Study on the influence of close range coal seam mining relationship on the deformation law of surrounding rock in lower roadway
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摘要: 近距离煤层上煤层工作面与下位煤层巷道采掘关系发生变化时，巷道围岩变形失稳机理会更加复杂，而目前针对上煤层工作面与下位煤层巷道推进方向不同时巷道受载动态演化规律及失稳特征的研究较少。以陕北能东煤矿近距离煤层为研究对象，采用理论分析、数值模拟与现场实测相结合的方法，对上煤层工作面回采后下位煤层巷道的稳定性进行了研究。理论分析得出，上煤层工作面开采后所产生的底板裂隙深度为22.5 m，未发育至下位煤层巷道。按采掘空间位置关系将回采工作面与巷道分为相向、相交、背向3个状态，数值模拟当巷道与工作面的空间位置关系发生变化时下位煤层巷道围岩的变形情况，结果表明：① 上煤层工作面与下位煤层巷道的采掘关系为相交与背向推进时，巷道围岩应力呈先增后减再增的趋势，在推进距离为90 m时，最大应力为6.5 MPa，应力集中系数为1.49，在推进距离为100～110 m时，巷道围岩应力降低幅度最大，降低了53.2%，在推进距离为150 m时应力最小，为0.95 MPa，之后不断增大，直到恢复至原岩应力。② 巷道围岩位移量在推进距离为100～150 m时增长幅度较大，在150 m时顶板位移量达到最大，为0.036 m，随着巷道越接近边界煤柱，其巷道位移量越小。现场实测结果表明：上煤层工作面过下位煤层巷道时，巷道位移量显著增长，顶板最大位移量为3.41 cm，与数值模拟结果一致；相交推进过程中若地质条件简单可以适当加快推进速度，减小上煤层工作面开采对下位煤层巷道的影响。Abstract: When the mining relationship between the upper coal seam working face and the lower coal seam roadway in the close distance coal seam changes, the deformation and instability mechanism of the surrounding rock of the roadway will be more complicated. At present, there is little research on the dynamic evolution law and instability characteristics of the roadway when the upper coal seam working face and the lower coal seam roadway advance in different directions. Taking the close range coal seam of Nengdong Coal Mine in northern Shaanxi as the research object, a combination of theoretical analysis, numerical simulation, and on-site measurement is used to study the stability of the lower coal seam roadway after the upper coal seam working surfaceis mined. Theoretical analysis shows that the depth of the floor cracks generated after mining the upper coal seam working surfaceis 22.5 m, and they have not developed to the lower coal seam. According to the spatial relationship of mining, the mining face and the roadway are divided into three states: facing, intersecting, and advancing in the opposite direction. Numerical simulations show that when the spatial relationship between the roadway and the working face changes, the deformation of the surrounding rock of the lower coal seam roadway is affected. The results show the following points. ① When the mining relationship between the upper coal seam working surface and the lower coal seam roadway is intersecting and advancing in the opposite direction, the stress of the surrounding rock of the roadway shows a trend of first increasing, then decreasing, and then increasing again. When the length of intervals of travel is 90 m, the maximum stress value is 6.5 MPa, and the stress concentration factor is 1.49. When the length of intervals of travel is 100-110 m, the stress reduction of the surrounding rock of the roadway is the largest, decreasing by 53.2%. When the length of intervals of travel is 150 m, the minimum is 0.95 MPa, and then it continues to increase until it returns to the original rock stress. ② The displacement of the surrounding rock in the roadway increases significantly when the length of intervals of travel is between 100-150 m, and reaches its maximum displacement of 0.036 m at 150 m. As the roadway approaches the boundary coal pillar, the displacement of the roadway decreases. The on-site measurement results show that when the upper coal seam working surface passes through the lower coal seam roadway, the displacement of the roadway increases significantly, and the maximum displacement of the roof is 3.41 cm. It is consistent with the numerical simulation results. If the geological conditions are simple during the process of intersecting advancement, the advancement speed can be appropriately accelerated to reduce the impact of upper coal seam working surface mining on lower level roadways.
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图 1 工作面与巷道空间位置关系
Figure 1. Spatial position relationship between the working face and the roadway
图 5 不同空间位置下采场围岩应力分布规律
Figure 5. Stress distribution law of stope surrounding rock at different spatial positions
图 6 不同空间位置下3−2煤层超前垂直应力分布
Figure 6. Distribution of advance abutment pressure in 3-2 coal seam at different spatial positions
图 7 不同空间位置下采场围岩位移分布规律
Figure 7. Displacement distribution law of stope surrounding rock at different spatial positions
图 8 不同掘进距离下巷道围岩位移分布规律
Figure 8. Displacement distribution law of roadway surrounding rock under different excavation progress
表 1 现场岩体参数
Table 1. In-situ rock mass parameters
参数 值 参数 值 $\varphi_{\mathrm{s}} $/（°） 35.40 M/m 1.30 H/m 150.00 k 3.96 γ/（kN·m−3） 25.00 Cm/MPa 5.34 f 0.22 $\varphi_{\mathrm{m}} $/（°） 27.90 
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表 2 煤岩力学参数
Table 2. Mechanical parameters of coal rock
岩性 密度/
（kg·m−3）体积模
量/GPa剪切模
量/GPa泊松比 抗拉强
度/MPa黏聚力/
MPa内摩擦
角/（°）粉砂岩 2420 3.5 2.1 0.21 2.69 6.48 28.4 4−2煤 1250 1.6 1.0 0.28 0.7 5.99 24.4 细砂岩
夹泥岩2350 2.8 1.8 0.22 1.59 5.96 27.9 3−2煤 1280 1.3 0.84 0.28 0.73 6.63 20.8 粉砂岩
夹泥岩2240 2.8 1.8 0.21 1.65 4.06 35.4 3−1煤 1220 1.6 1.0 0.29 0.7 5.34 27.9 泥岩 2370 2.8 1.8 0.23 2.69 6.48 28.4 2−2煤 1250 1.6 1.0 0.28 0.7 5.99 24.4 泥质
粉砂岩2420 3.5 2.1 0.21 2.69 6.48 28.4
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