堤防工程安全评估中几个问题的探讨

在对国内外有关堤防工程安全评估研究工作调查的基础上,针对目前堤防工程的管理现状和发展前景,从堤防工程安全评价的含义、影响堤防工程安全的主要因素、影响因素的量化处理和权系数的选择、评估指标集的选取等几个方面对影响堤防工程安全评估进行了系统的探讨,并对堤防实时监测工作的几个环节给予了讨论。在此基础上初步形成了堤防工程安全评估的理论体系。     

Impact of repository depth on residence times for leaking radionuclides in land-based surface water

The multiple scales of landscape topography produce a wide distribution of groundwater circulation cells that control the hydro-geological environments surrounding geological repositories for nuclear waste. The largest circulation cells tend to discharge water into major river reaches, large freshwater systems or the nearby Baltic Sea. We investigated numerically the release of radionuclides from repositories placed in bedrock with depths between 100 to 2000 meters in a Swedish coastal area and found that leakage from the deeper positions emerges primarily in the major aquatic systems. In effect, radionuclides from the deeper repositories are more rapidly transported towards the Sea by the stream system compared to leakage from more shallow repositories. The release from the shallower repositories is significantly retained in the initial stage of the transport in the (superficial) landscape because the discharge occurs in or near low-order streams with high retention characteristics. This retention and residence time for radioactivity in the landscape control radiological doses to biota and can, thus, be expected to constitute an essential part of an associated risk evaluation.     

Assembly and dispersal of Pangea: Large-scale tectonic effects on coeval deposition of North American, marine, epicontinental, black shales

Both before and after inclusion of Laurussia in Pangea, the continent was a site of extensive epicontinental, marine, black-shale deposition, but from Pennsylvanian to Jurassic time when North America was an integral part of Pangea, the pattern of black-shale deposition was one of long-term decline. In North America the decline seems to have been greatest in Late Permian and Triassic times. Although this decline could have reflected a period of global cooling and a related decrease in organic productivity brought on by conditions associated with the supercontinent state, mapping the distribution of black shales in time and space on North American parts of Pangea suggests that the restricted availability of suitable repositories for organic-rich sediments may have been an equally important cause. In fact, mapping shows that the distribution of North American, Pangean, marine, black shales was greatest during Mississippian assembly of Laurussia when foreland-basin-type repositories were abundant and again during Late Jurassic fragmentation when rift-basin-type repositories were abundant. In both cases, tectonically conditioned basins formed the major repositories and promoted certain conditions that enhanced early basin anoxia.During Late Permian and Triassic time, when Pangea had been assembled, neither compressive orogenies nor crustal extension were major influences on North America. Consequently, suitable repositories were minimal and so was the extent of black-shale deposition. However, the continued presence of even a few major black-shale deposits during this time of minimum suggests that even low organic productivity was not a primary cause of decline and points to the possible significance of active continent assembly and breakup in generating tectonic-basin repositories conducive to accumulation and preservation of the organic matter that is nearly always present in quantities great enough to form major black-shale deposits.     

Assessing leakage detectability at geologic CO2 sequestration sites using the probabilistic collocation method

We present an efficient methodology for assessing leakage detectability at geologic carbon sequestration sites under parameter uncertainty. Uncertainty quantification (UQ) and risk assessment are integral and, in many countries, mandatory components of geologic carbon sequestration projects. A primary goal of risk assessment is to evaluate leakage potential from anthropogenic and natural features, which constitute one of the greatest threats to the integrity of carbon sequestration repositories. The backbone of our detectability assessment framework is the probability collocation method (PCM), an efficient, nonintrusive, uncertainty-quantification technique that can enable large-scale stochastic simulations that are based on results from only a small number of forward-model runs. The metric for detectability is expressed through an extended signal-to-noise ratio (SNR), which incorporates epistemic uncertainty associated with both reservoir and aquifer parameters. The spatially heterogeneous aquifer hydraulic conductivity is parameterized using Karhunen–Loève (KL) expansion. Our methodology is demonstrated numerically for generating probability maps of pressure anomalies and for calculating SNRs. Results indicate that the likelihood of detecting anomalies depends on the level of uncertainty and location of monitoring wells. A monitoring well located close to leaky locations may not always yield the strongest signal of leakage when the level of uncertainty is high. Therefore, our results highlight the need for closed-loop site characterization, monitoring network design, and leakage source detection.     

Ongoing research on seismic safety assessment

Research on seismic safety assessment has been the centre of great interest among the scientific community in recent years. Although the devastating impact of earthquakes on current society should be incentive enough to increase research, the development of more realistic mechanical behaviour models and the continuous enhancement of computation capabilities are paramount factors contributing a great deal to the increase of such interest. In this context, three research areas can be identified as currently leading to important developments: code related research, especially in Europe where new design codes are in the implementation process; risk analysis, namely concerning the definition of methodologies for safety assessment that involve the evaluation of the failure probability and could be included in future generations of codes; and experimental characterization of constitutive laws which provides support for the development and calibration of accurate and realistic numerical models for seismic analysis and for the adequate characterization of limit state capacities. The paper will present some of the current scientific research trends on these three seismic safety assessment related topics. Studies addressing the seismic safety assessment of structures, either probabilistically or based on code provisions, and that consider realistic nonlinear mechanical behaviour models will be focussed. Reference will also be made to experimental research on the seismic behaviour of structural elements, emphasizing its crucial role to support the development of numerical models simulating the effects of different seismic strengthening techniques. Finally, given the development of studies leading to new trends and perspectives for performance based earthquake engineering, a possible scenario for seismic design in the future is presented, emphasizing the key issues for its implementation.     

地震安全性评价制度改革的问题与展望

地震安全性评价制度是地震灾害预防制度的重要组成部分,自中华人民共和国成立之初演化发展至20世纪90年代基本成形,并纳入《中华人民共和国防震减灾法》.在深化"放管服"改革中,国务院先后取消了地震安全性评价资质许可和结果审定的行政审批事项,提出施行区域评估.在建立新制度过程中,面临着审批部门须承担委托开展地震安全性评价责任...     

天津近代典型砖木结构建筑基于安全鉴定的抗震性能评价

针对天津近代老旧建筑,尤其是砖木结构房屋开展了大量的安全鉴定和实际检测工作。获取了一栋近代典型砖木结构建筑的结构尺寸,检测了承重主体的强度,查明了结构的安全隐患,分析了结构的抗震性能,给出了抗震加固的建议措施,对全国近代典型砖木结构的安全鉴定和抗震加固具有一定的指导意义。     

多层砌体房屋地震现场安全性鉴定子系统的研制与开发

本文利用模糊综合评判原理研究了多层砌体房屋地震现场安全性鉴定方法,并以此为基础研制了多层砌体房屋地震现场安全性鉴定子系统。本文将该子系统运用到两个实际问题中,所得结论与专家基于经验的现场鉴定相吻合,初步验证了系统分析模块的可靠性。     

黄河胜利大桥动力测试和安全评估

大跨度斜拉桥的整体安全性评估对桥梁的运营管理具有十分重要的意义。在环境激励条件下,测试了黄河胜利大桥桥塔、主桥桥跨的基本动力特性以及斜拉索的索力。利用动力检测结果,以白振频率变化作为桥梁整体安全指标,并通过测试数据与设计允许值的比较,采用整体状态评估的方法研究了黄河胜利大桥的安全性。研究结果表明,大桥桥塔、主桥桥跨结构整体性较好,斜拉索也基本处于正常工作状态。     

Seismic fragility assessment of concrete gravity dams

Many concrete gravity dams have been in service for over 50 years, and over this period important advances in the methodologies for evaluation of natural phenomena hazards have caused the design‐basis events for these dams to be revised upwards. Older existing dams may fail to meet revised safety criteria and structural rehabilitation to meet such criteria may be costly and difficult. Fragility assessment provides a tool for rational safety evaluation of existing facilities and decision‐making by using a probabilistic framework to model sources of uncertainty that may impact dam performance. This paper presents a methodology for developing fragilities of concrete gravity dams to assess their performance against seismic hazards. The methodology is illustrated using the Bluestone Dam on the New River in West Virginia, which was designed in the late 1930s. The seismic fragility assessment indicated that sliding along the dam–foundation interface is likely if the dam were to be subjected to an earthquake with a magnitude of the maximum credible earthquake (MCE) specified by the U.S. Army Corps of Engineers. Moreover, there will likely be tensile cracking at the neck of the dam at this level of seismic excitation. However, loss of control of the reservoir is unlikely. Copyright © 2003 John Wiley & Sons, Ltd.     

西南地区区域地震构造图数据库

利用西南地区多年来积累的地震安全性评价工作成果,借助地理信息系统MapInfo强大的空间信息表达能力,使在MapInfo平台上构建西南地区区域地震构造图数据库成为可能。文中使用空间数据库与属性数据库分开设计的方法,采用多个层次、多种基本类型、多表关联的数据库格式,在MapInfo平台上构建了西南地区区域地震构造图数据库     

Risk assessment of offshore oil and gas activities in the Netherlands

Offshore oil and gas activities may lead to a conflict between the protection of the marine environment and health and safety aspects. Priority given to the protection of the marine environment may have an impact on the health or safety of the people working offshore and/or the integrity of the offshore installation. Previous health and safety protection measures are now known to create large-scale effects on the environment, e.g. the application of polychlorinated biphenyls as a cooling medium in transformers and the application of the ozone-depleting halons for efficient fire protection. Risk assessment, taking all health and safety aspects into account, may be the primary mechanism to justify operational procedures agreed by the national authorities as well as by the Exploration and Production industry. Risk assessment of health and safety aspects uses several models which are applied when designing new offshore installations. Several models, which have been developed in the last couple of years, are now available for the assessment of the environmental risk. This paper considers the need for the application of risk assessment with respect to all aspects, health, safety and environment, in order to determine a balanced set of priorities and protection measures.     

Upscaling of a dual-permeability Monte Carlo simulation model for contaminant transport in fractured networks by genetic algorithm parameter identification

The transport of radionuclides in fractured media plays a fundamental role in determining the level of risk offered by a radioactive waste repository in terms of expected doses. Discrete fracture networks methods can provide detailed solutions to the problem of modeling the contaminant transport in fractured media. However, within the framework of the performance assessment (PA) of radioactive waste repositories, the computational efforts required are not compatible with the repeated calculations that need to be performed for the probabilistic uncertainty and sensitivity analyses of PA. In this paper, we present a novel upscaling approach, which consists in computing the detailed numerical fractured flow and transport solutions on a small scale and use the results to derive the equivalent continuum parameters of a lean, one-dimensional dual-permeability, Monte Carlo simulation model by means of a genetic algorithm search. The proposed upscaling procedure is illustrated with reference to a realistic case study of $ {}^{239}{\text{Pu}} $ migration taken from literature.     

New concepts in ecological risk assessment: where do we go from here?

Through the use of safety factors, the use of single-species test data has been adequate for use in protective hazard assessments and criteria setting but, because hazard quotients do not consider the presence of multiple species each with a particular sensitivity or the interactions that can occur between these species in a functioning community, they are ill-suited to environmental risk assessment. Significant functional redundancy occurs in most ecosystems but this is poorly considered in single-species tests conducted under laboratory conditions. A significant advance in effects assessment was the use of the microcosm as a unit within which to test interacting populations of organisms. The microcosm has allowed the measurement of the environmental effect measures such as the NOAEC(community) under laboratory or field conditions and the application of this and other similarly derived measures to ecological risk assessment (ERA). More recently, distributions of single-species laboratory test data have been used for criteria setting and, combined with distributions of exposure concentrations, for risk assessment. Distributions of species sensitivity values have been used in an a priori way for setting environmental quality criteria such as the final acute value (FAV) derived for water quality criteria. Similar distributional approaches have been combined with modeled or measured concentrations to produce estimates of the joint probability of a single species being affected or that a proportion of organisms in a community will be impacted in a posteriori risk assessments. These techniques have not been widely applied for risk assessment of dredged materials, however, with appropriate consideration of bioavailability and spatial and nature of the data these techniques can be applied to soils and sediments.     

PROBABLE MAXIMUM FLOOD FOR DAM SAFETY ASSESSMENT

ＰＲＯＢＡＢＬＥＭＡＸＩＭＵＭＦＬＯＯＤＦＯＲＤＡＭＳＡＦＥＴＹＡＳＳＥＳＳＭＥＮＴＣ．Ｆ．ＬＥＥ（Ｆｏｒｍｅｒｌｙ，ＭａｎａｇｅｒｏｆＧｅｏｔｅｃｈｎｉｃａｌａｎｄＨｙｄｒａｕｌｉｃＥｎｇｉｎｅｅｒｉｎｇＤｅｐａｒｔｍｅｎｔ；ＭａｎａｇｅｒｏｆＣｉ...     

土木工程结构安全性评估、健康监测及诊断述评

阐述了土木工程结构的安全性评估、健康监测及损伤诊断的必要性和迫切性，系统论述了结构健康监测和诊断的概念、理论和方法，重点讨论了传感器的优化布置、损伤识别等健康监测中的关键问题，介绍了光纤等新型传感器的应用情况，最后指出了值得进一步研究的问题。     

Analysis of seismic disaster failure mechanism and dam-break simulation of high arch dam

Based on a Chinese national high arch dam located in a meizoseismal region, a nonlinear numerical analysis model of the damage and failure process of a dam-foundation system is established by employing a 3-D deformable distinct element code(3DEC) and its re-development functions. The proposed analysis model considers the dam-foundation-reservoir coupling effect, infl uence of nonlinear contact in the opening and closing of the dam seam surface and abutment rock joints during strong earthquakes, and radiation damping of far fi eld energy dissipation according to the actual workability state of an arch dam. A safety assessment method and safety evaluation criteria is developed to better understand the arch dam system disaster process from local damage to ultimate failure. The dynamic characteristics, disaster mechanism, limit bearing capacity and the entire failure process of a high arch dam under a strong earthquake are then analyzed. Further, the seismic safety of the arch dam is evaluated according to the proposed evaluation criteria and safety assessment method. As a result, some useful conclusions are obtained for some aspects of the disaster mechanism and failure process of an arch dam. The analysis method and conclusions may be useful in engineering practice.     

城市地下轨道交通火灾风险评估体系模型研究——以某地铁车站为例

用按时序分阶段的评估方法建立了城市地下交通火灾风险评估体系的架构,并用改进的层次分析法建立了多层次评估指标权重模型,建立了判断火灾风险的评价标准。以北京地铁二号线某车站为例,在对其现有设备资料和运行特性进行详细调研分析的基础上,把风险评估结构划分为目标层、准则层、指标层,并按照现有的参考依据对各项影响火灾安全的风险因素进行赋值计算,得到了火灾各个阶段该车站的火灾风险水平,并对评价中的薄弱环节,提出了有针对性的建议。研究结果可供地下交通系统火灾应急预案制定参考。     

Seismic hazard analysis for engineering sites based on the stochastic finite-fault method

Seismic hazard analyses are mainly performed using either deterministic or probabilistic methods. However, there are still some defects in these statistical model-based approaches for regional seismic risk assessment affected by the near-field of large earthquakes. Therefore, we established a deterministic seismic hazard analysis method that can characterize the entire process of ground motion propagation based on stochastic finite-fault simulation, and we chose the site of the Xiluodu dam to demonstrate the method. This method can characterize earthquake source properties more realistically than other methods and consider factors such as the path and site attenuation of seismic waves. It also has high computational efficiency and is convenient for engineering applications. We first analyzed the complexity of seismogenic structures in the Xiluodu dam site area, and then an evaluation system for ground motion parameters that considers various uncertainties is constructed based on a stochastic finite-fault simulation. Finally, we assessed the seismic hazard of the dam site area comprehensively. The proposed method was able to take into account the complexity of the seismogenic structures affecting the dam site and provide multi-level parameter evaluation results corresponding to different risk levels. These results can be used to construct a dam safety assessment system of an earthquake in advance that provides technical support for rapidly and accurately assessing the post-earthquake damage state of a dam, thus determining the influence of an earthquake on dam safety and mitigating the risk of potential secondary disasters.     

地震现场工作刍议

简要回顾了随着我国社会经济的发展, 地震现场工作经历的5个发展历程。 随后从人员、 技术、 制度、 装备、 体能和心理等方面概述了震前应急准备工作, 详细介绍了地震现场的震情分析预报、 地震监测、 地震紧急救援、 地震灾害损失评估、 科学考察、 建筑物安全鉴定、 现场通信保障、 地震宣传和后勤保障等各项工作的主要内容、 遵循的工作依据和技术规范及须注意的问题。