Abstract
The hydrophobicity of the aquifer at the bottom of the porous alluvium will affect the stability of the shaft. According to the changes of water level and the compressive amount of alluvium, we can evaluate the shaft stability and predict the shaft failure. In this work, the simulation model of the auxiliary shaft in the Zhuxianzhuang Coal Mine is generated by using the Nsdc software to evaluate the stability of the shaft during drastic drawdown dewatering. Based on the measured hydrophobic compression ratio in an adjacent coal mine, the compressive amounts of the strata near the main and auxiliary shafts in the Zhuxianzhuang Coal Mine are predicted under the condition of drastic drawdown dewatering, which will be 249.69 mm and 302.75 mm, respectively. It is more likely that the shaft wall may fracture in the 15th day (fourth load level) under the condition of drastic drawdown dewatering. The formation compressive amount near the auxiliary shaft is approximately 320 mm, which is close to the measured predicted value. At the same time, the Fisher discriminant model is established, and it is predicted that the state of the main and auxiliary shafts will be failure under the conditions of drastic drawdown dewatering in the Zhuxianzhuang Coal Mine. Based on the simulating results, the technical means of using the ground grouting for early prevention and control is proposed.
Highlights
Introduction e HuangHuai region is an important coal production base in China
When the load level is the fifth load level, the vertical stress of the shaft wall at the bottom of alluvium reaches 70 MPa, which exceeds the strength of the shaft wall (C20–C40), and the possibility of the shaft failure is large
Prediction results of strata compression near the main and auxiliary shafts in the Zhuxianzhuang Coal Mine are showed in Table 5. en, using the same method to calculate the remaining 11 months, the water level dropped by 4 m, and the compressive amounts of the formation near the main and auxiliary shafts are 8.47 mm and 10.27 mm, respectively
Summary
Because the thickness of alluvium in the Zhuxianzhuang Coal Mine is large, the nature of soil are different and the properties of the bedrock weathering zone, shaft wall, and soil material are completely different; different lithological materials are selected in the appropriate constitutive model. Taking the auxiliary shaft in the Zhuxianzhuang Coal Mine as an example, the simulated radial width is from the central axis of the shaft to 200 m and the depth is 9 m below the surface to the bedrock weathering zone, and the depth is 260 m. E stress state of the shaft and the compression of the formation under the condition of drastic drawdown dewatering are analyzed. The simulation scheme of drastic drawdown dewatering is designed (see Table 3) to analyze the stress of the shaft wall and formation deformation
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