Study On Strength And Disintegration Characteristic Of Improved Granite Eluvial Soil

Nanyue district is located in the subtropical regions with abundant rainwater and remarkablely dry and wet altering climate conditions.In this area,the granite residual soil cover layer is relatively thick,with low Clay content,poor cohesiveness and containing a huge number of kaolinite which is hydrophilic and water-destructible under proper condition. It leads to that geological disasters such as landslides and collapse occur easily there. Therefore,it is necessary to improve granite residual soil to improve soil strength and water stability.Based on the granite residua soil low soil cohesive force, bad stability in water and high level of water-destructible characteristics, this paper puts forward three kinds of improved methods: fiber-improved methods, in which the mass fraction of fiber incorporation volume was 1 ‰, 2 ‰, 3 ‰, 4 ‰ and 5 ‰ with random mixing method; cement-improved methods,in which the mass fraction of cement incorporation volume was 2%, 3%, 4%, 5% and 6%, the sample was prepared with random mixing, then conserved for 7 days for testing;lime-improved methods, in which the mass fraction of lime incorporation volume was 4%,6 %, 8%, 10% and 12%, the sample was prepared with random mixing, then conserved for 7days for testing as well.This paper mainly studied the strength properties and disintegrating properties of the improved granite residual soil and compared with the unmodified ones, and then combined with the simulation analysis to find the best improvement methods. Wherein the strength characteristics was primarily studied through indoor static triaxial test, the confining pressure studied were 50 kPa, 100 kPa and 150 kPa respectively, controlling the shear rate, the improved degree of compaction studied were all 90% of the stress-strain characteristics of the sample to obtain its strength parameters cohesion and internal friction angle, and then got strength properties of the improved soil samples. Disintegration properties took into account the situations of suddenly encountering heavy rain after exposure, the soil disintegration was most likely to happen, so the actual situation was simulated, and the disintegration properties of improved soil sample was studied through dry and wet cycle disintegration test, the cycledisintegration was performed in accordance with 50 ℃ drying, weighing, disintegration,air-dried, then dried again, at the same time the phenomena was observed and the data was recorded as well, the disintegration rate of the sample was finally got after three dry and wet cycles and then the disintegration properties of improved soil was studied.The comparison between the soil samples improved by fiber, cement and lime and unimproved soil samples showed that the properties including Shear strength, cohesion,internal friction angle and resistance to disintegration of soil samples improved by lime were significantly better than unimproved soil samples and significantly better than the other two improvement methods as well. Through the stability analysis of the stability of the slope without support measures by Lizheng software: the sample improved by lime owned the maximum slope critical height. Therefore, the optimum improvement method of the granite residual soil was lime-improved method, and the best mass fraction of the lime incorporation volume was 6%. This conclusion was of great significance for practical engineering of similar soil.