Cleavage Dependent Indirect Tensile Strength of Pocheon Granite Based on Experiments and DEM Simulation

Zhuang, Łi; Diaz, Melvin; Jung, Sung Gyu; Kim, Kwang Yeom

doi:10.7474/tus.2016.26.4.316

Cited by 6 publications

(6 citation statements)

References 17 publications

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“…These observations are confirmed in other cases regardless of the injection scheme, although the frequency of occurrence varies from case to case. As preexisting microcracks are abundant in the Pocheon granite (Zhuang et al 2016(Zhuang et al , 2019a, the chips formed are likely created when hydraulic fractures interacted with microcracks in quartz grains, resulting in crisscrossed fractured quartz grains. This will help to enlarge the damage zone and improve the permeability increase.…”

Section: Discussionmentioning

confidence: 99%

“…The anisotropy of granites with microscopic fabric is analyzed according to Douglass and Voight (1969). The three cleavage planes, called rift, grain and hardway, cannot be ignored in laboratory scale testing on either mechanical or hydraulic fracturing (Zhuang et al 2016(Zhuang et al , 2019a(Zhuang et al , 2020. The applied three principal stresses are 4 MPa in vertical direction, 6 MPa for the maximum horizontal stress and 3 MPa for the minimum horizontal stress.…”

Section: Test Specimens Stress Conditions and Acoustic Emission Monit...mentioning

confidence: 99%

“…The applied three principal stresses are 4 MPa in vertical direction, 6 MPa for the maximum horizontal stress and 3 MPa for the minimum horizontal stress. The maximum horizontal stress is applied perpendicular to the hardway plane; therefore, fractures are expected to be generated along the rift plane, which has the smallest tensile strength and mode I fracture toughness among the three cleavage planes (Zhuang et al 2016(Zhuang et al , 2020.…”

Section: Test Specimens Stress Conditions and Acoustic Emission Monit...mentioning

confidence: 99%

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Laboratory True Triaxial Hydraulic Fracturing of Granite Under Six Fluid Injection Schemes and Grain-Scale Fracture Observations

et al. 2020

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Laboratory hydraulic fracturing tests on cubic granite specimens with a side length of 100 mm were performed under true triaxial stress conditions combined with acoustic emission monitoring. Six different injection schemes were applied to investigate the influence of the injection scheme on hydraulic performance and induced seismicity during hydraulic fracturing. Three of these schemes are injection rate controlled: constant rate continuous injection (CCI), stepwise rate continuous injection (SCI), and cyclic progressive injection (CPI); the other three are pressurization rate controlled: stepwise pressurization (SP), stepwise pulse pressurization (SPP) and cyclic pulse pressurization (CPP). The test results show that the SPP scheme achieves the highest increase in injectivity among the six schemes. The CPI scheme generates the lowest induced seismicity while the improvement in injectivity is the least pronounced. The CPP scheme allows increasing injectivity and decreasing induced seismicity, and is suggested as a promising alternative injection scheme for field applications. Thin section microscopic observations of fractured specimens show that intragranular fractures splitting microcline, orthoclase and quartz grains dominate the hydraulic fractures independent of the injection scheme. The SPP scheme creates the largest fracture length, which explains the highest injectivity value among all schemes. Tests with relatively low magnitude of maximum AE amplitude correspond to short fracture length and small portions of intragranular fractures in microcline grains. Quartz grains are more fractured than microcline and orthoclase grains, and quartz chips (natural proppants) are frequently observed adjacent to hydraulic fractures. The laboratory test results show the potential for hydraulic fracture growth control in field applications by advanced fluid injection schemes, i.e. cyclic pulse pressurization of granitic rock mass.

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Section: Discussionmentioning

confidence: 99%

Section: Test Specimens Stress Conditions and Acoustic Emission Monit...mentioning

confidence: 99%

Section: Test Specimens Stress Conditions and Acoustic Emission Monit...mentioning

confidence: 99%

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Laboratory True Triaxial Hydraulic Fracturing of Granite Under Six Fluid Injection Schemes and Grain-Scale Fracture Observations

et al. 2020

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“…The average measured effective porosity is 0.66%. This granite shows mild but clear anisotropy, with three typical cleavages of rift (R), grain (G) and hardway (H), which have different densities of microcracks (Zhuang et al 2016a). As shown in Fig.…”

Section: Test Samplesmentioning

confidence: 90%

Laboratory Investigations on the Hydraulic Fracturing of Granite Cores

Zhuang

Jung

Diaz

et al. 2020

Modelling Rock Fracturing Processes

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This chapter introduces laboratory studies on the hydraulic fracturing of granite cores. Some of the most important factors influencing fracturing are considered, including injection rate, fluid infiltration, fluid viscosity, borehole size, and injection scheme. Results from acoustic emission monitoring help elucidate the fracturing process. Hydraulic fractures of granite samples are observed and analysed at the mineral scale with the aid of X-ray scanning and Computed Tomography. A first attempt to investigate the initiation and propagation of hydraulic fractures in granite drill cores during cyclic injection is presented.

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“…The measured average grain size is 0.94 mm in rift plane, 1.01 mm in grain plane and 0.91 mm in hardway plane. Among the three planes, rift plane has the highest microcrack density and therefore its tensile strength is the lowest, whereas the hardway plane has the lowest microcrack density and the highest tensile strength (Park et al 2004;Zhuang et al 2016b). Figure 2a, b shows microcracks in a thin section of Pocheon granite cut parallel to the rift plane.…”

Section: Rock Samplementioning

confidence: 99%

Effect of Water Infiltration, Injection Rate and Anisotropy on Hydraulic Fracturing Behavior of Granite

et al. 2018

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Hydraulic fracturing tests on Pocheon granite cylinders at seven different injection rates varying from 1 to 100 mm 3 /s were conducted. They were compared with sleeve fracturing tests in which borehole was sleeved, and therefore, water infiltration influence was excluded. Hydraulic fracturing behavior of granite is significantly influenced by water infiltration, which is closely related to the preexisting microcracks in granite as well as the cleavage anisotropy. There was a threshold injection rate to fracture the granite specimen under given stress conditions. When the injection rate is below the threshold, water infiltrated granite matrix with slow increment of injection pressure, and the specimen finally reached a full saturation without fracturing. Injection pressure developed nonlinearly with time during water infiltration, while approximately linearly when infiltration was excluded. For both hydraulic and sleeve fracturing tests, breakdown pressure increases with increasing injection rate. The breakdown pressures by sleeve fracturing were more than two times higher than those in hydraulic fracturing. X-ray computed tomography (CT) observations show that induced fractures are along the weaker cleavage parallel to the direction of the vertical stress. The higher breakdown pressure results in a larger aperture of fractures in hydraulic fracturing tests.

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Cleavage Dependent Indirect Tensile Strength of Pocheon Granite Based on Experiments and DEM Simulation

Cited by 6 publications

References 17 publications

Laboratory True Triaxial Hydraulic Fracturing of Granite Under Six Fluid Injection Schemes and Grain-Scale Fracture Observations

Laboratory True Triaxial Hydraulic Fracturing of Granite Under Six Fluid Injection Schemes and Grain-Scale Fracture Observations

Laboratory Investigations on the Hydraulic Fracturing of Granite Cores

Effect of Water Infiltration, Injection Rate and Anisotropy on Hydraulic Fracturing Behavior of Granite

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