考虑围岩应变软化及采空区接触的深部煤层底板破坏分析

尹尚先; 孟浩鹏; 钱双彬

doi:10.12363/issn.1001-1986.21.09.0474

考虑围岩应变软化及采空区接触的深部煤层底板破坏分析

doi: 10.12363/issn.1001-1986.21.09.0474

基金项目: 国家自然科学基金项目(51774136，51974126)；河北省自然科学基金重点项目(D2017508099)

详细信息

第一作者:
尹尚先，1964年生，男，山西朔州人，博士，教授，博士生导师，从事煤矿防治水工作. E-mail：yinshx03@126.com

中图分类号: TD12；TD325
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- 被引次数: 0
出版历程
- 收稿日期: 2021-09-01
- 修回日期: 2021-12-20
- 发布日期: 2022-05-25
- 网络出版日期: 2022-05-07

Failure analysis of deep coal seam floor considering strain softening of surrounding rock and formation contact in goaf

摘要

摘要: 为研究深部煤层开采底板破坏形态，提出考虑围岩应变软化和采空区接触的FLAC^3D有限差分数值方法，以河北开平煤田林西矿2023工作面底板实测导水裂隙带为工程背景，结合朗肯土压力理论定性分析，研究深部煤层底板破坏特征。结果表明：采用应变软化本构关系代替常用摩尔–库伦本构关系能够对围岩塑性破坏后的力学状态更准确表述；采用“应变软化–空–弹性”模型转变的方法，达到模拟采空区顶板垮落后应力传递的效果，弥补了以往煤层开采模拟中采空区垮落后顶底板不接触的固有缺陷；通过采空区顶底板接触与否条件下应力、位移的对比，发现采空区是否接触对数值结果影响巨大，突出考虑采空区接触的必要性；根据模拟结果中塑性剪切应变率的变化，实现了底板滑移面的三维显示，形态为斜向采空区的半包围面状结构；结合朗肯土压力理论将底板塑性区与主动区、过渡区和被动区对应，3个区破坏形式分别为剪切破坏、剪切破坏、拉张与剪切的交互破坏。提出的考虑围岩应变软化及采空区接触的FLAC^3D数值方法对煤层开采模拟实现了优化，并可为其他大变形后需考虑接触的工程模拟提供参考。
- 深部煤层 /
- 底板破坏 /
- 采空区接触 /
- 朗肯土压力 /
- 数值模拟 /
- 应变软化 /
- 河北开平煤田
Abstract: In order to study the failure mode of the floor in deep coal seam mining, we proposed a FLAC^3D finite difference numerical method considering the strain softening of surrounding rock and the contact of goafs .Through the qualitative analysis of Rankine’s earth pressure theory, the failure of the deep coal seam floor is studied based on the measured water conducting fracture zone of the floor in working face 2023 of Linxi Mine. The results show that the mechanical state of surrounding rock after plastic failure can be described more accurately by using the strain-softening constitutive relationship instead of the common Mohr−Coulomb constitutive relationship. The transformation method of “strain softening-emptiness-elasticity” model is adopted to simulate the stress transmission caused by the collapse of goaf roofs, which makes up for the inherent defect of no contact between the roof and floor after the goaf collapse in the previous simulation of coal seam mining. The stress and displacement when there is contact and no contact between the roof and floor of the goaf is compared, showing that the contact between the roof and the floor has a great impact on the numerical results. Therefore, the necessity of the contact needs to be considered. According to the change of the plastic shear strain rate in the simulation results, the three-dimensional display of the floor slip surface is realized, which is in the shape of half-surrounded surface structure of the inclined goaf. Based on Rankine’s earth pressure theory, the plastic zone of the floor is corresponded to the active zone, transition zone and passive zone. The failure forms of the three zones are shear failure, shear failure and the interactive failure of tension and shear. The proposed FLAC^3D numerical method considering strain softening of the surrounding rock and no contact achieves optimization for coal seam mining simulation and can provide a reference for other engineering simulations that need to consider contact after large deformation.
- deep coal seam /
- floor failure /
- formation contact in goaf /
- Rankine earth pressure /
- numerical simulation /
- strain softening /
- Kaiping Coalfield of Hebei

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图 1 2023工作面底板破坏深度实测钻孔布置

Fig. 1 Layout of boreholes for the failure depth in the floor of working face 2023

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图 2 2个钻孔漏失量曲线

Fig. 2 Two boreholes leakage curves

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图 3 D01-2钻孔不同深度成像

Fig. 3 D01-2 borehole imaging at different depths

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图 4 煤层底板破坏分区

Fig. 4 Coal seam floor failure zones

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图 5 煤层底板极限平衡状态

Fig. 5 Limit equilibrium state of coal seam floor

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图 6 2种本构模型应力–应变曲线

Fig. 6 Stress-strain curves of two constitutive models

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图 7 煤层底板破坏数值模型

Fig. 7 Numerical model of coal seam floor failure

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图 8 煤层顶底板竖直方向应力

Fig. 8 Stress in vertical direction of coal seam roof and floor

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图 9 煤层顶底板竖直位移

Fig. 9 Vertical displacement of coal seam roof and floor

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图 10 不同回采距离塑性区分布

Fig. 10 Plastic zone distribution in different mining distance

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图 11 不同回采距离塑性剪切应变突出区

Fig. 11 Strain-shear-plastic outburst zone in different mining distance

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图 12 2种地应力下局部模拟结果

Fig. 12 Local simulation results under two ground stresses

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表 1 数值模型岩石力学参数

Table 1 Rock mechanical parameters of the numerical model

岩层	密度/(kg∙m⁻³)	弹性模量/GPa	泊松比	黏聚力/MPa	抗拉强度/MPa	内摩擦角/(°)	剪胀角/(°)
中砂岩	2670	1.80	0.27	2.9	0.45	42	12
粉砂岩	2550	2.10	0.31	3.1	0.28	40	11
泥岩	2480	1.20	0.35	0.8	0.22	30	9
粗砂岩	2760	1.70	0.26	2.8	0.64	44	12
细砂岩	2590	2.00	0.29	1.1	0.33	32	10
煤层	1600	0.85	0.38	0.5	0.14	28	9

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