Characteristics of breaking coal-rock by submerged jet and its application on enhanced coal bed methane recovery.

Hydraulic slotting is a technique to enhance coal bed methane (CBM) recovery and prevent gas disasters. The drilling fields are usually arranged in floor roadway rather than roof roadway, but submerged jet effects caused by hydraulic slotting in roof roadway have not been carried out extensively. Concerning this issue, this paper conducted a series of numerical simulation and physical experiments on hydraulic slotting in roof roadway. It is shown that when the impact load of middle- and high-pressure water jet is applied to the sample, downlink borehole slotting can cause much stronger disturbance than uplink slotting due to the submerged jet. The fracture characteristics of samples also reflect that cavitation erosion caused by submerged jet promotes the fracture formation under middle and high impact load conditions. [ABSTRACT FROM AUTHOR]