Mechanism and control technology of floor heave in fully mechanized top-coal caving faces of ultra-thick coal seams

doi:10.16265/j.cnki.issn1003-3033.2025.05.0971

Abstract

Abstract:

In order to address the floor heave issue during the mining of fully mechanized top-coal caving faces in ultra-thick coal seams, the floor heave mechanism was investigated through field investigations, theoretical analysis, and numerical simulations. Corresponding control technologies were proposed. The ZF1409 working face in a coal mine in Shaanxi province was selected as the engineering case. Key findings include: Severe floor heave predominantly occurs during periodic weighting periods. Higher shield support resistance is observed, particularly in areas with mudstone-dominated floor strata or thin residual coal beneath the floor. The sliding surface of the floor stratum primarily consists of weak mudstone with low ultimate bearing capacity. Floor heave initiates when the applied load exceeds the ultimate bearing capacity. The frictional resistance and cohesion generated by the self-weight of the rock mass along the sliding surface are overcome. Numerical modeling of the ZF1409 face reveals that shield support resistance plays a critical role in floor heave evolution. Under fully mechanized top-coal caving conditions in ultra-thick coal seams, the sudden rupture of the near-field key stratum forms a cantilever beam structure, causing rapid escalation of shield resistance and subsequent floor heave. Implementing underground regional hydraulic fracturing technology to precondition the near-field key stratum effectively mitigates floor heave by optimizing stress redistribution.

Key words: ultra-thick coal seams, fully mechanized top-coal caving face, floor heave mechanism, control technology, near-field key stratum, hydraulic fracturing

CLC Number:

X936

ZHU Zhijie, WANG Peng, LI Ruiqi, QIN Hongyan, SHI Qingwen, CHEN Kun. Mechanism and control technology of floor heave in fully mechanized top-coal caving faces of ultra-thick coal seams[J]. China Safety Science Journal, 2025, 35(5): 73-81.

Figures/Tables 15

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Table 1

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Table 2

Ultimate bearing capacity of floor

载荷类型	载荷宽度/m	底板岩性	$φ$ /(°)	$γ$ /(kN·m^-3)	c/kPa	$N γ$	$N c$	$p u$ /MPa
支架载荷	2.5	泥岩	26.6	25.67	510	13.7	23.3	12.3
	2.5	煤	39.1	13.48	530	93.8	68.6	37.9
	2.5	粉砂岩	35.4	24.94	3310	51.2	47.8	159.8
超前支承压力	15	泥岩	26.6	25.67	510	13.7	23.3	14.5
	15	煤	39.1	13.48	530	93.8	68.6	45.8
	15	粉砂岩	35.4	24.94	3310	51.2	47.8	167.8

Table 2

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Table 3

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序号	来压类别	回采位置/m	来压显现支架编号	来压步距/m	来压显现情况
1	初次来压	118.55	40—70	118.55	工作面39—71号支架高度较低(前立柱3.5 m),支架阻力较大(30~40 MPa,最大压力40.3 MPa),40—66号支架架前切顶,45—65号支架前刮板输送机处底鼓
2	周期来压	168.1	58—100	49.55	工作面底板不平,支架和刮板输送机倾斜,65—92号支架前梁较低,前立柱高度不足3.7 m,58—95号支架后刮板输送机底鼓严重,60—100号支架前刮板输送机处底鼓
3	周期来压	214.4	50—76	45.5	50—65号支架阻力较大(30~40 MPa),68—76号支架前刮板输送机处底鼓严重
4	周期来压	256	71—99	42.4	78—93号支架后刮板输送机处底鼓,71—99号支架高度低,支架后立柱高度最低3.5 m,83—100号支架处顶板破碎
5	周期来压	287.85	60—100	31.85	60—100号支架工作阻力大,80—90号支架架前切顶,支架高度低(3.5 ~3.8 m),80—106号支架后刮板输送机处底鼓
6	周期来压	310.15	57—94	22.3	76—94号支架前刮板输送机处出现底鼓,底鼓量为200~400 mm;57—92号支架后刮板输送机处出现底鼓,底鼓量为300~500 mm;82号架高度为2.9 m,74—100号支架顶板破碎

岩性	密度/(kg·m^-3)	弹性模量/GPa	泊松比	黏聚力/MPa	内摩擦角/(°)	抗拉强度/MPa
粉砂岩	2 494.6	10.19	0.25	3.31	35.4	1.28
泥岩	2 567.0	1.2	0.32	0.51	26.6	0.26
细粒砂岩	2 506.1	7.07	0.25	1.81	33.4	1.45
砂质泥岩	2 460.5	2.5	0.29	0.39	26.6	0.22
含砾粗砂岩	2 566.5	10.64	0.26	2.62	34.2	1.40
中粒砂岩	2 560.3	16	0.26	2.02	33.8	1.60
煤	1 348.8	2.54	0.28	0.53	39.1	0.47