• The Journal of Engineering Geology
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• v.17 no.3
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• pp.351-358
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• 2007

Using the results of the Piezocone Penetration Test(PCPT) which were executed at the Yangsan-Mulgum site, the applicability of the interpretation methods far estimating the OCR(Overconsolidation Ratio) of soft clay was evaluated. At the same time, the results from the laboratory tests using the total of 172 undisturbed soft clay samples taken from the 44 bore holes of the Yangsan-Mulgum site were used to compare the OCR values obtained from the consolidation test with those from the PCPT. The relationship between the predicted overconsolidation ratio($OCR_p$) using the PCPT and the measured overconsolidation ratio($OCR_c$) from the laboratory consolidation tests are investigated and presented in this study. The $OCR_p$ by using the Powell et al.'s method for non-fissured clay from the results of the PCPT shows the best relationship with the $OCR_c$ obtained from the laboratory consolidation test.

• Geomechanics and Engineering
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• v.6 no.6
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• pp.577-592
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• 2014

The methods for estimating in-situ hydraulic conductivity ($k_{hp}$) and coefficient of consolidation ($c_{hp}$) in the horizontal direction from piezocone penetration and dissipation test results have been investigated using test results at two sites in Saga, Japan. At the two sites the laboratory values of hydraulic conductivity ($k_v$) and coefficient of consolidation ($c_v$) in the vertical direction are also available. Comparing $k_{hp}$ with $k_v$ and $c_{hp}$ with $k_v$ values, suitable methods for estimating $k_{hp}$ and $c_{hp}$ values are recommended. For the two sites, where $k_{hp}{\approx}k_v$ and $c_{hp}{\approx}2c_v$. It is suggested that the estimated values of $k_{hp}$ and $c_{hp}$ can be used in engineering design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2C
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• pp.95-103
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• 2008

Seismic piezocone penetration tests (SCPTu) can be used to obtain dynamic properties of soils as well as cone resistance and penetration pore pressure. However, the SCPTu system can be hardly utilized in marine soils because it is difficult to install the source apparatus which generates the shear wave in offshore site. The authors developed an inhole type piezocone penetration test (CPTu) equipment which both source and receiver composed of bender elements were installed inside the rod located behind the cone. Therefore, it can be applicable to even an offshore site without any additional source apparatus. The objective of this paper is to investigate the practical application of inhole type CPTu by performing laboratory model tests using kaolinite as soft clay. The shear wave velocities of kaolinite soil were measured with time, and the effects of soil disturbance due to the installation of source and receiver were also examined for various distance between source and receiver.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.191-199
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• 2000

In this research, the finite element analysis of piezocone penetration and dissipation tests has been conducted using the anisotropic elastoplastic-viscoplastic bounding surface model, virtual work equation, and theory of mixtures formulated in the Up[dated Lagrangian reference frame for the large deformation and finite strain nature of piezocone penetration. The formulated equations have been implemented into a finite element program. The cone resistance, excess pore water pressure, and dissipation of excess pore water pressure from the finite element analysis have been compared and investigated. An effective simulation could be performed with the use of the anisotropic and viscous soil model. The finite element formulations and the results are described in part 'I' and part 'II' respectively.

• Geotechnical Engineering
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• v.14 no.6
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• pp.45-56
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• 1998

In order to select a proper ground improvement technology and to assess the quality and rate of improvement in the soft deposits. it is essential to characterize in-situ properties of the soft marine clay layer that may have many thin silt or sand seams. In this paper, both piezocone and flat dilatometer tests were performed to characterize in situ properties of a marine clay. Both tests provided quite similar site classifications, and in both tests the penetration pore water pressure was the better indicator for the classification of marine clay layer, especially in which sand or silt seams are frequently interbedded. Undrained strengths determined by both the cone tip resistance and the excess pore water pressure measured from piezocone were very similar in clayey soil layers. And the untrained strength determined by dilatometer had an approximately average value of undiained strengths obtained from piezocone. In addition, the theoretical time factor that can consider pore pressure dissipation effect during cone penetration may provide a reliable estimation of the coefficient of consolidation, especially for a coastal site which includes many silt or sand fractions or seams.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.4
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• pp.1-10
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• 2008

Shear wave velocity($V_S$), which can be obtained using various seismic tests, has been emphasized as representative geotechnical dynamic characteristic mainly for seismic design and seismic performance evaluation in the engineering field. For the application of conventional geotechnical site investigation techniques to geotechnical earthquake engineering, standard penetration tests(SPT) and piezocone penetration tests(CPTu) together with a variety of borehole seismic tests were performed at many sites in Korea. Through statistical modeling of the in-situ testing data, in this study, the correlations between $V_S$ and geotechnical in-situ penetrating data such as blow counts(N value) from SPT and piezocone penetrating data such as tip resistance ($q_t$), sleevefriction($f_s$), and pore pressure ratio($B_q$) were deduced and were suggested as an empirical method to determine $V_S$. Despite the incompatible strain levels of the conventional geotechnical penetration tests and the borehole seismic tests, it is shown that the suggested correlations in this study are applicable to the preliminary estimation of $V_S$ for Korean soil layers.

• Geotechnical Engineering
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• v.13 no.6
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• pp.25-36
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• 1997

A degree of consolidation at any time can be evaluated by using cone penetration test after soil improvement. In this case, after stopping the penetration of a piezocone, pore pressure dissipation(PPD) best is carried out until the pore pressure remains constant. Since the hydraulic conductivity of soft ground is very small, it takes very long time to finish the PPD test. This research is performed to develop a method overcoming this problem of the PPD test and reducing the test time. The analyses are carried out in the following ways : an equilibrium pore pressure can be determined by using pore pressure measured in the middle of the test, which is predicted by hyperbolic, Asaoka and Hoshino methods. And this equilibrium pore pressure is compared with the one measured in a test of long duration. As a result of the study, it is found that Hoshino method is the best way to predict the equilibrium pore pressure in a teat of short duration. And it is proposed as a methodology to fond a minimal time in which we can get an equilibrium pore pressure.

• Journal of the Korean GEO-environmental Society
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• v.22 no.9
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• pp.5-16
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• 2021

In this study, piezocone coefficients of clays (Hwasung, Gunsan, Changwon, Busan) were analyzed from piezocone penetration tests those accompanied with vane shear and UU tests. Piezocone coefficients of west sea clays (Hwasung, Gunsan), i.e, N_kt is 12.6 and N_qu is 8.8, while those of south sea clays are 16.5 and 9.2 respectively. The difference of liquid limit between south and west clays causes main roles those which west sea clay is generally lower than 50%, i.e, CL, and liquid limit of south sea clay is mostly higher than 50%, i.e CH. Piezocone coefficients obtained from several tests show similar trends even though they still have some differences depending on each test. However, they show clear differences depending on liquid limit. Therefore, piezocone coefficients need to be used with caution depending on LL.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.311-320
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• 2003

The coefficient of consolidation of clay deposit is one of the most important properties in the design of ground improvement. The in-situ value of $c_h$ is generally estimated by pore pressure dissipation using piezocone. Many researchers have suggested theoretical formula for its estimation. This study attempts to find out the validity of the existing theoretical formula in Korea and to find out the characteristics of $c_h$ related to the mechanical properties of clay. Piezocone tests and laboratory tests were performed at the site of pilot project of ground improvement at Yangsan-Mulgeum, Gyeongnam. Comparison of the estimated values of $c_h$using piezocone tests results and those from laboratory consolidation tests are carried out. Results show that Torstensson(cylindrical cavity theory) and Teh & Houlsby solutions derive similar values of $c_h$. And $c_h$ from oedometer test shows values similar to the above two methods. The value from either of the above two methods[Torstensson(cylindrical) or Teh & Houlsby] is recommended to be used as $c_h$.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.49-54
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• 2000

Several soil parameters can be calculated for results of Piezocone test; sensitivity, soil classification, OCR, undrained shear strength, coefficient of consolidation etc., and used to analysis geotechnical problems. Particularly, the coefficient of consolidation which is related to degree of consolidation varies according to rigidity index(I/sub r/). In this study, rigidity index(I/sub r/) was analyzed by Roy's formula. Trixial tests and unconfined compression tests data in the ten sites was analyzed. In conclusion, rigidity index(I/sub r/) was suggested such as rigidity index(I/sub r/) = 15∼60, average rigidity index value(I/sub r/) of approximately 33 within a country.