• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.61-68
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• 2008

Resilient modulus has been used for characterizing the stress-strain behavior of subgrade soils subjected to traffic loadings. With the recent release of the M-E Design Guide, highway agencies are further encouraged to implement the resilient modulus test to improve subgrade design. The subgrade design for the trackbed, however, is primarily relying on the static test results such as $K_{30}$ and deformation modulus, Ev. Therefore applicability of the resilient modulus for the design of trackbed needs to be evaluated. In this study, physical property tests, unconfined compressive tests and resilient modulus tests were conducted to assess the resilient and permanent strain behavior of 14 cohesive subgrade soils. A predictive model for estimating the resilient modulus is proposed based on the results of unconfined compressive tests and tangent elastic modulus, unconfined compressive strength, failure strain, secant modulus at peak, and yield strain. The predicted resilient moduli using the predictive models compared satisfactorily with measured ones. Although the permanent strain occurs during the resilient modulus test, the permanent behavior of subgrade soils is currently not taken into consideration.

• Geotechnical Engineering
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• v.10 no.2
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• pp.5-24
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• 1994

Resilient modulus tests were performed on five cohesive soils sampled from in -service subgrades and three cohesive soils compacted in the laboratory. It was concluded that in service resilient modulus can not be estimated from the resilient modulus of laboratory specimen compacted at same water content and dry density as in -service condition. The stress at 1 percent axial strain in unconfined compression tests ($Su_{1.0%}$) was found as a good indicator of the resilient modules ($M_R$), and the unique relationship between MR and $Su_{1.0%}$ was obtained. This relationship for the laboratory compacted soil is slightly different from that for the field compacted soil and the difference is less pronounced at the confining stress level expected to exist in subgrade. A proposed relationship itself is not affected by the changes in subgrade after construction and, therefore, it is applicable to as compacted and in service subgrade conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.229-236
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• 2015

In this study, the resilient modulus test and Light Weight Deflectormeter (LWD) test were conducted to simulate the moving vehicle load for the evaluation of the internal failure of epoxy asphalt pavement. The Measured displacement in the resilient modulus test of epoxy asphalt concrete showed very little residual deformation under repeated loads unlike the conventional asphalt. Therefore, the test results were evaluated as a normal state due to its similarity with elastic deformation. The deflection results from the resilient modulus tests were converted to the surface deflection modulus and the normal range of surface deflection modulus was estimated applying LWD measurement of 1 SIGMA level. Internal failure of pavements were estimated using the suspicious failure range at $60^{\circ}C$ and hysteresis. Internal moisture penetration and a decrease in bonding were observed in partial areas at $140{\mu}m$ of surface deflection. However, the areas showed inflection points in the hysteresis. Field investigation by suggested criterion indicated a high degree of accuracy.

• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.257-262
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• 2008

Design and analysis of road subgrade system, which is exposed to repetitive loading condition, uses resilient modulus. The behavior of railway subgrade system will not be quite different from that of road system. Following this phenomenological feature of the subgrade system, this paper introduces the implementation of the resilient modulus based constitutive model on a commercial finite element software. The implementation of the resilient modulus models such as K-${\theta}$ and Uzan on a FE program has been conducted previously. These model assumes that the material state reaches to the nonlinear elastic condition and with further application of repetitive loads, the response of material is completed in elastic condition. According to the recent test results performed on cohesive subgrade soils, however, permanent deformation occurs with repetitive loads. With aids of previously suggested models the permanent deformation cannot be modeled. To overcome such limitation a plastic potential derived from the test results and simple failure criterion based constitutive model is developed. The comparison between the analysis and test results shows a good correlation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.69-78
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• 1993

A testing system has been developed to evaluate the seasonal variation of the resilient modulus of granular subgrade soils. Two sites were successfully instrumented with soil moisture-temperature cells to monitor over a period of one year, the field temperature and moisture content underneath the pavement. Multiple regression equations were developed to determine the resilient modulus under environmental conditions. It is noted that the use of the effective resilient modulus at the location of the Average Depth of Significant Stress (ADSS) provides a reasonable basis for determining subgrade properties. In addition, a theoretical model has been developed to predict the resilient modulus due to the change of temperature and moisture condition.

• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.415-422
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• 2014

Reinforced trackbeds are an important layer that has a significant effect on the deformation of the track, therefore, a deeper understanding of reinforced trackbeds is necessary. In this paper, we conduct a large triaxial test in order to evaluate the resilient modulus ($M_R$) of reinforced trackbed materials through considering several factors such as the grain size distribution (GSD) and loading conditions. It is identified that the maximum size of the particle, GSD, and compacted water content affect the $M_R$ but the loading frequency does not. Because these tests are performed with consideration of the field environment, the test results are useful for analyzing tracks including reinforced trackbeds. The data are limited to evaluating the parameters of $M_R$ model; however the parameters of the deviatoric and bulk stress models that can be used in various loading conditions are proposed.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.133-140
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• 2021

There are few attempts to estimate the strength and stiffness of controlled low strength material (CLSM) using existing field-testing methods. The objective of this study is to evaluate the resilient modulus of CLSM by using the Light Weight Deflectometer (LWD) and investigate the relationships between the resilient modulus from LWD and the unconfined compressive strength (UCS) and secant modulus of elasticity from unconfined compressive test. Five CLSMs with different mix designs are used to evaluate the flowability and the stiffening of the CLSM in the flow and Vicat needle tests, respectively. To evaluate the early strength and stiffness characteristics, unconfined compressive tests are performed using the CLSM specimens cured for 1 and 7 days. LWD tests are carried out to estimate the resilient modulus of the CLSM specimens. The experimental results show that for the curing time of 1 day, the UCS and secant modulus of elasticity generally increase with the fast setting mortar content (FC). The CLSM specimen with the highest FC shows the significant increase in the UCS and secant modulus of elasticity along the curing time. Overall, the resilient modulus for the curing time of 1 day increases with the FC, while that for the curing time of 7days decreases with an increase in the FC. From the results, the linear relationships between the resilient modulus and UCS and secant modulus of elasticity are established.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.63-70
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• 2011

Expanded Polystyrene (EPS) is a type of geosynthetic material manufactured with various strengths, unit weights, and dimensions. Due to recent advances in research on EPS, the use of EPS has increased dramatically. This super light weight material has a unit weight of approximately $0.16{\sim}0.47kN/m^3$, equivalent to 6.3~15.7 of that of most natural soils with conditions of fill materials. In spite of this advantage, it is noted that no standard method of resilient modulus test on EPS geofoam was reported and no literature on resilient modulus test methods for EPS geofoam exist. The main object of this study was to investigate feasibility of the resilient modulus of EPS when it was applied for flexible pavement. The investigation of the feasibility was completed based on the results from triaxial tests.

• Journal of the Korean GEO-environmental Society
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• v.14 no.7
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• pp.51-56
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• 2013

Recently, a top record of hourly-based rainfall has been changed annually and flood damages of road have increased. To solve this problem, pavements for drainage were developed and practically constructed but there was no considerations on sub-base. In this research, we proposed standard for distribution of particle size of sub-base to consider strength characteristic and drainage property. We focused to compare coefficients strength and permeability by laboratory tests. Prior to tests, 4 samples were selected under the consideration on the international or domestic design guideline. In the tests, strength characteristics were compared with resilient modulus. Also, permeability characteristics were compared with coefficient of upward and downward permeability. Resilient modulus was determined with MR test using cyclic triaxial testing system. Two permeability tests were carried out. One is variable head permeability test for downward drainage and the other is Rowe Cell test for upward drainage. In the case of Rowe Cell test, middle-sized sampler with 150mm diameter was used for this study. Consequentially, we tried to find the optimum distribution of particle size to satisfy both of strength and permeability characteristics for sub-base.

• Journal of the Korean GEO-environmental Society
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• v.13 no.9
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• pp.61-68
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• 2012

The main objective of this study is to develop an analytical model for the resilient modulus of EPS geofoam when it is applied for flexible pavement as a subgrade material. This analytical model has been developed based on the results from triaxial compression tests. And this model can be used to analyze the flexible pavement structure using the finite element method by developing a program or modifying an existing program for any desired purposes. The results of this study show that the EPS geofoam as a replacement material for subgrade in flexible pavement is a feasible alternative to natural weak soils.