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The length of fracture process zone deciphers variations of rock tensile strength 断裂过程区的长度解读岩石抗拉强度的变化
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-27 DOI: 10.1016/j.ijrmms.2024.105885
Saeed Aligholi , A.R. Torabi , Mehdi Serati , Hossein Masoumi

Tensile strength is one of the most critical design factors in many rock engineering projects. However, despite many available testing techniques, an accurate estimation of the true tensile strength of quasi-brittle rock-like materials is yet a controversial problem since it can vary by the shape and size of a test specimen, the adopted test method, and applied loading conditions. Different studies have tried to address this issue by providing (mainly empirical) laws for determining variations of rock tensile strength as a function of a particular test parameter such as specimen size. In this study, however, a new general approach is presented that can decipher the tensile strength variations of rock under various testing conditions. Using coupled Finite Fracture Mechanics (FFM), it is first proved that the length of the Fracture Process Zone (FPZ) can be determined with accuracy and ease using the energy criterion of coupled FFM. Then, the length of FPZ is used in the stress criterion of coupled FFM to determine rock tensile strength. The failure stress of a material is then proved to be mainly a function of the FPZ length following a power law originated from the Linear Elastic Fracture Mechanics (LEFM). The results assist in deciphering variations of rock tensile strength related to the sample size and test method.

抗拉强度是许多岩石工程项目中最关键的设计因素之一。然而,尽管有许多可用的测试技术,但准确估算准脆性类岩石材料的真实抗拉强度仍是一个有争议的问题,因为抗拉强度会因测试样本的形状和尺寸、采用的测试方法以及应用的加载条件而变化。为了解决这个问题,不同的研究都提供了(主要是经验)法则,用于确定岩石抗拉强度随试样尺寸等特定测试参数的变化。然而,本研究提出了一种新的通用方法,可以破解岩石在各种测试条件下的抗拉强度变化。利用耦合有限断裂力学(FFM),首先证明了利用耦合有限断裂力学的能量准则可以准确、轻松地确定断裂过程区(FPZ)的长度。然后,在耦合 FFM 的应力准则中使用 FPZ 长度来确定岩石抗拉强度。材料的破坏应力被证明主要是 FPZ 长度的函数,遵循线性弹性断裂力学(LEFM)的幂律。这些结果有助于解读与样本大小和测试方法有关的岩石抗拉强度变化。
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引用次数: 0
Experimental investigation on the influence of weak interlayers on sandstone rockburst and associated microcracking mechanism 弱夹层对砂岩岩爆的影响及相关微裂缝机制的实验研究
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-27 DOI: 10.1016/j.ijrmms.2024.105890
Fuqiang Ren , Tengyuan Song , Ke Ma , Murat Karakus

Weak interlayers (WI) are common in sedimentary rock masses in deep coal mines. The qualitative effect of the WI on rockbursts is widely acknowledged; however, its influence mechanism still needs further investigation. In the present study, true triaxial unloading rockburst tests of sandstone with WI and calcite veins (CV) were conducted to explore their influence mechanisms. To explore the impact of WI, the rockburst stress, failure modes, acoustic emission (AE) parameters (energy, entropy, and b-value), and spatial energy characteristics of AE events were analyzed. The influence of the area ratio of WI and their distribution patterns (centralization and dispersion) on rockburst were further investigated. The results indicate that the rockburst stress (peak of maximum principal stress) decreased by 4 % for every 1 % increase in the sandstone's dispersion WI area ratio (1.9%–9.3 %). Namely, rockburst is more likely to occur when there is appropriate WI distributed in the sandstone because WI exacerbates the microcrack activities and energy release. The CV will reduce the weakening effect of WI on rockburst stress and can enhance the rockburst intensity, especially in samples with dispersion WI. Moreover, the more considerable AE energy is released around CV for the sandstone with dispersion WI. The interface between WI and matrix is prone to rockburst for the sandstone with centralized WI because of the concentrated energy release. The results of this paper can provide a reference for the prevention and control of rockbursts in mine sedimentary rocks containing WI and CV.

弱夹层(WI)在深部煤矿的沉积岩体中很常见。WI 对岩爆的定性影响已得到广泛认可,但其影响机制仍有待进一步研究。本研究对含 WI 和方解石脉(CV)的砂岩进行了真正的三轴卸载岩爆试验,以探讨其影响机制。为探讨 WI 的影响,分析了岩爆应力、破坏模式、声发射(AE)参数(能量、熵和 b 值)以及 AE 事件的空间能量特征。进一步研究了 WI 的面积比及其分布模式(集中和分散)对岩爆的影响。结果表明,砂岩的分散 WI 面积比(1.9%-9.3%)每增加 1%,岩爆应力(最大主应力峰值)就减少 4%。也就是说,当砂岩中分布有适当的 WI 时,岩爆更容易发生,因为 WI 会加剧微裂缝活动和能量释放。CV 会降低 WI 对岩爆应力的削弱作用,并能增强岩爆强度,尤其是在 WI 分散的样本中。此外,对于具有分散 WI 的砂岩来说,CV 周围释放的 AE 能量更大。对于集中式 WI 的砂岩,WI 与基体之间的界面由于能量释放集中而容易发生岩爆。本文的研究结果可为含有 WI 和 CV 的矿山沉积岩岩爆的防治提供参考。
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引用次数: 0
Analytical solutions of noncircular tunnels in transversely isotropic rheological rock masses 横向各向同性流变岩体中的非圆形隧道的解析解
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-26 DOI: 10.1016/j.ijrmms.2024.105880
G.S. Zeng , H.N. Wang , F. Song , A. Rodriguez-Dono , L.R. Alejano

In the field of tunnelling applications, it is often found that the rock masses exhibit anisotropy and rheological properties. To optimize the utilization of underground space, the use of noncircular tunnels is often preferred. However, it is important to note that these noncircular tunnels can lead to high-stress concentrations and significant displacements.

This article presents a thorough analytical study on the time-dependent ground responses induced by the excavation of noncircular tunnels in transversely isotropic viscoelastic rock masses. The study considers a comprehensive set of engineering factors, including the viscoelastic characteristics of the surrounding rock, any anisotropic angle, and arbitrary tunnel shapes.

Using the generalized corresponding principle of anisotropic elasticity and anisotropic viscoelasticity, an analytical model is introduced. This model can accurately and swiftly address the problem of deformation and stresses around noncircular tunnels in anisotropic rheological rock masses. The analytical solutions are verified by their good agreement with the Finite Element Method (FEM) results under identical assumptions. Moreover, the qualitative agreement between the analytical solutions and field data further validates the practical application of the analytical solution.

A parametric analysis is then performed to investigate the effects of anisotropy ratio, anisotropy angle, and coefficient of lateral pressure on stresses and displacements.

The proposed analytical solutions can help reveal the particular mechanical mechanism of the time-dependent ground responses due to the combination of rock anisotropy and rheology. Furthermore, they can provide a more accurate prediction of the ground response, which may be useful to optimize the design of tunnel excavation in anisotropic rheological rock masses.

在隧道应用领域,人们经常发现岩体具有各向异性和流变特性。为了优化地下空间的利用,人们通常倾向于使用非圆形隧道。本文对在横向各向同性粘弹性岩体中开挖非圆形隧道所引起的随时间变化的地面响应进行了深入的分析研究。该研究考虑了一系列综合工程因素,包括围岩的粘弹性特征、任意各向异性角和任意隧道形状。利用各向异性弹性和各向异性粘弹性的广义相应原理,引入了一个分析模型。利用各向异性弹性和各向异性粘弹性的一般相应原理,引入了一个分析模型。该模型可以准确、快速地解决各向异性流变岩体中非圆形隧道周围的变形和应力问题。在相同的假设条件下,分析求解结果与有限元法(FEM)结果的良好一致性验证了这一点。此外,分析解决方案与现场数据之间的定性一致进一步验证了分析解决方案的实际应用。然后进行了参数分析,以研究各向异性比、各向异性角和侧压力系数对应力和位移的影响。此外,它们还能提供更准确的地层响应预测,有助于优化各向异性流变岩体中的隧道开挖设计。
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引用次数: 0
Theory and analytical solutions to wellbore problems with hardening/softening Drucker-Prager models 使用硬化/软化德鲁克-普拉格模型解决井筒问题的理论和分析方法
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-23 DOI: 10.1016/j.ijrmms.2024.105878
Tuan Nguyen-Sy , Jian Huang , Herve Gross

Recognizing and quantifying the elasto-plastic nature of underground formations is critical for various subsurface operations such as drilling, stimulation, production, injection, and storage. In the case of geological CO2 storage, for instance, it is key to identify storage sites characteristics and pumping parameters that lead to safe and perennial CO2 trapping. In this work, we investigate different rock hardening/softening behaviors with the Drucker-Prager model: cohesion hardening/softening, friction hardening/softening, and their combination, jointed hardening/softening. Our focus is to solve the elasto-plastic deformation analytically in the vicinity of a wellbore. The three hardening/softening formulations predict different mechanical responses and stress-paths for solving the same wellbore problem with excavation. The analytical solutions for 2D axisymmetric problems with different hardening laws are provided in this study and verified with corresponding numerical results. This approach can be used to interpret field observations and calibrate experimental data with more comprehensive models. These new laws are implemented and benchmarked in GEOS, an open-source advanced numerical simulator of subsurface formations. This study enhances our understanding of subsurface rock's elasto-plastic behavior and offer analytical references for interpretating experimental measurements and developing numerical simulations for solving wellbore problems.

认识和量化地下地层的弹塑性对于钻井、激励、生产、注入和封存等各种地下作业至关重要。以二氧化碳地质封存为例,关键是要确定封存地点的特征和泵送参数,从而实现二氧化碳的安全和长效封存。在这项工作中,我们利用德鲁克-普拉格模型研究了不同的岩石硬化/软化行为:内聚硬化/软化、摩擦硬化/软化以及它们的组合--节理硬化/软化。我们的重点是分析解决井筒附近的弹塑性变形。这三种硬化/软化公式预测了不同的机械响应和应力路径,用于解决带有挖掘的同一井筒问题。本研究提供了具有不同硬化规律的二维轴对称问题的分析解,并用相应的数值结果进行了验证。这种方法可用于解释现场观测结果,并用更全面的模型校准实验数据。这些新定律已在 GEOS(一种开源的地下地层高级数值模拟器)中实施并进行了基准测试。这项研究加深了我们对地下岩石弹塑性行为的理解,为解释实验测量数据和开发数值模拟以解决井筒问题提供了分析参考。
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引用次数: 0
Experimental study on dynamic response of hard rock blasting under in-situ stress 硬岩爆破在原位应力作用下的动态响应实验研究
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-23 DOI: 10.1016/j.ijrmms.2024.105860
Huilin Liu , Linqi Huang , Zhaowei Wang , Yangchun Wu , Xibing Li

Deep mine rock mass is in high static stress and dynamic disturbance coupling conditions, its mechanical properties and failure mode is different from the shallow rock mass, which leads to low rock blasting efficiency and engineering geology hazards. In-depth research on the dynamic response of rock blasting under in-situ stress will help to optimize the blasting design, improve the blasting efficiency and safety of blasting operations, and provide theoretical support for rock blasting in deep mines. In this study, the blasting experiment was conducted on granite specimens under different biaxial static stress conditions. Meanwhile, the dynamic response of rock blasting was monitored, collected, and analyzed using a high-speed digital image correlation (DIC) measurement system, a strain wave acquisition system, and an acoustic emission (AE) system. The results show that small and medium pre-static loads inhibit blast crack propagation, at which time the cumulative AE hits from dynamic loads (CAECd) are more than those from pre-static loads (CAECs), but large pre-static loads promote crack propagation, at which time CAECs are more than CAECd. Secondly, as pre-static load increases, the specimen's maximum strain (εmax) decreases first and then increases, but as lateral pressure coefficient (K) increases, the εmax in the direction of lower static stress decreases gradually and the εmax in the direction of higher static stress remains constant. In addition, the confining pressure magnitude and K affect the area and shape of the failure zone of the specimen, as well as the size and propagation direction of the radial crack. Especially when the confining pressure is high, the specimen will undergo shear failure, and the smaller K is the more serious the shear failure. Finally, the failure criterion of rock under dynamic-static coupling conditions is proposed based on the energy index, and different failure types of rock are discussed.

深部矿山岩体处于高静应力和动态扰动耦合条件下,其力学性质和破坏模式与浅部岩体不同,导致岩石爆破效率低,工程地质危险性大。深入研究岩石爆破在原位应力作用下的动态响应,有助于优化爆破设计,提高爆破效率和爆破作业的安全性,为深部矿山岩石爆破提供理论支持。本研究对不同双轴静应力条件下的花岗岩试样进行了爆破实验,结果表明,花岗岩试样在不同双轴静应力条件下的爆破响应不同。同时,利用高速数字图像相关(DIC)测量系统、应变波采集系统和声发射(AE)系统对岩石爆破的动态响应进行了监测、采集和分析。结果表明,中小型预静态载荷会抑制爆破裂纹扩展,此时动态载荷的累积声发射(CAECd)大于预静态载荷的累积声发射(CAECs),但大型预静态载荷会促进裂纹扩展,此时 CAECs 大于 CAECd。其次,随着预静力荷载的增加,试样的最大应变(εmax)先减小后增大,但随着侧压力系数(K)的增加,较低静力方向上的εmax逐渐减小,而较高静力方向上的εmax保持不变。此外,约束压力大小和 K 会影响试样破坏区的面积和形状,以及径向裂缝的大小和扩展方向。尤其是当约束压力较高时,试样会发生剪切破坏,K 越小,剪切破坏越严重。最后,基于能量指数提出了动静耦合条件下岩石的破坏准则,并讨论了岩石的不同破坏类型。
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引用次数: 0
Fatigue damage evolution behaviors and fractional fatigue mechanical model of monzogabbro under true triaxial disturbance test 单斜辉长岩在真实三轴扰动试验下的疲劳损伤演化行为和分部疲劳力学模型
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-23 DOI: 10.1016/j.ijrmms.2024.105881
Zhi Zheng , Hongyu Xu , Wei Wang , Guoxiong Mei , Wuqiang Cai , Zhi Tang , Zhiyang Cai

The disturbance wave caused by excavation or blasting of underground surrounding rock causes fatigue degradation effect of rock and eventually leads to disasters. However, the fatigue damage characteristics and fatigue models of rock under true triaxial disturbance are scare. Therefore, a series of true triaxial disturbance tests were conducted to investigate the rock fatigue deformation, strength and damage behaviors under different conditions. The evolutions of static damage and fatigue damage are separated and investigated respectively. Fatigue deformation and damage of rock under true triaxial stress undergoes three stages: attenuation, constant velocity and acceleration stage. The crack initiation stress can be as the initial condition of the fatigue deformation; the fatigue critical stress σdc of rock entering the acceleration failure stage was proposed and explored, with increasing frequency, σdc increase slightly and with increasing σ2, σdc increase obviously. Then, a novel fractional fatigue mechanical model considering the fatigue damage and intermediate principal stress effects of rock under true triaxial disturbance was proposed. The theoretical results of the model agree well with the results of the tests. Finally, the sensitivity analysis of stresses and model parameters and the model predictions under other untesting conditions were carried out to improve the understanding and prediction level of fatigue failure in underground engineering.

挖掘或爆破地下围岩时产生的扰动波会引起岩石的疲劳降解效应,并最终导致灾害。然而,岩石在真实三轴扰动下的疲劳破坏特征和疲劳模型却十分罕见。因此,我们进行了一系列真三轴扰动试验,以研究不同条件下岩石的疲劳变形、强度和损伤行为。分别研究了静态损伤和疲劳损伤的演变过程。岩石在真实三轴应力作用下的疲劳变形和损伤经历了三个阶段:衰减阶段、恒速阶段和加速阶段。裂纹起始应力可作为疲劳变形的初始条件;提出并探讨了岩石进入加速破坏阶段的疲劳临界应力σdc,随着频率的增加,σdc略有增加,随着σ2的增加,σdc明显增加。随后,提出了一种考虑岩石在真三轴扰动下的疲劳破坏和中间主应力效应的新型分数疲劳力学模型。模型的理论结果与试验结果吻合良好。最后,对应力和模型参数进行了敏感性分析,并对其他非试验条件下的模型进行了预测,以提高对地下工程疲劳破坏的认识和预测水平。
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引用次数: 0
Insight into the dynamic tensile behavior of deep anisotropic shale reservoir after water-based working fluid cooling 水基工作液冷却后深层各向异性页岩储层动态拉伸行为透视
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-22 DOI: 10.1016/j.ijrmms.2024.105875
Yide Guo , Xibing Li , Linqi Huang , Arcady Dyskin , Elena Pasternak

During deep shale gas production, flowing water-based working fluid inevitably cools shale reservoirs around boreholes and some fractures, and possible extraction methods induce dynamic stresses. To understand the dynamic tensile behavior of deep anisotropic shale reservoir after water-based working fluid cooling, a split Hopkinson pressure bar was used for performing the dynamic Brazilian tests on shale samples with bedding angles of 0°, 30°, 45°, 60° and 90° after reservoir temperature realization (25–200 °C) and water cooling. The results illustrate that dynamic tensile strength of shale samples decreases gradually as reservoir temperature increases under the loading rates 100–1000 GPa/s. From room temperature to 200 °C the most strength deterioration appears on samples with the bedding angle of 90°. A dynamic tensile strength deterioration model for deep shale reservoirs after water-based working fluid cooling is proposed considering the influence of loading rate and bedding angle. Geometrical trajectories of the main failure cracks are separated into three types, i.e., fully central tensile failure, tensile-shear failure and fully shear failure (sliding of bedding planes). For samples with bedding angles of 30°, 45° and 60°, increasing reservoir temperature encourages tensile failure to change into shear failure. The roles that bedding planes play in interacting with failure crack growth are summarized as IP mode (intersecting propagation), TP mode (turning propagation) and PP mode (promoting propagation). Anisotropic dynamic tensile strength responses are systematically discussed by using thermal stress simulation in ABAQUS, microstructure analyses, crack interaction conditions and the one-dimensional stress wave propagation theory. Based on experimental observations, field implications in borehole stability and fracturing of deep shale reservoirs are proposed under medium and high loading rates. This work is instrumental in providing valuable information and technology assistance for real deep shale gas production projects.

在深层页岩气生产过程中,流动的水基工作液不可避免地会冷却钻孔和一些裂缝周围的页岩储层,可能的开采方法会引起动应力。为了解深层各向异性页岩储层在水基工作液冷却后的动态拉伸行为,在储层温度实现(25-200 °C)和水冷却后,使用分体式霍普金森压力棒对基底角为 0°、30°、45°、60°和 90°的页岩样品进行了巴西动态试验。结果表明,在 100-1000 GPa/s 的加载速率下,页岩样品的动态拉伸强度随着储层温度的升高而逐渐降低。从室温到 200 °C,强度下降最多的是基底角为 90° 的样品。考虑到加载速率和铺层角度的影响,提出了水基工作液冷却后深层页岩储层动态拉伸强度劣化模型。主要破坏裂缝的几何轨迹分为三种类型,即完全中心拉伸破坏、拉伸-剪切破坏和完全剪切破坏(垫层平面滑动)。对于基底角为 30°、45° 和 60°的样品,储层温度的升高会促使拉伸破坏转变为剪切破坏。垫层平面与破坏裂纹生长的相互作用可概括为 IP 模式(相交扩展)、TP 模式(转向扩展)和 PP 模式(促进扩展)。通过使用 ABAQUS 中的热应力模拟、微观结构分析、裂纹相互作用条件和一维应力波传播理论,系统地讨论了各向异性动态拉伸强度响应。根据实验观察结果,提出了在中高加载率条件下深层页岩储层井眼稳定性和压裂的现场意义。这项工作有助于为实际的深层页岩气生产项目提供有价值的信息和技术帮助。
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引用次数: 0
Analytical solutions considering face advance and time-dependent behavior for back-analysis of convergence measurements in deep circular tunnels under isotropic initial stress state 在各向同性初始应力状态下,对深圆隧道内收敛测量进行反分析时,考虑面前进和随时间变化行为的分析解决方案
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-20 DOI: 10.1016/j.ijrmms.2024.105866
Alec Tristani, Jean Sulem, Lina-María Guayacán-Carrillo

A methodology is presented for the back-analysis of convergence measurements in deep tunnels to determine the constitutive parameters of the surrounding rock mass. Since increasing deformations and stresses with time are due to both the face advance and the time-dependent behavior of the ground, the two effects must be considered during the excavations. To that end, an analytical solution assuming an unlined circular tunnel excavated in a homogeneous isotropic ground under an initial isotropic stress field and assuming a fractional viscoelastic plastic behavior is developed. A second closed-form solution is also derived assuming an instantaneous excavation. Additionally, combining the developed analytical solution that takes into account the progressive face advance and an empirical approach, convergences are back-analyzed based on a least-squares optimization method to calibrate the constitutive parameters of the ground. The presented methodology aims to characterize the long-term behavior of tunnels and offers the advantage of being directly applicable during the excavation phase as soon as convergence measurements are available. Finally, the method is illustrated by two case studies related to the Fréjus road tunnel and the Saint-Martin-la-Porte access gallery (SMP2).

本文介绍了一种对深埋隧道中的会聚测量进行反分析的方法,以确定周围岩体的构成参数。由于随着时间的推移,变形和应力不断增加,这既是由于工作面的推进,也是由于地层随时间变化的行为,因此在开挖过程中必须考虑这两种影响。为此,我们开发了一种分析解决方案,假设在初始各向同性应力场下,在均质各向同性地层中开挖一条无衬砌圆形隧道,并假定存在部分粘弹性塑性行为。同时还推导出了第二种闭式解,即假设瞬时开挖。此外,结合已开发的考虑到工作面逐步推进的分析解决方案和经验方法,基于最小二乘优化方法对收敛性进行了反向分析,以校准地层的构成参数。所介绍的方法旨在描述隧道的长期行为,其优点是一旦获得收敛测量结果,就可在挖掘阶段直接使用。最后,该方法通过两个与弗雷瑞斯公路隧道和圣马丁拉波尔特通道(SMP2)相关的案例研究进行了说明。
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引用次数: 0
Drilling performance analysis of a polycrystalline diamond compact bit via finite element and experimental investigations 通过有限元和实验研究分析聚晶金刚石紧凑型钻头的钻探性能
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-20 DOI: 10.1016/j.ijrmms.2024.105862
Ahmed Al Shekaili, Yang Liu, Evangelos Papatheou

The significance of improving the drilling productivity and reducing the cost and non-productive time of drilling process, substantially relies on the efficiency of drilling performance. This paper provides a comprehensive understanding of drilling process, aiming to predict drilling performance and investigate drilling parameters using a validated finite element (FE) model. Experimental validation of the FE model was achieved through testing on a laboratory drilling rig, ensuring the accuracy and reliability of the numerical simulations. To accurately capture the nonlinear characteristics of bit-rock interaction, the Riedel–Hiermaier–Thoma model was adopted as a material model, and its parameters were identified through a series of carefully conducted experimental tests. The numerical results obtained from the FE rock failure model during the compressive and tensile tests demonstrated a robust correlation with the experimental data. The verified material model was then employed into another FE drilling model to simulate rock breaking in an actual drilling scenario. This analysis sheds light on the impact of drill-bit interaction with the rock formation, providing valuable insights into its behaviour during drilling operations. The FE drilling model was further utilised in a parametric study to predict the effects of critical drilling parameters, like loading rate and rotary speed, on the weight on the bit, torque on the bit, and rate of penetration. Both the FE drilling and experimental results provided a significant consistency when the drilling parameters were compared, and nonlinear dynamic phenomena, such as stick–slip and bit-bouncing, were observed. By investigating these effects, this study contributes to optimising drilling operations, enabling better control of premature vibrations and enhancing drilling efficiency.

提高钻井生产率、降低钻井过程的成本和非生产时间,在很大程度上取决于钻井性能的效率。本文全面介绍了钻井过程,旨在利用经过验证的有限元(FE)模型预测钻井性能并研究钻井参数。通过在实验室钻机上进行测试,对有限元模型进行了实验验证,确保了数值模拟的准确性和可靠性。为准确捕捉钻头与岩石相互作用的非线性特征,采用了 Riedel-Hiermaier-Thoma 模型作为材料模型,并通过一系列精心进行的实验测试确定了其参数。在压缩和拉伸试验过程中,FE 岩石破坏模型得出的数值结果与实验数据具有很强的相关性。经过验证的材料模型随后被应用到另一个 FE 钻井模型中,以模拟实际钻探情况下的岩石破碎。这项分析揭示了钻头与岩层相互作用的影响,为钻探作业期间的岩层行为提供了宝贵的见解。FE 钻探模型还被进一步用于参数研究,以预测加载率和旋转速度等关键钻探参数对钻头重量、钻头扭矩和穿透率的影响。在对钻进参数进行比较时,FE 钻进结果和实验结果具有明显的一致性,并观察到了粘滑和钻头弹跳等非线性动态现象。通过研究这些影响,本研究有助于优化钻井作业,更好地控制过早振动,提高钻井效率。
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引用次数: 0
Polyaxial failure criteria for in situ stress analysis using borehole breakouts: Review of existing methods and development of an empirical alternative 利用钻孔破裂进行原位应力分析的多轴向破坏标准:审查现有方法并开发经验替代方法
IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Pub Date : 2024-08-20 DOI: 10.1016/j.ijrmms.2024.105864
Maciej Trzeciak, Hiroki Sone

Analysis of compressive wellbore failure, or breakouts, is one of the primary methods of constraining the maximum horizontal stress in deep boreholes. To estimate stress using the observation of breakouts, one needs to measure the breakout width from image logs and use a failure theory to predict the stress that led to the development of the measured breakout. Most commonly, Mohr–Coulomb failure criterion has been used which disregards the influence of intermediate stress on strength. Hence, various polyaxial criteria have been proposed to include this effect. Here, we first review some selected polyaxial criteria: Drucker–Prager, Mogi, Modified Wiebols–Cook, and Modified Lade, and we conclude that their application in breakout analysis may be cumbersome and often unreliable. One reason for these problems is that the criteria are defined using stress invariants, while the stress estimation is most easily performed and analyzed in the principal stress space. Therefore, an alternative is to define the polyaxial criterion as a simple relation between maximum and intermediate stresses. We propose to define such an empirical criterion as a second order polynomial which fits trends observed in polyaxial laboratory strength data. Such approach allows to limit strength overestimation, often associated with the use of previous polyaxial criteria, and to easily relate uncertainties in strength estimation to uncertainty in maximum horizontal stress prediction.

分析压缩性井筒失效或破裂是限制深井眼最大水平应力的主要方法之一。要通过观察破裂来估算应力,需要根据图像测井仪测量破裂宽度,并使用失效理论来预测导致测量破裂的应力。最常用的是莫尔-库仑失效准则,它忽略了中间应力对强度的影响。因此,人们提出了各种多轴判据,以纳入这种影响。在此,我们首先回顾一些选定的多轴准则:我们得出的结论是,在断裂分析中应用这些准则可能很麻烦,而且往往不可靠。造成这些问题的原因之一是,这些标准是使用应力不变式定义的,而应力估计最容易在主应力空间中进行和分析。因此,另一种方法是将多轴标准定义为最大应力和中间应力之间的简单关系。我们建议将这种经验准则定义为二阶多项式,它符合多轴实验室强度数据中观察到的趋势。这种方法可以限制强度过高估计,而强度过高估计通常与使用以前的多轴标准有关,并且可以轻松地将强度估算的不确定性与最大水平应力预测的不确定性联系起来。
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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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