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“轰隆!轰隆!”奔跑在青藏铁路线的火车,好像一条发威的巨龙,从高峻宽阔的青藏高原飞驰而过。所到之处,大地仿佛都在颤抖。青藏铁路的路基很高,因为冬天的冻土会在夏天融化,地面会升高,为防止掩盖路基,有的路基高度甚至达到20米呢。路基的下面修建了很多桥洞。这些桥洞是做什么的呢?
“Bang! Bang!” Running on the Qinghai-Tibet Railway line train, like a cruel dragon, speeding from the tall and wide Qinghai-Tibet Plateau. Wherever he went, the earth seemed to tremble. The Qinghai-Tibet Railway has a high subgrade because the permafrost in winter will melt in the summer and the ground will rise. In order to prevent covering the subgrade, some embankments even reach a height of 20 meters. Under the roadbed built a lot of bridge holes. What do these bridge holes do?