grade tunnel的意思|示意

Then, the divide standard of damage grade and the enduring fire limit time of the tunnel lining caused by fire accident are discussed.

在此基础上提出了隧道衬砌火灾损伤等级的划分标准与耐火极限时间。

The iron powder quality is ensured through tunnel kiln reduction and second reduction by using iron scale of high grade as raw material.

以优质铁鳞为原料，加强隧道窑和二次精还原工艺技术管理，确保铁粉质量。

The road double lines multi-arch tunnel has such advantages as low ground area, easy connection with other lines and so forth, and is adopted more and more widely in high grade road construction.

公路双线连拱隧道以其占地少、与线路连接方便等突出优势在高等级公路建设中被越来越多的采用。