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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.

Stokoe II K.H.,University of Texas at Austin | Park K.,University of Texas at Austin | Seo W.,GS Engineering and Construction Co. | Schuhen M.,Sandia National Laboratories
9th US National and 10th Canadian Conference on Earthquake Engineering 2010, Including Papers from the 4th International Tsunami Symposium | Year: 2010

A field method has been developed at the University of Texas at Austin to evaluate the linear and nonlinear shear moduli of soil. The method utilizes a dynamically-loaded shallow footing as the seismic source and 3-D geophones embedded in vertical arrays beneath the footing as sensors. The field method was applied to cemented alluvium at the Yucca Mountain site in Nevada to evaluate the effects of stress state and strain amplitude on shear modulus. Experimental results show that small-strain shear moduli were obtained at total vertical stresses from about 10 to 250 kPa and shear moduli were evaluated at shearing strains ranging from about 10 -4 to 10 -2%. Comparisons of field measurements with laboratory-determined shear modulus reduction curves evaluated with reconstituted gravelly specimens support the validity of the field method and show the need for these in-situ measurements, especially in hard-to-test soils like cemented alluvium.

Park K.,University of Texas at Austin | Stokoe II K.H.,University of Texas at Austin | Olson R.E.,University of Texas at Austin | Seo W.,GS Engineering and Construction Co.
Soil-Foundation-Structure Interaction - Selected Papers from the International Workshop on Soil-Foundation-Structure Interaction, SFSI 09 | Year: 2010

Most existing methods of estimating the settlement of footings in cohesionless soils under working stresses are empirical and based on correlations with field measurements of settlement. The result is considerable scatter and a lack of a basis for long term improvements. In this paper we propose a method of analysis based on equivalent-linear elasticity that involves measurement of real soil properties and uses simple analytical methods.We also propose methods to determine and/or estimate the needed soil properties.We report here on load tests of two footings and one plate with diameters ranging from 0.25m to 0.91 m, in silty sand, in which measured settlement is compared with settlement predicted using the theory and soil properties determined in the field from seismic tests.We also compare measured settlements with values calculated with Schmertmann's widely used method based on penetration testing. © 2010 Taylor & Francis Group.

Li S.,GS Engineering and Construction Co. | Kim Y.-G.,Korea Gas Corporation
Metals and Materials International | Year: 2013

Stray current corrosion phenomena of ductile iron pipe (DIP) located in the vicinity of cathodically protected steel pipe was assessed using the boundary element method. When all joints in DIP were electrically connected, the maximum corrosion rate was 0.005 mm/y. However, when the joints were isolated, the corrosion rate increased due to the jumping effect of stray current at isolated joints, which resulted in the increase of maximum corrosion rate to 0.87 mm/y at the isolated point. Moreover, the electrical bonding between the DIP and steel pipe could not act effectively but showed an adverse effect of collecting more cathodic protection (CP) currents into the DIP, which eventually jumped out into the soil and resulted in larger amount of stray current corrosion. Therefore it is desirable to apply control methods from the design and construction stage, which include the increase of anodebed and the pipe distance, electrical connection of DIP joints, installation of sacrificial anode at isolated joints, or the application of CP on DIP, etc. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

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.

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.

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

An exponential formula is used to best-fit theoretical and measured time-settlement (or excess pore pressure) data over the full range of consolidation. The formula fits well theoretical consolidation solutions and measured data regardless of using the incompletely consolidated data, and it is possible to reliably predict the ultimate values. This result has a different trend from those of the hyperbolic and Asaoka (1978) methods. Thus the coefficients of horizontal consolidation and the mobilised discharge capacity qw(mob) can be expressed in terms of parameters of the exponential formula corresponding to the measured data and the theoretical solutions. The application of the proposed method to six case records on three construction sites (with a maximum drainage path lm of 7-50m) indicates that the coefficient of horizontal consolidation for the ideal condition are likely to be used to reconstruct the monitored time-settlement curve and also to adjust the hydraulic and consolidation properties of each monitored point. Based on back-analysis, the mobilised and required discharge capacity for a preliminary design guideline are recommended as: qw(mob)=(1-5)khlm 2 and qw(req)=19.63khlm 2, where kh is the horizontal permeability of soil. © 2014 Elsevier Ltd.

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.

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.

Lee Y.-H.,Konkuk University | Sung W.-J.,GS Engineering and Construction Co. | Seong K.-W.,Konkuk University
Journal of Engineering Mechanics | Year: 2010

When a prestressed double-T beam is subjected to torsion, a pair of prestressing tendons resists torsional rotation because of the restoring action of the displaced prestressing tendons. A comprehensive formulation to account for the torsional restoring action of double-T beams is presented, based on Vlasov's hypothesis of considering warping displacement in an open-section. The deformation energies of prestressing tendons and reinforcing bars are calculated based on the deformed geometry to obtain the total potential energy. A two-noded beam element with seven degrees of freedom per node approximates an axial displacement, two translations, two flexural, and one torsional rotations, and a warping displacement to derive the finite-element equilibrium equations by minimizing the potential energy function. The role of prestressing forces of the tendons on the torsional resistance and the limitations of the traditional transformed section approach are addressed when it is applied to torsional problems. As a numerical example, an existing three-span continuous double-T beam is analyzed, and the bimoment and angle of twist are compared to those calculated using conventional three-dimensional finite-element analysis and the analytical solution of governing differential equations. © 2011 ASCE.

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