The stability assessment of karstic caves beneath Gushikawa Castle remains (Japan)

Regional Symposium of the International Society for Rock Mechanics: Rock Engineering in Difficult Ground Conditions - Soft Rocks and Karst, EUROCK 2009 -- 29 October 2009 through 31 October 2009 -- Dubrovnik, Cavtat -- 89361The authors have been involved with the stability problem of the karstic caves at Gushikawa Castle remains in Okinawa Island of Japan using different techniques available in rock mechanics and rock engineering. First, several rock classifications were used for the characterization of rock masses surrounding these karstic caves on the basis of geotechnical investigations. Then, some stability assessments of caves were carried out using empirical and analytical techniques. And then, two-dimensional elasto-plastic finite element analyses were carried out to check the present situation and the effect of filling these cavities as a counter measure. Following these stability assessment studies, three dimensional elasto-plastic static and dynamic analyses of the Gushikawa castle remains with two karstic caves were analyses under present natural state and filled state. Numerical analyses showed that filling the cavities would increase the safety of the natural rock structures. © 2010 Taylor & Francis Group, London

Experimental studies on the dynamic response and stability of some historical masonry structures in ryukyu archipelago

8th Asian Rock Mechanics Symposium, ARMS 2014 -- 14 October 2014 through 16 October 2014 -- -- 118520The authors have been recently involved with the restoration of the various historical masonary structures as well as static and dynamic stability assessment of some natural monumental rock structures. Furthermore, dynamic limiting equilibrium methods (D-LEM) as well as numerical methods used for stability assessment of these structures. The outcomes of these studies are presented and their implications on the stability of historical masonary structures in Ryukyu Archipelago under dynamic loads such as those induced by earthquakes are discussed. © 2014 by Japanese Committee for Rock Mechanics

An integrated study on the response of an arch structure above karstic caves at New Ishigaki Airport

14th International Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014 -- 22 September 2014 through 25 September 2014 -- Kyoto -- 107391The authors have undertaken some studies on the stability assessment methods for natural underground openings in Ryukyu limestone in Ryukyu Islands and arch structures built above these caves to prevent any possible damage to the runway. The authors carried out a series of computations using 2D and 3D numerical methods to check the stability assessment of natural underground openings with its protection arch structure. In this article, the authors would present the outcomes of the numerical studies and discuss their implications. © 2015 Taylor & Francis Group, London

Some considerations on yield (failure) criteria in rock mechanics

American Rock Mechanics Association46th US Rock Mechanics / Geomechanics Symposium 2012 -- 24 June 2012 through 27 June 2012 -- Chicago, IL -- 95262Every material in nature starts to yield after a certain stress or strain level, and rock or rock mass is a no exception. The terms of elasticity or visco-elasticity are replaced by the terms of elasto-plasticity or elasto-visco-plasticity once material behaviour deviates from linearity. The relation between total stress and strain or strain rate tensors can no longer be used and every relation must be written in incremental form. As a result, the constitutive laws are derived using some assumptions, which include yield functions. Therefore, several yield criteria are proposed for rocks. In this article, the authors compare and discuss the applicability of various criteria used in Rock Mechanics and point out their features and shortcomings in view of experimental results. It is shown that Hoek-Brown's criterion as one of best criteria is quite questionable in view of experimental results. Copyright 2012 ARMA, American Rock Mechanics Association

Response and stability of underground structures in rock mass during earthquakes

Underground structures are well known to be earthquake resistant. However, the recent earthquakes showed that underground structures are also vulnerable to seismic damage. There may be several reasons such as high ground motions and permanent ground movements. This study attempts to describe various forms of damage to underground structures such as tunnels, caverns, natural caves and abandoned mines during major earthquakes. Results of various model tests on shaking table are also presented to show the effect of ground shaking on the response and collapse of underground structures in continuum and discontinuum. Furthermore, some empirical equations are proposed to assess the damage to underground structures, which may be useful for quick assessments of possible damage. © 2010 Springer-Verlag

Dynamic response and stability of some historical masonry structures subjected to ground shaking

3rd International Conference on Rock Dynamics and Applications, ROCDYN-3 2018 -- 26 June 2017 through 27 June 2017 -- -- 220639Historical structures are mainly masonry structures, which are composed of blocks made of natural stones, bricks or both, and they are assembled in different patterns with or without mortar. The authors have been recently involved with the restoration of the famous Shuri Castle, Nakagusuku Castle, Gushikawa Castle, an arch bridge in Iedonchi Royal garden and Yodore Royal Mausoleum of the Ryukyu Imperial period as well as static and dynamic stability assessment of some natural rock structures such as Perry Banner Rock. The deterioration by atmospheric agents, bombing and seismic shaking damaged some of these structures. The recent earthquakes in Kumamoto also caused severe damage to historical masonry structures. The authors describes the outcomes of experimental, limiting equilibrium and numerical studies on the stability of historical masonry structures under dynamic loads such as those induced by earthquakes and their implications are discussed. © 2018 Tokashiki et al