• Journal of the Korean GEO-environmental Society
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• v.8 no.1
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• pp.27-32
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• 2007

Trafficability for construction equipments in soft ground should be secured by improving the surface course. For this situation, the ground improvement technique has been used with stiffening agent, but the improvement cement has been mostly used so far. However, oyster shell has been developed and used as the stiffening agent to expand the chance of recycling oyster shell, which is regarded as solid waste. In this research, it was confirmed mechanical characteristics of oyster shell as stiffening agent by analyzing the strength characteristic such as mixing rates, water contents, and curing days of that to the dredging soil.

• Journal of the Korean GEO-environmental Society
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• v.19 no.5
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• pp.23-31
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• 2018

The dredging project became more important with the recent construction of off shore structures and reclamation projects. Accordingly, more exact quantitative estimation of the dredged amount should be required. The sub-sea ground information can be obtained generally by the boring investigation and the dredged amount can be estimated based on the depth or the deeper bound of a ceratin layer via 3D visualization program. During the estimation process, the input DB should be constructed with 1D elevation information from boring investigation for the spatially approximated distribution of a deeper bound of each ground layer. The input DB can be varied with the application of the borings and the approximation targets. Therefore, the 3D visualized ground profile and dredged amounts are compared on the actively dredged sites, vicinity of Saemangeum area and outer port area in Gunsan with regard to the input DB construction methods. Conclusively, the input DB based on the spatially approximated depths show higher precision results and more reasonable 3D visualized ground profiles.

• Journal of the Korean Geosynthetics Society
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• v.11 no.1
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• pp.47-56
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• 2012

Discharge capacity of PBD is sensitive in proportion to thickness and ground condition, and drainage of PBD declines due to disturbance effect in surrounding ground by mandrel used for vertical drainage setting and setting machines and type. Also, deviation of discharge capacity gets larger according to ground condition, construction condition and soil properties. But cause and analysis of those problems like reduced discharge of capacity and delayed dissipation of pore water pressure for discharge capacity is lack. Thus, in this text, ground improvement and discharge capacity is investigated by implementing composite discharge capacity test for analysis of an effect factor of PBD discharge capacity with in-situ ground condition. After fixing the vertical drain on a cylindrical cylinder, put churned sample into the cylinder. After in-situ ground and reclamation of ground are dredged, load following the loading step of 30, 70 and 120kPa using a pressure device. Result of the test, The discharge capacity was SM>ML>CL>CL(dredged soil) in situ condition and more fine-grained content, the amount of discharge was greater.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.75-83
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• 2002

This paper is to investigate the mechanical characteristics of light-weighted soils (LWS) consisting of expanded polystyrene(EPS), dredged clays and cement by using both uniaxial and triaxial compression tests. The mechanical characteristics of the compressive strength of LWS are analysed with varying initial water contents of dredged clays, EPS ratio, cement ratio, and curing stress. In the triaxial compression state, it is found that the compressive strength of LWS containing EPS is independent on the effective confined stress. As the EPS ratio decreases($A_E$<2%) and cement ratio increases($A_c$>2%), the behavior characteristics of triaxial compressive strength-strain relationship is similar to that of cemented soil which decreases rapidly in compressive strength after ultimate compressive strength. For the applications of LWS to ground improvements which require the compressive strength of up to 200kPa, the optimized EPS ratio and initial water content of dredged clay are estimated to be 3~4% and 165~175%, respectively. Also, the ultimate compressive strength under both triaxial test and uniaxial compression states are almost constant for a cement ratio of up to 2% and then critical cement ratio of this LWS shall be 2%.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.309-317
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• 2002

The mechanical characteristics of Light-Weighted Foam Soil(LWFS) are investigated in this research. LWFS is composed of the dredged soil from offshore, cement and foam to reduce the unit-weight and increase compressive strength. For this purpose, the unconfined compression tests and triaxial compression tests are carried out on the prepared specimens of LWFS with various conditions such as initial water contents, cement contents, curing conditions and confining stresses. The test results of LWFS indicated that the stress-strain relationship and the compressive strength are strongly influenced by the cement contents rather than the intial water contents of the dredged soils. On the other hand, the stress-strain relationship from triaxial compression test has shown strain-softening behavior regardless of curing conditions. The stress-strain behavior for the various confining stress exhibited remarkable change at the boundary where the confining stress approached to the unconfined compression strength of LWFS. In order to obtain the ground improvement of the compressive strength above 200kPa, the required LWFS mixing ratio is found to be 100%~160% of the initial water contents of dredged soil and 6.6% of cement contents.

• Journal of the Korean GEO-environmental Society
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• v.20 no.5
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• pp.39-46
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• 2019

Most of the soil used for reclamation is marine clay generated from dredging construction.The soft ground made of dredged clay has high water content and high compressibility, so the bearing capacity of the ground is very weak and it is difficult to enter the ground improvement equipment. Therefore, surface hardening treatment method is used to enter equipment prior to full-scale civil engineering work, and stabilizer is mainly used for cement series. Cement-based stabilizers have the advantage of improving the ground in a short period of time and have excellent economic efficiency, but they are disadvantageous in that they cause environmental problems due to leaching of heavy metals such as hexavalent chromium. In this study, environmental effects evaluation of dredged clay mixed with normal portland cement and environmentally friendly stabilizer was evaluated, and uniaxial compressive strength test and indoor model test were conducted to confirm the bearing capacity characteristics of the solidified layer.

• Journal of the Korean Geosynthetics Society
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• v.22 no.1
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• pp.87-96
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• 2023

There are a lot of difference between the surface settlement and the differential settlement measured at the Busan New Port, where the dredged and reclaimed clay layer exists and below the clay is originally thickly distributed. To find the cause and solution of this, the actual conditions of each differential settlement used for the soft ground improvement, characteristics, installation method, measurement frequency, measurement data management, and data analysis of each type were considered. In the deep soft ground improvement work where large deformation occurs, the bending deformation of the screw-type differential settlement gauge is less than that of other types of measuring instruments, so there is less risk of loss, and the reliability of data is relatively high as the instruments are installed by drilling for each stratum. Since the greater the amount of high-precision settlement measurement data, the higher the settlement analysis precision. It is necessary to manage with higher criteria than the measurement frequency suggested in the standard specification. For the data management of the differential settlement gauge, it is desirable to create graphs of the settlement and embankment height of the relevant section over time, such as surface, differential, and settlement of pore water pressure gauge for each point. In the case of multi-layered ground with different compression characteristics, it is more appropriate to perform settlement analysis by calculating the consolidation characteristics of each stratum using a differential settlement data.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.101-111
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• 2000

This research is results of experimental and numerical works on characteristic of strength increase and bearing capacity in dredged and reclaimed soil due to desiccation shrinkage. For a soil sampled from southern coastal area in Korea, basic soil property tests and standard consolidation test with falling head permeability tests were carried out to obtain consolidational characteristics of soil. Double cone penetration test, laboratory vane test and unconfined compression test were also performed to investigate the change of shear strength with degree of desiccation. Model tests were performed in 1G environment and 30G level artificially accelerated condition by using the centrifuge model test facilities to investigate the bearing capacity of desiccated ground. Test results were analyzed by using the theoretical and load-settlement characteristics method proposed by Meyehof & Hanna(1978). On the other hands, the numerical technique, using the finite strain consolidation theory considering the effect of desiccation was used to estimate the appropriate time of using heavy construction equipments in field with respect to strength increase due to desiccation.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.469-478
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• 2005

Understanding of an accurate state of consolidation of underconsolidated clay body, like a recently dredged or reclaimed clay deposits, is one of the most difficult tasks. The estimation of the consolidation status of these clay bodies is often made by laboratory tests of numerical analyses. However these methods demonstrated crucial limitations in the accurate prediction. Therefore, the predicted degree of consolidation from various techniques is verified by actual measured field data. The degree of consolidation of clay body in the East Side Hinterland of Gwangyang Port(2nd Phase) is evaluated in this study by using various techniques such as oedometer test, CPTu, numerical analysis and piezometer tests etc. And the results are compared each other to find the most reliable prediction technique. The merit and reliability of each method is discussed in detail. It is revealed from in this study that the estimation of degree of consolidation by an actual pore water pressure measurements is the most reliable technique.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.75-81
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• 2003

To investigate the reinforcing effect of subsurface layers of marine dredged clay(DMC) mixed with the micro-fiber(MF), a series of laboratory tests were performed on the DMC specimens with and without MF through uniaxial and triaxial compression tests. For the test programme, the elapsed time after dredging of marine clay, mixing rate and length of MF, and curing time of the composite were chosen as the important factors affecting the strength behaviour. The strength of the DMC mixed with MF and waste lime(WL) used for the admixture was found to be enhanced with the increasing content and length of MF, and with decreasing water content of DMC. MF and WL were applied as materials for trafficability improvement of the very soft reclaimed ground by DMC.