Research on deep and thick topsoil wellbore monitoring and its deflection laws

In order to study the deflection and deformation law of vertical shafts in deep and thick topsoil layer, the main and secondary shafts of Shandong Guotun Coal Mine are taken as the examples, and the wireline baseline method is adopted to carry out multi-period deformation monitoring. Based on the multi-period monitoring data, the dynamic information of shaft deflection was obtained, and combined with the geological conditions and mining activities, the temporal and spatial characteristics of shaft deflection and deformation were investigated to analyze the changes of the local parameters of the shaft, compare the differences in shaft deflection, and reveal the deflection and deformation law of the shafts in deep topsoil layer, which provides a reliable basis for demonstrating the mechanism of shaft deflection and the management of the shafts. The study shows that: the time characteristics of wellbore deflection in vertical wells affected by mining and grouting activities can be divided into three phases of “increasing-decreasing-stabilizing”, and the spatial characteristics are mainly manifested in that the bedrock layer is less deflected, while the topsoil layer shows a function-like significant change, and the dynamics of wellbore and its deflection in the topsoil layer are approximately equal, with the area of the largest wellbore deflection converging to the wellhead; the main and auxiliary wells are inclined to the northwest of the mining area and there is a difference in orientation. The overall inclination of the wellbore in the east-west direction accounts for more than 97%, while that in the north-south direction is only less than 20%, which is highly correlated with the working face direction in terms of the distance between the workings; the horizontal displacement of the deep topsoil layer triggered by the mining disturbance increases with the height of the wellbore, which is the main reason for the deflection of the wellbore.