干湿循环作用下陕北Q_(2)黄土强度及水土特性试验研究

Experimental Study on Strength and Soil-Water Characteristics of Q_(2) Loess in Northern Shaanxi under Drying-Wetting Cycles

为研究不同干湿循环次数下陕北Q_(2)黄土水土特性及其强度的变化规律,利用真空饱和仪制备不同干湿循环次数的土样,采用直剪试验、滤纸法测定其非饱和抗剪强度参数及土水特征参数。研究表明:随着干湿循环次数的增加,陕北Q_(2)黄土的脱湿速率与进气值不断减小,持水能力逐渐增强,且脱湿速率与进气值降低速率逐渐减小,第二次脱湿时最大脱湿速率降幅约30%,进气值约降低1/3;剪应力-剪切位移曲线峰值更加明显,应变软化特性逐渐增强;得到土水特征参数、非饱和抗剪强度参数随干湿循环次数变化的预测拟合公式,且较为精确地预测了第4次干湿循环次数下土样的土水特征参数。

In order to study the variation law of soil-water characteristics and strength of Q_(2) loess in northern Shaanxi under different drying-wetting cycles,soil samples with different drying-wetting cycles were prepared by vacuum saturator,and the unsaturated shear strength parameters and soil-water characteristic parameters were measured by direct shear test and filter paper method.The results show that with the increase of drying-wetting cycle times,the dehumidification rate and air inlet value of Q_(2) loess in northern Shaanxi decrease,the water holding capacity increases,and the rate of dehumidification rate and air inlet value decrease gradually.During the second dehumidification,the maximum dehumidification rate decreases by about 30%and the air inlet value decreases by about 1/3.The peak value of shear stress shear displacement curve becomes more and more obvious,and the strain softening characteristic increases gradually.The prediction and fitting formulas of soil water characteristic parameters and unsaturated shear strength parameters with the number of drying-wetting cycles are obtained,and the soil water characteristic parameters of soil samples under the number of fourth drying-wetting cycles are accurately predicted.