• Explosives and Blasting
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• v.36 no.4
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• pp.16-25
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• 2018

In order to reduce ground vibration during tunnel excavation, a free surface blasting method has been applied in which a partial free surface is formed on the excavation surface and controlled blasting is performed. In this study, the ground vibration reduction due to artificial joints was evaluated by forming artificial joints on center cut using diamond wire saw and comparing the ground vibration caused by center cut blasting. As a result of comparison, ground vibration was reduced by artificial joints center cut blasting more than normal center cut blasting, and the ground vibration reduction effect of horizontal artificial joints center cut blasting was evaluated more than that of vertical artificial joint center cut blasting.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.721-728
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• 2000

The shear behavior of sawtoothed artificial joints grouted with cement milk was investigated in the laboratory under constant normal stress conditions. Tests were conducted on joints with asperities having inclinations of 16.7$^{\circ}$ and 26.6$^{\circ}$, compresive strengths having 15MPa and 47MPa under a given range of normal stresses varying from 0.76 to 1.91 MPa and at a free condition of pitching, rolling and dilatancy. Results show that the effect of asperities on shear strength increase is significant up to asperity height to grout thickness (t/a) ratio of 0.3∼1.0. Increase of cohesion is the main cause of shear strength increase in cement grouted sawtoothed artificial joints.

• Geomechanics and Engineering
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• v.31 no.4
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• pp.353-364
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• 2022

This study presents a hybrid algorithm for classifying the rock joints, where the improved artificial bee colony (IABC) and the fuzzy C-means (FCM) clustering algorithms are incorporated to take advantage of the artificial bee colony (ABC) algorithm by tuning the FCM clustering algorithm to obtain the more reasonable and stable result. A coefficient is proposed to reduce the amount of blind random searches and speed up convergence, thus achieving the goals of optimizing and improving the ABC algorithm. The results from the IABC algorithm are used as initial parameters in FCM to avoid falling to the local optimum in the local search, thus obtaining stable classifying results. Two validity indices are adopted to verify the rationality and practicability of the IABC-FCM algorithm in classifying the rock joints, and the optimal amount of joint sets is obtained based on the two validity indices. Two illustrative examples, i.e., the simulated rock joints data and the field-survey rock joints data, are used in the verification to check the feasibility and practicability in rock engineering for the proposed algorithm. The results show that the IABC-FCM algorithm could be applicable in classifying the rock joint sets.

• Explosives and Blasting
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• v.36 no.3
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• pp.1-9
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• 2018

This study was conducted to evaluate the influences of the angle of artificial joints, the distance between the artificial joints and the blast hole, and the number of artificial joints on the pressure wave propagation, crack propagation, and blast wave velocity. The evaluation was conducted numerically by use of the Euler-Lagrange solver supported by the AUTODYN, which is a dynamic FEM program. As a result, it was found that the blast wave velocity was decreased most rapidly as either the distance between the artificial joint and the blast hole was decreased or the angle of the artificial joint was increased. In contrast to the case of no artificial joint, the amount of attenuation of the blast wave velocity was considerably large when an artificial joint was present. However, the effect of the number of artificial joint on the attenuation of the blast wave velocity was negligible under the given condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1033-1039
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• 2012

Artificial joints are used when joints lose their function because of either the destruction or damage of the composing bones of the joints. To evaluate the primary stability of a femur-implant system, the relative displacement caused by a repeated load is measured immediately after the insertion of the artificial joint. For more accurate stability evaluation, the accurate measurement of the penetration displacement of the artificial joint to the bone and the rotation angle of the artificial joint is essential. In this study, to evaluate the primary stability of the femur-implant system, we propose a new relative displacement measurement method. By using this new method, we comparatively evaluate the primary stability for various surgical methods and the varying stiffness of the cadaver femur-implant itself.

• Tribology and Lubricants
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• v.13 no.1
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• pp.82-87
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• 1997

The modern orthopaedics frequently uses the total hip replacement in the artificial hip joint. The wear in this joint requires a re-replacement of hip joints because it is under the severe load and friction conditions. To solve these problems the previous studies have been mainly focussed on the development of new materials. The research of new materials, however, needs much time and effort since it should be experimented for its bio-compatibility, friction, and wear characteristics. To reduce the work, in this study, the finite element analysis is applied to find new combinations of bio-materials in the total hip replacement which has the excellent contact characteristics. A non-linear FEM program MARC with 5-node axisymmetric element was used for analyzing the contact stresses between the hip joints. The computed results show that in case of acetabulum UHMWP has good characteristics, in femoral head, $Al_2O_3$, and in stem, Ti6Al4V.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.265-270
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• 2000

AESTRACI: The shmr behior of sawtoothed artrjicial joints grouted with cement milk rm investiguted in the lahotconstant normal stress conditions. Tests were amducted on joints with asperities h i n g inclinations cf 16.7" and 26.6" ,strengths h i n g 15MPa and 47MPa under a given nmge of n o d stresses wrying frcm 0.76 to 1.g MPa md at a freepitching, rolling and dihtmuy. Results show that the gect of asperities on shmr strength increme is signifamt up to as,to grout thidness (t/a) mtio 4 0.3-1.0. Increme of ahesim is the nmn muse cf shmr strength increme in cemmtoothed artificial iointsed artificial ioints

• Journal of Biomedical Engineering Research
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• v.22 no.6
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• pp.519-526
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• 2001

At present. about 0.3 million and more THRs (Total Hip Replacement) in a rear are being done worldwide. The increase in mechanical failure with the increase in THR, required more revisions. Revisions compensate mainly the wear of the artificial joint frictional surface and the loosening of the cup and stem. According to recent researches, loosening is mainly due to wear debris UHMWPE (Ultra High Molecular Weight Polyethylene) from frictional surfaces . To overcome the wear problems associated with artificial joint materials , new surface structures with regular Patterns were designed and fabricated The lubrication Properties were examined to evaluate the wear of the frictional surfaces. The surface structure manifested a Pattern of "dents" with a 0.2-1.0 mm of diameter and 0.6-2.0 mm of Pitch. From the friction test of the SUS316L vs UHMWPE using the frictional tester, we found that the lubrication Performance was improved due to of drastically reduced amount of abrasion. There were optimum sizes for the diameter and the pitch of the Pattern. The results demonstrated that the lubrication properties could be improved by Patterning of the frictional surfaces. The surface Patterning was effective in preventing wear of the frictional surfaces, and the life of an artificial joint could be extended with such Patterning.

• Tunnel and Underground Space
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• v.7 no.2
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• pp.108-115
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• 1997

Uniaxial and biaxial compressive tests were conducted on limestone specimens containing artificial joints and a circular hole to investigate the influence of inclination and number of joints on compressive strength and deformation behavior of rock with a circular hole. Under uniaxial and biaxial compressive condition, the inclination of joints showing the maximum and minimum strength were 0$^{\circ}$ and 30$^{\circ}$ respectively, which was independent of the number of joints. Under uniaxial compressive condition, relative maximum strength of rock with n=1 and 3 to intact rock with a circular hole were 12.5%~82.8% and 11.4~62.5% respectively, and under biaxial compressive condition, 18.2~91.0% and 17.0~87.5% respectively. The influence of the number of joints on the decrease of compressive strength was greater under uniaxial than under biaxial compressive condition. Under uniaxial and biaxial compressive condition, axial and lateral deformations of rock showed the least values where $\alpha$=30$^{\circ}$. Under uniaxial compressive condition, axial and lateral deformation at maximum strength of rock have the increasing tendency with increase the number of joints. But they have the decreasing tendency under biaxial compressive condition. Under uniaxial and biaxial compressive conditions, axial deformation of circular hole was greater than lateral deformation without respect to the number of joints and the inclination of joints.

• Geomechanics and Engineering
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• v.12 no.4
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• pp.723-738
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• 2017

Rock is a heterogeneous material, which introduces complexity in the analysis of rock slopes, since both the existing discontinuities within the rock mass and the intact rock contribute to the degradation of strength. Rock failure is often catastrophic due to the brittle nature of the material, involving the sliding along structural planes and the fracturing of rock bridge. This paper proposes an advanced discretization method of rock mass based on block theory. An in-house software, GeoSMA-3D, has been developed to generate the discrete fracture network (DFN) model, considering both measured and artificial joints. Measured joints are obtained from the photogrammetry analysis on the excavation face. Statistical tools then facilitate to derive artificial joints within the rock mass. Key blocks are searched to provide guidance on potential reinforcement measures. The discretized blocky system is subsequently implemented into a discontinuous deformation analysis (DDA) code. Strength reduction technique is employed to analyze the stability of the slope, where the factor of safety can be obtained once excessive deformation of slope profile is observed. The combined analysis approach also provides the failure mode, which can be used to guide the choice of strengthening strategy if needed. Finally, an illustrated example is presented for the analysis of a rock slope of 20 m height inclined at $60^{\circ}$ using combined GeoSMA-3D and DDA calculation.