International Journal of Rock Mechanics and Mining Sciences最新文献_第2页

The role of annealing and grain boundary controls on the mechanical properties of limestones and marbles 退火和晶界控制对灰岩和大理石机械特性的作用

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-28 DOI: 10.1016/j.ijrmms.2024.105926

Chemical and mechanical processes are coupled in many geological and geochemical environments. Reactive processes anneal defects and restructure grain boundaries, modifying their elastic properties, levels of internal friction, wave propagation rates and fracture behaviors. The nature of these changes is, however, contingent on the initial state of the rock. In this study, impulse excitation was used to measure changes in mechanical properties as a function of dry and steam heating time at 300 °C for three carbonate rocks: Carrara marble, Carthage marble (Burlington Limestone), and Texas Cream limestone (Edwards limestone), with initial porosities of about 1 %, 3 %, and 27 %, respectively. Frequency-dependent phenomena along with mineral recrystallization were observed. This was coupled with small-angle X-ray and neutron scattering analysis to determine the relationship between changes in bulk mechanical and microstructural properties. An observed decrease in both the Young's and shear moduli in the experimental limestones as a function of heating time reflects and quantifies a reduction in the stiffness of the rock due to annealing. The internal friction of the samples first increases then decreases with reaction time, reflecting defect annealing, but this was balanced against grain boundary dissolution apparently driven by condensation of steam in the confined grain-boundary environment. This suggests an increase in the boiling point under confinement leading to dissolution, increased porosity and widening of the grain boundaries. In addition, comparison of small-angle X-ray and neutron scattering results suggests that it is inappropriate to assume that pores are empty for quantitative analysis of typical small-angle scattering samples.

在许多地质和地球化学环境中，化学和机械过程是相互关联的。反应过程会使缺陷退火并重组晶界，从而改变其弹性特性、内摩擦力水平、波传播速度和断裂行为。然而，这些变化的性质取决于岩石的初始状态。在这项研究中，我们使用脉冲激励来测量三种碳酸盐岩在 300 °C 下的机械特性变化与干燥和蒸汽加热时间的函数关系：卡拉拉大理石、迦太基大理石（伯灵顿石灰岩）和德克萨斯奶油石灰岩（爱德华兹石灰岩）的初始孔隙率分别约为 1%、3% 和 27%。观察到频率相关现象以及矿物再结晶。结合小角 X 射线和中子散射分析，确定了块体机械性能和微观结构性能变化之间的关系。观察到实验石灰岩的杨氏模量和剪切模量都随加热时间而降低，这反映并量化了退火导致的岩石刚度降低。随着反应时间的延长，样品的内摩擦力先增大后减小，这反映了缺陷退火，但这又与晶界溶解相平衡，显然是由于蒸汽在封闭的晶界环境中凝结造成的。这表明，在密闭条件下，沸点升高会导致溶解、孔隙率增加和晶界扩大。此外，对小角 X 射线和中子散射结果的比较表明，在对典型的小角散射样品进行定量分析时，假设孔隙是空的是不恰当的。

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引用次数: 0

An energy-driven crushing-plasticity coupling model for grain crushing in porous rocks 多孔岩石中晶粒破碎的能量驱动破碎-塑性耦合模型

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-25 DOI: 10.1016/j.ijrmms.2024.105931

This research develops an energy-driven constitutive model designed to tackle the complex phenomenon of grain crushing in porous rocks. Initially, a novel coupled relationship is proposed to integrate various energy dissipation mechanisms, including both plastic and crushing effects, using spherical polar coordinates. This approach results in a robust coupling of energy dissipation, providing a comprehensive depiction of the influence of grain crushing on plastic deformation. An energy-based yield criterion is then formulated by comparing elastic potential energy contours with experimental findings, and the behaviour of crushing hardening is examined through energy evolution. Flow rules are subsequently derived, both independently and with consideration of plasticity-crushing coupling. Finally, validation against a range of experimental tests highlights the model's versatility. The proposed model enhances the understanding of rock-crushing issues from an energy perspective and demonstrates simplicity with only 4 or 5 easily calibrated parameters.

这项研究开发了一种能量驱动构造模型，旨在解决多孔岩石中晶粒破碎的复杂现象。首先，提出了一种新颖的耦合关系，利用球极坐标整合各种能量耗散机制，包括塑性效应和挤压效应。这种方法实现了能量耗散的稳健耦合，全面描述了晶粒破碎对塑性变形的影响。然后，通过将弹性势能等值线与实验结果进行比较，制定了基于能量的屈服标准，并通过能量演化研究了压碎硬化的行为。随后推导出流动规则，既包括独立的流动规则，也包括考虑塑性-挤压耦合的流动规则。最后，根据一系列实验测试进行验证，突出了模型的多功能性。所提出的模型从能量角度加强了对岩石破碎问题的理解，并且只需 4 或 5 个易于校准的参数就能显示出其简易性。

引用次数: 0

Numerical simulation on multi-well fracturing considering multiple thin layers in vertical direction 考虑垂直方向多薄层的多井压裂数值模拟

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-25 DOI: 10.1016/j.ijrmms.2024.105951

Multiwell fracturing is a key technology for developing shale gas and shale oil reservoirs. In this study, a multiple planar 3D (PL3D) fracture simulator that can capture multiple thin layers was developed to examine the propagation of multiple fractures during multicluster fracturing in multiple horizontal wells. The simulator considers multiple thin layers in the vertical direction. The results of the model are validated against the analytical solution of a single radial fracture and the implicit level set algorithm (ILSA). Using the simulator, a series of numerical simulations based on the field case are performed to investigate the fracture propagation mechanism of multiwell fracturing. The completion sequence, well placement pattern, well spacing, and cluster spacing are investigated to optimize the treatment parameters. The effective fracture area is used to quantitatively describe the stimulation effect. The adaptability of the completion sequence and well placement pattern is also analysed from the perspective of “frac hits”. The results show that the completion sequence has a critical influence on the stimulation effect and fracture geometry. From the perspective of avoiding “frac-hit” fractures, fracturing the low-stress layer can form an “artificial stress barrier”, which slightly protects the well from interference from other fractures. The staggered well pattern is better than the stacked well pattern. Compared with the stacked pattern, the staggered pattern can reduce the overlap area of fractures by 80 %, which greatly reduces the probability of “frac-hits”. With increasing well spacing from 200 m to 500 m, the fracture area increases by 25 %, and the degree of uneven stimulation between the two pay zones also increases by 6 %. Considering that a small well spacing is prone to “frac hits”, a large well spacing leads to an unstimulated area between two wells, and a 350 m well spacing is optimal. The effective fracture area decreases slightly with increasing perforation cluster spacing, but the fracture geometry becomes much more regular. The results can be helpful for the field design of multiwell fracturing.

多井压裂是开发页岩气和页岩油藏的一项关键技术。本研究开发了一种可捕捉多薄层的多平面三维（PL3D）压裂模拟器，以研究多水平井多簇压裂过程中多条裂缝的传播情况。该模拟器考虑了垂直方向上的多个薄层。该模型的结果与单一径向裂缝的分析解法和隐式水平集算法（ILSA）进行了验证。利用该模拟器，进行了一系列基于现场案例的数值模拟，以研究多井压裂的裂缝传播机理。研究了完井顺序、井位模式、井间距和簇间距，以优化处理参数。有效压裂面积用于定量描述刺激效果。还从 "压裂命中率 "的角度分析了完井顺序和布井模式的适应性。结果表明，完井顺序对刺激效果和裂缝几何形状有着至关重要的影响。从避免 "压裂命中 "裂缝的角度来看，压裂低应力层可以形成 "人工应力屏障"，稍微保护油井不受其他裂缝的干扰。交错井型优于叠层井型。与叠层井型相比，交错井型可减少 80% 的裂缝重叠面积，大大降低了 "压裂命中 "的概率。随着井距从 200 米增加到 500 米，压裂面积增加了 25%，两个有效层之间的不均匀激励程度也增加了 6%。考虑到小井距容易出现 "压裂命中"，大井距导致两口井之间出现非刺激区，因此最佳井距为 350 米。随着射孔群间距的增加，有效压裂面积略有减少，但压裂几何形状变得更加规则。这些结果有助于多井压裂的现场设计。

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引用次数: 0

Exposure behavior and drilling efficiency of basalt fiber composite impregnated diamond bits in hard granite 玄武岩纤维复合材料浸渍金刚石钻头在硬质花岗岩中的暴露行为和钻进效率

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-25 DOI: 10.1016/j.ijrmms.2024.105950

Impregnated diamond bits (IDBs) are widely used for drilling in hard formations. To improve the drilling efficiency and exposure behavior of IDBs in granite, three types of Cu-based basalt fiber (BF) composite IDBs were designed and prepared by using the medium-frequency induction hot-pressing and sintering method, in which 0 wt% BF and 25 vol% diamond were used in 0BF25D IDB, 1 wt% BF and 25 vol% diamond were used in 1BF25D IDB, 1 wt% BF and 20 vol% diamond were used in 1BF20D IDB. The drilling efficiency of each IDB was tested under different drilling pressures (WOB), and the exposure behavior of IDBs was investigated by scanning electron microscopy and ultra field microstructural characterization. Results show that drilling granite with grade 9 drillability, low drilling pressure can drill successfully with the addition of BF. The average rate of penetration (ROP) of 1BF20D IBD under 6 kN WOB was 4.78 m/h, which was improved by 60 %∼80 %, energy consumption decreased by 66 % for each meter, torque (TOB) decreased, and rotational speed (RPM) was more stable during the drilling process. The addition of BF and reasonable diamond concentration enhanced the holding power of the diamond which promoted the exposure of the diamond. The average exposed height of the diamond in 1BF20D IDB reached 121.2 μm with 22 %–29 % of the whole diamond.

浸渍金刚石钻头（IDB）被广泛应用于硬地层的钻探。为了提高浸渍金刚石钻头在花岗岩中的钻进效率和暴露性能，采用中频感应热压烧结法设计并制备了三种铜基玄武岩纤维（BF）复合材料浸渍金刚石钻头，其中 0BF25D 浸渍金刚石钻头使用了 0 wt% BF 和 25 vol% 金刚石，1BF25D 浸渍金刚石钻头使用了 1 wt% BF 和 25 vol% 金刚石，1BF20D 浸渍金刚石钻头使用了 1 wt% BF 和 20 vol% 金刚石。在不同的钻孔压力（WOB）下测试了每种 IDB 的钻孔效率，并通过扫描电子显微镜和超场微结构表征研究了 IDB 的暴露行为。结果表明，添加 BF 后，可钻性为 9 级、钻压较低的花岗岩也能成功钻进。在 6 kN WOB 条件下，1BF20D IBD 的平均钻进速度（ROP）为 4.78 m/h，提高了 60%∼80%，每米能耗降低了 66%，扭矩（TOB）降低，钻进过程中转速（RPM）更加稳定。BF 的添加和合理的金刚石浓度增强了金刚石的保持力，从而促进了金刚石的裸露。在 1BF20D IDB 中，金刚石的平均裸露高度达到 121.2 μm，占整个金刚石的 22%-29%。

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引用次数: 0

Determination of the REV size for heterogeneous rocks with different grain sizes: Deep learning and numerical approaches 确定具有不同粒度的异质岩石的 REV 尺寸：深度学习和数值方法

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-24 DOI: 10.1016/j.ijrmms.2024.105940

Accurate determination of the representative elementary volume (REV) size plays a pivotal role in analysing the mechanical properties and failure processes of heterogeneous rocks in complex engineering environments. In this study, a novel microstructure modelling strategy (NMMS) for determining the REV size is proposed by combining deep learning and an improved phase-field method (PFM). Micro- and macroscale experiments are systematically conducted to determine the real microstructural characteristics and mechanical properties of heterogeneous rocks with different grain sizes. On the basis of this experimental evidence, geometric models of different sizes were reconstructed through deep learning to avoid the limitations of human-based methods, and an improved PFM was used for numerical calculations. These models were then employed to perform numerical tests under uniaxial loading conditions, and the coefficient of variation was introduced to determine the REV size of heterogeneous rocks with different grain sizes. The research findings indicate that the final REV size is the maximum value of the REVs defined by the evaluation properties within an acceptable coefficient of variation. At a criterion of 5% for the coefficient of variation, the REV sizes are 60 mm

\times

60 mm, 70 mm

\times

70 mm, and 90 mm

\times

90 mm for fine-medium-grained (FMG), medium-grained (MG), and coarse-grained (CG) rocks, respectively. Furthermore, the REV determined by the NMMS was applied to investigate the effects of microstructure on macromechanical properties and damage evolution under triaxial loading conditions. The numerical results show that the NMMS can accurately predict the macromechanical properties and microcracking patterns of heterogeneous rocks, especially the intracrystalline cracks in feldspar, the interfacial cracks in gravel, and the “voids” of cracks in biotite. This research can provide some basic references for the optimal choice of the REV size of heterogeneous rocks.

准确确定代表性基本体积（REV）尺寸对分析复杂工程环境中异质岩石的力学性能和破坏过程起着至关重要的作用。本研究结合深度学习和改进的相场法（PFM），提出了一种用于确定 REV 尺寸的新型微结构建模策略（NMMS）。研究系统地进行了微观和宏观实验，以确定具有不同晶粒尺寸的异质岩石的真实微观结构特征和力学性能。在此实验证据的基础上，通过深度学习重建了不同粒度的几何模型，以避免人为方法的局限性，并使用改进的 PFM 进行数值计算。然后利用这些模型在单轴加载条件下进行数值试验，并引入变异系数来确定不同粒度的异质岩石的 REV 尺寸。研究结果表明，最终的 REV 尺寸是在可接受的变异系数范围内，由评价特性定义的 REV 的最大值。在变异系数为 5%的标准下，细中粒（FMG）、中粒（MG）和粗粒（CG）岩石的 REV 尺寸分别为 60 毫米×60 毫米、70 毫米×70 毫米和 90 毫米×90 毫米。此外，在三轴加载条件下，应用 NMMS 确定的 REV 研究了微结构对宏观力学性能和损伤演化的影响。数值结果表明，NMMS 可以准确预测异质岩石的宏观力学性能和微裂纹形态，尤其是长石的晶内裂纹、砾石的界面裂纹和生物岩的 "空洞 "裂纹。这项研究可为异质岩 REV 尺寸的最佳选择提供一些基本参考。

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引用次数: 0

The hydromechanical coupled numerical method in pseudo-3D axisymmetric domain with cracks extension and coalescence applies to the decompression failure problem 伪三维轴对称域中的水力机械耦合数值方法（含裂缝扩展和凝聚）适用于减压失效问题

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-24 DOI: 10.1016/j.ijrmms.2024.105945

The stress-strain state of the saturated porous media determines the behavior of fracturing, which defines the efficiency of developing tight oil, shale, coalbed, and thermal energy fields. Therefore, reliable hydromechanical coupled simulations with destruction reconstruction are critical.

The proposed innovative simulator has a strong interrelation between fluid flow and rock deformation of porous media and realizes a fully coupled pseudo-transient numerical method by high-performance computing (HPC) tools. To increase the detail of the results in the problem, a finite difference numerical algorithm was implemented in the axisymmetric cylindrical domain, which reduces from three to two dimensions without loss of precision. Highly efficient parallelization using CUDA on the GPU computes meshes of up to one billion cells, allowing the simulation of a total core sample to sub-micrometer resolution in an appropriate time. The algorithm has been validated to find the exact solution to the cylinder problem. The proposed model accounts for cracks propagation with their coalescence within a single computational static grid, which keeps timing close to the continuous model.

This comprehensive implementation enables solving industrial problems, such as modeling core sample damage during rapid decompression. High-resolution simulations help reconstruct fracture propagation, analyze the initial stress state, and identify critical damage factors. The comparison with the exact solution to the cylinder problem confirmed the reliability of the algorithm. The calculation results show a strong dependence of decompression failure on the coalescence and elongation of cracks, influenced significantly by the rock's cohesion. Microcracks length and distribution play a decisive role in the decompressive destruction behavior of the rock sample. For the first time, the simulations demonstrated the decompressive destruction of a core sample during an uncontrolled, rapid core retrieval operation.

饱和多孔介质的应力应变状态决定了压裂行为，而压裂行为决定了致密油、页岩、煤层和热能领域的开发效率。所提出的创新模拟器在多孔介质的流体流动和岩石变形之间具有很强的关联性，并通过高性能计算（HPC）工具实现了完全耦合的伪瞬态数值方法。为了增加问题结果的细节，在轴对称圆柱域中实施了有限差分数值算法，在不损失精度的情况下从三维减少到二维。利用 GPU 上的 CUDA 进行高效并行化，可计算多达 10 亿个单元的网格，从而能够在适当的时间内模拟亚微米分辨率的总核心样本。经过验证，该算法可以找到圆柱体问题的精确解。所提出的模型在单个计算静态网格内考虑了裂纹的传播和凝聚，使时间与连续模型接近。这种全面的实施方法可以解决工业问题，如模拟快速减压过程中的岩心样品损伤。高分辨率模拟有助于重建断裂扩展、分析初始应力状态和识别关键损伤因素。通过与圆柱体问题的精确解进行比较，证实了该算法的可靠性。计算结果显示，减压破坏与裂缝的凝聚和伸长有很大关系，受岩石内聚力的影响很大。微裂缝的长度和分布对岩样的减压破坏行为起着决定性作用。模拟首次证明了岩心样本在不受控制的快速岩心取回过程中的减压破坏。

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引用次数: 0

A novel Tree-augmented Bayesian network for predicting rock weathering degree using incomplete dataset 利用不完整数据集预测岩石风化程度的新型树增强贝叶斯网络

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-21 DOI: 10.1016/j.ijrmms.2024.105933

The precise forecasting of the weathering degree of surrounding rock holds paramount importance for the scientific design and secure execution of tunnel engineering. The apparent features of the surrounding rock serve as critical indicators for evaluating its weathering degree. This paper endeavors to quantify the rock apparent features based on an improved Computer vision model and establish a multi-source heterogeneous dataset encompassing 10 parameters, thereby facilitating data-driven predictions of the weathering degree. Specifically, the rock appearance parameters are quantified and segmented by an improved Tunnel face feature segmentation (TFF_Seg) model, which is tailored to the unique characteristics of groundwater, fractures, and interlayers. Concurrently, the TFF_Seg model exhibits significantly enhanced performance for these rock features compared to other widely employed Computer vision methods. Subsequently, this multi-source dataset is further enriched by incorporating rock physical and mechanical parameters as well as tunnel design parameters. Nevertheless, the issue of data incompleteness persists within this dataset. To achieve precise prediction of the weathering degree based on this incomplete dataset, a novel Tree-augmented Bayesian network (TAN-BN) is designed, which is capable of learning from incomplete datasets. The predictive outcomes demonstrate that the proposed TAN-BN surpasses other currently utilized meta models and ensemble models, such as ANN, GBRT, and Naive BN. Finally, sensitivity analysis is conducted to determine the importance rankings of the 10 parameters, offering valuable insights for on-site evaluation of the rock weathering degree at the tunnel face.

围岩风化程度的精确预测对于隧道工程的科学设计和安全实施至关重要。围岩的表观特征是评价围岩风化程度的关键指标。本文试图基于改进的计算机视觉模型对岩石表观特征进行量化，并建立一个包含 10 个参数的多源异构数据集，从而为数据驱动的风化程度预测提供便利。具体来说，通过改进的隧道面特征分割（TFFSeg）模型对岩石外观参数进行量化和分割，该模型专门针对地下水、裂缝和夹层的独特特征而设计。同时，与其他广泛使用的计算机视觉方法相比，TFFSeg 模型在处理这些岩石特征方面的性能明显提高。随后，通过加入岩石物理和机械参数以及隧道设计参数，进一步丰富了这一多源数据集。然而，该数据集仍存在数据不完整的问题。为了在不完整数据集的基础上实现对风化程度的精确预测，设计了一种新型树增强贝叶斯网络（TAN-BN），它能够从不完整的数据集中学习。预测结果表明，所提出的 TAN-BN 超越了目前使用的其他元模型和集合模型，如 ANN、GBRT 和 Naive BN。最后，通过敏感性分析确定了 10 个参数的重要性排序，为现场评估隧道工作面岩石风化程度提供了有价值的见解。

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引用次数: 0

Shear creep deformation of rock fracture distrubed by dynamic loading 动态载荷作用下岩石断裂的剪切蠕变变形

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-21 DOI: 10.1016/j.ijrmms.2024.105943

The long-term stability of jointed rock masses is usually dominated by fault activation, which may be triggered by the dynamic disturbance generated by blasting during mining activities, leading to the occurrence of disasters such as landslides in open-pit and rockbursts in deep mining. The initial stress and dynamic disturbance are key factors that strongly affect the shear creep behavior of rock fractures. In this work, the shear failure instability of rock fractures of sandstone under creep-impact loading was experimentally investigated by using a creep-impact test machine, which allows for applying creep loading and an additional dynamic disturbance on rock fractures. Three stages of shear creep deformation, creep strain rate, and time-to-failure are examined under different creep stress levels and impact energies. Experimental results show that the tangential and normal creep rates increase with the increase of creep stress and impact energy, but the increment of tangential creep rate is higher than that of the normal creep rate. The time-to-failure of the creeping specimen is shortened under high creep stress and large impact energy, while the time-to-failure after the last dynamic disturbance of the specimen is determined by the total impact energy and creep stress level. By using high-speed photography, it is found that the failure types of rock depend on the magnitude of impact energy and creep stress level; that is, rock mainly slides with low stress levels and shears off with high stress levels. In addition, under different impact energy and creep stress levels, the variation of height is between 0.38 and 0.52, while the defined fracture factor, which describes the degree of failure of serrations, is between 0.30 and 0.54. The findings can provide deep insight into the fault sliding mechanism caused by mining activities, which provides theoretical support for the safe mining of ore in fault fracture zones.

节理岩体的长期稳定性通常受断层活化的影响，采矿活动中爆破产生的动态扰动可能引发断层活化，从而导致露天开采中的山体滑坡和深部采矿中的岩爆等灾害的发生。初始应力和动态扰动是强烈影响岩石裂缝剪切蠕变行为的关键因素。本研究利用蠕变冲击试验机对砂岩岩石裂缝在蠕变冲击荷载作用下的剪切破坏不稳定性进行了实验研究，该试验机可对岩石裂缝施加蠕变荷载和额外的动态扰动。在不同的蠕变应力水平和冲击能量下，对剪切蠕变变形、蠕变应变率和破坏时间三个阶段进行了研究。实验结果表明，切向蠕变率和法向蠕变率随着蠕变应力和冲击能量的增加而增加，但切向蠕变率的增量高于法向蠕变率的增量。在高蠕变应力和大冲击能量条件下，蠕变试样的失效时间缩短，而试样最后一次动态扰动后的失效时间由总冲击能量和蠕变应力水平决定。通过高速摄影发现，岩石的破坏类型取决于冲击能量和蠕变应力水平的大小，即岩石主要在低应力水平下滑动，在高应力水平下剪切。此外，在不同的冲击能量和蠕变应力水平下，高度变化介于 0.38 和 0.52 之间，而描述锯齿破坏程度的定义断裂系数介于 0.30 和 0.54 之间。研究结果可以深入揭示采矿活动引起的断层滑动机理，为在断层破碎带安全开采矿石提供理论支持。

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引用次数: 0

A hybrid multiscale model for fluid flow in fractured rocks using homogenization method with discrete fracture networks 利用离散断裂网络的均质化方法建立断裂岩石中流体流动的混合多尺度模型

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-18 DOI: 10.1016/j.ijrmms.2024.105936

Fluid flow in subsurface tight reservoirs containing pores, microcracks and macrocracks is notably influenced by the characteristics of macro/micro-cracks. A novel hybrid multiscale model is proposed to address the response of macrocracks and pores/microcracks in different spatial scales. Specifically, an equivalent macroscopic model (EMM) deduced from locally periodic representative element volume (REV) is developed using the asymptotic homogenization method to represent the poroelastic behavior of porous medium with microcracks. Simultaneously, the macrocracks are modeled explicitly using the discrete fracture model (DFM), where the hydraulic properties of cracks influenced by fluid pressure gradient is represented by the nonlinear opening/closure behavior. The obtained hybrid model takes into account the heterogeneous nature of fractured rock masses containing pores, micro/macro-cracks, which is fundamental to describe fluid flow behavior in fracture-matrix system. Specialized finite elements, regular meshing technique and adaptive time stepping algorithm are adopted to improve the computational efficiency. The hybrid multiscale model is firstly validated step by step to demonstrate the accuracy and then used to simulate fluid flow in fractured rock reservoir, shedding light on the underlying mechanisms of the enhanced flow capacity resulting from microcrack distribution, connectivity, and macrocrack stimulation.

在含有孔隙、微裂缝和大裂缝的地下致密储层中，流体流动明显受到宏观/微观裂缝特征的影响。本文提出了一种新型多尺度混合模型，以解决宏观裂缝和孔隙/微裂缝在不同空间尺度上的响应问题。具体来说，利用渐近均质化方法，从局部周期性代表元素体积（REV）推导出等效宏观模型（EMM），以表示具有微裂缝的多孔介质的孔弹性行为。同时，利用离散断裂模型（DFM）对大裂缝进行了明确建模，其中裂缝受流体压力梯度影响的水力特性由非线性开/闭行为表现。所获得的混合模型考虑了包含孔隙、微/宏观裂缝的断裂岩体的异质性，这对于描述断裂-基质系统中的流体流动行为至关重要。为提高计算效率，采用了专用有限元、规则网格划分技术和自适应时间步进算法。首先逐步验证了混合多尺度模型的准确性，然后利用该模型模拟了裂缝岩石储层中的流体流动，揭示了微裂缝分布、连通性和大裂缝刺激导致流动能力增强的内在机制。

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引用次数: 0

The failure of edge-cracked hard roof in underground mining: An analytical study 地下采矿中边缘开裂硬顶的破坏：分析研究

IF 7 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

International Journal of Rock Mechanics and Mining Sciences

Pub Date : 2024-10-18 DOI: 10.1016/j.ijrmms.2024.105934

Hard roof is the primary concern of strata control in underground mining. Various techniques have been utilized to fracture the hard roof and control the failure of strata. Understanding the impact of cracks on strata behaviour is vital for optimizing strata control strategies. In this study, the hard roof was regarded as a beam structure with different loading, support, and boundary conditions. The equivalent spring model was adopted to represent the edge-cracked section of the hard roof, which allows additional rotation at the crack location. A piecewise-defined function was developed for solving equations of hard roof in the vicinity of the crack section. By combining the hard roof beam model and the equivalent spring model, the impact of a crack on the hard roof can be measured. A case study was carried out to explore the impacts of crack location and crack depth on the mechanical state of the hard roof. Results showcase the failure of the hard roof controlled by the crack depth and greatly influenced by the crack location. From the perspective of coal burst prevention, roof fracturing should be implemented at the high-stress area of strata, whereas it has been challenging in practice to determine such a location precisely. To address this challenge, it was suggested that hard roof fracturing should be carried out before coal seam de-stressing, increasing the likelihood of a crack occurring in a high-stress area. By adopting the proposed method, the mechanical state of the edge-cracked hard roof can be quantified.

硬顶是地下采矿中地层控制的首要问题。人们利用各种技术对硬顶板进行破碎，控制地层的破坏。了解裂缝对地层行为的影响对于优化地层控制策略至关重要。在本研究中，硬顶板被视为具有不同荷载、支撑和边界条件的梁结构。采用等效弹簧模型表示硬屋顶的边缘裂缝部分，允许裂缝位置有额外的旋转。开发了一个片断定义的函数，用于求解裂缝部分附近的硬屋顶方程。通过结合硬屋顶梁模型和等效弹簧模型，可以测量裂缝对硬屋顶的影响。通过案例研究，探讨了裂缝位置和裂缝深度对硬屋顶力学状态的影响。结果表明，硬顶板的破坏受裂缝深度的控制，并在很大程度上受裂缝位置的影响。从防止煤层爆裂的角度来看，顶板破碎应在地层的高应力区进行，而在实践中，要精确地确定这样的位置一直是个难题。为解决这一难题，有人建议在煤层去应力之前进行硬顶压裂，以增加裂缝出现在高应力区的可能性。通过采用建议的方法，可以量化边缘裂缝硬顶的机械状态。

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引用次数: 0