Study on instability criterion of rib pillars in open-pit during highwall mining

doi:10.16265/j.cnki.issn1003-3033.2023.09.0454

Abstract

Abstract:

To investigate the instability criteria of the rib pillar, determine the reasonable setting of the rib pillar during highwall mining in an open-pit coal mine and realize the optimal design of parameters for both the open-pit highwall and the rib pillar, a mechanical model of roof-rib pillar was constructed using Winkler elastic foundation theory. Theoretical formulas of vertical displacement of the roof and the vertical stress of the rib pillar during highwall mining were derived and validated through numerical simulation. Considering safety requirements for rid pillars, combined with Wilson's ultimate strength theory of the coal pillar, the instability criteria of rid pillars in open-pit mining was established. The study explored the impact of slope and pillar shape parameters on the safety of the rib pillar theoretically. The results show that the safety factor of the rib pillar exhibits a negative exponential correlation with mining depth, end-slope angle and end-slope height. Conversely, it shows a linear positive correlation with the total width of the coal pillar, and the theoretical curves of the vertical displacement of the roof and the vertical stress of the rib pillar exhibit a saddle-shaped distribution. Theoretical calculations are in good agreement with numerical simulation results, thereby verifying the rationality and accuracy of the theoretical calculations.

Key words: open-pit mine, highwall mining, rid pillar, instability criterion, elastic foundation

LI Guanghe, HU Zihuan, WANG Dong, WANG Laigui, ZHOU Zhiwei, DING Chunjian. Study on instability criterion of rib pillars in open-pit during highwall mining[J]. China Safety Science Journal, 2023, 33(9): 122-128.

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岩性	厚度/m	密度/(kg·m^-3)	弹性模量/GPa	泊松比	内摩擦角/(°)	黏聚力/kPa	抗拉强度/MPa
第四系	23	1 920	0.05	0.42	15	17	0.87
砂砾岩Ⅰ	40	1 831	1.3	0.4	33.5	25.6	0.51
煤Ⅰ	19	1 178	0.96	0.34	34	56	0.68
粉砂岩	7	1 941	0.8	0.39	35	65.4	1.31
砂砾岩Ⅱ	17	1 831	1.3	0.4	33.5	25.6	0.51
煤Ⅱ	6	1 178	0.96	0.34	34	56	0.68

采深d/m	煤柱总宽度N/m	边坡角θ/(°)	边坡高度H/m	与安全系数F的关系式
d	280	28	100	F=1.344×0.992d+1.207
300	N	28	100	F=0.011N-1.688
300	280	θ	100	F=0.701exp(-θ/275.984)+2.212
300	280	28	H	F=2.068 9exp(-H/54.339)+1.056

煤柱数量n/个	煤柱宽度a/m	采深d/m	回采率k/%	预计回采煤量Q/t
38	7.684	300	43.19	399 593.9
39	7.333	300	44.36	410 418.7
40	7.000	300	45.53	496 173.6
41	6.683	282.361	43.95	406 625.4
42	6.381	234.357	37.39	345 932.3