| With the rapid development of China’s energy industry,coal production is increasing and gradually moving deeper,and it has become a trend for coal mining to develop deeper.During the construction and operation of vertical shafts in extra-thick topsoil layers,factors such as aging of the original support structure,high load operation and poor surrounding rock conditions often lead to the reduction or loss of strength of vertical shafts in extra-thick topsoil layers,and their safety is greatly threatened,leading to destabilisation and damage of the shaft.In view of this,this paper uses a combination of theoretical analysis,numerical simulation and field measurements to study the rupture mechanism and repair and reinforcement technology of shaft walls in extra-thick topsoil layers.(1)Using theoretical analysis methods,the stress characteristics and rupture features of shaft walls in extra-thick topsoil layers were comparatively analyzed,and it was concluded that the loads on shaft walls mainly include: self-weight load,lateral pressure,vertical additional force,temperature stress and other loads.The main reason for the rupture of the shaft wall is that the water level of the aquifer drops due to surface pumping or mine mining evacuation and drainage,which increases the effective stress and leads to soil consolidation and induces ground settlement,eventually leading to the rupture of the shaft wall.(2)According to the engineering geology and construction conditions,the MIDAS GTS NX finite element software was used to establish the force model of the vertical shaft wall in the extra-thick topsoil layer,and the force distribution law of the shaft under hydrophobic conditions was obtained,and then one pressure relief tank(at the stress concentration,-593m;under the three compartments,-540m;in the middle of the aquifer,-570m)and two pressure relief tanks(-540 m and-593m)were considered.The stress distribution patterns of the repaired ruptured wellbore in the extra-thick topsoil layer under different repair scenarios were investigated.The results show that the single relief tank at-593 m provides better vertical stress relief than that at-570 m and-540m;secondly,the difference between the single relief tank and the double relief tank for vertical stress relief in the shaft walls is small,about 7.28%.(3)Combining the rupture mechanism of the shaft walls in the extra-thick topsoil layer and the traditional topsoil wall repair cases,the design and management principles for the repair of ruptured vertical wells in the extra-thick topsoil layer were summarised and combined with the numerical calculation results,the repair and reinforcement design and construction plan were determined as follows: the height of the inter-wall grouting section is 90 m,from-513 m to-603m;the height of the post-wall grouting section is 12 m,from-591 m to-603 m.At-593 m,a pressure relief tank is installed with a size of600mm1000mm;and at-528.7m to-531.7m,the reinforced section is 3m high with 15 channel steel well rings,at-585.5m to-590.5m,the reinforced section is 5m high with 25 channel steel well rings,and at-592.2m to-593.8m The reinforced section is 1.6m high and 8 channel steel well rings are erected.(4)To ensure the safety of the shaft and the reliability of the rehabilitation program,steel string displacement gauges and steel string pressure gauges were used to monitor the displacement deformation of the pressure relief tank and the pressure applied to it in real-time.The maximum vertical pressure in the pressure relief tank was 8.3MPa,which was lower than the maximum load-carrying capacity of the inner wall,and the wall was in a safe condition.The research results of this paper provide technical guidance for the rehabilitation and reinforcement of vertical shaft walls with extra-thick topsoil layers,and also provide a reference basis for the design and construction of vertical well rehabilitation projects with extra-thick topsoil layers,which is of great significance.Figure [64] Table [16] Reference [82]... |
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