Abstract
To determine the impact of influencing factors on unsupported roof stability in coal mine roadway, a mechanical model of the unsupported roof was built. FLAC 3D numerical simulation was utilized to study the stability of the unsupported roof under the influence of the depth of the roadway, the thickness of the roof, and the unsupported-support distance. In view of the key influencing factors, the geological conditions of the site, and the relationship between the tensile stress and tensile strength of the unsupported roof, the maximum unsupported roof distance during roadway excavation was determined. Considering the surplus safety factor of the unsupported roof, the reasonable unsupported roof distance during the excavation of roadway 150802 was finally determined to be 2.08 m. The comprehensive roadway excavation speed increased by 62.7%, achieving a monthly progress over 500 m.
Highlights
Increase in the coal mine roadway roadwaying speed can be achieved through two approaches, : (1) increase the unsupported roof length and improve the efficiency of each roadway excavation cycle and (2) reduce the time consumption of roadway bolt support operation and increase the operating rate of the roadheader
Precious research studies have increased the speed of coal mine roadway excavation by a certain extent, the considered factors affecting unsupported roof stability were relatively limited. erefore, a mechanical model was built to analyze the relationship between the tensile stress of the unsupported roof and the various influencing factors
On site results showed that the theory and numerical simulation analysis in this paper was safe and feasible for calculating the unsupported roof length. is paper provides an important theoretical basis for rapid excavation of coal mine roadways
Summary
Along with the roadway excavation, the pressure on the rock mass of the roadway surface goes from three-dimensional to two-dimensional while the strength of the rock mass reduces extensively. When the pressure exceeds the ultimate strength of the rock mass, the surrounding rock collapses, starting from the roadway surface which can be regarded as the direct roof. According to equation (7), the maximum deflection of the unsupported roof is as follows: ωmax. E above parameters are substituted into the above equation to determine the maximum unsupported roof length of the roadway. E relationship between the unsupported roof length and the surplus safety factor during roadway excavation is as follows: bm a . Collapse of the surrounding rock mass is mainly due to tensile-shear force, so the Mohr–Coulomb yield criterion is introduced to the calculation of the numerical model. By simulating the changes in each factor listed, the resulted vertical stress of the roadway roof is calculated and recorded
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