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Vertical backfill drill-hole is usually a key project in an underground mine with backfill method and can be easily damaged by impact of backfill slurry. Observation of the damaged vertical backfill drill-holes in Jinchuan Nonferrous Metal Corporation (JNMC), Gansu Province, China, given by a digital drill-hole video camera, indicated that there usually exist serious wear zones in casing pipe in vertical...
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