粘性泥石流固-液两相相互作用试验研究

Dynamic properties such as velocity, discharge, and impact force are required in debris flow control engineering design and debris flow risk zoning. Dynamic models of debris flow are fundamental approaches to estimate these properties. However, some key parameters are difficult to determine in these models because of the complicated interaction between solid and fluid phases in debris flow. Therefore, in this project instruments and equipments in the Dongchuan Debris Flow Observation and Research Station (DDFORS), Chinese Academy of Sciences will be used to conduct experimental studies on the interaction mechanism between solid and fluid phases in viscous debris flow. The following contents are included in the study: Firstly, flume experiments and locale simulation experiments are performed at DDFORS and Huajiaopo Gully-a tributary of Jiangjia Gully, respectively. Normal stress and pore fluid pressure are measured in these experiments. Thus a method to determine the critical particle size of viscous debris flow can be proposed with these data. Secondly, fluid phase samples and solid phase samples are prepared for soil mechanics experiments to obtain internal friction angle of the solid phase. Then how the internal friction angle is affected by the fluid phase will be studied. Meanwhile, rheological tests are performed to study how rheological characteristics of the fluid phase are affected by the solid phase. Finally, on the basis of above researches the two-phase flow model of viscous debris flow is improved and tested with observations in Jiangjia Gully. With these studies, simulation results of debris flow models can be improved, and thus they can provide more reliable support for debris flow prevention and mitigation.

泥石流动力学模型是计算泥石流防治工程设计和危险性分区所需流速、流量、冲击力等动力学参量的基本手段，而泥石流中固相和液相的复杂相互作用使得模型中的一些关键参数难以确定。针对这一问题，本项目将利用中国科学院东川泥石流观测研究站的观测和实验条件，开展粘性泥石流固-液两相相互作用试验研究。具体内容包括：在观测站开展粘性泥石流流槽试验，并在蒋家沟冲沟滑脚坡沟开展现场模拟试验，进行正应力和孔隙水压力观测，反算泥石流固、液两相分界粒径，确定分界粒径的计算方法；配制液相和固相材料，在观测站开展休止角试验和流变试验，研究液相作用下固相内摩擦角的变化规律和固相作用下液相宏观流变参数的变化规律，得到二者的数学表达式；在上述研究基础上改进现有的粘性泥石流两相流模型，利用蒋家沟的观测资料进行模型验证。通过该项研究，将提高粘性泥石流两相流模型的模拟精度，为泥石流防灾减灾提供更为可靠的动力学支持。

在泥石流两相流模型中，液相由水和细颗粒构成，固相为粗颗粒。固相和液相的相互作用是泥石流动力学研究的重要内容。针对这一问题，本项目开展了大量土力学试验和流变实验进行了研究，具体内容包括：（1）提出颗粒级配分析法确定固相和液相的分界粒径，在云南东川蒋家沟开展泥石流沉降试验，证明该方法的可行性；将该方法应用于蒋家沟原型泥石流，得到了分界粒径和泥石流密度的经验关系式。（2）从云南省和四川省的多条泥石流沟采集样品，配置不同固体颗粒体积浓度的泥浆悬浮液，测量其流变曲线，分析浆体刚度系数和屈服应力与固体颗粒粒径级配和体积浓度的关系，建立了估算浆体流变参数的经验关系式，同时讨论了浆体粘度计算中所需关键参数——最大体积浓度的确定方法。（3）利用蒋家沟泥石流堆积物配置不同密度粘性泥石流原样对应的不同上限粒径的浆体，开展流变试验，分析较粗的颗粒加入细颗粒浆体后流变参数的变化规律，建立了粗颗粒浆体与细颗粒浆体的相对粘度和相对屈服应力间的经验关系式。（4）开展砾石的堆积实验，测量砾石在空气中、水中和泥浆中的天然休止角，对比显示浆体的存在对砾石天然休止角没有显著影响；利用<0.075mm的细颗粒配置不同密度的浆体，开展0.5-1mm的砂在各浆体中的流变试验，分析浆体对砂的运动阻力的影响，测量结果显示浆体的存在有利于附加孔隙水压力的保持，从而能够降低砂的运动阻力，浆体浓度越高、剪切速率越大，减阻作用越显著。（5）根据粘性泥石流固相和液相分界粒径的研究结果以及两相之间相互作用的研究结果，提出了粘性泥石流运动阻力的计算方法，构建了粘性泥石流两相流模型的框架。