Ground grouting stratum reinforcement technology for thick loose layer adjacent to existing shaft

In order to solve the technical problem of ground grouting reinforcement of existing vertical shaft in thick loose layer,taking the ground grouting treatment of deflected shaft in thick loose layer of Guotun Coal Mine in Juye Mining Area of Shandong Province as the engineering background,and according to the shaft deflection characteristics of Guotun Coal Mine,a field borehole water pressure test and ground high-pressure grouting test were used to analyze the ratio of test pressure water at the injection point of different grouting depths and grouting intervals to maximum pressure of grouting head in different grouting depth and grouting layer section,and obtained the ratio of grouting pressure at injection point to hydrostatic pressure at this point,and the injectability and grouting technical parameters of the main aquifer in the thick loose layer are obtained. Finally,the design principle and construction scheme of the ground grouting treatment scheme for the deviated shaft in the thick loose layer were determined. Moreover,a new type of single well multi-layer grouting casing was developed,and the “injection discharge” joint intermittent grouting reinforcement technology was formed. The results show that：① when the grouting pressure reaches about 2.0-2.5 times of the hydrostatic pressure,the cement slurry can be injected smoothly; ② the deeper the loose layer is,the smaller the unit slurry suction volume of the stratum is; in the same grouting section,under the same pressure,the water pressure flow is twice of the grouting amount; ③the error between the designed grouting amount and the actual grouting amount determined by grouting test is within 27%. With the grouting of the grouting hole,the phenomenon of water coming out of the hole orifice,slurry returning and slurry flowing in the hole pipe orifice appeared in the adjacent pressure relief hole,which realized the purpose of pressure relief,and had little influence on the stress deformation of the adjacent existing shaft; ④after grouting,the water inrush on the surface soil section of the main shaft,auxiliary shaft and air shaft decreases obviously,and there is a tendency to return to normal. The research results have been successfully applied in the surface high-pressure grouting treatment project of the deflected shaft in the thick loose layer of Guotun Coal Mine.