• Journal of the Korean Geotechnical Society
• /
• v.18 no.4
• /
• pp.137-146
• /
• 2002

Geomembrane, compacted clay liner, and geosynthetic clay liner (GCL) are widely used to prevent leachate from leaking to adjacent geo-environment at a municipal solid waste (MSW) landfill. Interface shear strength between GCL and geomembrane installed at a landfill side slope is important properties for the safe design of side liner or final cover systems. The interface shear strength between two geosynthetics was estimated by a large direct shear test in this study. The shear strength was evaluated by the Mohr-Coulomb failure criterion. The effects of normal stress, hydration or dry condition, and a hydration method were investigated. The test results show that the interface shear strength and shear behavior varied depending up on the level of normal stress, the type of geosynthetic combinations, and a hydration method. When GCLs were sheared after being hydrated under 6kPa loading, the results were consistent with those published by other researchers. Summaries of friction angles, normal stress and hydration condition is presented. These friction angles could be used as a reference value at a site where similar geosynthetics are installed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.35 no.4
• /
• pp.769-777
• /
• 2015

In this study, the rheological models were introduced and developed to reflect rate dependent tensile behaviour of concrete. In general, mechanical properties(e.g. strength, elasticity, and fracture energy) of concrete are increased under high loading rates. The strength of concrete shows high rate dependency among its mechanical properties, and the tensile strength has higher rate dependency than the compressional strength. To simulate the rate dependency of concrete, original spring set of RBSN(Rigid-Body- Spring-Network) model was adjusted with viscous and friction units(e.g. dashpot and Coulomb friction component). Three types of models( 1) visco-elastic, 2) visco-plastic, and 3) visco-elasto- plastic damage models) are considered, and the constitutive relationships for the models are derived. For validation purpose, direct tensile test were simulated, and characteristics of the three different rheological models were compared with experimental stress-strain responses. Simulation result of the developed visco-elasto-plastic damage(VEPD) model demonstrated well describing and fitting with experimental results.

• Tunnel and Underground Space
• /
• v.26 no.2
• /
• pp.100-109
• /
• 2016

This study suggests three spatial distribution functions of strength parameters, which can be adopted in the derivation of failure conditions for transversely isotropic rocks. All three proposed functions, which are the oblate spheroidal function, the exponential function, and the function based on the directional projection of the strength parameter tensor, consist of two model parameters. With assumption that the cohesion and friction angle can be described by the proposed distribution functions, the transversely isotropic Mohr-Coulomb criterion is formulated and used as a failure condition in the simulation of the conventional triaxial tests. The simulation results confirm that the failure criteria incorporating the proposed distribution functions could reproduce the general trend in the variations of the axial stress at failure and the directions of failure planes with varying inclination of the weankness planes and confining pressure. Among three distribution functions, the function based on the directional projection of the strength parameter tensor yields the highest axial strength, while the axial strength estimated by the oblate spheroidal distribution function is the lowest.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.4
• /
• pp.1281-1293
• /
• 2013

A sophisticated finite element model is illustrated to analyze the behavior of Prefabricated Parallel Wire Strand(PPWS) sockets for main cables of suspension bridges. An orthotropic model is proposed for the casting material by considering both effects of individual wires and a casting alloy, and the contact between surfaces of a socket and a casting alloy is idealized by using the Coulomb friction and the surface-based contact model. The proposed FE model is verified by comparing the strain distributions obtained from the tensile test and FE analysis. The mechanical behavior of a socket is investigated with respect to the variation of the frictional coefficient. The result shows that the friction between surfaces significantly diminishes the stress concentration of a socket and a casting alloy, and the normal stress from the design equation represents the averaged value of the upper and lower quartiles in the distribution of contact stresses between a socket and a casting alloy.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.1
• /
• pp.63-72
• /
• 2006

Coulomb's theory has traditionally been used for the estimation of active earth pressure acting on rigid walls. However, many experimental data show that active earth pressures on rough, rigid walls are nonlinearly distributed. This is due to the arching effects produced by friction between the wall and backfill materials when the wall translates away from the backfill. Although there are analyses that take arching into consideration f3r a horizontal backfill surface and a vertical rigid wall, these analyses were derived for homogeneous backfill. Therefore, it is not possible to use these analyses for a caisson backfilled with crushed rock and sand, a common type of rigid wall for harbor structures. In this study, a new formulation for calculation of the nonlinear active earth pressure acting on a caisson backfilled with crushed rock and sand is proposed considering both internal friction angles and unit weights of the crushed rock and sand.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.11
• /
• pp.91-100
• /
• 2008

This study proposes the equations evaluating the shear strength of cemented sand by analytical interpretation based on Mohr-Coulomb failure criteria, and verifies them using the results of triaxial and unconfined compression tests. The internal friction angle of cemented sand is identical to that of uncemented one regardless of the stress level, while the cohesion intercept of cemented sand is constant before the breakage of cementation bonds. Therefore, the shear strength of cemented sand can be represented as a summation of the shear strength of uncemented sand and the unconfined compressive strength of cemented sand. In addition, the cohesion intercept of cemented specimen can be expressed as a function of unconfined compressive strength and friction angle. In the transition zone, assuming a constant shear strength, the equations to evaluate shear strength and cohesion intercept of cemented sand are also represented. It is observed that the predicted values using these solutions agree well with the experimental results. The experimental results also show a linear relationship between the unconfined compressive strength and the breaking point of cementation bonds.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.12
• /
• pp.128-141
• /
• 1998

We propose the robust nonlinear controller design methodology for the multivariable system which has hard nonlinearities (Coulomb friction, dead-zone, etc) and the structured real parameter uncertainty. The hard nonlinearity can be linearized by the RIDF technique and structured real parameter uncertainty can be modelled as the sense of Peterson-Hollot's quadratic Lyapunov bound. For this system, we apply the robust QLQG/H$_{\infty}$ control and then can obtain four Riccati equations. Because of the system's nonlinearity, however, one Riccati equation contains the nonlinear correction term that is very difficult to solve numerically, In order to treat this problem, using some transformations to Riccati equations, the nonlinear correction term can be eliminated. Then, only two Riccati equations need to design a controller. Finally, the robust nonlinear controller is synthesized via IRIDF techniques. To test this proposed control method, we consider the direct-drive robot manipulator system that has Coulomb frictions and varying inertia.

• Computers and Concrete
• /
• v.31 no.4
• /
• pp.307-314
• /
• 2023

In this paper we back-analyze a failure event of a 9 m high concrete cantilever wall subjected to earth loading. Granular soil was deposited into the space between the wall and a nearby rock slope. The wall segments were not designed to carry lateral earth loading and collapsed due to excessive bending. As many geotechnical programs rely on the Mohr-Coulomb (MC) criterion for elastoplastic analysis, it is useful to apply this failure criterion to the concrete material. Accordingly, the back-analysis is aimed to search for the suitable MC parameters of the concrete. For this study, we propose a methodology for accelerating the back-analysis task by automating the numerical modeling procedure and applying a machine-learning (ML) analysis on FE model results. Through this analysis it is found that the residual cohesion and friction angle have a highly significant impact on model results. Compared to traditional back-analysis studies where good agreement between model and reality are deemed successful based on a limited number of models, the current ML analysis demonstrate that a range of possible combinations of parameters can yield similar results. The proposed methodology can be modified for similar calibration and back-analysis tasks.

• Journal of the Korean Society for Railway
• /
• v.19 no.6
• /
• pp.765-776
• /
• 2016

In this study, a standard section of a railway bridge abutment wall was designed to satisfy the external stability condition in accordance with the design criteria; this design was used to compare and analyze the active earth pressure and to calculate various types of earth pressure acting on the virtual back (wall, plane) according to the frictional angle of the backfill materials. Also, the external stability, member force and construction cost were analyzed according to the frictional angle of the backfill materials using various theories of earth pressure such as Rankine, Coulomb, Trial Wedge, and Improved Trial Wedge. As for the results, it was found that lateral earth pressure at the virtual back plane was higher than at the virtual back wall, and that these values decreased with the increase of the frictional angle of the backfill materials. The increasing of the frictional angle of the backfill materials decreased the active earth pressure (according to Rankine, Coulomb, Trial Wedge, and Improved Trial Wedge results), and the member force as well as the construction cost were reduced.

• Journal of the Korea Concrete Institute
• /
• v.13 no.3
• /
• pp.221-227
• /
• 2001

Both strength and stiffness of RC structures strengthened by a steel plate greatly increase and however, their ductility might not be sufficient because premature failures usually occur at the adhesive-concrete interface. In this study, Mohr-Coulomb criterion was adopted to examine the bonding failure mechanism, and the diagonal shear bonding test, the direct shear bonding test, and the flexural test on RC beams strengthened by a steel plate were carried out to measure the bonding properties. It is found from the experimental and numerical results that the cohesive strengths of epoxy-concrete interfaces are ranging from 50 kgf/㎠ to 70 kgf/㎠ when the friction angle is 45°. Bonding failure loads can be predicted by applying the bonding properties to the structural analysis of RC beams strengthened by steel plate. By considering them in the design of strengthened beams, the premature failure would be effectively prevented.