Numerical modelling of bit–rock fracture mechanisms in percussive drilling with a continuum approach

Saksala, Timo

doi:10.1002/nag.974

Cited by 32 publications

(37 citation statements)

References 26 publications

(76 reference statements)

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“…This paper is a direct continuation of the work presented by the author in [1]. Therein, a method for dynamic bit-rock interaction simulation, including the constitutive model presented in [2] and a method for simulating the bit-rock interaction using contact mechanics, was presented.…”

Section: Introductionmentioning

confidence: 90%

“…In this paper, the constitutive model presented in [1,2] is improved by determining the softening moduli via the fracture energies in modes I and II, providing a mesh objective dissipation. Moreover, values for the viscosity modulus in tension is selected here according to the dynamic calibration carried out in [12] based on the dynamic Brazilian disc test.…”

Section: Introductionmentioning

confidence: 99%

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3D numerical modelling of bit‐rock fracture mechanisms in percussive drilling with a multiple‐button bit

Saksala

2013

Num Anal Meth Geomechanics

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Regrettably, the author noticed an error in the code used to compute all the results in the original paper. Namely, the ordering of the last two shear components of the strain/stress vector (6Â1 vector in the Voigt notation) was not consistent. When this error was fixed, the results changed notably. Consequently, the analyses of the results in the original paper are not fully correct.In what follows, the re-computed results are presented along with their corrected analyses as well as the other errors or misprints found in the original manuscript.In the second paragraph in Section 4 (Numerical simulations), the Weibull distribution parameters should read x u = 5 MPa, x u = 50 MPa, not x u = 6 MPa, x u = 60 MPa.In Figure 2a in Section 4.1 (Single-button bit case: simulations with different button geometries), the radius of the button should read R = 5 mm, not R = 10 mm.

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Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

3D numerical modelling of bit‐rock fracture mechanisms in percussive drilling with a multiple‐button bit

Saksala

2013

Num Anal Meth Geomechanics

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“…In the second step, the three eigenvalues of the microscopic stress tensor are computed. In case of positive microscopic eigenstresses, a damage variable is calculated according to Eqn (5) and the macroscopic stress is derived (refer to Eqn (6). Finally, the macroscopic stress tensor is written in the initial basis.…”

Section: Effect Of Structural Cracksmentioning

confidence: 99%

A numerical study of the influence from pre‐existing cracks on granite rock fragmentation at percussive drilling

Saadati

Forquin

Weddfelt

et al. 2014

Num Anal Meth Geomechanics

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SUMMARYThe aim of this study is to investigate the effect of pre-existing, or structural, cracks on dynamic fragmentation of granite. Because of the complex behavior of rock materials, a continuum approach is employed relying upon a plasticity model with yield surface locus as a quadratic function of the mean pressure in the principal stress space coupled with an anisotropic damage model. In particular, Bohus granite rock is investigated, and the material parameters are chosen based on previous experiments. The equation of motion is discretized using a finite element approach, and the explicit time integration method is employed. The pre-existing cracks are introduced in the model by considering sets of elements with negligible tensile strength that leads to their immediate failure when loaded in tension even though they still carry compressive loads as crack closure occurs because of compressive stresses. Previously performed edge-on impact tests are reconsidered here to validate the numerical model. Percussive drilling is simulated, and the influence of the presence of pre-existing cracks is studied. The results from the analysis with different crack lengths and orientations are compared in terms of penetration stiffness and fracture pattern. It is shown that pre-existing cracks in all investigated cases facilitate the drilling process.

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“…These results are in good agreement with the present ones reported above. In this context it should also be mentioned that Saksala [1] reports a somewhat higher value, 80 GPa, on the compressive Youngs's modulus for Bukit Timah granite. This value is of course higher than the ones determined here but is obviously for another type of granite material.…”

Section: Direct Compression and Tensile Testsmentioning

confidence: 99%

“…Unlike the situation at quasi-static indentation, the stress waves and rapid indentation make percussive drilling a transient dynamic problem with high local strain rates in the rock [1]. The final aim of this investigation is to numerically simulate the rock fragmentation mechanism during percussive drilling as a dynamic problem.…”

Section: Introductionmentioning

confidence: 99%

On the Mechanical Behavior of Granite Material With Particular Emphasis on the Influence From Pre-Existing Cracks and Defects

Saadati

Forquin

Weddfelt

et al. 2018

Journal of Testing and Evaluation

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In this investigation, experiments were carried out in order to determine the mechanical properties of Bohus granite considering the influence from pre-existing cracks and defects. The experimental investigation aimed at a complete material characterization, for the purpose of mechanical analyses using advanced constitutive models, based on a variety of tests. In doing so, direct tensile and compression tests were performed to evaluate the stiffness and strength; quasi-oedometric tests were carried out in order to obtain the deviatoric and volumetric behavior of the material at different levels of hydrostatic pressure (up to 860 MPa); three-point bend tests were performed to evaluate the quasi-static strength of the rock and its distribution. Weibull statistics was then employed to describe the strength distribution. The intact specimens indicated a rather low scatter in the mechanical properties such as Young’s modulus and tensile strength. However, specimens with large initial defects behaved differently. The failure mechanism in these specimens was not as brittle as the intact ones. The crack was opened on the tensile surface of such specimens during the three-point bend test at an early stage during loading, as demonstrated by digital image correlation results.

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Numerical modelling of bit–rock fracture mechanisms in percussive drilling with a continuum approach

Cited by 32 publications

References 26 publications

3D numerical modelling of bit‐rock fracture mechanisms in percussive drilling with a multiple‐button bit

3D numerical modelling of bit‐rock fracture mechanisms in percussive drilling with a multiple‐button bit

A numerical study of the influence from pre‐existing cracks on granite rock fragmentation at percussive drilling

On the Mechanical Behavior of Granite Material With Particular Emphasis on the Influence From Pre-Existing Cracks and Defects

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