# An Established Theory of Digital Twin Model for Tunnel Construction Safety Assessment
## 5 Case Study
### Modeling Accuracy and Content
Therefore, the modeling level of materials should be at white-box level. In this study, the RFID tag is also used as the main technology to store information on various construction materials. Taking a segment as an example, its model expression formula is \(CM_{1}=\{\)AT334190314T, {segment, 6000 mm, 5500 mm, 1000 mm, C50, P10, HPB300, HRB400}, reinforced concrete, shield interval 1, 2018-04-12 of a construction section of a project, segment factory of a construction bureau of a city, {shield normal tunneling-segment assembly, 15 min, qualified}, [232.2, 200.7, \(-\)11]]. The specific meaning is {The unique identification ID corresponding to the segment and the active RFID, {material type, outer diameter, inner diameter, ring width, concrete strength grade, impermeability grade, reinforcement type, reinforcement grade}, material, location, production time, production unit, {the construction process in which the segment is located, the time spent in the process, quality grade}, {location coordinate, (unit: meter)}]. As an external factor that may impact construction safety, environmental information may lead to a more severe loss of life and property. Therefore, environmental information is a construction element that cannot be ignored. In this paper, the environmental factors that may affect construction safety are divided into two categories. One is the environmental factors that directly affect the structural safety, represented by the surrounding rock. The other is the environmental factors that affect the workers' status (such as the concentration of harmful gases); among them, the surrounding rock and other factors are mainly considered for their mechanical properties, which are defined as the white-box level. The concentration of harmful gases and other relevant environmental factors only need to be considered as simple numerical information, which is defined as the black-box level. The surrounding rock information can be stored in the digital twin model by the construction of geological exploration results. The model expression formula is \(GI_{\text{I}}=\{\)[0.108, 0.125, 5.84], 13.62]. The specific meaning is {rock mass integrity coefficient, surrounding rock quality index, compression modulus}, surrounding rock deformation value (unit: mm)). The model expression formula of harmful gas concentration and other related environmental factors is \(EI_{\text{I}}=\{\)0.01%, 18 \({}^{\circ}\)C, 0.4% rh, 3 m/s\(\}\). The specific meaning is \(EI_{\text{I}}=\{\)concentration of harmful gas, temperature, humidity, wind speed\(\}\). The tunnel construction process is dynamic, and many of the construction elements are not static. Many of the above elements should be monitored and updated with appropriate frequency. The purpose of this paper is to evaluate the construction safety state based on the digital twin model. The settlement, which can represent the main factor of construction structure safety, is selected as the critical monitoring and analysis parameter [42]. According to the requirements of relevant standards, the data collection frequency is once a day. The collection results are both the basis for model updating and essential data for risk prediction.