Table 12 Problems of unfavorable geology.
Problems of unfavorable geology | Geological problem analysis |
|---|---|
Gushing water | The top cover of the shaft is 0.4m thick gravel soil. The lithology of the lower surrounding rocks are sandstone, charcoal shale and granodiorite. The permeability of sandstone and charcoal shale is basically slightly permeable, with permeability rate of 0.1 ~ 1Lu. The permeability rate of granite diorite is 0.1 ~ 5Lu. The rock body is slightly ~ weakly permeable, and the groundwater activity is weak. A small amount of dripping and seepage phenomenon may exist locally during the shaft boring, but it will not produce sudden water surge phenomenon |
Geostress and rockbursts | The maximum burial depth of the right line of the proposed tunnel is about 466.9m. The maximum burial depth of the left line is about 466.2m. This shaft traverses the rock of the mountain body which is generally mainly a medium-weathering granodiorite layer with good rock integrity. The rock integrity coefficient Kv of this layer is taken to be 0.49 according to the description of the strata |
Hazardous gas | By investigating the geological data within the scope of the project area, there is basically no source of harmful gases for the shaft crossing the mountain in this engineering. Even if the concentration exists, it is relatively small and the impact on the construction is slight. So the amount of harmful gas gushing out can be approximated as 0 m3/min |
Quartz content | According to the geological data of tunnel, the quartz content of the formation lithology traversed by SBM in this shaft is as follows: sandstone quartz content is 25% ~ 50%; charcoal shale quartz content is 3% ~ 5%; and granodiorite quartz content is 25% ~ 40%. Accordingly, the integrated value of quartz content in SBM tunneling in this formation is 25% |
