Research on the Dredging and prevention of Grout leakage in Overlying Rock Separation Grouting Boreholes

During the construction process of the overlying rock delamination grouting technology, problems such as borehole blockage, low grouting efficiency and grouting leakage are often encountered. To ensure the smooth implementation of the delamination grouting project, based on the water pressure pressure-time (p-t) curve of the ZK-7 borehole in the 15205 working face in the early stage of delamination grouting, the optimal grouting start-up time of the ZK-7 borehole is determined. And the ZK-7 borehole was cleared by using the high-pressure gas-hydraulic linkage through-hole technology. Based on the analysis of the actual geological conditions, the activation of the upper section of the DF8 fault and the fracture expansion in the syncline structural area have formed a temporary slurry migration channel, resulting in slurry leakage during the mining process of the working face. A comprehensive prevention and control plan for slurry leakage in the working face has been proposed. The test results show that: After the grout leakage phenomenon was treated, the average pressure value at the orifice was stable at about 2 MPa, meeting the normal grouting conditions.