sand-prevention pillar 防砂煤柱
coal pillar for sand proof 防砂煤柱
sand-proof pillar 防砂煤柱
pillar against sand 防砂煤柱
safety pillar against sand 防砂煤柱
set safety pillar prevent sand 防砂煤柱留设
anti-sand & anti-collapse coal pillar 防砂防塌煤柱
·2,447,543篇论文数据，部分数据来源于NoteExpress
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