Seismic exclusions and re-entry from a risk perspective

Proceedings of the 8th International Symposium on Rockbursts and Seismicity in Mines, RaSiM8, 2013

The possibility of experiencing a seismic event resulting in fatalities has arguably become the most important financial risk in underground hardrock mines operating in developed countries. In the two most recent cases in Australia, the entire operation was shut down for a period well exceeding one year while the mining method had to be re-engineered in order to demonstrate to regulators that the seismic risks had been lowered to an acceptable level. The methods for mitigating seismic risk have developed significantly over the last couple of decades. The seismic risk is mitigated by reducing the seismic hazard through the implementation of sound geotechnical principals in mine design or through pre-conditioning practice, managing exposure of personnel and assets, and reducing the damage potential with dynamic resistant support. This paper reviews the risk mitigation techniques currently used in Australia, Canada and Sweden (A/C/S) with an emphasis on where and how the authors believe these techniques could be improved through future research and development.

Rock Mechanics and Rock Engineering, 2009

The problem of mining-induced seismicity in hardrock mines has become significant as underground mines from around the world are pushing production to deeper levels. At many mines, the risk associated with large seismic events and rockburst damage must be managed to ensure the safety of mine workers and minimise production losses. In this paper, an engineering approach to seismic risk management is described. It relies on accepted risk management techniques, which principally include the identification and understanding of hazards from which risk mitigation measures can be developed. This is achieved using simple but effective analysis techniques of high resolution microseismic data.

Journal of the Southern African Institute of Mining and Metallurgy, 2009

Earthquake Engineering emerged during the time from 1910 to 1930's, resulting with first building codes which included earthquake activities as loads. Seismic engineering need was triggered by devastating earthquakes in Northern California, and Messina -Italy. Since then, and especially during the last decades, earthquake engineering has increasingly advanced ever changing the norms and building codes. By now the preventive measures of earthquake risk mitigation have drastically evolved suggesting protection not only for new buildings, but also for the existing ones which make the majority of our surrounding built world.

The objective of this investigation is to improve worker safety through a better understanding of mine excavation response to rockbursts. The improved understanding should lead to improved mine layout and support design. The project is a continuation of GAP 201 and consists of two main enabling areas namely: a comprehensive investigation of rockbursts that have caused damage and posed a hazard to workers and measurement and analysis of the dynamic response of the rock surrounding excavations following seismic shaking.

Several accidents occurred in the last decades evidenced that the impact of seismic events in industrial plants may trigger accidental scenarios involving the release of relevant quantities of hazardous substances. Severe scenarios typical of the process industry, as fires, explosions, toxic releases, water pollution were reported as the consequence of seismic events in industrial areas. Although the severity of this kind of accidents, scarce attention was devoted to the assessment of risk due to major accidents triggered by seismic events and a comprehensive approach to risk assessment and emergency planning in industrial sites extended to include the possible external hazard factors is still needed. In the present study, a specific approach was developed for the assessment of local and societal risk indexes caused by accidental scenarios triggered by earthquakes. The approach allows the identification and the consequence assessment of all the possible scenarios that may follow the seismic events. The starting point of the procedure was the use of available historical data to assess the expected frequencies and the severity of seismic events. Simplified empirical vulnerability models (fragility curves) were used to assess the damage probability of equipment items due to a seismic event. The data on the frequency of the natural events have to be combined with the data of the equipment vulnerability, in order to calculate a release probability, indispensable to obtain the final risk value. The procedure was implemented in a GISbased software tool in order to manage the high number of event sequences that are likely to be generated in large industrial facilities. The developed methodology requires a limited amount of additional data with respect to those used in a conventional QRA. The application of the procedure to a storage plant sited in the Emilia-Romagna region evidenced that the scenarios initiated by seismic events may be important in the comprehensive assessment of industrial risk.

Knowledge and understanding of natural hazards is continually evolving. As a result, there is a need to reexamine the safety of nuclear facilities in the light of new knowledge and reassess the adequacy of original design bases. Department of Energy (DOE) nuclear facilities must comply with DOE Order 420.1C Facility Safety, which requires that facilities review their natural phenomena hazards (NPH) assessments at least every ten years. Re-evaluation programs have also been undertaken for nuclear power plants (NPPs) and significant post-Fukushima re-evaluation activities are underway in the United States (US). Once completed, all US NPPs will have updated seismic hazard information and a significant number will have completed seismic probabilistic risk analysis (SPRAs). Information from DOE facilities, new information on NPP capacity, and the maturing of probabilistic seismic hazard analysis (PSHA) and SPRA techniques provides a unique opportunity to develop a new, risk-informed framework that can be used to effectively address technical and regulatory questions that arise from new natural-hazard information. A risk-informed approach for re-evaluating seismic hazard and risk information for a broader range of facilities would benefit the NRC, DOE, the nuclear industry, and the public. It could also serve as a template for addressing a large suite of other natural hazards. BACKGROUND

Malaysian Journal of Science and Advanced Technology

Over 40% percent of the accidents encountered at Unki Mines are related to ground failure and other geotechnical complications. This research sought to address the monetary losses incurred in revenue and productivity through absenteeism and injury. With the development of mine production in Zimbabwe, the depth of mines gradually increased, and the ecological environment developed complex conditions. Deep mining unlike shallow mining is characterized by extra ground pressure, more gas, and faster deformation rates. These factors affect the safety of mining production. Therefore, as the mining depth and breadth increase, the difficulty of mine rock engineering is also increasing. The deepening of mining depth and the improvement of the mechanization level have brought increasing difficulties regarding the stability of surrounding rock hence risk issues arise. The ultimate objective of this study was to ensure a robust design of support systems at Unki Mine that would eventually reduce...

Recent developments in the field of risk acceptance criteria for structures are implemented in this contribution to derive cost-optimal safety measures against earthquakes in seismic regions. The methodology consists of four steps: a) Probabilistic representation of earthquake intensity: the random peak ground acceleration for a specific region or country is probabilistically evaluated as a function of its influencing parameters, i.e. source geometry, magnitude model (including uncertainty of the upper bound magnitude), occurrence rate, error term. b) Probabilistic assessment of the correlation between earthquake intensity and structural damage (vulnerability): results from recent earthquakes are included to present the damage probability matrix for several building classes; the associated model uncertainties are taken into account. c) Formulation of risk acceptance criteria based on the Life Quality Index LQI Approach: by using this approach an optimum acceptable cost per averted fatality (ICAF) can be derived for a specific country. d) Optimization of safety measures based on the aforementioned risk acceptance criteria: safety measures against earthquake such as preventive design (safety factors) or mitigation measures (rescue measures) can be optimized by comparing the relative measure costs to the aforementioned ICAF and by considering their risk reducing effectiveness (based on experience and risk analysis background). The applicability of the proposed procedure dealing with optimisation of safety measures against earthquake is presented herein and illustrated in an example. Conclusions for further developments are drawn.