Stability assessment of volcanic natural caves - Lava tunnels - Using both empirical and numerical approach, case studies of Galapagos Islands (Ecuador) and Lanzarote Island (Canary - Spain)

Abstract:

Lava tunnels are natural caves in volcanic basalt rocks originated by the differential cooling between the center and the outside of a Pahoe-oe lava flow. These caves are visited by many tourists around the world and there are few studies that assess the Factor of Safety. In the present study the stability of some of the most representative and visited tunnels in Galapagos and Lanzarote is assessed. Special emphasis is done in show caves in the islands of Santa Cruz and Isabela and the Canary island of Lanzarote. It has been used an empirical methodology - internationally accepted for tunnels and underground works for the stability analysis, combining geomechanical classifications, in particular the index Q with numerical methods - finite elements by Phase2 program. Accessible caves have been visited, some of which are totally stable and others have some signs of instabilities. The goal-output end of the investigation is to represent each of the cavities and sections by a point on a graph (size cave and rock quality) different if these are stable or unstable. A separation line (based on empiricism) between stable and unstable or collapsed caves is established. The line of separation of the domains corresponds to a Factor of Safety - FoS - equal to 1. We have also chosen ten of the most significant caves for analysis using finite elements and check which is the minimum FoS of each one.

Año de publicación:

2016

Keywords:

Fuente:

scopus