Experimental Study Of The Moisture Content And Clay Content On The Strength Of Unsaturated Soil

Unsaturated soil is three-phase medium, so the mechanical properties of vapor, liquidand solid phase and energy balance is much more complicated than the saturated soils. Themacroscopic parameter matric suction and suction stress are widely involved in the researchof unsaturated soils shear strength. The paper researches the regular pattern of matric suctionand effective cohesion which will make great significance for engineering practice. On thebasis of the previous tests results scholars presented, choosing the unconsolidated red-claysoils as the research object, this paper analyses the effect on shear strength that resulted frommatric suction, suction stress, moisture content. In the study, we did the soil watercharacteristic curve tests for unsaturated soil and the direct shear tests by applying the soilpore pressure dewatering and controlling clay content to make the soils samples underdifferent moistures and different gradations. From experimental research can found that shearstrength of unsaturated soil depended largely on the degree that soil matric suction changedinto the effective cohesion c’, or the conversion rate that the matric suction transformed intosuction stress. There must be a certain moisture content that makes the soil shear strength amaximum regarding that the matric suction and moisture content was in keeping with the soilwater characteristic curve. In addition, clay content and gradation of grain has an enormousimpact on the transformed rate. When the clay content was more than70%, the conversionrate of the average particle size was up to80%and even more. However, the transformed ratesharply decreased, eventually was close to zero with the growing coarse granule. And at thesame time shear strength of unsaturated soil is very low while there was some matric suction.So it should be paid enough attention to in results analysis.According to test data analysis put forward the three parameters of the relationshipbetween moisture content and conversion function, in the process of this method to calculatethe moisture migration effectively, the change of the cohesive force of the cohesion ofdifferent clay with moisture content change curve, and through the test analysis in differentmoisture migration path to the strength formula is worth, put forward the theoreticalcalculated value and actual worth correction coefficient.