Comprehensive treatment technology for wellbore deflection in thick loose bed and thin bedrock formation

Aiming at the technical problems of comprehensive treatment of shaft deflection in thick loose bed and thin bedrock strata, taking the ground grouting treatment engineering of the deflected shaft in Guotun Coal Mine in Juye Mining Area, Shandong Province as the background, new damage characteristics based on the coexistence of deviation and vertical compression deformation of the loose layer section in the shaft and the deviation to the direction of asymmetric mining face, the mechanism of shaft deflection and vertical compression deformation in Guotun Coal Mine is revealed. The analysis shows that the two characteristics are respectively caused by the horizontal overturning thrust and vertical additional force of the stratum under the superposition action of the non-uniform hydrophobic consolidation settlement of the bottom aquifer caused by the asymmetric mining of the coal seam. In line with the principle of ensuring safety and non-stop production treatment, a comprehensive treatment plan for ground grouting of in-service deflected shaft without stopping production has been formulated, and a series of comprehensive treatment technologies for deflected shaft have been developed: ① The dual control ground high-pressure grouting technology of “pressure relief and early warning” for protecting the shaft in service; ② New casing and construction technology for single hole and multi-layer grouting in thick loose layer; ③ Engineering determination method of ground grouting parameters in thick loose layer; ④ Early warning technology of deep hole high-pressure grouting treatment under the condition of continuous production operation of the in-service shaft. The comprehensive monitoring results show that during the grouting process of the main, auxiliary and wind deflected shaft treatment projects of Guotun Coal Mine, the comprehensive treatment technology of continuous production of the deflected shaft under the condition of thick loose bed and thin bedrock was strictly followed, and the drilling quantity of the grouting hole was 31026.8 m, the grouting quantity reached 35536.66 m³, realizing the grouting treatment of the shaft without stopping production. After the treatment, the shaft no longer deviates from north to west, during the grouting period of the main shaft, the deviation from the wellhead to the north and the west decreased by 12 mm and 18 mm respectively, and the deviation from the wellhead of the auxiliary shaft to the north and the west decreased by 13 mm and 41 mm respectively. Within one year after the completion of the grouting, the overall deviation of the shaft continues to decrease and has a positive trend, and the sinking rate around the shaft slows down, which ensures the safety of the shaft operation. The research results have been successfully applied in the ground high-pressure grouting treatment project of the deflected shaft in thick loose bed and thin bedrock strata of Guotun Coal Mine, providing reference and engineering experience for the future application in similar projects.