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1.
S. M. Dassanayake 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2020,14(1):41-55
ABSTRACTThere is a growing body of evidence confirming the detrimental effects of invasive wildlife activities on the performance and – ultimately – the safety of earth dams and levee systems. Modelling cavities and burrows dug by animals in earth structures is rather cumbersome due to their geometrical complexity and randomness. This study proposes the use of the probabilistic approach to estimate the risk associated with the presence of wildlife chambers in an arbitrary dam section. Two dimensional limit equilibrium slope stability analyses were conducted for a homogeneous silty sand dam. The animal chambers were modelled as idealised highly permeable circles with a near-zero strength. Uncertainty in the dam material was introduced using the Monte-Carlo technique to randomise the input parameters. The conditional probability of failure, P(F|C), was spatially evaluated by manual perturbations of chamber locations within the dam section. Using the Bayesian approach, the section was accordingly mapped into three stability zones: “safe”, “marginally safe” and “likely to fail” based on P(F|C) values associated with the chamber location. For this very complex problem, the probabilistic handling seems to provide a mathematically normalised basis for risk assessment in lieu of the classical belief-based single-value factor of safety (FoS). 相似文献
2.
Jia-Jyun Dong Yu-Hsiang Tung Chien-Chih Chen Jyh-Jong Liao Yii-Wen Pan 《Engineering Geology》2011,117(1-2):52-61
Landslides may obstruct river flow and result in landslide dams; they occur in many regions of the world. The formation and disappearance of natural lakes involve a complex earth–surface process. According to the lessons learned from many historical cases, landslide dams usually break down rapidly soon after the formation of the lake. Regarding hazard mitigation, prompt evaluation of the stability of the landslide dam is crucial. Based on a Japanese dataset, this study utilized the logistic regression method and the jack-knife technique to identify the important geomorphic variables, including peak flow (or catchment area), dam height, width and length in sequence, affecting the stability of landslide dams. The resulting high overall prediction power demonstrates the robustness of the proposed logistic regression models. Accordingly, the failure probability of a landslide dam can also be evaluated based on this approach. Ten landslide dams (formed after the 1999 Chi-Chi Earthquake, the 2008 Wenchuan Earthquake and 2009 Typhoon Morakot) with complete dam geometry records were adopted as examples of evaluating the failure probability. The stable Tsao-Ling landslide dam, which was induced by the Chi-Chi earthquake, has a failure probability of 27.68% using a model incorporating the catchment area and dam geometry. On the contrary, the Tangjiashan landslide dam, which was artificially breached soon after its formation during the Wenchuan earthquake, has a failure probability as high as 99.54%. Typhoon Morakot induced the Siaolin landslide dam, which was breached within one hour after its formation and has a failure probability of 71.09%. Notably, the failure probability of the earthquake induced cases is reduced if the catchment area in the prediction model is replaced by the peak flow of the dammed stream for these cases. In contrast, the predicted failure probability of the heavy rainfall-induced case increases if the high flow rate of the dammed stream is incorporated into the prediction model. Consequently, it is suggested that the prediction model using the peak flow as causative factor should be used to evaluate the stability of a landslide dam if the peak flow is available. Together with an estimation of the impact of an outburst flood from a landslide-dammed lake, the failure probability of the landslide dam predicted by the proposed logistic regression model could be useful for evaluating the related risk. 相似文献
3.
Alitabar Abbas Noorzad Reza Qolinia Afshin 《Geotechnical and Geological Engineering》2021,39(6):4237-4251
Embankment dams are one of the most important geotechnical structures that their failures can lead to disastrous damages. One of the main causes of dam failure is its slope instability. Slope Stability analysis has traditionally been performed using the deterministic approaches. These approaches show the safety of slope only with factor of safety that this factor cannot take into account the uncertainty in soil parameters. Hence, to investigate the impact of uncertainties in soil parameters on slope stability, probabilistic analysis by Monte Carlo Simulation (MCS) method was used in this research. MCS method is a computational algorithm that uses random sampling to compute the results. This method studies the probability of slope failure using the distribution function of soil parameters. Stability analysis of upstream and downstream slopes of Alborz dam in all different design modes was done in both static and quasi-static condition. Probability of failure and reliability index were investigated for critical failure surfaces. Based on the reliability index obtained in different conditions, it can be said that the downstream and upstream slope of the Alborz dam is stable. The results show that although the factor of safety for upstream slope in the state of earthquake loading was enough, but the results derived from probabilistic analysis indicate that the factor of safety is not adequate. Also the upstream slope of the Alborz dam is unstable under high and uncontrolled explosions conditions in steady seepage from different levels under quasi-static terms.
相似文献4.
In the geotechnical field, the risk related to slope instabilities or collapse of geotechnical structures are increasingly being faced by early warning systems, capable of: (1) predicting the incipient collapse based on the interpretation of a continuous monitoring of the structure and (2) spreading alarm promptly to reduce people exposure. Compared with structural approaches, early warning systems have two important advantages: a faster, simpler and less expensive implementation and environmental compatibility. Past experience indicates that vulnerability of earth dams is generally low under both static and seismic loading conditions. In spite of this, earth dams are characterized by a high-risk level, due to the high exposure factor. Nowadays, the application of early warning systems to dams is fully supported by the technological progress achieved in the telecommunication field, since it is possible to install and automate recordings and transmission of all physical variables significant to check dam safety: accelerations, displacements, pore-water pressures, total stresses, seepage flows. A considerable lack still arises in the predictive models for interpreting monitoring data and providing indicators on dam safety soon after a strong earthquake. The present work illustrates the basic concepts of an earthquake early warning (EEW) system for earth dams and the main features that should characterize a predictive model to such a scope. An application to a real case is finally provided, enhancing the role played by each monitored physical variable for the aims of EEW. 相似文献
5.
Dwayne D. Tannant 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2015,9(3):148-157
The Testalinden earth dam in southern British Columbia failed in June 2010 and created a huge debris flow. Homes were destroyed and property was damaged. The failure of this small dam resulted in a comprehensive review of over 1000 dams in the province, evaluation of dam safety management practices, changes to the Water Act and improvements in how data on dams are collected, archived and communicated. The provincial dam inventory was re-evaluated to ensure that appropriate consequence classification, and therefore attention, is assigned to dams. Increased scrutiny was placed on dam owners to ensure they complied with dam safety policies and to ensure they submitted annual inspection reports and formal dam safety reviews in a timely manner. Dam owners and professionals engaged in dam safety activities have received new guidelines and better education and training. 相似文献
6.
The Bhuj, India, earthquake of 26 January 2001, Ms 7.9, caused dams built on alluvium to sustain damage ranging from cosmetic to severe. Major damage was caused almost entirely by soil liquefaction in the alluvium. The critical factor was the level of earthquake ground motion.
The Bhuj earthquake showed that peak horizontal accelerations (PHAs)≤0.2 g were generally safe. PHAs>0.2 g were hazardous, when unconsolidated granular foundation soils were water saturated. N values of <20 are indicative of susceptibility to soil liquefaction. The Bhuj experience showed that alluvial foundation soils, subject to a PHA>0.2 g, must be evaluated over the full area beneath a new dam and all soils deemed susceptible to liquefaction must be either removed or treated. For remediating an old dam, reliable options are removal and replacement of liquefiable alluvium beneath upstream and downstream portions of the dam, combined with building berms designed to provide stability for the dam should there be a strength loss in soils beneath the dam. 相似文献
7.
The geologic structures associated with several selected dam sites in Jordan and the tectonic effects on dam foundations and reservoir margins are reviewed. Rock defects, especially discontinuities represented by faults and closely spaced, open joints are investigated. Related problems, such as loss of water from the reservoir by seepage and leakage within the dam foundation are evaluated. The regional seismicity is analyzed and a design earthquake is established for each dam site.
Two major embankment dams are investigated, together with two large proposed dams and several small dams.
This paper discusses in some detail the regional setting and site-specific geology, and the occurrence, size and inclination of faults and joints at each dam site. Moreover, the effects of the faults on the operational performance of each dam are described and specific techniques are used or proposed for remediation are outlined.
The study shows that the combination of faults and joint features cause leakage problems at the operational dams in Jordan. Although, preventive measures such as grouting have been implemented, further leakage and/or seepage problems are anticipated and a monitoring system is needed to control and foresee such problems.
Jordan is an earthquake-prone region. Consequently, it is recommended that the design of embankment dams in the vicinity of the Dead Sea-Jordan Valley Rift should include such considerations as dynamic loading and associated hazards, including embankment acceleration zoning, foundation liquefaction risk and rockhead rupture. The magnitude of the design earthquake at each dam site can be estimated following the guidelines of ICOLD (1989), which are based on probabilistic seismic hazard analysis. 相似文献
8.
Santi Pailoplee 《Natural Hazards》2014,74(3):1813-1827
In this study, the earthquake hazard was evaluated for all of 19 of the proposed or built dams along the Mekong River. All values representing a potential indication of hazardous earthquakes, such as the closest earthquake and seismogenic faults and including the seismic parameters required for a seismic safety evaluation, were clarified. The results will be useful in reviewing the safety of existing dams and for the design of suitable earthquake resistant specifications for any currently or future planned dam construction in this area. Seismotectonically, 14 of the 19 proposed Mekong River dams are located within an earthquake source zone. Most of faults are potentially still active, according to both seismicity and paleoseismological evidence. In addition, the maximum credible earthquakes were estimated to be in the range of 7–8 Mw for the closest fault zone of each dam. Previous isoseismal maps indicated a risk of shaking intensities of around scale III–IV (Modified Mercalli Intensity Scale) for the dams. According to the preliminary ranging of the International Commission on Large Dams, 9 of these 19 dams are classified as in an extreme hazard class and so need careful observation and monitoring of hazardous earthquakes. An effective mitigation plan should also be prepared for each operating dam. 相似文献
9.
Different models were developed for evaluating the probabilistic three-dimensional (3-D) stability analysis of earth slopes and embankments under earthquake loading. The 3-D slope stability model assumed is that of a simple cylindrical failure surface. The probabilistic models evaluate the probability of failure under seismic loading considering the randomness of earthquake occurrence, and earthquake induced acceleration and uncertainties stemming from the discrepancies between laboratory-measured and in-situ values of shear strength parameters. The models also takes into consideration the spatial variabilities and correlations of soil properties. The probabilistic analysis and design approach is capable of obtaining the 2-D and 3-D static and dynamic safety factors, the probability of slope failure, the earthquake induced acceleration coefficient, the yield acceleration coefficient, the earthquake induced displacement, and the probability of allowable displacement exceedance taking into account the local site effect. The approach is applied to a well known landslide case: Congress Street Landslide in Chicago. A sensitivity analysis was conducted on the different parameters involved in the models by applying those models to the Congress Street landslide considering different levels of seismic hazard. Also, a sensitivity analysis was carried out to study the sensitivity of computed results to input parameters of undrained shear strength, and corrective factors. A comparison was made between the different models of failure. The parametric study revealed that the hypocentral distance and earthquake magnitude have major influence on the earthquake induced displacement, probability of failure and dynamic 2-D and 3-D safety factors. 相似文献
10.
覆盖层上土石坝非线性动力响应分析的地震波动输入方法 总被引：1，自引：0，他引：1
较多已建和待建的土石坝直接修筑于覆盖层上,合理描述土石坝与覆盖层之间的动力相互作用对大坝抗震安全评价至关重要。基于等效荷载和人工边界的地震波动输入方法能较好地反映出结构-地基之间的相互作用并得到了广泛应用。等效荷载和人工边界参数在均质线弹性地基条件下易于获得,而对于覆盖层地基,土体动力非线性特性给求解带来很大困难。鉴于此,首先根据覆盖层侧向边界的位移模式,发展了能高效、精确地获取多向地震动垂直入射时均质或成层覆盖层自由场非线性动力响应的简化模型;结合能动态实时获取地基材料参数的非线性人工边界,发展了一套覆盖层上土石坝非线性动力响应分析的地震波动输入方法。算例表明,发展的地震波动输入方法可大大减小计算网格量,并能较好地反映覆盖层对地震动频谱特性的影响且具有较高的精度。 相似文献
11.
Embankment dams are important and costly civil engineering structures that provide an essential infrastructure for the management of water. One of the critical aspects of dam design is the analysis of stability and safety of the earth structure under various operating and environmental conditions. Traditionally, a deterministic approach is used for such analysis. However, the determination of variables such as soil strength parameters, pore pressure and other pertinent properties involves uncertainties, which cannot be handled in the traditional deterministic methods. It is, therefore, highly desirable to develop a reliability based analytical/numerical methodology for stability analysis of dams taking into account these uncertainties. Reliability and probability theories are developed in this paper for assessing the reliability index and the corresponding probability of failure of multi-layered embankment dams and slopes. Two definitions were used to calculate the reliability index (i.e. the normal distribution and the log–normal distribution). The computer program
was developed and validated by the Congress Street open cut failure case. The developed approach was used to study the stability of the King Talal embankment dam. The results are discussed and conclusions drawn. 相似文献
12.
The 12 May Wenchuan earthquake-induced landslide lakes: distribution and preliminary risk evaluation 总被引：26，自引：9，他引：17
The Wenchuan earthquake, measured at M
s 8.0 according to the China Earthquake Administration, occurred at 14:28 on 12 May 2008 in the Sichuan Province of China.
It brought overwhelming destruction to eight provinces and cities. Landslides and rock avalanches triggered by the earthquake
produced 257 landslide lakes which were distributed along the fault rupture zone and river channels. The authors traveled
to the disaster zone immediately after the earthquake to examine some of the features of the debris dams and performed a quick
evaluation of the potential for outburst of earthquake-induced landslide lakes for the purpose of disaster relief. The preliminary
analysis indicated that the landslide lakes could be classified as those exhibiting extremely high risk, medium risk, and
low risk according to field observations and remote sensing, to determine material composition, dam structure, dam height,
maximum water storage capacity, and size of the population potentially affected area. The failure risk of 21 debris dams were
evaluated as follows: one dam with an extremely high danger risk, seven dams with a high danger, five dams with a medium danger,
and eight dams of low danger. More concern was given to the Tangjiashan Lake and different scenarios for the potential sudden
failure of its dam were assessed. The risk evaluation result was accepted in full, by the earthquake disaster relief office.
A successful emergency dam treatment for risk reduction was planned, based on our assessments, and these measures were quickly
carried out. According to this research, the earthquake destabilized the surrounding mountains, resulting in a prolonged geohazard
for the area. Landslides and debris flows will continue to develop for at least 5 to 10 years after the Wenchuan earthquake
and will produce additional dammed lakes. Recommendations and plans for earthquake–landslide lake mitigation were proposed,
based on past successful practices. 相似文献
13.
A. Gabriel Villavicencio Pierre Breul Claude Bacconnet Daniel Boissier A. Raúl Espinace 《Geotechnical and Geological Engineering》2011,29(6):1073-1084
Dams are often used for storing mine tailings. These structures present failure mechanisms that can lead to major risks for
surrounding populations. In view to managing these risks, it is necessary to take a probabilistic approach in predicting their
behaviour. The application of such approaches is limited by the difficulty of obtaining experimental data to estimate the
variability of the parameters and conditioned by the relevance of the probability models chosen to represent this variability.
This article proposes (1) a probabilistic modelling of the index properties of the mine tailings constituting these dams based
on statistical analyses and (2) a method using dynamic penetration tests to estimate on site the mine tailings friction angle
and its variability. This method, applied to chilean tailings dams proposes a single model for all tailings dams in order
to associate a probability law to the effective friction angle (ϕ′). The procedure is illustrated on the probabilistic study
of slope stability carried out at the global scale of a dam and also at the local scale of each of its constituent layers. 相似文献
14.
Abbas Abbaszadeh Shahri Bijan Esfandiyari Roshanak Rajablou 《Arabian Journal of Geosciences》2012,5(4):555-564
During the earthquakes, a number of earth dams have had severe damages or suffered major displacements as a result of liquefaction, thus modeling by computer codes can provide a reliable tool to predict the response of the dam foundation against earthquakes. These modeling can be used in the design of new dams or safety assessments of existing ones. In this paper, on the basis of the field and laboratory tests and by combination of several software packages a seismic geotechnical-based analysis procedure is proposed and verified by comparison with computer model tests and field and laboratory experiences. Verification or validation of the analyses relies to the ability of the applied computer codes. By using the Silakhor earthquake (2006, M s 6.1) as a basis in order to check the efficiency of the proposed framework, the procedure is applied to the Korzan earth dam of Iran which is located in Hamedan Province to analyze and estimate the liquefaction and safety factor. Design and development of a computer code by the authors which was named as the ??Abbas Converter?? with graphical user interface which operates as logic connecter function that can compute and model the soil profiles is the critical point of this study. The results confirmed and proved the ability of the generated computer code on the evaluation of soil behavior during earthquake excitations. Also, this code was able to facilitate this study better than previous ones have, taking over the encountered problem. 相似文献
15.
土石坝抗震安全的设计一般立足于预防结构的倒塌,如何使土石坝结构地震破损控制在可接受的风险水平是一个值得研究的重要课题。应用地震风险分析理论,建立了土石坝地震风险分析方法,包括地震危险性分析、地震易损性分析和地震灾害损失评估3个方面。在场地地震危险性分析基础上,将基于性能的抗震设计思想应用于土石坝结构地震易损性分析中,以土石坝坝顶相对沉陷为评价指标,划分土石坝震损等级,最后结合地震经济损失分析,建立了土石坝地震风险计算模型,在技术和经济上对土石坝地震破损风险进行分析计算。以某高土石坝为例,用该模型对大坝的震害和经济损失进行了预测分析,其结论可为土石坝安全评价及投资决策等提供依据。 相似文献
16.
Different models were developed for evaluating the probabilistic three-dimensional (3-D) stability analysis of earth slopes and embankments under earthquake loading using both the safety factor and the displacement criteria of slope failure.The probabilistic models evaluate the probability of failure under seismic loading considering the different sources of uncertainties involved in the problem. The models also take into consideration the spatial variabilities and correlations of soil properties. The developed models are incorporated in a computer program PTDDSSA.These analysis/design procedures are incorporated within a code named SARETL developed in this study for stability analysis and remediation of earthquake triggered landslides. In addition to the dynamic inertia forces, the system takes into consideration local site effects.The code is capable of assessing the landslide hazard affecting major transportation routes in the event of earthquakes and preparing earthquake induced landslide hazard maps (i.e., maps showing expected displacements and probability of slope/embankments failure) for different earthquake magnitudes and environmental conditions. It can also beused for proposing a mitigation strategy against landslides. 相似文献
17.
In probabilistic stability analyses of concrete dams founded on rock, the uplift pressure is often a parameter of major importance. In previous literature, it has been suggested that assessing uplift with pore pressure measurements, instead of using empirical assumptions, could improve the calculated dam safety. This paper presents a coherent methodology to investigate whether incorporating pore pressure measurements has any impact on the calculated dam safety, based on Bayesian linear regression of pore pressure data in combination with series-system and the first-order reliability method. The study concludes that the probability of sliding failure is closely related to the probability of an extreme increase in uplift. Hence, measured uplift should only be incorporated while this probability remains sufficiently small, which requires proper programs both for uplift monitoring and for maintenance of drains and grout curtains. 相似文献
18.
考虑饱和-非饱和渗流的土坡极限分析 总被引：2，自引：1，他引：1
给出了均质土坝的下游坝坡的安全系数的计算方法。均质土坝的下游坝坡有可能会通过滑裂面发生破坏。土坝中的土坡通常处于非饱和状态。非饱和土坡的安全系数计算需要考虑吸力对抗剪强度的贡献以及土坡中的非饱和渗流。给出处于饱和-非饱和渗流状态下的土坡的安全系数,有助于评价均质土坝的安全系数。下游坝坡的安全系数计算方法有：极限平衡法、上限解法和下限解法,该算法适用于非饱和土坡,且是在饱和土坡安全系数的计算方法上修正得到的。算例中非饱和土坡安全系数的计算考虑了吸力对抗剪强度的贡献。考虑非饱和渗流理论的土坡安全系数计算方法通常更加接近现场实际情况,并且对于同一坝坡,考虑非饱和渗流计算出的土坡安全系数要比饱和渗流理论计算出的安全系数大。 相似文献
19.
Modeling uncertainty in stability analysis for design of embankment dams on difficult foundations 总被引：2，自引：0，他引：2
A probabilistic 3-D slope stability analysis model (PTDSSAM) is developed to evaluate the stability of embankment dams and their foundations under conditions of staged construction taking into consideration uncertainty, spatial variabilities and correlations of shear strength parameters, as well as the uncertainties in pore water pressure. The model has the following capabilities: (1) conducting undrained shear strength analysis (USA) and effective stress analysis (ESA) slope stability analysis of staged construction, (2) incorporation of field monitored data of pore water pressure, and (3) incorporation of increase of undrained shear strength with depth, effective stress, and pore water pressure dissipation. The PTDSSAM model is incorporated in a computer program that can analyze slopes located in multilayered deposits, considering the total slope width.
The main outputs of the program are the geometric parameters of the most critical sliding surface (i.e., center of rotation/radius of rotation and critical width of failure), mean 2-D safety factor, mean 3-D safety factor, squared coefficient of variation of resisting moment, and the probability of slope failure. The program is applied to a case study, Karameh dam in Jordan. Monitored data of induced pore water pressure in the dam embankment and soft foundation were gathered during dam construction.
The stability of Karameh dam embankment and foundation was evaluated during staged construction using deterministic and probabilistic analysis. Foundation stability was evaluated based on the monitored data of pore water pressure.
The study showed that the mean values of the corrective factors which account for the discrepancies between the in situ and laboratory-measured values of soil properties and for the modeling errors have significant influence on the 2-D safety factor, 3-D safety factor, slope probability of failure, and on the expected failure width.
The degree of spatial correlation associated with shear strength parameters within a soil deposit also influences the probability of slope failure and the expected failure width. This correlation is quantified by scale of fluctuation. It is found that a larger scale of fluctuation gives an increase in the probability of slope failure and a reduction in the critical failure width. 相似文献
20.
强震作用下土石坝极易出现失稳破坏,从而造成人员伤亡和较大的社会经济损失.由于地震的不确定性,强震作用下土石坝失稳分析通常采用失稳概率表示,目前常用方法是地震易损性分析方法,主要有云图法和增量动力分析（incremental dynamic analysis,IDA）两种方法.IDA方法计算结果准确,但计算效率低,云图法计算效率虽高,但计算精度无法得到有效保证.基于上述问题,提出了一种基于云图法和IDA方法的地震易损性快速精准分析方法（CIHA,cloud-IDA hybrid approach）.CIHA方法可兼顾计算效率和计算精度,该方法基于云图法的对数线性回归假设,通过非线性时程分析,并对地震波进行一次放缩来计算相应损伤指标下的地震动强度值,利用地震动强度值得到的均值和方差生成土石坝在各个损伤等级下的易损性曲线.通过对Lower San Fernando土石坝的地震易损性分析,将所提CIHA方法与IDA方法的计算结果进行了对比.结果表明,在计算精度方面,CIHA方法可以获得与IDA方法相近的结果,在计算效率方面,CIHA方法相比IDA方法计算效率有显著提高. 相似文献