Research On The Cumulative Damage To Expansive Soil In Wetting-Drying Cycle Condition

With the research object of expansive soil in Naming, Guangxi , combining on the observation date of expansive soil slope of field engineering ,the change law of the strength and deformation and damage to cumulative fatigue of manipulated expansive soil under wetting-drying cycle are disclosured by wetting-drying cycle test in laboratory. The main research findings are as follows:1. Triaxial test and wetting-drying cycle test are conducted by controlling the temperature and humidity, obtain the laws of the deformation change and strength attenuation that are changing with parameters of wetting-drying cycle are obtained.The cumulative damage of expansive soil is mostly occur in 1~5 the cycle index of wetting and drying. The subsequent strength arrives a stability gradually.Get the cycle index of wetting and drying of damage.Built up the relationship of the data of shearing strength vs the amplitudes and of wetting and drying cycle and the cycle index of wetting and drying.2. Based on the expansion test, the variable law of the deformation of expansive soil under wetting and drying cycle is discussed, the variable law of the deformation of expansive soil is unreversible. Increase with the cycle index of wetting and drying, the relative deformation is lessening gradually. increase in the residual deformation. Increase with the tangent modulus the absolute strain is lessening gradually. The detection infliction sequence of the circulate amplitude have no regulation. Attain a stability relative strain.3. Complete different circulate amplitude combine of the wetting-drying circulation experiment.Find high→low amplitude circulate, high circulation amplitude of the circulation number of times have decisive function to stabilize strength. But at same high and low circulation time several times, low→high amplitude circulation, the stable strength the former is high.4. Combine the tired accumulation of the Palmgren-Miner line damage standard, analyze to change circulate amplitude to descend the expansive soil strength accumulation damage,and discuss to make use of the accumulation damage theories to study the possibility that the inflation soil strength attenuation process.