To drillsoft, unconsolidated, usually shallow formations by eroding the "rock" below the bit by hydraulic impact loading alone.
钻进松软、非固结，通常是浅地层时，通过仅仅依靠液力冲击载荷去冲蚀破碎钻头下的岩石。
2
The paper describes a waterjet-aided drill which, successfully developed by Changsha Institute of Mining Research, is useful in laboratory and capable of drilling holes both in soft and hard rock.
The bane that discussing the softrock geologic strata closes to drill a hole badly and solve the method and measures, and put forward the actual suggestion within work.