隧道高地温的地质成因研究

Geological Genesis of Tunnel High Ground Temperature

为研究隧道高地温的地质成因,以云南某在建高速公路隧道——尼格隧道为研究对象,该隧道兼有高水温与高岩温,最高水温达63.4℃,最高岩温达88.8℃.从区域地质构造及地震特征、水化学特征、地热储特征等对区域性的热因控制、水源、热源、导热通道等进行了分析,利用氢氧同位素分析法、锶同位素分析法、微量元素分析法、放射性元素分析法等对隧址区的热水来源及演变过程、热源成因进行了研究,并结合隧道工程地质、水文地质条件及开挖揭示状况,对隧道高水温段及高岩温段的地质成因过程进行了剖析.研究结果表明:灰岩段高水温的成因过程与花岗岩段高岩温有所差异,隧道高水温的成因过程为热源(深部热异常体)—主要传热通道(深循环)—次级传热通道—浅表水体混合、水岩作用,其过程伴随着冷热水混合作用、离子交换作用等;隧道高岩温的成因过程为热源(深部热异常体、放射性元素衰变生热)—主要传热通道(深循环)—次级传热通道—热气沿裂隙传至隧道岩体,其过程伴随着S元素的富集,易形成HS或SO有毒有害气囊.

A highway tunnel under construction in Honghe Prefecture, Yunnan Province was taken as the research object to study the geological genesis of high ground temperature. The tunnel has both high water temperature and high rock temperature, with the maximum water temperature of 63.4 ℃ and the maximum rock temperature of 88.8 ℃. The regional thermal control, water source, heat source, and heat conduction channel are analyzed from the aspects of regional geological structure, seismic characteristics, hydrochemical characteristics,and geothermal reservoir characteristics. The hot water source, evolution process, and origin of heat source are studied by means of hydrogen oxygen isotope analysis, strontium isotope analysis, trace element analysis, and radioactive element analysis. Based on the geological, hydrogeological and excavation conditions of the tunnel,the geological genesis of the high water temperature section and the high rock temperature section of the tunnel is dissected and discussed. The results show that the genetic process of high water temperature in limestone sections is different from that in granite sections. The genetic process of high water temperature in tunnel is “heat source(deep thermal anomaly)–main heat transfer channel(deep cycle)–secondary heat transfer channel–shallow water mixing and water rock interaction”, which is accompanied by cold and hot water mixing, ion exchange, etc.;while the genetic process of high rock temperature in tunnel is “heat source(deep abnormal body, radioactive element decay heat generation)–main heat transfer channel(deep cycle)–secondary heat transfer channel–hot gas being transmitted to the tunnel rock mass along the crack”, and the process is accompanied by the enrichment of S element, which is favorable to the formation of toxic and harmful air bag of HS or SO.