Study On The Strength Of Unsatureted Soils Condering Hysteretic Of Soil Water Characteristic Curve

Most of unsaturated soil distributed in nature, currently the TheoreticalFramework of unsaturated soil is builded based on the soil water characteristic curve.The use of unsaturated soil water characteristic curves for predicting the shearstrength of unsaturated soils is an important aspect. However,we found there ishysteresis effects in the soil water characteristic curve which including dring curveand wetting curve, a large number of engineering practice show that the slope failureoften experienced many times hydraulic circulating.for example, slope will failureduring rising and falling of the water level in the reservoir area. Therefore, syudyshear strength of unsaturated soils under the effect of hysteresis has importantsignificance. Meanwhile, put forward a shear strength prediction formula not includedparameter matric suction for the development of the theory of unsaturated soil hasimportant application value.First of all,development soil water characteristic curve tester, which includes apressure chamber, the pressure control panel, drainage measurement device and gassourse. The core part is drainage measurement device, overcome the currentlaboratory soil water characteristic curve tester can not overcome the impact of thewater pressure. At the same time, reference Marriotte bottle test principle,development water inlet device when testing the wetting curve. During the test toprovide a stable flow, accurate measurement water absorption of sample in theprocess of wetting process, greatly improve the test accuracy. On this basis, usingnew soil water characteristic curve to test hysteresis curve. And using experimentaldata Van Genuchten parameter fitting equation to obtain better results.Secondly,using the direct shear testing equipment of unsaturated soil onZhangjiakou remodeling silt doing direct shear tests of desorption process and theadsorption process control matric suction of50kPa,100kPa and150kPa.Study therelationship between the normal stress shear strength and vertical in the desorptionprocess and the absorption process, and the change trend of cohesion and internal friction angle, that is the greater the vertical normal stress shear strength the greatercohesion increases larger,but little change in angle of internal friction is negligible.Meanwhile, discover the shear strength increase with the increase matric suctiongradually increased in the desorption process and the absorption process. At the samematric suction, the shear strength of the desorption process is greater than the shearstrength of the absorption process.Finally, according to the hysteresis curve fitting equation model, establishingformula considering the hysteresis effect and no matric suction parameter to predictunsaturated soil shear strength and use this formula to verify the test data, achievinggood results. The formula can provide a reference for Zhangjiakou unsaturated soilstrength calculations.