Improvement Of Silt In Yellow River Flooding Area And Interfacial Friction Of Soil

Eastern Henan is located in the Yellow River flooding area,the treatment of silt subgrade is an urgent engineering problem in the construction of this area.Because the traditional soil modifier has a certain impact on the environment,the exploration of new soil modifier will play a certain role in the treatment of silt subgrade.Because of its high tensile strength and good corrosion resistance,FRP(fiber reinforced polymer)has been gradually applied in the fields of superstructure and pile foundation reinforcement.However,the study on the interfacial friction between FRP material and soil has not been carried out yet.In this paper,calcium lignosulfonate is used to modify silt in the Yellow River flooding area of Eastern Henan Province,which provides a basis for the application and popularization of this technology in this area.The interfacial friction characteristics between GFRP cloth and soil were studied through indoor friction test,which provide appropriate parameters for the application of this material in engineering.The main contents of this paper are as follows:(1)The dynamic characteristics of silt and lignin-modified soil in the Yellow River flooding area were studied by dynamic triaxial test.The effects of compaction and confining pressure on the dynamic strength of silt,and the effects of different calcium lignosulfonate content and curing age on the dynamic strength and dynamic shear modulus of the modified soil were studied.The results show that calcium lignosulfonate is helpful to improve the dynamic properties of silt in eastern Henan,and when the lignin content is about 5%,the improvement effect is the best.(2)The strength of the lignin-modified soil was studied by compaction test and unconfined compressive strength test,and the effects of different lignin content and curing age on the strength of improved soil were analyzed.The results show that the maximum dry density of lignin-modified soil increases first and then decreases with the increase of calcium lignosulfonate content,and the optimal moisture content decreases gradually.The strength of the lignin-modified soil increases first and then decreases with the increase of the dosage,and increases gradually with the increase of the curing age.The strength increases obviously with the calcium lignosulfonate content of about 5% and the long curing age.(3)The freeze-thaw cycling tests of lignin-modified soil specimens with different calcium lignosulfonate content were carried out by using concrete rapid freeze-thaw cycling tester.The effects of calcium lignosulfonate content and freeze-thaw cycles on the durability of lignin-modified soil were analyzed.The test results show that the strength of silt and lignin-modified soil decreases gradually with the increase of freeze-thaw cycles;under the same freeze-thaw cycles,the strength of lignin-modified soil is slightly lower than that of silt,which indicates that appropriate calcium lignosulfonate content can effectively improve the durability of soil.(4)The interfacial friction characteristics of silt-GFRP cloth were studied by TZY-1 geosynthetics comprehensive tester.The effects of moisture content,compactness and normal stress on the interfacial friction coefficient were analyzed.The results show that the interfacial friction coefficient increases with the increase of compactness and decreases with the increase of normal stress.When the moisture content of soil is near the optimum moisture content,the interfacial friction coefficient reaches the maximum and decreases when it exceeds the optimum moisture content.