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“梯-潭”型泥石流排导槽消能特性研究
Alternative TitleStudy on Energy Dissipation Characteristics of Debris Flow Drainage Channel with Step-Pool Configura
Language中文
李云
Thesis Advisor陈晓清
2015
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震后泥石流 大比降沟道 排导槽 阶梯-深潭 消能特性
Abstract泥石流排导槽是一类应用于流域中下游堆积区的灾害防治工程,目前效果较好的有全衬砌“V”型槽和具备软基消能特性的“东川”槽。“梯-潭”型泥石流排导槽是根据震后泥石流排导工程降坡、控速、消能的需求,结合东川槽的消能原理,依据小岗剑泥石流治理工程箱体消能槽的实践经验,借鉴山区阶梯-深潭系统的体型而提出作新型排导结构,适用于大比降、多物源、高频率、小流域泥石流沟,兼有东川槽消能和全衬砌槽加速输移的性能。 通过公式推导与分析研究了梯-潭槽的纵坡特性;通过野外模型试验改变泥石流容重、一次过程总量、坡度等控制参数,结合数值模拟改变梯-潭槽体型参数,较为完整的揭示了流体在“梯-潭”槽内的运动特性;研究了不同性质流体在槽内的消能机制,分析了各种消能机制所发挥的作用,探讨了容重、一次过程总量、容重及梯-潭槽体型参数对于消能率的影响,给出了不同坡度情形下消能率取值范围;初步给出了梯-潭槽的体型参数设计方法,取得以下成果: (1)纵坡特性 梯-潭槽具有间接降低沟道纵坡的特点,其设计参数阶高H、潭深h、潭长L、排导段l0、设计纵坡i、沟道纵坡i0、潭数 n满足以H-L-l0-n为参数的i-i0二元二次关系。 当a=0,b>0且H值较小时,全衬砌排导槽;当a>0,b=0且H值较大时,东川槽;当a>0,b>0且H值取适宜时,则为梯-潭槽。 (2)运动特征 流体在潭内经历跌落-旋滚-流深跃起等过程,在排导槽中以反复“加速-减速”的方式运动,与之相适应流深则相应的“减少-增加”,实现流体在槽内不冲不淤均衡排泄。 稀性泥石流的阻力主要来自下部泥深交换层颗粒间相互碰撞的离散力及表层浑水的紊动;粘性泥石流阻力主要来自内部的粘滞阻力和与潭内石块的摩擦碰撞搅拌作用。对于水流,在该体型下不同坡度的综合糙率为0.0128~0.0277;对于高含沙水流综合糙率为0.0117~0.0451;对于稀性泥石流,综合糙率为0.0109~0.0588;对于粘性泥石流综合糙率为0.0443~0.0807。 修正的抛程计算公式为: 对于粘性泥石流0.55≤ψ≤0.70;对于稀性泥石流0.70≤ψ≤0.88;对于高含沙水流0.90≤ψ≤0.95。 (3)消能特性 泥石流过流“梯-潭”槽时,有三种消能形式:跌落消能率约为40%-50%,潭内旋滚和类似水跃消能率约为20%-30%,试验中潭内填石的摩擦碰撞搅拌作用消能率约为10%-20%。当流体流量较大时,槽内梯-潭型消能结构完全被淹没,其相对糙度较小,流体直接越过梯-潭消能结构,此时消能率为约为20%。 随着坡增加,消能率有减小的趋势,部分情况下,消能率小幅增加,而后减小,其揭示了不同坡度情形下,能量耗散方式的不同。一次过程总量对消能率的影响相对较小,对于水流、高含沙水流、稀性泥石流影响在20%以内,对于粘性泥石流影响在10%以内。消能率随容重的增加而减少,当达到一定值后,消能率随容重的增加而增加。 对于水流消能率试验取值范围为27.97%~66.27%,高含沙水流消能取值范围25.66% ~52.95%,稀性泥石流消能率取值范围18.78%~64.10%,粘性泥石流消能率取值范围57.77%~84.75%。 在单宽流量q一定的情况下,消能率随阶梯高度的增加而增加。采用的坡比范围为 1:2~1:3,在此坡比范围内,阶梯消能能够达到60% 。潭的配置密度,l0/L大于1时,其对消能率影响不大。 (4)参数设计方法 单个阶梯高度H宜取值为3~5m。潭长L,潭长设计值:L=ζ(1.3~1.5)L1。排导段l0,一般取1L~3L,对于稀性泥石流取较大值,粘性泥石流取较小值。埋入深度h,按坝后冲刷深度计算,且不应小于(1/3~1/2)H。潭内填筑石块,由上自下,粒径变粗;填筑不宜太满,预留(1/3~1/2)设计泥深高度。可自由配置潭的个数n,且间距及每个潭的体型可不同。
Other AbstractDrainage channel is one of engineering mitigation measures used in deposition zones, including the "V" shape debris flow drainage channel and ladder shape debris flow drainage channel. Imitating the step-pool system in mountain rivers as prototype,referring to the energy dissipation theory of ladder shape debris flow drainage channel,and taking theengineering practice of debris flow drainage channel with box configuration in Xiaogangjian Gully into consideration,the debris flow drainage channel with step-pool configuration(DCSC) is proposed in accordance with demand to decrease the slope gradient and control the flow velocity in earthquake areas. The DCSC is available for small watershed gullies with high gradient,abundant loose mass and occurrence in high frequency,combining the capacity of energy dissipation with the capacity of speeding up debris flow to deliver. The characteristic in longitudinal gradient is analysed by formula derivation.The bulk density,gross of the process,longitudinal gradient are changed in the model exeriment and the shape parameters H-L-l0 are changed in the numerical simulation.Before to discusse the energy dissipation mechanism the dynamicbehaviour of the channelized debris flow is revealed.The energy dissipation mechanism is different when fluid volume weight creases.The detailed analysis is carried out on the energy dissipation rate,to understand the factos such as bulk density,gross of the process,longitudinal gradient and shape parameters H-L-l0's effect to energy dissipation rate,and to get the range of energy dissipation rate in different longitudinal gradient.Based on the above sdudy,the preliminary design method of shape parameters are obtained. (1)The characteristic in longitudinal gradient The DCSC has the function of decreasing slope gradient,and the relationship between i and i0 satisfies a binary quadratic equations with parameters acceleration index a and the deceleration index b.When a=0,b>0,H is low,the channel is fully overspreaded with concrete;When a=0,b=0,H is high,the channel is filled with ladder shape;When a>0,b>0,H is 3-5meters,the channel is filled with step-pool configuration. (2)The dynamic behaviour of the channelized debris flow The fluid fall into the pool with the turbulence occuring,then the fluid roll out of pool like hydraulic jump,in other words,the fliud move in a "peed up-speed down" way,which will transport the channelied debris flow smoothly. For diluted debris flow,the resistance is mainly from the lowwer mutual collision of sediment and the turbulence of upper water,while for viscous debris flow,the resistance is mainly from viscous drag and the friction of blocks in pool. For water,the n is 0.0128~0.0277;for hyper-concentration flow,the n is 0.0117~0.0451;for diluted debris flow,the n is 0.0109~0.0588;for viscous debris flow,the n is0.0443~0.0807. The correctionaljet distance: For viscous debris flow, 0.55≤ψ≤0.70;for diluted debris flow ,0.70≤ψ≤0.88;for hyper-concentration flow,0.90≤ψ≤0.95. (3)The characteristic of energy dissipation When debris flow go trough the DCSC,the energy dissipate in three ways.Energy dissipation rate by fluid fall is about 40%~50%,energy dissipation rate by turbulence in the pool is about 20%~30%,and energy dissipation rate by the friction of blocks in pool is about 10%~20%.When the volume flow rate is high,the step-pool configuration in the DCSC is submerged,namely the surface roughness decrease,the step-pool configuration can not work,leading to the energy dissipitation rate decrease to about 20%. When the lognitudinal gradient value is high,the energy dissipation rate goes down,in some cases the energy dissipation rate firstly goes up and then goes down,which reveals the different energy dissipation mechanism in different lognitudinal gradient.The gross of the process has little effect on energy dissipation.When the bulk density crease,the energy dissipation rate firstly goes down and then goes up. For wat
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/14137
Collection山地灾害与地表过程重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
李云. “梯-潭”型泥石流排导槽消能特性研究[D]. 北京. 中国科学院大学,2015.
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