The Dynamic Parameter Experiment Research On Fly Ash Of Freezing And Thawing Circulation

This text is at the background of freezing and thawing destruction to the roads in cold region. Through a great deal of materials reading and on the base of research on fly ash and silty clay of the predecessors, we utilize dynamic type triaxial test to do the research on fly ash and silty clay. The elastic modulus Ed and shear strength of soil (бd/2) are adopted as the main parameter of dynamic force when collapse period Nf is equal to 10.After the complete freezing and thawing circulatory processes of cohesive soil samples experience 0 to 8 indoors, we carry on the triaxial test under the different rock pressure and determine the elastic modulus Ed and shear strength (бd/2). According to the data of the elastic modulus Ed and shear strength (бd/2), we can study the effect of freezing and thawing circulation on the character of silty clay and fly ash under different seconds of freezing and thawing circulation.The concrete contents of the research include work as follows:1.The present condition of dynamic force parameter research is concluded after the freezing and hawing circulation of silty clay and fly ash at home and abroad.2.Make sure the physical parameter of the silty clay and fly ash, as well as the parameter of the freezing and thawing test.3.Study the methods of dynamic load test on the silty clay and fly ash.The test studies the effect of freezing and thawing circulation on the parameter of dynamic force of silty clay and fly ash.The main contents of geotechnological experiments include:1.Materials and preparation: some samples which are made indoors at the optimum water content after taking outdoors. The kit instruments include compaction device, dry-box, electronic scale and so on.2. Carry on the test on samples by the use of freezing and thawing box and regulate the temperature according to the actual condition. The temperature gradient must be regulated±1℃once every 24hours,and the temperature should range from -5℃to 5℃.3. Utilize dynamic type triaxial test to make sure the shear strength and elastic modulus of silty clay and fly ash, which don't experience the freezing and thawing circulation.4. The dynamic type triaxial test of silty clay and fly ash undergoes eight freezing and hawing circulations in total. By the strength contrast from beginning to end, we can do a quantitative analysis on dynamic strength of silty clay and fly ash every time.From the result of the experiment, we can know that silty clay is more stable after experiencing freezing and thawing circulation three times, but dynamic strength will be lower than 52% to 75% of unfrozen silty clay. So anti-freezing property of silty clay is weaker when it's used as subgrade fillers.Further more, under the condition of 300kPa confining pressure, the dynamic strength of silty clay is better than that of other two different confining pressure at first, but as vibration numbers of circulatory load increase, the dynamic strength will decline. According to the comparison of eight freezing and thawing circulation, fly ash is as same as silty clay under the condition of 100kPa at the first time. And under the condition of 200kPa,the dynamic strength of fly ash, which is frozen and thawed, is 40% more than that kind of silty clay. The dynamic strength of fly ash is 60% more than that of silty clay under the condition of 300kPa.So the anti-freezing durability of fly ash is better than that of silty clay .Through three times of freezing and thawing circulation, the stress of fly ash tends to be stable, and it will enhance while the confining pressure improves.At the same time, the dynamic strength decreases while the vibration frequency of circulation load increases. Under the condition of 300kpa, the dynamic strength of fly ash is better than that of another two kinds. At this moment, its stability is the best of all, and with the increasing of vibration frequency of circulatory load; its dynamic strength is still higher than others. After one freezing and thawing circulation, the dynamic modulus of fly ash decreases at first. But after the second time, it increases at first and then decreases later. Its dynamic modulus tends to be stable with the change of strain after 3 to 8 freezing and thawing circulation. But the dynamic modulus of fly ash is 28.6% higher than that of silty clay. For this reason, we can put specific quantity of fly ash into subgrade fillers to enhance the durability of anti-frozen and thawed. We can know the dynamic modulus of fly ash will be improved after three freezing and thawing circulation. The reason is that the porosity ratio of dense soil becomes smaller, the structure becomes dense and the confining pressure becomes larger after the action freezing and thawing circulatory load. It's also one of the reasons that fly ash is better than silty clay as the subgrade fillers.The research indicates that the dynamic performance criteria of fly ash will be better than that of silt after three freezing and thawing circulation. Meanwhile, the fly ash has better anti-frozen property and stability. When the times of freezing and thawing circulation is increasing, the attenuation and loss rate of dynamic strength of silty clay is higher than that of fly ash .So it shows that the fly ash completely can be used as subgrade fillers in seasonal frost regions. Furthermore, it also can save the earth and reduce the environment pollution, and acquire greater social and economical benefits.