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1.
为探寻喀斯特峰丛节齿藓类（Arthrodontae mosses）的生态分布规律及环境因子的影响,选择贵阳市思雅河3座典型喀斯特峰丛为研究对象,利用藓类综合优势比、Sorenson相似性指数及RDA对节齿藓类的生态分布及环境因子影响进行分析。结果表明:3座喀斯特峰丛上共发现节齿藓类植物11科、26属、74种,其中顶蒴单齿藓26种,顶蒴双齿藓21种,侧蒴双齿藓27种。Ⅰ号峰丛以侧蒴双齿藓为主,综合优势比为100%,Ⅱ号、Ⅲ号峰丛则以顶蒴单齿藓为主,综合优势比分别为81.80%、69.75%。节齿藓类在喀斯特峰丛上的分布在坡底以侧蒴双齿藓为主,其综合优势比为97.06%,坡中、坡顶以顶蒴单齿藓为主,其综合优势比分别为86.23%、90.76%。坡中和坡顶的顶蒴单齿藓物种相似性指数最高,为27.91%;坡中和坡顶的侧蒴双齿藓物种相似性指数最低,为11.63%。光照强度和环境温度是影响顶蒴单齿藓类分布的主要因子,侧蒴双齿藓类的分布则主要受到相对湿度的强烈影响;而顶蒴双齿藓类的分布主要受海拔影响。 相似文献
2.
汶川八级地震触发何家沟碎屑流滑坡基本特征及形成机理 总被引：1，自引：0，他引：1
汶川地震造成大量次生斜坡地质灾害,包含崩塌、滑坡及泥石流等灾种,其中以滑坡分布最为广泛、破坏力最强,且多以高速碎屑流为表现形式,何家沟滑坡即是其中典型例证。滑坡距发震断裂——映秀-北川南枝断裂不足5km,震前斜坡为双向临空的单薄山脊,其走向与断裂走向小角度相交,岩层走向与坡面斜交,中风化基岩结合紧密,结构面延伸性较好,强风化基岩较破碎,浅表部残坡积物较为松散。调查分析表明：残坡积物与强风化基岩是碎屑流滑坡的物质基础;中风化基岩面构成碎屑流滑坡滑床;斜坡临空面是滑坡产生的地形条件;高强度、长历时强震是导致滑坡产生的根本因素。滑坡的形成经历以下4个阶段：强震导致坡体表层残坡积物与强风化基岩松弛和解体;在强震作用下滑体从高位整体下错;松散物质沿中风化基岩面溃滑形成碎屑流和碎屑流堆积阶段。碎屑流产生后,受地形限制,停积于沟床内,在随后的“9．24”特大暴雨过程中进一步转化为泥石流次生灾害。 相似文献
3.
某水电站坝前堆积体稳定性的三维数值模拟分析 总被引：13，自引：0，他引：13
某水电站坝前堆积体边坡的稳定性关系到该大坝的建设与运营。野外工作发现,它是深切冲沟型崩塌式堆积体,由下伏基岩和松散的堆积物组成。在1 360~1 450 m高程之间堆积体有一个较为明显的收口转向特征,这有利于增加其稳定性。在野外工作的基础上,采用目前较为通用的两种三维有限元软件(3D-Sigma和3D-Flac)对其稳定性进行数值模拟研究。结果表明：（1）堆积体的应力场主要表现为以自重应力场为主,其应力分布主要受岩性控制;（2）堆积体的潜在滑动面为堆积体与其下伏基岩接触部位的一定范围内;（3）堆积体的位移表现为向坡外(临空面方向)滑移,且中前缘的位移量相对较大;（4）堆积体前缘的收口效应改善了其应力状态,增加了稳定性;（5）堆积体的整体稳定性较好,在1 472~1 610 m高程之间的堆积体有可能发生局部的中浅层破坏。 相似文献
4.
汶川－马尔康高速公路（简称汶马高速）沿线发育大量的千枚岩堆积体,施工开挖形成的千枚岩堆积体边坡的稳定性显著影响着该公路施工及运营安全。以往对千枚岩堆积体的研究多将其视为均质碎块石土边坡,较少关注其特有的结构特征——千枚岩岩块的定向性,导致工程实践中边坡的失稳破坏。千枚岩为片理构造的变质岩,岩块具有显著的扁平化特征,沿坡运动后以一定的方向性停积。野外调研表明,堆积体中扁平状岩块的倾向与边坡坡面倾向相近,将此称之为岩块定向性,并认为该定向性是影响堆积体边坡稳定性的重要因素。以汶马高速千枚岩堆积体为研究对象,设计物理模型试验研究千枚岩堆积体岩块定向性特征及其影响因素。在此基础上开展考虑岩块定向特征的堆积体大型直接剪切试验,探索岩块定向性对千枚岩堆积体边坡稳定性的影响。结果表明,坡度及堆积体中细颗粒含量对岩块定向性有显著影响,坡度为20°～30°时,定向性最明显,且随细颗粒的含量增大而增大;边坡稳定性分析时的潜在滑面抗剪强度由于岩块定向性而显著降低。 相似文献
5.
紫坪铺水利枢纽工程左岸坝前堆积体治理措施评价 总被引：1，自引：0，他引：1
紫坪铺水利枢纽工程左岸坝前堆积体在水库运行期间极可能最先发生局部沿腰部失稳模式,其治理措施应考虑从前缘堆载反压措施人手,并结合相应的排水措施。治理后堆积体的稳定性大大提高,但在水库运行期间仍应尽量避免库水位变幅较大或调节速率过高,同时应加强地震监测和变形监测,以保障堆积体和大坝的安全稳定。 相似文献
6.
Samples of stream sediments and aquatic mosses were collected from nine sites across several mineralized zones at the southeasternmost extension of the Idaho Cobalt Belt. Because the steepness of the terrain and the attendant high flow rate of the streams made it difficult to obtain adequate sediment samples, mosses were considered as an alternative sampling medium. The results not only showed that the Cu and Co content of the mosses correlated almost perfectly with that of the sediments, but that the contrast between samples taken from mineralized and background areas was greater in mosses, especially for Co. Maximum concentrations of 35,000 μg/g Cu and 2000 μg/g Co were observed in the ash of mosses, compared to maximum concentrations of 1700 μg/g and 320 μg/g, respectively, in the associated sediments. Species identification was considered unimportant, which should dispel some reluctance to use mosses in mineral exploration. 相似文献
7.
沟系土壤测量在贵州大厂矿田普晴锑金矿区地质找矿中的应用 总被引：1，自引：0，他引：1
通过对贵州晴隆县大厂矿田西部普晴锑金矿区的成矿地质特征及自然景现条件的调查研究.认为该区为中高山湿润剥蚀景观区,适合开展沟系土壤测量.通过方法实验,提出了沟系土壤测量的关键技术指标,即:采样介质为沟系两侧残坡积物、冲刷物,采样层位为B层;采样密度为30-50个/km2,样品加工粒度为20目.利用STASTIC软件对测试数据的常用对数值进行R型因子分析,得到4个F因子组合,圈定了3个异常区.根据对元素异常下限值及F因子组合异常的评价分析,筛选出3个Sb、Au找矿靶区,可作为下一步地质找矿的依据. 相似文献
8.
The morphology and surface ages of talus-derived rock glaciers are investigated to establish the timing of rock glacier formation in the central Southern Alps. Samples of rock weathering rinds show that all rock glaciers studied were formed during the Neoglacial period, but differences exist between sites in the number of new rock glacier lobes formed by Holocene climatic fluctuations. A qualitative conceptual model is proposed to explain rock glacier formation in terms of two thresholds. An external threshold relates to the presence of a cool climate capable of allowing internal ice to form within talus slopes. An internal threshold relates to the presence of sufficiently thick talus at a site to generate a shear stress capable of overcoming internal friction within the talus/ice mass. The model produces a non-steady-state response to explain why unmodified talus, single-lobed and double-lobed rock glaciers developed at adjacent sites under the same climatic regime. Individual landforms have different sensitivities to formation, which depend partly on the previous history of talus accumulation and rock glacier activity at a site. The model demonstrates how successive cool climate periods may be fully represented by rock glacier lobes at sensitive sites but under-represented at insensitive sites. Sensitivity (and therefore climatic representativeness) is favoured by high rates of debris supply. By implication, the timing of formation of rock glacier lobes in regions of prolonged cool climate and low debris production is less likely to correspond to the timing of climatic cooling and more likely to follow the ‘rules’ of deterministic chaos. 相似文献
9.
Geophysical investigations of large landslides in the Carnic Region of southern Austria 总被引：7，自引：0，他引：7
Hermann J. Mauritsch Wolgang Seiberl Ranier Arndt Alexander R mer Klaus Schneiderbauer Gernot P. Sendlhofer 《Engineering Geology》2000,56(3-4):373-388
The area under investigation for the past two decades is in the vicinity of the Gailtal lineament, which is the most dominant tectonic feature of the eastern Alps of southern Austria. An area of about 8 km2 is in a state of constant instability, as documented by movement of road tracks of several centimetres per year. Geotechnical and surveying techniques have been used to measure these movements in the past but without solving the problem of the mechanism of these failure processes. Geophysical methods (seismic refraction, geoelectrics, and electromagnetics) were applied in order to determine the validity of one of the discussed movement models. In-situ velocity measurements were used to identify different lithologies beneath surficial talus deposits. The thickness of these talus deposits, of about 4–30 m, found by seismic refraction clearly demonstrates that huge ‘blocks’ (i.e. more or less undisturbed lithologic units) within the talus/debris are in close contact with the basement. This basement, which shows lower seismic velocities in different parts combined with low electric resistivities, is obviously strongly disturbed by different failure surfaces. The different gliding velocity of the blocks and the talus/debris deposits leads to a geological model in which huge rock blocks move slowly in relation to the disintegrating basement, whereas the talus/debris deposits move over the surface of these blocks at a higher velocity. The interpretation of these landslide studies is not a straightforward analysis. It is a complex problem with a complex solution, including all information from geotechnical, geophysical, and surveying investigations. 相似文献
10.
Rockfalls that trigger scree‐laden snow avalanches are common in mountain ranges, but the resulting avalanche development and its role in understanding the sedimentology of scree slopes are rarely described in detail. On Riepenwand (2774 m above sea‐level, Kalkkögel range, Alps), on 6 May 2011 a 5800 m3 rockfall of dolostone detached from the flank of a gorge in the upper part of the mountain. After first collapsing into the gorge, the fragmented rock mass fell down freely for 150 m onto a talus covered by coarse‐granular snow. Rockfall impact triggered a medium‐scale avalanche that developed: (i) a lower layer A of entrained, pure snow; and (ii) an upper layer B of clay‐sized to boulder‐sized fragments mixed with snow. This ‘two‐layer scree/snow avalanche’ halted in the distal slope segment of the talus. Boulders within layer B mainly came to rest in the distal part of the avalanche deposit. Fragments smaller than cobble‐size grade did not show obvious downslope segregation. With snowmelt, the rockfall fragments dispersed in layer B were concentrated to a clast‐supported veneer that was draped over the older talus surface upon slower melting of avalanche layer A. In the grain‐size fraction ≤16 mm, a mean of 5 wt% matrix (silt‐sized to clay‐sized grains) of the rockfall‐derived scree of layer B is similar to a mean matrix content of 7 wt% within stratified talus slopes of the Kalkkögel range. This similarity suggests that a major share of matrix – widespread in stratified talus – stems from rockfalls. The characteristics of the scree veneer as melt‐lag of a scree‐laden snow avalanche will be blurred with time. Fossil talus successions may contain a substantial proportion of scree carried down by snow avalanches. The formation of a distinct sedimentary facies of snow avalanche‐deposited scree is impeded by processes of redeposition and deposit modification on talus. 相似文献
11.
沿台地边缘斜坡沉积的古代碳酸盐再沉积物是最近十年来才引起沉积学者广泛注意的一种深水碳酸盐类型,包括碳酸盐重力流,重力滑动(滑塌)沉积及塌磊裙。重力流及由于重力作用引起的沉积物与浅水碳酸盐或深水原地碳酸盐沉积相比,有很大的差异。它们的主要岩石类型是异地碳酸盐,为一套在重力作用下顺坡而下流动的碳酸盐沉积物。前礁塌磊是台地边缘礁坠落到陡崖下的礁块堆积,也称为礁崖塌积。 相似文献
12.
贵州普定喀斯特受损生态系统石生藓类植物区系及物种多样性研究 总被引：2，自引：2，他引：0
以贵州普定县喀斯特受损生态系统石生藓类为研究对象,对其区系及多样性进行研究。结果显示,该区共有石生藓类植物8科24属54种,其中丛藓科和灰藓科为优势科,扭口藓属、真藓属、曲柄藓属、拟合睫藓属和细喙藓属为优势属;物种多样性丰富度指数在0.471～－0.297之间变化,均匀度指数在0.617～0.566之间不明显变化,受损区域藓类植物多度明显低于水土保持长期观测样方（E）;有丛集型（53.8%）、交织型（26.9%）、平铺型（11.5%）和悬垂型（7.7%）4种生活型,主成分分析（PCA）显示不同样方中的苔藓植物生态分布存在差异性。 相似文献
13.
基于元胞自动机模型的堆积体动力学参数研究 总被引：1，自引：0，他引：1
堆积体是一种典型的二元介质,由软弱的基质土与坚硬的碎、块石构成。利用元胞自动机模型对随机离散单元进行演化,模拟堆积体的分布结构、“聚团”特征;利用弹性应力波传播原理计算波的等效速度,研究了堆积体内介质分布、软硬程度对动力学参数的影响规律。研究发现,堆积体内的波速由基质与充填物共同决定,基质材料越弱,地震波传播速度越慢,二者呈对数变化;堆积体内碎石含量越高,则波速越快,波速与充填碎石块含量呈对数关系增长,而振幅系数与碎石含量关系不大,主要取决于碎块石的分布结构;由于堆积体介质密度不均,导致堆积体内波传播速度与入射波频率密切相关,高频波速度快、低频波速度慢,横波速度与入射波频率成指数递增关系。研究表明,采用基于元胞自动机模型研究动变形参数,可以更好地反映出堆积体的波动力学性能,是一种获得复杂介质动参数的重要方法,可以弥补室内及现场试验的不足。 相似文献
14.
对河北省围场地区广发永剖面藓类植物薄网藓Leptodictyum riparium、似叶镰刀藓Drepanocladus trichophyllus和多姿柳叶藓Amblystegium varium的古地理及其对应的现代植物地理分布研究显示,这些植物最早出现于早中新世的围场地区,可能起源于该时期的古北大陆,东亚为起源中心。之后向东通过白令陆桥扩散到北美,向西沿欧亚大陆扩散至欧洲西部,至全新世时主要分布在北半球。全新世后,薄网藓与多姿柳叶藓进一步向南扩散,分别由北美及亚洲东部扩散到南美洲及澳大利亚地区,逐步形成现在的分布格局;毛叶镰刀藓则在更新世就已形成与现代相近的分布格局。该研究确立了3种藓类植物的地理起源、地史分布及迁移路线。 相似文献
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16.
Twenty-seven moss specimens collected from the Guangfayong section （Early Miocene,22.1 Ma） of the Weichang District,North China were investigated in the present study.Based on the morphological and anatomical features of gametophytes,all specimens were found to belong to three species：Leptodictyum riparium,Drepanocladus subtrichophyllus sp.nov.,and Amblystegium varium,all of which belong to the family Amblystegiaceae.The microhabitats and living environments of fossil mosses were also investigated based on comparison with living mosses.The results suggest that these mosses grew primarily at the edges of rivers,streams,and lakes and favored being submerged in streams or lakes in the Weichang District in the Early Miocene. 相似文献
17.
鄂尔多斯盆地中南部三叠系延长组8油层组成岩作用及其对储层物性的控制 总被引：1，自引：0，他引：1
鄂尔多斯盆地中南部延长组8油层组主要成岩作用包括压实作用、石英次生加大、自生绿泥石膜生长、次生高岭石化、连晶方解石交代、长石溶蚀。根据铸体薄片,碳氧同位素分析,确定了各种主要成岩产物的空间分布和成因,分析了成岩产物分布与现今总面孔率的关系,从而确定8油层组的物性主要受石英次生加大、连晶方解石、长石溶孔、剩余原生孔隙分布的控制。石英次生加大和连晶方解石发育的地方,储层物性差;具自生绿泥石膜的剩余原生孔隙和长石溶孔发育的地方,储层物性好。 相似文献
18.
The polymorphous transition that occurs during the process of metasomatic replacement was observed in the experiment on the retgersite paramorph formation after nickelhexahydrite crystals. This process runs through a solution film formed on the primary crystal surface and then penetrated into the crystal along with the replacement front. One or several secondary mineral grains have ingrown into a comparatively perfect crystal up to the complete replacement; these grains are randomly oriented with regard to the crystal. A finegrained mass replaces the imperfect crystals. An aggregate of mineral grains incorporated into the fine-grained mass is an intermediate case. Single-crystal pseudomorphs have been synthesized for the first time as products of the nonisomorphic interaction. Conditions of the nickelhexahydrite metastable equilibrium and the retgersite stable equilibrium are closely related and determine the structural features of the replacement reactions for these two compounds. A relatively low supersaturation with retgersite in the vicinity of the eutonic point resulted in the nucleation and growth of secondary single crystals. A deviation from the eutonic point gives rise to the increasing supersaturation and mass precipitation of the secondary phase. 相似文献
19.
Rock glaciers, protalus ramparts and related phenomena, Rondane, Norway: a continuum of large-scale talus-derived landforms 总被引：1，自引：0，他引：1
RICHARD A. SHAKESBY ALASTAIR G. DAWSON JOHN A. MATTHEWS 《Boreas: An International Journal of Quaternary Research》1987,16(3):305-317
Talus-derived landforms from Rondanc National Park, southern Norway, are described and classified as protalus ramparts, valley-floor and valley-side talus-foot rock glaciers, and a 'push-deformation' moraine. A morphological and developmental continuum of talus and derivative large-scale landforrns is proposed. with simple talus slopes at one end and more complex ridge, lobe and bench forms at the other. The various types of feature probably develop from simple talus slopes via separate developmental routes, rather than as a linear sequence. Lichen size and Schmidt hammer R-values were used to indicate the relative ages of the features. Although all are thought to have originated during the early Holocene, they differ in the presence or extent of recent activity. Hence an age and activity continuum is also suggested, the recency of activity increasing in the direction protalus rampart → rock glacier →'push-deformation' moraine. 相似文献