密实及稀疏泥石流的流动性控制因素  

Control factors for mobility of dense and dilute debris flows

作　　者：宋东日 陈倩 陈晓清[1,2] 周公旦 白艺彤[1,2] 胡洪森 SONG DongRi;CHEN Qian;CHEN XiaoQing;ZHOU GongDan;BAI YiTong;HU HongSen(Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,Chengdu 610041,China;University of Chinese Academy of Sciences,Beijing 100049,China;China-Pakistan Joint Research Center on Earth Sciences,Chinese Academy of Sciences-Higher Education Commission(Pakistan),Islamabad 45320,Pakistan)

机构地区：[1]中国科学院水利部成都山地灾害与环境研究所,成都610041 [2]中国科学院大学,北京100049 [3]中国-巴基斯坦地球科学研究中心,中国科学院-巴基斯坦高等教育委员会,伊斯兰堡45320,巴基斯坦

出　　处：《中国科学：技术科学》2022年第4期585-598,共14页Scientia Sinica(Technologica)

基　　金：国家自然科学基金(批准号:41925030,42077256,51809261);中国科学院“西部之光”和四川省科技计划(编号:2020YJ0002)资助项目。

摘　　要：泥石流是山区常见的地质灾害之一,固-液两相协同作用使泥石流明显区别于崩塌碎屑流、洪水等其他地质流体.由于泥石流固-液两相相互作用的复杂性,现阶段泥石流流动性研究主要集中在密实泥石流(体积固相浓度~0.6,也称为黏性泥石流).然而,对密实泥石流向稀疏泥石流转变(体积固相浓度0.6~0.4)中的物理过程研究较少.本研究以体积固相浓度和液相黏度为变量,通过一系列泥石流水槽实验对应力状态和孔隙水压的精准测量,探究体积固相浓度的变化对孔隙水压及泥石流流动性的影响,揭示密实泥石流及稀疏泥石流的流动机理.实验结果表明,泥石流的高流动性与液化程度密切相关.在密实泥石流向稀疏泥石流的转变过程中,固相颗粒从剪胀状态过渡到剪缩状态,孔隙水压上升导致泥石流液化,流动性激增.剪应力的计算值和实测值对比表明,密实泥石流的剪切阻力由颗粒间摩擦主导,而稀疏泥石流的剪切阻力则部分来源于液相黏性,因此表征密实流体剪切阻力的流变关系不足以完全描述稀疏流体的流变行为,充分考虑颗粒间相互作用(摩擦、碰撞)和液相黏性的模型有助于揭示稀疏泥石流的流动机理,这一点有待进一步研究.Debris flow is a commonly occurring geological hazard in mountainous areas.The solid-liquid coupling makes the debris flows distinct from other geophysical fluids such as debris avalanches and floods.Owing to the complexity of this solid-liquid interaction,current research of debris-flow mobility focuses mainly on dense debris flows with a volumetric solid concentration of~0.6.However,few studies focus on the physical processes occurring in the transition from dense to dilute debris flows with volumetric solid concentrations of 0.6-0.4.The objectives of this study are to explore the effects of changes in volumetric solid concentration on pore water pressure response and debris-flow mobility and to reveal the mechanisms in the transition from dense to dilute debris flows.Taking the debris-flow volumetric solid concentration and fluid viscosity as variables,a series of well-instrumented flume experiments is conducted.The results show that the high mobility of debris flow is closely related to the state of liquefaction.In the transition from dense to dilute debris flows,the shear dilatancy(state of solid particles)shifts from positive(dilation)to negative(contraction).As a result,the increase in pore water pressure causes the debris flow to liquefy,and the mobility surges accordingly.According to the calculated and measured shear stresses,it is apparent that the shear resistance of dense(dilute)debris flows is dominated by friction between the particles(viscous drag).An employed rheological model shows that the shear resistance in dense debris flows is insufficient for describing the rheological behavior of dilute flows.Models considering the interaction between particles,including friction and collision,and the viscosity of the fluid phase are warranted in future research.

关 键 词：泥石流 流动性 剪胀效应 体积固相浓度 孔隙水压 库仑摩擦 

分 类 号：P642.23[天文地球—工程地质学]