Construction risks of Huaying mount tunnel and countermeasures
The Chongqing-Guang’an motorway is planned to cross Huaying mount at Jingguan town of Chongqing city. The whole mount is a colossal anticline whose core is consisted of coal measure strata (upper Permian Longtan formation P l) and the limbs are limestone strata (middle Triassic Leikoupo formation T l and lower Triassic Jialingjiang formation T j). The tunneling is full of risks of collapse, gas explosion or gas outburst, water (mud) inrush, gas inrush because of existence of faults, high pressure gas, karst tectonics and coal goafs around the tunnel. In order to cope with the high risk, two main countermeasures were taken to ensure security of construction. One is geology prediction, and the other is automatic wireless real-time monitoring system, which contains monitoring of video, wind speed, poisonous gas (CH , CO, H S, SO ), people location, and automatic power-off equipment while gas contents being more than warning threshold. These ascertained the engineering safety effectively.