Extraction of multiple seam using fully mechanized coal mining technology caused severe deformations in the lower coal seam roadways in Zhaiyadi Coal Mine in Shanxi Province, China. Understanding the characteristics of the lower coal seam entry failure mechanism under the remnant pillar is the first step in determining a reasonable location of the lower coal seam entry. Characteristics of the lower coal seam entry failure mechanism under the remnant pillar are investigated by means of numerical simulations and in-situ observations. To improve the reliability of the numerical simulations, the global model is validated by comparing the surrounding rock deformation of 3905 headgate with the in-situ observation data due to the extraction of Panel 3805. The numerical simulation results of the global model indicate that the original 3905 headgate under the remnant coal pillar is located in the vertical stress concentration zone and horizontal stress concentration zone. Firstly, the peak vertical stress concentration factor in the coal seam 9# (the lower coal seam) is 4.9, located 100 m behind the active Panel 3805 while the peak horizontal stress concentration factor in the coal seam 9# is 2.1, and located 30 m behind the active Panel 3805. When the delay distance to the active Panel 3805 is 80 m, the stress transmission angle reaches a constant value of 30.9°. Secondly, both the ratio of coal pillar rib deformation to solid coal rib and the ratio of roof subsidence to floor heave increase as the delay distance to the active Panel 3805 increases. Finally, numerical results show that the designed 3905 headgate located 25 m to 30 m away from the middle of the remnant coal pillar would be an alternative scheme, located out of the floor horizontal stress concentration and vertical stress concentration in the coal seam 9#. The findings in this study will help to provide a basis to select a reasonable location for lower coal seam roadways under similar mining and geological conditions.

采用综采技术的多煤层开采导致了山西省寨亚迪煤矿下部煤层巷道的严重变形。了解残余煤柱下煤层下陷破坏机理的特征是确定下煤层下陷合理位置的第一步。通过数值模拟和现场观察，研究了残余煤柱下煤层进入破坏机理的特征。为了提高数值模拟的可靠性，通过将3905闸门的围岩变形与由于提取3805面板而产生的现场观测数据进行比较，来验证整体模型。整体模型的数值模拟结果表明，残余煤柱下方的原始3905闸门位于垂直应力集中区和水平应力集中区。首先，煤层9＃（下部煤层）的垂直应力集中系数峰值为4.9，位于活动面板3805后面100 m，而煤层9＃中的水平应力峰值集中系数为2.1，位置30在活动面板3805后面的m处。当到活动面板3805的延迟距离为80 m时，应力传递角达到30.9°的恒定值。其次，随着到活动面板3805的延迟距离增加，煤柱肋变形与实心煤肋的比率以及顶板沉降与底鼓的比率两者都增加。最后，数值结果表明，设计的3905闸板位于距残余煤柱中间25 m至30 m处，是一种替代方案，位于9＃煤层的底板水平应力集中和垂直应力集中之外。这项研究的结果将有助于为在相似的采矿和地质条件下选择较低煤层巷道的合理位置提供依据。