After several years to jumbolter research,the hard rocks always present in the soft ones in the wall rock procedure using jumbolter,which results in changing the boring tool during the procedure.
经过几年钻机的跟踪研究,发现
钻机
围
作业中常遇到软
中有硬
的现象,造成施工过程经常更换钻具的问题。