乡镇煤矿资源回收率低，严重缩短了矿井的服务年限。
It has been shortening the service life of mines because of their low recovery ratio.
运行矿井提升绳的更换，在矿井运行服务年限中是有相当次数的。
There are many times of replacement of lifting ropes during the shaft service life?
运行矿井提升绳的更换，在矿井运行服务年限中是有相当次数的。
There are many times of replacement of lifting ropes during the shaft service life?
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