جستجوی مقالات مرتبط با کلیدواژه « بهسازی و تثبیت خاک » در نشریات گروه « عمران »

In road projects, a suitable base for project execution is essential. Many of the soil types, such as wind sand, are not suitable for road building, and there is a need to carry out operations to prepare these soils for the base. In many cases, there is a need to switch to bed soil, but it is costly and will prolong the execution time of the project. Since it is challenging to reach ideal soil for road construction projects, soil improvement is being carried out. This is done in different ways, one of which is adding different materials to the soil. In this study, this method is used to stabilize the wind sand of Yazd. Two different types of glass fibers (type E and AR) have been used in this study. In order to perform the compressive test, the soil with both types of glass fibers was mixed in different percentages of 0.25, 0.5, 0.75, and 1 percent. The results showed that the percentage of optimum moisture increased by increasing the percentage of glass fibers. It should be noted that glass fibers did not affect the maximum dry soil weight. The direct shear test was done with the same percentages used in the compressive experiment. In this experiment, adding 0.75 and 0.5 percent of the type of AR and E to soil was selected as optimal for internal friction angle and cohesion, respectively. Also, using glass fibers of type AR in the studied soil had better results.

Poorly graded sandy soil could cause numerous geotechnical problems in large areas across the world. Weak soils have insufficient bearing capacity and this may be the cause of many issues in roads infrastructure, embankments, buildings foundation, and other geotechnical projects. Stabilizing the soil by chemical stabilizers like ordinary Portland cement (OPC) is one of the most conventional methods for enhancing the engineering proprieties of soil, usually by different percentages of binder/soil ratio. Some environmental and economical issues of utilizing OPC as binder are the serious concern of researches during few decades. Alkali-activated materials (AAM), with lower destructive impact on environment and more economical profits, have been one of the attractive materials as a new generation of binders recently. These materials can be utilize in different geotechnical applications such as: soil stabilizing, different kinds of mixing method, and grouting. The current study has aimed to evaluate the mechanical and durability properties of stabilized sandy soil by AAM, the used slag for AAM binder is Ground Granulated Blast furnace Slag (GGBS) and the slag is activated by different kinds of novel alkali activators. The activators are combination of Na2SiO3 and NaOH, Na2CO3 and Ca(OH)2, and Na2SO4 and Ca(OH)2; namely, Ac1, Ac2, and Ac3, respectively. In order to evaluate mechanical properties of stabilized soil samples, unconfined compressive strength (UCS) test, and to investigate the durability properties of stabilized soil samples, freezing-thawing cycles are applied to specimens. Additionally, scanning electron microscopy (SEM) test are implemented on Ac2- and Ac3-based stabilized samples to investigate the morphological aspects of stabilized soil. Studied parameters of this study are the effect of curing time on mechanical behavior of stabilized soil samples, and the effect of types of activator on mechanical and durability properties (volume changes and soil-cement losses) of stabilized soil samples. Curing time of 14, 28, and 90 days are considered for UCS test, and 28 days are considered for freezing-thawing cycles durability test. The amount of binder for soil stabilization is considered in a constant value of 5 wt.% of dry soil for UCS and freezing-thawing tests. The 90-day UCS value for OPC-based stabilized sample is 0.75 MPa, for As1-based stabilized sample is 2.63 MPa, for As2-based stabilized sample is 2.28 MPa, and for As3-based stabilized sample is 4.5 MPa. As seen, AAM-based stabilized soil samples show greater UCS value in the same binder/soil ratio and curing time. As3 showed the most effective activator with higher UCS value as a soil stabilizer. In the test of freezing-thawing, except As2-based stabilized sample, other samples survived all 12 cycles. As2-based soil stabilized sample only survived 7 cycles of freezing and thawing. The most amount of volume changes for OPC-based stabilized soil is 12.82% for 12 cycles, while this amount is 6.65% for As2-based stabilized soil for 7 cycles. As1- and As3-based stabilized soil have showed fairly stable volume changes; i.e. with the most amounts of volume changes of 5.93% and 4.17% for 12 cycles. This results show AAM-based stabilized samples are more soundness than OPC-based stabilized samples and are more stable during volume changes.