川藏铁路康定隧址区地热水成因及其工程影响分析

An analysis of the genesis and engineering influence of geothermal water in the Kangding tunnel site of the Sichuan-Tibet Railway

川藏铁路康定隧址区穿越鲜水河断裂带,属地热异常区,对铁路建设造成一定的热害威胁。采用野外调查、水化学分析和氢氧同位素测试等技术方法,开展了川藏铁路康定隧址区地热水成因研究。结果表明,康定隧址区地热水水化学类型主要为HCO_(3)·Cl—Na和HCO_(3)—Na型,聚集于折多塘、康定和中谷3个热水区。地热水均为未成熟水,热储温度为104~172℃,深部初始地热水温度为186~250℃,冷水混合比例为0.56~0.81。氢氧同位素显示地热水补给高程为3768~4926 m。在康定隧址区,地热水受到高海拔水源补给,主体断裂构造为导热构造,次级分支断裂和发育节理、裂隙的断层破碎带为导水构造,地热水形成后沿浅部断层破碎带出露形成温泉。FEFLOW数值模拟分析表明研究区100 m深度地温场温度为35.4~95.1℃,研究区内三个热水区之间存在低温通道。隧道建设时应重点关注康定热水区的高温水热灾害。

The Kangding tunnel of the Sichuan-Tibet Railway crosses the Xianshuihe Fault Zone where geothermal abnormity occurs and is harmful for railway construction.This paper analyzes the genetic mechanism of geothermal waters through the integration of field survey,hydrochemical analysis and D-O isotopic experiments.The results show that HCO3·Cl—Na and HCO3—Na types are the main hydrochemical types of hot springs in the Kangding tunnel area,which exists in the Zheduotang,Kangding and Zhonggu geothermal areas.Geothermal waters are immature and the reservoir temperature ranges from 104℃to 172℃.Deep initial geothermal waters display the reservoir temperature of 186−250℃and are mixed by 56%−81%of cold water.Hydrogen and oxygen isotopes show that the recharge elevation of the geothermal water ranges from 3768 m to 4926 m.In the study area,geothermal waters are recharged by water source at high elevation.The main fault is the structure of thermal conductivity,and secondary faults and fracture zones are the channel of water migration.Geothermal waters arise and expose as hot springs on the land surface.Simulated geothermal field of 100 m has the temperatures of 35.4−95.1℃.Relatively low-temperature channel may be existed among three geothermal areas.High-temperature geohazard induced by geothermal water should be focused in the Kangding area during tunnel construction.