Engineering geological characteristics, failure modes and protective measures of Longyou rock caverns of 2 000 years old.

The Longyou rock caverns are a group of large ancient underground caverns in Zhejiang, China, which were manually caved in pelitic siltstone in the Quxian Formation of the Upper Cretaceous more than 2 000 years ago. They were discovered by local farmers during drainage of pools in 1992. An investigation was carried out into the geological setting, hydrogeological conditions, water seepage and fracture in caverns that have maintained their integrity and the failure modes in the failed caverns. Many fractures have developed in the intact caverns since 1992, and their distribution is consistent with the failure characteristics of the failed caverns. Protective measures are discussed for the five intact caverns, including roof reinforcement, using pillars and beams, reinforcement of rock pillars and common sidewalls between caverns, waterproofing and installation of a monitoring system.
The Longyou rock caverns are a group of large ancient underground caverns in Zhejiang, China, which were manually caved in pelitic siltstone in the Quxian Formation of the Upper Cretaceous more than 2 000 years ago. They were discovered by local farmers during drainage of pools in 1992. An investigation was carried out into the geological setting, hydrogeological conditions, water seepage and fracture in caverns that have maintained their integrity and the failure modes in the failed caverns. Many fractures have developed in the intact caverns since 1992, and their distribution is consistent with the failure characteristics of the failed caverns. Protective measures are discussed for the five intact caverns, including roof reinforcement, using pillars and beams, reinforcement of rock pillars and common sidewalls between caverns, waterproofing and installation of a monitoring system.