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71.
Nikolaos Tavoularis Ioannis Koumantakis Dimitrios Rozos Georgios Koukis 《Geotechnical and Geological Engineering》2018,36(3):1491-1508
This paper presents an application of the rock engineering system (RES) in an attempt to assess the proper landslide parameters and estimate the instability index, using two disastrous landslides in Greece which took place in Panagopoula (1971) and Malakasa (1995). RES has been developed by Hudson (Rock engineering systems: theory and practice. Ellis Horwood Limited, 1992) to determine interaction of a number of parameters in rock engineering design and calculate instability index for rock slopes. In this paper, an attempt is made to prove, how RES can be implemented in large-scale instability areas where natural slopes are associated with a variety of geomaterials (soils, rocks, weathering mantle, etc.), by selecting each time the most appropriate parameters that are relevant to the ad hoc potential slope failure and which can be quantified easiest than those of time and money consuming ones. RES approach allows the utilization of those parameters which are particularly active at the site, evaluates the importance of their interactions, taking into account the particular problems at any investigated site. The instability index for both study areas were calculated and found 89.47 for Panagopoula site and 81.59 for Malakasa (out of 100). According to the classification for landslide susceptibility by Brabb et al. (Landslide susceptibility in San Mateo County, California, 1972), both the examined case studies are classified as landslides, approving their existence as two serious slope failures. Thus, RES could be a simple and efficient tool in calculating the instability index and consequently in getting the prognosis of a potential slope failure in landslide susceptible areas, for land use and development planning processes. 相似文献
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Heidi Turpeinen Andrea Hampel Tobias Karow Georgios Maniatis 《Earth and Planetary Science Letters》2008,269(1-2):230-241
Field investigations suggest that postglacial unloading and rebound led to the formation or re-activation of reverse faults even in continental shields like Scandinavia. Here we use finite-element models including a thrust fault embedded in a rheologically layered lithosphere to investigate its slip evolution during glacial loading and subsequent postglacial unloading. The model results show that the rate of thrusting decreases during the presence of an ice sheet and strongly increases during deglaciation. The magnitude of the slip acceleration is primarily controlled by the thickness of the ice sheet, the viscosity of the lithospheric layers and the long-term shortening rate. In contrast, the width of the ice sheet, the rate of deglaciation or the fault dip have an only minor influence on the slip evolution. In all experiments, the slip rate variations are caused by changes in the differential stress. The modelled deglaciation-induced slip acceleration agrees well with the occurrence of large earthquakes soon after the melting of the Fennoscandian ice sheet, which led to the formation of spectacular fault scarps in particular in the Lapland Fault Province. Furthermore, our model results support the idea that the low level of seismicity in currently glaciated regions like Greenland and Antarctica is caused by the presence of the ice sheets. Based on our models we expect that the decay of the Greenland and Antarctica ice sheets in the course of global warming will ultimately lead to an increase in earthquake frequency in these regions. 相似文献
74.
Nicos Kalapodis Georgios Zalachoris Olga-Joan Ktenidou Georgios Kampas 《地震工程与结构动力学》2023,52(1):147-163
With a new era emerging in the field of lunar exploration and habitation, there is a need for research on structural forms made of local soil material (regolith), which will be able to endure the extreme conditions in harsh environments (e.g., extreme temperature fluctuations, solar and cosmic radiation, meteor showers, strong ground motions, etc.). The present work focuses on understanding the dynamic and seismic behaviour of certain structural typologies of monolithic arches by means of finite element analysis (FEA). These typologies were extensively investigated previously, using static analyses accounting for the reduced gravitational field on the moon, and proved to be of the optimum shape against certain loading scenarios. Specifically, these optimal monolithic arch forms (named enhanced varying-thickness arches – EVTAs) examined herewith, are described by varying-thickness geometry, properly enhanced at certain weak points for increasing their structural stability. Aiming at a fair comparison, the seismic behaviour of EVTAs is contrasted to that of their corresponding monolithic constant-thickness (CTAs) counterparts (having the same amount of structural material). After defining an appropriate damage state, the authors conduct preliminary pushover analyses to determine the structural capacity of the arches against lateral loading. Subsequently, the modal analysis of the EVTAs shows that the second/vertical mode exhibits a natural period almost equal to that of their first/translational mode and substantially longer than the corresponding second/vertical mode of their CTA counterparts, indicating a potential vulnerability along the vertical excitation. Furthermore, taking into account that shallow moonquakes are comparable to intraplate earthquakes in terms of hazard potential, the authors produce sets of stochastic seismic excitations used as time histories for seismic analyses. The probability of exceedance of the defined damage state as a function of the peak ground acceleration (PGA) is presented through indicative fragility curves, where the structural superiority of EVTAs against their CTA counterparts is demonstrated. 相似文献