基于不同坡比的黄土边坡大雨降雨入渗测试与比较

Testing and comparison of heavy rainfall infiltration of loess slope at different slope ratios

降雨是诱发黄土边坡失稳破坏的重要因素,加之黄土边坡形态各有其独特性,因此研究不同坡比条件下黄土边坡降雨入渗规律和机理是必要的。本文以甘肃某均质黄土边坡为原型,开展了3种坡比(坡比1∶1、1∶0.75、1∶0.5)条件下的大雨降雨边坡模型试验,测试了边坡土体含水率、基质吸力和湿润锋的变化,分析了不同坡比条件下降雨入渗过程和坡面冲刷现象,评价了不同坡比条件下降雨入渗规律的差异。试验结果表明:在边坡降雨入渗过程中,坡顶降雨入渗速率最快、坡脚较快、坡中最慢,且降雨入渗深度呈现出坡脚最深、坡顶较深、坡中最浅的特点;同时不同坡比条件下黄土边坡降雨入渗规律差异较大,以坡比1∶1边坡的体积含水率峰值作为参照条件,坡比1∶0.75、1∶0.5边坡在坡脚处含水率峰值分别增大7.3%、12.7%,坡中处含水率峰值分别减小0.8%、5.8%,且坡比越大的边坡,坡脚处含水率曲线越陡,坡中处含水率曲线越缓,表明随着坡比的增大,坡中降雨入渗速率越慢,坡脚入渗速率越快,且以坡比1∶1边坡坡中湿润锋深度作为参照条件下,坡比1∶0.75湿润锋深度减小5~10 cm,坡比1∶0.5湿润锋深度减小10~15 cm,说明坡比越大,坡中降雨入渗深度越浅;同时以坡比1∶1边坡坡面产流作为参照条件下,坡比1∶0.75、1∶0.5边坡的坡面产流分别增大11.1%、27.7%,表明随着坡比的增大,坡面径流现象越明显,冲刷作用越剧烈,坡脚淤泥层越厚。最后基于Geo-studio软件验证了模型试验结果的正确性。

Rainfall is an important factor inducing the instability and failure of loess slope.In addition,the shape of loess slope has its own uniqueness.Therefore,it is necessary to study the law and mechanism for rainfall infiltration of loess slope at different slope ratios.In this paper,heavy rain rainfall slope model tests were carried out at three slope ratios(slope ratio 1∶1,1∶0.75 and 1∶0.5)based on a homogeneous loess slope in Gansu Province,with the changes of soil moisture content,matric suction and wetting front of the slope tested.Then,the rainfall infiltration process and slope scour phenomena at different slope ratios were analyzed,with the differences of infiltration laws evaluated.The results show that the rainfall infiltration rate is the fastest at the top,the faster at the foot and the slowest in the slope,and that the depth of rainfall infiltration is the deepest,the second at the top and the shallowest in the slope.At the same time,the rainfall infiltration laws of loess slope are greatly different at different slope ratios.Taking the peak volume moisture content of a slope with a slope ratio of 1∶1 as a reference condition,the peak value of the water content at the foot of the slope at a slope ratio of 1∶0.75 and 1∶0.5 increased by 7.3% and 12.7% respectively,and the peak value of the water content in the slope decreased by 0.8% and 5.8% respectively.In addition,the steeper the moisture content curves at the foot of a slope,the slower the moisture content curves in the slope with a larger slope ratio,indicating that with the increase of slope ratio,the slower the rainfall infiltration rate in the slope,the faster the infiltration rate at the foot of the slope.Taking the wetting front depth in a slope at a slope ratio of 1∶1 as a reference condition,the wetting front depth at a slope ratio of 1∶0.75 was reduced by 5~10 cm,and the wetting front depth in a slope ratio of 1∶0.5 was reduced by 10~15 cm.It shows that the higher the slope ratio is,the shallower the rainfall infiltration depth is.At the same time,under the reference condition of slope surface yield flow at the slope ratio 1∶1,the slope surface yield flow at the slope ratio 1∶0.75 and 1∶0.5 increases by 11.1%and 27.7%respectively.It shows that with the increase of slope ratio,the runoff on the slope surface is more obvious,and the slope scour becomes more serious and the silt layer of the slope foot is thicker.Finally,it verified the correctness of model test results based on the Geo-studio software.