基于含水量高频监测的花岗岩崩岗侵蚀红壤优先流研究

Study on the Preferential Flow of Red Soil Erosion in Granite slope collapse with High Frequency Monitoring of Water Content

为了研究崩岗侵蚀土壤的水分运动特征,采集湖北通城县花岗岩崩岗区的红壤,研究优先流及影响因子。把采集的1种红土和3种砂土按照野外＂上红下砂＂层次顺序,分别装填到长60cm,宽11cm,高110cm的透明PVC土箱。3个土箱在不同初始含水量（12.2%~23.6%）和雨强（0.7,1.2mm/min）下进行模拟降雨入渗,用时域反射仪（TDR）高频监测土体20个部位含水量瞬时动态,根据含水量的时空变化识别土体优先流发生特征。结果表明,降水入渗多表现为非均匀入渗,土壤饱和导水率较大、大孔隙路径状况较好的土体更容易发生优先流,其影响范围更广。雨强越大,优先流与周围基质作用越明显,优先流反应量越大,雨强1.2mm/min的优先流速率是0.7mm/min的1.8~4.0倍。且小雨强的优先流程度受土箱初始含水量影响大于大雨强处理,在雨强1.2mm/min时,优先流程度随初始含水量的增加而减小;当雨强减小为0.7mm/min时,优先流程度随初始含水量的增加先增大后减小。优先流发生受降水特性和初始含水量影响,但土壤性质对优先流的影响更大。

In order to study the soil water movement characteristics of the slope collapse erosion,the author collected red soil from granitearea of collapse gully erosion in Hubei Tongcheng County and studied the preferential flow and impact factor.The collection of 1kind of clay and 3kinds of sand layer were loaded in transparent PVC soil box,60 cm long,11 cm wide,and 110 cm high,respectively,in accordance with the order of＂sand under the red soil＂.Rainfall infiltration was simulated using three soil boxes in different initial moisture content（12.2% ~23.6%）and rainfall（0.7,1.2 mm/min）,and the instantaneous dynamic soil moisture of 20 positions of the soil mass was monitored by the time domain reflectometry（TDR）in high frequency.Thus,according to the spatio-temporal variations of the water content,the soil preferential flow characteristics were recognized.The results showed that the infiltration of precipitation was not uniform infiltration,and when the soil saturated hydraulic conductivity was larger and the path condition of marcropore was better,the preferential flow was more likely to occur,and its scope of influence was more extensive.The greater the rainfall intensity,the more obvious effect the preferential flow and the surrounding matrix,the greater the preferential flow rate.The rainfall intensity of 1.2mm/min had a preferential flow rate 1.8~4.0times of that by the rainfall intensity of with 0.7mm/min.When the treatment of initial moisture content was smaller,the initial flow time was later and the flow rate was smaller.The results showed that the preferential flow was affected by precipitation and initial water content,but the effect of soil properties was greater.