Table 4
New finding-based estimands from ancient sources.
| Indicator name | Measurement method | Value range or category | Engineering implication |
|---|---|---|---|
| Fracture Zone Width | Ground-Penetrating Radar | 2.5–5.0 m | Indicates potential risk zones for collapse |
| Surrounding Rock Weathering Degree | Advanced Borehole Logging | Moderate to severe | Affects support structure design |
| Groundwater Enrichment Level | Forecast Borehole Water Test | Moderate (localized strong) | Risk of water inflow or gushing |
| Rock Mass Integrity (RQD) | Core Drilling (Forecast Hole) | 40%–60% | Determines stability and excavation difficulty |
| Anomalous Reflection Zone Depth | GPR Longitudinal Section | 8–12 m ahead of the tunnel face | Used to pre-locate weak rock layers or voids |
| Karst or Cavity Signal Strength | Electromagnetic Scanning | High intensity signal zone | Indicates possible hidden cavities or erosion areas |
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