尼格高地温隧道地热成因及地温分布特征研究

Study on geothermal origin and geothermal distribution characteristics of Nige high geothermal tunnel

隧道高地温带来诸多工程难题,如施工环境恶劣、衬砌耐久性降低、通风效果不佳等。以中国最高温公路隧道尼格隧道为研究对象,兼具干热岩和湿热岩特征,开挖掌子面围岩温度88.8℃,涌水温度63.4℃。通过地质调查、水化学分析、地热储分析、放射性元素分析、现场实测等方法,研究隧道的地热地质构造特征、地热热源、传热通道及温度场分布。研究结果表明,隧址区位于红河断裂等4组断裂地块内,地表温泉水温高达53.8~87.9℃,新构造活动强烈,地质构造复杂,穿越三叠系中统个旧组(T_(2g))灰岩和燕山期侵入(γ^( 3(a))_(5))花岗岩。隧道灰岩段地下水主要源自大气降水和浅表水下渗,裂隙水深循环与硅酸盐岩、表层与白云岩发生水-岩作用。运用SiO_(2),Na+K,K+Mg和Na+K+Ca地热温标,推测隧址区的热储温度为122.47℃,热储埋深2457 m。热源为地壳深部热异常体和放射性元素衰变生热,排除个旧燕山期花岗岩岩浆余热为热源的可能。花岗岩放射性元素衰变生热率10.01μW/m^(3),是滇东南燕山期花岗岩生热率的1.7~8.2倍。热源通过岩体向地表传递,断层Fn1,Fn2,fn1,接触带L_(J),构造优势裂隙L_(G),溶蚀及岩溶通道LR构成传热通道。现场实测岩体温度随埋深增大而增加,灰岩段为湿热岩,水温>岩温>气温;花岗岩段为干热岩,岩温>气温。在相同埋深下,灰岩段水温(岩温)明显低于花岗岩段岩温。研究成果可为类似工程地热成因分析提供借鉴。

The high temperature of the tunnel brings many engineering problems,such as poor construction environment,reduced lining durability,and poor ventilation effects.The Nige,the highest temperature Tunnel in China,was taken as the research object,which features the characteristics of both hot dry rock and hot damp rock,the surrounding rock temperature of the palm surface of 88.8℃,and the inrush water temperature of 63.4℃.Through geological survey,water chemistry analysis,geothermal storage analysis,radioactive element analysis,on-site measurement and other methods,the geothermal geological structure characteristics,geothermal heat source,heat transfer channel and temperature field distribution of the tunnel were studied.The results show that the tunnel site area is located in four groups of fault plots,including the Honghe Fault.This area features a surface hot spring water temperature of up to 53.8~87.9℃,strong new tectonic activity,complex geological structure,and passes through the Triassic Middle Formation(T_(2g))limestone and Yanshan period intrusionγ ^(3(a))_(5) granite.The groundwater in the limestone section of the tunnel is mainly derived from atmospheric precipitation and shallow underwater infiltration,and the deep circulation of fissure water interacts with silicate rocks,surface layers and dolomites.By using SiO_(2),Na+K,K+Mg,Na+K+Ca geothermal temperature scales,it was estimated that the heat storage temperature in the tunnel site area is 122.47℃,and the heat storage depth is 2457 m.The heat source is heat generation from the deep crust thermal anomalies and the decay of radioactive elements,which excluded the possibility of waste heat from granite magma in the old Yanshan period as a heat source.The decay heat generation rate of granite radioactive elements is 10.01μW/m^(3),which is 1.7~8.2 times that of granite in the Yanshan period of southeast Yunnan.The heat source is transmitted to the surface through the rock mass,and the faults fn1,Fn2,fn1,contact zone L_(J),tectonic dominant fissure L_(G),dissolution and karst channel LR constitute heat transfer channels.The measured rock mass temperature at the site increased with the increase of burial depth,the limestone section was hot and humid rock,and the water temperature is higher than the rock temperature,and the temperature is the lowest;the granite section was hot dry rock,and the rock temperature is higher than the temperature.At the same burial depth,the water temperature(rock temperature)of the limestone section is significantly lower than that of the granite section.The research results can provide areference for the analysis of similar engineering geothermal genesis.