• Journal of Industrial Technology
• /
• v.28 no.A
• /
• pp.11-17
• /
• 2008

Applicability of hyperbolic settlement prediction method to consolidation settlement in the dredged and reclaimed ground was assessed by analyzing results of centrifuge tests modelling self-weight consolidation of soft marine clay. From literature review about self-weight consolidation of soft marine clays located in southern coast in Korea, constitutive relationships of void ratio - effective stress - permeability and typical self-weight consolidation curves with time were obtained by analyzing centrifuge model experiments. For the condition of surcharge loading, exact solution of consolidation settlement curve obtained by using Terzaghi's consolidation theory was compared with results predicted by the hyperbolic method. It was found to have its own inherent error to predict final consolidation settlement. From results of analyzing thc self-weight consolidation with time by using this method, it predicted relatively well in error range of 0.04~18% for the case of showing the linearity in the relationship between T vs T/S in the stage of consolidation degree of 60~90 %. However, it overestimated the final settlement with large errors if those relation curves were nonlinear.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.1
• /
• pp.113-125
• /
• 2002

Ground improvement technique of cement stabilization via Deep Soil Mixing with dry cement is gaining popularity, particularly in Japan and other parts of Southeast Asia and in Scandinavia. Cement can be mixed with deep soft clay deposits, typical of marine environments, to improve the bearing capacity and/or reduce the compressibility of the material so that an otherwise poor site can be developed. However, the strength/deformation behaviour and resulting soil structure of the clay-cement mixture is presently not well understood with respect to both dry and wet mix methods. An extensive laboratory test was carried out to determine the mechanical characteristics of kaolin-cement, with some brief examination of the effects of curing environment. Laboratory tests include triaxial tests, unconfined compression tests, isotropic consolidation testis and oedometer tests. Cement contents up to 10 percent were considered and water curing was employed. Samples were cured for 7 to 112 days while submerged in distilled water. Conventional laboratory tests were also performed. In this paper, the laboratory testing program is described and various sample preparation techniques are discussed. Preliminary triaxial compression test results and trends at varying moisture contents, cement contents, confining pressures and curing times will be presented.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.1
• /
• pp.221-228
• /
• 2003

In land reclamation construction using marine clay, a measure of material function, that is, the relation between void ratio-effective stress and permeability, is very important aspect for the prediction of self-weight consolidation behavior. But reclaimed ground has very high water content, so there are many difficulties in the laboratory test for measuring material function. For this reason, some researches are carried out using slurry cconsolidometr to measure material function. In this study, material function was measured using slurry consolidometer, and to overcome the shortcoming of researches using slurry cosolidometer, an equation for the prediction of material function was proposed on the basis of column test's parameter. Material function was determined through low stress consolidation test and permeability test, and it also was calculated with the equation using column test parameter. The continuity of material function could be confirmed through these tests. Material function is easily determined with the equation proposed in this study, and can be used for the prediction of self-weight consolidation behavior.

• Journal of the Korea Construction Safety Engineering Association
• /
• s.43
• /
• pp.98-106
• /
• 2007

In this paper, a ground disturbance effects, strength and consolidation characteristics of soft clay through using the large block samples($\theta$:300mm, H:400mm) and the piston samples, f hose which had been gathered in west coast and south coast. Especially, we have assessed the coefficient of horizontal consolidation when penetrating the mandrel considering the variance of ratio between diameter and height in drainage sample through the experiment of the oedometer test and Rowecell and also investigated the disturbance area in smear zone by interior model test, the strength originated by disturbance, the variance in characteristics of the consolidation. As the result, the large block sample has been investigated that ihe uniaxial compression test(qu) was shown bigger than the piston sample by about 11-19%. Under the size of anistropy in consolidation, the coefficient ratio of consolidation(ch/cv,) perfomed by standard consolidation test(SC) was shown bigger than that of (Cro/Cv) by the Rowecell test. And the coefficient ratio of consolidation(Cro/Cv) perfomed by piston sample was evaluated bigger than that Of (Cro/Cv) by the large block sample by about 0.9-1.9. The coefficient ratio of consolidation along with the variance in ratio of between diameter and height when penetrating the mandrel was shown big difference according to the characteristics of soil of the specimen. In addition, ds/dw of smear zone at the marine clay in west-south was ranged from 1.6 to 4.2. The width of variance in rat io[(qud)/(quud)] of strength n the area between disturbance and undisturbance was shown big as about 72-91% but the principle was judged with the similiar range when the decrease of the strength in smear zone become the zone under 25% in unditurbance area.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.9
• /
• pp.67-76
• /
• 2009

The problems of bearing capacity, settlement and shear deformation occur when constructing a structure such as harbor, airport and bridge on soft ground of marine clay, silty clay or sandy soil. Various ground improvement methods are applied to obtain preceding settlement of soft ground and strength increase. In this study, to analyze the applicability of PBD method in deep soft ground, the compound drainage capacity test was operated in comparison with SD. As a result of the test, a minimum drainage capacity of drain material was estimated to be more than $10\;cm^3/sec$ at a more than $400\;kN/m^2$ and less than $5\;cm^3/sec$ at a more than $500\;kN/m^2$ confining pressure in case of single core PBD. In case of double core PBD, it was estimated to be more than $10\;cm^3/sec$ at a more than $500\;kN/m^2$ confining pressure.

• Geotechnical Engineering
• /
• v.9 no.4
• /
• pp.93-102
• /
• 1993

Soil structures which are constructed over the soft ground settle continuously by the self-weight of embankment for a long time. It is because of timetependent behaviours . consolidation and creep occurring simultaneously. This paper tries to determine the required parameters for analysis of the creep behaviour in marine clays and studied the effect of the confining stress and stress level on the creep parameters . As a result, it presents an equation for the determination of creep parameters according to stress level considering that elastic modulus El and creep parameter f are found to be affected by the applied stress level.

• Journal of the Korean Geotechnical Society
• /
• v.38 no.7
• /
• pp.25-37
• /
• 2022

In this paper, a small-scale model testing system was developed using a series of small-scale model tests to analyze the mechanism of compaction pile formation and evaluate the quality of controlled grading aggregates proposed as an alternative material to the sand compaction pile (SCP) method and granular compaction pile (GCP). These are the most typical ground improvement methods in field practice, particularly for soft grounds. However, the SCP has faced difficulties due to the supply shortage of natural sand and the corresponding price surge of sand. The GCP is limited in marine soft grounds because of the failure occurring at the pile tip caused by excessive expansion of the deeper bulbs, leading to uneven bulb formation. The uniformity of compacted pile bulbs is critical to ensuring the bearing capacity and quality of the compaction pile. This study aims to evaluate the performance of the new material and controlled grading aggregates using small-scale model tests simulating field compaction process to investigate its potential application in comparison with SCP. The compaction piles are examined in four cases according to different materials used for compaction pile and clay strength. The compaction pile materials, which are made of sand and controlled grading aggregates, used in this study were compared to reveal the mechanism of the bulb creation. The experimental data confirm that the bulb formation quality of the traditional sand and the new material, controlled grading aggregates are comparable. The compaction pile made of controlled grading aggregates presents higher bearing capacity than that of marine sand.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.6
• /
• pp.83-90
• /
• 2012

Generally, the effect of the cement deep mixing method on the improvement of clay ground is far greater than the effect of physical improvement. Although it leads to great improvement strength in the initial stage, there are not many constructional precedents in Korea and it is hard to manage quality according to the cement-clay mixing method. In order to figure out the strength characteristics according to the mixing ratio of cement, sand, and clay and the improvement characteristics of weak ground according to the forms of the specimens to be improved, marine clay was used in this study to conduct the uniaxial compression test and soil bin model test. The test piece specimens for the uniaxial compression test were mixed with sand in a fixed ratio with the criterion of the water cement ratio. The cement was mixed with clay in the ratios of 10%, 20%, 30%, and 40% to the clay weight. The moisture content of the soil ground was made in the ratios of 40%, 60%, and 80%. The test piece specimens went through curing by moistening for 7, 14, and 28 days and underwent the uniaxial compression test according to the curing period. For the bearing test, the soil bin models were made and the ground improved in the Mat type was formed. After that, the bearing strength was compared in this study according to the improvement ratio and analyzed the intervening effect between the walls of the improved specimens.

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

• Journal of the Korean GEO-environmental Society
• /
• v.3 no.3
• /
• pp.15-25
• /
• 2002

The permeability coefficient is one of the fundamental engineering properties of soft clays. Consolidation process as well as migration of pollutants in soil are affected the permeability coefficient, which generally decreases with the reduction in void ratio during consolidation. After Kozeny(1927) and Carman(1956), many researchers have proposed the relationships between void ratio and permeability in such forms as; (1) log e - log k(1+e), (2) e - log k, or (3) log e - log k. Constant rate of strain (CRS) tests was performed with undisturbed samples obtained at Kunsan and Kimhae deposits, which are representative Korean marine clay. From the results of the tests, the relationships were found valid for Kunsan and Kimhae clays. The experimental correlation $C_k=0.5e_o$ was satisfied with Kimhae clay but not with Kunsan clay.