## 5 Conclusions  
Through the channel modeling of the ground electrode current field in the tunnel environment and the analysis of the buried electrode, various factors affecting the information transmission characteristics of the ground electrode current field are analyzed.  
Under different conductivities, the receiving voltage decreases sharply with the distance, and at a distance of 100 m, the receiving voltage is only \(\upmu\)V. This puts forward the requirement for the receiving ability of the system to be able to detect the \(\upmu\)V signal.  
Under different conductivities, the path loss increases significantly with the increase in the penetration distance. According to the relationship between the path loss and the penetration distance, the matching and selection of the transmitter power can be guided by the designed sensitivity of the receiving unit.  
Affected by the skin effect, if the resistivity is too small, the penetration ability of the electromagnetic wave signal will deteriorate, and if the resistivity is too high, the radiation power of the ground electrode will be low. When the resistivity is constant, the smaller the frequency, the stronger the signal penetration ability, but the information transmission rate is extremely low.  
As the number of parallel electrodes increases, the contact area between the electrodes and the ground increases, and the ground impedance of the electric dipole antenna decreases.  
The insertion depth of the ground electrode will affect the impedance between the electrodes. Therefore, variables, such as soil conductivity, depth of the ground electrode, radius of the ground electrode, and separation distance between the two vertical electrode rods must be considered.  
Through the research of this project, using the research results, we have developed and produced an engineering prototype that can penetrate underground projects and facilities such as mines or tunnels with a thickness of 1000 m of collapse and surrounding rock and conduct instant interactive text communication with a single piece of self-compiled information that does not exceed 24 characters. It solves the communication problems between rescuers and trapped personnel after accidents in underground projects and facilities within mines or tunnels, before and during rescue operations, and provides accurate information and communication guarantees for decision-makers to formulate scientific and accurate rescue plans and programs. It will definitely make outstanding contributions to the emergency rescue of underground projects in China and the world in the future.  
J.H.: visualization, data curation, formal analysis, writing original draft. H.Y.: investigation, resources, funding acquisition. Z.S.: supervision, project administration. B.Z.: conceptualization, validation. Z.K.: methodology, supervision. P.S.: software. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the special fund for safe production of China Communications Construction Corporation (BC2020000583).  
Not applicable.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The dataset can be accessed upon request.  
No conflict of interest exist in the submission of this manuscript, and this manuscript has been approved by all authors for publication.