土壤失水过程对土体收缩特性的影响

Effects of Soil Drying Process on Soil Shrinkage Characteristic

为探求不同质地和容重土壤失水过程中的土体收缩特性,选取山东壤土(SD)和陕西粉粘壤土(SX)作为供试土壤,并分别设定初始容重为1.30、1.40、1.50 g/cm^3,采用离心机法测定土壤水分特征曲线,同时对土壤脱水过程中土体轴向和径向收缩特征进行研究。结果表明,对于SD和SX土样,不同容重土壤含水率随吸力增加呈现不同幅度的减小趋势,但其减小速率均表现出"慢-快-慢"的变化特点;在土壤脱水过程中,土体线缩率随含水率减小而增大,Logistic模型可以较好地拟合线缩率与含水率之间的非线性关系(R^2在0.96~0.99之间);土壤轴向(δ_s)、径向(δ_r)和体积收缩应变(δ_V)均随容重增加而减小,SD和SX土样分别以水平收缩形变和垂直收缩形变为主。相关性分析表明,δ_s、δ_r和δ_V与砂粒含量呈负相关关系,与粉粒和粘粒含量呈正相关关系,且3种收缩特征指标与土壤颗粒含量之间的相关性受容重影响;对于SD土样,δ_s和δ_r与粘粒和粉粒含量显著相关,δ_V与砂粒含量显著相关;对于SX土样,δ_s、δ_r和δ_V与砂粒和粉粒含量显著或极显著相关,而与粘粒含量无显著相关性。

To explore soil shrinkage characteristics during soil drying process,loam soil from Shandong Province（ SD） and silty clay loam soil from Shaanxi Province（ SX） were selected. The initial bulk density of the two different types of soil was set at 1. 30,1. 40 and 1. 50 g/cm^3. A centrifuge method was adopted for soil-water characteristic curve measurement,and the axial and radial shrinkages during drying process were measured and quantitatively analyzed. Results showed that firstly,as for SD and SX soils,soil moisture was decreased with the increase of suction,but the decreasing range was different due to different bulk densities. When suction was increased from 0 to 7 000 cm,soil moisture was decreased with different rates. Secondly,linear shrinkage ratio increased with decrease of soil moisture during drying process,and the non-linear relationship between linear shrinkage ratio and soil moisture could be well fitted by the Logistic model,with high determination coefficients（ R^2） ranged from 0. 96 to 0. 99.Thirdly,axial shrinkage strain（ δ_s）,radial shrinkage strain（ δ_r） and volume shrinkage strain（ δ_V） all decreased with the increase of soil bulk density. And further analyses indicated that the mainly shrinkage characteristics for SD and SX soils were horizontal shrinkage and vertical shrinkage, respectively.Meanwhile,correlation analyses showed that δ_s,δ_rand δ_Vwere all negatively correlated with sand content and positively correlated with silt and clay contents. And the correlation between the three types of shrinkage strains（ i. e.,δ_s,δ_rand δ_V） and soil particle content was obviously influenced by bulkdensity. Detailedly,as for SD soil,δ_sand δ_rwere significantly correlated with clay and silt contents,however,δ_Vwas significantly correlated with sand content; as for SX soil,δ_s,δ_rand δ_Vwere all significantly or highly significantly correlated with sand and silt contents,but there was no significant correlation with clay content.