| This paper chooses the voca hot-springs in Tibet autonomous region as research object.Though analyzing the region geothermal and geologic background, do some researchs on the hot-springs distribution characteristics and its control factors,that find the springs appear on the zonal distribution along the esat-south,the direction as same as the west-border of voca basin,which show the distribution of springs has intimate connection with the fractures.Across the study of hydrochemical and isotope geochemical characteristics, Hot Springs is the main cation Na+, the main ingredients of anions SO42-, and the content of Cl- and hot temperatures are closely correlated. Hot-springs trace elements are close to background values in Tibet, and it significantly higher than surface water. With the comparison to Southwest meteoric water line, the main source of hot spring water from rainfall.the projected average annual temperature of recharge area -9℃, and supplies region between 5000 ~ 5300m elevation. Geochemical temperature scale and mixed use model calculations to estimate the storage temperature range of hot Voca 77 ~ 133℃between.Based on the geothermal gradient of the formation conditions and the calculation of geothermal, hot spring temperature and heat flow within the region can provide the heat conduction is roughly equal, it is mean that the main heat source of hot springs absorbing surrounding heat though deep-cycle, no special additional heat.The heat storage is fault type that is mainly stored in the hot spring fractured zone, and the area consists mainly of spring break deep cycle type. The forming conditions by analysis of hot spring water,comes mainly from Zengjiu river and bamboo river by watershed area, precipitation in the recharge area, infiltration along the bedrock fracture network, bringing together the western margin of the basin boundary fault Voca conducted deep circulation of groundwater circulation in the long process of fully absorb the heat of the rock formation deep underground hot water, then water blocking Voca ductile shear zone and other parts of the structural fault fracture zone intersected up, the last part in the favorable geological structure exposed on the emission. Integration of the aforementioned analysis of data for the construction of the tunnel for the more accurately predict the rock temperature.geothermal gradient was estimated though circulation patterns of Hot Springs with the regional heat flow value on the Voca area. La Long tunnel sections to predict rock temperatures.There are no medium-risk areas ,and only in the depth of the area and across the Voca area rated as slightly dangerous, accounting for 49% of total length of the tunnel, only to do processing to enhance ventilation.geothermal and the tunnel may have an impact. Geothermal development in the study area has a significant distribution, with the development of geothermal anomaly was controlled by faults, the formation of features according to Voca springs, water was blocked by east-west faults of the barrier. Voca hot water systems and the tunnel through the area belong to different hydrogeological units.With the limite of hydraulic conditions, water can not absorb a lot of heat for deep cycle and the formation of high heat flow, the heat encountered during tunnel excavation geothermal fluid is unlikely . Voca hot water systems and groundwater systems Lalong tunnel was through contact does not close.Lalong tunnel excavation of the tunnel caused the capture of Voca Spa is unlikely. Therefore, it is proposed to select the program through the Voca basin, groundwater system though will have some influence, but have a greater range of groundwater dewatering and hot spring on the Voca Capture group is unlikely.The program through the Voca basin is more feasible. |
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