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Natural Events: Seismic And Geotechnical Aspects
Published in Maurizio Cumo, Antonio Naviglio, Safety Design Criteria for Industrial Plants, 2019
Plate tectonic theory2 explains the mechanism of the strain energy accumulation. According to this theory, the lithosphere is made up by plates that continuously change and move independently from the others (Figure 1). The plates slide away from the mid-ocean ridges, where dense magma from earth interior creates new matter, while the old matter dives back where an oceanic plate collides with the edge of a continental plate, sinking below it. At the edges of the plates, where they collide or move along in opposite direction, tectonic forces strain the crustal rock. If the strength of the rock is overcome, then the rock breaks, coming back to its unstrained shape, and the elastic rebound generates seismic waves.3 The failure takes place on the weak point of the crust, generally where a discontinuity of the rock (a fault) already exists, and propagates from it. The point, where is the first release of energy, is called “hypocenter” and its projection at the ground surface is called “epicenter”.
Cascading process systems
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Of course, large-scale denudation is accompanied by crustal responses which complicate calculations of rates of relief reduction. Such responses involve either the release of elastic compression or isostatic recovery. Erosion and unloading of compressed elastic rocks, such as mica-rich granite or mica schist or overconsolidated sedimentary rocks, leads to elastic rebound. In the former rocks this results in the development of exfoliation joints which affect surface form (as in the Sierra Nevada of California) and allow for more effective local erosion, such as may occur in the overdeepening of cirques, glacial troughs and fjords by ice scour. An example of the elastic rebound of valleys cut in over-consolidated clay-shales, siltstones and sandstones following the removal of 610 m (2000 ft) of overlying sediments by erosion during the Tertiary and Pleistocene has occurred in central Alberta, where upwarping of 6 m of the floors of 62–123-m-deep valleys is common (i.e. 3–5 per cent of valley depth) and as much as 10 per cent has been recorded.
Movement monitoring
Published in Duncan C. Wyllie, Rock Slope Engineering, 2017
When a slope is first excavated or exposed, a period of initial response occurs as a result of elastic rebound, relaxation and/or dilation of the rock mass due to changes in stress induced by the excavation (Zavodni, 2000). This initial response will occur most commonly in open-pit mines, where the excavation rate is relatively rapid. In comparison, the exposure of slopes by the retreat of glaciation or gradual steepening of slopes due to river erosion at the toe will occur over time periods that may be orders of magnitude longer than that of mines. However, the cumulative strain of such slopes can be considerable. Elastic rebound strain takes place without the development of a definite sliding surface, and is likely the result of dilation and shear of existing discontinuities within the rock mass.
Seismicity pattern of African regions from 1964–2022: b-value and energy mapping approach
Published in Geomatics, Natural Hazards and Risk, 2023
Alemayehu Letamo, Kavitha B, Tezeswi TP
According to elastic rebound theory (Reid 1911), earthquakes are caused by the release of accumulated energy within fault raptures of rocks during sudden movements of tectonic plates. The distribution and mechanism of active faults, which are the source of significant seismicity, are crucial in seismicity studies. The map of active faults was recently compiled by Styron and Pagani (2020) under the project ‘The GEM Global Active Faults Database’. Figure 1 shows the mechanism of faulting for North Africa. It demonstrates that convergent northern Africa is subject to reverse faulting, and the formation of sizable thrust systems and orogenic belts (the Atlas and Betic/Rif chains) is primarily to responsible for the continent’s seismic activity. Diverging borders, however, show typical faulting (dextral and sinistral). It can be observed from Figure 2, that the East African rift system is now experiencing typical faulting in that it is a developing divergent tectonic plate boundary. Large earthquakes of various sizes have been recorded in historical and current times in the region around the triple intersection (Afar triangle). The area is dominated by normal faulting, according to the region’s surface geology and the focal mechanisms of earthquakes (e.g. Kebede and Kulhánek 1991; Ayele 2002), which is in line with current worldwide analyses of active faults by Styron and Pagani (2020).
Investigation of the Leeb hardness test in rapid characterisation of rock cores with particular emphasis on the effect of length to diameter ratio
Published in International Journal of Mining, Reclamation and Environment, 2023
Sefer Beran Çelik, İbrahim Çobanoğlu , Tamer Koralay, Kazim Gireson
Although MA and LM are very-fine-grained carbonate rocks with similar mineral composition and textural properties, significant differences are observed on the hardness measurements. The hardness of MA was obtained to be lower than that of LM, and a considerable difference was observed in the results. The lower hardness values of MA can be associated with the highly porous structure. Pores of a rock material attenuate the elastic rebound energy, which is the basic principle of the Leeb hardness measurement, and this causes decrease in the measured hardness values. LB was defined as a very-fine-grained carbonate rock. It has mostly sparite components that are well interlocked. However, a slight change was observed in the hardness measurements on this group. Travertine (TA) is massive and exhibit no crystal forms in hand sample. The hardness of TA samples group was found to be lower than LB sample group. This situation can be associated with the partially porous structure of TA.
Developing an anisotropic material for Engineered Material Arresting System (EMAS) usage
Published in International Journal of Pavement Engineering, 2021
Elvis A. Castillo-Camarena, Ernie Heymsfield
Cook (1993) investigated a number of materials for their potential as an EMAS material: sand, clay, water beds and gravel. However, the structural behaviour of such materials is heavily dependent on climate conditions. Moreover, because of their loose granular arrangement these materials can generate foreign object debris (FOD) (Heymsfield and Halsey 2008, Xing et al. 2017). Consequently, low strength-cementitious materials with a crushing strength less than 207 kPa (30 psi) were considered as most suitable as an EMAS material. These low strength-cementitious materials crush under aircraft loads creating an interface between the EMAS and the aircraft tires, which produces horizontal drag forces on the aircraft undercarriage (Heymsfield and Halsey 2008). In addition, cementitious materials have known predictable stress–strain behaviour, are incombustible, and do not show elastic rebound (Heymsfield et al. 2012). Elastic rebound negatively impacts stopping distance since it acts on the rear section of the tire to propel the aircraft and therefore, increase stopping distance. Although cementitious EMAS are longer lasting than loosely placed materials, cementitious blocks are prone to water infiltration (Xing et al. 2017).