| This paper is based on the National Natural Science Foundation of China project "Study on the effect of dry and wet cycles in Yunnan laterite dams"(Project No.51568031),which addresses the problems between water content,matrix suction and strength of unsaturated Yunnan laterite under the effect of dry and wet cycles.The water-bearing features and shear strength properties of dehumidified laterite and the relationship between them were investigated by combining model study and theoretical analysis through filter paper method test,pressure plate extractor test,and direct shear test.The following conclusions were obtained.The water-bearing features show that: when the water content of the filter paper test reaches a stable equilibrium,the mass water content and the contact filter paper water content of the dehumidified laterite show a slow decreasing trend with the decrease of the dehumidification moisture content;with the decrease of the mass water content,the contact filter paper water content shows a rapid decreasing-slow decreasing trend;with the increase of the initial dry density,the mass water content and the filter paper water content show a slow decreasing trend;with the increase of the initial water content,the mass water content shows a slow increasing-slow decreasing trend,and the contact filter paper water content shows a fluctuating decreasing trend.The characteristics of matrix suction show that:(1)when the water content of the filter paper method test reaches stable equilibrium,the matrix suction of the dehumidified laterite tends to increase with the decrease of the volumetric water content;with the increase of the initial dry density,the matrix suction and volumetric water content of the laterite generally show a fluctuating increasing trend;With the increase of initial water content,the matric suction and volumetric water content of laterite generally show a trend of fluctuating decrease.(2)In the pressure plate extractor test,when equilibrium was reached under each level of suction,the volumetric moisture content of laterite showed a trend of sharp decrease-stabilization with the increase of matrix suction,showing an inverted "J" curve shape;with the increase of initial dry density,the matrix suction and volumetric moisture content showed a non-linear increase and increasing trend respectively;with the increase of volumetric moisture content,the volumetric moisture content showed an increasing trend in general.The adaptability of soil-water model shows that: the three soil-water models Gardner,V-G and F-X were poorly fitted to the soil-water curves of the dehumidified laterite in the full suction range;the three soil-water models were better fitted in the high or low suction sections,respectively.The shear strength characteristics show that: under various influencing factors,the shear stress-shear displacement relationship of dehumidification laterite shows a rapid rise-a sharp declinestable strain softening phenomenon,showing brittle failure characteristics.With the increase of initial dry density,the peak stress increases,and the shear strength and strength index fluctuate.With the increase of initial water content,the peak stress decreases,the shear strength and cohesion decrease in fluctuation,and the internal friction angle increases in fluctuation.The relationship between soil-water characteristics and strength characteristics shows that: when the dehumidification laterite reaches the stable equilibrium of water content,the change trend of volumetric water content is consistent with that of dehumidification moisture content.Correspondingly,the relationship between volumetric water content and internal friction angle(cohesion)is also consistent with that between dehumidification moisture content and internal friction angle(cohesion).The cubic polynomial was used to fit the relationship between the shear strength index and the volume water content of the sample,and the fitting effect was good and reasonable.Based on the above fitting curve,the V-G model was used to predict the shear strength and shear strength parameters of the dehumidification laterite.The results show that the fitting curve is close to the test point in position and is in good agreement. |
