Risk analysis of landslides – A case study     

G. L. Sivakumar Babu  M. D. Mukesh 《Geotechnical and Geological Engineering》2003,21(2):113-127

The effects of uncertainty due to the variability of soil parameters on the risk of landsliding in the Himalayan region are investigated using a random field model combined with slope stability analyses. Effects of spatial variability both in horizontal and vertical directions, number of test samples, variations in piezometric level and the influence of earthquake on the reliability of a typical slope in a slide area are investigated. The results show that the reliability of slopes in the slide area is significantly affected by the coefficients of variation of soil parameters, spatial variations of soil parameters, number of test samples and piezometric variations. The results also show that the assumption of isotropic variations to assess slope reliability isconservative. The results of the study are useful in providing guidelines and pointing to remedial measures in the form of sub-surface drainage to improve slope reliability in the area.  相似文献   

Reliability based risk index for the design of reinforced earth structures   总被引：1，自引：0，他引：1  

Adnan A. Basma  Samer A. Barakat  Maher T. Omar 《Geotechnical and Geological Engineering》2003,21(3):225-242

The design methods currently used for earth reinforcement are mostly based on deterministic properties of both the soil and the construction materials used. Nowadays, however, the general trend is designing at a specific degree of reliability. This is even more true where the raw data such as soil properties exhibit significant variation. Deterministic solutions, in this case, may not suffice. Therefore, this paper will attempt to use probabilistic formulations thereby modifying the existing design procedure of reinforced earth retaining walls to account for uncertainties and variabilities. Through a first order Taylor's series expansion about the mean, the mean and variance of the strip reinforcing components, namely width and length, are derived in terms of the variations in the soil properties. Design charts that enable estimation of both mean and variance are developed to avoid extensive partial differentiation involved in the computations. Using appropriate probability distributions along with the mean and variance, the final design outputs are determined for a selected failure probability by introducing what is refered to as 'risk index'. The results indicate that the risk index increases with an increase in the coefficient of variations and a decrease in failure probability. Furthermore, it is shown that in some cases, depending on the variabilities of the soil properties, the classical design technique produced a relatively high failure probability. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

地下巷道弹性位移反分析各种优化方法的探讨   总被引：16，自引：5，他引：16  

吕爱钟 《岩土力学》1996,17(2):29-34

探讨了６种最优化方法（鲍威尔法、单纯形加速法、阻尼最小二乘法、变尺度法、模式搜索法和变量轮换法）在巷道弹性位移反分析中的应用情况。从参数初始点的选择、收敛速度、收敛精度和可靠性方面评价了这６种无约束最优化方法的优劣。  相似文献   

程裕淇主编《中国地层典》记失   总被引：1，自引：0，他引：1       下载免费PDF全文

张守信 《地质科学》2005,40(1):145-152

文章列数了《中国地层典》5个方面的重要失误:不是中国地层名称全览性的工具书,急于采用处于争议中的术语,大量地层单位名称的出处因考证不到位而形成张冠李戴,采用的历史优先律不是国际共识,在编撰过程中建立新名称。文章用选出的泰山杂岩、滹沱系、秦岭片岩和仑山石灰岩4个名称为例说明《中国地层典》对其出处的考证不到位,进而论证《中国地层典》的诸多解释可信度低。文章严肃地指出“历史优先律”给中国地层学造成的不良后果:它破坏了地层命名法的标准性,颠倒了中国地层命名史,干扰了中国地层名称的管理。  相似文献   

Reliability of mooring lines and piles for a permanently manned vessel in a tropical cyclone environment     

《Applied Ocean Research》2019

The factors of safety for stationkeeping systems in current standards (ISO, API) are not derived or validated using reliability analyses. As the oil and gas exploration and production is breaking new boundaries, deploying new floating systems and moving into regions with harsher environments, it is of paramount importance to understand what level of reliability these new marine structures are achieving. This paper presents a reliability analysis of the mooring system of a Floating LNG (FLNG) vessel permanently moored and permanently manned offshore North West Australia in a tropical cyclone environment. The reliability analysis addresses both the mooring chain and the pile foundation. The analysis accounts for the long term characteristics of the environment, including the short term variability, in response to a given sea state and the variability and uncertainty in strength of the mooring chain and the pile. The stationkeeping system was analysed using detailed time domain simulations, capturing system non-linearities and low frequency oscillations as well as wave frequency responses and, thereby, reducing modelling uncertainties to a minimum.It is found that for the conditions modelled, neither the chain nor the pile meet a target reliability of 10⁻⁴/annum using the factors of safety commonly used in design following current ISO and API standards. New factors of safety are proposed to achieve this target reliability. For the pile design, one complicating factor is that current design standards do not explicitly define the exceedance probability that should be associated with the characteristic value of the undrained shear strength to be used in the design. It is demonstrated that the required factor of safety is crucially dependent on the definition of this characteristic value and on the level and the type of uncertainty in the soil strength profile. A recommendation is made regarding the definition of this characteristic value and the associated factor of safety. Furthermore, it is found that designing the mooring system to an environmental condition with a return period of 10,000 yr (as an Abnormal Limit State event), and setting the factor of safety to unity, meets the target reliability of 10⁻⁴/annum for the pile, if the characteristic undrained shear strength is a lower bound, defined in this paper by the 10th percentile value. For the chain however, this target reliability is not achieved.  相似文献   

辽东湾海洋工程可靠性设计的海冰参数选取     

马玉贤  关湃  许宁  许有良  袁帅  刘永青  于福祥 《海洋工程》2019,37(3):136-142

海冰参数的合理取值是海洋工程海冰灾害风险评估的重要内容。利用1950—2018年的冰情等级(5个等级)数据,进行了1950—2018、1950—1990、1991—2018三种情景下的回归分析,确定了不同时期的冰情等级概率分布密度函数。利用鲅鱼圈雷达观测站2002—2017年的海冰现场实测资料,分别对鲅鱼圈附近海域一般冰厚、最大冰厚、最小冰厚进行概率分布拟合。基于上述概率分布结果,给出不同冰情等级的重现期,进而对海冰作业条件给出的设计参考值进行评价。结果表明:1990年以后2级、3级冰情重现期相对1990年之前变小,4级、5级冰情重现期相对1990年之前变大,规范给出重现期范围已不能代表辽东湾冬季海冰情况。本研究成果可为辽东湾海洋工程可靠性设计提供重要数据支撑。  相似文献   

Assessing the reliability of probabilistic flood inundation model predictions          下载免费PDF全文

Elisabeth Stephens  Paul Bates 《水文研究》2015,29(19):4264-4283

An ability to quantify the reliability of probabilistic flood inundation predictions is a requirement not only for guiding model development but also for their successful application. Probabilistic flood inundation predictions are usually produced by choosing a method of weighting the model parameter space, but previous study suggests that this choice leads to clear differences in inundation probabilities. This study aims to address the evaluation of the reliability of these probabilistic predictions. However, a lack of an adequate number of observations of flood inundation for a catchment limits the application of conventional methods of evaluating predictive reliability. Consequently, attempts have been made to assess the reliability of probabilistic predictions using multiple observations from a single flood event. Here, a LISFLOOD‐FP hydraulic model of an extreme (>1 in 1000 years) flood event in Cockermouth, UK, is constructed and calibrated using multiple performance measures from both peak flood wrack mark data and aerial photography captured post‐peak. These measures are used in weighting the parameter space to produce multiple probabilistic predictions for the event. Two methods of assessing the reliability of these probabilistic predictions using limited observations are utilized; an existing method assessing the binary pattern of flooding, and a method developed in this paper to assess predictions of water surface elevation. This study finds that the water surface elevation method has both a better diagnostic and discriminatory ability, but this result is likely to be sensitive to the unknown uncertainties in the upstream boundary condition. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

An efficient quasi-Newton approximation-based SORM to estimate the reliability of geotechnical problems     

《Computers and Geotechnics》2016

The first order reliability method (FORM) is efficient, but it has limited accuracy; the second order reliability method (SORM) provides greater accuracy, but with additional computational effort. In this study, a new method which integrates two quasi-Newton approximation algorithms is proposed to efficiently estimate the second order reliability of geotechnical problems with reasonable accuracy. In particular, the Hasofer–Lind–Rackwitz–Fiessler–Broyden–Fletcher–Goldfarb–Shanno (HLRF–BFGS) algorithm is applied to identify the design point on the limit state function (LSF), and consequently to compute the first order reliability index; whereas the Symmetric Rank-one (SR1) algorithm is nested within the HLRF–BFGS algorithm to compute good approximations, yet with a reduced computational effort, of the Hessian matrix required to compute second order reliabilities. Three typical geotechnical problems are employed to demonstrate the ability of the suggested procedure, and advantages of the proposed approach with respect to conventional alternatives are discussed. Results show that the proposed method is able to achieve the accuracy of conventional SORM, but with a reduced computational cost that is equal to the computational cost of HLRF–BFGS-based FORM.  相似文献   

风云卫星数据服务评价指标的验证分析     

李雪  咸迪  亓永刚  徐喆  钱建梅 《气象科技》2016,44(4):692-696

简述了目前我国风云卫星数据服务以及气象服务效益评估业务的现状,利用层次分析法提出风云卫星数据服务评价的6个1级指标和19个2级指标。设计了风云卫星数据服务评测量表,并采用分半信度、因子分析等方法对量表作信度和效度分析,结果表明所设计的评测量表具有良好的信度和效度,确定了包括服务平台易用性、服务流程规范性、服务响应及时性、服务内容完整性、服务工作主动性、服务宣传广泛性等6个方面的风云卫星数据服务评价指标。  相似文献   

Variability of levee failure mechanisms subject to heavy rainfalls,case studies in Taiwan     

Wen-Chao Huang  Hong-Wen Yu 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2016,10(4):269-279

In this study, the failure mechanisms for Chiuliao 1st Levee and Gueishan Levee in Taiwan were re-examined comprehensively considering the uncertainty of different parameters. Results have shown that for Chiuliao 1st Levee, the slope sliding failure has a higher coefficient of variation (COV). For Gueishan Levee, retaining wall sliding and overturning failure have higher values of COV instead. It can also be found that the scouring depths affect the stability of the levee significantly, therefore, a protecting system for the backfill material may be necessary to increase the stability of the levee effectively.  相似文献