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.

经过几年对钻机的跟踪研究,发钻机围岩业常遇到软岩有硬岩夹层的象,造成施工过程经常更换钻具的问题。