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水源对物源物理、力学特征作用是泥石流起动的内在作用,为研究该作用并阐述泥石流的起动机制,研制十字板改进的剪切流变仪作为主要仪器,以含水量作为水源条件的参数,以剪应力和应变关系作为物源条件研究对象,试验材料选用受含水量影响最显著的细颗粒土(d≤1 mm)开展间歇性人工降雨试验,使试验材料处于5级不同含水量水平,并分别开展加、卸载试验。试验表明,起动前试样在低含水量水平和试验加载条件下,其应变逐渐收敛于稳定值,该值随含水量增加而增大,当含水量达到一定水平(本试验为28.8%,称为起动水平)时,在试验加载条件下其应变不收敛,最终进入运动状态即起动;该结果表明泥石流起动具有流变变形特征,该特征可用本文提出的改进Bingham体模型表达,将试验数据代入模型方程可以确定模型参数。5级含水量条件下试验结果表明该模型参数是含水量的函数,随着含水量增加呈衰减趋势,表明含水量增加导致物源强度降低,最终导致作用于物源上原有力系平衡的失效,进而产生泥石流的起动。采用模型计算所得的卸载应变过程曲线与计算曲线具有较好一致性,表明该模型具有良好的适用性,可用于阐述泥石流的起动机制。
In order to study the action and explain the start-up mechanism of debris flow, a shear rheometer with improved cross-deck was developed as the main instrument. The water content was taken as the parameter of water source condition. Taking the relationship between shear stress and strain as the source condition, the experimental material was selected to use intermittent artificial rainfall test with the fine-grained soil (d≤1 mm), which is most significantly influenced by water content, so that the test material was at the level 5 with different water contents, And carry out plus, unloading test. The experiment shows that the strain of the pre-start sample converges to a steady value under the condition of low water content and test load, which increases with the increase of water content. When the water content reaches a certain level (28.8% in this test, it is called Is the starting level), the strain does not converge under the test loading conditions, and finally it enters the state of motion and starts. The results show that the debris flow start has the characteristics of rheological deformation. This feature can be expressed by the improved Bingham body model proposed in this paper. Model equations determine the model parameters. The test results under the condition of 5-level water content show that the parameters of this model are a function of water content, declining trend with the increase of water content, indicating that the increase of water content leads to the decrease of source intensity and finally to the failure of the original force system balance, In turn, debris flow starts. The curve of unloading strain calculated by the model is in good agreement with the calculated curve, indicating that the model has good applicability and can be used to explain the starting mechanism of debris flow.