## 5 Conclusions  
Tunnel aerodynamic effect, accompanied with environmental noise, facility safety, as well as human health problems, challenges the operation safety of high-speed railways. As the targeted velocity of HSTs is likely to approach 450 km/h in the near-future, investigation in this filed indicates urgent practical need. The present paper conducted a set of field tests and numerical simulations regarding train's passage and intersection with train's velocity ranged within 350-495 km/h. Numerical results were first validated by field measurements, indicating the discrepancy being less than 10%. Research concludes the following findings:  
1. TPL acting at tunnel surface and the train body presents unevenly distribution trend as the longitudinal distance to tunnel entrance increases. Pressures measured near tunnel center is generally higher than that those detected near tunnel portal. The pressure peak measured at tunnel surface first increases and then decreases with the maximum value appearing at the intersection position (tunnel center in the current research). Besides, for a given location, TPL nearby the train side increases with the measuring height and show slight difference on the other side.
2. Amplitude of micro-pressure wave increases with train's velocity. The maximum value of MPW detected in the field test is approximately 37.63 Pa. Meanwhile, amplitude of MPW is inversely proportional to the attenuated distance, i.e., \(P_{micro}\propto\frac{1}{x_{th-max}}\). Through data fitting, empirical model was established to predict the longitudinal attenuation of amplitude of MPW.
3. Pressure rapidly increases before the heat-to-head intersection and then fast decreases due to the tail-to-tail intersection. In the situation of train's intersection, variation of the pressure peak near the tunnel portals is insignificant though train's velocity changes. On the contrary, pressure peaks measured at the intersection position are doubled. The peak pressure load appears at the train head while carriages of the train body will be within the negative region after the head-to-head intersection. For the given location, values of pressure peak obtained from both the intersection side and non-intersection side presents limited variation while values change when the longitudinal location varies.  
Conceptualization by [PERSON] and [PERSON]. Methodology by [PERSON] and [PERSON]. Formal Analysis by [PERSON] and [PERSON]; Data Curation by [PERSON] and [PERSON]; Writing--Original Draft by [PERSON]; Writing--Review and Editing by [PERSON] and [PERSON]; Supervision by [PERSON] Funding acquisition by [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript.  
Figure 20: Dimensionless maximum pressure load \(P_{tu-max}^{*}\) at tunnel sidewall regarding train’s intersection.  
**Funding:** This work was financially supported by National Key R&D Program of China (Grant No. 2022 YFB2603400) and China Railway Group Science and Technology Research and Development Program (Grant No. P2021T013).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors would like to acknowledge the computational support from AMD (China) by providing AMD EPYC 7003 Processors with AMD 3D V-CACHE.  
**Conflicts of Interest:** The authors declare no conflict of interest.