Breakdown Pressure and Propagation Surface of a Hydraulically Pressurized Circular Notch Within a Rock Material

Schwartzkopff, Adam Karl; Melkoumian, N.; Xu, Chaoshui

doi:10.1007/s00603-020-02264-3

Cited by 7 publications

(5 citation statements)

References 38 publications

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“…When explored further, results can be out by 50% when compared against lab experiments [11], with the disparity increasing further at higher stresses. With the current trend of higher stress mining, and a hesitation to adopt a time intensive and testing intensive breakdown model, this leads to an urgent need for a more precise and relevant hard rock breakdown model developed off of the conventional model, and more aligned to linear elastic fracture mechanics by incorporating fracture toughness [12] and if the use of notching can aid in reducing this breakdown pressure and directing fracture propagation.…”

Section: Introductionmentioning

confidence: 93%

The effect of notches on breakdown pressure during hydraulic fracturing at various stress regimes

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Karakus

Amrouch

et al. 2023

IOP Conf. Ser.: Earth Environ. Sci.

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High stress environments are becoming more common as the trend and need to develop deeper block cave mines economically and safely continue. Hydraulic fracturing (HF) is considered to be a powerful tool in the success of hard rock block cave mines as it assists with caveability, economic recovery, and seismic risk mitigation. Therefore, determining critical design parameters such as breakdown pressure and the impact of notching on this parameter is paramount for designing and implementing a successful preconditioning campaign. To better understand the impact of notches on the breakdown and propagation pressure, a series of lab experiments were undertaken with variations in stress regime, stress magnitudes and the presence and number of notches were evaluated. This enabled us to explore the impact of confining pressure and spacing of notches on the breakdown and fracture propagation pressures. Various types of samples including Adelaide Black Granite, Engineered plastic (PMMA) were tested to give ranges and balance for homogeneity and real-world mining applications. We observed the fracture initiation and propagation through breakdown pressures along with acoustic emission measurements. The experimental results confirm that increasing confining stress on a sample increases the breakdown pressure. The works also validate the non-impact of axial stresses and the variation of tensile strength on a sample on the breakdown pressure.

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Section: Introductionmentioning

confidence: 93%

The effect of notches on breakdown pressure during hydraulic fracturing at various stress regimes

Powlay

Karakus

Amrouch

et al. 2023

IOP Conf. Ser.: Earth Environ. Sci.

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“…As we know, the internal defects are misaligned when the materials are subjected to stress, causing microcracks, and they are detected by AE monitoring. Moreover, it was found that the crack propagation surface produced is perpendicular to the minor principal stress direction [28,32]. Since the three decomposed stress orientations are perpendicular to each other, the microcracks should propagate along the other two stress orientations.…”

Section: Theoretical Distribution Pattern Spacementioning

confidence: 99%

“…The investigations of the spatial distribution of cracks have focused on hydraulic fracturing. In particular, the stimulated reservoir volume (SRV) was proposed to estimate the storage of oil and gas [26][27][28]. Convex optimization algorithms such as 3D convex hull and minimum volume enclosing ellipsoid (MVEE) were successfully adopted to evaluate the SRV from the perspective of microcracks [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

“…More importantly, the objective of SRV estimation is to seek volume size rather than the spatial distribution pattern of microcracks under loading conditions. Despite the differences between hydraulic fracturing and rock compression fractures, they share similarities of microcracks distributed in an ellipsoid pattern [23,27,28,38]. Therefore, the methods of SRV assessment can be applied to evaluate the crack space of the compression failure test.…”

Section: Introductionmentioning

confidence: 99%

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Spatial Characterization of Single-Cracked Space Based on Microcrack Distribution in Sandstone Failure

et al. 2023

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To further understand the rock damage zone, an approach based on microcrack distribution was proposed to characterize the crack space of rock specimens in this research. Acoustic emission (AE) technology was utilized on sandstone to obtain the spatial distribution of microcracks in which uniaxial compression forms the single-cracked fracture. The proposed theoretical distribution pattern space (TDPS), 3D convex hull, and the minimum volume enclosing ellipsoid (MVEE) algorithms were adopted to analyze the geometric features of the crack space. It was found that the 3D convex hull method returned the smallest results in both area and volume of the crack space, and the largest results were provided by the proposed TDPS method. The difference between the results of the proposed TDPS method and the MVEE method became smaller after 85%. The deviation angle of the principal axis of the cracked space gradually decreased as the spatial scale decreased, while the other two major axes exhibited a tendency to increase at the 65% scale. The results indicate that a spatial scale from 65% to 85% is a reliable range for the characterization of crack space.

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“…In previous studies, cracks were classified into two categories according to the causes of rock cracks: tensile cracks and shear cracks. The damage modes of the specimens were classified into tensile and shear damage according to the type of the main cracks that led to the damage of the specimens (Chen, 2019;Mei et al, 2019;Schwartzkopff et al, 2020). It was shown that when tensile damage occurred, the surface of the specimens was clean, with traces of tensile cracks clearly visible and no obvious fragmentation.…”

Section: Macroscopic Crack Expansion Pattern and Damage Mode Of Speci...mentioning

confidence: 99%

Effects of Normal Stress and Joint Inclination Angle on Rock Failure Characteristics Under Compression–Shear Conditions

Chen

Liu

Wang³

et al. 2022

Front. Earth Sci.

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In this study, cement mortar was used to make specimens containing groups of parallel joints with different inclination angles to simulate natural rock mass, and the specimens were subjected to shear tests under different normal stresses. By analyzing the crack propagation path, failure modes, and strength characteristics of these rock specimens, the effects of normal stress and joint inclination angles on the strength and failure characteristics of this type of rock mass were studied. The following conclusions are drawn: 1) when the inclination angles of the joints are 0° and 15°, the changing of the normal stress did not affect the failure mode of the rock mass. The rock mass was mainly in the mode of shear failure, and the increase in the normal stress only increased the spalling area of the rock mass. 2) When the inclination angles of the joints are 30°, 45°, and 60°, with the increasing of the normal stress, the number of those approximately parallel cracks in the specimens increased, the friction marks caused by shearing increased, and the failure mode of the rock mass changed from tension failure to tension–shear composite failure. 3) Under different joint inclination angles, the propagation and penetration paths of cracks generated in the rock mass and the damage mode of the rock mass were different. With an increase in the joint inclination angles, the damage mode of the rock mass gradually changes from shear damage to tensile–shear composite damage and the α and β angles between the through cracks and the vertical direction on the left and right sides of the specimens tended to decrease. 4) The shear resistance of the rock mass was affected by the inclination angle of the joints and the normal pressure. The shear resistance of rock mass was improved due to the increasing of normal stress. Within a certain range, with the increasing of the inclination angles of the joint, the shear resistance of the rock mass tended to decrease first and then to increase.

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Breakdown Pressure and Propagation Surface of a Hydraulically Pressurized Circular Notch Within a Rock Material

Cited by 7 publications

References 38 publications

The effect of notches on breakdown pressure during hydraulic fracturing at various stress regimes

The effect of notches on breakdown pressure during hydraulic fracturing at various stress regimes

Spatial Characterization of Single-Cracked Space Based on Microcrack Distribution in Sandstone Failure

Effects of Normal Stress and Joint Inclination Angle on Rock Failure Characteristics Under Compression–Shear Conditions

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