Deflection Mechanism and Safety Analysis of Coal Mine Shaft in Deep Soil Strata

Abstract

The main shaft and auxiliary shaft in the Guotun Coal Mine underwent large deflections, with deflection values of 359 mm and 322 mm, respectively. These two deflections represent the first occurrence of such large vertical shaft deviations in the soil strata in China. The deflection problem has seriously affected the hoisting safety and lining safety and has become a serious impediment to the sustainable production of mines. Therefore, the deflection mechanism must be determined. For this purpose, based on mining subsidence theory, the spatial probability integral method and a more accurate time function were used to establish a model, called 3D dynamic prediction model, for predicting the shaft movement. The formulas for calculating the lining stress caused by coal mining were based on established models. With measured shaft deflection data, the prediction parameters for deep soil strata were calculated on the basis of an inversion analysis. A comparative analysis of measured and calculated deflection values revealed that the reason for shaft deflection in Guotun Coal Mine is the insufficient size of the protection coal pillar (PCP); namely, the design parameters of the PCP in current codes are not applicable to the deep soil strata. As a result, under the asymmetric mining conditions, mining causes the shaft to deflect without damage and under the symmetric mining conditions, mining causes the lining to fracture. The results have an extremely important significance for the prevention and control of shaft deflection, for the rational design of PCP, and for the sustainability of mine production.

A spatio-temporal predictive model for surface subsidence induced by mining in deep loose and thin bedrock strata

“…The stratal subsidence caused by mining not only results in the waste of land resources and severe ecological damage, but also severely affects the safety of underground structures and surface buildings (Huang et al 2008;Han et al 2019). Such problems become increasingly serious as the thickness of loose strata increases (Han. 2021).…”

Similar simulation test study on the influence of mining on shaft deflection of deep soil based on hydraulic permeability model

“…To study the problem of shaft deflection in deep soil. Han et al (2019a, 2019b) established a three-dimensional dynamic prediction model for predicting shaft movement using the probability integral method and time function, based on the mining subsidence theory. According to the prediction model, it is analyzed that the main cause of shaft deflection in deep soil is coal mining.…”