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Through analyzing the reason of great accidents in coal mine in recent years, the new characteristics was revealed, that most great gas-explosion accidents happened in lower-gas “safety” area under normal production conditions, but not in higher-gas area to be on guard. Weakness of emergency rescue was pointed out when emergencies were confronted. It is indicated that replied and controlled hidden...
The erosion (circular) pit is a common sedimentary structure but its genesis is complex. Many erosion pits occur on the Yellow River delta plain, with some formed by ice-water erosion. The ice-water pits are generally circular or semi-circular in cross-section, and are typically 2–40 cm across and 2–20 cm in depth. We identify four types of pits on the basis of their origin: (i) pits that formed by...
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