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Chung S.G.,Dong - A University | Kweon H.J.,Dong - A University | Jang W.Y.,GS Engineering and Construction Co
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2014

A simple hyperbolic equation is used to best fit measured piezocone pore pressure dissipation data. The same hyperbolic equation, albeit with slight differences in its coefficients, fits well the existing theoretical solutions/charts for piezocone dissipation response. Coefficient of consolidation ch can be conveniently expressed in terms of the hyperbolic parameters corresponding to the measured data and the existing solution charts. Field piezocone dissipation test data for Busan clay is successfully fitted using the provided hyperbolic equation. The ch values thus determined over a range of degree of consolidation (10290%) compare well with ch values obtained by the traditional direct use of the same existing theoretical solutions or charts. © 2014 American Society of Civil Engineers. Source


Chung S.G.,Dong - A University | Chung J.G.,Pusan Information College | Jang W.Y.,GS Engineering and Construction Co | Lee J.M.,Dong - A University
Marine Georesources and Geotechnology | Year: 2010

In this study, CPT and FVT tests are carried out on young, normally consolidated clay (Busan clay, which is an unusually thick deposit) at several locations in the Nakdong River deltaic plane in Busan, Korea. Two correlation techniques are applied for estimating the cone factors for which the uncorrected and corrected field vane strengths are used as the reference strength. First, due to the scattered data over the entire depth, a direct correlation between the tested results (a method generally used in practice), is applied for each depositional environment (facies) that is detected from the CPT profiles and the geological analysis. Secondly, a special attempt is made to determine the cone factors based on the fact that the ratios of the field vane strength and the (qt - σv0) and (u2 - u0) values to the effective overburden pressure respectively, are approximately constant for each facies (the indirect correlation). It appears that the values obtained from the two techniques are almost identical. However, the direct correlation is sensitively affected by the fabric effects especially in some of the uppermost and lowermost layers of the clay and hence the arithmetic average values of each facies sometimes result in lower correlation coefficients. It is therefore inferred that the indirect correlation is more proficient for estimating the cone factors at each facies and can be used for practical applications. From the results of the indirect correlation, the cone factors of Busan clay are Nkt = 7.13-13.06, Nkt,corr = 9.45-17.07, NΔu = 6.10-9.88 and NΔu,corr = 8.41-12.24, the corrected values of which are considerably smaller or larger than the general ranges recommended by Lunne et al. (1997a). However, good correlations between Nkt and IP, and between NΔu (or Nkt) and Bq, are not found for the clay. © Taylor & Francis Group, LLC. Source


Jang W.Y.,GS Engineering and Construction Co | Chung S.G.,Dong - A University
Geotextiles and Geomembranes | Year: 2014

Prefabricated vertical drains (PVDs) were partially or fully penetrated into thick clay deposits at a reclamation project in Busan City, Korea. Elasto-viscoplastic finite element analysis is conducted to predict the long-term behaviors using a macro-element technique. Settlements predicted using laboratory-based and back-analyzed soil parameters are in good agreement with monitored data. The relationships of time versus volumetric strain and excess pore pressure at each element are effective in investigating the overall behaviors; that is, the settlements in the improved zone degrade from steep to gentle slopes, whereas those in the unimproved zone change with a relatively gentle slope. The effect of partially penetrated PVD on ue dissipation appears to be in relatively good agreement with results obtained by Ong et al.'s (2012) method. © 2014 Elsevier Ltd. Source


Yoon G.L.,Korea Ocean Research and Development Institute | Yoon Y.W.,Inha University | Chae K.S.,GS Engineering and Construction Co
Environmental Earth Sciences | Year: 2010

This paper investigates the fundamental characteristics of shear strength and deformation of crushed oyster shell-sand mixtures to stimulate recycling of waste oyster shells. Standard penetration tests (SPT) and large-scale direct shear tests were carried out with different kinds of dry unit weight and mixing rate of oyster shell-sand mixture. Correlations between N-value, dry unit weight, and friction angle of mixtures were observed from the results of experimental tests, making it possible to estimate the in situ strength from SPT, and the coefficient of volume compressibility from the confined direct-shear compression test. These results also make it possible to compute the settlement of oyster shell-sand mixture when used in soft ground improvement. © 2009 Springer-Verlag. Source


Chung S.G.,Dong - A University | Lee J.M.,Dong - A University | Jang W.Y.,GS Engineering and Construction Co
Engineering Geology | Year: 2014

Three types of fixed-piston samplers were employed at Nakdong River Delta. The retrieved samples were equally divided into 100. mm long pieces. Quality was evaluated using suction, shear wave velocity, and consolidation tests. The constant rate of strain consolidation test, rather than the incremental loading test, produces a better correlation with the nondestructive test results. The sample quality progressively degrades from the near-center to both ends of each sampling tube. The sample quality measured using the three methods on samples at the near-center of the sampling tubes consistently varies with the in-situ void ratio in the upper clay; however, such a trend is not observed in the lower clay. This may be attributed to the effect of total stress relief on the clay. The sample quality evaluated deteriorates in the following order: oil-operated type, mechanical type, and hydraulic type. The results suggest that the difference in sample quality is principally caused by the mechanical disturbance attributed to the different penetration mechanisms (methods) of the sampling tubes. The tip angle of sampling tubes significantly affects sample quality, whereas the length-to-diameter ratio has a relatively insignificant effect. © 2014 Elsevier B.V. Source

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