International Journal of Rock Mechanics and Mining Sciences最新文献_第4页

Hard rock fragmentation by dynamic conical pick indentation under confining pressure 在约束压力下通过动态锥形镐压痕破碎硬岩

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-11 DOI: 10.1016/j.ijrmms.2024.105932

Pingkuang Luo , Diyuan Li , Wenkai Ru , Hao Gong , Mimi Wang

Mechanical mining and excavation in deep metal mines can be regarded as the process of crushing hard rock by conical pick indentation. In this study, a confining pressure loading device was designed and used to carry out dynamic conical pick indentation crushing tests under confining pressure conditions on three types of granite with varying strengths, using the Split Hopkinson Pressure Bar (SHPB). The objective was to quantitatively investigate the effect of confining pressure and rock strength on the indentation crushing characteristics of deep hard rocks. The results indicate that as the confining pressure increases from 5 MPa to 20 MPa, the dimensional parameters such as volume, diameter and depth of the impact groove decrease linearly, while parameters such as the specific energy, indentation force, indentation index and energy utilization rate progressively increase. The increase in the confining pressure inhibits the formation of internal cracks in the rock, enhancing its resistance to pick indentation, which in turn makes rock fragmentation more difficult. This creates unfavorable conditions for efficient rock breaking. Furthermore, rock strength plays a crucial role in the pick indentation process. The higher the rock strength, the greater its resistance to pick indentation, leading to increased energy consumption, accelerated wear of the conical picks, and reduced efficiency in rock breaking.

深部金属矿山的机械采矿和挖掘可视为通过锥形镐压痕破碎坚硬岩石的过程。本研究设计了一种封闭压力加载装置，并利用分体式霍普金森压力棒（SHPB）对三种不同强度的花岗岩进行了封闭压力条件下的动态锥形镐压痕破碎试验。目的是定量研究封闭压力和岩石强度对深层硬岩压痕破碎特性的影响。结果表明，随着约束压力从 5 兆帕增加到 20 兆帕，冲击槽的体积、直径和深度等尺寸参数呈线性下降，而比能、压痕力、压痕指数和能量利用率等参数则逐渐增加。约束压力的增加抑制了岩石内部裂缝的形成，增强了岩石对镐压痕的抵抗力，这反过来又增加了岩石破碎的难度。这就为高效破岩创造了不利条件。此外，岩石强度在镐头压入过程中起着至关重要的作用。岩石强度越高，对镐头压入的阻力就越大，从而导致能耗增加、锥形镐头磨损加快、破岩效率降低。

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引用次数: 0

Changes in the nanomechanical properties of the constituent minerals in the ductile fauske marble and the brittle kuru granite during progressive failure 韧性福斯克大理石和脆性库鲁花岗岩在渐进破坏过程中组成矿物的纳米力学特性变化

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-01 DOI: 10.1016/j.ijrmms.2024.105853

Wenkai Wan , Charlie C. Li , Siqi Liu , Jianying He

The nanoscale elastic moduli and hardness of the constituent minerals of the Class II Kuru granite and the Class I Fauske marble were experimentally investigated. The aims were to correlate the microcrack patterns with the nanomechanical properties of the minerals, and to help understand the important roles of the nanomechanical properties of the minerals in brittle and ductile behaviors. Cylindrical rock specimens were uniaxially loaded to various stress levels in both the pre- and post-peak stages. The specimens were then unloaded to zero, and two thin sections –– one parallel with and the other perpendicular to the loading direction –– were prepared from each specimen. Nano-indentation tests were conducted on the thin sections to measure the elastic moduli and hardness of the major constituent minerals in the rocks. The test results showed that both the elastic moduli and hardness of the minerals abruptly decreased when the applied stress was above 80 % of the uniaxial compressive strength of the rock in the pre-peak stage and also in the entire post-peak stage. At the same time, the values of the two properties became more scattered with increasing damage to the minerals. The number of intragranular cracks was significantly less in the harder quartz and microcline than in the softer calcite. The abundant intragranular cracks in the calcite dissipated most of the strain energy in the Class I marble, such that the rock was not burstable after failure. A small number of intragranular cracks were created in the quartz and microcline in the Class II granite, such that most of the strain energy in the minerals was released to eject rock after failure. Intragranular cracking is thus a key factor in determining whether a rock is burst-prone or not.

实验研究了二级库鲁花岗岩和一级法斯克大理石组成矿物的纳米级弹性模量和硬度。目的是将微裂纹模式与矿物的纳米力学性能联系起来，帮助理解矿物的纳米力学性能在脆性和韧性行为中的重要作用。圆柱形岩石试样在峰值前和峰值后阶段均受到不同应力水平的单轴加载。然后将试样卸载至零，从每个试样上制备两个薄片--一个平行于加载方向，另一个垂直于加载方向。对薄片进行纳米压痕测试，以测量岩石中主要成分矿物的弹性模量和硬度。测试结果表明，当施加的应力超过岩石单轴抗压强度的 80% 时，岩石的弹性模量和硬度都会突然下降。同时，这两种属性的值随着矿物受损程度的增加而变得更加分散。较硬的石英和微晶石的粒内裂缝数量明显少于较软的方解石。方解石中大量的粒内裂缝耗散了 I 级大理石中的大部分应变能，因此岩石在破坏后不会爆裂。二级花岗岩中的石英和微晶石中产生了少量粒内裂缝，因此矿物中的大部分应变能都被释放出来，使岩石在破坏后喷出。因此，晶内裂缝是决定岩石是否易爆的关键因素。

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引用次数: 0

A multi-step calibration strategy for reliable parameter determination of salt rock mechanics constitutive models 可靠确定盐岩力学组成模型参数的多步骤校准策略

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-09-28 DOI: 10.1016/j.ijrmms.2024.105922

Hermínio T. Honório , Maartje Houben , Kevin Bisdom , Arjan van der Linden , Karin de Borst , Lambertus J. Sluys , Hadi Hajibeygi

The storage of renewable hydrogen in salt caverns requires fast injection and production rates to cope with the imbalance between energy production and consumption. This raises concerns about the mechanical stability of salt caverns under such operational conditions. The use of appropriate constitutive models for salt mechanics is an important step in investigating this issue, therefore many constitutive models with several parameters have been presented in the literature. However, a robust calibration strategy to reliably determine which model and parameter set represents the given rock, based on stress–strain data sets, remains an unsolved challenge. In this paper, for the first time in the community, we present a multi-step strategy to determine a single parameter set based on many deformation data sets for salt rocks. Towards this end, we first develop a comprehensive constitutive model able to capture all relevant nonlinear deformation physics of transient, reverse, and steady-state creep. The determination of the single set of representative material parameters is then achieved by framing the calibration process as an optimization problem, for which the global Particle Swarm Optimization algorithm is employed. To allow for dynamic data integration, a multi-step calibration strategy is developed for a situation where experiments are included one at a time, as they become available. Additionally, due to the existing mild heterogeneity in the experimental rock samples, our optimization strategy is made flexible to allow for this slight heterogeneity. The devised optimization strategy, based on the multi-physics comprehensive constitutive modeling framework, results in a single set of representative material properties of all the deformation data sets. As a rigorous mathematical analysis for the presented method and the lack of relevant experimental data sets, we consider a wide range of synthetic experimental data sets, inspired by the existing sparse relevant data in the literature. The results of our performance analyses show that the proposed calibration strategy is robust. Moreover, the results become increasingly more accurate as more data sets become available.

在盐洞中储存可再生氢需要快速注入和生产，以应对能源生产和消费之间的不平衡。这就引起了人们对盐洞在这种运行条件下的机械稳定性的关注。使用适当的盐力学构成模型是研究这一问题的重要一步，因此文献中提出了许多具有多个参数的构成模型。然而，如何根据应力应变数据集可靠地确定哪个模型和参数集代表给定的岩石，仍然是一个尚未解决的难题。在本文中，我们首次提出了一种多步骤策略，可根据盐岩的多个变形数据集确定单一参数集。为此，我们首先开发了一个全面的构成模型，能够捕捉瞬态、反向和稳态蠕变的所有相关非线性变形物理特性。然后，将校准过程作为一个优化问题，采用全局粒子群优化算法来确定单组代表性材料参数。为了实现动态数据集成，我们开发了一种多步骤校准策略，以便在实验可用时一次纳入一个实验。此外，由于实验岩石样本中存在轻微的异质性，我们的优化策略也变得灵活，以适应这种轻微的异质性。所设计的优化策略基于多物理场综合结构建模框架，可为所有变形数据集提供一套具有代表性的材料属性。为了对所提出的方法进行严格的数学分析，并解决缺乏相关实验数据集的问题，我们从文献中现有的稀疏相关数据中汲取灵感，考虑了一系列合成实验数据集。我们的性能分析结果表明，所提出的校准策略是稳健的。此外，随着可用数据集的增多，结果也越来越精确。

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引用次数: 0

Fault slip behaviors and frictional stability controlled by particle size of fault gouge under fluid injection 注入流体条件下由断层破碎带粒径控制的断层滑移行为和摩擦稳定性

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-09-28 DOI: 10.1016/j.ijrmms.2024.105919

Bin Liu , Zhi Geng , Yongshui Kang , Xuewei Liu , Yuan Zhou , Quansheng Liu , Youqi Huang , Xiubin Zhou

Understanding the control mechanism of fault rock particle size in fluid-induced fault slip and rupture processes is crucial for mitigating the seismic risks associated with large-scale fluid injection. Here, we conducted laboratory experiments to present the effects of fault rock particle size on slip behavior, friction, and slip modes under fluid injection. Our results demonstrate that the particle size of the gouge controls the initiation of fault slip events and that the fluid pressure required for the initial fault slip is negatively correlated with the rock particle size. The increase in rock particle size can weaken the faults and induce the transition of the fault slip mode from creep to slow stick-slip events, which leads to the occurrence of seismic events. These results reveal the particle size of fault gouge exerts a potentially dominant control on the slip behavior, slip modes, and frictional characteristics of faults under fluid injection, providing crucial insights into fault slip and seismic events.

了解断层岩粒度在流体诱发断层滑移和破裂过程中的控制机制对于降低大规模流体注入带来的地震风险至关重要。在此，我们进行了实验室实验，以展示在流体注入情况下，断层岩颗粒大小对滑动行为、摩擦力和滑动模式的影响。我们的结果表明，冲沟的颗粒大小控制着断层滑动事件的发生，而初始断层滑动所需的流体压力与岩石颗粒大小呈负相关。岩石颗粒尺寸的增加会削弱断层，诱发断层滑动模式从蠕变到缓慢粘滑事件的转变，从而导致地震事件的发生。这些结果揭示了断层破碎带的粒度对注入流体作用下断层的滑移行为、滑移模式和摩擦特性具有潜在的主导控制作用，为研究断层滑移和地震事件提供了重要依据。

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引用次数: 0

Difference in rock-breaking characteristics between water-coupling blasting and air-coupling blasting 水耦合爆破与空气耦合爆破的破岩特性差异

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-09-27 DOI: 10.1016/j.ijrmms.2024.105924

Zhiwei Ye , Jianhua Yang , Ming Chen , Chi Yao , Xiaobo Zhang , Yongli Ma , Chuangbing Zhou

The water-coupling blasting (WCB) technology has received widespread attention due to its advantages of high efficiency and environmental protection. However, the parameters of WCB in practical engineering are generally determined based on the experience and standards of air-coupling blasting (ACB), leading to poor blasting effects and wastage of explosive energy. The study focuses on comparing the rock-breaking effects of shock waves and explosive gases between WCB and ACB to offer insights for optimizing the design of WCB. Firstly, the stress field in blasting with different coupling mediums was calculated. Then, the shock failure characteristics of rocks between WCB and ACB were analyzed. The results show that the radius of shock failure zones decreases with the increasing decoupling coefficient in WCB and ACB. On this basis, a model for calculating the shock failure range in WCB and ACB was proposed. This model can be utilized to estimate the percentage of fine-grained stone in the two types of blasting. Further, a method for distinguishing between the rock-breaking effects of shock waves and explosive gases was proposed based on the numerical simulation results of blasting damage. A comparative analysis between WCB and ACB on the rock-breaking volume by shock waves and gases was conducted. The results indicate that the failure volumes of rocks induced by shock waves and gases in WCB are 1.4–2.1 times greater than those in ACB, with a decoupling coefficient ranging from 1.26 to 1.71. Finally, a method for determining the charging structure in WCB was discussed, which has been preliminarily validated by field tests. The findings can help regulate rock-breaking effects in blasting by rationally selecting coupling mediums and charging constructions.

水耦合爆破（WCB）技术因其高效、环保等优点受到广泛关注。然而，在实际工程中，水煤浆爆破的参数一般都是根据空气耦合爆破（ACB）的经验和标准确定的，导致爆破效果不佳和爆炸能量的浪费。本研究重点比较了 WCB 和 ACB 的冲击波和爆炸气体的破岩效果，为优化 WCB 的设计提供启示。首先，计算了不同耦合介质爆破时的应力场。然后，分析了 WCB 和 ACB 之间岩石的冲击破坏特征。结果表明，随着 WCB 和 ACB 去耦系数的增大，冲击破坏区的半径会减小。在此基础上，提出了计算 WCB 和 ACB 冲击破坏范围的模型。该模型可用于估算两种爆破中细粒石材的比例。此外，还根据爆破破坏的数值模拟结果，提出了一种区分冲击波和爆炸气体破岩效果的方法。对 WCB 和 ACB 在冲击波和气体作用下的岩石破坏量进行了比较分析。结果表明，在 WCB 中，冲击波和气体诱发的岩石破坏体积是 ACB 的 1.4-2.1 倍，解耦系数在 1.26-1.71 之间。最后，讨论了一种确定 WCB 中装药结构的方法，该方法已通过现场试验得到初步验证。这些发现有助于通过合理选择耦合介质和装药结构来调节爆破中的破岩效果。

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引用次数: 0

A thermo-mechanical phase-field model for mixed-mode fracture and its application in rock-like materials 混合模式断裂的热机械相场模型及其在类岩材料中的应用

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-09-27 DOI: 10.1016/j.ijrmms.2024.105907

Qiang Yue , Qiao Wang , Timon Rabczuk , Wei Zhou , Xiaoying Zhuang , Xiaolin Chang

Thermally induced fracture is a common phenomenon for concrete and rock-like materials, which presents a significant challenge to numerical modelling. In this work, a thermo-mechanical model for mixed-mode fracture based on phase-field method is proposed. This approach overcomes the difficulties of modelling the thermally induced cracking process when it comes to complex fracture patterns. To simulate different failure modes in thermo-mechanical conditions, the model's constitutive expression includes a unified failure criterion that takes into account both tensile and shear strengths. The proposed formulation provides a length scale insensitive response for brittle materials such as rocks, although other prevalent phase-field theories for purely mechanical fracture can also be involved. The computational results of the representative examples for rock-like materials are highly consistent with prior findings. It demonstrates that the presented model can effectively reproduce the thermally induced cracking process for various cracking patterns, such as tensile, shear, and tensile-shear fractures, indicating the method's remarkable capabilities for further research.

热诱导断裂是混凝土和类岩材料的一种常见现象，这给数值建模带来了巨大挑战。本研究提出了一种基于相场法的混合模式断裂热机械模型。这种方法克服了复杂断裂模式下热致开裂过程建模的困难。为了模拟热机械条件下的不同破坏模式，模型的构成表达式包括一个统一的破坏准则，该准则同时考虑了拉伸强度和剪切强度。所提出的公式为岩石等脆性材料提供了对长度尺度不敏感的响应，尽管也可以涉及其他纯机械断裂的流行相场理论。岩石类材料代表性实例的计算结果与之前的研究结果高度一致。研究表明，所提出的模型可以有效地再现各种裂纹模式（如拉伸、剪切和拉伸剪切断裂）的热诱导裂纹过程，这表明该方法具有卓越的能力，值得进一步研究。

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引用次数: 0

Investigation on the pore size characteristics and mechanical properties of grouting materials scoured by flow water 流水冲刷灌浆材料的孔径特征和力学性能研究

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-09-25 DOI: 10.1016/j.ijrmms.2024.105923

Longji Wu, Zhijun Wu, Lei Weng, Yang Liu, Zhaofei Chu, Xiangyu Xu

Investigating the pore size characteristics and mechanical properties of the stone bodies formed by residual grout is crucial for understanding the authentic permeability and load-bearing capacity of grouting materials after being scoured by water flow. In this study, the pore size distribution, porosity, uniaxial compressive strength (UCS), and elastic modulus (E) of stone bodies formed by residual grout from polyacrylate latex-modified cement grouting material (PLMC) were systematically investigated, and pure cement grout (PC) as a control group. First, scouring tests were conducted on grouting materials with various water-to-cement ratios (w/c, 0.6–0.8) and polymer-cement ratios (p/c, 0–0.2) under different flow velocities (0–1 m/s). Subsequently, the pore size characteristics of stone bodies formed by residual grout under various conditions were studied via nuclear magnetic resonance test. Finally, the uniaxial compression tests were conducted to investigate the impact of water scouring on the mechanical properties of grouting materials, and the relationship between pore size characteristics and macro mechanical responses was analyzed. Results show that the stone bodies formed by residual grout compared to the non-scoured state develop mesopores and macropores, and the number of micropores also increased significantly. This porosity escalation results in a reduction in UCS and E. When the flow velocity reaches 1 m/s, the porosity of PLMC with w/c = 0.8 increases by 2.95 %, while UCS decreases by 14.6 % and E decreases by 37.4 %. PC demonstrates more pronounced changes, with a porosity increase of 7.01 %, UCS decreases by 32.9 %, and E decreases by 41.5 %. With the rise in w/c, the deterioration of pore structure and mechanical properties of the stone bodies formed by residual grout is more significant compared to the non-scoured state. Increasing p/c can mitigate the deterioration of the pore structure and mechanical properties. The findings provide meaningful guidance for the grouting reinforcement under dynamic water conditions.

研究残余灌浆料形成的石体的孔径特征和力学性能，对于了解灌浆材料经水流冲刷后的真实渗透性和承载能力至关重要。本研究系统研究了聚丙烯酸酯胶乳改性水泥灌浆材料（PLMC）残留灌浆料形成的石体的孔径分布、孔隙率、单轴抗压强度（UCS）和弹性模量（E），并以纯水泥灌浆料（PC）作为对照组。首先，对不同水灰比（w/c，0.6-0.8）和聚合物水泥比（p/c，0-0.2）的灌浆材料在不同流速（0-1 m/s）下进行了冲刷试验。随后，通过核磁共振测试研究了不同条件下残余灌浆料形成的石体的孔径特征。最后，通过单轴压缩试验研究了水冲刷对灌浆材料力学性能的影响，并分析了孔径特征与宏观力学响应之间的关系。结果表明，与未冲刷状态相比，残留灌浆料形成的石体会产生中孔和大孔，微孔数量也显著增加。当流速达到 1 米/秒时，w/c = 0.8 的 PLMC 的孔隙率增加了 2.95%，而 UCS 减少了 14.6%，E 减少了 37.4%。PC 的变化更为明显，孔隙率增加了 7.01%，UCS 减少了 32.9%，E 减少了 41.5%。与未浇注状态相比，随着 w/c 的增加，残留灌浆料形成的石体的孔隙结构和机械性能的劣化更为显著。提高 p/c 可以缓解孔隙结构和机械性能的恶化。研究结果为动水条件下的灌浆加固提供了有意义的指导。

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引用次数: 0

Effects of crystal orientation, temperature, deviatoric stress, and confining stress on creep of rock salt 晶体取向、温度、偏差应力和约束应力对岩盐蠕变的影响

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-09-24 DOI: 10.1016/j.ijrmms.2024.105913

Timothy J. Truster, Amirsalar Moslehy, Khalid A. Alshibli

The creep of rock salt greatly influences the performance and safety of rock salt caverns when they are used as an underground repository for oil, nuclear waste, or other hazardous materials. Creep may cause shearing of casings of oil wells drilled through thick layers of salt rock formation. The crystallographic structure of salt rock grains, in-situ deviatoric stress changes caused by excavation, confining stress from the surrounding environment, and ambient temperature can have a significant impact on the creep behavior of rock salt. Although the creep behavior of polycrystalline rock salt has been extensively studied by many researchers, the creep behavior of single-crystal natural rock salt is not yet fully understood. This paper investigates the influence of crystal orientation, temperature, deviatoric stress, and confining stress on the creep behavior of single-crystal and polycrystalline rock salt. 42 long-term creep experiments with various temperatures, confining stresses, and deviatoric stresses were conducted on natural single-crystal specimens. The temperatures were 20, 100, and 150 °C, the confining stresses were 0.1, 1.0, and 5.0 MPa, and the various deviatoric stresses were applied in different loading directions with respect to the specimen's crystal orientations. Additionally, 18 long-term creep experiments were performed on synthetic polycrystalline specimens with wet grain boundaries at temperatures of 20, 100, and 150 °C, at confining stresses of 0.1, 1.0, and 5.0 MPa, and various deviatoric stresses. The effects of the mentioned experimental conditions on the accumulated axial strain, transient strain rate, and steady-state strain rate during the creep of rock salt were then examined and discussed in detail. Moreover, the influence of temperature, deviatoric stress, and confining stress on the steady-state creep of single crystal rock salt is examined within the context of existing polycrystalline creep data available in the literature.

当岩盐洞穴用作石油、核废料或其他有害物质的地下贮藏库时，岩盐的蠕变会极大地影响岩盐洞穴的性能和安全。蠕变可能会导致钻过厚盐岩层的油井套管发生剪切。盐岩晶粒的晶体结构、挖掘造成的原位偏差应力变化、周围环境的约束应力以及环境温度都会对岩盐的蠕变行为产生重大影响。虽然许多研究人员已经对多晶岩盐的蠕变行为进行了广泛研究，但对单晶天然岩盐的蠕变行为还没有完全了解。本文研究了晶体取向、温度、偏差应力和约束应力对单晶和多晶岩盐蠕变行为的影响。在天然单晶试样上进行了 42 次不同温度、约束应力和偏差应力的长期蠕变实验。温度分别为 20、100 和 150 °C，约束应力分别为 0.1、1.0 和 5.0 MPa，各种偏差应力施加在与试样晶体方向不同的加载方向上。此外，还对具有湿晶界的合成多晶试样进行了 18 次长期蠕变实验，温度分别为 20、100 和 150 °C，约束应力分别为 0.1、1.0 和 5.0 MPa，并施加了各种偏差应力。然后详细研究和讨论了上述实验条件对岩盐蠕变过程中累积轴向应变、瞬态应变率和稳态应变率的影响。此外，还结合文献中现有的多晶蠕变数据，研究了温度、偏差应力和约束应力对单晶岩盐稳态蠕变的影响。

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引用次数: 0

Acoustic emission and 4D X-ray micro-tomography for monitoring crack propagation in rocks 用于监测岩石裂缝扩展的声发射和 4D X 射线微断层扫描技术

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-09-22 DOI: 10.1016/j.ijrmms.2024.105917

Daniel Kytýř , Petr Koudelka , Daria Drozdenko , Martin Vavro , Tomáš Fíla , Václav Rada , Leona Vavro , Kristián Máthis , Kamil Souček

Acoustic emission (AE) and 4D X-ray computed tomography (4D XCT) were used simultaneously to study crack initiation and propagation in two different types of quartz-rich sandstones during the four-point bending experiments. Statistical analysis of the AE response indicated the failure mechanisms and their dynamics. The characteristic changes observed in the AE response defined the timing of the bending interruptions for XCT scanning to reveal the development of the crack. It was possible to quantitatively describe the developing cracks in their dimensions and volume and relate this information to the rate of decrease in the post-peak region of the material response. It could be concluded that the combination and concurrent use of AE and XCT techniques represents a highly effective and reliable instrument for observation, description, analysis of the crack propagation process, and rock disintegration in detail at a microscale level. With regard to the specific sandstones studied, Mšené sandstone is softer, respectively, less brittle, while Kocbeře sandstone is characterised by a more brittle behaviour accompanied by an AE signal with higher amplitudes compared to those of Mšené.

在四点弯曲实验中，同时使用声发射（AE）和四维 X 射线计算机断层扫描（4D XCT）来研究两种不同类型富含石英的砂岩中裂纹的产生和扩展。对 AE 响应的统计分析显示了破坏机制及其动态变化。在 AE 响应中观察到的特征变化确定了 XCT 扫描显示裂纹发展的弯曲中断时间。可以定量描述裂纹发展的尺寸和体积，并将这些信息与材料响应峰值后区域的下降率联系起来。可以得出结论，AE 和 XCT 技术的结合和同时使用是一种非常有效和可靠的仪器，可用于观察、描述和分析裂纹扩展过程，以及岩石在微观层面上的详细崩解情况。就所研究的特定砂岩而言，Mšené 砂岩较软，脆性较低，而 Kocbeře 砂岩的特点是脆性较高，与 Mšené 砂岩相比，AE 信号的振幅较高。

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引用次数: 0

Grading scalping and sample size effects on critical shear strength of mine waste rock through laboratory and in-situ testing 通过实验室和原位测试，分级标度和样本大小对矿山废石临界剪切强度的影响

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-09-21 DOI: 10.1016/j.ijrmms.2024.105915

Gilbert Girumugisha , Carlos Ovalle , Serge Ouellet

Geotechnical stability analyses of mine waste rock (WR) piles require the critical friction angle (ϕ_cr) of the coarse blasted rock. However, due to the presence of oversized rock clasts, shear strength can only be characterized on small samples prepared using grading scaling techniques, such as scalping. Thus, considering a testing device able to handle samples of characteristic size D, the material should be scaled down to a maximum particle size d_max given by the minimum sample aspect ratio α = D/d_max. However, a practical concern about how far the size scale can be reduced while keeping representative results remains a matter of debate in the geotechnical community. International standards do not agree on the minimum recommended α, and its effects on the mechanical behavior remain poorly understood. This paper aims to investigate the grading effects and sample size effects on ϕ_cr of WR materials using the scalping technique, to provide insights on the minimum recommended α. Triaxial tests were conducted on loose and dense samples of diameters D = 150 and 300 mm. Samples were scalped from field material having d_max = 75 mm, to allow a range of α from 4 to 30. Additionally, one of the world largest in-situ direct shear boxes (120 × 120 × 38 cm³) was developed to test the same WR material. The results show that scalping is an appropriate technique to assess the critical shear strength of WR. The minimum α for ϕ_cr assessment in triaxial testing is not sensitive to grading nor sample size, but it is affected by sample density. The aspect ratio was found to be α ≥ 12 and α ≥ 16 for loose and dense samples, respectively. This finding advocates that α values recommended by worldwide standards, such as ASTM D7181-20, might be too low and should be revisited after comprehensive testing.

矿山废石（WR）桩的岩土稳定性分析需要粗爆破岩石的临界摩擦角（jcr）。然而，由于存在过大的岩石碎块，只能通过分级缩放技术（如缩放）制备的小样本来确定剪切强度。因此，考虑到测试设备能够处理特征尺寸为 D 的样品，材料应按比例缩小到最大粒度 dmax，该粒度由最小样品长宽比 α = D/dmax 给出。然而，在岩土工程界，如何在保持结果代表性的同时缩小粒度仍是一个值得关注的实际问题。国际标准并未就推荐的最小值 α 达成一致，而且人们对其对力学行为的影响仍知之甚少。本文旨在利用剥离技术研究 WR 材料的级配效应和样本大小对 ϕcr 的影响，从而为推荐的最小 α 提供见解。样品是从 dmax = 75 毫米的现场材料中剥取的，因此 α 的范围在 4 到 30 之间。此外，还开发了世界上最大的原位直接剪切箱（120 × 120 × 38 立方厘米）之一，以测试相同的 WR 材料。结果表明，缩放是评估 WR 临界剪切强度的一种适当技术。在三轴测试中评估ϕcr 的最小 α 对级配和样品大小不敏感，但会受到样品密度的影响。研究发现，松散和致密样品的长宽比分别为 α ≥ 12 和 α ≥ 16。这一发现表明，ASTM D7181-20 等世界标准推荐的 α 值可能过低，应在全面测试后重新考虑。

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引用次数: 0