坑道支柱

例句：

1. 1. The engineer designed the tunnel to be as straight as possible to ensure safe passage for the miners.
   工程师设计了尽可能直的隧道，以确保矿工的安全通行。
2. 2. During construction, the workers used these pillars to support the weight of the excavated earth.
   在施工期间，工人们使用这些支柱来支撑挖掘出的土体的重量。
3. 3. The pillars are made from reinforced concrete and are essential for maintaining the stability of the tunnel.
   这些支柱由钢筋混凝土制成，对于保持隧道的稳定性至关重要。