问答题

回柱放顶时,必须每几个人一组,一人回柱放顶,一人观察顶板及支架周围情况,观察人员除协助回柱外不得兼做其他工作。严禁什么?

【参考答案】

严禁单人作业。在煤矿井下作业中,回柱放顶是一项危险性较高的工作,需要严格遵守安全操作规程。通常要求至少两人一组进行作业,......

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相关考题

Deep inside a mountain near Sweetwater in East. Tenness...


单项选择题Deep inside a mountain near Sweetwater in East. Tennessee is a body of water known as the

Lost Sea. It is listed by the Guinness Bool of World Records as the world&39;s largest underground lake. The Lost Sea is part of an extensive and historic cave system called Craighead Caverns.The caverns have been known and used since the days of the Cherokee Indian Nation. The cave expands into a series of huge rooms from a small opening on the side of the mountain. Approximately one mile from the entrance, in room called "the Council Room", many Indian artifacts have been found. Some of the items discovered include pottery, arrowheads, weapons, and jewelry.
For many years there were persistent rumors of a large underground lake somewhere in a cave, but it was not discovered until 1905. In that year, a thirteen-year-old boy named Ben Sands crawled through a small opening three hundred feet underground. He found himself in a large cave half filled with water.
Today tourists visit the Lost Sea and ride far out onto it in glass-bottomed boats powered by electric motors. More than thirteen acres of water have been mapped out so far and still no end to the lake has been found. Even though teams of divers have tried to explore the Lost Sea, .the full extent of it is still unknown.
1、The Lost Sea is unique because it is__________.
A.part of a historical cave system
B.the biggest underground lake in, the world
C.listed in the Gninness Book of World Records
D.the largest body of water in Tennessee
Who located the Lost Sea in recent times?A.The Cherokee Indians.
B.Tourism.
C.Ben Sands.
D.Scientists.
It can be inferred from the passage that the Craighead Caverns presendy serve as__________. A.an Indian meeting ground
B.a tourist attraction
C.a motor boat race course
D.an underground testing site
The Craighead Caverns have been known__________.A.through history
B.since the time of the Indian Nations
C.since 1905
D.since divers explored them