GEOTHERMAL CHARACTERISTICS OF QINGHAI-TIBET PLATEAU AND RISK ANALYSIS OF DEEP UNDERGROUND GEOTHERMAL HAZARDS FOR ONE MAJOR LINEAR PROJECT

The Qinghai-Tibet Plateau is characterized by complex geological structure that has many unfavorable geological phenomena such as suture zones, faults and hot spring outcroppings. The phenomena tend to produce local sources of abnormal high heat. The transport line runs across the Qinghai-Tibet Plateau and is influenced by coupled effects of obvious geothermal anomalies and large buried depth. Thus the railway is vulnerable to the threat of high geothermal disaster. In this study, geothermal distribution in the Qinghai-Tibet Plateau is first analyzed. Then, the high geothermal risks of some typical deep and long tunnels of the transport line are quantitatively assessed. The results show that the distribution of ground temperature over the Qinghai-Tibet Plateau varies both spatially and temporally. Generally, the ground temperature in the Qinghai-Tibet Plateau is higher in south and east than in north and west, and has been increasing in the past 50 years. Typical tunnels, such as the Zheduoshan tunnel and the Layue tunnel, are subject to high geothermal risks of different degrees. The risk of high geothermal in the Layue tunnel is higher than that in the Zheduoshan tunnel. The distribution of high risk area along tunnel is related to buried depth and geological structure. In geothermal anomaly areas, special geological structure is the main cause of high geothermal. Furthermore, the controllability of high geothermal risk is evaluated by comparing with domestic and foreign tunnels having similar engineering geology backgrounds. It is concluded that, with reasonable engineering measures, the high geothermal risks of the Zheduoshan and Layue tunnel of the transport line are generally controllable. Nevertheless, it is still needed to strengthen the scientific and comprehensive control of high geothermal risk during the whole life cycle of the transport line.