两条平行暗挖隧道相距小于1倍洞跨时,其开挖面前后错开距离不得小于()。
A. 10m
B. 15m
C. 20m
D. 25m
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登杆用的踩板,必须进行承力试验,其要求是:静荷重(),持续时间:5min。
A. 150kg;
B. 175kg;
C. 200kg;
D. 225kg。
当探测50kg/m钢轨轨头时,探头的折射角为69°,探头在轨面上的偏角应为()。
光路跳纤的两端应粘贴光路标签,光路标签的粘贴位置为离尾纤头5-10厘米处。
A. 正确
B. 错误
Due to the large amount of heat picked up by the air in boiler and engine rooms, it would be () to maintain ambient conditions within the comfort zone by air conditioning.
A. possible
B. necessary
C. practicable
D. impracticable