不同微观裂隙密度下断层黏滑失稳规律离散元模拟

doi:10.3969/j.issn.0253-4967.2024.06.008

地震地质 ›› 2024, Vol. 46 ›› Issue (6): 1357-1373.DOI: 10.3969/j.issn.0253-4967.2024.06.008

不同微观裂隙密度下断层黏滑失稳规律离散元模拟

赵乾百¹⁾(), 赵永¹⁾^,^*(), 杨天鸿¹⁾, 滕龙²⁾, 王述红¹⁾, 刘一龙¹⁾

¹⁾ 东北大学, 资源与土木工程学院, 沈阳 110000
²⁾ 长沙矿山研究院有限责任公司, 长沙 410012

收稿日期:2023-11-01 修回日期:2023-12-27 出版日期:2024-12-20 发布日期:2025-01-22
通讯作者: *赵永, 男, 1991年生, 副教授, 主要从事岩体孕灾机理和灾变预警、微震监测理论与应用等方面的研究, E-mail: zhaoyongrock@163.com。
作者简介:
赵乾百, 男, 1997年生, 现为东北大学资源与土木工程学院矿业工程专业在读博士研究生, 主要从事断层黏滑失稳破坏机理以及破坏模式和岩体力学空间参数非均匀性分布表征等方面研究, E-mail: 2538440998@qq.com。
基金资助:
国家自然科学基金(52374157); 国家自然科学基金(52004052); 博士后国际交流计划派出项目(2020059); 教育部中央高校基本科研业务经费(2023GFYD17)

DISCRETE ELEMENT SIMULATION STUDY OF FAULT STICK-SLIP INSTABILITY PATTERNS AT DIFFERENT MICROCRACK DENSITIES

ZHAO Qian-bai¹⁾(), ZHAO Yong¹⁾^,^*(), YANG Tian-hong¹⁾, TENG Long²⁾, WANG Shu-hong¹⁾, LIU Yi-long¹⁾

¹⁾ Northeastern University, School of Resources & Civil Engineering, Shenyang 110000, China
²⁾ Changsha Mining and Metallurgy Research Institute Co., Ltd., Changsha 410012, China

Received:2023-11-01 Revised:2023-12-27 Online:2024-12-20 Published:2025-01-22

摘要/Abstract

摘要：

在原岩应力及开采扰动作用下, 断层上、下盘的岩体内部为微裂隙赋存状态, 改变了岩体的受力构架体系, 对断层上、下盘滑动行为模型产生影响, 继而形成了不同的破坏模式。因此, 对不同微观裂隙密度下断层黏滑失稳运动过程的力学行为和损伤规律亟待开展进一步研究。声发射监测是研究断层黏滑破坏模型的重要手段, 可用来获取断层活化过程中的有效信息。然而, 断层结构面对岩体破裂声发射波的传播路径和强度造成了一定的阻碍, 从而在研究断层上、下盘与岩体结构面的响应机制方面存在一定的局限性。文中采用离散元数值模拟方法构建了不同微观裂隙密度条件下的数值模型, 以模拟断层的黏滑失稳破坏过程。此外, 通过记录颗粒间接触的力学行为变化, 更深入地研究了断层黏滑的声发射特性和演化规律。研究结果详细地阐明了不同微观裂隙密度对黏滑失稳运动过程的影响, 包括应力-应变关系(如黏滑次数、启滑应力、启滑应力降和最大应力降)及声发射信号特征的演化规律。文中成果为深入理解岩体微观裂隙密度对黏滑失稳过程的影响提供了重要见解, 并为断层活化的力学行为研究提供了一种新的数值模拟方法。此外, 文中研究可作为室内断层黏滑声发射实验和现场微震监测研究的重要参考。

关键词: 断层黏滑, 声发射, 微观裂隙密度, 力学行为

Abstract:

This study examines the impact of in-situ stress and mining-induced disturbances on fault stability, specifically focusing on the influence of micro-crack density on the fault stick-slip instability process. The rock masses on the hanging wall and footwall of a fault are often characterized by micro-cracks, which alter their load-bearing structural system and thus influence the fault's sliding behavior, leading to various failure modes. Therefore, understanding the mechanical behavior and damage patterns associated with fault stick-slip instability under different micro-crack densities is essential. Acoustic emission(AE)monitoring, a critical tool for studying fault stick-slip failure, provides valuable information on fault activation. However, the fault structure constrains AE wave propagation paths and intensity, limiting insights into the interaction between fault planes and surrounding rock masses.

The study uses the Particle Flow Code(PFC), a discrete element method(DEM)simulation governed by force-displacement laws and Newton's second law, to model and analyze fault stick-slip instability. PFC simulates the motion and interaction of rigid particle assemblies, representing material fracture, damage, and crack propagation. In this framework, particle contact models define the mechanical properties of particle assemblies. The study constructs discrete element numerical models under varying micro-crack densities to simulate the stick-slip process of faults. By monitoring mechanical behavior at particle contacts, the study provides insights into the AE characteristics and evolutionary patterns of fault stick-slip. The AE system, constructed via the moment tensor method, reveals micro-fracture interactions within the rock mass and enables identification of fracture types and the spatio-temporal distribution of AE events. During fault stick-slip instability, the moment tensor represents the displacement generated by contact forces on particles, akin to the effect of body forces. By tracking displacement and force changes during particle-bond fracture, the moment tensor is calculated based on contact forces within the fracture region.

Key findings reveal that different micro-crack densities significantly influence the fault stick-slip instability process. The results detail stress-strain relationships(e.g., stick-slip event frequency, onset stress, stress drop at onset, and maximum stress drop)and AE signal evolution patterns. The fault stick-slip instability process can be divided into four stages, with numerous tensile micro-cracks generated near the fault surface. As micro-crack density increases, structural damage within the rock mass intensifies, reducing the fault's self-locking effect. This, in turn, affects fault stick-slip instability. Increased micro-crack density generally leads to a larger maximum stress drop, while onset stress drop tends to decrease. High micro-crack density also correlates with a higher frequency of minor stress drops in the latter stages of stick-slip.

In conclusion, this study provides valuable insights into the effects of micro-crack density on the fault stick-slip instability process, presenting a novel numerical simulation approach for examining fault activation mechanics. These findings offer a reference for laboratory AE experiments on fault stick-slip and contribute to field-based microseismic monitoring research.

Key words: fault stick-slip, acoustic emission, microcrack density, mechanical behavior

赵乾百, 赵永, 杨天鸿, 滕龙, 王述红, 刘一龙. 不同微观裂隙密度下断层黏滑失稳规律离散元模拟[J]. 地震地质, 2024, 46(6): 1357-1373.

ZHAO Qian-bai, ZHAO Yong, YANG Tian-hong, TENG Long, WANG Shu-hong, LIU Yi-long. DISCRETE ELEMENT SIMULATION STUDY OF FAULT STICK-SLIP INSTABILITY PATTERNS AT DIFFERENT MICROCRACK DENSITIES[J]. SEISMOLOGY AND GEOLOGY, 2024, 46(6): 1357-1373.

图/表 12

图1 断层黏滑模型构建 a 成样阶段; b 预压阶段; c 胶结阶段; d 构建断层阶段; e 施加围岩阶段; f 加载阶段

Fig. 1 Set up of the fault stick-slip model.

表1 光滑黏结模型微观参数

Table1 Micro parameters of the SJ model

参数类型	微观参数	数值
光滑节理模型微观参数	法向刚度/N·m^-1	30×10⁹
	切向刚度/N·m^-1	30×10⁹
	摩擦系数	0.55

表2 平行黏结模型微观参数

Table2 Micro parameters of the PB model

参数类型	微观参数	数值
颗粒基本物理参数	密度/kg·m^-3	2661
	最小颗粒半径/mm	0.45
	最大颗粒半径/mm	0.585
	孔隙率	0.15
	线性部分模量/GPa	23.5
	线性部分刚度比	1.5
线性平行黏结微观参数	摩擦系数	0.5
	黏结部分模量/GPa	23.5
	黏结部分刚度比	1.5
	法向强度均值/MPa	98
	法向强度方差/MPa	19.6
	切向强度均值/MPa	98
	切向强度方差/MPa	19.6
	内摩擦角/(°)	45

图2 震源区颗粒定位

Fig. 2 Schematic diagram showing particle location in the epicenter area.

图3 声发射事件的矩张量计算

Fig. 3 The calculation of moment tensor for acoustic emission events.

表3 微观裂隙密度几何参数

Table3 Geometric parameters of microscopic fracture density

工况	倾角分布方式	位置分布方式	尺寸分布方式	尺寸分布范围	密度
工况一	高斯分布均值135°;方差90°	均匀分布	负幂律分布指数3	1×10^-3~2×10^-3m	0个/m²
工况二	高斯分布均值135°;方差90°	均匀分布	负幂律分布指数3	1×10^-3~2×10^-3m	10个/m²
工况三	高斯分布均值135°;方差90°	均匀分布	负幂律分布指数3	1×10^-3~2×10^-3m	20个/m²
工况四	高斯分布均值135°;方差90°	均匀分布	负幂律分布指数3	1×10^-3~2×10^-3m	30个/m²
工况五	高斯分布均值135°;方差90°	均匀分布	负幂律分布指数3	1×10^-3~2×10^-3m	40个/m²

图4 不同微观裂隙密度下应力-应变曲线(全局) a 应力-应变曲线; b不同微观裂隙密度模型

Fig. 4 Stress-Strain curves(global)at various microcrack densities.

图5 不同微观裂隙密度下的应力-应变曲线(局部) a 微观裂隙密度为0; b 微观裂隙密度为10; c 微观裂隙密度为20; d 微观裂隙密度为30; e 微观裂隙密度为40

Fig. 5 Stress-Strain curves(local)at various microcrack densities.

图6 不同微观裂隙密度下的岩体破坏形态 a 微观裂隙密度为0; b 微观裂隙密度为10; c 微观裂隙密度为20; d 微观裂隙密度为30; e 微观裂隙密度为40

Fig. 6 Rock mass failure modes at various microcrack densities.

图7 不同微观裂隙密度下声发射震级的空间分布 a 微观裂隙密度为0; b 微观裂隙密度为10; c 微观裂隙密度为20; d 微观裂隙密度为30; e 微观裂隙密度为40

Fig. 7 Spatial distribution of acoustic emission magnitudes at various microcrack densities.

图8 不同微观裂隙密度下应力特征点演化 a 启滑应力和黏滑次数; b 应力降与应力降

Fig. 8 Evolution of stress characteristics at various microcrack densities.

图9 不同微观裂隙密度下裂纹演化曲线 a 不包含微观裂隙; b 包含微观裂隙

Fig. 9 Fracture evolution curves at various microcrack densities.

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不同微观裂隙密度下断层黏滑失稳规律离散元模拟

DISCRETE ELEMENT SIMULATION STUDY OF FAULT STICK-SLIP INSTABILITY PATTERNS AT DIFFERENT MICROCRACK DENSITIES

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