Analysis of the genesis of the Yulyu high-temperature hot spring in Shenzhen and its impact on the Luotian-Tiegang Water Conveyance Tunnel Project

Abstract

The geological conditions along the Luotian Reservoir-Tiegang Reservoir water conveyance tunnel in Shenzhen are complex. The main tunnel line is adjacent to the Yulyu medium-to-high-temperature hot spring, which has a flow rate of approximately 1.5 L/s and a maximum temperature of 66~68℃. The genesis of the hot spring remains unclear, and the potential mutual impacts between the hot spring and tunnel construction require focused study. By employing surface geophysical prospecting, drilling, geothermal temperature testing, hydrochemical and isotopic analyses, this study investigates the formation mechanism of the Yulyu hot spring and evaluates its potential impacts on the tunnel project. The tunnel excavation validated the accuracy of the analytical result. The findings indicate that the geothermal water originates from atmospheric precipitation, with a recharge elevation of 102-169 m. The recharge area is identified as the northern slope of a low hilly region south of the hot spring, situated within a granite zone bounded between the southern plate of the Yulyu Fault and the northern plate of the Huangcaokengding Fault. The recharge water circulates deeply along secondary faults and fracture-dense zones, ascends via thermal convection along the Yulyu Fault, and emerges at structurally weak surface locations to form the hot spring. The Luotian-Tiegang water conveyance tunnel route avoids the deep cyclic seepage field of the Yulyu hot spring's recharge, flow, and discharge pathways. The project construction exhibits minimal impact from the Yulyu hot spring and its geothermal activity, nor does it adversely affect the hot spring itself.

Keywords

Yulyu hot spring in Shenzhen / geothermal / hydrogen and oxygen isotopes / Luotian-Tiegang Water Conveyance Tunnel