沟床侵蚀型泥石流起动临界条件试验研究

Debris flow due to channel-bed failure is one of main types of debris flows. It can cause huge damage and death –tolls once it occurred. The critical condition model can not be actually used due to complicated initiation mechanism of debris flow generated by runoff. The difficulty is how to quantitativly determine depth of active layer. The initiation for debris flow due to channel-bed failure is studied experimentally at different bed slopes and different size distributions of deposits. Processes for initiation of debris flow triggered by runoff are observed and analyzed to reveal the mechanism for initiation of debris flow.The change law of the depth of active layer is analyzed along with the change of the bed slopes,grain size parameters of deposit,and shear strength index of deposit so as to determine the main factors which influence the depth of active layer. Quantitative analysis is applied to shear strength and resisting shear strength of deposits. A pridiction model is established to compute the critical conditions for initiation of debris flow due to bed-failure by employing Mohr coulomb failure criteria. The research results can be used to pridct the critical conditions for initiation of debris flow due to channel-bed failure in mountain area, which can also provide theoretical and technical support for preventing and early warning debris flows.

沟床侵蚀性泥石流是泥石流的主要类型之一，一旦暴发可造成巨大人员和财产损失。但由于该类型泥石流启动的复杂性，现有泥石流起动模型与其适用性仍待提高，其难点在于如何定量描述泥石流起动时刻的活动层厚度。本研究拟开展不同沟床比降和不同堆积物级配条件下的沟床侵蚀型泥石流起动水槽试验，分析沟道堆积物受水流冲刷生成泥石流的起动全过程，采用摩尔-库伦破坏准则进行理论建模，通过对试验数据的反演分析，确定堆积物活动层厚度，分析泥石流起动时刻活动层厚度随沟床比降、径流条件、沟床堆积物级配及强度等的变化规律，并定量表达堆积物活动层厚度，开展沟床堆积物剪应力和抗剪应力的定量分析，进而建立沟床侵蚀型泥石流起动临界条件（径流量、径流深）计算模型，研究成果可用于我国山区沟道侵蚀型泥石流起动临界条件预测，为沟床侵蚀性泥石流防灾减灾提供理论依据。

洪水侵蚀沟床形成泥石流是泥石流的主要类型之一，研究其形成机理和形成的临界条件有助于泥石流治理和预警预报。借鉴河流动力学中推移质输沙理论，对已有洪水侵蚀沟床形成泥石流的水槽试验资料分析表明，洪水侵蚀沟床所形成泥石流的体积输沙浓度随沟床固体颗粒物质无量纲切应力的增大而增大，且呈幂函数关系。采用定量标准作为泥石流形成判别条件，则泥石流形成临界条件是体积输沙浓度计算公式的一个特例，此时床面颗粒无量纲切应力为0.655，远大于泥沙颗粒起动无量纲切应力。基于水槽试验资料和蒋家沟原型观测资料的适用性分析表明，本研究所建立的体积输沙浓度计算公式是合理的，能够反映泥石流形成和输移规律，可用于指导泥石流形成临界水力条件的计算。通过本项目研究，发表论文4篇，其中SCI论文1篇，EI论文1篇；累计申请发明专利3项，其中2项已获授权。