Quantitative risk assessment of landslide by limit analysis and random fields

Risk may be estimated by multiplying the probability of failure by the consequence. This is acceptable for systems that have a single mode of failure. For systems that have multiple failure modes, such as landslides, the consequences should be assessed individually for each of the failure modes. This paper proposes a new framework of quantitative landslide risk assessment, in which consequences are assessed individually. The framework is generally applicable, and the landslide risk assessments of two typical slopes are presented.     

Probability of scour depth exceedance owing to hydrologic uncertainty

The average risk of a bridge over water in the USA collapsing from scour during its 75 years design life is estimated at 3.7×10^?3. This risk makes scour of foundations the number one cause of bridge collapse and 3 times larger than the next cause of bridge collapse, which is collisions. The current paper presents a site specific method to estimate the probability that a certain scour depth will be exceeded during the life of a bridge. The methodology is limited to some uncertainties associated with the randomness of hydrologic conditions. It does not include uncertainties associated with other input parameters, such as geometry and soil erodibility or uncertainties associated with the scour prediction model. The SRICOS–EFA method is used as the reference method to predict the scour depth. This method requires three inputs: the hydraulic parameters (e.g. velocity hydrograph), the geometry parameters (e.g. pier size) and the soil erodibility parameters (e.g. erosion function). The input is used together with the program to generate the scour depth versus time over the period of interest. The final scour depth is that reached at the end of the specified period. This paper proposes a probabilistic framework to present the final scour depth as a cumulative density function. The cumulative density function of the flow is sampled randomly to give a future hydrograph, which has the same mean and standard deviation as the original hydrograph. For this synthetic hydrograph a final scour depth is obtained by using SRICOS–EFA. Thousands of equally likely hydrographs are generated and the corresponding final scour depths are organized in a distribution. That final scour depth distribution gives the probability that a chosen scour depth will be exceeded.     

Reliability of shallow foundations designed against bearing failure using LRFD

Worldwide, there is growing interest in the development of a rational reliability-based geotechnical design code. The reasons for this interest are at least two-fold; first, geotechnical engineers face significantly more uncertainties than those faced in other fields of engineering, therefore there is a need to properly characterize and deal with these uncertainties. Second, for decades, structural engineers have used a reliability-based design code, and there is a need to develop the same for geotechnical engineers, in order that the two groups can ‘speak the same language’. This paper develops a theoretical model to predict the probability that a shallow foundation will exceed its supporting soil's bearing capacity. The footing is designed using characteristic soil properties (cohesion and friction angle) derived from a single sample, or ‘core’, taken in the vicinity of the footing, and used in a load and resistance factor design approach. The theory predicting failure probability is validated using a two-dimensional random finite element method analysis of a strip footing. Agreement between theory and simulation is found to be very good. Therefore, the theory can be used with confidence to perform risk assessments of foundation designs and develop resistance factors for use in code provisions.     

Marine debris surveys at Volunteer Beach, Falkland Islands, during the summer of 2001/02

This survey evaluated the monthly accumulation rate of marine debris and the types of objects washed ashore at Volunteer Beach on East Falkland between October 2001 and March 2002. The mean (±SD) accumulation rate of marine debris was 77 ± 25 items/km/month, of a mean weight of 17.3 ± 12 kg. Forty different objects were collected and the five most frequent items were cotton fabric, string, polystyrene packing sheet, plastic packing tape and broken plastic pieces. The debris on Volunteer Beach was dominated by fishing debris; 42% of the items were discarded fishing equipment, while 39% of the items were of a packaging or associated nature. The mostly likely source of this household waste was fishing vessels, with Falkland Islands Government (FIG) fisheries observers seeing 27 of the 40 items of debris collected from Volunteer Beach being discarded from fishing vessels. It is suggested that, although further marine debris research is warranted, more effective at-sea ship waste disposal regulations are required in Falkland waters to reduce environmental and economic threats both at the local and international level.     

北祁连东段及其邻区地震滑坡的基本特征和危险区预测

本文根据野外调查和航片解译，研究了北祁连东段及其邻区地震滑坡的基本特征和形成条件，探讨了地震滑坡的动力机制，并在本区使用多因素模糊数学综合评判方法预测滑坡危险区。     

兰州马衔山北缘断裂地震潜势评估

马衔山北缘断裂为晚第四纪活动的左旋逆走滑断裂,是对兰州市影响最大的控震断裂,自东向西可分为内官营段、马衔山段、七道梁段和雾宿山段4条次级断层段.其中雾宿山段为1125年兰州7级地震的发震断层段,其特征地震平均复发间隔为2 250～3 590年,最晚离逝时间为882年,在未来关注的200年内再次发生强震的可能性较小;马衔山段特征地震平均复发间隔约为3 120年,历史上曾发生过多次中等破坏性地震,其潜在地震危险性值得关注;七道梁段和内官营段未获得古地震复发间隔等参数,但历史上均发生过中等破坏性地震,未来仍存在中等破坏性地震发生的可能,其地震复发间隔可近似地参考马衔山断裂带上相应震级地震的平均值.     

Development of a seismic damage and loss scenario for contemporary and historical buildings in Thessaloniki, Greece

The methodologies used in Greece for estimating direct losses in both reinforced concrete (R/C) and masonry buildings (also including monuments) are summarised, the critical issue of data collection is addressed, and practical solutions that have been tried are discussed. The development of a seismic risk scenario for contemporary and historical buildings in Thessaloniki is then presented and some key results are given, including the expected geographical distribution of building damage (due to the scenario earthquake) in the municipality of Thessaloniki; damage is described both in structural and in economic terms.     

Risk-based drought early warning system in reservoir operation

This paper introduces a risk-based decision process integrated into a drought early warning system (DEWS) for reservoir operation. It is to support policy making under uncertainty for drought management. Aspects of posterior risk, chances of option occurrences and the corresponding options to given chances, are provided to help decision makers to make better decisions. A new risk index is also defined to characterize decision makers’ attitudes toward risk. Decision makers can understand the inclination of attitude associated with any specific probability through accuracy assessment, and learn to adjust their attitudes in decision-making process. As a pioneering experiment, the Shihmen reservoir in northern Taiwan was tested. Over the simulation period (1964–2005), the expected overall accuracy approximated to 77%. The results show that the proposed approach is very practical and should find good use for reservoir operations.     

A risk assessment model for produced water discharge from offshore petroleum platforms-development and validation

Produced water discharge accounts for the greater portion of wastes arising from offshore oil and gas production operations. Development and expansion of Canada’s offshore oil and gas reserves has led to concerns over the potential long-term impacts of produced water discharges to the ocean. To examine this emerging environmental issue at a regional scale, an integrated risk assessment approach was developed in this study based on the princeton ocean model (POM), a random walk (RW) and Monte Carlo simulation. The use of water quality standards arrayed in a Monte Carlo design in the developed approach has served to reflect uncertainties and quantify environmental risks associated with produced water discharge. The model was validated against field data from a platform operating off Canada’s east coast, demonstrating its usefulness in supporting effective management of future produced water discharge.