京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18569号 / 工博第3930号 / 新制||工||1604(附属図書館) / 31469 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 清野 純史, 教授 三村 衛, 准教授 古川 愛子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The thesis is focused on the issue of black swans in the water structure. More detail risks and hazard dam. History has shown us that sophisticatedly structure as dam is not perfect. Failure can cause weather, natural disaster, bad chance or deliberate attack. A detailed analysis of the current situation, I mapped historic dam failure, which can cause black swan. In thesis is a reseach on knowledge of the population in this issue. Based on the analysis and obteined information was proposed measures to improve the situation.

Catastrophic events such as dam failures or severe floods are considered to be of low probability, although their consequences can be extremely high and might include loss of life. Earlier studies have linked circumstances surrounding historical darn failure events to actual loss of life and produced formulations using statistical analysis of these events. Shortcomings of these methods include the inability to adjust life-loss estimates based on the type of darn failure, global averaging of population at risk, and ignoring the dynamics of the evacuation process. The main objective of this research is to develop a practical and improved life-loss estimation approach for use in dam safety risk assessment and emergency planning. The methodology is specifically formulated to overcome the limitations of previous. purely empirical, approaches. The approach takes into account the spatial and temporal distribution of flood water depth and velocity, fate of buildings, simulation of warning diffusion, and tracking the movement of people from their original location towards safe shelters. The model created, called LlFESim, is designed to serve multiple function s. First, it can be used in a Deterministic Mode using best estimate inputs to obtain point estimates, or to test different policies for evacuation as well as different times of the day and for different dam breach flooding scenarios. Second, the Uncertainty Mode represents input and parameter uncertainties to provide estimates of life loss, and other variables relating to warning and evacuation effectiveness, as probability distributions. These distributions of life loss can be combined with estimates of the uncertainties in other risk assessment inputs, to obtain estimates of uncertainties in risk assessment results, including evaluations against tolerable risk guidelines. Two communities were used to demonstrate the model performance. Deterministic Mode results display the various possible model outputs. Sensitivity analysis for the Deterministic Mode shows that the effect of warning issuance time is the dominant factor in the estimated life loss. However, other factors play an important role such as the time of day, effectiveness of the warning system, and shelter location. Uncertainty Mode results demonstrate the effect of uncertainties in model parameters and inputs on the model results.

Seepage-related erosion is one of the predominant mechanisms responsible for incidents and failures of dams and levees. Current geotechnical engineering practice consists of comparing expected exit gradients with the critical gradient of the soil at the seepage exit point. The critical gradient is generally considered as the ratio of soil buoyant unit weight and the unit weight of water, suggesting that the critical gradient only depends on the void ratio and specific gravity of the solids. However, in the field and in research, it has been observed that piping can initiate at average gradients much lower than unity due to concentrations in flow and non-vertical exit faces. Therefore, there is a need for deeper understanding of the granular scale mechanisms of the piping erosion process. This thesis presents the results of a laboratory study to assess the effects that soil properties and exit face configurations have on the potential for initiation of piping and the piping mechanisms. By using a laboratory device designed and constructed specifically for this study, the critical gradients needed to initiate piping in a variety of sandy soils were measured to assess the effects that parameters such as gradation, grain size, and grain shape have on the critical gradients. The tests are also used to observe the grain scale mechanisms of piping erosion initiation. The ultimate goal of the study is to develop an empirical, but mechanism-based, grain-scale model that can take into account the effects of converging flows, non-horizontal exit faces, and soil properties while assessing the potential for piping erosion to occur.

Introduktion: Dammbrott är en olycka som har en låg sannolikhet att ske men om den skulle inträffa ha katastrofala konsekvenser. Ett område som skulle drabbas vid ett dammbrott i Luleälven är Luleå kommun som ligger i mynningen av Luleälven. För att områden som anses vara av risk skulle kunna utrymma i tid innan vattennivåerna stiger är det av vikt att individen dels förstår varningsmeddelandena samt förstår vilket ansvar den har vid en utrymning. Kunskapen om varningar och vilket ansvar individen har vid dessa visar tidigare forskning på som låg. Syftet med studien var att få kunskap om vilken förståelse det finns hos individer gällande varningssystem vid ett dammbrott och vilken syn som finns på ansvarsfördelningen i utrymningsprocessen. Studien syftade även till att identifiera vilka hinder och möjliggörande faktorer som kan påverka individen vid en utrymning.  Metod och material: Studien följde en fallstudiedesign med mixade metoder som antog en deduktiv ansats. Den kvalitativa datainsamlingen innefattade semistrukturerade intervjuer med tjänstepersoner vilket baserade på ett avsiktligt urval, som arbetar inom krishantering. Den kvantitativa datainsamlingen skedde i form av webbenkäter, vars urval baserades på ett bekvämlighetsurval där individer som bodde i ett riskområde och var över 18 år, kunde svara på enkäten som skickades ut i Facebook-grupper för de boendeområdena som ansågs vara av risk. Analysen av datamaterialet skedde dels genom en deduktiv kvalitativ innehållsanalys där respondenternas svar analyserades utifrån tidigare förutbestämda kategorier. Det kvantitativa materialet analyserades utifrån både univariata och bivariata analyser samt tolkning av fritextsvar.  Resultat: Studien påvisade en gemensam bild kring att individer har en god förståelse kring vad varningssystemen innebär samt lämpliga handlingar därefter. Dock fanns en skillnad mellan åldersgrupperna där de yngre grupperna i större utsträckning inte vet vad de ska göra om varningssystemen larmar. Gällande ansvar fanns det även här en liknande bild där kommunen har ett stort ansvar i en utrymningssituation samt framfördes det att individen har ett ansvar, främst från respondenternas sida. En möjlighet som framkom var bland annat broschyren som skickades ut och många individer ansåg att den hade hjälp dem förstå vad de skulle göra vid ett dammbrott. Ett hinder som identifierades i samband med detta är att broschyren numera ligger på kommunens hemsida vilket innebär att personer som flyttar in till kommunen vare sig får kunskap om risken eller vad en ska göra om ett dammbrott sker.  Slutsatser: Sammanfattningsvis visar resultatet en liknande syn på kunskapen om varningssignalen samt lämpliga handlingar därefter både utifrån ett individ- och tjänstemannaperspektiv. Angående ansvaret att utrymma behövs vidare forskning då det behövs mer tillförlitlig data från ett individperspektiv. Framtida studier bör fokusera på åldersperspektivet med avseende på kunskapen och handling vid varning men också på de hinder som studien har identifierat. / Introduction: A dam failure is an accident with a low probability to occur but the consequences would be catastrophic. One area that would be affected if a dam failure would occur in Luleälven is the municipality of Luleå which is located at the estuary of Luleälven. To get individuals that live in areas that are regarded of risk, if a dam failure would occur, to evacuate in time before the water levels rise it is of importance that individuals understand the warning and the responsibility of the individual. The aim of the study was to develop a further understanding of the knowledge individuals have regarding the warning systems that would be used in the event of a dam failure, but also the view about the responsibilities in an evacuation process. The study also aims to identify obstacles and enabling factors that may impact the individual if an evacuation would be necessary.  Methods and material: The study had a case study design with mixed methods. The qualitative data collection included semi structed interviews with government officials who works with crisis mangement, which was based on a purposive sampling. The quantitative data collection was in the form om web surveys which used a convenience sampling that included individuals that lived in an area of risk and were older than 18 years. If the individual met the criteria for the data collection they were eligible to answer the web survey that was distributed in different Facebook groups for the different areas that were considered being of risk. The analysis method for the qualitative material was done through a deductive qualitative content analysis and the respondents answers were analyzed from predetermined categories. The quantitative material was analyzed with both univariate and bivariate analysis, and also interpretation of free text answers.  Results: The results showed a common view in regards that individuals have a good understanding of the warning systems and also appropriate actions thereafter. On the other hand, there was an age difference were the younger age groups in a greater extent do not know the appropriate action if the warnings systems go off. With regards to responsibility there is a mutual understanding of the municipality as to having a big responsibility during an evacuation. The individuals responsibility to evacuate was also put forward, mostly from the government officials. An enabling factor to evacuate was the brochure that was sent out a couple of years ago. Many individuals explained how the brochure had helped them understand what the appropriate actions in the case of dam failure. An obstacle that was identified in connection to this was that the brochure is only available on the municipality’s web site, which implies that people moving into the municipality neither get the knowledge about the risk or the appropriate actions if a dam failure would occur.  Conclusion: To conclude, there are similar views regarding the knowledge of the warning system and proper action in response to the warning, both from an individual and officials’ perspective. How the individual perceive their responsibility to evacuate is in need of further research since there is a lack of data from an individual’s perspective. Further research should focus on an age perspective with regards to the knowledge of warning system and action, and also concerning the barriers that have been identified in the study.