A bond failure criterion for DEM simulations of cemented geomaterials considering variable bond thickness

Jiang, Mingjing; Liu, Fang; Zhou, Yaping

doi:10.1002/nag.2282

Cited by 26 publications

(22 citation statements)

References 63 publications

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“…It has been reported that both the mechanical behavior and the bond strength are different for different bond models, which was concluded from the experimental data obtained for two aluminium rods bonded by cement with a fixed bond width . As a first step in simulation analyses considering the effect of bond model, Jiang et al proposed a new bond failure criterion for DEM simulations of bonded granulates. Thereafter, Jiang et al performed loading tests on a couple of aluminium rods glued together by cement with various values of width and thickness and proposed a rigorous failure criterion for the inter‐particle bonding.…”

Section: Introductionmentioning

confidence: 99%

A simple three‐dimensional distinct element modeling of the mechanical behavior of bonded sands

Jiang

Zhang

Thornton

2015

Num Anal Meth Geomechanics

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Summary This paper presents a simple three‐dimensional (3D) Distinct Element Method (DEM) for numerical simulation of the mechanical behavior of bonded sands. First, a series of micro‐mechanical tests on a pair of aluminum rods glued together by cement with different bond sizes were performed to obtain the contact mechanical responses of ideally bonded granular material. Second, a 3D bond contact model, which takes into account the influences of bond sizes, was established by extending the obtained 2D experimental results to 3D case. Then, a DEM incorporating the new contact model was employed to perform a set of drained triaxial compression tests on the DEM bonded specimens with different cement contents under different confining pressures. Finally, the mechanical behavior of the bonded specimens was compared with the available experimental results. The results show that the DEM incorporating the simple 3D bond contact model is able to capture the main mechanical behavior of bonded sands. The bonded specimen with higher cement content under lower confining pressure exhibits more pronounced strain softening and shear dilatancy. The peak and residual strengths, the apparent cohesion and peak/residual friction angles, and the position and slope of the critical state line increase with increase in cement content. Microscopically, bond breakage starts when the system starts to dilate and the maximum rate of bond breakage coincides with the maximum rate of dilation. Bond breakage is primarily due to tension‐shear failure and the percentage of such failures is independent of both confining pressure and cement content. Copyright © 2015 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

A simple three‐dimensional distinct element modeling of the mechanical behavior of bonded sands

Jiang

Zhang

Thornton

2015

Num Anal Meth Geomechanics

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“…The significance of bond thickness on the contact behaviour has been experimentally confirmed by Jiang et al (2014), indicating the need for a size-dependent bond contact law for a rigorous DEM analysis.…”

Section: Introductionmentioning

confidence: 91%

On the size-dependent compressive resistance of bonded granules

Liu¹,

Jiang²

2015

Géotechnique Letters

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Peculiar properties of cemented geomaterials are endowed by inter-particle bonds, of which the contact behaviour has recently been found to be size dependent. This study uses the distinct-element method to investigate the size effect on the compressive resistance of an inter-particle bond, which is modelled as an assemblage of tiny bonded particles. The model parameters are carefully calibrated according to laboratory observation of a realistic reference material. The simulations demonstrate that the compressive resistance of the bond largely depends on bond slenderness and boundary curvature as well as the bond contact area. The combined effect of three size parameters can be captured in a single formula. Given the bond contact area in common, a thin bond between large particles tends to fail at higher compressive force than a thick bond between small particles because the coalescence of micro-cracks inside the bond is hindered more effectively in the thin case, resulting in ultimate failure due to compressive crushing rather than tensile cracking. A full consideration of the size effect on the bond contact strength may change the picture of progressive bond breakage in cemented geomaterials, which deserves further investigation once a size-dependent bond contact law is obtained.

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“…Because the stress distribution inside a bond is oversimplified, which in reality can be extremely complex , shortcomings in these criteria are obvious: bond geometry effects are not considered; compressive bond failure is usually ignored; and the normal force dependence of shear and rolling strengths (and torsion strength in three‐dimensional (3D) DEM) of a bond and their coupling is not well captured. All these aspects had been experimentally found to be significant .…”

Section: Introductionmentioning

confidence: 98%

“…In the authors' team, bond failure was studied in a series of two‐dimensional (2D) experiments on bonded aluminum rod doublets under various loading modes . The experimental results have been incorporated into a bond failure criterion to remedy the aforementioned shortcomings, thus leading to more realistic 2D DEM simulations .…”

Section: Introductionmentioning

confidence: 99%

Numerical study of inter‐particle bond failure by 3D discrete element method

Shen

Jiang

Wan

2015

Num Anal Meth Geomechanics

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The cohesive-frictional nature of cementitious geomaterials raises great interest in the discrete element method (DEM) simulation of their mechanical behavior, where a proper bond failure criterion is usually required. In this paper, the failure of bond material between two spheres was investigated numerically using DEM that can easily reproduce the failure process of brittle material. In the DEM simulations, a bondedgrain system (composed of two particles and bond material in between) was discretized as a cylindrical assembly of very fine particles connecting two large end spheres. Then, the bonded-grain system was subjected to compression/tension, shear, rolling and torsion loadings and their combinations until overall failure (peak state) was reached. Bonded-grain systems with various sizes were employed to investigate bond geometry effects. The numerical results show that the compression strength is highly affected by bond geometry, with the tensile strength being dependent to a lesser degree. The shear, rolling and torsion strengths are all normal force dependent; i.e., with an increase in the normal force, these strengths first increase at a declining rate and then start to decrease upon the normal force exceeding a critical value. The combined actions of shear force, rolling moment and torque lead to a spherical failure envelope in a normalized loading space. The fitted bond geometry factors and bond failure envelopes obtained numerically in this three-dimensional study are qualitatively consistent with those in previous two-dimensional experiments. The obtained bond failure criterion can be incorporated into a future bond contact model.where the three fitting parameters are C 1 = 1.444, C 2 = À0.702 and C 3 = 0.168. Figure 7 presents the 2D experimental results adapted from [44]. In Figure 7(a), the end particle size (D s ) in the experiments was fixed at 12 mm, whereas the 528 Z. SHEN, M. JIANG AND R. WAN compressive displacements as marked in Figure 8(a). The black lines represent compressive forces, and the red lines represent tensile forces (in the online version of this paper). Figure 8(b) shows that the bond material initially crushes at the periphery, and the crushed zone extends inward progressively. No force is transmitted through the crushed zone. Figure 8(c) presents similar observations in 2D experiments. Comparison with experiments.The outermost peripheral zone of the bond material is mechanically the weakest. The longer (in the normal direction) this zone is, the less overall compressive force it can bear because of the increased susceptibility to lateral buckling. The buckling itself is a result of the complex stress distribution within the bond material. See more details on this issue in [36] where FEM was used to visualize the stress fields at a bond contact. This buckling mechanism can explain the end shape and slenderness effects to be discussed below. 3.1.3.2. End shape. The nondimensional quantity D s /D b characterizes the end shape of the bond material. A smaller D s /D b means that...

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A bond failure criterion for DEM simulations of cemented geomaterials considering variable bond thickness

Cited by 26 publications

References 63 publications

A simple three‐dimensional distinct element modeling of the mechanical behavior of bonded sands

A simple three‐dimensional distinct element modeling of the mechanical behavior of bonded sands

On the size-dependent compressive resistance of bonded granules

Numerical study of inter‐particle bond failure by 3D discrete element method

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