非饱和砂质黏性紫色土一维渗透特性试验研究

利用土体瞬时渗透特性测试仪,对重庆非饱和砂质黏性紫色土进行一维土柱垂直渗透试验。模拟不同降雨条件(5 mm/h、15 mm/h、30 mm/h)下,其入渗率、累积入渗量、浸润峰、体积含水率和吸力等随时间的变化规律;分析得到其渗透特性和持水特性。结果表明:(1)在初始含水率相同的情况下,降雨强度越大,初期入渗率越大;土体的入渗率与含水率有关,含水率越低的土体,其入渗率越大;(2)不同降雨强度下,水入渗到同一监测点的时间不同;且降雨强度越大时,含水率增大到某一稳定值的数值也越大;(3)降雨强度并不会影响土体的饱和渗透系数和持水性能。从试验规律可知非饱和砂质黏性紫色土的体积含水率θ与渗透系数的对数lgk之间存在线性关系,拟合的线性方程,可应用于相应紫色土地区土体的非饱和渗流分析。

Experimental Study on One-dimensional Permeability of Sandy Clayey Purple Soil at Unsaturated Condition

One-dimensional vertical permeability test for sandy clayey purple soil column in Chongqing was carried out by using the instantaneous permeability tester.Under different rainfall conditions (5 mm/h,15 mm/h and 30 mm/h),the infiltration rate,cumulative infiltration amount,infiltration peak,volume moisture content and suction change with time were simulated,and the permeability and water holding characteristics were analyzed.The results show:(1) with the same initial water content,the higher the rainfall intensity is,the greater the initial infiltration rate is;the infiltration rate of soil is related to the water content,and the lower the water content is,the greater the infiltration rate is;(2) under different rainfall intensity,the time of water infiltration to the same monitoring point is different;and the larger the rainfall intensity is,the greater the value of water content increasing to a certain stable value is;(3) rainfall intensity does not affect the saturated permeability coefficient and water holding capacity of soil.It can be seen from the test law that there is a linear relationship between the volume moisture content θ of the unsaturated sandy clayey purple soil and the logarithm lgk of the permeability coefficient.The fitted linear equations can provide scientific basis for unsaturated seepage analysis in the purple soil area.