短语词组短语roof -bolt t drill 顶板锚栓钻机grouted roof -bolt 洞顶灌浆锚杆cemented roof -bolt 钢筋混凝土锚杆roof bolt plate 锚杆垫板mine roof bolt 矿顶螺栓expansion type roof bolt 膨胀式锚杆 返回 roof bolt