冻融作用对坡面侵蚀过程的影响

Effects of Freezing-thawing on Hillslope Erosion Process

为了探究降雨条件下冻融作用对坡面土壤侵蚀的影响,利用室内人工模拟降雨试验研究了未冻融及冻融2种条件下,冻融前后土壤物理性质、产流、产沙和颗粒分选过程。结果表明:经过冻融作用后,土壤含水量增加了14.86%,土壤容重降低了4.13%,孔隙度增大了3.05%;相比于未冻融坡面,冻融坡面产流时间延迟了30.18%,产流后前4min内冻融坡面的产流率减小了16.69%,坡面入渗率表现为冻融坡面>未冻融坡面,冻融坡面稳渗率为未冻融坡面2倍;冻融坡面的侵蚀速率波动较剧烈,在产沙后前21min内,冻融坡面侵蚀的速率大于未冻融坡面,冻融坡面的泥沙流失量比未冻融坡面增加了4.67%;2种试验条件下坡面侵蚀过程中溅蚀颗粒、冲刷泥沙颗粒与土壤本底物颗粒的平均重量直径(MWD)相比,表现为溅蚀颗粒>本底物颗粒>冲刷泥沙颗粒。经t检验,2种试验条件下坡面侵蚀过程中溅蚀分别与本底物颗粒、冲刷泥沙颗粒MWD之间均表现为极显著性差异(p<0.01)。经ANOVA检验,冻融作用对坡面侵蚀过程中冲刷泥沙颗粒MWD表现为极显著性影响(p<0.01)。

In order to explore the effect of freezing-thawing（FT）on the hillslope soil erosion under rainfall conditions, a simulated rainfall experiment was carried out to study soil physical properties, runoff yield, sediment yield and particle size-selection before and after FT. The results showed that after FT, soil moisture content, bulk density and porosity increased by 14.86%, 4.13% and 3.05 %, respectively. The runoff-yielding time of FT hillslope delayed by 30.18%, compared to that of slope with no FT, and runoff rate of FT hillslope was 16.69% lower than that of no FT slope within first 4 minutes after runoff yielding. The infiltration rate of FT slope was greater than that of no FT hillslope and the stable infiltration rate of FT slope was as twice as that of no FT hillslope. Meanwhile, the erosion rate of FT hillslope significantly fluctuated, which was greater than that of no FT hillslope within first 21 rain after sediment yielding, while the sediment yield of FT slope was 4.67%o higher than that of no FT hillslope. By comparison, it was found out that the MWDs of 3 types of particles in the slope erosion process under 2 experimental conditions were arranged by the following sequences： splashing particles〉 substrate particles〉 scouring particles. T-test analysis showed that there were remarkable differences between MWD of splashing particles and substrate particles or scouring particles under 2 experimental conditions（p〈0.01）. The ANOVA results revealed that the freezing-thawing had a significant influence on the MWD of scouring particles in hillslope erosion process（p〈0.01）.