降雨型大孔隙斜坡非平衡流与失稳特性试验研究

Experimental Study on Non-equilibrium Flow and Instability Characteristics on Macropores Slope under Rainfall Conditions

为揭示降雨条件下含大孔隙斜坡水分非平衡运移与失稳特性,设计了室内2阶边坡模型,在坡体内布设30个人造大孔隙,分别施加2种降雨强度R=30、80 mm/h,测试坡顶、坡中、坡脚处的体积含水率θ、孔隙水压力p、土压力σ、位移u、坡面流速v、坡面累计径流量q等指标,应用PhotoInfor图像处理技术识别位移云图,分析了大孔隙斜坡的水力响应规律和失稳破坏过程。结果表明:降雨强度越大,坡脚、坡中、坡顶处θ开始响应的时间越接近,非平衡流现象越显著,坡脚处越易积水,坡顶处越易形成冲蚀沟,坡脚p二次增大、坡顶卸压时间提前;坡顶、坡脚σ随着降雨强度的增大而增大,达到峰值后缓慢减小,最终随着边坡局部垮塌而释放;u随着降雨历时的增长而缓慢增大,当边坡发生局部垮塌时达到峰值;降雨强度越大,坡顶、台阶处的u峰值越大,达到峰值的时间越早;q和v的峰值均随降雨强度的增大而增大;降雨强度较小时,大孔隙边坡主要发生浅层局部滑裂破坏,降雨强度较大时,大孔隙边坡主要发生浅层局部冲刷破坏。

In order to reveal non-equilibrium migration and characteristics of instability of macropores slopes under rainfall conditions, an indoor two-stage slope model with 30 artificial macropores was designed. Two rain intensities 30 and 80 mm/h were applied respectively. Volumetric moisture content θ, pore water pressure p, soil pressure σ, displacement u, slope surface velocity v and cumulative discharge q at the top, middle and foot of the slope were tested. And the displacement nephogram was identified by PhotoInfor image processing technology to analyze the hydraulic response law and instability failure process of macroporous slope under different rainfall intensities. The results show that the greater the rainfall intensity, the closer the response time of θ at the foot, middle and top of the slope, the more significant the non-equilibrium flow phenomenon;furthermore, the easier it is to accumulate water at the foot of the slope, the easier it is to form an erosion ditch at the top of the slope, which causes the secondary increase of p at the foot of slope and the advance of pressure relief time at the top of slope. The σ at the top and foot of the slope increases with the increase of rainfall intensity, and then decreases slowly after reaching the peak value. Finally, the σ is released associated with local collapse of slope. The u increases slowly with the increase of rainfall duration and reaches the peak when the slope collapses locally. The greater the rainfall intensity, the greater the peak value of u at the top and step of slope, and the earlier the time to reach the peak value. The peak value of q and v increases with the increase of rainfall intensity. When the rainfall intensity is small, the macropore slope mainly suffers from shallow local sliding fracture. When the rainfall intensity is large, the macropore slope mainly suffers from shallow local scour failure.