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Hardrock burst mechanisms and management strategies 硬岩爆震机理及管理策略
Geohazard Mechanics
Pub Date : 2023-03-01 DOI: 10.1016/j.ghm.2022.11.001
Graham Swan , Charlie C. Li

Rockbursts occur as a direct consequence of underground mining or civil excavation. The general scale of their seismic disturbance and consequences depend upon known factors. However, uncertainty remains as to exactly when and where rockbursts will occur, as well as the effectiveness of ground support measures to fully mitigate their consequences. While the uncertainty in when and where is a dilemma shared with earthquake prediction, that associated with ground support capability is both a design and a management concern. Following a brief review of the known mechanisms that produce rockbursts, the paper explores the sources and scales of energy demands that characterize the risk of their damaging consequences upon underground excavations. We note that some of this risk continues to be associated with uncertainty with respect to rockmass properties and in situ stress, particularly in the context of deep mining. A review is presented of all available yielding ground support systems and their necessary design requirements, identifying practical weaknesses and limitations where these are known. The paper concludes with some suggested areas where further study and development could provide the ways and means to reduce the design uncertainty in managing rockbursts.

岩爆是地下采矿或土木开挖的直接后果。其地震扰动的总体规模和后果取决于已知因素。然而，岩爆发生的确切时间和地点，以及充分减轻其后果的地面支撑措施的有效性，仍然存在不确定性。虽然何时何地的不确定性与地震预测一样是一个难题，但与地面支援能力相关的不确定性既是一个设计问题，也是一个管理问题。在简要回顾了产生岩爆的已知机制后，本文探讨了能量需求的来源和规模，这些来源和规模表征了其对地下挖掘造成破坏性后果的风险。我们注意到，其中一些风险仍然与岩体性质和现场应力的不确定性有关，特别是在深部采矿的情况下。对所有可用的屈服地面支撑系统及其必要的设计要求进行了审查，确定了已知的实际弱点和局限性。文章最后提出了一些建议，进一步的研究和发展可以为减少岩爆管理中的设计不确定性提供途径和方法。
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引用次数: 2
Detection and targeted control of regional stress field for coal burst prevention 区域应力场的探测与针对性控制
Geohazard Mechanics
Pub Date : 2023-03-01 DOI: 10.1016/j.ghm.2022.11.006
Linming Dou , Zhenyu Sun , Xuwei Li , Quan Liu , Siyuan Gong , Chao Wang

As coal burst normally occurs in the area of high stress concentration, it is of significance to study the features of regional stress field in coal mines. Primitive stress field, mining-induced stress field and their coupling effect are investigated through the methods of theoretical analysis, field measurement, numerical simulation and wave velocity CT inversion, and the relationship among regional stress field, high-energy seismic events and coal bursts are analyzed. Investigation of the 3# mining district in Xingcun coal mine shows that: (1) Though stress concentration changes in the mining process, several special areas witnesses stress concentration in the whole mining process, such as the rise pillar area, several syncline axis areas and large fault areas; (2) Coal burst occurrence and high-energy seismic events have a close relationship with regional stress field. Coal bursts and high-energy seismic events tend to occur in areas of stable stress concentration, such as the rise area, several syncline axis areas and large fault areas. Targeted control of stress field for coal burst prevention is developed based on stress field detection. The process of targeted control of stress field for coal burst prevention is: detection of regional stress field based mainly on wave velocity CT, identification of stress concentration, implementation of destress measures to control the identified stress concentration. This method of stress field control was applied to LW3306 working face in Xingcun coal mine and coal burst hazards were effectively controlled in LW3306.

由于冲击地压通常发生在高应力集中区，研究煤矿区域应力场特征具有重要意义。采用理论分析、实测、数值模拟和波速CT反演等方法，研究了原始应力场、采动应力场及其耦合效应，分析了区域应力场与高能地震事件、煤爆的关系。对兴村煤矿3#矿区的调查表明：（1）尽管应力集中在开采过程中发生了变化，但在整个开采过程中，有几个特殊区域出现了应力集中，如上升柱区、几个向斜轴区和大断层区；（2） 煤爆和高能地震事件的发生与区域应力场有着密切的关系。煤爆和高能地震事件往往发生在应力集中稳定的地区，如隆起区、几个向斜轴区和大型断层区。在应力场检测的基础上，提出了有针对性的应力场控制方法。煤爆防治应力场目标控制的过程是：主要基于波速CT检测区域应力场，识别应力集中，实施卸压措施控制识别出的应力集中。将该应力场控制方法应用于兴村煤矿LW3306工作面，有效地控制了该工作面的煤突灾害。
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引用次数: 2
Pendulum waves and basics of «geomechanical thermodynamics» 摆波和«地质力学热力学»的基础知识
Geohazard Mechanics
Pub Date : 2023-03-01 DOI: 10.1016/j.ghm.2022.12.001
V.N. Oparin

It is shown that modern achievements in the field of experimental and theoretical researches and developments of innovative measuring systems for monitoring of non-linear dynamic and kinematic characteristics allow to formulate basics of new academic discipline, designated as “geomechanical thermodynamics”. The following circumstances can be considered as the most important prerequisites for development of this new discipline.

(1) Practical completeness of the classical thermodynamics, based on kinetic gas theory and molecular movements in solid bodies; (2) Creation of “formular construction tool” for the description of dynamic and kinematic characteristics of pendulum waves and energy conditions of their occurrence and propagation from dynamic sources, located in multi-phased stressed rock mass and geomaterials with block-hierarchical structure; (3) Principal opportunity to establish formal relations between substantial energy carriers of “packages” of non-linear pendulum waves (geoblocks of certain hierarchical levels according to their diameters) and “molecules”: their movement, velocity and acceleration of the “molecules” ↔ “geoblock”; “force interactions between molecules” ↔ “non-linear elastic interaction between geoblocks”, etc.

The term of “geomechanical temperature” is introduced and its analytical expression, which is proportional to kinetic energy of movement of geoblocks with defined volume for their hierarchical subsequence at “confined” conditions of the stressed rock mass, is shown. The similar aspects are discussed, when emission acoustic-electromagnetic fields are fixed using corresponding coefficients of mechanical-electrical and mechanical-acoustic transformations. In order to quantitively describe the evolution of energy state of local zones of stress-strain concentration and surroundings of their non-linear influence from catastrophic events at the natural and mine-engineering systems (earthquakes, rock bursts, etc.), the terms of their geomechanical and thermodynamic stages are introduced and specified: Ti(i∈0,+,±,−,∗)‒ with background states (i∈0,∗) and three major stages (i∈+,±,−) outlined, where (+) is the concentration, (±, ‒) are the failure and relaxation and (∗) is the quasi-recovering up to “background” level after the occurred catastrophic event. Using certain examples, the existence of critical elastic energy content of local zones with “meta-stable state”, which is transforming to quasi-resonance process of failure and relaxation of “excessiv

研究表明，在实验和理论研究领域取得的现代成就，以及用于监测非线性动力学和运动学特性的创新测量系统的开发，有助于制定被称为“地质力学热力学”的新学术学科的基础。以下情况可以被认为是这门新学科发展的最重要的先决条件。（1） 基于气体动力学理论和固体中分子运动的经典热力学的实用完整性；（2） 创建“公式构建工具”，用于描述具有块体分级结构的多阶段受力岩体和岩土材料中摆波的动力学和运动学特征以及其发生和传播的能量条件；（3） 在非线性摆波的“包”（根据其直径具有特定层次的地质块）和“分子”之间建立形式关系的主要机会：“分子”的运动、速度和加速度↔ “地理块”；“分子之间的力相互作用”↔ “地质块体之间的非线性弹性相互作用”等。引入了“地质力学温度”一词，并给出了其解析表达式，该表达式与受力岩体“受限”条件下具有定义体积的地质块体的分级子序列的运动动能成比例。当使用相应的机电和机械声学变换系数固定发射声电磁场时，讨论了类似的方面。为了定量描述自然和矿山工程系统中灾难性事件（地震、岩爆等）对应力-应变集中的局部区域及其非线性影响的环境的能量状态演化，介绍并规定了其地质力学和热力学阶段的术语：Ti（i∈0，+，±，−，*）-具有背景状态（i∈0，*）和概述的三个主要阶段（i∈+，±、−），其中（+）是浓度，（±，-）是失效和松弛，（*）是灾难性事件发生后准恢复到“背景”水平。通过某些例子，证明了具有“亚稳态”的局部区域的临界弹性能含量的存在，该区域正转变为失效的准共振过程和“过量”能量的松弛（T±）。
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引用次数: 0
Disturbance response instability theory of rock bursts in coal mines and its application 煤矿冲击地压扰动响应不稳定理论及其应用
Geohazard Mechanics
Pub Date : 2023-03-01 DOI: 10.1016/j.ghm.2022.12.002
Yishan Pan, Aiwen Wang

Aiming at the rock burst prevention in coal mines, this study argue that a rock burst is the instability of the coal mass deformation system with the infinite deformation response subjected to a small disturbance, and the concepts of control, disturbance and response variables of the coal mass deformation system are proposed. The analytical solution of rock bursts of circular roadways is derived, using a mechanical model of the coal mass deformation system of circular roadways, and the stress and energy conditions of the disturbance response instability of a rock burst are also presented. Based on the disturbance response instability theory, this study identifies the factors controlling the occurrence of rock bursts, involving the coal uniaxial compressive strength, coal bursting liability and roadway support stress. The relationship between the critical stress and the critical resistance zone of surrounding rock in roadways, the coal uniaxial compressive strength, roadway support stress, roadway geometric parameters and coal burst liability is revealed, and the critical stress index evaluation method of rock burst risk is proposed. Considering the disturbance and response variables of rockburst occurrence, a monitoring system of rock burst based on stress and energy monitoring is established. Considering managing the disturbance and control variables, regional and local prevention measures of rock burst are proposed from four aspects: destressing in coal mass, avoiding the mutual disturbance between multi-group mining or excavation, reducing the dynamic load disturbance and weakening of the physical properties of the coal mass. Based on the enhancement principle of the roadway support stress on the critical load of rockburst occurrence and the energy absorption effect of the support, an energy absorption and anti-bursting support technology for roadways are proposed. The disturbance response instability theory of rock bursts has formed a technical system from the aspects of mechanism, prediction and prevention to guide the engineering practice for rock burst mitigation.

针对煤矿岩爆的预防，本文认为岩爆是在小扰动作用下具有无限变形响应的煤体变形系统的失稳，提出了煤体变形的控制、扰动和响应变量的概念。利用圆形巷道煤体变形系统的力学模型，导出了圆形巷道岩爆的解析解，并给出了岩爆扰动响应失稳的应力和能量条件。基于扰动响应失稳理论，确定了控制岩爆发生的因素，包括煤的单轴抗压强度、煤的爆裂倾向和巷道支护应力。揭示了临界应力与巷道围岩临界阻力区、煤单轴抗压强度、巷道支护应力、巷道几何参数和煤爆倾向之间的关系，提出了煤爆危险性的临界应力指标评价方法。考虑岩爆发生的扰动和响应变量，建立了基于应力和能量监测的岩爆监测系统。考虑到对扰动和控制变量的管理，从四个方面提出了岩爆的区域性和局部性预防措施：减轻煤体应力，避免多组开采或开挖之间的相互干扰，减少动载荷扰动，削弱煤体物理性质。根据巷道支护应力对岩爆发生临界荷载的增强原理和支护的吸能效果，提出了一种巷道吸能防爆支护技术。岩爆扰动响应失稳理论从机理、预测和预防等方面形成了一套技术体系，指导了岩爆治理的工程实践。
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引用次数: 4
Quantitative assessment of energy changes in underground coal excavations using numerical approach 用数值方法定量评价地下采煤能量变化
Geohazard Mechanics
Pub Date : 2023-03-01 DOI: 10.1016/j.ghm.2022.11.003
Chunchen Wei, Chengguo Zhang, Onur Vardar, John Watson, Ismet Canbulat

Coal burst is caused by a dynamic and unstable release of energy within the overstressed rock mass/coal during the mining process. Although the occurrence of coal burst is a result of the complex impacts of many factors, a major component of coal burst mechanism is associated with energy storage and release. This study reviewed the sources of energy that can contribute to a coal burst, principally strain and potential energy stored in the coal mass around excavations, and radiated seismic energy released by geological discontinuities. The energy balance concept proposed by [1] was utilised in numerical modellings to compute the radiated seismic energy in a modelling system and the kinetic energy of ejected rock/coal for a given burst scenario. The modelling results showed that the strain energy density (SED) around excavations increases with increasing mining depth and the maximum SED area migrates deeper into the coal. For the effect of geological features on both roadway and longwall face, the coal burst risk proneness can be assessed considering the proposed energy terms. According to the results of energy changes in excavations, the modelling predicts that for depths of ejection 2 ​m and 3 ​m the kinetic energy of a burst increases as the mining depth increases from 100 ​m to 1000 ​m, but for depth of ejection 1 ​m only increases until mining depth reaches 700 ​m and then decreases. The proposed energy-based model indicators can deepen the understanding of energy changes and the associated coal burst risks for different mining conditions.

煤爆是由采矿过程中过度应力的岩体/煤炭内能量的动态和不稳定释放引起的。虽然煤爆的发生是多种因素复杂影响的结果，但煤爆机制的一个主要组成部分与能量的储存和释放有关。这项研究回顾了可能导致煤爆的能量来源，主要是储存在挖掘周围煤块中的应变和势能，以及地质不连续性释放的辐射地震能。[1]提出的能量平衡概念被用于数值建模，以计算建模系统中的辐射地震能和给定爆破场景下喷出的岩石/煤的动能。模拟结果表明，随着开采深度的增加，采场周围的应变能密度（SED）增加，最大应变能密度区域向更深的煤层迁移。考虑到地质特征对巷道和长壁工作面的影响，可以考虑所提出的能量项来评估煤的爆裂风险倾向性。根据挖掘中能量变化的结果，模型预测，对于喷射深度2​m和3​m爆破的动能随着开采深度从100增加而增加​m至1000​m、 但对于喷射深度1​m只会增加，直到开采深度达到700​m，然后减小。所提出的基于能源的模型指标可以加深对不同开采条件下能源变化和相关煤爆风险的理解。
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引用次数: 2
An assessment of earthquake vulnerability by multi-criteria decision-making method 基于多准则决策方法的地震易损性评估
Geohazard Mechanics
Pub Date : 2023-03-01 DOI: 10.1016/j.ghm.2022.11.002
Md. Saalim Shadmaan, Samsunnahar Popy

Background

Earthquake is one of the most destructive catastrophes in Bangladesh and the evaluation of vulnerability is a prerequisite for the earthquake risk estimation. As a result, determining vulnerability is essential for lowering the future fatalities. The fundamental challenge in estimating the seismic vulnerability is to have a systematic understanding of all potential earthquake related losses. With this objective, the current study deals with evaluating the seismic vulnerability of Sylhet district of Bangladesh.

Method

A multi-criteria decision-making approach such as the analytical hierarchy process (AHP) has been used in this study to estimate the earthquake vulnerability. For the assessment of three scenarios namely social, structural, and physical distance vulnerabilities, several criteria have been chosen in order to fully identify the risk of earthquake.

Findings

The study uncovers the vulnerable areas of Sylhet district. It is revealed that in terms of social vulnerability, 9% area of Sylhet district is under very high, 55% high, 15% moderate, 17% low, and 4% is under very low vulnerable zone. Structural vulnerability represents that 9% of the district area is under the very high vulnerability category, 48% high, 31% moderate, 4% low, and 8% falls under the very low category zone, whereas physical distance vulnerability comes up with a result that 23%, 38%, 23%, 7%, and 9% of the total area fall into very high, high, moderate, low, and very low categories, respectively.

Interpretation

The current work on seismic vulnerability assessment might be useful in reducing the risk and minimizing the losses due to earthquake.

背景地震是孟加拉国最具破坏性的灾害之一，脆弱性评估是地震风险评估的先决条件。因此，确定脆弱性对于降低未来的死亡人数至关重要。估计地震脆弱性的根本挑战是系统地了解所有潜在的地震相关损失。为此，本研究对孟加拉国锡尔赫特地区的地震脆弱性进行了评估。为了评估三种情况，即社会、结构和物理距离脆弱性，选择了几个标准，以充分识别地震风险。发现这项研究揭示了锡尔赫特区的脆弱地区。据透露，就社会脆弱性而言，Sylhet区9%的地区处于非常高、55%处于高、15%处于中等、17%处于低脆弱区，4%处于非常低脆弱区。结构脆弱性表明，9%的地区属于非常高的脆弱性类别，48%为高，31%为中等，4%为低，8%属于非常低类别，而物理距离脆弱性的结果是，23%、38%、23%、7%和9%的地区分别属于非常高、高、中、低和非常低类别。当前的地震脆弱性评估工作可能有助于降低地震风险和最大限度地减少地震损失。
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引用次数: 1
Experimental investigations on the cracking and mechanical responses of PMMA samples with two 3D embedded elliptic flaws under uniaxial compression 含两个三维嵌埋椭圆裂纹的PMMA单轴压缩开裂及力学响应试验研究
Geohazard Mechanics
Pub Date : 2023-03-01 DOI: 10.1016/j.ghm.2022.11.004
Xiaoping Zhou, Yunding Long, Wei Ye

In this paper, the cracking and mechanical responses are studied for the Polymethylmethacrylate (PMMA) sample with two three-dimensional embedded coplanar elliptic flaws subjected to uniaxial compression. The experimental results indicate that both the peak stress and crack initiation stress first decrease and then increase with increasing flaw angle, and they increase linearly with increasing flaw spacing. Moreover, five crack modes occur in these tested samples, including the coplanar secondary cracks, wing cracks, petal cracks, anti-wing cracks, and vertical giant cracks. The growth length of wing cracks is approximately equal to the length of the long axis of pre-existing flaw. However, the maximum width is roughly equal to half the length of the long axis of pre-existing elliptic flaw. The final failure modes include the splitting failure induced by wing cracks and vertical giant cracks, and the mixed tensile-shear failure induced by coplanar secondary cracks and wing cracks.

本文研究了具有两个三维嵌入共面椭圆缺陷的聚甲基丙烯酸甲酯（PMMA）试样在单轴压缩下的开裂和力学响应。实验结果表明，峰值应力和裂纹萌生应力均随裂纹角度的增大先减小后增大，且随裂纹间距的增大呈线性增大。此外，在这些测试样品中出现了五种裂纹模式，包括共面二次裂纹、翼裂纹、花瓣裂纹、反翼裂纹和垂直巨型裂纹。机翼裂纹的扩展长度大约等于预先存在的裂纹的长轴长度。然而，最大宽度大致等于预先存在的椭圆缺陷长轴长度的一半。最终失效模式包括机翼裂纹和垂直巨型裂纹引起的劈裂失效，以及共面二次裂纹和机翼裂纹引起的混合拉剪失效。
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引用次数: 0
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