Study on Construction Technology of Surface Ground Pre-Grouting for Mine Shafts in Northwest China Mining Area

In order to solve the high dficult construction of the pre-grouting at surface ground for mine shaft in China Northwest mining Area, the theoretical analys is and site test method was applied to the study on the pre-grouting technology at surface ground for a mineauxiliary shaft of HongDer Mine. Before the mine shaft sinki ng, the top overburden soil section was construction with a ground freezing method and as for the low base rock section, a pre-grouting technology at the surface groun d was conducted as the water sealing measure.The vertical boreholes and S type boreholes combined construction method was applied to realize the simultaneous ope rations of the grouting, ground freezing and mine permanent headframe installation.The results showed that the final grouting pressure value at the rock cushion sectio n was 1.5 times higher than the hydrostatic pressure value of the same stratum level, all final grouting pressure value of each grouting borehole at the base rock groutin g section was two times higher than the hydrostatic pressure value, the average grouting value of the mine shaft was 53.9 m3/m and the total grouting quantity was 19 227 m3, which was 3 606 m3 over the designed grouting quantity.The residual water inflow value at the grouting section of the mine shaft was 2.3 m3/h obtained from t he pressurized water test. The total construction period completed was 58 days earlier than the designed construction period.Thus the pre-grouting at the surface groun d could ensure the engineering quality and could reduce the construction period.