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地震作用下节理岩质边坡稳定性影响因素研究 总被引：1，自引：0，他引：1
汶川地震灾害调查表明,在基岩山区地震滑塌主要发育在局部强度相对较大、节理较发育的厚层或块状岩体中.以岩石中含两组节理的岩质边坡为例,输入实际的地震记录,采用离散单元法进行数值模拟,分别探讨坡高、地震烈度、坡角及节理倾角组合对节理岩质边坡稳定性的影响.结果表明:地震作用下坡体中质点的加速度、速度具有高程放大效应;节理岩质边坡稳定性随着坡高、坡角和地震烈度的增加而降低;两组节理不同组合的岩质边坡,其稳定性变化较为复杂,受节理倾角与坡角的关系、节理的倾向、两组节理之间夹角等因素的影响.节理岩质边坡在地震作用下是受拉区逐渐向受剪区扩展而最终导致边坡失稳破坏,是受拉和受剪的复合破坏.上述初步结论为评价山区节理较发育的岩质边坡在地震作用下的稳定性提供一定的依据. 相似文献
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边坡破坏是累积性过程，从变形到破坏的过程中会产生永久位移，如果永久位移过大，极有可能产生滑坡。因此根据不同工况下采集到的位移数据，分析地震作用下反倾层状岩质边坡在不同内摩擦角下的破坏特征。利用二维数值流形法（NMM），以青藏高原金沙江流域西藏昌都地区芒康县索多西乡贡扎倾倒滑坡为研究对象，依据实地考察数据及室内力学试验得到的物理力学参数，建立数值计算模型，模拟地震作用下反倾层状岩质边坡倾倒破坏过程，并在边坡上布置3组监测点获取位移数据。模拟结果表明:随着内摩擦角的增大，边坡坡体从开始破坏到新的平衡状态和达到最大位移所需的时间越短，同时，滑动块体最大水平位移逐渐减小；内摩擦角＜40°时，坡体在前15 s呈整体移动趋势，大部分岩块产生整体滑移，靠近坡顶处的岩块发生轻微转动，推动前面的岩块加速滑动，呈倾倒-滑移模式；内摩擦角＞40°时，靠近坡顶的岩块首先产生滑动，并转动驱使前面的岩块，推动坡脚处岩块产生滑动，最终上部岩块达到新的平衡，呈渐进式倾倒破坏，产生整体性破坏的可能性较小。 相似文献
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Newmark永久位移是评价边坡在地震时稳定性的一个重要指标,近年来广泛应用于地震边坡危险性评价中。传统Newmark永久位移法在计算临界加速度时假定其为常数,未考虑滑动面上抗剪强度参数的变化,过低估计了边坡的永久位移。为了解决这一问题,本文从岩土结构理论获得思路,详细分析滑块底面抗剪强度参数在地震中的变化过程,以边坡震动过程中黏聚力逐步丧失为基本思路,在黏聚力符合一定概率分布的基础上,提出了一种利用蒙特卡罗法模拟其动态减小过程从而实现临界加速度动态变化的计算方法。经过算例计算,黏聚力和临界加速度体现了地震过程中边坡滑块黏聚力和临界加速度的动态变化,位移大小符合地震边坡实际位移的常规数值。本文提出的蒙特卡罗法实现动态黏聚力和动态临界加速度的计算过程与地震时程相对应,不仅在一定程度上解决了抗剪强度参数的动态变化问题,还解决了传统Newmark位移计算中永久位移比实际位移偏小的问题。 相似文献
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基于动态临界加速度计算地震边坡永久位移的方法应用了边坡分布的不均匀性，不均匀分布程度影响着永久位移计算结果。研究Newmark滑块底部或潜在滑动面上抗剪强度参数的分布特征，有利于了解地震过程中临界加速度的分布和变化过程，为地震边坡永久位移计算参数选取提供依据。通过计算发现：边坡土体标准差的线性关系比较微弱，在缺乏实验数据时，仅可参考使用；黏聚力随机数个数达到200时所计算的永久位移数值不再有波动；黏聚力无论设置为正态分布还是对数正态分布均不影响永久位移计算结果；黏聚力标准差的数值大小对永久位移的大小和离散性影响很大。在地震边坡计算时，尽量将其设置为符合正态分布；尽量根据实测数据设定黏聚力标准差，若缺乏实测资料，可参考两者的线性关系并结合经验进行标准差设定。 相似文献
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在分析加筋土边坡稳定性时,将加筋材料的作用视为施加于滑面上的等效力,建立了满足力平衡的加筋土边坡安全系数的计算格式;将边坡临界滑动场数值模拟方法进行推广,提出了基于力平衡的加筋土边坡临界滑动场计算方法,可以得到形状任意的临界滑动面及边坡最小安全系数。通过算例,比较加筋前后临界滑动面和安全系数的变化,并探讨了加筋水平间距、强度、长度对加筋土边坡稳定性的影响。 相似文献
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《世界地震工程》2015,(4)
针对汶川地震区边坡,介绍了边坡的工程背景和滑坡现状,研究了地震和降水耦合条件作用对边坡稳定性的影响。探索了加筋挡土墙在地震区边坡应用的可能性,使用基于极限平衡法的SLIDE软件进行不同工况条件下边坡稳定性的计算,分析了不同的加筋方案对加筋挡土墙性能的影响。研究表明:在地震作用下,边坡土体原有的结构体系遭到破坏,土体变得较松散,甚至产生张拉裂缝,为雨水的渗入提供了通道,对边坡的稳定性产生不利影响。数值模拟计算得出,边坡在排水条件下基本处于极限平衡状态,最危险滑动面位于边坡下部,但滑动区域相比饱水条件下明显减小,危险滑动面面积也随之减小,而合理的削坡、建立有效的坡表排水系统和加筋挡土墙加固可较大程度的提高坡体稳定性。 相似文献
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《地震工程与工程振动》2016,(4)
依据量纲分析法和相似定律,制作了顺层和反倾向岩质隧道边坡的物理模型,采用单向振动试验台施加动力荷载,利用摄像机记录模型边坡的变形破坏过程、加速度传感器采集边坡各部位加速度分布情况。试验结果表明:层状岩质边坡的变形破坏是受到结构面控制的,顺层边坡的破坏以剪切滑动破坏为主,而反倾向边坡的破坏以松散体塌落为主;另外,隧道洞口的破坏情况与洞口所处的高程有关,高坡位的隧道洞口在振动力作用下的破坏较为严重,而低坡位隧道洞口则容易被滑塌体堵塞洞口;模型边坡存在明显的"高程效应"和"趋表效应",不同结构面组合形式的边坡其加速度放大效应具有相似规律。 相似文献
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《世界地震工程》2015,(1)
斜坡的坡体结构是控制斜坡变形破坏模式、影响斜坡动力特性的重要因素。为了进一步了解"坡体结构面如何影响边坡地震动力响应规律"这一问题,对均质斜坡(无结构面)和水平层状岩质斜坡(含水平结构面)两种类型的岩质斜坡进行了大型振动台试验研究,并着重对比分析了有无结构面对岩质斜坡峰值加速度动力响应规律的影响。研究结果表明:水平层状斜坡坡表和坡内加速度动力响应基本上都大于均质斜坡,即水平层状岩质斜坡存在层面放大作用,但水平结构面对斜坡加速度动力响应放大作用的程度与地震波类型、频率、振动强度和激振方向有关,总的来说,水平层面对Z向地震波的放大作用大于对X向地震波;在本试验研究中,频率仅影响层面放大系数量值的变化,而地震波类型及其振动强度和激振方向则对其分布形式和量值均有显著影响。 相似文献
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2014年8月3日鲁甸MS6.5地震触发了大量的滑坡崩塌,其中,位于鲁甸县李家山村和巧家县红石岩村交界处的牛栏江干流北岸的红石岩滑坡规模巨大,与此处位于左岸的红石岩古滑坡体的前缘部分一起堵塞了牛栏江而形成高达120m、体积达1 200×104m3的大型堰塞体。通过震后开展的野外实地调查,获得了红石岩滑坡发生处的地形地貌、地质构造、岩体结构及物质组成等资料。以这些第一手资料为基础,构建了红石岩滑坡的边坡模型,并应用边坡稳定性分析软件Geo Studio中Slope/W模块分别计算了红石岩滑坡体震前坡体安全系数和地震作用下的坡体安全系数。结果表明,红石岩滑坡体发生处的坡体安全系数在地震前为1.450,处于相对稳定状态,而鲁甸地震的地震动作用则使坡体的安全系数降低至0.962,直接导致红石岩坡体的失稳。文中进一步讨论了坡体滑动面的存在与否对坡体稳定性的影响:安全系数计算的结果表明,在中强地震作用下,先存滑动面的存在是导致大型滑坡形成的重要条件;对于高陡岩质边坡,如果没有先存滑动面,只可能形成浅表性滑坡。 相似文献
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《国际泥沙研究》2014,(4)
正Director:Shangfu Kuang,China Vice-directors:Chunhong Hu,China Duihu Ning,China Guangquan Liu,China The International Research and Training Center on Erosion and Sedimentation(IRTCES)was jointly set up by the Government of China and UNESCO on July 21,1984.It aims at the promotion of international exchange of knowledge and cooperation in the studies of erosion and 相似文献
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《中国科学:地球科学(英文版)》2014,(3)
正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research. 相似文献
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Richard D. Hey 《地球表面变化过程与地形》1979,4(1):59-72
Feedback mechanisms, which operate upstream through drawdown and backwater effects and downstream through sediment discharge are responsible for channel evolution. By combining these mechanisms with channel processes it euables a dynamic process-response model to be developed to simulate the initial evolution of straight gravel-bed channels. When erosion commences on a land surface, sediment entrained in the headwater reach by hydraulic action is selectively transported, deposited and reworked. This produces a damped oscillation between degradation and aggradation as the channel and valley respond to spatial and temporal variations in sediment calibre and hydraulic conditions. The initial cut and fill phases are responsible for valley incision and floodplain development while secondary and subsequent activity can produce river terraces. Eventually sediment entrainment in the headwaters declines as slopes are reduced. Subsequent channel evolution is relatively insignificant because it is dependent on local weathering activity producing material that can be transported on declining slopes. Therefore landforms produced during the initial phase of development, when local weathering was non-limiting, dominate the landscape. 相似文献
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Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored. 相似文献
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《水文科学杂志》2013,58(6)
Abstract The western reservoirs represent the principal groundwater system in Morocco. Demographic, industrial and agricultural developments during the last decade have markedly altered groundwater quality. The Mamora coastal aquifer system is among the Atlantic systems which are most heavily threatened by pollution. Agricultural and industrial activities, and rapid urban growth contribute to the pollution of the groundwater. Contamination transport is facilitated by a high permeability of the aquifer formations. In order to assess the actual groundwater quality of the Mamora aquifer and to understand the influence of the factors generating the pollution, an extensive multidisciplinary research programme is in progress, with hydrochemistry and microbiology playing essential roles. The present paper concerns the spatial distribution of physico-chemical parameters in the groundwater, subjected to domestic, industrial and agricultural pollution. Fifty-seven samples were analysed for several parameters (Ca2+, Mg2+, Na+, K+, Cl?, SO4 2?, HCO3 ?, NO3 ?, pH, electrical conductivity and temperature). The microbiological analysis of 143 samples reveals the presence of four kinds of indicator bacteria in the groundwater resources: faecal Streptococci, faecal coliform, Escherichia coli and Clostridium. The physico-chemical results and bacteriological monitoring show that the nitrate and bacteria concentrations exceed the maximum admissible levels, notably around pumping stations in the sectors of Sidi Taibi, Sidi Ahmed Taleb and Aïn Sbaâ. Contamination is generated by uncontrolled anthropogenic activities and accentuated by the high intrinsic vulnerability of the aquifer system. Several parameters appeared to exceed admissibility standards. Measures are recommended to prevent groundwater pollution in the region. 相似文献
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K.-G. Malle 《洁净——土壤、空气、水》1992,20(4):196-204
Zinc in the Environment. In 1990 the world production of zinc ammounted to 7 Mio. metric tons. The main areas of application were: galvanization, alloys like brass and zinc metal. The content in the earth crust varies between 10–300 ppm zinc with a mean of 70 ppm. Uncontaminated surface waters contain less than 10 mg/m3 zinc. Apart from civilization air contains 1–10 ng zinc per m3. These background concentrations are exceeded by orders of magnitude in zinc deposit areas and where anthropogenic influences predominate. Accumulation can occur in sediments and sewage sludge. Molluscs and Algae also accumulate zinc. Zinc is essential for live. With normal food the zinc supply of man is just sufficient. Bioaccumulation of zinc towards man or chronic oversupply of man is not known. Zinc has no teratogenic or mutagenic effects, a suspicion on a carcinogenic effect proved wrong. In stockbreeding and plant cultivation a minimum supply of zinc is necessary. Plants are relatively less sensitive against higher soil contents of zinc. Considering the toxicological and ecotoxicological effects of zinc in the environment, the critical organismens are marine invertebratae like tubifex, daphnia, gammarus and algae. But normally only a minor part of the total zinc contest is biologically available, depending on salt content and pH of the waters. 相似文献