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煤体张开型裂隙演化规律及失稳前兆试验

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为探究不同裂隙分布特征参数煤体失稳前兆信息,基于MTS816试验系统开展单轴加载试验,分析了煤体力学特征及裂隙演化规律,推导出起裂角精确表达式,建立了弯折裂纹力学模型.结果表明:随裂纹方位角减小,煤体劣化程度增加,但均低于完整试件,裂隙长度同试件强度呈负相关性;剪切互锁效应使含裂隙煤体应力-应变曲线表现为双驼峰形态,互锁强度同方位角呈负相关性,但与长度无明显关联;裂隙分布特征参数对初始应变场形成局部高应变区具有显著引领作用,方位角于0°～90°之间时,应变集中、弥散与裂隙扩展的空间演绎形式高度统一;定义了端部动态剪切因子(τ0)并求得其表达式,完善了 Ⅱ型SIF(应力强度因子)并推导出精确起裂角表达式,得出起裂角同方位角呈负相关性;比较剪切互锁前后扰动系数ε(KⅡ/KⅠ)可知,剪切互锁效应可通过抑制裂纹端部的翼状Ⅰ型扩展从而发生Ⅱ型破坏,且抑制效果与方位角呈负相关性;相较于表面应变监测,互锁强度变化特征可对煤体在不同裂隙分布特征参数下的骤然破坏提供更加积极的前兆信息.
Evolution law of open fracture of coal body and instability precursor test
In order to explore the precursor information of coal instability with different fracture distribution characteristic parameters,uniaxial loading test was carried out based on MTS 816 test system,the mechanical characteristics and fracture evolution law of coal body were analyzed,the accurate expression of crack initiation angle was derived,and the mechanical model of bending crack was established.The results show that the deterioration of the coal body increases with decreasing crack azimuth,but the strength is lower than that of the intact specimen,and the length of the cracks is negatively correlated with the strength of the specimen.The shear interlocking effect makes the stress-strain curve of fractured coal body show a double hump shape.The interlocking strength is negatively correlated with the azimuth angle,but has no obvious correlation with the length.The characteristic parameters of fracture distribution play a significant leading role in the formation of local high strain zone in the initial strain field.When the azimuth angle is between 0° and 90°,the spatial deduction forms of strain concentration,dispersion and fracture propagation are highly unified.The dynamic shear factor(τ0)of the crack end is defined and its expression is obtained.The type Ⅱ SIF is im-proved and the exact crack initiation angle expression is derived.It is concluded that the crack initiation angle is negatively correlated with the azimuth angle.Comparing the disturbance coef-ficient e(KⅡ/KⅠ)before and after shear interlocking,it can be seen that the shear interloc-king effect can cause type Ⅱ failure by inhibiting the wing-like type Ⅰ expansion at the crack tip,and the inhibition effect is negatively correlated with the azimuth angle.Compared with surface strain monitoring,the variation characteristics of interlocking strength can provide more positive precursor information for the sudden failure of coal under different fracture dis-tribution characteristic parameters.

open crackDIC monitoringshear interlocking strengthend shear dynamic fac-torequivalent crack model

王磊、刘化强、李少波、张宇、刘怀谦、陈礼鹏、王安铖

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安徽理工大学深部煤矿采动响应与灾害防控国家重点实验室,安徽淮南 232001

中国矿业大学(北京)能源与矿业学院,北京 100083

非闭合裂纹 DIC监测 剪切互锁强度 端部动态剪切因子 等效裂纹模型

安徽高校协同创新项目安徽省科技重大专项项目安徽理工大学校级一般项目安徽理工大学研究生创新基金项目深部煤矿采动响应与灾害防控国家重点实验室开放基金课题项目

GXXT-2020-055202203a07020010xjyb2020-012022CX2033SKLMRDPC22KF10

2024

10.13247/j.cnki.jcumt.20230189

中国矿业大学学报
中国矿业大学

中国矿业大学学报

CSTPCD北大核心
影响因子：1.83
ISSN：1000-1964
年,卷(期)：2024.53(2)
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