Study Of Fly Ash In Filling Into Base Of Highway In Cold Area

This paper relies on the project of"Study of filling materials of roadbed and construction technique"belonged to Transportation institute of Jilin province.It has mainly studied highway roadbed filling with fly ash in cold area. The paper consists of five chapters. Chapter four is the emphasis of the paper,chapter three is the core of the paper.Chapter one introduces study background,purpose and significance. Fly ash is a kind of industrial waste generated in power station. It has quite a lot of characteristics which is apt to be applied in highway construction. As a new kind of road material, it has wide applying foreground. It demands scope of moisture capacity much wider than soil which is apt to control moisture capacity in construction and accelarate the progress of works. In the meanwhile, fly ash pollute environment seriously and take up lots of land . In order to reduce fly ash pollution and save land, comprehesive utlization of fly ash has become a very important current task.Chapter two introduces the road performance of fly ash. Through the compaction curve of fly ash, we can find that the maximum dry unit weight and optimum water content of fly ash from different factories vary, mainly because of different particle size and grain composition. In construction , new compaction experiment should be conducted if the quality of fly ash has changed, in order to indentify the maximum dry unit weight of fly ash and to ensure the degree of compaction of the roadbed. Fly ash is more sensible to compaction coefficient than soil.And also,fly ash may be influenced by compaction coefficient more obviously than soil. With the increase of degree of compaction, the strength of fly ash increases rapidly. Therefore, degree of compaction must be controlled when filling roadbed with fly ash.Chapter three is the core of this paper. It studies the frost–heave performance of fly ash,combination of fly ash & soil and soil. Through experiments, we discovered that it is visual to judge frost-heave ratio by degree of saturation. There is obvious correlation between frost-heave ratio and degree of saturation of fly ash. Based on arrangement and analysis of experiment data, we put forward the formula only for reference. Because of the cycles of freezing and thawing action , the degree of compaction decreases by year , correspondingly, the moisture capacity in the roadbed increases by year.Therefore, the bearing capacity of the roadbed will decrease. During the cycles of freezing and thawing, in the conditon of feed-water makeup, the strength of roadbed reduces largely. The sequence of strength reduction of the three kinds of materials mentioned above is : soil>fly ash >combination of fly ash & soil. The combination is better than fly ash. That is ,the freeze-thaw resistance of the combinatin is better than fly ash or soil. The latter two is near to each other. In the conditon of no feed-water makeup, the freeze-thaw resistance of fly ash and the combination is superior to soil. The frost depth of fly ash is much smaller than soil. The heat conduction coefficent of fly ash is smaller than soil. As for the freeze-thaw resistance, fly ash is superior to soil.Chapter four talks about the design and construction of fly ash experimental road. The purpose of roadbed design is to comprehensivelyconsider traffic composition, traffic load, practical performance of filling materials, geologic enviroment and natrural enviroment etc.factor, to adopt economic and effective solution, to select reasonable roadbed structure and compaction standard, to ensure the fly ash roadbed has adequent strength and stability to provide solid base for pavement. It also introduces the detection and standard for degree of compaction. Degree of compaction is the main control data in the detection of filling roadbed, is the most economic and effective technical method to ensure strength and stability of the roadbed. During the design of road stucture thickness,we adopt compressive rebound modulus as a strength parameter to calculate for measureing the rebound modulus of fly ash filling material. So the measurement of road rebound modulus is a important parameter in design of road structure.Chapter five is the summarization of the paper. It is the summarization of the completed jobs during the course of writing this paper, it also presents the content and direction for further study.