Speculum Observation and Trajectory Measurement in Gas Extraction Drilling: A Case Study of Changling Coal Mine

Figure 2

(a) Layout of boreholes for peeping and trajectory measurement in C₅^b coal seam. (b) Layout of high-level boreholes peeping and trajectory measurement in C₅^b coal seam. (c) Layout of trajectory survey boreholes in C₅^a coal seam. (d) Layout of trajectory survey boreholes in C₆^a coal seam. (e) Layout of trajectory survey boreholes in C₆^c coal seam.

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