公路泥石流防治结构冲磨性能优化研究

作为山区公路一种典型地质灾害的泥石流是液相泥浆与固相岩土的二相混合流,对防治结构的磨蚀破坏极其严重,使防治结构的有效使用寿命缩短35%~50%,降低了防治结构安全性能,严重威胁公路交通的正常运营。为增强防治结构耐久性、提高公路交通的安全性能,作者通过泥石流与防治结构的偶合作用、流体力学理论与固体磨蚀原理,从结构设计和构造材料两方面对防治结构的抗磨性能进行了研究,创建了既能避免泥石流直接冲撞、又能降低泥石流磨损的防治结构轴线方程。根据磨蚀量计算理论,对四川西昌平川泥石流防治结构的磨蚀量进行对比计算,优化后的磨蚀计算量约为优化前的36%,抗御泥石流冲击磨蚀的能力得到显著地增强,显示了优化防治结构的优越性。研究成果为合理设计速、排结构与拦渣坝等防治结构提供了理论依据。但是,作为2相流的泥石流,对防治结构的粘滞、摩擦作用是一个非常复杂的过程,也是正确计算磨蚀量的关键参数之一。因此,进一步展开泥石流体物性研究具有重要价值。     

人工阶梯-深潭防治地震区泥石流的探索

阶梯-深潭是山区河流中常见的一种具有高效消能作用的河床结构。2009年采用人工阶梯-深潭系统对文家沟滑坡体上的新生泥石流沟治理进行野外治理实验。在主沟上游段人工构筑33级阶梯-深潭,经历当年几次暴雨,由于通过在深潭内耗散水流的大部分能量,阻止了沟谷下切并有效地控制了泥石流的发生。对野外实验和数值模拟的结果分析表明,在一定的流量下,阶梯-深潭发育的河流系统有助于单位时间内单位重量水流能量耗散率将趋于最小,可以提升河流系统的稳定性。在地震区的泥石流沟内构筑阶梯-深潭系统有利于加速其稳定的进程,并减少灾害的发生。     

一次奇特的泥石流

在连续晴朗且没有大容量地表水的情况下,浙江省庆元县安南乡小源村洋尾坑发生了泥石流,与通常认为的泥石流的发生由暴雨、冰雪融水或库塘溃坝等水源激发大相径庭。通过访问灾害形成及活动过程和全面调查地质环境条件,认为该泥石流是滑坡的一种特殊运动形式,属于比较独特的泥流,并展开了活动机理研究。     

基于能量概念的泥石流减灾新思路

陆地上发生的很多变迁都是受能量流控制的,特别是在泥石流这种具有复杂性、突发性、群发性、继承性和局部性等特征的山地灾害过程中,能量趋于均衡化是它们发生和输移的根源和驱动力。本文从能量的角庞出发,通过阐述能量线性模型的原理,分析泥石流输移时的各种能量消耗,从宏观角度提出了减轻泥石流灾害的一种新的思路,即可以从控制能量或熵消耗的角度出发,通过减少固体物质来源量和增大摩擦两种途径来采取一系列减灾措施,为制定泥石流防治规划提供参考。     

Size of a debris flow deposition: model experiment approach

 The prediction of the dangerous extent of a debris flow deposition is of vital importance, but difficult to achieve. Precise prediction of the depositional boundary of a debris flow event is impossible, but the size of a debris flow deposition could provide some estimates of the area, length, width, and thickness of a debris flow deposition. Based on in situ depositional experiments performed on a debris flow creek just after debris flows, a rule of thumb expressed by a group of equations containing the multiple-variate nonlinear functions is proposed in this paper. The interrelationships between the size and the causation also are discussed, and some empirical formulae to calculate the causative parameters for different regions are presented. Received: 24 April 1995 · Accepted: 21 June 1995     

弯曲溢洪道挑流消能试验研究

为避免加剧弯曲溢洪道的不良振动,对弯道水流的挑流消能问题进行研究。通过试验研究的方法,提出了一种适用于弯曲溢洪道的新型挑流消能工,结合渠底超高法对弯道水流的干扰,使水流在质量力的作用下分流,有效降低和减小了回水的流量范围,增加了挑流水舌的纵向长度。通过对比两种不同凹岸边墙半径的弯曲束窄差动式斜切挑坎和弯曲连续斜切挑坎的回流、挑流和分流等特性,根据水流运动特性和流线的几何关系,提出了一种判断该新型挑坎发生回水的半理论半经验方法。研究发现高坎的收缩程度和凹岸边墙半径是影响分流和回水的主要因素,通过对高坎水流运动特性的分析,拟合流量、凹岸边墙半径与高坎折冲水流出流方向角γ的经验公式,推导了高坎分流临界角度γc的计算表达式,计算结果与试验测量结果吻合良好,可以为弯道水流挑流消能的工程应用和运行提供参考。     

弯曲溢洪道挑流消能试验研究

为避免加剧弯曲溢洪道的不良振动，对弯道水流的挑流消能问题进行研究。通过试验研究的方法，提出了一种适用于弯曲溢洪道的新型挑流消能工，结合渠底超高法对弯道水流的干扰，使水流在质量力的作用下分流，有效降低和减小了回水的流量范围，增加了挑流水舌的纵向长度。通过对比两种不同凹岸边墙半径的弯曲束窄差动式斜切挑坎和弯曲连续斜切挑坎的回流、挑流和分流等特性，根据水流运动特性和流线的几何关系，提出了一种判断该新型挑坎发生回水的半理论半经验方法。研究发现高坎的收缩程度和凹岸边墙半径是影响分流和回水的主要因素，通过对高坎水流运动特性的分析，拟合流量、凹岸边墙半径与高坎折冲水流出流方向角γ的经验公式，推导了高坎分流临界角度γ_c的计算表达式，计算结果与试验测量结果吻合良好，可以为弯道水流挑流消能的工程应用和运行提供参考。     

中国泥石流起动物理模拟试验研究进展

为进一步提高泥石流起动物理模拟试验的科学性,完善试验体系,采用资料收集与分析方法,总结了近年来中国泥石流起动物理模拟试验开展的现状,从水流冲刷与泥石流起动试验以及人工降雨与泥石流起动试验两个方面论述了中国泥石流起动试验取得的主要进展和理论成果。在国内外泥石流起动物理模拟试验对照基础上,提出中国泥石流起动物理模拟试验研究的建议:提高水流浓度、降雨雨型与土体特征的相似率;加强降雨或水流作用下土体物理力学特征变化与泥石流起动响应研究;推动降雨与汇流共同作用下泥石流起动综合性物理模拟试验的开展。     

底流消能方式水电站泄洪雾化模型试验研究

泄洪雾化现象是伴随着高坝泄洪消能带来的一个负面效应,它对于电厂的安全运行、周围环境等有一定的影响。采用大比尺模型试验方法研究向家坝水电站泄洪雾化问题,利用类似消能工的湾塘水电站泄洪雾化原型观测成果,反馈分析了雾化模型尺度效应,得到了雾化量的相似律,并预测和评价了向家坝水电站泄洪雾化影响。     

具有风景区泥石流治理特色的土木工程措施

风景区泥石流治理不同于其他泥石流的治理。在总结九寨沟风景名胜区泥石流治理土木设计的基础上,提出4种具有风景区泥石流治理特色的土木工程措施。即漂木拦挡、泥沙拦淤、生态保护及景点保护。详细分析了每种技术的减灾需求,在此基础上结合其他泥石流治理设计的成功经验,总结各技术的设计要点,并给出可供参考的成功应用实例。这些成功技术在九寨沟泥石流治理中取得了成功,可为其他风景区泥石流治理借鉴。     

滑坡碎屑流冲击拦挡结构的离散元模拟

拦挡结构可以有效减小滑坡致灾范围、减弱致灾强度。文章以滑坡碎屑流为研究对象,通过对比模型试验和数值模拟结果,校正三维离散元模拟参数,进而研究不同坡脚角度和挡板高度对冲击力、最大水平运动距离的影响。研究结果表明:三个坡脚角度碎屑流冲击力的变化过程存在明显区别,坡脚角度为35°和45°时,冲击力时程曲线经历了两个显著的变化阶段:线性增大、线性减小。而坡脚角度为55°时,碎屑流冲击力时程曲线出现三个变化阶段:线性增加、恒力阶段、线性减小。挡板高度越高,恒力阶段的持续时间越短,冲击力线性减小阶段时间越长。小颗粒（2.5~10 mm）对挡板的冲击效应显著;中等颗粒（10~25 mm）随着挡板高度的增加,对挡板的冲击效应逐渐增大;而大颗粒（25~60 mm）作用在挡板上的冲击效应出现突变,与其他两种颗粒对比,整个运动过程冲击效应不显著。碎屑流的运程随着挡板高度的增加逐渐减小。对比三个坡脚角度下挡板的拦挡效果,坡脚角度α≤45°时,拦挡效果显著。     

河北省太行山区泥石流灾害发育分布特征及防治

由于受太行山区地形地貌、气候特征、区域性地质构造活动及强烈的地壳抬升影响,河北省西部的泥石流极为发育,对人类及其生存环境带来了极大的危害.研究表明,我省太行山区泥石流的发育具有分区性、群发性、周期性及季节性等特征,流域面积一般为1～5km2,流域长宽比在l～4之间,并且在其发生发展过程中常与其它地质灾害相互影响、相互转换.本文系统分析了太行山区复杂的地质构造、地形地貌及独特的气候条件和人类活动对泥石流形成的影响,并对泥石流危险度进行划分,提出了地质环境保护、防灾减灾对策.     

泥石流防治工程损毁度评价

泥石流岩土防治工程被广泛应用于泥石流灾害的治理,而工程的损毁程度会对工程的功能性产生一定的影响,并影响效益的持续发挥。文章以汶川为研究区域,选取18条泥石流沟的岩土防治工程作为研究对象,结合现场考察,对防治工程的损毁程度进行评价。评价指标体系总体上分为拦挡工程因子和排导工程因子2项,细化二级评价指标包括坝基损毁度、坝肩损毁度、坝体损毁度、基础冲刷度、结构冲击度、斜坡推力度等6项。运用模糊综合评价方法构建判断矩阵和隶属度函数,将损毁度等级划分为优、良、中、差四个等级。评价结果显示,除板子沟和登溪沟的防治工程损毁等级为差和中以外,其余泥石流沟内防治工程损毁等级均为良或优,且评价结果与现场考察一致。     

Experimental and numerical investigation for energy dissipation of supercritical flow in sudden contractions

Dealing with kinetic energy is one of the most important problems in hydraulic structures, and this energy can damage downstream structures. This study aims to study energy dissipation of supercritical water flow passing through a sudden contraction. The experiments were conducted on a sudden contraction with 15 cm width. A 30 cm wide flume was installed. The relative contraction ranged from 8.9 to 9.7, where relative contraction refers to the ratio of contraction width to initial flow depth. The Froude value in the investigation varied from 2 to 7. The contraction width of numerical simulation was 5~15 cm, the relative contraction was 8.9~12.42, and the Froude value ranged from 8.9~12.42. In order to simulate turbulence, the k-ε RNG model was harnessed. The experimental and numerical results demonstrate that the energy dissipation increases with the increase of Froude value. Also, with the sudden contraction, the rate of relative depreciation of energy is increased due to the increase in backwater profile and downstream flow depth. The experimentation verifies the numerical results with a correlation coefficient of 0.99 and the root mean square error is 0.02.     

泥石流排导槽研究进展及发展方向

泥石流是我国最常见的地质灾害之一,在5.12汶川地震后表现得尤为突出。排导槽作为一种结构简单、经济适用的防护措施在泥石流的防治工程中发挥了重要作用。本文简要阐述了泥石流排导槽的发展历程,重点分析比较全衬砌槽和软基消能型槽的结构特点、排导原理、优缺点及适用范围,其中全衬砌槽束水冲砂的特点增加泥石流的排泄,减少淤积,适于下游有广阔停淤区域或主河有足够输移能力的泥石流;而软基消能槽设置贯穿型横向潜槛,增大摩擦,降低流速,适于下游有城镇、铁路、工厂等重要基础设施的泥石流;分别从横纵断面优化、材料选择等角度总结了排导槽的研究进展:初步界定排导槽合理纵比降为3°～10°;横断面上对矩/梯形、圆形、V形等几种主要槽型水力条件进行分析比较,得出圆形断面最优;尝试运用高强混凝土等新型材料或结构增加排导槽的抗磨强度,延长其使用年限;综合考虑泥石流地质地貌背景、水文条件、施工难易程度、经济与否等多方面因素,选择最合适的排导工程;指出随着各项土木工程中生态需求的日益增长,今后研究工作中应加强模型试验,尤其是交错齿槛等生态型泥石流排导槽的研究,进一步完善泥石流排导槽的优化设计体系。     

A numerical simulation of debris flow and its application

Debris flow is the flow of solid-fluid mixture and was treated as the flow of a continuum in routing in this study. A mathematical model was proposed to describe debris flow including deposition process and then solved numerically with suitable boundary conditions. Laboratory experiments were also conducted for comparison and calibration of the numerical results as well as for investigation of debris flow phenomena. The numerical model was also applied to simulate the debris flow caused by heavy rainfall in Tungman village of Hualien County located in the east of Taiwan on 23 June 1990. The simulated bed topographies in alluvial fan were in good agreement with those obtained from laboratory experiments and field observations.     

A study of methods to estimate debris flow velocity

Debris flow velocities are commonly back-calculated from superelevation events which require subjective estimates of radii of curvature of bends in the debris flow channel or predicted using flow equations that require the selection of appropriate rheological models and material property inputs. This research investigated difficulties associated with the use of these conventional velocity estimation methods. Radii of curvature estimates were found to vary with the extent of the channel investigated and with the scale of the media used, and back-calculated velocities varied among different investigated locations along a channel. Distinct populations of Bingham properties were found to exist between those measured by laboratory tests and those back-calculated from field data; thus, laboratory-obtained values would not be representative of field-scale debris flow behavior. To avoid these difficulties with conventional methods, a new preliminary velocity estimation method is presented that statistically relates flow velocity to the channel slope and the flow depth. This method presents ranges of reasonable velocity predictions based on 30 previously measured velocities.     

低频泥石流特征及防治 --以四川汶川县茶园沟为例

低频泥石流指30a以上发生1次的泥石流。尽管发生频率很低，但由于自身的特征及人们认识上的原因，其造l戒的人员伤亡和财产损失却居各类泥石流之首。对低频泥石流的研究在预防和减轻泥石流灾害方面有着重要意义。文章以2003年8月9日发生在四川汶川县茶园沟的泥石流为蒯，采用形态调查法和称重法等方法确定了流量、流速及重度。分析了其物质来源及形成的自然和人为原因，探讨了低频泥石流的特征。针对低频泥石流的低频性、破坏性和隐蔽性特点，同时考虑到低频泥石流沟的防治受保护对象的重要程度及资金投入等因素的限制，提出了进行泥石流危险性分区、搞好小流域水土深持、普及泥石流防灾减灾知识及加强监测和预警预报等措施，这对减轻低频泥石流区的灾害有一定的借鉴意义。     

川藏公路特殊碎屑流灾害综合防治技术

川藏公路帕隆藏布沿岸路段广泛发育一种特殊的碎屑流灾害——溜砂坡,危害十分严重。通过近几年的研究与工程实践,溜砂坡灾害的防治对策可归纳为避让与清除、砂源区控制技术、固砂技术、拦砂技术与排砂技术五大类。根据溜砂坡灾害的基本特征、发育阶段及道路工程所处的环境条件,有针对性地选择防治技术,才能取得较好的防治效果。     

Properties of debris flow deposits and source materials compared: implications for debris flow characterization

In the Alps, debris flow deposits generally contain <5% clay‐size particles, and the role of the surface‐charged <2 μm particles is often neglected, although these particles may have a significant impact on the rheological properties of the interstitial fluid. The objective of this study was to compare debris flow deposits and parent materials from two neighbouring catchments of the Swiss Alps, with special emphasis on the colloidal constituents. The catchments are small in area (4 km²), 2·5 km long, similar in morphology, but different in geology. The average slopes are 35–40%. The catchments were monitored for debris flow events and mapped for surface aspect and erosion activity. Debris flow deposits and parent materials were sampled, the clay and silt fractions extracted and the bulk density, <2 mm fraction bulk density, particle size distribution, chemical composition, cation exchange capacity (CEC) and mineralogy analysed. The results show that the deposits are similar to the parent screes in terms of chemical composition, but differ in terms of: (i) particle size distribution; and (ii) mineralogy, reactivity and density of the <2 mm fraction. In this fraction, compared with the parent materials the deposits show dense materials enriched in coarse monocrystalline particles, of which the smallest and more reactive particles were leached. The results suggest that deposit samples should not be considered as representative of source or flow materials, particularly with respect to their physical properties.