• Journal of the Korean Geotechnical Society
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• v.38 no.10
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• pp.31-40
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• 2022

This study compares elastic moduli calculated using two stiffness testing methods with different strain ranges to evaluate the stress-settlement characteristics of foundation support layers. Elastic moduli were calculated by the soil stiffness gauge (SSG) in the micro-strain range and the plate load test (PLT) in the medium strain range. To apply the elastic moduli obtained by the two testing methods with different strain ranges to the design and construction of foundation soils, the correlation between each measurement value should be identified in advance. As a result of the comparative analysis of the elastic moduli calculated using the two methods in weathered soil and rock, which are representative support layers in Korea, the calculated elastic moduli differed depending on the types of soil and stress conditions. For various soil types, the static elastic modulus obtained by the PLT was reduced by 56% because of the difference in the strain level of the test compared with the dynamic elastic modulus obtained by the SSG. Therefore, the results show that it is necessary to apply corrections to the stress distribution, stress level, and dynamic effect according to the ground stiffness to effectively use the SSG instead of the PLT.

• Structural Engineering and Mechanics
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• v.13 no.3
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• pp.329-343
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• 2002

In this research, the dynamic stability of an orthotropic elastic conical shell, with elasticity moduli and density varying in the thickness direction, subject to a uniform external pressure which is a power function of time, has been studied. After giving the fundamental relations, the dynamic stability and compatibility equations of a nonhomogeneous elastic orthotropic conical shell, subject to a uniform external pressure, have been derived. Applying Galerkin's method, these equations have been transformed to a pair of time dependent differential equations with variable coefficients. These differential equations are solved using the method given by Sachenkov and Baktieva (1978). Thus, general formulas have been obtained for the dynamic and static critical external pressures and the pertinent wave numbers, critical time, critical pressure impulse and dynamic factor. Finally, carrying out some computations, the effects of the nonhomogeneity, the loading speed, the variation of the semi-vertex angle and the power of time in the external pressure expression on the critical parameters have been studied.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.175-183
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• 1999

Recently, problems related to vibrations of decomposed granite soils have acquired increasing attention in Korea because those soils cover approximately one third of the country. Both resonant column and cyclic triaxial test were performed to investigate deformation characteristics of unsaturated and cement-mixed decomposed granite soils in Suwon region. The important soil parameters in this respect are the shear moduli, dynamic moduli of elasticity and damping ratios. The dynamic parameters are influenced by variables such as strain amplitude, ratio of loading cycles, and degree of saturations, etc. Test results and data have shown that the optimum degree of saturation to the maximum shear modulus due to a capillary menisci effect was about 17~18 % at low strain amplitude and 10~15 % at intermediate strain amplitude. This paper suggests the range of threshold strain and mean shear modulus of decomposed granite soils in Suwon region. It also proposed the empirical relationship between the dynamic parameters for cement-mixed and non-mixed decomposed granite soils.

• International Journal of Highway Engineering
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• v.17 no.3
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• pp.35-47
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• 2015

PURPOSES : A tack coat has been utilized to increase the bond performance between the surface layer and base course (intermediate course) at various road pavement sites. This is similarly true in other nations. Based on this connection, the objective of the present study is to evaluate the properties of hot mix asphalt (HMA) mixtures with an RSC-4 or BD-Coat and determine the application rate of the tack coat. METHODS : The HMA specimens were manufactured using superpave gyratory compaction. The HMA mixtures were composed of a 5-cm thick surface layer and a 10-cm thick base course. An impact hammer resonance test (IHRT) and a static load shear test were conducted to evaluate the performance of the HMA mixtures with a tack coat. From these tests, the dynamic moduli related to the high-frequency resistance and interlayer shear strength (ISS) of HMA could be obtained. RESULTS : The results of the dynamic moduli of HMA are discussed based on the resonance frequency (RF). To check the accuracy of the IHRT, we conducted a coherence analysis. A direct shear test using the application of a static load test was carried out to evaluate the interlayer shear strength (ISS) of HMA. CONCLUSIONS : The maximum ISS was demonstrated at an RSC-4 application rate of 462 gsm, and the maximum dynamic modulus was demonstrated at an RSC-4 application rate of 306 gsm. By averaging the results of the ISS, the maximum ISS values were obtained when a BD-Coat application rate of 602 gsm was applied.

• Magazine of the Korea Concrete Institute
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• v.8 no.5
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• pp.123-133
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• 1996

Recently, the construction of infrastructures has been booming and accelerating to keep up with rapid economic growth. Construction activities and operation of transportation facilities cause unfavorable effects such as civil petitions associated with vibration-induced damages or nuisances. Accordingly, the objective of this study is to develop vibration-controlled concrete using various vibration-controlled mixtures, and also to recycle obsolete materials in part. As the first step to achieve this research, preliminary mix designs have been carried out to obtain an appropriate mix proportion above 200kg/$\textrm{cm}^2$ in uniaxial compressive strength. Test specimen based on the mix proportion selected have been actuated by the impact hammer to investigate their dynamic characteristics. Vibration-controlled mixtures are foam, latex, rubber powder and plastic resin, which have been determined to reduce a vibration by and large. KS F2437 and travel time method have been used to figure out 1st natural frequency and dynamic elastic moduli. Damping ratios have been computed by adopting the polynomial curvefitting method and the geometric analysis method on the frequency response spectrum curve. of which results have been compared and analyzed hereon.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.189-197
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• 2003

In this paper, deformation characteristics of fiber-mixed-soils were studied at small strain range(0.0001%～1%) using resonant column test and triaxial test, and reinforcement effect was evaluated by the measure of maximum shear moduli. The effects of the major parameters such as fiber content, aspect ratio and fiber type on reinforcement were comparatively assessed. The specimens were remolded from Jumunjin Sand randomly mixed with discrete polypropylene staple fibers. Maximum shear moduli of fiber-mixed-soils increased by up to 30% and modulus reduction was also restrained in nonlinear range. Shear moduli increased as the aspect ratio increases. The reinforcement was more effective with fibrillated fiber than with monofilament fiber. The most effective reinforcement was achieved with the specimen of 0.3 % fiber content.

• Proceedings of the Korean Society of Rheology Conference
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• 2006.06a
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• pp.119-122
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• 2006

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.180-185
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• 1996

Construction activities and operation of transportation facilities have caused unfavorable effects such as civil petitions associated with vibration-induced damages or nuisances. The objedtive of this research is to develop vibration-controlled concrete containing foams, latex, rubber powders, plastic resins and etc as a concrete mixture. As the first step to achieve this research, preliminary mix designs have been carried out to find out an appropriate mix proportion above 200kg/㎠ in uniaxial compressive strength, and investigate their dynamic mechanical characteristics such as dynamic elastic moduli, material damping ratio, Poisson's ratio, resonant frequency and etc.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2328-2339
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• 1992

The propagation of coherent time-harmonic elastic L-and SV-waves is studied in a medium with random distribution of cylindrical inclusions. The purpose of the research is to characterize the dynamic elastic moduli and the attenuation properties of fiber-reinforced composite materials. The cylindes representing the fibers are assumed to be distributed in parallel with each other and the direction of incident waves are normal to the cylinder axes. A multiple scattering formula using the single scattering coefficients in conjunction with the Lax's quasicrystalline approximation is derived from which the dispersion relation for such medium is obtained. In order to formulate the multiple scattering interaction between cylinders, the pair correlation functions are generated by the Monte Carlo simulation technique. From the numerically evaluated complex wavenumbers, the propagation speed of the average wave, the coherent attenuation and the effective elastic moduli are presented as functions of frequency and fiber volume fraction.

• Macromolecular Research
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• v.17 no.9
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• pp.658-665
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• 2009

This study examined the effects of the sodium salts of aliphatic dicarboxylic acids (DCAs) on the dynamic mechanical properties and morphology of two sets of poly(styrene-co-sodium methacrylate) (MNa) and poly(styrene-co-sodium styrenesulfonate) (SNa) ionomers. When the DCA content was relatively low, the ionic moduli of the MNa and SNa ionomers increased but the matrix and cluster glass transition temperature ($T_g$) did not change significantly. The increasing ionic modulus was almost independent of the type of the ionic groups of the ionomer, and the chain length of DCAs. When a large amount of the sodium succinate (DCA4) was added to the MNa and SNa ionomers, the ionic moduli of the two ionomers increased strongly but the matrix and cluster $T_g's$ increased slightly and significantly, respectively. In the case of sodium hexadecanedioate (DCA 16), DCA 16 increased the ionic moduli of the two ionomers. The addition of DCA16 changed the matrix and cluster $T_g's$ of the MNa ionomer slightly, but decreased the cluster $T_g$ of the SNa ionomer significantly with no change in the matrix $T_g$. In addition, the DCA-containing ionomers showed an X-ray diffraction peak indicating the presence of ordered domains of DC As in the ionomers. Hence, DCA4 acts mainly as a reinforcing filler in MNa and SNa systems. In the case of DCA 16, it initially behaved like a filler but also functioned as a preferential plasticizer for the clusters at high content.