Simulation of fire-induced spalling and damage behaviors in granite rock caverns in Hong Kong using thermo-mechanical coupling phase field method

Abstract

Since the 1980s, the Hong Kong Government has been exploring the construction of rock caverns as a sustainable solution to alleviate land scarcity. Fire safety remains a paramount concern in the operation of underground rock caverns. Fires not only pose significant risks to personnel evacuation and firefighting intervention but also present substantial challenges for post-disaster repair and fire-resistant design for these caverns. Granite formations, which are very common in Hong Kong, are favorable for housing caverns. However, both the granite and its supporting concrete lining in cavern may experience significant mechanical degradation when subjected to high temperatures. To investigate the thermo-mechanical coupling response of rock caverns under fire scenarios, we employed the phase field method (PFM) to simulate a project in Hong Kong. This work explores the heated spalling fracturing and damage behaviors of the lining and surrounding rock under various conditions involving fire scenarios, cavern burial depths, rock stiffness, and presence of rock bolts. The results indicate that the failure of the lining and rock is affected by the fire scenario on the fire-exposed surface, while the burial depth and rock stiffness have minimal impact. Rock bolts can effectively reduce the deformation of intact rock formations which are not subjected the high temperature penetration.