中文摘要：

根据渗水实验、孔隙度、粒度、磁化率测定，研究了长武黄土剖面L3～S6土层的渗透性及其成因。研究结果表明，L3，L4，L5和L6黄土层渗透性较强，稳定入渗速率较高，它们的渗透系数变化在0．57～1．06mm／分之间，4层平均为0．75mm／分；S3，S4，S5和S6古土壤渗透性较弱，稳定入渗率较低，它们的渗透系数变化在0．18—0．71mm／分之间，4层平均为0．44mm／分。红色古土壤达到稳定入渗率的时间一般比黄土层要长；黄土层的平均空隙度比红褐色古土壤高，渗透性强，粒度成分较粗，黄土层比红褐色古土壤层更利于构成含水层；红褐色古土壤层粒度成分细，空隙度低，渗透性弱，比黄土层利于形成隔水层。长武第4层古土壤厚度小，纵向裂隙发育强，入渗速率较大，不易形成隔水层。磁化率、粘粒含量资料表明红褐色占土壤层与黄土层渗透性、含水空间和隔水性的差异主要是当时气候冷干和温湿交替变化的结果。

英文摘要：

Based on water-seeping experiment,porosity, grain size analysis and magnetic susceptibility determination, the permeability from L3 to S6 in the loess section in Changwu of Shaanxi was studied. The results show that the waterseeping speeds of L3, L4 , L5, L6 loess layers are higher than those of adjacent red paleosol layers. The seeping speed in the initial 20 minutes of the experiment is the highest,about 2mm/min. It becomes lower from 20 to 80 minutes and is stabilized from 80 to 100 minutes. The stabilized speeds of L3 ,L4 ,L5 ,L6 loess layers are 0. 64mm/min,0. 57 mm/min, 1.06mm/min,0.71 mm/min respectively, and the average is 0.75mm/min. The stabilized speeds of S3 , S4 , S5 and S6 paleosol layers are lower, 0. 18 mm/min, 0.71 mm/min, 0.53 mm/min, 0.35 mm/min respectively, and the average is 0. 44 mm/min. The time for seeping speed of paleosol layer becoming stable is longer than that of loess layer,and as the result of the longitudinal crack in red-brown paleosol layers developing better than that in loess layers,the seeping speed of S5 becomes stabilized after 230 minutes. The water-bearing space of loess layer is larger than that of red-brown paleosol layer, and the grain size is bigger too, so the water-bearing space forms more easily in loess layer than in red-brown paleosol layer. In paleosol, the grain size is smaller, the porosity is lower, and the permeability is weaker,thus the water-resistant layer forms more easily in paleosol layer than in the loess layer. Because the porosity of paleosol layer is higher, the water-resistant capability of paleosol layer is weaker. The 4th paleosol layer in Changwu is thin, the longitudinal crack in it develops well,and the seeping speed is higher,which reduce its water-resistant capability. The analyses of magnetic susceptibility and grain size content show that the strongly water-resistant red-brown paleosol is determined by warm-moist climate at that time,and the weakly waterresistant loess is determined by the cold-arid climate at that time.