• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.45-50
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• 2005

Sand pile method, such as sand drain method and sand compaction pile method, has been popularly used as an improved method for soft clay grounds. The effect of accelerating consolidation of soft clay grounds has been evaluated with Barren's solution. The consolidation behavior of soft clay ground with sand piles strongly depends on both the nonlinear mechanical interaction between sand piles and surrounding clays and the degradation permeability of clays. In this paper a method of determining consolidation parameters of soft clay ground with sand drains by using Barren's solution was proposed through a series of numerical simulations. Through the method, the change in both volume compressibility and permeability during consolidation was reasonably evaluated.

• Journal of the Korean GEO-environmental Society
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• v.13 no.10
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• pp.43-53
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• 2012

This study deals with the conventional consolidation methods like preloading and vertical drains. For it, Two different mechanism, i.e., increasing of permeability and evaporating of pore water were studied. The marine clays excavated in Incheon were heated at low temperature($90^{\circ}C$) to increase the permeability. Also, Microwave oven and high-temperature electric heater were used for pore water evaporation. Several points raised from the experiments. To fix them, the electric heating system was revised to upgrade the field application and drain efficiency of pore water, and the marine clays were heated by revised electric heater at high temperature($250^{\circ}C$). From Experimental result showed that results, high-temperature heater induced the pore water evaporation and displayed the excellent consolidation behavior. In addition, the cone index of heated clays were increased about 19 times, which suggested that electric heating system could be applied for ensuring the trafficability of heavy equipments.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.59-70
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• 2002

Horizontal drains are sometimes installed on the ground together with vertical drains in order to drain excess pore water. Taking into account the discharge capacity of horizontal drains, a new analytical method is developed in this paper, and then a new formula for the discharge capacity of horizontal drains is proposed. It is known from the analysis that the effect of the rate of surcharge loading is negligible in determining horizontal discharge capacity. This formula is described as the function of coefficient of consolidation, space of vertical drain, compression index, length of horizontal drains, and thickness of the compressible layer.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.5-11
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• 2007

This paper is to investigate the removal of the smear at elevated temperatures. This study utilized both small cylinder cell and large consolidometer apparatus to investigate the combination of PVD with heat and without heat. Two types of heaters are used in this study. The heater drain made of copper tube is used for all tests except large consolidometer and flexible wire heater is used for large consolidometer. Specimens demonstrated volume contraction upon heat and without heat. This contraction is dependent on temperature magnitude. When the specimen is heated, the magnitude of settlements is higher and rate of consolidation is faster. After treatment using PVD combined without heat and with heat for undisturbed specimens the $C_h$ values obtained were $3.45m^2/yr$ and $3.83m^2/yr$, respectively, from $3.2m^2/yr$ before treatment. The $K_h/K_s$ ratios were 3 for the specimen without heat and 2 for the specimen with heat. Similarly, in reconstituted specimens without heat and with heat, the $C_h$ values were $2.1m^2/yr$ and $2.5m^2/yr$ with $K_h/K_s$ ratios of 1.75 and 1.5, respectively.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.349-359
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• 2011

The consolidation behavior of soft clay is controlled mainly by its compressibility and deformation characteristics. Soil permeability depends on various soil characteristics, including the soil type and anisotropy. The coefficient of permeability of soft clay is determined by using a laboratory test (the Oedometer test) or a piezocone test. The latter test is useful for estimating the permeability characteristics from $c_h$ and $k_h$ by performing an excess pore-pressure dissipation test. This study seeks to validate an existing theoretical formula in applying it to marine clay, and to assess the relation between $k_h/k_c$ and the mechanical properties of soft clay. Piezocone tests and laboratory tests were performed using sediment from the Yellow Sea and from the South Sea near Korea. We compared $k_h/k_v$ values obtained using the piezocone test and using laboratory consolidation tests. The obtained values are similar to the values obtained by Jamiolkowski et al. (M application); therefore, the latter values are recommended to be used as $k_h/k_v$.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.47-54
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• 2011

Consolidation behavior of soft clay is generally to be affected by its compressibility and deformation characteristics. Especially, soil permeability depends on soil characteristics including its type of anisotropy. Coefficient of permeability of soft clay is mostly estimated by using laboratory(Oedometer test) and in-stiu piezocone test. The permeability characteristics of soft clay is estimated by excess pore pressure dissipation test results. In this study, the tests were performed to find out the validity of the existing theoretical formula in clay by pore pressure dissipation test and laboratory test results. After grasping of variation the coefficient of permeability ratio(${k_{h}/k_{v}}$) in different clay soils, it was found out adequate solution of in-stiu permeability ratio(${k_{h}/k_{v}}$). Piezocone tests and laboratory tests were performed at the site of pilot project of ground improvement at Yangsan-Mulgeum, Gyeongsangnam-do. Comparisons of the estimated values of ${k_{h}/k_{v}}$ using piezocone tests results and those from laboratory consolidation tests were carried out. Test results show that values of ${k_{h}/k_{v}}$ by piezocone test result(5.85) is similar of it's laboratory test(5.28).

• Geotechnical Engineering
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• v.12 no.4
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• pp.131-144
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• 1996

In order to accelerate the rate of consolidation settlement and to gain a required shear strength for a given soft clay deposit, the preloadina technique combined with a vertical drainage system has been widely applied. Even if a sophisticated numerical analysis technique is applied to solve the consolidation behavior of drainage-installed soft deposits, the actual field behavior is often different from the behavior predicted in the design state due to several uncertainties involved in soil properties, numerical modelling, and measuring system. In this paper, two back-analysis schemes such hs simplex and BFGS methods have been implemented in an a Bisymmetric consolidation program, AXICON which considers the variation of compressibility and permeability during the consolidation process. Utilizing the program, one might be able to appropriately predict the subsequent consolidation behavior from the measured data in an early stage of consolidation of drainage-installed soft deposits.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.129-138
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• 1999

This study is performed for the development of a field monitoring and test technique both of self-weight and hydraulic consolidation by which the soil parameters of dredge-reclaimed clay can be obtained effectively. The field monitoring development and tests mentioned above make it possible to reproduce the process of the self-weight consolidation from settling to reclaimed soft ground. The experimental research is mainly focussed on the characteristics of self-weight consolidation of dredged clayey soil. And theoretical study has pointed out the limits in the application of Terzaghi's one dimensional consolidation theory in interpreting reclaimed clayey ground. Furthermore, a finite difference analysis has been made on the basis of Mikasa s self-weight consolidation theory which takes the problems of Terzaghi's theory into consideration. The relationships between specific volume, effective stress, and the coefficient of permeability of Kunsan reclaimed clayey soil have been obtained by laboratory tests. On the other hand, through the field monitoring, pore pressure, total pressure, and water levels have been measured after pouring. The results of these experiments have been analyzed, and compared with those from Terzaghi's method and the finite difference analysis of Mikasa's self-weight consolidation theory. In conclusion, the measured settlements is comparatively consistent with Mikasa's self-weight consolidation theory rather than Terzaghi's consolidation theory.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.169-178
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• 2002

The stress~strain characteristics of geosynthetics reinforced clayey soil were investigated by triaxial compression tests. All the tests were peformed either on unreinforced or reinforced soils under fully drained condition after having been consolidated isotropically or anisotropically to the required level of effective stresses by the small increment of 0.05kgf/$cm^2$. The anisotropically consolidated drained tests were performed to simulate the in-situ condition of reinforced soil structures such as reinforced soil wall, abutment and embankment which are generally in the anisotrpic state. From a series of tests it was ffund that the behavior of the anisotropically consolidated reinforced clayey soils was very different from stress~strain characteristics of consolidated reinferced clayey soils. It was found especially that the initial Young's moduli of anisotropically consolidated reinforced clayey soils were higher than those of isotropically consolidated reinforced clayey soils. It was found also that the reinforcement effect in anisotropically consolidated reinforced soils developed at a much lower level of axial strain(0.01%) compared with isotropically consolidated ones(about 1.0~5.0%).

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.4
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• pp.48-58
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• 1992

This study was conducted to investigate the consolidation characteristics of the marine clay, treated with predetermined ratios of lime and briquette ash. The standard consolidation test was performed for the sample of mixture remoulded under the condition of optimum moisture content. The results obtained were as follows ; 1.The increase of the consolidation coefficient due to load increament was larger in the lime treated soil and briquette ash treated soil than in the untreated soil. The decrease of the compression index due to admixing ratio of additives was smaller in the former than in the latter. 2.The increase of the secondary consolidation coefficient of the untreated soil due to load increment was minimal, while that of lime treated soil and the lime-briquette ash treated soil was conspicuous and that of briquette ash treated soil was slight. 3.The $C\alpha$/Cc relationship of untreated soil was represented by colsely distributed points. That of briquette ash treated soil, lime treated soil and the lime-briquette ash treated soil was represented by linear distribution. The $C\alpha$/Cc values of untreated soil, briquette ash treated soil and lime treated soil were approximately 0.049, 0.044 and 0.031, respectively. 4.The maximum consolidation coefficient was obtained with lime and briquette ash (lime : briquette .h 2 :1) mixture ratio of 15%. And the minimum secondary consolidation coefficient, compression index was obtained with same mixture ratio. The required quantity of lime could be reduced and the consolidation was accelerated by applying the above mixture ratio.