Experimental investigation of crack evolution and failure behaviors in dual-curved flawed shale under hydraulic-mechanical loading

IF 5.6 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics Pub Date : 2025-09-29 DOI:10.1016/j.tafmec.2025.105264

Wei Yi , Shuxin Huang , Binghui Xu , Mingfeng Lei , Yinian Wu , Chaojun Jia , Qiujing Pan

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引用次数: 0

Abstract

Investigating crack evolution and failure behaviors in flawed shale under hydro-mechanical loading holds critical significance for improving reservoir stimulation efficiency, and ensuring wellbore stability in shale gas development. While existing studies mainly focus on straight-flawed rock and rock-like under single stress state, the behavior of bedding shale with curved flaws under hydro-mechanical loading remains poorly understood. Additionally, digital image correlation (DIC) techniques, though effective in monitoring crack propagation under compression, have rarely been applied in hydro-mechanical conditions. This study developed a transparent enclosure apparatus capable of applying hydraulic pressure directly to crack surfaces in shale specimens. A series of systematic hydraulic-mechanical experiments, combined with DIC technique, were performed on bedding shale specimens with dual circular arc flaws, to investigate the effects of hydraulic pressure (P_H), bedding angle (α), and flaw curvature (κ) on crack propagation process and failure behaviors. Quantitative characterization of crack network complexity and connectivity was achieved through fractal dimension and topological analysis. Result shows that α has a greatest impact on the compaction stage, followed by P_H, and finally κ, with increasing P_H and α progressively suppressing compaction effects until near elimination. Nine crack types are identified, with α exerting a stronger influence than P_H and κ, particularly at larger α. κ predominantly controls non-tip crack initiation, followed by α, while P_H plays the minimal effect. Non-tip crack initiation usually appears in conjunction with the non-tip coalescence of rock bridges. The highest crack network complexity (D = 1.381) corresponds to moderate connectivity (normalized parameter

η_{C}^{'}

= 0.667), whereas the greatest connectivity (D = 0.737) exhibits lower complexity (

η_{C}^{'}

= 1.363), indicating no direct correlation between the crack network complexity and connectivity. The complexity of the crack network does not exhibit a direct correlation with its connectivity, and greater complexity degree of crack network does not necessarily result in a larger connectivity. This study might provide valuable insights into the crack evolution and failure behavior of shale, contributing to the advancement of shale gas exploration strategies

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水力-力学载荷作用下双弯曲缺陷页岩裂纹演化及破坏行为试验研究

在页岩气开发中，研究有缺陷页岩在水力力学载荷作用下的裂缝演化与破坏行为，对提高储层增产效率、保证井筒稳定性具有重要意义。现有的研究主要集中在单一应力状态下的直缺陷岩和类岩石，而对含弯曲缺陷的层理页岩在水-力加载下的行为了解较少。此外，数字图像相关（DIC）技术虽然可以有效地监测压缩条件下的裂纹扩展，但很少应用于水力力学条件。本研究开发了一种透明的封闭装置，能够直接对页岩试样的裂缝表面施加水力压力。通过系统的水力力学试验，结合DIC技术，对具有双圆弧缺陷的层理页岩试样进行了试验，研究了水力压力（PH）、层理角度（α）和缺陷曲率（κ）对裂纹扩展过程和破坏行为的影响。通过分形维数和拓扑分析，定量表征裂缝网络的复杂性和连通性。结果表明，α对压实阶段的影响最大，其次是PH，最后是κ，随着PH的增加，α逐渐抑制压实作用，直至接近消除。9种裂纹类型中，α对裂纹的影响强于PH和κ，特别是α较大时。κ主要控制非尖端裂纹萌生，其次是α， PH影响最小。非尖端裂纹起裂通常与岩石桥梁的非尖端聚并同时发生。裂缝网络复杂度最高（D = 1.381）对应中等连通性（归一化参数ηC′= 0.667），而连通性最高（D = 0.737）对应较低的连通性（ηC′= 1.363），说明裂缝网络复杂度与连通性之间没有直接关系。裂缝网络的复杂程度与其连通性并不直接相关，裂缝网络的复杂程度越大，连通性也不一定越大。该研究为页岩裂缝演化和破坏行为提供了有价值的见解，有助于页岩气勘探策略的改进

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来源期刊

Theoretical and Applied Fracture Mechanics 工程技术-工程：机械

CiteScore

8.40

自引率

18.90%

发文量

435

审稿时长

37 days

期刊介绍： Theoretical and Applied Fracture Mechanics'' aims & scopes have been re-designed to cover both the theoretical, applied, and numerical aspects associated with those cracking related phenomena taking place, at a micro-, meso-, and macroscopic level, in materials/components/structures of any kind. The journal aims to cover the cracking/mechanical behaviour of materials/components/structures in those situations involving both time-independent and time-dependent system of external forces/moments (such as, for instance, quasi-static, impulsive, impact, blasting, creep, contact, and fatigue loading). Since, under the above circumstances, the mechanical behaviour of cracked materials/components/structures is also affected by the environmental conditions, the journal would consider also those theoretical/experimental research works investigating the effect of external variables such as, for instance, the effect of corrosive environments as well as of high/low-temperature.