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Anisotropic behavior and mechanical characteristics of the Montney Formation 蒙特尼地层的各向异性行为和力学特征
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-01 DOI: 10.1016/j.ijrmms.2024.105831

This study investigates the rock mechanics and anisotropic properties of the Montney Formation, Alberta, through two sets of experiments: unconfined compressive strength tests and triaxial compression tests, supplemented by ultrasonic wave velocity measurements. These tests enabled the calculation of dynamic and static stiffness properties and Thomsen anisotropy parameters (ε, δ, γ). Our findings reveal that the Montney Formation exhibits weak anisotropy, with ε values generally below 0.10, contrasting with other strongly anisotropic shale formations. Specimens exhibiting higher clay content and total organic carbon levels show more pronounced anisotropy. Static measurements exhibit a higher degree of anisotropy compared to dynamic measurements. The investigation also explored loading and unloading stiffness parameters, noting a higher E loading-to-unloading ratio for rock specimens with lower elastic properties. This provides important information on the rock's response to stress path effects during stimulation and exploitation. The study also discusses other rock mechanics parameters including Poisson's ratio, tensile strength, and brittleness. The research contributes to a more comprehensive understanding of the geomechanical and petrophysical behavior of the Montney Formation, aiding reservoir characterization and hydrocarbon exploration and production.

本研究通过两组实验研究了阿尔伯塔省蒙特尼地层的岩石力学和各向异性特性:无约束抗压强度试验和三轴压缩试验,并辅以超声波速度测量。通过这些试验,可以计算出动态和静态刚度特性以及汤姆森各向异性参数(ε、δ、γ)。我们的研究结果表明,蒙特尼地层的各向异性较弱,ε值一般低于 0.10,这与其他各向异性较强的页岩层形成了鲜明对比。粘土含量和总有机碳含量较高的样本显示出更明显的各向异性。与动态测量相比,静态测量显示出更高程度的各向异性。调查还探讨了加载和卸载刚度参数,注意到弹性特性较低的岩石试样具有较高的 E 加载-卸载比。这为岩石在激励和开采过程中对应力路径效应的反应提供了重要信息。研究还讨论了其他岩石力学参数,包括泊松比、抗拉强度和脆性。这项研究有助于更全面地了解蒙特尼地层的地质力学和岩石物理行为,有助于储层特征描述以及油气勘探和生产。
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引用次数: 0
Characterization of energy-driven damage mechanism and gas seepage in coal under mining-induced stress conditions 采矿诱发应力条件下煤炭中能量驱动破坏机制和瓦斯渗流的表征
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-07-31 DOI: 10.1016/j.ijrmms.2024.105834

Gas seepage and progressive failure of coal are common energy-driven mining phenomena. A comprehensive understanding of the energy-driving mechanism behind the catastrophic behavior of mining-induced coal is fundamental to innovating the technology of coal and gas co-mining. Thus, this study simulated three typical mining stress evolution process in protective coal-seam mining (PCM), top-coal caving mining (TCM), and non-pillar mining (NM) to investigate the energy evolution and distribution patterns of coal. The results indicate a strong correlation between energy dissipation and gas seepage. By transitioning from PCM and TCM to NM, the peak elastic strain energy of gas-bearing coal increased by 155.92 %, and the ratio of peak dissipative energy decreased from 51 % to 41 %. Under the PCM stress path, gas seepage decreased the energy storage by 13.52 %, whereas the pre-mining pressure relief and enhanced permeability simulation increased in peak dissipation energy by 49.66 %. Using the cumulative dissipative energy as a damage variable reveals that the degree of coal damage evolution under PCM is higher than other mining methods. Based on the energy-driven damage mechanism, a new coal permeability model was established, and its comparison with classical permeability model demonstrated its excellent fitting effectiveness.

瓦斯渗漏和煤的渐进衰竭是常见的能量驱动开采现象。全面了解开采诱发煤炭灾难性行为背后的能量驱动机制,是创新煤与瓦斯共采技术的基础。因此,本研究模拟了保护煤层开采(PCM)、顶煤崩落开采(TCM)和非支柱开采(NM)三种典型的开采应力演化过程,以研究煤炭的能量演化和分布规律。结果表明,能量耗散与瓦斯渗流之间存在密切联系。从 PCM 和 TCM 过渡到 NM,含瓦斯煤的峰值弹性应变能增加了 155.92%,峰值耗散能比率从 51% 降至 41%。在 PCM 应力路径下,瓦斯渗流使储能减少了 13.52%,而开采前降压和强化渗透模拟使峰值耗散能增加了 49.66%。将累积耗散能作为破坏变量可以发现,PCM 下煤炭破坏演化程度高于其他开采方法。基于能量驱动的损伤机理,建立了新的煤炭透气性模型,并与经典透气性模型进行了对比,证明了其卓越的拟合效果。
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引用次数: 0
Reliability analysis of deep tunnels in spatially varying brittle rocks using interval and random field modelling 利用区间和随机场建模对空间变化的脆性岩中的深层隧道进行可靠性分析
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-07-31 DOI: 10.1016/j.ijrmms.2024.105836

Rock properties are estimated using objective lab/in-situ testing and subjective judgements invoking different types of uncertainties, i.e., aleatory, and epistemic, along them, often indicated by varying information levels. This study presents a unified reliability method to integrate the spatial variability of inputs modelled via alternate uncertainty models (intervals and probability-boxes (p-boxes)) with those modelled as stochastic variables via probability distributions. The methodology employs advanced Karhunen–Loève decomposition to generate interval and random fields of inputs modelled via alternate and stochastic models, respectively. Input properties are allocated to the zones of the numerical model in Fast Lagrangian Analysis of Continua-2D (FLAC-2D) based on their spatial dependency and correlation functions through a developed MATLAB-FLAC coupled code. The methodology is demonstrated for a deep tunnel in Canada to be constructed along a massive rock prone to brittle failures. Intact rock properties are modelled as stochastic variables due to objective estimation, while Geological Strength Index (GSI) and deformation modulus are modelled using alternate models (interval and p-box, respectively) due to subjective and hybrid estimation (double uncertainty propagation algorithm). The results of the methodology are compared with those of traditional deterministic and random field methods. The methodology reduces the subjectivity invoked by including unavailable additional information (e.g., assuming probability distributions of inputs based on literature) and propagates the originally available information of inputs accurately. The final outputs are the p-boxes of response parameters (i.e., displacements and damage zone) instead of their fixed values (deterministic analysis) and probability distributions (traditional reliability analysis), indicating the propagation of both impreciseness and variability of inputs by the method. For this case study, the p-boxes of outputs were bounding their values/distributions estimated via traditional analyses, verifying the accuracy of the methodology. Further, the impreciseness in the outputs, highest in the damage zone extent, was due to imprecision in the estimated GSI.

对岩石特性的估算,既有客观的实验室/现场测试,也有主观的判断,其中包含不同类型的不确定性,即已知的和认识的不确定性,这些不确定性通常表现为不同的信息水平。本研究提出了一种统一的可靠性方法,将通过交替不确定性模型(区间和概率框(p-boxes))建模的输入空间变异性与通过概率分布作为随机变量建模的输入空间变异性结合起来。该方法采用先进的 Karhunen-Loève 分解法,分别生成通过交替模型和随机模型建模的输入的区间和随机场。通过开发的 MATLAB-FLAC 耦合代码,根据输入属性的空间依赖性和相关函数,将输入属性分配到快速拉格朗日连续体分析-2D(FLAC-2D)数值模型的区域。该方法针对加拿大的一条深隧道进行了演示,该隧道将沿着易发生脆性破坏的大块岩石建造。由于采用了客观估算,完整岩石属性被模拟为随机变量,而地质强度指数(GSI)和变形模量则由于采用了主观估算和混合估算(双重不确定性传播算法),使用交替模型(分别为区间模型和 p-box 模型)进行模拟。该方法的结果与传统的确定性方法和随机现场方法的结果进行了比较。该方法减少了因加入不可用的附加信息(如根据文献假设输入的概率分布)而产生的主观性,并准确地传播了输入的原始可用信息。最终输出的是响应参数(即位移和破坏区)的 p-框,而不是其固定值(确定性分析)和概率分布(传统可靠性分析),这表明该方法传播了输入的不精确性和可变性。在本案例研究中,通过传统分析估算出的输出值/分布的 p 框与其值/分布的边界一致,验证了该方法的准确性。此外,由于估算的 GSI 不精确,导致输出结果不精确,其中损坏区范围的精确度最高。
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引用次数: 0
Enhancing stability graphs for stope design in deep metal mines using machine learning 利用机器学习增强用于深部金属矿井斜坡设计的稳定性图
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-07-31 DOI: 10.1016/j.ijrmms.2024.105837

Stope structural parameters, which are human-controllable, directly impact the safety and economics performance of underground mineral extraction. Current stope design still relies heavily on empirical methods such as stability graphs, due to the complex nature of rock masses and varied stope failure mechanisms. This study aims to enhance stability graphs with machine learning techniques. Firstly, a dataset of 980 records from unsupported stopes was compiled, representing perhaps the largest dataset of its kind so far in the literature. This was achieved through extensive literature review and the collation of an additional 289 records from Chinese mines which were previously not included. An analysis of data reveals that over 90 % of the records fall within a stability coefficient of 0–100 and a hydraulic radius of 0–20 m. Secondly, a stability graphs optimization process was established using Python, eliminating the subjectivity of partitioning. Nine supervised machine learning algorithms were employed and trained to test their performance in partitioning form and predicting accuracy. It was found that the neural network algorithm demonstrated the best overall performance. At last, a neural network with the Keras framework was used to establish a new multilayer perceptron model to generate safety factor probability curves, which were then used to construct the stability graph. To facilitate practical use, mathematical functions fitting safety factor curves within the unstable zone were further formulated. Compared with other empirical stability graphs, our new approach allows designers to more efficiently and reliably select safety factors to determine the stability state according to site specific conditions and technical support systems, thereby providing enhanced guidance for stope design.

人工可控的斜坡结构参数直接影响地下矿产开采的安全性和经济性。由于岩体的复杂性和不同的斜坡失效机制,目前的斜坡设计仍主要依赖于稳定性图等经验方法。本研究旨在利用机器学习技术增强稳定性图。首先,我们编制了一个包含 980 条无支撑斜坡记录的数据集,这可能是迄今为止文献中最大的同类数据集。这是通过广泛的文献综述和整理额外的 289 条以前未包括在内的中国矿井记录而实现的。数据分析显示,超过 90% 的记录属于 0-100 的稳定系数和 0-20 米的水力半径范围。采用了九种有监督的机器学习算法并对其进行了训练,以测试其在分区形式和预测准确性方面的性能。结果发现,神经网络算法的整体性能最佳。最后,使用 Keras 框架的神经网络建立了一个新的多层感知器模型,以生成安全系数概率曲线,然后用于构建稳定性图。为便于实际使用,还进一步制定了不稳定区域内安全系数曲线拟合数学函数。与其他经验稳定图相比,我们的新方法能让设计人员更有效、更可靠地根据现场具体条件和技术支持系统选择安全系数来确定稳定状态,从而为斜坡设计提供更好的指导。
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引用次数: 0
Crack propagation process and lifetime prediction method of concrete-rock interface under constant loading 恒定荷载下混凝土-岩石界面的裂缝扩展过程和寿命预测方法
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-07-30 DOI: 10.1016/j.ijrmms.2024.105839

This study investigated the crack propagation processes and established the lifetime prediction methods of the concrete-rock interfaces under constant loading. Firstly, the constant loading tests were performed under three-point bending loading on the composite concrete-rock beams with three kinds of interfaces, i.e. natural, 4 × 4, and 7 × 7 interfaces, and under three constant load levels, i.e. initial cracking load, 80 % and 97 % of the peak loads. Then, the clip gauge method and digital image correlation method were employed to detect the crack lengths under constant loading. Finally, the effects of constant load levels on fracture properties of the concrete-rock interfaces were analyzed and the crack propagation processes under constant loading were discussed. The results indicated that the clip gauge method was an available and accurate method to detect the crack lengths of the concrete-rock interfaces under constant loading. Crack propagation processes and crack mouth opening processes under constant loading exhibited the three-stage feature, i.e. deceleration stage, uniform stage and acceleration stage. In addition, the logarithms of the constant loading lifetimes showed an approximate linear relationship with the logarithms of the crack mouth uniform opening rates, and a quantitative relationship was established by using the linear regression analysis to establish the lifetime prediction methods. This study proposed a practical method to predict the service life of concrete structure-bedrock interface. When the crack mouth uniform opening stage was recognized, the lifetime of concrete structure-bedrock interface in service can be predicted by substituting the crack mouth uniform opening rate into the pre-established prediction model. This study can provide the theoretical support for the safety assessment of the concrete structure-bedrock interface in service.

本研究探讨了混凝土-岩石界面在恒定荷载作用下的裂纹扩展过程,并建立了寿命预测方法。首先,在三种界面(即自然界面、4 × 4 界面和 7 × 7 界面)的混凝土-岩石复合梁上,在三种恒定荷载水平(即初始开裂荷载、峰值荷载的 80 % 和 97 %)下进行了三点弯曲恒载试验。然后,采用夹钳法和数字图像相关法检测恒定荷载下的裂缝长度。最后,分析了恒定荷载水平对混凝土-岩石界面断裂特性的影响,并讨论了恒定荷载下的裂缝扩展过程。结果表明,夹规法是检测恒定荷载下混凝土-岩石界面裂缝长度的一种可用且准确的方法。恒定荷载下的裂缝扩展过程和裂缝张口过程呈现三阶段特征,即减速阶段、均匀阶段和加速阶段。此外,恒定加载寿命的对数与裂口均匀张开率的对数呈近似线性关系,并通过线性回归分析建立了定量关系,从而确立了寿命预测方法。本研究提出了一种实用的混凝土结构-岩石界面使用寿命预测方法。当裂缝口均匀张开阶段得到确认后,将裂缝口均匀张开率代入预先建立的预测模型,即可预测混凝土结构-岩土界面的服役寿命。该研究可为混凝土结构-基岩界面的使用安全评估提供理论支持。
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引用次数: 0
Propagation of interfered hydraulic fractures by alternated radial-circumferential extensions and its impact on proppant distribution 通过径向-环向交替延伸传播干扰水力压裂及其对支撑剂分布的影响
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-07-30 DOI: 10.1016/j.ijrmms.2024.105838

The fracture extension mechanisms and proppant transport characteristics play key roles for optimizing hydraulic fracturing in unconventional reservoirs. In this work, the visual physical simulation method was used to analyze the 3D dynamic extension processes of multi-stage hydraulic fractures and the subsequent impact on proppant distribution. The interfered fracture in multi-stage hydraulic fracturing exhibit alternated radial-circumferential extension behavior. More specifically, these behavior changes from unilaterally radial initiation, circumferential extension to radial extension. Unilaterally radial initiation results in the formation of both mirror and conchoidal features, while circumferential extension leads to stepped feature, and radial extension gives rise to feather feature. The four features of hydraulic fractures result in four types of non-uniform proppant distribution: uniform, scattered, cluster, and regional distribution. The proppant transport shifted from linear to radial mode, promoting further fracture extension. The effects of segment spacing and proppant injection sequence were studied. The results showed that the influence on the interfered fracture decreases as the segment spacing increases. In addition, the propped fracture area is larger when the small-size proppant is injected first, followed by large-size one. The research can improve understanding and optimization of multi-stage hydraulic fracturing in unconventional oil and gas reservoirs.

压裂延伸机理和支撑剂输送特性对于优化非常规储层的水力压裂起着关键作用。本研究采用可视化物理模拟方法分析了多级水力压裂的三维动态延伸过程及其对支撑剂分布的影响。多级水力压裂中的干扰裂缝表现出径向-环向交替延伸行为。更具体地说,这些行为从单侧径向启动、周向延伸到径向延伸。单侧径向启动会形成镜面特征和锥形特征,而环向延伸会形成阶梯特征,径向延伸会形成羽毛特征。水力裂缝的四种特征导致了四种非均匀支撑剂分布:均匀分布、分散分布、集束分布和区域分布。支撑剂的输送从线性模式转变为径向模式,促进了裂缝的进一步延伸。研究了段间距和支撑剂注入顺序的影响。结果表明,随着分段间距的增大,对干扰断裂的影响减小。此外,先注入小尺寸支撑剂,后注入大尺寸支撑剂时,支撑裂缝面积更大。该研究可提高对非常规油气藏多级水力压裂的理解和优化。
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引用次数: 0
Distribution-free estimation for average trace length of rock discontinuities within 3D large sampling window of complex high-steep slope 复杂高陡边坡三维大采样窗内岩石不连续性平均轨迹长度的无分布估计
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-07-13 DOI: 10.1016/j.ijrmms.2024.105828
Sicong Wang , Shengyuan Song , Baotian Li , Mingyu Zhao , Yongchao Li , Dianze Liu

The trace length as an important indicator reflecting the size of discontinuity, can usually be estimated by setting a sampling window on the surface of the rock mass. However, in high-steep rock slopes with cliffy topography and uneven terrain, traditional methods are difficult to select suitable plane sampling windows. Therefore, estimating the average trace length accurately in this situation has become an urgent problem to be solved. This study proposes a distribution-free method for estimating the average trace length of discontinuities within large windows in complex high-steep slopes. By introducing a cuboid sampling window, the estimation method has been extended to three-dimensional for the first time. Additionally, the proposed method addresses the limitations of existing methods, making it applicable for larger sampling areas. In addition, the new method considers the proportion of three types of traces intersecting the sampling area and their angles with the sampling area, and corrects the new method using the weight of visible traces at both ends, eliminating the impact of sampling biases such as censoring bias, orientation bias, and size bias. The reliability of the proposed method was validated by generating nine sets of simulated trace data with different angles and distribution types. Finally, the new method is applied to a complex high-steep slope with an elevation difference of nearly 600 m on the southeastern edge of the Qinghai Tibet Plateau. The results indicate that for the estimation of trace length in high-steep slope, the new method has smaller errors and lower error volatility. When selecting an appropriate sampling area size, the error of the new method is less than 6 %, and the error fluctuation is less than 4 %. And this study is of great significance for evaluating the stability of high-steep rock mass structures in major projects in hard mountain areas.

迹线长度是反映不连续性大小的重要指标,通常可以通过在岩体表面设置取样窗口来估算。然而,在地形陡峭、高低不平的高陡岩坡上,传统方法很难选择合适的平面取样窗。因此,在这种情况下准确估算平均轨迹长度成为亟待解决的问题。本研究提出了一种无分布方法,用于估算复杂高陡边坡大窗口内不连续面的平均轨迹长度。通过引入长方体采样窗口,该估算方法首次扩展到三维领域。此外,所提出的方法还解决了现有方法的局限性,使其适用于更大的采样区域。此外,新方法还考虑了与采样区域相交的三种痕迹的比例及其与采样区域的夹角,并利用两端可见痕迹的权重对新方法进行修正,消除了剔除偏差、方向偏差和大小偏差等采样偏差的影响。通过生成九组不同角度和分布类型的模拟轨迹数据,验证了所提方法的可靠性。最后,将新方法应用于青藏高原东南边缘高差近 600 米的复杂高陡边坡。结果表明,对于高陡边坡的迹线长度估算,新方法的误差较小,误差波动也较小。在选择合适的采样面积时,新方法的误差小于 6%,误差波动小于 4%。这项研究对硬质山区重大工程中高陡岩体结构的稳定性评价具有重要意义。
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引用次数: 0
Mechanical behavior and thermal damage characterization of granite after flame jet-water cooling treatment 火焰喷射-水冷却处理后花岗岩的力学行为和热损伤表征
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-07-11 DOI: 10.1016/j.ijrmms.2024.105833
Xibing Li, Yangchun Wu, Linqi Huang

Flame jet-assisted mechanical rock drilling is expected to solve the hard-rock crushing challenges in underground engineering such as mining, tunneling, and drilling. Therefore, it is important to investigate mechanical behavior of the rock after flame jet-water cooling treatment. In this paper, granite blocks were subjected to flame jet-water cooling treatment, which means the rapid heating of the granite using a flame with a temperature of 1564 °C, followed by water cooling. Then, physico-mechanical behaviors of samples at different distances (all the distances mentioned later mean the vertical distance between the sample axis and the flame jet-water cooling path) were measured. Results showed physico-mechanical parameters of the sample increased as the distance increased. The Vp (P-wave velocity), UCS (uniaxial compressive strength) and BTS (Brazilian tensile strength) of the samples increased from 3171.7 m/s, 84.84 MPa and 5.01 MPa at 0 mm to 3619.3 m/s, 145.86 MPa and 7.30 MPa at 70 mm, respectively. Meanwhile, physico-mechanical parameters of samples at 70 mm all reached more than 95 % of those of untreated samples. As the distance increased, cumulative AE counts at peak stress gradually enhanced, and failure modes of uniaxial samples shifted from shear to tensile splitting failure. The SEM (scanning electron microscope) images illustrated that the closer to the flame jet-water cooling path, the more thermal cracks produced in the sample. Meanwhile, the damage factor can well characterize the thermal damage degree of granite. According to the variation of physico-mechanical parameters and SEM images of samples with distances, it can be assumed that the thermal damage width of granite after flame jet-water cooling was about 140 mm. It was much greater than the 50 mm width of spalling pits, which greatly increased the feasibility of thermal-assisted mechanical rock drilling. The tensile stress induced by the temperature gradient below the spalling pit is the fundamental cause of thermal damage to the rock, which is further aggravated by water cooling. The findings can provide some guidance for flame jet-assisted mechanical rock drilling.

火焰喷射辅助机械凿岩有望解决采矿、隧道和钻探等地下工程中的硬岩破碎难题。因此,研究火焰喷射水冷却处理后岩石的力学行为非常重要。本文对花岗岩块进行了火焰喷射-水冷却处理,即使用温度为 1564 ℃ 的火焰快速加热花岗岩,然后进行水冷却。然后,测量了样品在不同距离(后面提到的所有距离均指样品轴线与火焰喷射-水冷却路径之间的垂直距离)上的物理机械性能。结果表明,样品的物理机械参数随着距离的增加而增加。样品的 V(P 波速度)、UCS(单轴抗压强度)和 BTS(巴西抗拉强度)分别从 0 mm 时的 3171.7 m/s、84.84 MPa 和 5.01 MPa 增加到 70 mm 时的 3619.3 m/s、145.86 MPa 和 7.30 MPa。同时,70 毫米处样品的物理机械参数均达到未处理样品的 95% 以上。随着距离的增加,峰值应力下的累积 AE 计数逐渐增加,单轴样品的失效模式从剪切失效转变为拉伸劈裂失效。扫描电子显微镜(SEM)图像显示,越靠近火焰喷射-水冷却路径,样品产生的热裂纹越多。同时,损伤因子可以很好地表征花岗岩的热损伤程度。根据样品物理力学参数和扫描电镜图像随距离的变化,可以推测火焰喷水冷却后花岗岩的热损伤宽度约为 140 毫米。这远远大于 50 毫米的剥落坑宽度,大大提高了热辅助机械凿岩的可行性。剥落坑下方的温度梯度引起的拉应力是岩石热损伤的根本原因,而水冷则进一步加剧了这种损伤。研究结果可为火焰喷射辅助机械凿岩提供一些指导。
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引用次数: 0
Energy control and block performance optimization of bench blasting 台阶爆破的能量控制和区块性能优化
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-07-11 DOI: 10.1016/j.ijrmms.2024.105830
Ming Tao , Yuanquan Xu , Rui Zhao , Yulong Liu , Chengqing Wu

In this study, rock-like model blast tests with varying toe burdens are conducted and the evolution of blast-induced fractures is analyzed using the digital image correlation (DIC) method. In addition, post-blast fragmentations are image-processed to quantitatively investigate the blasting performance. A three-dimensional numerical model is developed and validated against the experimental results. The effects of blasthole inclination (70°, 80°, and 90°) and short delays on fragment size distribution (FSD) are numerically investigated. Field trials are conducted to verify the numerical results. The experimental results reveal that the overall fragment size increases significantly in proportion to the toe burden. The explosion energy utilization rates range from 3.56 % to 13.16 %, with a tendency to initially increase and subsequently decrease. The numerical results demonstrate that fragments are more evenly distributed with a blasthole inclination of 70°, resulting in a remarkable improvement in rock fragmentation compared to a vertical blasthole. Compared to the toe burden, the influence of short delays on concrete fragmentation is insignificant. The field test results indicate that a narrower FSD range and stable pit walls are achieved by utilizing inclined blastholes in bench blasting. This study provides theoretical guidance for optimizing bench blasting parameters, which has practical significance for improving explosive energy utilization and production efficiency in open-pit mines.

本研究采用数字图像相关(DIC)方法,对不同趾部负担的类岩模型爆破试验进行了研究,并分析了爆破引起的裂缝演变。此外,还对爆破后的碎片进行了图像处理,以定量研究爆破性能。建立了一个三维数值模型,并根据实验结果进行了验证。数值研究了爆破孔倾角(70°、80° 和 90°)和短延迟对碎片尺寸分布(FSD)的影响。为验证数值结果,还进行了现场试验。实验结果表明,碎片的总体尺寸随着趾部负担的增加而显著增大。爆炸能量利用率从 3.56 % 到 13.16 % 不等,呈先增后减的趋势。数值结果表明,与垂直爆破相比,当爆破孔倾角为 70°时,碎片分布更均匀,岩石破碎率显著提高。与趾部负担相比,短时延迟对混凝土破碎的影响微乎其微。现场测试结果表明,在台阶爆破中利用倾斜爆破孔可以获得更窄的 FSD 范围和稳定的坑壁。该研究为优化台车爆破参数提供了理论指导,对提高露天矿爆破能量利用率和生产效率具有重要的现实意义。
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引用次数: 0
Proposed formulas for pillar stress estimation in a regular room-and-pillar pattern 用于估算规则房柱模式中支柱应力的拟议公式
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-07-10 DOI: 10.1016/j.ijrmms.2024.105826
Ioannis Vlachogiannis , Andreas Benardos

Room-and-pillar mining is one of the oldest and most widely employed underground mining methods worldwide, while in recent years it has also been used for civil engineering projects and applications. The pillar design process is quite straightforward, requiring the assessment of two key elements, namely the pillar's strength and the anticipated loading imposed on it. Lots of research work has been elaborated for the estimation of pillars' strength and the main parameters associated with it, while, on the other hand, in terms of the loading the Tributary Area Theory (TAT) has been traditionally and successfully used as the dominant methodology to assess the post-mining pillar induced stresses. This paper focuses primarily on decoding the pillar loading regime by analyzing the identifying the stresses imposed to them through the use of modern computational tools offered by 2D and 3D numerical analyses, over a series of pillars' type (square, ribs), configurations and initial virgin stress fields. This allows for the development of a benchmarking framework that showcase the differences in the stress conditions and reveal the over-conservative behavior of TAT. More importantly though, it allowed for the expression of two (2) general analytical formulae for the direct estimation of the average vertical elastic stresses on pillars, both for the case of rib & square pillars layout; the most typical patterns applied in this method. They aim at providing an easy to use and more accurate estimation of the pillar stress - as compared to TAT - in alignment with the results obtained from numerical analyses. Thus, with the proposed formulas, the time-consuming numerical process needed for preliminary pillars' dimensioning is tackled in a swift and effective manner.

房柱式采矿是世界上历史最悠久、应用最广泛的地下采矿方法之一,近年来也被用于土木工程项目和应用领域。支柱设计过程非常简单,需要评估两个关键因素,即支柱的强度和对其施加的预期负荷。为估算支柱强度及其相关的主要参数,已经开展了大量的研究工作,而另一方面,在加载方面,支流面积理论(TAT)作为评估采矿后支柱诱导应力的主要方法,一直被成功地使用。本文的主要重点是通过使用二维和三维数值分析提供的现代计算工具,对一系列支柱类型(方形、肋形)、配置和初始原始应力场进行分析,确定施加在支柱上的应力,从而解码支柱加载机制。这样就可以建立一个基准框架,显示应力条件的差异,并揭示 TAT 的过度保守行为。但更重要的是,它允许表达两(2)个用于直接估算支柱上平均垂直弹性应力的通用分析公式,这两个公式都适用于肋和方形支柱布局的情况;这是本方法中应用的最典型模式。与 TAT 相比,这些公式旨在提供一种易于使用且更准确的支柱应力估算方法,与数值分析得出的结果保持一致。因此,利用所提出的公式,可以快速有效地解决初步确定支柱尺寸所需的耗时的数值计算过程。
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引用次数: 0
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International Journal of Rock Mechanics and Mining Sciences
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