ASSESSMENT OF LIQUEFACTION CONSEQUENCES FOR NUCLEAR POWER PLANT PAKS (original) (raw)
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Safety Assessment of Nuclear Power Plants for Liquefaction Consequences
In case of some nuclear power plants constructed at the soft soil sites, liquefaction should be analysed as beyond design basis hazard. The aim of the analysis is to define the postevent condition of the plant, definition of plant vulnerabilities, and identification of the necessary measures for accident management. In the paper, themethodology of the analysis of liquefaction effects for nuclear power plants is outlined.The procedure includes identification of the scope of the safety analysis and the acceptable limit cases for plant structures having different role fromaccident management point of view. Considerations are made for identification of dominating effects of liquefaction.The possibility of the decoupling of the analysis of liquefaction effects from the analysis of vibratory ground motion is discussed. It is shown in the paper that the practicable empirical methods for definition of liquefaction susceptibility provide rather controversial results. Selection of method for assessment of soil behaviour that affects the integrity of structures requires specific considerations. The case of nuclear power plant at Paks, Hungary, is used as an example for demonstration of practical importance of the presented results and considerations.
Methods and Uncertainties in Liquefaction Hazard Assessment for Nuclear Power Plants
2014
Experience shows that the nuclear power plant can be safely designed for vibratory effects of earthquakes. Contrary to this, the plants can be heavily damaged by effects of earthquake-induced phenomena like tsunami, soil liquefaction after surviving the ground shaking effects. In the paper, the problems in nuclear power plant’s safety analysis methodology are outlined for the case of soil liquefaction. Depending on the applied method, the liquefaction hazard assessment may provide very scattering results and might lead to controversial conclusions. In the paper different approaches and methods for liquefaction hazard assessment are considered. Practical problems of the selection of appropriate methods are demonstrated on the example of Paks Nuclear Power Plant, Hungary. For comparison, records of one SPT, one CPT and one shear wave velocity measurement, that were located very close to each other, were chosen from the site and the liquefaction potential was assessed by altogether nin...
Vulnerability of Industrial Components to Soil Liquefaction
Chemical Engineering Transactions, 2014
Dynamic liquefaction of saturate loose sand deposit is a common geotechnical failure effect caused by an earthquake, which can lead to structural damage of buildings, lifelines and industrial components in general. Several damage cases have been observed in past events and have been documented in the technical literature and post-earthquake reconnaissance reports. Failure and malfunctioning of pipelines, tanks and wastewater treatment plants, induced by differential vertical settlements, horizontal lateral spread and uplift of underground structures, are described. All these permanent displacements could be directly related to co-seismic liquefaction of the foundation soil. Moreover, this failure mechanism is strongly site dependent and the abovementioned effects frequently occurred in coastal and fluvial plane areas, where industrial plants are often situated. The paper studies and compares the behaviour of some important industrial components during the liquefaction event. Empirical fragilities and threshold values were evaluated on the basis of the significant seismic parameter, accounting for the possible hazardous effects of the release of toxic and flammable fluids. These tools could be assessed by means of a comparison with similar ones proposed by current building codes and implemented in existing software for the risk assessment of industrial plants and lifeline networks.
Clayey silty up to silty sandy and sandy soils are generally recognized to have a significant liquefaction potential when extended submerged below water table. This phenomenon raises a major concern to the foundation and structural engineer. Low plasticity silts, silty clays and silty sands occur extensively as recent alluvial deposits in the southern coastal region of Elefsina Municipality in Attica Prefecture, Greece. In this area, a Combined Cycle Gas Turbine (CCGT) Power Plant is planned to be constructed and its foundation stability and durability reassurance is of utmost importance to structural engineers. In the study of the geotechnical ground investigation for the foundation design of the CCGT project, a number of field and laboratory tests were carried out. For evaluating its foundation soil liquefaction potential and risk during an earthquake, some internationally accepted guidelines are available based on soil density, void ratio, plasticity index, standard penetration test values, and other simple soil properties. The liquefaction behavior and potential of this kind of foundation soils stratified in the alluvial deposits has been studied thoroughly based on both Seed's and Idriss's procedure / relationships as well as Prakash's limit state methodology, using S.P.T. results and an algorithm program / software code, that was developed and published by the author. The S.P.T. tests were executed inside the twenty investigation-sampling boreholes of a depth range from 10 up to 50 meters each one, in an 100.000 s.m. plot, where a Combined Cycle Gas Turbine (CCGT) Power Plant is planned to be constructed. According to the results of these analyses and assessments the well documented and argued necessity is deduced either for transferring the project foundation loads to underlying deeper and more competent bearing strata and layers, or for strengthening, geotechnically upgrading (ground improvement), stabilizing and cement grouting the foundation ground of the CCGT Power Plant using jet grouting piles techniques. Finally, the exact depth range under the CCGT Power Plant foundation site that is prone and dangerous to be liquefied in the event of a strong seismic shock and vibration was determined and diagrammatically presented and the remedial measures to be taken were suggested. Hence, in this way the liquefaction risk can be mitigated or even deterred from the incompetent upper natural soil layers of the project foundation ground.
The 1999 earthquakes (which had magnitudes Mw of 7.4 and 7.2) in Turkey caused great destruction and damage for Yalova (Turkey) sites in the Marmara Region. In the investigation area, the mainly reason for destruction is the liquefaction. As it is known, liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. In the frame of this research, probabilistic and deterministic analyses were used to determine the safety factors for several parameters. For the study area, the probabilistic seismic hazard analysis showed very high seismic activity. By using deterministic seismic hazard analysis, the magnitudes were estimated for the three rupture (with four different fault lengths, 109, 120 and 174 km) model of North Anatolian Fault Zone in the Marmara Region. By using analysis (deterministic and probabilistic), estimated magnitudes and accelerations of earthquake were taken as alternatively 6.5, 7.0 and 7.5 for magnitudes and from 0.2 -0.50 g for accelerations. For several design earthquake parameters, cyclic stress analysis of liquefaction were applied to the field data (both SPT (N) and S wave data), obtained in the Yalova region. In the first phase of the study of liquefaction, the cyclic stress ratio approach was applied for all data to analysis of soil liquefaction. Then FS (factor of safety) values of liquefaction were estimated with this approach.
3 Review on Liquefaction Hazard Assessment
2020
Advances in Geotechnical Earthquake Engineering-Soil Liquefaction and Seismic Safety of Dams and Monuments 64 temporarily lose shear strength and behave more as a viscous liquid than as a solid. The water in the soil voids exerts pressure upon the soil particles. If the pressure is low enough, the soil stays stable. However, once the water pressure exceeds a certain level, it forces the soil particles to move relative to each other, thus causing the strength of the soil to decrease and failure of the soil follows. During earthquake when the shear wave passes through saturated soil layers, it causes the granular soil structure to deform and the weak part of the soil begins to collapse.
E3S Web of Conferences
Liquefaction is a hazardous and temporary phenomenon by which water saturated soil loses some or all of its resistance. The undrained conditions linked to the cyclic load increase the pores water pressure inside the soil and consequently reduce effective stress. As a result, the soil can no longer resist or hold the shear forces, and lead to enormous deformations that directly influence the stability of structures and infrastructures foundations. Since 1964, several semi-empirical methods have been invented to evaluate the liquefaction potential using the in-situ test results. This study is based on the correlation between experimental data results of Menard pressuremeter and SPT dynamic penetrometer tests. Samples used in this test come from the Rhiss dam located in the North of Morocco, 24 kilometers as the crow flies from the town of Al Hoceima and south of the foundations of a calcareous ridge. The studied area have high seismic activity and a high percentage of fine soil elemen...
Arabian Journal of Geosciences, 2012
Paying special attention to geotechnical hazards such as liquefaction in huge civil projects like urban railways especially in susceptible regions to liquefaction is of great importance. A number of approaches to evaluate the potential for initiation of liquefaction, such as Seed and Idriss simplified method have been developed over the years. Although simplified methods are available in calculating the liquefaction potential of a soil deposit and shear stresses induced at any point in the ground due to earthquake loading, these methods cannot be applied to all earthquakes with the same accuracy, also they lack the potential to predict the pore pressure developed in the soil. Therefore, it is necessary to carry out a ground response analysis to obtain pore pressures and shear stresses in the soil due to earthquake loading. Using soil historical, geological and compositional criteria, a zone of the corridor of Tabriz urban railway line 2 susceptible to liquefaction was recognized. Then, using numerical analysis and cyclic stress method using QUAKE/W finite element code, soil liquefaction potential in susceptible zone was evaluated based on design earthquake.
Soil Liquefaction and Risk Analysis From in Situ Tests for the City of Trapani (Italy)
2001
The paper deals with a microzoning criterion based on CPT data to define liquefaction risk of the city of Trapani, Sicily (Italy). Zonation for liquefaction is a timdamental issue to prevent from seismic disasters since, as lessons of past earthquakes teach, liquefaction of sandy soils has been a major cause of damage to buildings. For the evaluation of the seismic risk of the municipal area of Trapani it has been chosen a scenario earthquake which may represent a possible repetition of the 1968 event. For this earthquake a Richter magnitude M= 6.0 and a maximum ground acceleration a,-= 0.3Og have been estimated. While new tools and refinements continue to be developed on the subjects of pore pressure build-up due to earthquake shaking and of liquefaction triggering, reliable evaluation methods already exist for liquefaction microzonation purposes. This study focuses on the application of a method for the evaluation of the liquefaction potential to several sites of the city of Trapani, by means of relationships between liquefaction resistance and corrected cone penetration tests (CPT) resistance.