黄河口水下斜坡波致圆弧振荡剪切破坏分析   总被引：2，自引：2，他引：0  

常方强  贾永刚 《海洋学报》2010,32(5):175-179

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The System Analysis and Reliability Evaluation of Rock Slopes   总被引：1，自引：0，他引：1  

Luo Guoyu  Yan ChanghongDepartment of Earth Sciences  Nanjing University  Nanjing  Jiangsu Fei Zhenbi 《《地质学报》英文版》1994,68(4)

The principal of preferred plane analysis is a new research view and model of rock slope engineering geology. It advocates that the rock slope stability, boundary conditions and failure model are controlled by preferred planes. Therefore, the problem of slope stability evaluation can be converted into the search for preferred planes and determination of preferred separating bodies. The organic combination of the deterministic model and the indeterministic model can be realized by applying the systems engineering principle and the research model and method of reliability analysis in the quantitative evaluation and prediction of rock slope stability. Finally, the paper presents the case studies of slopes of the Yangtze Gorge Project and the Ma'anshan openpit mine.  相似文献   

不连续岩体变形破坏过程中AE的空间演化与意义     

曾正文  马瑾 《工程地质学报》1994,2(1):46-53

通过一些典型节理化岩体模型变形破坏过程中的AE事件的定位分析和破裂面形态的研究,探讨了不连续岩体变形破坏过程的空间演化特征。结果表明:单节理岩体变形破坏的空间动态特征受节理角控制,随着节理角从小变大,岩体的变形破坏方式从AE在局部集中的突发式失稳向AE弥漫于整个节理层面的类似渐进式的破坏形式发展；失稳破裂面从简单的整体状岩-膏界面变成形态复杂的层内复合破裂面；复杂节理岩体的变形破坏受一条（组）主导构造控制,强AE事件集中发生在不连续构造交汇部位,在包含多条主构造的岩体模型中最终失稳破裂面只与最后阶段AE的位置一致。  相似文献   

早期左心功能不全的一种CT征象——胸膜下区宽带状影的研究     

孙伯章  蒋国民  黄晓英  刘赓年 《CT理论与应用研究》1993,(2)

早期左心功能不全的诊断目前仍较困难,作者在部分病人的胸部CT 图象上发现一种胸膜下区宽带状影与早期左心功能不全有密切关系,表现为两肺背部呈带状的模糊影象,这种胸膜下宽带状影对诊断早期左心功能不全,尤其是舒张功能有一定的临床意义。  相似文献   

40Ar/39Ar laser probe evidence concerning the age and associated hazards of the Lake Nyos Maar,Cameroon     

G. Brent Dalrymple  John P. Lockwood 《Natural Hazards》1990,3(4):373-378

The waters of Lake Nyos are impounded by a fragile natural dam composed of pyroclastic rocks ejected during the formation of the lake crater (maar). Lateral erosion of this dam has reduced its width from over 500 m to only 45 m. Published whole-rock K-Ar ages of about 100 ka on juvenile basalt from the dam suggests that erosion has been slow and that the dam poses no imminent threat. New apparent ⁴⁰Ar/³⁹Ar ages of 1.4 to 232 Ma on xenocrystic K-feldspar contained in the basalt show that the xenocrysts, whose source is the 528-Ma crystalline basement, are carriers of inherited radiogenic ⁴⁰Ar and would cause the whole-rock K-Ar ages to be too old. The best estimate for the age of the maar is provided by a ¹⁴C age of 400 ± 100 yr BP on charcoal from the base of the dam. This young age indicates that the dam is eroding at a relatively rapid rate; its failure, perhaps within a few decades, would result in a major flood and imperil thousands of people living downstream in Cameroon and eastern Nigeria.  相似文献   

Reliability level III method in design of square pillar resting on weak floor stratum     

W. M. Pytel 《Geotechnical and Geological Engineering》1990,8(2):149-162

Summary Current methods of design of pillars resting on weak floor strata involve only a deterministic, conventional safety factor calculation, based on material parameters treated as the mean values taken from observations. In a case where high parameters variability occurs, these methods may lead to fatal design errors resulting in excessive pillar settlement and roof falls. Therefore, to include the influence of parameters quality, the new approach based on reliability level III method was developed. Consideration was given to the identification of the system parameters importance, and to density function for the safety factor treated as a random variable. Design procedure involving floor probability of failure was illustrated by numerical examples.  相似文献   

Time-dependent behaviour of the rock mass   总被引：1，自引：0，他引：1  

E. Z. Lajtai 《Geotechnical and Geological Engineering》1991,9(2):109-124

Summary The strength of intact rock and the rock mass is time-dependent. For intact rock experimental verification is available, for the rock mass the scale of time-dependence is a matter of judgement. Rock mass classifications do however emphasize the effect of time on tunnel stability. This paper examines the source of time-dependence in rocks and the rock mass and suggests a technique for estimating the long term strength. The long term strength of the rock mass is controlled by the time-dependent weakening of intact rock. Frictional resistance, a major source of rock mass strength, increases rather than decreases with time. Lifetime estimation for rocks can be accomplished phenomenologically or mechanistically. The first is a statistical process of wide applicability, the second is more restrictive in usage as its applies only to materials that suffer time-dependent strain (creep). Although the mechanistic route is more appealing, it has a major drawback as it concentrates on steady state creep. There is no strong evidence for steady state creep in rocks. The technique for long term prediction is developed through the analysis of the failure rate under constant load. The failure rate for a given load and environment is established from the frequency distribution of time-to-failure data as measured in static fatigue tests. As expected, the failure rate is strongly affected by both the loading and the environmental condition. The influence, however, is systematic and predictable.  相似文献   

Effects of soil moisture dynamics on slope failure at Hyrum Reservior,Utah     

Michael P. O'Neill  Jeffrey J. McDonnell 《地球表面变化过程与地形》1995,20(3):243-253

Field observations of shoreline conditions at Hyrum Reservoir, Utah, were conducted during the summers of 1991 to 1993. A process of bluff retreat is described for a multiple-layered bluff environment of sand and clay layers. Failure is initiated by wetting and drying of clay sediments, which produces horizontal cracks within bluff material. These cracks appear to penetrate to a depth of approximately 100-150 mm before initiating vertical cracking in the sediments. The vertical cracks are propagated by continued drying of the surface sediment, ultimately leading to failure of the bluff material. The physical dimensions of sediment blocks succumbing to this mechanism range from a few hundred millimetres up to 3 m on a side, with a depth of approximately 100-150 mm. The mechanism described here appears to operate optimally when the supply of subsurface moisture is abundant and nearly continuous throughout the spring and early summer. Reservoir draw-down, large capillary fringe effects in the bluff and periodic wetting from upslope undrained hollows are the dominant moisture controls at this site. Moisture delivery to the face is strongly influenced by anisotropy of saturated hydraulic conductivity in the alternating clay and sand layers and related differences in sediment texture.  相似文献   

结构模糊随机可靠度的实用计算方法   总被引：15，自引：0，他引：15  

王光远  刘玉彬 《地震工程与工程振动》1995,15(3):38-46

本文以模糊随机变量为基本变量，定义了结构的模糊随机功能函数，分析了结构有效状态与失效状态之间的模糊性，建立了结构的模糊随机极限状态方程。利用序关系给出单失效模式结构的模糊安全准则，讨论了ａ－约束水平条件下单失效模式结构的失效概率、可靠度及可靠指标，进而得出结构的模糊随机失效概率、模糊随机可靠度及模糊可靠指标等。本文给出的具体计算方法和目前设计规范中彩的方法是相对应的。  相似文献   

三峡水库运行条件下金乐滑坡稳定性评价   总被引：1，自引：2，他引：1  

胡新丽  王亮清 《地球科学》2007,32(3):403-408

三峡水库运行后,水库水位每年将在145m～162m～175m间波动,库水位的浸泡软化作用及水位升降引起的地下水位的波动将会降低库岸岩土体的抗剪强度,影响已有滑坡的稳定性.因此,在实际水库运行条件下滑坡的稳定性是目前迫切需要研究的重要课题.针对库区大型复杂滑坡——金乐滑坡,分析了该滑坡的工程地质条件和形成机制;建立了二维有限元计算模型并选择合理的岩土力学参数;利用英国帝国理工学院ICFEP有限元软件,依据水库实际运行曲线,在一年时间内分7种不同的模拟状态进行了模拟.结果表明:(1)金乐滑坡在天然状态下处于稳定状态;(2)库水位上升状态下,滑坡前缘稳定性较相应的稳定水位状态较好;(3)水位下降状态,滑坡前缘将出现破坏,特别是162m下降至145m时,滑坡前缘出现破坏,存在中前部渐进破坏的可能;(4)金乐滑坡变形破坏形式为牵引渐进式,在一个水位波动周期内不存在整体滑移的危险.建议对滑坡前缘进行治理.  相似文献