of void-cement ratio and zeolite content is demonstrated to be an appropriate method to assess UCS of zeolite-cemented mixtures.展开更多
文摘Review of the literature related to the mixture of shredded tire and sand shows that,despite of the increase in shear strength due to addition of tire chips,granulated rubber causes reduction in shear strength of sand.In this study,the shear behavior of mixtures of fine-grained sand and 1-5 mm granulated rubber is investigated.Sixty direct shear tests were conducted on sandegranulated rubber mixtures with various rubber contents(0%,5%,10%,20% and 30%) at different relative densities(50%,70% and 90%) and different normal stresses(34.5 kPa,54.5 kPa,74.5 kPa and 104.5 kPa).The obtained results show that the granulated rubber improves the shear strength of fine-grained sand at medium relative density and low normal stress.The degree of improvement in shear strength is a function of rubber content,relative density and normal stress.The results show that at relative density of 50%,by adding 5% granulated rubber,the internal friction angle of sand increases from 35.1° to 39.2°.However,at relative densities of 70% and 90%,addition of granulated rubber to sand decreases its internal friction angle.The results also indicate that the behavior of sand becomes more ductile with increasing granulated rubber content.Adding granulated rubber leads to greater yielding strain and less tangent stiffness of sand.The maximum dilation angle decreases with the decrease in granulated rubber content.The stress ratio of sample at critical state(ψ= 0°) decreases with increasing granulated rubber content.
文摘Similar to free-standing pile groups, piled raft foundations are conventionally designed in which the piles carry the total load of structure and the raft bearing capacity is not taken into account. Numerous studies indicated that this method is too conservative. Only when the pile cap is elevated from the ground level,the raft bearing contribution can be neglected. In a piled raft foundation, pileesoileraft interaction is complicated. Although several numerical studies have been carried out to analyze the behaviors of piled raft foundations, very few experimental studies are reported in the literature. The available laboratory studies mainly focused on steel piles. The present study aims to compare the behaviors of piled raft foundations with free-standing pile groups in sand, using laboratory physical models. Cast-in-place concrete piles and concrete raft are used for the tests. The tests are conducted on single pile, single pile in pile group, unpiled raft, free-standing pile group and piled raft foundation. We examine the effects of the number of piles, the pile installation method and the interaction between different components of foundation. The results indicate that the ultimate bearing capacity of the piled raft foundation is considerably higher than that of the free-standing pile group with the same number of piles. With installation of the single pile in the group, the pile bearing capacity and stiffness increase. Installation of the piles beneath the raft decreases the bearing capacity of the raft. When the raft bearing capacity is not included in the design process, the allowable bearing capacity of the piled raft is underestimated by more than 200%. This deviation intensifies with increasing spacing of the piles.
文摘It is well known that the cemented sand is one of economic and environmental topics in soil stabilization. In this instance, a blend of sand, cement and other materials such as fiber, glass, nanoparticle and zeolite can be commercially available and effectively used in soil stabilization in road construction. However, the influence and effectiveness of zeolite on the properties of cemented sand systems have not been completely explored. In this study, based on an experimental program, the effects of zeolite on the characteristics of cemented sands are investigated. Stabilizing agent includes Portland cement of type II and zeolite. Results show the improvements of unconfined compressive strength （UCS） and failure properties of cemented sand when the cement is replaced by zeolite at an optimum proportion of 30% after 28 days. The rate of strength improvement is approximately between 20% and 78%. The efficiency of using zeolite increases with the increases in cement amount and porosity. Finally, a power function of void-cement ratio and zeolite content is demonstrated to be an appropriate method to assess UCS of zeolite-cemented mixtures.
