• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.15-24
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• 2001

In order to evaluate undrained shear strength of clayey soils using Piezocone Penetration Test (CPTu), piezoncone factor is utilized. Commonly, piezoncone factors determined by empirical basis were preferred, which were established by correlation between measurements of piezocone test and undrained strengths obtained from other shearing tests. However, previous studies on the empirical piezocone factors were site-specific and there have been no systematic investigations on the effect of both engineering characteristics of clayey soils and soil non-homogeneity on the piezocone factor. Accordingly, the direct application of the previous results to Korean clayey soils without verification may be inappropriate. In this study, empirical piezocone factors are evaluated by comparing 46 CPTu results of 10 test sites with undrained shear strength obtained from Field Vane Test (FVT) and laboratory triaxial tests. Their reliabilities are investigated by the comparison with the previous piezocone factors and the deviation of data distribution from the mean values. And the effects of referencing test methods and typical engineering characteristics of clayey soils such as overconsolidation ratio (OCR) and plastic Index (I$_{p}$) are examined. Because piezocone factors obtained for various soil conditions are widely distributed, it is not appropriate to use the mean value as a representative. Instead, it is recommended to apply the piezocone factors with OCR, which is found to be a major factor in deriving piezocone factor. The necessitated piezocone factors are presented.d.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.2
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• pp.96-106
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• 2003

134 Dutch cone (mechanical cone) and 9 piezocone (electronic cone) penetration tests have been performed in the southwestern part of Korea. In general, Dutch cone results may be different from that of piezocone due to the difference in structure of the cones. 6 Dutch cone and piezocone test data which were obtained at the same point respectively, were analyzed and plotted in soil classification chart proposed by Robertson et. al.(1986, 1990). Cone factors of Dutch cone and piezocone test empirically have been determined using laboratory and field vane test results. Using this cone factors, it was shown that there was good correlation between shear strength estimated using cone resistance and that of laboratory test and field vane tests. It was found that there was a good correlation between cone resistance from Dutch cone and that from piezocone. Relationship formula was also suggested. Dutch cone test provides a useful means for stratigraphic profiling in large project and has some advantage over piezocone in particular situations, such as very soft clay ground and dredged area.

• Ocean and Polar Research
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• v.25 no.spc3
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• pp.353-360
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• 2003

Estimation of undrained shear strength $(S_u)$ of clayey soils from piezocone penetration test (CPTu), which has widely been known as one of very promising in situ test methods, requires piezocone factors. Empirical correlations are generally utilized to derive piezocone factors, but previous studies on the empirical piezocone factors are site-specific and in some cases need engineering characteristics, which should be obtained from additional laboratory tests. In this study, empirical cone factors were evaluated by comparing 6 CPTu results at Shihwa region in Korea with reference $S_u$ values obtained from field vane test (FVT). From previous CPTu results of other regions in Korea as well as the results herein, the correlations between piezocone factor, $N_{kT}$ and CPTu results were investigated and three simplified evaluation methods of $S_u$ using only CPTu results were presented. The $S_u$ values estimated by $(q_T-{\sigma}_v)/{\sigma}'_v$ method shows better matches with those obtained from laboratory tests for marine clays at Shihwa region.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.237-244
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• 2002

A comparative study of 134 mechanical (Dutch cone) and 9. electronic cone (Piezocone) penetration data from the southern part of Korea has been performed. In general, Dutch cone results may be different from piezocone results due to the difference in structure of the cones. Cone penetrometer test data were analyzed and plotted in soil classification chart proposed by Robertson et. al.(1986,1990) Cone factors of Dutch cone and piezocone test have empirically been determined using laboratory and field vane test results. Using this cone factors, it was shown that there was good correlation between shear strength estimated using cone resistance and that of laboratory test and field vane tests. It was found that there was a good correlation between cone resistance from Dutch cone and that from piezocone. Dutch cone test provides a useful means for stratigraphic profiling in large project and has some advantage over piezocone in particular situations, such as very soft clay ground and dredged area.

• Proceedings of the Korean Geotechical Society Conference
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• 1996.10a
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• pp.237-248
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• 1996

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.89-100
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• 2008

Applying graph and correlation developed in other countries to the domestic field has limits. Therefore, it is necessary that Piezocone factor should be determined by including ground characteristics obtained from various test results in the domestic site for better application. In this study, laboratory tests and field tests were performed to find the characteristics of soft ground which was widely distributed around Siwha lake. A comparative analysis of these tests with Piezocone penetration test was performed and the Piezocone factor was estimated by correlationship analysis of undrained shear strength and cone resistance. Also, an appropriate Piezocone factor in the study site was reestimated by utilizing statistical analysis method for deriving reliable result.

• Journal of the Korean GEO-environmental Society
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• v.13 no.5
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• pp.41-49
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• 2012

In this study, laboratory test, in-situ vane shear test and piezocone penetration test in the study area were conducted to investigate the engineering characteristics of soft soils at Cheongra District, Songdo District in Incheon City, the west coast of Gyeonggi province, and Sihwa District in Ansan city. The correlations among compression index, and in-situ vane shear test, and cone resistance were obtained. The variations of liquid limit, plasticity index, water content and compression index with respect to depth exhibit strong similarity. This means that they have strong correlations, which can be used to evaluate the local characteristics of the study area. Thus, the correlations between compression index and physical properties were analysed to investigate the engineering characteristics of soft soil in the study area. The relationships between the measured piezocone factor by empirical methods, and undrained shear strength obtained by triaxial compression test or in-situ vane shear test were compared. It shows the significant correlation and piezocone factors, $N_{kT}$are suggested for the study area.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.169-179
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• 2003

Undrained shear strength of clay deposit is one of the most important properties in the design of geotechnical structures. The use of piezocone test is rapidly growing due to its merit that can measure the in-situ undrained shear strength continuously with less error. The reliability of the shear strength from piezocone test depends upon the cone factor applied. Many researchers have suggested different ranges of values for the factors. This study performs to find out the validity of the suggested values in Korea and their charateristics related to the mechanical properties of clay. Piezocone tests were performed at the site of pilot project of ground improvement at Yangsan-Mulgeum Gyeongnam to investigate the charateristics of piezocone factors. The piezocone fators$(N_{kt}, N_{ke}, N_{\Delta u})$ based on the undrained shear strength from quick triaxial compression test are generally within the suggested range. And there appears considerable relations between undrained shear strength and $(N_{kt}, N_{ke}, N_{\Delta u})$ and between preconsolidation pressure and $(N_{kt}, N_{ke})$, while plasticity index, rigidity index and friction ratio do not show any relations with cone factors. The results also reveal that factor $(N_{\Delta u})$ shows higher reliability than factors $(N_{kt} and N_{ke})$, which show smaller standard deviation, breadth of change and scattering.

• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.53-66
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• 2009

Recently, the importance of investigation for soft ground has been raised, so that various techniques of the investigation for soft ground are being introduced and applied. In particular, Piezocone penetration test has been utilized frequently home and abroad to identify many features of grounds precisely and gain various results in accordance with dividing strata and depth constantly by measuring continuously. In this study, to identify some features of soft clays distributed in the estuary of Nakdong river, researchers conducted field tests and laboratory tests with boring tests, and analyzed and compared with Piezocone penetration test. In addition, credible Piezocone factor of communities of subjects for this study was estimated to analyze some features of undrained shear strength of clay and calculate Piezocone factor compared with corrected cone resistance and apply some statistical techniques to estimated Piezocone factor.

• Journal of the Korean GEO-environmental Society
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• v.20 no.2
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• pp.59-67
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• 2019

Using the results from laboratory soil test, field vane test and piezocone penetration test, the engineering characteristics of the soft ground at east side of Gwangyang Port, which is located at south coast of Jeollanam-do, were investigated and optimal piezocone penetration test depth was derived to calculate piezocone factor. In this paper, the results of 61 laboratory soil tests, 226 times of field vane tests and 26 piezocone penetration tests were used. The result of laboratory soil test suggested that some physical properties such as specific gravity, moisture content, liquid limit and plastic index and others are higher than other south coast regions, meanwhile uniaxial compression strength, undrained shear strength, defined as mechanical property, appeared to be relatively small, distributed widely. According to the plastic chart, the ground was classified as high compressibility clay and low compressibility clay, mostly represent to Type 3 clay by Robertson (1990)'s classification chart. Piezocone factor was calculated by empirical method, based on the undrained shear strength which was obtained by the field vane test. According to the analysis with 3 different depth range, to set the appropriate measured depth range of piezocone penetration for comparation, using average value of the range of 5 times the vane length showed the highest correlation.