• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.597-604
• /
• 2002

This paper reviews depositional environments of marine deposits along the Nakdong river and then analytical solution of self-weight consolidation considering artesian pressure is made to find consolidated state. It's known that this area is in the under-consolidated state by the artesian pressure(u$\_$a/=0.3kg/$\textrm{cm}^2$) and the distribution of the artesian pressure is not linear but parabola. In predicting consolidation settlement for soft grounds improved by vertical drain, it is emphasized that the self-consolidation by sudden dissipation of artesian pressure should be considered.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.20 no.3
• /
• pp.4750-4770
• /
• 1978

Under the various variations of the sample thickness, the load increment ratio and the load increment duration, this consolidation test of the clay in the Asan Bay was tried for the comparison with the standard consolidation test. The results gained are as follows; 1. The void ratio variations of the leached-clay samples were increasingly high, according as the sample thickness thinned and the load increment duration and the laod increment ratio increased. 2. The coefficient of consolidation were increased with the increment of the sample thickness, of the load increment ratio and of the load increment duration. Near the pre-consolidation load, the coefficient of secondary consolidation had the maximum value and lessened with the increment of the sample thicknss, and of the load increment duration 3. The value of the pre-consolidation load increased in proportion to the increment of the sample thickness and the decrease of the load increment ratio and the load increment duration. 4. The compression indices increased as the increment of load increased and decreased as the sample thickness increased. 5. The initial compression ratio increased as the sample thickness, the load increment ratio and the load increment duration decreased. The ratio of primary compression to the secondary decreased with the increment of the sample thickness and of the load increment ratio. 6. The time at the completion of psimary consolidation increased with the increment of the sample thickness and of the consolidation load, and with the decrease of the load increment ratio. 7. The compression indicses increaed as the sample thickness lessened and decreased as the load increment ratio increased. The coefficient of consolidation increased according as the sample thickness, the load increment ratio and the load increment duration went up. The settlement at the construction site should be calculated highly in proportion as the sample thickness lessened and the load increment ratio increased. The consolidation ratio is thought to be accelerated if the sample thickness and the load increment ratio becomes higher and the load increment duration longer.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.495-508
• /
• 2010

Vertical drains are commonly used to accelerate the consolidation process of soft soils, such as dredged materials. The installation of vertical drain provides a radial drainage path to water in the deposit soil in addition to the vertical direction. An estimation of time rate of settlement is considerably complicated when vertical drains are installed to enhance consolidation process of dredged material because the vertical drains are commonly installed before self-weight consolidation is ceased. In this paper, the vertical drain theory developed by Barron(1948) is applied to analyze the non-linear consolidation behavior considering radial drainage. The overall average degree of self-weight consolidation of the dredged soil under the condition that the water is drained in both radial and vertical directions is estimated using the Carillo(1942) formula. In addition, the Morris(2002) theory and the one-dimensional non-linear finite strain numerical model, PSDDF, are applied to analyze the self-weight consolidation in case of only the vertical drainage is considered. The new analysis approach proposed herein can simulate properly the time rate of the self-weight consolidation of dredged materials that is facilitated with vertical drains.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.64 no.2
• /
• pp.85-96
• /
• 2022

The study is aimed to investigate the features and socio-economic background of farmland consolidation project with medium-sized paddy plot at irrigation associations during the Japanese colonial period in Korea. Most of farmland consolidation works in the 1940s was composed of independent irrigation and drainage ditches along the short side of field plot. However, the number of farm roads at farmland consolidation zone was much smaller than number of irrigation ditches to decrease reduction in farmland area. The standard field plot was medium-sized (about 20-40 ares) in Korea but small-sized (about 10 ares) in Japan in this period. As the result of farmland consolidation works, the unit water requirement was increased to 0.0035 m³/s/ha, and the unit area drainage discharge was over 2.0 m³/s/km² in many cases. The farmland consolidation with medium-sized plot have been spread under the colonial landlord system, where major landlords occupied a large share of farmland and managed corporate farming to gain more benefit. The reasons for spread of farmland consolidation with medium-sized plot may be as follows: high net profit ratio, an increase in land price, and labor savings in rice farming. The farmland consolidation with medium-sized plot in the colonial period showed intermediate features between the farm consolidation with small-sized plot for an increase in land productivity in Japan and the farm consolidation with medium-sized plot for an increase in labor productivity after the 1960s.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.5C
• /
• pp.201-208
• /
• 2010

In this study, the ground settlement was investigated by using monitoring data of the test sites where vacuum consolidation method and surcharge method were applied for improving deep soft soil. The monitoring data are chosen in ${\bigcirc}{\bigcirc}$ area port construction site reclaimed with very soft dredged clay. These data are analyzed to compare the consolidation characteristics between the different loading methods for soil improvement. Through analysis of the loading time, it is shown that the ground settlement reaches its allowable value under vacuum consolidation loading by about 45% faster than that of the surcharge loading consolidation. This could be explained that vacuum consolidation method makes the isotropic consolidation condition so that the time for reaching a certain final preloading without soil failure can be shortened.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.52 no.2
• /
• pp.1-9
• /
• 2010

This study was carried out to comparison of coefficient of consolidation and the prediction of excess pore water pressure in agricultural reservoir on soft clay ground. For the purpose of verification of the proposed equation, laboratory model tests and field tests were performed and excess pore water pressure was compared to those predicted with the Terzaghi's method. The predicted excess pore water pressure according to ponding was very applicable to practice because it was close to the observed data. Also, for the comparison of coefficient of consolidation, the oedometer, constant rate of strain (CRS), and Rowe cell tests were performed. The coefficient of consolidation at the Rowe cell and CRS tests showed a greate increase than in the oedometer test. The ratio of the vertical and horizontal coefficient of consolidation showed a large difference according to various tests method and mixing ratio. Therefore, it is recommended that careful attention should be paid to predicting the required consolidation period in agricultural reservoir.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.1-6
• /
• 2008

When a saturated clay is sampled in an undisturbed manner from a bore hole, the sample extends vertically and shrinks horizontally under undrained conditions due to stress release. The conventional consolidation test specimen is trimmed from the expanded sample so that its diameter is equal to the inner diameter of the consolidation test ring, this test procedure does not reproduce the actual consolidation behavior. The measurement of sample extension was conducted by means of overcoring method found that the extension strains were 1 to 2%. To simulate the in-situ consolidation behavior, the consolidation test method that uses a specimen with a slightly smaller diameter than the inside diameter of consolidometer so that the specimen expands laterally to the inside of the ring.

• Current Research on Agriculture and Life Sciences
• /
• v.2
• /
• pp.98-108
• /
• 1984

Generally, in case of constructing the embankments on the soft clay layers, one-dimensional consolidation settlement under the assumption of a middle position stress in a single layer makes a great difference with the integral value, ie. the final settlement. Consequently, to find how many equal segments of the soft clay layer are needed to converge into the integral value and which position should be taken as a position of mean stress, authors compared the theoretical value of the settlement due to one-dimensional consolidation with the practical value of the settlement due to two dimensional consolidation. The obtained results are as follows. 1) The practical value of the two-dimensional consolidation settlement can be estimated by the 74-83% theoretical value of the one-dimensional consolidation settlement. 2) When the soft clay layer was cut into 8-16 equal segments according to the depth, one-dimensional consolidation settlement converge into the integral value. 3) Assuming a total soft clay layer as a single one, the depth of a mean stress position is 0.29-0.37 of the thickness of the total soft clay layer. 4) The Hyperbola Method which presumes the long-term settlement from the short-term practical value of settlement is credible, because all practical value of the settlement are in safe side of the standard error of estimation and the correlation coefficient is up to 0.95.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.11a
• /
• pp.53-80
• /
• 2002

Settlement in the Shallow Foundation are presented. Various practical methods to calculate immediate settlement, consolidation settlement, and secondary compression of the compressive soils under the shallow foundation are summerized. Especially the critical depth for settlement calculation, the contact pressure, the allowable settlement of the shallow foundation are recommended.

• Geomechanics and Engineering
• /
• v.6 no.2
• /
• pp.173-194
• /
• 2014

Laboratory and field data showed that deep mixed (DM) columns accelerated the rate of consolidation of the soft foundations. Most analyses of consolidation of DM column-improved foundations so far have been based on the elastic theory. In reality, the DM columns may yield due to the stress concentration from the soft soil and its limited strength. The influence of column yielding on the degree of consolidation of the soft foundation improved by DM columns has not been well investigated. A three-dimensional mechanically and hydraulically-coupled numerical method was adopted in this study to investigate the degree of consolidation of the DM column foundation considering column yielding. A unit cell model was used, in which the soil was modeled as a linearly elastic material. For a comparison purpose, the DM column was modeled as an elastic or elastic-plastic material. This study examined the aspects of stress transfer, settlement, and degree of consolidation of the foundations without or with the consideration of the yielding of the DM column. A parametric study was conducted to investigate the influence of the column yielding on the stress concentration ratio, settlement, and average degree of consolidation of the DM column foundation. The stress concentration ratio increased and then decreased to reach a constant value with the increase of the column modulus and time. A simplified method was proposed to calculate the maximum stress concentration ratios under undrained and drained conditions considering the column yielding. The simplified method based on a composite foundation concept could conservatively estimate the consolidation settlement. An increase of the column modulus, area replacement ratio, and/or column permeability increased the rate of consolidation.