Study On Chemical Curing Mechanism And Durability Of High-liquid Limit Soil Subgrade In Fujian

High-liquid limit soil is widely distributed in China,A large number of high liquid limit soil directly used for roadbed filling,leads to the non-uniform deformation,slope collapse,mud and other diseases in the road.Although the realization of high-liquid limit soil is turning waste into treasure because of many improved measures,but due to the high temperature,rainy weather,regional soil and other reasons in Fujian Province,the improvement effect of high-liquid limit soil in Fujian province is still not perfect,The curing mechanism and durability are not clear enough.Based on this,In this paper,through literature research and material characteristics analysis,using CS(Cement+SAP),QLS(Quicklime+SAP),CL(Cement+Renolith),CY(Cement+YiFusen),EN-1(Cement+EN-1)five composite modified treatment scheme of high liquid limit soil,through the physical and mechanical properties test,Durability test,microscopic test,theoretical calculation and numerical simulation were used to study the mechanism and durability of chemical solidification of high liquid limit soil subgrade in Fujian province:1.Based on the investigation,the distribution of high liquid limit soil and water content,liquid limit and CBR in Fujian Province were obtained;Most of the soil does not meet the requirements of subgrade filling,which needs to be improved;Based on the test results of physical and mechanical properties of three typical high liquid limit soils in Fujian Province,select the appropriate improved soil.2.Combined with the dry-wet cyclic compressive strength,Wet,Immersion,wet and dry cracking test,the durability of five kinds of improved soil is analyzed,the optimal ratio of five kinds of combination scheme are as follows:5%Cement+0.06%SAP,6%Quicklime+0.06%SAP,3%Cement+0.2%Renolith,3%Cement+0.004%Yi Fusen,3%Cement+0.008%EN-1,the effects are as follows:CS,CY,CL,CE,QLS and the strength and durability of the composite reinforced soil were better than that of single solidified soil,they can meet the requirements of subgrade filling.3.Microscopic test found:SAP is a high molecular polymer,which has a strong water absorption effect.Both Renolith and Yi Fusen are organic compounds,which have a certain degree of bond polymerization.EN-1 is an ionic compound,it can occur Ion exchange reaction.Four materials are heated to a temperature of 100℃,the mass loss is less than 20%,which shows that the thermal stability of the four materials is very good.The curing agent changes the physical and mechanical properties of the soil by changing the pore structure,the phase structure and the bonding way between the soil particles,so as to meet the requirements of the roadbed filling.4.The results of comprehensive theoretical calculation and numerical simulation show that,the difference between the theoretical value and the numerical simulation results of five modified subgrade settlement is less than 3 cm,compared to plain soil subgrade settlement decreases 11～15cm,and the stability safety factor of the five modified soil subgrades is more than 2.5 times of the plain soil.5.Based on the investigation and analysis,and summarizes the construction technology,quality control and quality inspection index suitable for the high liquid limit subgrades in Fujian Province.Through the economic analysis of the improved program,the improvement effects of the five schemes is as follows:CY,CE,CL,QLS,CS.In all aspects,the five modified soil can meet the requirements of subgrade filling,but the improvement effect of CY and CL is relatively better.