## 2 Geologic Background and Methods
### Parameterization of the Model  
Thermal conductivity is a fundamental parameter in geothermal research, as it governs the distribution characteristics of the geothermal field. According to the previous research results of various lithologies in the model to define the parameters (Table 2), the Gonghe Basin Cenozoic stratigraphy as a whole has a low thermal conductivity of only 1 to 2 W/(m\(\cdot\)K), especially the upper shallow surface in the middle and upper Pleistocene and Holocene stratigraphy, which are dominated by the fluvial lake-phase sandy and gravelly mudstones, a set of loose sandy and gravelly clay, in a weak rock-forming state. Near the surface, 500-600 m, the thermal conductivity is extremely low, only 0.2-0.5 W/(m\(\cdot\)K). The thermal conductivity of the thickly developed Neoproterozoic claystone in the hinterland of the Gonghe Basin is 0.2142-0.6121 W/(m\(\cdot\)K), with an average of 0.3761 \(\pm\) 0.10 W/(m\(\cdot\)K); the specific heat capacity is 1.3388-1.5400 MJ/(m\({}^{3}\cdot\)K), with an average of 1.04276 \(\pm\) 0.09 MJ/(m\({}^{3}\cdot\)K); the thermal diffusion coefficient is 0.16 \(\times\) 10\({}^{-6}\)-0.40 \(\times\) 10\({}^{-6}\) m\({}^{2}\)/s, with an average of \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Drill Hole Number** & **Office Elevation (m)** & **Hole Depth (m)** & \multicolumn{2}{c}{**Temperature at the**} & **Geodetic Heat Flow** \\  & & & **Bottom of the Hole (\({}^{\circ}\)C)** & **Values (mW/m\({}^{2}\))** \\ \hline SZK03 & 3325 & 822 & 39 & 89.52 \\ SZK04 & 3135 & 550 & 21.1 & 51.32 \\ SZK05 & 2875 & 427 & 16.3 & 34.78 \\ SZK13 & 3483 & 980 & 26.8 & 46.94 \\ SZK10 & 2757 & 278 & 10.9 & 34.14 \\ SZK30 & 3070 & 600 & 28.9 & 70.77 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Calculation list of geodetic heat flow results along the tunnel route. \(0.2613\pm 0.07\times 10^{-6}\) m\({}^{2}\)/s. The thermal conductivity of the Middle Triassic shallow metamorphic sandstone slate ranges from 1.2957 to 2.4405 W/(m\(\cdot\)K), with an average of \(1.69\pm 0.31\) W/(m\(\cdot\)K); specific heat capacity is 1.4241-1.7700 MJ/(m\({}^{3}\cdot\)K), with an average of \(1.55\pm 0.10\) MJ/(m\({}^{3}\cdot\)K); and thermal diffusion coefficient is 0.6700 \(\times\) 10\({}^{-6}\cdot\)1.3934 \(\times\) 10\({}^{-6}\) m\({}^{2}\)/s, with an average of 1.03 \(\pm\) 0.18 \(\times\) 10\({}^{-6}\) m\({}^{2}\)/s. The thermal conductivity of Middle and Late Triassic granite is 2.0794-3.2623 W/(m\(\cdot\)K), with an average value of 2.7929 \(\pm\) 0.34 W/(m\(\cdot\)K); the specific heat capacity is 1.5605-1.8959 MJ/(m\({}^{3}\cdot\)K), with an average value of \(1.7576\pm 0.10\) MJ/(m\({}^{3}\cdot\)K); the thermal diffusion coefficient is 1.3325 \(\times\) 10\({}^{-6}\cdot\)-1.8666 \(\times\) 10\({}^{-6}\) m\({}^{2}\)/s, with an average of (1.5886 \(\pm\) 0.18) \(\times\) 10\({}^{-6}\) m\({}^{2}\)/s [27]. Since Equation (2) is used to calculate the temperature at the model base, the radiogenic heat production of rocks along the tunnel route must also be considered. This study refers to the work of [PERSON] et al. on the radiative heating rate of rocks in the Gonghe Basin and Guide Basin [20]. In this study, we utilize [PERSON] et al. 's calculations for the radioactive heat generation rate of rocks in the Gonghe Basin and Guide Basin. The rate for granite in the CPC area is defined as 3.1 \(\mu\)W\(\cdot\)m\({}^{-3}\), and for sedimentary rocks in the Gonghe