滑坡碎屑流颗粒分选效应的数值模拟
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摘要
大量粗细不均匀的碎屑岩粒及孤大块石在滑坡碎屑流运动过程中的相互作用产生颗粒分选效应,影响了滑坡碎屑流的运移堆积特征及致灾效应。以模型试验的资料和数据为依据,运用三维颗粒离散元素法,建立滑坡碎屑流颗粒流数值模型,从滑体运动堆积过程中不同粒径组分的分布位置和动能两方面研究了滑坡碎屑流颗粒分选效应的形成过程,探讨了颗粒分选效应的形成机制。结果表明:滑坡碎屑流运动过程中,粗颗粒组分易获得较大速度并向滑体表层及前缘运移,细粒组分运动速度较慢,并向滑体底层及后部聚集,这种颗粒分选效应最终导致了滑体反粒序分布结构的形成。滑坡碎屑流颗粒分选效应是由振动筛分、小颗粒耗能较大率先停积、大颗粒碰撞分离等动力学机理共同作用的结果。
The interactions between the component particles of a mobilized landslide debris flow with varied sizes cause solids segregation,therefore governing the dynamic characteristics and geohazard potential level of landslide debris flow. From the aspects of the distribution and kinetic energy of different particle size components of a mobilized landslide debris flow,the forming process and formation mechanism of solids segregation were investigated in the present study by using a three-dimensional discrete element method together with the results of model testing. The results of existing studies suggest that the large particle components tend to get large speeds and migrate to the surface and front edge of the sliding body. The fine-grained components move slowly and accumulatetoward the bottom and back of the sliding body. This solids segregation effect eventually leads to the inverse grading form of the landslide deposits. Solids segregation in landslide debris flows is a consequence of the kinematic sieving,the preferential sedimentation of little particles and the collision of large particles.
The interactions between the component particles of a mobilized landslide debris flow with varied sizes cause solids segregation,therefore governing the dynamic characteristics and geohazard potential level of landslide debris flow. From the aspects of the distribution and kinetic energy of different particle size components of a mobilized landslide debris flow,the forming process and formation mechanism of solids segregation were investigated in the present study by using a three-dimensional discrete element method together with the results of model testing. The results of existing studies suggest that the large particle components tend to get large speeds and migrate to the surface and front edge of the sliding body. The fine-grained components move slowly and accumulatetoward the bottom and back of the sliding body. This solids segregation effect eventually leads to the inverse grading form of the landslide deposits. Solids segregation in landslide debris flows is a consequence of the kinematic sieving,the preferential sedimentation of little particles and the collision of large particles.
引文
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[15]徐小敏,凌道盛,陈云敏,等.基于线性接触模型的颗粒材料细-宏观弹性常数相关关系研究[J].岩土工程学报,2010,32(7):991-998.
[16]韩燕龙,贾富国,唐玉荣,等.颗粒滚动摩擦系数对堆积特性的影响[J].物理学报,2014,63(17):165-171.
[17]舒安平,杨凯,李芳华,等.非均质泥石流堆积过程粒度与粒序分布特征[J].水利学报,2012,43(11):1322-1327.
[18]FAN X Y,TIAN S J,ZHANG Y Y.Mass-front velocity of dry granular flows influenced by the angle of the slope to the runout plane and particle size gradation[J].Journal of Mountain Science,2016,13(2):234-245.
[19]樊晓一,李天话,田述军,等.未完全受阻地震滑坡运动距离的影响因素及机制分析[J].地震地质,2017,39(4):754-767.
[2]郝明辉,许强,杨兴国,等.高速滑坡-碎屑流颗粒反序试验及其成因机制探讨[J].岩石力学与工程学报,2015,34(3):472-479.
[3]ZHOU GGD,NG CWW.Numerical investigation of reverse segregation in debris flows by DEM[J].Granular Matter,2010,12(5):507-516.
[4]王玉峰,程谦恭,朱圻.汶川地震触发高速远程滑坡-碎屑流堆积反粒序特征及机制分析[J].岩石力学与工程学报,2012,31(6):1089-1106.
[5]陆鹏源,侯天兴,杨兴国,等.滑坡冲击铲刮效应物理模型试验及机制探讨[J].岩石力学与工程学报,2016,(6):1225-1232.
[6]KOKELAAR B P,GRAHAM R L,GRAY J M N T,et al.Fine-grained linings of leveed channels facilitate runout of granular flows[J].Earth&Planetary Science Letters,2014,385(1):172-180.
[7]周公旦,孙其诚,崔鹏.泥石流颗粒物质分选机理和效应[J].四川大学学报(工程科学版),2013,45(1):28-36.
[8]BAGNOLD R A.Experiments on a gravity-free dispersion of large solid spheres in a Newtonian fluid under shear[J].Proc.roy.soc.london,1954,225(1160):49-63.
[9]LUN C K K,SAVAGE S B,JEFFREY D J,et al.Kinetic theories for granular flow:inelastic particles in Couette flow and slightly inelastic particles in a general flow field[J].Journal of Fluid Mechanics,2006,140(140):223-256.
[10]王品,徐则民.头寨大型高速远程滑坡碎屑流堆积体的粒度组成[J].山地学报,2013,31(6):745-752.
[11]张明,王正波,孙琳.滑坡碎屑流高速远程机制环剪试验研究[J].岩石力学与工程学报,2016,(S1):2673-2681.
[12]JIANG Y,TOWHATA I.Experimental study of dry granular flow and impact behavior against a rigid retaining wall[J].Rock Mechanics&Rock Engineering,2013,46(4):713-729.
[13]胡国明.颗粒系统的离散元素法分析仿真[M].湖北武汉:武汉理工大学出版社,2010:1-10.
[14]曹文,李维朝,唐斌,等.PFC滑坡模拟二、三维建模方法研究[J].工程地质学报,2017,25(2):455-462.
[15]徐小敏,凌道盛,陈云敏,等.基于线性接触模型的颗粒材料细-宏观弹性常数相关关系研究[J].岩土工程学报,2010,32(7):991-998.
[16]韩燕龙,贾富国,唐玉荣,等.颗粒滚动摩擦系数对堆积特性的影响[J].物理学报,2014,63(17):165-171.
[17]舒安平,杨凯,李芳华,等.非均质泥石流堆积过程粒度与粒序分布特征[J].水利学报,2012,43(11):1322-1327.
[18]FAN X Y,TIAN S J,ZHANG Y Y.Mass-front velocity of dry granular flows influenced by the angle of the slope to the runout plane and particle size gradation[J].Journal of Mountain Science,2016,13(2):234-245.
[19]樊晓一,李天话,田述军,等.未完全受阻地震滑坡运动距离的影响因素及机制分析[J].地震地质,2017,39(4):754-767.