Brittle crack growth in rocks

Müller, W.

doi:10.1007/bf00879605

Cited by 18 publications

(10 citation statements)

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“…Several authors studied the effect of confining pressure on K!c. [23][24][25][26][27] The trend is always an increase in Klc with an increase in confining pressure (see Table 2). If this trend is extrapolated to confining pressures typical of field conditions, Klc increases by a factor of two or three compared with values of KIc determined without confining stress.…”

Section: Parameters Affecting Fracture Toughnessmentioning

confidence: 99%

Influence of Fracture Toughness on the Geometry of Hydraulic Fractures

Thiercelin

Jeffrey

Naceur

1989

SPE Production Engineering

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Section: Parameters Affecting Fracture Toughnessmentioning

confidence: 99%

Influence of Fracture Toughness on the Geometry of Hydraulic Fractures

Thiercelin

Jeffrey

Naceur

1989

SPE Production Engineering

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“…Severe penetration into the pore space of the rocks may lead to build-up of a pore pressure of unknown magnitude. Previous experiments indicated that an effective pressure law holds for toughness; when the confining fluid penetrated cracks and pores right from the start of an experiment (samples without any jacketing), an effect of absolute pressure on K IC was not observed (Balme et al 2004;Müller 1986). We address whether penetration issues affect our results for toughness by comparing the results for the two notch geometries and estimating penetration times.…”

Section: The Dependence Of Fracture Toughness On Uniform Pressurementioning

confidence: 93%

“…For the testing at elevated pressure, a custom-designed apparatus (Fig. 10) was used, composed of a vessel and a loading system (Winter 1983;Müller 1986). The vessel accommodates a specimen immersed in pressurized oil that applies the confining pressure.…”

Section: Testing Apparatusmentioning

confidence: 99%

“…Previous experimental studies (Schmidt and Huddle 1977;Winter 1983;Müller 1986;Al-Shayea et al 2000;Vásárhelyi 2001;Balme et al 2004;Funatsu et al 2004Funatsu et al , 2014Backers 2005;Sato and Hashida 2006;Kataoka et al 2017) indicate that fracture toughness increases with confining pressure, with the relation reported to be either linear (e.g., Al-Shayea et al 2000) or logarithmic (e.g., Funatsu et al 2004). Yet, no noticeable increase in fracture toughness with pressure has also been reported (Müller 1986;Balme et al 2004). The different observations may be a result of different experimental procedures and data reduction, the latter actually not fully disclosed in cases.…”

Section: Introductionmentioning

confidence: 98%

“…In previous studies, specimens were coated with urethane (Schmidt and Huddle 1977), silicone (Funatsu et al 2004(Funatsu et al , 2014Kataoka et al 2017), varnish (Winter 1983), or glossy spray paint (Al-Shayea et al 2000) exhibiting variable suitability for rocks with high porosity. Specimens were also jacketed with flexible materials, e.g., rubber tubes (Müller 1986;Vásárhelyi 2001), scotch tape (Al-Shayea et al 2000;Funatsu et al 2004) or copper sheets (Kataoka et al 2017), covering the notch such that confining fluid does not penetrate it. The sealing methods thus correspond to different scenarios regarding the difference between pressure acting on the bulk sample and in the notch.…”

Section: Introductionmentioning

confidence: 99%

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Determination of Fracture Toughness of Mode I Fractures from Three-Point Bending Tests at Elevated Confining Pressures

2021

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Fracture toughness is one of the key parameters for the characterization of brittle rock fracturing. Yet, constraints on it mainly rest on measurements performed at ambient pressure, although rock fracturing frequently occurs at elevated pressures even in geotechnical applications. To address the lack of a generally accepted evaluation procedure for tests at elevated pressure we explored the conditions for initiation and propagation of mode I fractures in samples subjected to bending at elevated pressure by numerical modeling and analytical considerations of the involved angular moments. We derived an evaluation procedure and applied it to experimental observations for specimens with either a chevron or a single-edge notch of four different rocks (a granite, a limestone, a marble and a sandstone) subjected to three-point bending at confining pressures up to 30 MPa. Two sealing methods were considered. Specimens were either varnished or jacketed by a rubber tube, differing in whether pressure is allowed to build up inside the pre-fabricated notch or not, respectively. Irrespective of notch geometry and sealing method, the determined toughness values increase significantly with confining pressure. The apparent toughness determined for jacketed specimens is, however, larger than that for varnished specimens, for which toughness seems to reach a plateau with increasing pressure. The similarity of the pressure dependence of the toughness determined for varnished, i.e., uniformly pressurized, samples with that of other physical properties suggests that it is controlled by the closure of pre-existing micro-cracks; the absence of pressure dependence beyond some tens of MPa suggests that non-linearity effects may not be as severe at depths beyond a few kilometers as previously discussed. Our study points to the necessity of resolving numerical issues associated with compressed fractures and of further improving experimental facilities for the determination of fracture toughness at elevated pressure.

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Comparing Reservoir and Outcrop Specimens for Mixed Mode I-II Fracture Toughness of a Limestone Rock Formation at Various Conditions

Al-Shayea

2002

Rock Mechanics and Rock Engineering

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Brittle crack growth in rocks

Cited by 18 publications

References 4 publications

Influence of Fracture Toughness on the Geometry of Hydraulic Fractures

Influence of Fracture Toughness on the Geometry of Hydraulic Fractures

Determination of Fracture Toughness of Mode I Fractures from Three-Point Bending Tests at Elevated Confining Pressures

Comparing Reservoir and Outcrop Specimens for Mixed Mode I-II Fracture Toughness of a Limestone Rock Formation at Various Conditions

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