• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.1-12
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• 2011

In order to analyze the influence of particle bonding and crushing on the characteristics of shear behavior, especially residual shear behavior of granular soil, ring shear test was simulated by using DEM(Discrete Element Method)-based software program PFC(Particle Flow Code). Total four models including two non-crushing models and two crushing models were created in this study by using clump or cluster model built in PFC. The applicability of Lobo-crushing model proposed by Lobo-Guerrero and Vallejo(2005) was investigated. In addition, the results of ring shear test were analyzed and compared with those of direct shear test. The results showed that the modelling of ring shear test should be conducted to investigate the residual shear behavior. The Lobo-crushing model cannot be applied to investigate the residual shear strength. Finally, it can be concluded that the numerical models excluding Lobo-crushing model suggested in this study can be used extensively for other studies concerning the residual shear behavior of granular soil including soil crushing.

• Geomechanics and Engineering
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• v.35 no.2
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• pp.209-219
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• 2023

This paper presents numerical investigations into the particle crushing effect on the shear properties of gravel under direct shear condition. A novel particle crushing model was developed based on the octahedral shear stress criterion and fragment replacement method. A series of direct shear tests were carried out on unbreakable particles and breakable particles with different strengths. The evolutions of the particle crushing, shear strength, volumetric strain behavior, and contact force fabric during shearing were analyzed. It was observed that the number of crushed particles increased with the increase of the shear displacement and axial pressure and decreased with the particle strength increasing. Moreover, the shear strength and volume dilatancy were obviously decreased with particle crushing. The shear displacement of particles starting to crush was close to that corresponding to the peak shear stress got. Besides, the shear-hardening behavior was obviously affected by the number of crushed particles. A microanalysis showed that due to particle crushing, the contact forces and anisotropy decreased. The mechanism of the particle crushing effect on the shear strength was further clarified in terms of the particle friction and interlock.

• Geomechanics and Engineering
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• v.5 no.3
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• pp.241-261
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• 2013

The bearing mechanism of pile during installation and loading process which controls the deformation and distribution of strain and stress in the soil surrounding pile tip is complex and full of much uncertainty. It is pointed out that particle crushing occurs in significant stress concentrated region such as the area surrounding pile tip. The solution to this problem requires the understanding and modeling of the mechanical behavior of granular soil under high pressures. This study aims to investigate the sand behavior around pile tip considering the characteristics of sand crushing. The numerical analysis of model pile loading test under different surcharge pressure with constitutive model for sand crushing is presented. This constitutive model is capable of predicting the dilatancy of soil from negative to positive under low confining pressure and only negative dilatancy under high confining pressure. The predicted relationships between the normalized bearing stress and normalized displacement are agreeable with the experimental results during the entire loading process. It is estimated from numerical results that the vertical stress beneath pile tip is up to 20 MPa which is large enough to cause sand to be crushed. The predicted distribution area of volumetric strain represents that the distributed area shaped wedge for volumetric contraction is beneath pile tip and distributed area for volumetric expansion is near the pile shaft. It is demonstrated that the finite element formulation incorporating a constitutive model for sand with crushing is capable of producing reasonable results for the pile loading problem.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.325-328
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• 2004

This paper deals with void crushing behavior by ingot forging process which consists of sequential operations of upset forging and bloom forging. The predicted results of void crushing behavior by the simplified global-local method using F.E. analysis showed that the inherent void at the top region of the ingots remains incompletely crushed even after several forging operations. From the results of the hot upset forging test using the billets with drilled voids, it was found that the bonding efficiency of the void after forging process increases with an increase in deformation, and a decrease of initial diameter of voids.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.169-176
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• 2002

Axial crushing behavior of cylindrical shell Is utilized in the braking of the high-velocity impacting object. In this paper, truncated cone shape brake device is introduced. That is, thickness of the shell is increased gradually from the impacting end to the other end. A detailed experimental investigation on the quasi-static axial crushing behavior of truncated cone type brake devices has been performed. Specimens of various shape were tested to check the influence of design parameters such as length, radius, mean thickness, and conical angle of cylinder. Influence of the material properties were also investigated by adopting aluminum, low carbon steel, and stainless steel as constructing materials. By analyzing deformation procedures of the specimens, it is seen that conical angle influence the deformation mode and the sequence of the wrinkles generation. Braking distance and mean braking force of each specimen were predicted based on the crushing load measured from the tests.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.314-323
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• 2010

Recently, granular soils having a large particle size are frequently used as a filling material in the construction of foundation, harbor, dam, and so on. The shear behavior of this granular soil plays a key role in the stability of structures. For example, soil particle crushing occurring at the interface between structure and soil and/or within soil mass can cause the disturbance of ground characteristics and consequently induce an issues in respect of stability of structures. In order to investigate the shear behavior according to an existence and nonexistence of particle crushing, numerical analyses were conducted by using the DEM(Discrete Element Method)-based software program PFC(Particle Flow Code). Using the crushing model and non-crushing model which were created in this study, numerical analyses of ring shear test were conducted and their results were analyzed and compared. In general, landslide and slope stability are accompanied by a large displacement and consequently not only a peak strength but also a residual strength are very important in the analysis of landslide and slope stability. However the direct shear test which has been commonly used in the determination of shear strength parameters has a limitation on displacement therefore the residual strength parameters can not be obtained. The characteristics of residual shear behavior were investigated through the numerical analyses in this study.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.41-53
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• 2009

In order to analyze the influence of particle shape on evolution of particle crushing and characteristic of shear behavior of granular soil, direct shear test was simulated by using DEM (Discrete Element Method). Six particle shapes were generated by clump and cluster model built in PFC (Particle Flow Code). The results of direct shear test for six particle shapes were compared and analyzed with those for circular particle shape. The results of numerical tests showed a good agreement with those of experimental tests, thus the appropriateness of numerical modelling set in this study was proved. As for particle shape, more angular and rougher particle induced larger internal friction angle and more particle crushing than relatively round and smooth particle. When particles were crushed, crushing was concentrated on the shear band adjacent to the shear plane. Finally, it can be concluded that the numerical models suggested in this study can be used extensively for other studies concerning the shear behavior of granular soil including soil crushing.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.136-145
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• 2009

Factors influencing shear behavior of granular material include particle size, shape, distribution, relative density, particle crushing, etc. In this study, these factors are characterized by viewpoint of shear behavior using numerical analysis based on DEM. Geometrical particle shape is represented by a combination of small circular particles and influence of particle shape on crushing is studied through relative comparisons between clump (uncrushable) and cluster (crushable) models which are modeled using DEM. Also, particle shape is quantified by the dimensionless parameters such as circularity and convexity. The results indicate that particle shape indexes have a negative association with internal friction angle. Also, internal friction angle becomes reduced and failure envelop curve becomes nonlinear due to the particle crushing. It is also found that numerical results are quite good agreement with the experimental test conducted in this study.

• Journal of Hydrospace Technology
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• v.2 no.1
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• pp.27-40
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• 1996

The prediction of the crushing strength and corresponding energy dissipation of unstiffened and stiffened plates under axial compression is discussed. Semi-empirical formulae for the crushing strength and dissipation energy of these stiffened plates are derived from the assesment of the structural behavior of unstiffened and stiffened box columns consisted of rectangular plates with longitudinal, transverse and orthogonal stiffeners. To demonstrate the effectiveness of proposed formulae, they are compared with the existing formulae and experimental results, which are shown in good agreements.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.4
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• pp.321-336
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• 2012

The shear behavior at the particle/surface interface such as rock joint can determine the mechanical behavior of whole structure. Therefore, a fundamental understanding of the mechanisms governing its behavior and accurately estimation of the interface strength is essential. In this paper, PFC, a numerical analysis program of discrete element method was used to investigate the effects of the surface roughness crushing on interface strength. The surface roughness was characterized by smooth, intermediate, and rough surface, respectively. Particle shape was classified into one ball model of circular shape and 3 ball model of triangular shape. The surface shape was modelled by wall model of non-crushing surface and ball model of crushing surface. The results showed that as the bonding strength of ball model decreases, lower interface strength is induced. After the surface roughness crushing was occurred, the interface strength tended to converge and higher bonding strength induced lower surface roughness crushing. Higher friction angle was induced in wall model and higher surface roughness induced the higher friction angle. From these findings, it is verified that the surface roughness and surface roughness crushing effect on the particle/surface interface shear behavior.