IMHE OpenIR  > 山地灾害与地表过程重点实验室
Alternative TitleMotion Features of the Extra-ordinary Water-rock Flow Occurred on July 18, 2013 in Maoniuping Mountain,Mianning
Thesis Advisor马东涛
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name硕士
Degree Discipline建筑与土木工程
Keyword水石流 形成条件 形成机理 运动特征 冲淤特征
Abstract冕宁县牦牛坪2013年7月18日发生的特大水石流,为深入研究水石流提供了一次良好的机会。本文通过实地调查和地区资料分析,在明确其发育背景的基础上,结合室内试验数据,利用前人理论分析成果,对这次特大水石流的形成条件,形成机理,运动特征和冲淤特征进行研究,得到如下结论: (1)水石流沟谷流域面积小(大多小于6 km2),沟床比降大(大于20%),山坡坡度陡,具充分的水石流发育地形条件;沟道内补给源和方式多样,为水石流提供了充分的固体物源;丰富的降雨和冰雪融水以及较大的降水强度成为水石流十分重要的诱发因素。 (2)水石流的形成是沟床物质发生整体型“溃失”,且“溃失”的条件为沟床内最大粒径石块的起动。 (3)水石流体颗粒粗(平均粒径30 cm左右),容重高(1.65~1.85 t/m3),粘度低(堆积物中粉粒+粘粒含量百分比几乎都<2%);水石流在运动中颗粒较分散,适用固体颗粒相互碰撞模型,流速计算适用公式为:U_c=(M_c R^(2?3) i_0^(1?2))?a。 (4)水石流中漂砾的起动,浆体中细颗粒对粗颗粒的润滑和托举作用有效降低了漂砾的“起动门槛”,促进水石流的整体起动;床面漂砾受到容重为γ_m的“准水石流体”起动,适用的起动计算公式:U_c=1.14√(([(γ_s-γ_m))?γ_m ]gd) (H/d)^(1?6)。 (5)水石流具有典型的下切冲刷、岸壁冲刷、弯道冲刷和零星冲刷等冲刷特征,还有堆积扇、心滩堆积、阶地堆积和侧向堆积等堆积特征。沟道呈现明显的沿程堆积和冲淤变化频繁的冲淤变化特征。 (6)水石流沟床表现出明显的自动调整规律:沟道上游主要发生下切冲刷,沟床以调平比降为主,中、下游段河道展宽,沟床以调整断面形态为主。影响沟床自动调整的条件包括泥沙搬运量、剪应力分布和水流流势等。
Other AbstractAn extra-ordinary water-rock flow broke out on July 18, 2013 in Maoniuping mountain Mianning of Sichuan Province, which provided an valuable opportunity to study the water-rock flow. Based on field investigation and data analysis, and combined with laboratory test data, the previous theoretical analysis results and the development background, the formation conditions, formation mechanism, motion feature and characteristics of scouring and sedimentation of water-rock flow are studied in this dissertation. The follow conclusions are gotten: (1) The gully had sufficient terrain condition for water-rock flow with the small basin area (less than 6 km2), a little higher bed gradient (greater than 20%) and steeper hill slope. The multiplicity of ways and sufficiency of sources ensured solid material supply of the water-rock flow. Rich rainfall with the heavy intensity is very important for triggering the water-rock flow. (2) The formation of water-rock flow was the whole type “outburst” of gully deposit materials, and the condition of “outburst” was the starting of the maximum grain size stone. (3) The fluid of water-rock flow has characteristics such as coarser grain size (the average particle size was about 30 cm), higher density (1.65~1.85 t/m3) and lower viscosity ( the content of silt and clay of the deposit was less than 2%). The solid particles were dispersed in the fluid. The applicable model for water-rock flow was the solid particles collision with each other model, and the velocity formula was U_c=(M_c R^(2?3) i_0^(1?2))?a. (4) The fine particles in slurry had lubricating and lifting effect on coarse particles, which was easier for starting of boulders in water-rock flow. The boulders on gully bed were started by the “quasi- water-rock flow” with a bulk density of γ_m, and the starting formula was U_c=1.14√(([(γ_s-γ_m))?γ_m ]gd) (H/d)^(1?6). (5) Water-rock flow had some typical erosion characteristics, such as incised scour, quay wall scour, bend scour, and sporadic scour, which also had the accumulation characteristics such as deposition fan, central bar accumulation, terrace accumulation and lateral accumulation et al. The channel presented obvious scouring-erosion variation characteristics of along accumulation and sediment changes frequently. (6) Water-rock flow gully bed had an obvious automatic adjustment rules that the channel mainly occurs incised scour in upstream and gully bed is mostly leveled gradient, and the channel is mainly broadened in midstream and downstream, where the gully bed keep balanced by adjusting the cross section. The quantity of sand transportation, shear stress distribution and the flow pattern so on factors influenced the gully bed automatically adjusting.
Document Type学位论文
Recommended Citation
GB/T 7714
陈英. 冕宁县牦牛坪“7·18”特大水石流运动特征[D]. 北京. 中国科学院大学,2015.
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