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.

经年对锚杆钻机的跟踪研究,发锚杆钻机围岩作业中常遇到软岩中有硬岩夹层的,成施工程经常更换钻具的问题。