Fractal fracture toughness measurements of heat-treated granite using hydraulic fracturing under different injection flow rates

Zhuang, Dengdeng; Yin, Tubing; Li, Qiang; Wu, You; Chen, Yongjun; Yang, Zheng

doi:10.1016/j.tafmec.2022.103340

Cited by 28 publications

(10 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Fractal dimension reflects the complexity of a fracture surface, and the larger the fracture dimension, the rougher the surface. Previous research found that the fractal dimension for rock fracture surfaces typically ranged between 2 and 2.5 and possibly ranged between 2 and 3 (Jiang et al., 2006; D. Zhuang et al., 2022), which agrees with our tested values ranging between 2.9 and 3 (Figure 12b).…”

Section: Resultssupporting

confidence: 91%

Mode I Microscopic Cracking Process of Granite Considering the Criticality of Failure

Mo,

Zhao,

Zhang

2023

JGR Solid Earth

View full text Add to dashboard Cite

Rock failure under tensile loading conditions is significant for rock engineering stability and underground energy development. However, a comprehensive understanding of the rock cracking process and the corresponding failure pattern at microscale remains unclear. Therefore, the cracking process and the damage evolution of rock and their underlying mechanisms were systematically investigated. In this study, the fracture behavior of granite was examined by performing mode I fracture tests. For extensive analysis of the cracking process, the cracks were captured in real‐time by scanning electron microscope, and the two fracture toughnesses of the double‐K model were evaluated. Subsequently, fracture morphologies of the post‐failure specimens were analyzed to further investigate the cracking mechanisms. The experimental results indicated the following: (a) the propagated direction of cracks was controlled by the fracture toughness of mineral grains and grain boundaries; and (b) the ratio of the two fracture toughnesses was correlated with fracture tortuosity. Furthermore, two damage modes of granite were found: catastrophic failure and non‐catastrophic failure modes. The former showed precursory behavior prior to catastrophic failure, while the latter did not. The underlying mechanisms of damage modes were revealed as follows: (a) the increased degree of heterogeneity caused by mineral composition complexity led to the early arrival of precursors; and (b) the occurrence of catastrophic or non‐catastrophic failure mode was determined by the difference in grain‐scale heterogeneity. Our results found at microscale also have implications for understanding the macroscopic failure process of rocks.

show abstract

Section: Resultssupporting

confidence: 91%

Mode I Microscopic Cracking Process of Granite Considering the Criticality of Failure

Mo,

Zhao,

Zhang

2023

JGR Solid Earth

View full text Add to dashboard Cite

show abstract

“…Figure 6 shows the hydraulic injection pressure‐time and pressurization rate‐time curves of the granite specimens in Group X. It can be seen that the figures follow the typical pressure‐time curves of the hydraulic fracturing tests 37 and the pressure evolution curves can be divided into four stages: (I) initial pressure development, (II) wellbore pressurization, (III) fracturing, and (IV) post‐fracturing.…”

Section: Testing Resultsmentioning

confidence: 86%

Experimental study of fatigue load effect on the hydraulic fracturing behavior of granite

Zhu

et al. 2022

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

Rock masses around fluid injection projects are usually subject to complex stress states, including hydraulic pressure, in situ stresses, and fatigue loads.Thus, a series of hydraulic fracturing experiments were performed on granite to simulate such stress states using the true triaxial dynamic testing system.Computed tomographic (CT) imaging was performed to identify the fatigue effects on hydraulic fractures. The results indicate that the increasing amplitudes of cyclic load applied on the minimum principal stress direction will change fracture initiation pressure and generate nonplanar and narrow fractures. When the disturbance direction was changed to the intermediate principal stress, the higher amplitude corresponds to the lower breakdown pressure and the shorter pressurize duration and leads to wider fractures. With the increasing disturbance frequency, complex fatigue cracks were generated, which might weaken the rock strength. The present experiments can enhance the understanding of the hazard of fatigue loads on hydraulic fracturing.

show abstract

“…It is obvious that the conventional calculation model is based on the hypothesis that the surrounding stress field and the minimum shear stress remain constant after the hydraulic crack re-extends, thus the reopening pressure only lacks tensile strength compared to the breakdown pressure [ 43 , 44 ]. However, this hypothesis is contrary to fracture mechanics theory, where the stress field around the hydraulic crack is inevitably altered as it re-extends [ 45 , 46 ]. Therefore, it is not valid to calculate the reopening pressure using the continuous assumptions of the elastic-plastic theory, and a new calculation model based on fracture mechanics should be developed.…”

Section: Calculation Model For Hydraulic Fracturing Reopening Pressurementioning

confidence: 97%

An Innovative Method to Analyze the Hydraulic Fracture Reopening Pressure of Hot Dry Rock

et al. 2023

Self Cite

View full text Add to dashboard Cite

This paper focuses on a new test method and theoretical model for measuring and evaluating the reopening pressure during hot dry rock hydraulic fracturing. Firstly, rock blocks of four lithologies were collected from the hot dry rock strata. Hydraulic fracturing tests at high temperatures in real-time were conducted using drilled cubic specimens and drilled cubic specimens with a pre-crack. Breakdown pressure, reopening pressure, and fracture toughness were measured, respectively. In addition, Brazilian splitting tests at high temperatures in real-time were performed using Brazilian disc specimens to measure tensile strength. Secondly, an empirical equation for evaluating the reopening pressure during hot dry rock secondary fracturing was developed based on fracture mechanics and hydraulic fracturing theory. Third, the values calculated by the new equation, considering breakdown pressure, fracture toughness, and tensile strength, were compared to the values determined by the classical equation and to measurement results. It was found that the new equation predicted closer reopening pressure to the measurement results, regardless of the lithology of the hot dry rock. Moreover, with increasing temperature in the specimens, the error between the value calculated by the new equation and the measurement value remained low. In contrast, the difference between the classical equation predictions and the measurement results was widened. In addition, the reopening pressure was positively correlated with tensile strength and fracture toughness. Variations in lithology and temperature affected tensile strength and fracture toughness, which then changed the hot dry rock reopening pressure.

show abstract

Fractal fracture toughness measurements of heat-treated granite using hydraulic fracturing under different injection flow rates

Cited by 28 publications

References 50 publications

Mode I Microscopic Cracking Process of Granite Considering the Criticality of Failure

Mode I Microscopic Cracking Process of Granite Considering the Criticality of Failure

Experimental study of fatigue load effect on the hydraulic fracturing behavior of granite

An Innovative Method to Analyze the Hydraulic Fracture Reopening Pressure of Hot Dry Rock

Contact Info

Product

Resources

About