• Journal of Industrial Technology
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• v.29 no.B
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• pp.81-88
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• 2009

The main purpose of this work is to determine characteristics of undrained shear strength of remolded marine clay at Incheon. Laboratory vane tests with remolded marine clay sampled from west coast at Incheon were performed to investigate the undrained shear strength of them being dumped for reclamation after dredging from the sea bottom. Test results were compared with the predicted values of undrained shear strength proposed by many researchers. It was found that measured results about undrained shear strength with water content was in good agreements with values proposed by Mikasa and Modified Mikasa's empirical formula.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.373-382
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• 1997

• Journal of Industrial Technology
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• v.30 no.A
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• pp.103-109
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• 2010

This research is to determine characteristics of undrained shear strength of remolded marine clay at Incheon and Busan, representing typical marine clays in Korea. Laboratory vane tests with remolded marine clays sampled from coasts at Incheon and Busan were performed to investigate the undrained shear strength of them. Test results were compared with the predicted values of undrained shear strength proposed by many researchers. It was found that measured results about undrained shear strength with water content was in good agreements with values proposed by Terzaghi empirical formula.

• The Journal of Engineering Geology
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• v.12 no.4
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• pp.459-469
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• 2002

We have remolded marine clay sample collected along the vertical and horizontal directions and investigated the characteristics of the consolidation constants by SCT and CRSC methods. We have studied also on consolidation chracteristics and application for weathered granite soil using SCT and CRSC methods for undisturbed and disturbed samples. As the result, values of pre-consolidation stress, compression index, excessive pore pressure, pore water pressure ratio of the marine-clay were different due to different test methods(SCT and CRSC) and sampling directions(vortical and horizontal directions). Disturbed and undisturbed samples of the weathered granite soil have showed similar change aspect like marine clay during over-consolidatied and normally consolidatied stages.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.81-93
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• 1999

This paper investigated the negative skin friction acting on the model piles driven in the cylindrical chamber filled with remolded marine clay. In model tests, three load cells were installed on the model piles consisting of three parts to measure the negative skin friction forces independently. Pore pressures and ground movements were monitored throughout the period of investigation. Finite element analysis was used to simulate the behavior of a model pile. This paper describes the comparison of the behavior of negative skin friction on the single model pile with a numerical analysis by CRISP.

• Geotechnical Engineering
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• v.12 no.5
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• pp.17-26
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• 1996

The undrained behavior of Asan marine soil was investigated by using an automated triaxial testing device. The stress-strain behavior at the preand postfailure state of marine soil under undrained compression and eatension conditions was compared with the behavior of pure silt, pure clay and the overall behavior of Asan marine soil was predicted with the modified Camflay model and the bounding surface model. The marine soil sampled in Asan bay area was clayey silts with 70oA silt-30% clay content and the testing samples were prepared in both undisturbed and remolded conditions. All samples are normally consolidated with 400 kPa of effective mean confining pressure and each sample is unloaded to 200, 100, 67 kPa, respectively. And then the shear test was performed with different confining pressure. According to experimental results, there exists an unique failure line whose slope is lower than silt's and higher than clay's. It is identified that the undrained shear strength of normally consolidated samples increases after crossing the phase transformation line because of volume dilation tendency which is not seen in clay. Overconsolidated samples show different soil behavior compared with pure silt due to its tendency of change in volume. It is also found that the overall behavior of Asan marine soil cannot be predicted precisely with the modified Cam-clay model and the bounding surface model.

• Journal of the Korean Geotechnical Society
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• v.30 no.2
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• pp.53-64
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• 2014

This study sets it's face to define effects of the various loading periods in normal consolidation area on clay's compression and long-term consolidation characteristics through a laboratory test using homogeneous remolded clay. Moreover, by carrying out a long-term consolidation test which diversifies initial consolidation applicable to effective overburden loading in the various loading period. This study intended to suggest the method predicting the final settlement on the basis of loading periods by comparing and analyzing compression curve's characteristics according to loading weight of each stage and increase in loading period when carrying out the standard consolidation test. From the test results, the study shows that as of the soft clay's compression characteristics on the basis of various loading periods, preconsolidation load has a tendency to be decreased slightly as the loading period is getting more and more longer at each step after initial consolidation load puts on the remolded clay which is caused by secondary consolidation's increase in the latter part of each phase. And those effects have an weaker influence on compression index in normal consolidation area at the same time as secondary consolidation brought out quasi-overconsolidation and stabilization of clay's structure, have an influence re-compression index is increased in overconsolidation area on the other hand.

• Journal of the Korean Geotechnical Society
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• v.21 no.9
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• pp.13-23
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• 2005

The prefabricated vertical drains (PVDs) are one of the most widely used techniques to accelerate the consolidation of soft clay deposits and dredged soil. Discharge capacity is one of the factors affecting the behavior of PVDs. In the field, a PVD is confined by clay or dredged soil, which is normally remolded during PVD installation. Under field conditions, soil particles may enter the PVD drainage channels, and the consolidation settlement of the improved subsoil may cause 131ding of the PVD. These factors will affect the discharge capacity of the PVDs. In this study an experimental study was carried out to estimate the discharge capacity of three different types of PVDs by utilizing the large-scale laboratory model testing and small-scale laboratory model testing equipments. The several factors such as confinement condition (confined by soft marine clay or dredged soil) and variations of the discharge capacity were studied with time under soil specimen confinement, The test results indicated that discharge capacity decreases with increasing load, time, and hydraulic gradient. With load application, the cross-sectional area of the drainage channel of PVD decreases because the filter of PVD is pressed into the core. The discharge capacity of the soft marine clay-confined PVDs is much lower than that of the dredged soil-confined PVDs.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.33-43
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• 2014

Recently, the case to construct the structure on the soft clayey ground has increased and in order to the reduction of the cost of construction and maintenance on the social infrastructure facilities we have been trying to improve the soft clayey ground using the existing methods such as the pre-loading method and the vertical drain method. Like this, when various ground improvement methods are applied on the soft clayey ground, a long-term consolidation settlement will be key issue due to low permeability coefficient of cohesive soil. According to existing research results that relate to the consolidation settlement, the loading periods for existing the standard consolidation test (Oedometer test) to obtain the consolidation parameters are needed for minimum ten days or more. Therefore, in this study, the standard consolidation test (24 hours step-loading) and constant strain rate consolidation test changed by strain rate was performed using the remolded marine clay on Gwangyang bay composed of a soft clayey ground of the south-west coast. From the laboratory test results, the characteristics of compression, strain-effective stress relations by constant strain rate and the variation characteristic of the pore water pressure by different of loading speed and the relation between consolidation parameters and constant strain rate are compared and analyzed.