• Journal of the Korean Geotechnical Society
• /
• v.40 no.3
• /
• pp.19-31
• /
• 2024

In Korea, driven piles are generally penetrated up to weathered rock or harder strata. Friction piles have been used to some extent in the southwest coastal area with deep soils; however, friction piles are not extensively due to uncertainties about construction quality. The embedded pile construction method is primarily used due to noise and vibration complaints. However, in Southeast Asian countries (e.g., Cambodia, Myanmar, and Vietnam), where soft sediments are deep, the driven pile method is commonly used due to its economic advantages. Construction companies are increasingly entering overseas construction markets, e.g., Southeast Asia; thus, it is necessary to understand the behavior of driven friction piles in the soil and improve on-site engineering management to gain market competitiveness in these countries. In this study, the bearing capacity of friction piles driven into clayey coastal soils in Vietnam with time-dependent characteristics was evaluated based on the dynamic and static pile load tests. Based on the results, a modified Danish formula is proposed for on-site quality management.

• Journal of the Korean Geotechnical Society
• /
• v.17 no.6
• /
• pp.163-171
• /
• 2001

It is important to pay careful attention to the backfill construction for the structural integrity of concrete box culvert. To increase the structural integrity of culvert good compaction by the dynamic compaction roller with big capacity is as effective as good backfill materials. However structural distress of the culvert could be occurred due to the excessive earth pressure by great dynamic compaction load. In this study, two box culverts were constructed with change compaction materials and construction methods. Two type of on-site soils such as subbase and subgrade materials were used as backfill materials. In most case, dynamic compaction rollers with 11 to 12 ton weights were used and vibration frequency were applied from 2000 to 2500 rpm for the great compaction energy. Backfill compactions with good quality soils were carried out to examine the effect of cushions on dynamic lateral soil pressure. Expanded polystyrene (EPS) and rubber of tire were adapted as cushion materials and they are set on the culverts before backfill construction. This paper presents the main results on the characteristics of dynamic earth pressures. Test result indicates that the amounts of increased dynamic pressures are affected with backfill materials, depth of pressure cell, and compaction condition. The earth pressure during compaction can give harmful effect to box culvert because the value of dynamic earth pressure coefficient $(\DeltaK_{dyn}=\DeltaK\sigma_h\DeltaK\sigma_v)$ during compaction is greater than that of static condition. It was observed that cushion panels of EPS(t=10cm) and rubber(t=5cm) are effective to mitigate dynamic lateral pressure on the culverts.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.4D
• /
• pp.377-386
• /
• 2010

This study was conducted to find out the characteristics of the expanded road embankment constructed by the lightweight air-mixed soil (slurry density $10kN/m^3$) for a short-term without any ground improvement. Compression strength, capillary rise height of the lightweight air-mixed soil and settlement behavior of soft ground were studied. Compression strengths of the specimens sampled at the site after 1 and 5 months of construction were all satisfied the required strength 500 kPa. However, it was not convinced the homogeneity construction, because the values of strength were depending on the sampled location. Also, strength difference between laboratory and site specimens were found about 19%, and thus it should be considered for mixing design. Capillary rise reached about 20 cm for 70 hours because of a numerous tiny pores existed inside the lightweight air-mixed soil. Relationship between settlement and time of the soft ground placed underneath the expanded embankment was estimated by using the measured data and back analysis technique. The current average consolidation ratio and the final settlement after 120 months later were estimated about 32% and 4.5cm, respectively. This settlement is much less value than the allowable settlement 10cm for this structure.

• Journal of agriculture & life science
• /
• v.44 no.6
• /
• pp.27-37
• /
• 2010

This study was carried out to offer the basic information on ecological succession of evergreen broad-leaved forest through understanding of ecological characteristics of forest community by distance from Camellia japonica stand. Importance value of C. japonica at tree layer was highest in site I and those of Pinus densiflora and P. thunbergii were highest in site II, III and IV. At subtree layer, the importance value of C. japonica was highest in site I while Neolitsea sericea and Styrax japonica had the highest importance value in site II, III, and IV. In all sites, species diversity ranged from 0.121 to 0.515 and 1.112 to 1.589 at tree layer and subtree layer respectively. Evenness ranged from 0.811 to 0.930 at subtree layer, 0.796 to 0.913 at shrub layer and 0.155 to 0.727 at tree layer, this indicates that distribution pattern by species is more uniform at subtree and shrub layer than at tree layer. Soil pH was highest as 5.72 at site I. Contents of total N, organic matter and available P were higher at site I than other sites.

• Geotechnical Engineering
• /
• v.11 no.2
• /
• pp.139-156
• /
• 1995

A set of field investigations was performed to estimate accurately the predominant periods of seismic 8round motions and the attenuation characteristics of the seismic ground vibration. Predominant periods of ground motions were estimated from the measurement of the continuous microseismic vibratins of certain periods, inherent in the ground and in the buildings, utilizing the high sensitivity digital velocity seismometer consisting of 3-component geophones and a digital seismograph. Estimated predominant periods of microseismic vibraion of the ground(measured on'the ground surface) and the building (measured on the second floor) were in the range of 0.18~0.235 sec. and 0.26~0.31 sec. respectively. The subsurface structure of the site ground was surveyed by the seismic refraction method utilizing the digital seismicwave probing system. The ground structure was found to be a two-layered system : an upper top soil layer of 7m in thickness with the P-wave velocity of 662m1sec and a lower layer of silty-clayey soils with the P -wave velocity of 2210m1 sec. The attenuation characteristics of the seismic ground vibrations were determined by the amplitude decay measurement method us;ng the Seisgun, which produces strong artificial seismic energy. Measured spatial attenuation coefficients of the ground vibration in vertical(Z) longitudinal(X), transverse(Y) direction were 0.1137, 0.0025, and 0.0290 respectively. Estimated Spartial QP's (inverse of the specific dissipation constant w.r.t. shear waved of X, Y, and Z directions were in the range of 5.913~7.575, 32.371~41.452, 2.794~3.579 re spectively. This indicates that aseimic design of the structures on the site should take stronger consideration regarding the earthquake resistance characteristics of the structures against longitudinal ground motion.

• Journal of Korean Society for Atmospheric Environment
• /
• v.19 no.E4
• /
• pp.177-186
• /
• 2003

The total of 1,454 aerosol samples were collected by high volume tape sampler at the Gosan Site in Jeju Island from 1992 to 1999, and the major water-soluble ionic components were chemically analyzed. The mean concentrations of nss-S $O_4$$^{2-}$, N $H_4$$^{＋}$, and N $O_3$$^{[-10]}$ showed high values, which were 6.73, 1.45, and 1.45 ${\mu}{\textrm}{m}$/㎥, respectively, while $Ca^{2+}$ and $K^{+}$ concentrations were low with the values of 0.49 and 0.42 $\mu\textrm{g}$/㎥. The concentrations of most components increased in spring but decreased in summer, especially with the remarkable increase of $Ca^{2+}$ and N $O_3$$^{[-10]}$ concentrations in spring. The seasonal comparison of nss-S $O_4$$^{2-}$ concentrations showed higher values with the order of spring > fall 〉 winter〉 summer, but spring 〉 winter〉 fall 〉 summer for N $O_3$$^{[-10]}$ Meanwhile, the concentration levels of N $a^{+}$ and C $l^{[-10]}$ increased more in winter season. According to the investigation of wind direction effect, the concentrations of most aerosol ionic components showed higher values consistently at the westerly and northerly wind conditions. Based on the factor analysis, the atmospheric aerosols in the Gosan Site are considered to be largely affected by marine sources, followed by anthropogenic and soil sources.urces..

• Earthquakes and Structures
• /
• v.25 no.1
• /
• pp.27-41
• /
• 2023

This study focused on nonlinear effective stress site response analysis using two coupled constitutive models, that is, the DM model (Dafalias and Manzari 2004), which incorporated a simple plasticity sand model accounting for fabric change effects, and the PMDY03 model (Khosravifar et al. 2018), that is, a 3D model for earthquake-induced liquefaction triggering and postliquefaction response. A detailed parametric study was conducted to validate the effectiveness of nonlinear site response analysis and porewater pressure (PWP) generation through a true coupled formulation for assessing the initiation of liquefaction at ground level. The coupled models demonstrated accurate prediction of liquefaction triggering, which was in line with established empirical liquefaction triggering relations in published databases. Several limitations were identified in the evaluation of liquefaction using the cyclic stress method, despite its widespread implementation for calculating liquefaction triggering. Variations in shear stiffness, represented by changes in shear wave velocity (Vs1), exerted the most significant influence on site response. The study further indicated that substantial differences in response spectra between nonlinear total stress and nonlinear effective stress analyses primarily occurred when liquefaction was triggered or on the verge of being triggered, as shown by excess PWP ratios approaching unity. These differences diminished when liquefaction occurred towards the later stages of intense shaking. The soil response was predominantly influenced by the higher stiffness values present prior to liquefaction. A key contribution of this study was to validate the criteria used to assess the triggering of level-ground liquefaction using true coupled effective-stress constitutive models, while also confirming the reliability of numerical approximations including the PDMY03 and DM models. These models effectively captured the principal characteristics of liquefaction observed in field tests and laboratory experiments.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.03a
• /
• pp.445-454
• /
• 2006

Myungji Housing Complex is located in the Nakdong River plain in which the Busan soft clays are developed. It has thick soft soil laver of about GL(-)50m including loose sandy layers, upper and lower clayey layers. The clayey layers have been being consolidated since the land reclamation was completed to build the place for Housing Complex(Apartment) in 1997. Therefore, as one of a series of advance preparations of this project, study was carried on the geotechnical characteristics under the foundation The first part of this paper represents a brief geological history. Then, geotechnical characteristics of clay was analyzed in the classical developments in soft clay. They were based on the geotechnical data obtained by site investigations performed from 1992 to 2005. Finally, we evaluated the average degree of consolidation at this point in time and the residual settlements of upper clayey layer using dissipation and oedometer tests for this project

• International Journal of Highway Engineering
• /
• v.12 no.2
• /
• pp.71-79
• /
• 2010

The influence of fines of the frost susceptibility of subgrade soils were established by laboratory freezing system test simulating closely the thermal conditions in the field. During the winter season, the climate is heavily influenced by the cold and dry continental high pressure. Because of siberian air mass, the temperature of January is $-6{\sim}-7^{\circ}C$ on average. This chilly weather generate the frost heaving by freezing the moisture of soil and damage potential of the road structure. In the freezing soil, the ice lenses increase the freeze portion of soil by absorbing the ground water with capillary action. However, the capillary characteristics differ from the sort of soil on the state of freezing condition. In the current design codes for anti-freezing layer, the thickness of anti freezing layer is calculated by freezing depth against the temperature condition. Therefore, they have a tendency of over-design and uniform thickness without the considerations of thermal stability, bearing capacity and frost susceptibility of materials. So, it is essential for studying the appropriateness and bearing capacity besides the seasonal and mechanical properties of pavement materials to take a appropriate and reasonable design of the road structure. In this Paper, the evaluation of frost susceptibility was conducted by means of the mechanical property test and laboratory freezing system apparatus. The temperature, heaving amount, heaving pressure and unfrozen water contents of soil samples, the subgrade soils of highway construction site, were measured to determine the frost susceptibility.

• Korean Journal of Soil Science and Fertilizer
• /
• v.49 no.5
• /
• pp.531-540
• /
• 2016

The adoption of legume cover crops in no-tillage system can contribute to improve soil fertility by providing several benefits, including reduction in soil erosion, suppression of weed growth and N supply to subsequent crops. We conducted a field study to investigate the effect of cover crops and nitrogen fertilization rates on yield and nitrogen use efficiency of waxy corn (Zea mays L.) in no-tillage upland field. Two legume cover crops, hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnuturn L.) were mechanically terminated with roller in early June. For each cover crop treatment, nitrogen (N) fertilizer was applied at three different rates (145, 72.5 and $0kg\;N\;ha^{-1}$). The growth and yield characteristics of corn were significantly affected by the N fertilization rates in crimson clover plots, which suggest N mineralization from the cover crop residue was not sufficient. In contrast, N fertilization rates had no significant effect on growth and yield of corn in hairy vetch plots, indicating that the amount of N released from the cover crop is large enough to meet most of the N requirement of corn. However, the application of N fertilizer in hairy vetch cover plots resulted in slight increase of crop yield, though not statically significant, and high levels of N concentration in corn plant tissue possibly due to luxury consumption of N. Organic residues on the soil surface in hairy vetch cover plots had substantial amounts of N after harvest, ranging from 100 to $116kg\;N\;ha^{-1}$, which is presumably retained during winter season and released by microbial mineralization in subsequent year. The highest nitrogen yield efficiency was achieved in the plot with hairy vetch cover and no N fertilizer application, followed by the plot with hairy vetch cover and $72.5kg\;N\;ha^{-1}$ fertilization rate. In conclusion, hairy vetch showed better performance in corn productivity as compared with crimson clover. In addition, it was concluded that the application of N fertilizer between 0 and $72.5kg\;N\;ha^{-1}$ in combination with hairy vetch cover crop might be most efficient for corn yield under no-tillage system with climatic and soil characteristics similar to those of the experimental site.