• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1152-1158
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• 2007

Although various fast and simple, testing devices have been developed in many countries such as the U.S, Japan, and European countries, these testing devices are not commonly used in Korea. In this study, compaction fur the field density test was carried out with a hand-guided vibrating roller. The results of the field density test were compared with those of the new testing devices such as the geogauge, soil impact hammer(CASPFOL), light falling weight deflectometer(LFWD), dynamic cone penetration(DCP). Regression analyses were conducted with the data from new testing devices. The analysis results showed that the correlation coefficients were high in the range of $70{\sim}95%$.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.636-643
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• 2008

The objective of this paper is to assess the potential use of the geogauge and the light falling weight deflectometer (LFWD) and the soil impact hammer as quality control/quality assurance $Q_C/Q_A$ devices for compacted soil layers. A comprehensive field experimental program considering variation of number of compaction, water contents and thickness of compaction layer was conducted on compacted layers of gravel sand. The geogauge, LFWD, the soil impact hammer and static load test (PLT) as a reference test were performed for the compacted layers. The geogauge elastic modulus, $E_G$, the LFWD dynamic modulus, ELFWD, empirical soil stiffness, $K_{30}$, obtained from soil impact hammer and soil stiffness directly obtained from PLT, $K_{30}$, were correlated with increasing number of compaction. The results of this study show that the geogauge, LFWD and the soil impact hammer, which are very simple to test, can be used as substituting devices for static PLT which is a conventional quality control/quality assurance $Q_C/Q_A$ devices for compacted soil layers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1373-1380
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• 2010

The plate loading test(PLT) and the field density test are mainly used on the construction of embankments to control the compaction of a limited layer thickness. These two test methods are very time consuming and inefficient, but they are still commonly used as the methods of quality control for soil compaction. In the last 3 decades, many devices such as geogauge, light falling weight deflectometer(LFWD) and dynamic cone penetrometer(DCP) etc., have been introduced into the engineering market with the objective of acquiring in situ stiffness properties of the compacted soil layers. Recently, a new type of sensor, called compactometer, which in mounted on the drum of a roller and measures impact forces continuously with GPS, called as Continuous Compaction Control(CCC), has come into use in many countries such as America, Germany, Japan and so on. The main objective of this paper is to assess the potential use of these new devices as quality control and assurance devices for compacted soil layers. Based on this study, compactometer and the LFWD results werestrongly correlated with the result obtained from the PLT and the field density test.

• Journal of the Korean GEO-environmental Society
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• v.19 no.2
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• pp.37-44
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• 2018

Ballasted track has been widely used due to its flexibility. However, the plastic deformation of ballasted track causes the evolution of track geometrical errors, and hence it requires continuous maintenance; increase in number of trains, weight, and speed expedites maintenance frequency and cost as well. Ballast stiffness is well-known as an indicator of design and maintenance. In this regard, this paper aims to suggest the method to measure ballast track stiffness using light-weight deflectometer (LWD) and thus verify its applicability as a maintenance measure. Preliminary field tests determined simple field testing protocol to measure track stiffness. The apparent ballast stiffness by LWD shows good corelation with TQI (Track Quality Index) and maintenance length. That is, as average of apparent stiffness increase, TQI and tamping length decrease exponentially. Therefore, apparent stiffness can be used as an index for ballast condition assessment.

• Journal of the Korean Society for Railway
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• v.18 no.1
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• pp.53-62
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• 2015

LWDT was developed for use as an alternative technique to measure the stiffness of trackbed soils. In this study, numerical and theoretical analyses of LWDT's acting mechanism were performed. The effectiveness of the adapted elastic formula used for calculation of the dynamic modulus, Evd, was investigated theoretically and also numerically by running ABAQUS analysis. The minimum thickness of the upper layer is proposed based on the analysis. Correction factors for the formula of elastic modulus are also proposed in this study. In the future, following field test results and laboratory mechanical tests such as the resonant column test, a guideline for the use of LWDT as a standard test protocol in track construction sites, as a measuring tool for the degree of compaction and/or stiffness and dynamic modulus, will be proposed based on this analysis.