• International Journal of Highway Engineering
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• v.11 no.2
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• pp.85-98
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• 2009

The in-situ Compaction test using sand cone (RC) and Plate Bearing Capacity Test (PBT) has been widely used for evaluating the subgrade and subbase condition on the pavement system. However, because the in-situ RC and PBT test are expensive and take plenties of time for operation, these are very difficult to figure out the in-situ characteristics of subgrade and subbase strength in detail. Therefore, for faster and economical operation, this study is to compare the Light Falling Weight Tests and propose the LFWD test as the in-situ Compaction test. This study suggests the relationship between in-situ RC value, $K_{30}$, $M_R$ and $E_{LFWD}$ of the subgrade and subbase materials in Korea using the laboratory and in-situ testing.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.57-63
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• 2004

The range of stresses experienced in subgrade soils and subbase materials in pavement under working stress conditions is below about 150㎪. Therefore, the deformational characteristics of soils at low confining pressures are important properties in the analysis and design of pavement system. Subgrade soils and subbase materials were collected from the actual pavement projects for testing. To evaluate the effect of confining pressure on modulus of those materials at low confining pressures, RC and FFRC tests were performed. Interestingly, the relationship between modulus of soils and confining pressure is more appropriate in linear space than in logarithm space at low confining pressure. Based on those results, new model fur evaluating the effects of confining pressure on modulus at low confining pressures was proposed.

• International Journal of Highway Engineering
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• v.6 no.2 s.20
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• pp.25-36
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• 2004

The pressuremeter test can be used as an effective tool for evaluating stiffness of lower pavement layers including subgrade and subbase. At present, the most practical and applicable methods for evaluation of the stiffness of the subgrade and subbase are PBT and CBR in Korea. However, these methods have inherent drawbacks and large variabilities of test results themselves. In this study, an evaluation method and a test procedure that can be used for decision of pavement stiffness using pressuremeter were developed. The obtained results representing stiffness of the subgrade and subbase can replace PBT's soil reaction value k and CBR in design methods. It is found that the developed procedure based on the pressuremeter can provide an effective correaltion between the PBT's soil reaction value k and PMT's reloading modulus ($E_R$).

• 한국도로학회:학술대회논문집
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• 1999.11a
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• pp.29-34
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• 1999

• International Journal of Highway Engineering
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• v.5 no.1 s.15
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• pp.35-45
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• 2003

This paper presents a theoretical approach for estimation of CBR-value of subbase course and subgrade using a portable pavement dynamic cone penetrometer(PDCP). The PDCP used in this paper was based on a design from South Africa and extensive studies by Kleyn(1982) and more recently by Liveneh and Ishai(1987) and Chua(1988). To date, California Bearing Ratio[CBR] value was studied mainly for application of pavement structural design. This study was initiated to develop a method of obtaining the in situ CBR-values of subbase and subgrade for the structural evaluation of pavements in the swift and inexpensive manner. PDCP tests were implemented at 20 different kinds of soil samples in the lab and test results were analysed by a theoretical approach introduced. The procedure presented provides acceptable and promising results.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.657-664
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• 2000

Weak and soft compressible clay deposits are commonly found in natural subgrade soils. These Soils need to be stabilized for using the subbase materials of highway constructions. This paper presents that a chemical treatment using chemical additives comprised of sulfate(SO$_4$) and chloride(Cl) is evaluated for stabilizing soft clay deposits and lime. The physical and mechanical characteristics of soil-lime and additives are described by means of a laboratory study. The study results indicate that the presence of chlorides encouraged the efficiency of lime stabilization, and the use of calcium chloride with quicklime is the best additive for improving soil behavior. The treated soil with lime-calcium chloride can have the adaptability to the subbase materials of highway constructions.

• Advances in Computational Design
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• v.3 no.2
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• pp.201-212
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• 2018

Decrease in availability of suitable subbase and base course materials for highway construction leads to a search for economic method of converting locally available troublesome soil to suitable one for highway construction. Present study insights on evaluation of benefits of stabilization of subgrade soils in term of extension in service life (TBR) and layer thickness reduction (LTR). Laboratory investigation consisting of Atterberg limit, Compaction, California Bearing Ratio, unconfined compressive strength and triaxial shear strength tests were carried out on two types of soil for varying percentages of stabilizers. Vertical compressive strains at the top of unstabilized and stabilized subgrade soils were found out by elastoplastic finite element analysis using commercial software ANSYS. The values of vertical compressive strains at the top of unstabilized and stabilized subgrade, were further used to estimate layer thickness reduction or extension in service life of the pavement due to stabilization. Finite element modeling of the flexible pavement layered structure provides modern technology and sophisticated characterization of materials that can be accommodated in the analysis and enhances the reliability for the prediction of pavement response for improved design methodology. If the pavement section is kept same for unstabilized and stabilized subgrade soils, pavement resting on lime, fly ash and fiber stabilized subgrade soil B will have service life 2.84, 1.84 and 1.67 times than that of unstabilized pavement respectively. The flexible pavement resting on stabilized subgrade is beneficial in reducing the construction material. Actual savings would depend on the option exercised by the designer for reducing the thickness of an individual layer.

• 한국도로학회:학술대회논문집
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• 2008.10a
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• pp.485-491
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• 2008

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.781-786
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• 1999

One of the major causes of concrete pavement deterioration is the loss of support due to erosion and pumping of subbase and subgrade. In this study, procedures for the detection of voids under concrete pavement slab are presented using nondestructive test method such as FWD(Falling Weight Deflectometer) and GPR(Ground Penetration Radar). The deflection responses of concrete slab obtained in FWD field test are analysed for determining the presence of void. Also, reflection responses in GPR test are interpreted. It was concluded that these procedures are available for detecting the viods under concrete pavement slab.

• Journal of the Korean Geotechnical Society
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• v.26 no.7
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• pp.71-80
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• 2010

Korea is considered to be a seasonal frozen soil area that thaws in the spring, and freezes in winter. In the current design codes for anti-freezing layer, the thickness of anti-freezing layer is calculated by the depth frozen due to the temperature condition. Therefore, there is a tendency of over-design and applying uniform thickness without the consideration of thermal stability, bearing capacity and frost susceptibility of materials. So, it is essential to study the structural appropriateness of pavement layer and bearing capacity besides the seasonal and mechanical properties of pavement materials to take an appropriate and reasonable design of the road structure. In this paper, the evaluation of frost susceptibility on subgrade, ant-freezing layer, subbase was conducted by means of the mechanical characteristics and model experiment. The temperature, heaving amount, unfrozen water contents and freezing depth of soil samples, the subgrade, anti-freezing layer, subbase soils of road construction site were measured to determine the frost susceptibility.