Experimental Study On The Dynamic Properties Of Lime-Treated Expansive Soil Affected By Wetting-Drying Cycles

For the effect of wetting-drying cycles lime-treated expansive soil strength characteristics were investigated. In this paper, after the lime treatment of Nanning weak expansive soil as the research object, through a series of indoor tests of physical and mechanical properties, obtained physical and mechanical properties of expansion soil before and after the lime treatment. Moreover, triaxial test specimens are used to carried on experiment of wetting-drying cycles. Finally, carry out static triaxial shear and dynamic triaxial test by GDS dynamic triaxial apparatus, the main research contents are as follows:1. A series of indoor physical and mechanical soil test are carried out on the ratio of blending 6% lime-treated expansive soil. The test results show that: lime-treated soil compared to the original expansive soil, the proportion decreased, liquid limit decreases, plastic limit increased, plasticity index was significantly decreased, maximum dry density decreases, the optimal moisture content increased, its soil category changed from low liquid limit clay into low liquid limit silt, high compressibility changed into low compressibility, free expansion rate, line shrinkage and swell shrink total rate index have decreased significantly compared with treatment before, inhibited the original expansive soil swelling shrinkage, the lime-treated soil is non expansive soil category, shear strength parameters has also been significantly improved.2. Carried out Wetting-drying cycles test on triaxial shear specimens, analysis the damage effect of wetting-drying cycles, it presents that wetting-drying cycles caused soil repeated expansion and contraction, leading to the development of fissures in the soil, reduce the degree of connection between soil particles, so that the treatment of soil structural damage and damage degree vary with the number of wetting-drying cycles increase and increase.3. Consolidated undrained triaxial test on treated specimens which subjected to 0-5 times wetting-drying cycles were carried out,the results show that:the effect of wetting drying cycles on the treatment of soil macro performance for shear strength of continuous attenuation, for the first time, after the second wetting-drying cycles cohesion attenuation range is bigger, after the third cycle attenuation amplitude decreased and stabilized, and friction angle only after the first wetting-drying cycles have larger attenuation, the overall change range is quite small.4. Through dynamic triaxial tests, obtain the treatment of soil dynamic deformation characteristics under the 0-5 times of wetting-drying cycles effect including the backbone curve (???d curve), dynamic elastic modulus and dynamic strain relationship curve (Ed??d curve, 1/Ed??d curve), damping ratio and dynamic strain curve (???d curve). Consolidation pressure, consolidation ratio, dynamic load frequency factors under wetting-drying cycles effect of soil treatment of backbone curve, dynamic elastic modulus and damping ratio are studied. Moreover, the backbone curve constitutive relation model, dynamic modulus of elasticity attenuation model under the influence of the different factors. According the equivalent damping ratio formula to calculate total strain range of damping ratio which is proposed by the equivalent linear model (Hardin-Drnevich model), meanwhile determine the maximum damping ratio ?max according to the test results. Furthermore, according to the hyperbolic dynamic stress dynamic strain proposed by Hardin-Drnevich model, fitting the calculated maximum dynamic modulus Edmax.