So researching the mechanism of water damage of unlined tunnel and how to control it is very necessary.

因此研究公路裸洞隧道水害的机理以及防治措施是很有必要的。

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Considering the high cost for Iining pressure tunnel a considerabie economic advantage can be obtained if pressure tunnels keep unlined completely or only partly.

由于衬砌水电站压力隧洞费用极高，如果能取消、即使部分取消压力隧洞的钢板衬砌，将能得到极大的经济效益。

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