砾石土分形特征及其与泥石流启动关系试验

对116条泥石流沟取样,所取土样共182个,通过室内颗分试验得到其颗粒组成特征,以此为基础引入分形理论计算各土样的分维值,并分析分维值与级配特征之间的关系。分析发现:泥石流源区砾石土以一重分形特征为主,分维值介于2.250~2.798之间,分维值大的砾石土颗粒组成较为均匀,分维值减小,砾石土中的细颗粒含量逐渐降低。基于砾石土分维值分布区间,在野外配置土样开展泥石流启动试验,综合分析试验现象、孔隙水压力及含水量变化情况得到以下结论:形成泥石流的砾石土具有临界特征,分维值小于2.4的砾石土不易形成泥石流;分维值介于2.4~2.6时,以土力类泥石流为主,泥石流重度较高且规模较大;分维值介于2.6~2.7时,以水力类泥石流为主,泥石流的重度较低,以稀性泥石流为主,并伴有明显的阵性特征。分维值及降雨条件相同时,土体变形(未启动形成泥石流)或破坏启动形成泥石流的时间与密度呈正相关关系。     

泥石流源区砾石土的粒度分形特征

以19条泥石流沟源区75个砾石土试样的颗分数据为基础,应用分形理论研究泥石流沟源区砾石土粒度组成特征,并对粒度分形特征与土体颗粒组成的关系进行了讨论。结果表明:1.粒度分布具有分形特征,以一重分形特征为主;2.一重分形特征表明土体各粒组的含量连续分布性较好;二重分形表明土体各粒组的含量连续分布相对较差,某一粒组含量存在突变;3.所研究的沟道平均粒度分维值Da在2.45～2.78间,且平均粒度分维值Da随粘粒含量Pc增加逐渐增大,具有一重分形特征的沟道二者满足关系式Da=0.108ln(Pc)+2.511。最后探讨了研究源区砾石土粒度分形特征的意义。     

西北地区泥石流沟形态因素的非线性分析——以兰州市为例

以兰州市区96条主要的泥石流沟为例,利用分形理论的统计自相似性对泥石流沟数的累计分布随沟谷形态要素沟道比降、汇水面积和沟道长度的变化进行了分析;并与不同流域形态要素的分维进行了比较,探讨了分维不同的原因。兰州市区泥石流沟三个形态要素均具有统计意义上的自相似性,其中以汇水面积显示出分维最小(0.46),沟道长度次之(0.71),沟道比降最大(1.09)。分维的大小描述了作为系统的沟谷及其泥石流的形成的空间结构,即分形结构,同时也反映了不同形态要素对系统所起作用的差异,分维越小,所起作用越显著。其结果对西北干旱半干旱地区石流灾害的进一步研究与防治提供了新的思路。     

泥石流的分形特征及其意义

分析了泥石流流体和堆积物粒度分布的分形结构特征，其分维值介于２￣３之间，平均值分别为２．７１和２．６５左右。研究了泥石流沟水系的分形特征及其在不同观察尺度下分维的变化特征，结果表明，分维可作为描述泥石流粒度成分和泥石流沟水系的参数，反映了泥石流活动的形成演化特征，在此基础上，论述了分维的研究意义。     

沙漠化的分形特征研究

在国内外有关学者研究的基础上,运用分形理论研究沙漠化的分形特征。结果表明:①作为风沙地貌形成的物质基础──沙粒,其粒径分布具有分形特征,其分维值的大小差异体现了沙物质分布的区域差异性。②风沙地貌是一种典型的分形几何实体,沙丘分布具有分形特征,其分维值体现了风沙地貌的自相似性规律。③风沙流结构不但是分形,而且是多重分形,其分维值与风速有着极大的关系。④荒漠绿洲景观镶嵌结构具有分形特征,各景观要素的分维值大小代表着该要素镶嵌结构的复杂性和稳定性程度。在黑河流域,自然绿洲的镶嵌结构最具复杂性,也最具稳定性。⑤沙漠化过程具有多重分形特征,如果用降水和风速为标度度量沙漠化过程,都表现出某种不规则性。     

黄河上游十大孔兑水系分形特征与侵蚀发育阶段研究（英文）

水系分形维数(Fractal dimension of gully network,D_g)反映了河网分布和水系发育的复杂程度。以位于黄河上游内蒙古段十大孔兑上游丘陵沟壑区为研究对象,利用计盒维数的方法,研究其水系分形特征,同时利用水系分维数D判断流域地貌所处的侵蚀发育阶段。结果表明,(1)以毛不拉孔兑为例,利用人工判定法,相关系数检验法和拟合误差相结合的方法确定无标度区为20~370 m。且各孔兑的地貌形态在该无标度区间内均表现出很好的分形特征,计盒维数可作为流域地貌形态分形特性的量化指标。求得十大孔兑上游丘陵沟壑区的水系分维数D_g为1.08~1.14。(2)十大孔兑水系分维值在不同的汇流面积阈值下变化不大;径流模数与河网分维存在正相关关系。产沙模数与河网分维的线性正相关关系反映了地貌发育幼壮年期地形条件对产沙的影响。(3)按水系分维数与流域起伏程度、坡度及等高线分维值的关系,就十大孔兑而言,当D_g≤1.06时,流域处于幼年期;当D_g1.06时,流域进入壮年期。水系分维数、高程积分值指示十大孔兑上游流域地貌均处于壮年期。     

不同比例尺下中国水系分维数关系研究

应用分形理论,再次验证整个中国水系及各流域水系分形特征的客观存在;通过比较1:450万及1:1200万比例尺计算的分形维值大小及变化规律,表明单一尺度的分形规律在其它尺度下依然存在;大比例尺条件下计算得到的分形维值也大,且各层次不同流域的分维值在不同比例尺条件下的变化也呈现相同的趋势,表明图源比例尺对分维计算值的影响。     

从空间Poisson过程看蒋家沟泥石流

云南东川蒋家沟泥石流频率高,变化多.每场泥石流包含几十到几百个阵流,各阵流具有不同的密度、流体性质和运动形态,流量涨落达3个数量级.这些特征意味着泥石流具有很强的随机性.根据蒋家沟的演化分区和野外观测,可以发现泥石流形成于特殊的源地分支.土体活动(包括滑坡、崩塌和局部的土体流动等)随机发生在那些分支流域,如果认为各源地的土体活动是独立的,而且活动强度正比于源地的面积,那么泥石流的形成和汇流就是一个空间Poisson过程.其结果是阵流流量服从指数分布,这很好地符合蒋家沟的泥石泥观测数据.从蒋家沟泥石流的随机性可见,泥石流依赖于流域的特定源区及其分布,而不是笼统地取决于全流域的地貌或几何因子.     

泥石流流域的形态特征

泥石流是特殊的流域侵蚀作用,同其他流域过程一样,密切联系着流域的形态特征.一般说来,泥石流都发生在小流域(102km2以下),而经典的流域形态研究所涉及的流域范围却达到107km2的尺度.我们想知道泥石流小流域是否具有特殊的数量特征.通过流域特征量的统计,我们看到,与一般流域相比,泥石流小流域的特征参数之间的关系形式上相同,而在数值上不同,这从一个方面肯定了流域演化存在着普遍规律(如自组织临界性),同时也证明泥石流是流域演化历史的"特殊一幕".     

桂东南容县花岗岩残积土粒度分形与物理参数的关系

桂东南容县花岗岩残积土滑坡灾害频发。为明确残积土粒度组成以便揭示滑坡形成机制,文中基于花岗岩残积土的土工试验数据和详查资料,利用分形理论揭示四个深度(0~30cm、30~50cm、50~70cm、滑动面(1~3m))土体粒度分形特征与颗粒含量、物理性质参数的关系。结果表明:(1)花岗岩残积土主要由细砾(粒径2~5mm)和砂粒(粒径 0.075~2mm)组成,粒度分布在无标度区间[0.075,5]内具有一重分形特征;(2)残积土平均分形维数由大即小依次是:D50-70(2.7244)>D滑动面(2.6910)>D0-30(2.6893)>D30-50(2.6480);(3)分形维数与粉砂含量呈极显著正相关,正相关性随深度增加而增大,与细砾和粗砂含量呈负相关性,即分形维数越大,粉砂含量越高,而细砾和粗砂含量越低;(4)D30-50、D滑动面与渗透系数、干密度呈显著负相关。     

泥石流颗粒组成的分形特征

1 IntroductionD ebris flow s in certain sense are a process of m ass interchanges through erosion and depositionbetw een the fluid and the sedim ent; and the interchange of m aterial caused change in thestructure of the flow s that can be ultim ately redu…     

Sources of debris flow material in burned areas

The vulnerability of recently burned areas to debris flows has been well established. Likewise, it has been shown that many, if not most, post-fire debris flows are initiated by runoff and erosion and grow in size through erosion and scour by the moving debris flow, as opposed to landslide-initiated flows with little growth. To better understand the development and character of these flows, a study has been completed encompassing 46 debris flows in California, Utah, and Colorado, in nine different recently burned areas. For each debris flow, progressive debris production was measured at intervals along the length of the channel, and from these measurements graphs were developed showing cumulative volume of debris as a function of channel length. All 46 debris flows showed significant bulking by scour and erosion, with average yield rates for each channel ranging from 0.3 to 9.9 m³ of debris produced for every meter of channel length, with an overall average value of 2.5 m³/m. Significant increases in yield rate partway down the channel were identified in 87% of the channels, with an average of a three-fold increase in yield rate. Yield rates for short reaches of channels (up to several hundred meters) ranged as high as 22.3 m³/m. Debris was contributed from side channels into the main channels for 54% of the flows, with an average of 23% of the total debris coming from those side channels. Rill erosion was identified for 30% of the flows, with rills contributing between 0.1 and 10.5% of the total debris, with an average of 3%. Debris was deposited as levees in 87% of the flows, with most of the deposition occurring in the lower part of the basin. A median value of 10% of the total debris flow was deposited as levees for these cases, with a range from near zero to nearly 100%. These results show that channel erosion and scour are the dominant sources of debris in burned areas, with yield rates increasing significantly partway down the channel. Side channels are much more important sources of debris than rills. Levees are very common, but the size and effect on the amount of debris that reaches a canyon mouth is highly variable.     

A morphometric analysis of gullies scoured by post-fire progressively bulked debris flows in southwest Montana, USA

In the fall of 2001, an intense thunderstorm in southwest Montana triggered many debris flows in the burned area of Sleeping Child Creek. In most instances, the debris flows cut deep gullies into previously unchannelized colluvial hollows and deposited large volumes of sediment onto the valley floor. The presence of rill networks above the gullies as well as the absence of landslide features indicate that the gullies were scoured by progressively bulked debris flows, a process in which dilute surface runoff becomes increasingly more laden with sediment until it transforms into a debris flow. In this contribution, we present a morphometric analysis of six of the gullies to better understand this relatively understudied process. We find that the locations of the rill heads and gully heads conform to slope-area thresholds that are characteristic of erosion by overland flow. Our data also suggest that the volumes of the debris flows increase exponentially with normalized drainage area, thus lending support to an assumption used in a recently proposed debris flow incision law. Finally, the debris flow fans have been relatively unaltered since deposition, suggesting that the valley may be currently aggrading while the hillslopes are being denuded.     

岷江上游潜在性泥石流堰塞湖危害及判识

汶川地震造成泥石流形成条件的改变,其次生灾害堰塞湖的危害已开始显现。如何对震后潜在性泥石流堰塞湖进行判识,成为迫切需要解决的问题。选取岷江上游映秀至汶川段为研究区,通过分析震后泥石流形成条件的变化、典型泥石流堰塞湖的危害及松散物质储量,选取潜在性泥石流堰塞湖的判识指标,利用模糊物元可拓模型,建立潜在性泥石流堰塞湖的综合判识模式。通过判识,研究区形成泥石流堰塞湖可能性高的一级支沟有17条,主要集中分布在映秀镇至草坡乡段,此段将是今后受堰塞湖危害的高危地段。     

西藏中尼公路沿线的泥石流

中尼公路是西藏西南部经济发展的动脉，沿线泥石流灾害严重威胁到线路的正常运营，本研究根据航空照片和卫星图象解译结果，结合现场踏勘校对，深入地研究了沿线700km范围内的环境背景条件和泥石流活动规律，确定沿线有泥石流沟842条，其中沟谷型泥石流沟474条，在公路一侧直接危害公路的沟谷型泥石流241条，深入地探讨了这一高原特殊环境下的泥石流活动特性；为公路部门提供了泥石流防治方案，成为线路整治改建的依据。     

The rock-avalanche of February 1995 at Claix (French Alps)

The sedimentology of a rock-avalanche involving ca. 7·10³ m³, that happened on February 1995 at Claix, the French Alps, is analysed here. The talus shows a proximal depression due to the impact of the debris, then a grooved area with few, mainly sandy silt deposits and a downslope accumulation of coarse debris that reaches up to 3 m in thickness. The material underwent mass movement as demonstrated by the steep distal front, the strong fabric strength and the thrust planes. The greatest part of the deposits consists of a clast-supported to partially openwork debris with angular clasts over a sheared matrix-supported basal layer. The largest blocks, often more than 1 m in length, are concentrated at the surface and the front. The overall sedimentological characteristics are similar to those of the small dry grain flows that occur usually on rockfall talus, except for the abundance of fine-grained particles that results from intense cataclasis during flow. It is suggested that the deposits of such medium-scale rock-avalanches, probably not uncommon in seismic regions, may have been confused in previous studies with other slope mechanisms such as debris flow and rockfall.     

基于地貌特征的青藏高原边缘泥石流沟分类

青藏高原地形急变带受构造运动、极端降水等因素的影响,呈现泥石流高发、群发的特点。对泥石流沟地貌特征的科学分类有利于探索泥石流发生机制、确定防治对策,对山区防灾减灾和生态修复具有重要意义。本文以青藏高原边缘7个泥石流高发流域为研究对象,开展地貌测量和统计分析。通过非度量多维尺度分析,将泥石流沟分为3种类型：I型是基岩下切区暴雨型泥石流;II型是基岩下切区冰川融水型泥石流;III型是沉积盆地下切区暴雨型泥石流。通过Kruskal-Wallis检验进一步分析3类泥石流沟地貌差异性,从地质、地貌与气候等方面探讨了3类泥石流沟的松散物来源与水沙输移特性。在气候变暖的影响下,II型泥石流的活跃性将增大;随着极端降雨频率的增加,I型和III型泥石流活跃性也将增加。     

北京山区泥石流的分类与类型

采用科学性、实用性和简明易行性的泥石流分类原则，制定出北京山区泥石流的分类指标，从7个方面对已判定出的705条泥石流进行分类。结果如下：1．按泥石流发育的地貌形态分类，有河谷型泥石流57条，沟谷型534条，山坡型114条(处)；2．按泥石流的暴发规模分类，有大规模泥石流51条，中等规模164条，小规模490条(处)；3．按泥石流的流体性质分类，有粘性泥石流136条，稀性泥石流30条，过渡性泥石流539条；4．按泥石流的发育阶段分类，有发展期泥石流296条，活跃期343条，衰退期66条；5．按泥石流的危害程度分类，有危害严重的泥石流117条，较严重的255条，中等的161条，轻微的172条；6．按泥石流的活动频率分类，有中频率的泥石流539条，低频率的166条；7．按泥石流形成与人类活动的关系分类，有人为泥石流36条，自然泥石流669条。     

GIS支持下的东川区泥石流危险度区划

在建立东川区泥石流信息系统的基础上,根据泥石流形成原因,初步选择面积、相对切割度、主沟沟床比降、相对高差、主沟长度、圆状率作为评价指标,利用东川区21条典型泥石流沟的数据,通过主成分分析,选择出面积、圆状率、相对高差三个指标,由主成分载荷得到危险度评价公式,在ARC／INFO和ARCVIEW软件的支持下,把东川区划分为60个评价单元,计算出各个单元内的危险度总分值,依据分值划分为四个级别,重度危险区、危险区、轻度危险区和基本无危险区,最后根据泥石流危险度区划原则,得到东川区泥石流危险度区划图。