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

Abstract

The authors were concerned 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. In addition, some model tests using a breakable model material were performed to evaluate dynamic response and failure mode. 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.