• Fisheries and Aquatic Sciences
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• v.11 no.2
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• pp.103-112
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• 2008

Compressional sound velocities of shelf sediments in the South Sea of Korea, were measured in situ and in the laboratory for six cores. In situ sound velocity was measured using the Acoustic Lance (frequency of 7.5-15 kHz), while laboratory velocity was measured by the pulse transmission technique (frequency of 1MHz). Physical properties were relatively uniform with sediment depth, suggesting little effect of sediment compaction and/or consolidation. Average in situ velocity at each core site ranged from 1,457 to 1,488 m/s, which was less than the laboratory velocity of 1,503 and 1,604m/s. In muddy sediments the laboratory velocity was 39-47 m/s higher than in situ velocity. In sandy sediments, the difference was greater by an average of 116 m/s. Although the velocity data were corrected by the velocity ratio method based on bottom water temperature, the laboratory velocity was still higher than the in situ velocity (11-21 m/s in muddy sediments and 91 m/s in sandy sediments). This discrepancy may be caused by sediment disturbance during core collection and/or by the pressure of Acoustic Lance insertion, but it was most likely due to the frequency difference between in situ and laboratory measurement systems. Thus, when correcting laboratory velocity to in situ velocity, it is important to consider both temperature and frequency.

• Journal of the Korean earth science society
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• v.37 no.7
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• pp.408-419
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• 2016

To investigate the in-situ sound velocity of sediment in the southwestern part of the East Sea, the laboratory sound velocity was measured using the pulse transmission technique. The sediment sound velocity measured in laboratory was corrected to in-situ sound velocity based on the seafloor temperature, seawater sound velocity, Kim et al. (2004) model, and Hamilton (1980) model. The distribution of the corrected in-situ sound velocity applying Kim et al. (2004) and Hamilton (1980) models reflects the characteristics of sediments of the study area and shows a similar distribution pattern. The correction for in-situ sound velocity was mostly influenced by seafloor temperature. Then, correction of sound velocity using seafloor sediment temperature data should be accomplished for conversion of laboratory data to in-situ sound velocity.

• Smart Structures and Systems
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• v.7 no.4
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• pp.289-302
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• 2011

In marine clay deposits, naturally formed or artificially reclaimed, the evaluation and monitoring of the consolidation process has been a critical issue in civil engineering practices due to the time frame required for completing the consolidation process, which range from several days to several years. While complementing the conventional iconographic method suggested by Casagrande and recently developed in-situ techniques that measure the shear wave, this study suggests an alternative experimental procedure that can be used to evaluate the consolidation state of marine clay deposits using the shear wave velocity. A laboratory consolidation testing apparatus was implemented with bimorph-type piezoelectric bender elements to determine the effective stress-shear wave velocity (${\sigma}^{\prime}-V_s$) relationship with the marine clays of interest. The in-situ consolidation state was then evaluated by comparing the in-situ shear wave velocity data with the effective stress-shear wave velocity relationships obtained from laboratory experiments. The suggested methodology was applied and verified at three different sites in South Korea, i.e., a foreshore site in Incheon, a submarine deposit in Busan, and an estuary delta deposit in Busan. It is found that the shear wave-based experimental procedure presented in this paper can be effectively and reliably used to evaluate the consolidation state of marine clay deposits.

• The Journal of Engineering Geology
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• v.16 no.1 s.47
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• pp.1-14
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• 2006

Various measurements were carried out to estimate the modulus of deformation in two dominant rock types in Korea: granite and gneiss. Four most commonly used methods were utilized: Goodman jack tests, PS well logging, laboratory ultrasonic tests and laboratory uniaxial loading tests. Laboratory static and dynamic Young's moduli depend on the magnitude of the applied axial stress, range of Sequency used for measurement and the loading/unloading condition. As the laboratory measurement condition approaches to that in situ, the resultant moduli also appear to be comparable to that in situ. This suggests that the simulation of in situ stress condition is important when the modulus of rock is determined in the laboratory Dynamic Young's modulus is generally higher than static Young's modulus because of (micro)crack behavior in response to the stress, different range of frequency used for measurements, and the effect of the amplitude of deformation. Understanding of the relations in moduli from different measurement methods will help estimate appropriate in situ values.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.619-626
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• 2002

In this study, a correlation among pressure, time and quantity of injection was organized from the laboratory tests, which were executed many times representing in-situ soil conditions carefully and then it would be applied to the in-situ soil injection simulator which will be developed for optimal injection into the ground. The sort of sample soils were both sand(A specimen) and silty sand(B specimen). Injection tests were gone into operation by compaction state, injection velocity and the depth individually. In the ground improved with permeation Infection, the relation among injection pressure of the same depth, the injected quantities and time were systematic by the depth. By defining the limit range of injection pressure and quantity about the variety of a linear equation obtained from lining each of their trend, the application of laboratory injection monitoring program and the data to evaluate its realization were produced. In the ground improved with root type injection, the relation between injection pressure and the injected quantities was irregular because fracture state occurred quickly.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.607-616
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• 2006

More strict construction control of railway roadbeds is demanded in high speed railway system because of heavier repeated dynamic loading than conventional railways. The aim of this study is to propose a compaction control methodology of crushed-rock-soil-fills including as large particles as $200\sim300mm$ in diameter, which are easily encountered in high speed railway roadbed. Field tensity evaluation and in turn compaction control of such crushed-rock-soil-fills are almost impossible by conventional methods such as in-situ density measurements or plate loading tests. The proposed method consists of shear wave measurements of compaction specimens in laboratory and in-situ measurements of fills. In other words, compaction control can be carried out by comparing laboratory and field shear wave velocities using as a compaction control parameter. The proposed method was implemented at a soil site in the beginning and will be expanded to crushed-rock-soil-fills in future. One interesting result is that similar relationship of shear wave velocity and water content was obtained as that of density and water content with the maximum value at the optimum moisture content.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.25-35
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• 2001

For the ground resrxmse analysis, both in-situ and laboratory testing techniques such as downhole, SASW, resonant column and torsional shear tests were perlormed for Hong-Seong area. The grOlmd upper 30m is classified as SD since it has an average shear wave velocity as 209m/s. The response specLrums obtained by site-specific analyses generally satisfied the seismic code, but near the resonance period the motion was evaluated to be higher than the code.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.5
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• pp.93-105
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• 2001

The permeability of converter slag, replacing material of sand mat on improving soft clay foundation, was evaluated in the laboratory as well as in situ test. Effects of grain size, flow water time and aging were investigated using sea and fresh water Converter slag which has a grain size less than 10mm were submerged with fresh water and sea water. In fresh water, the coefficients of permeability in samples A and B were measured as 4.50${\times}$10$^{-2}$ cm per second and 1.20${\times}$10$^{-1}$ cm per second, respectively while as 1.88$\times$10$^{-2}$ cm per second and 3.86$\times$10$^{-1}$ cm per second in sea water. The condition of turbulent flow may exit and was experimentally certified based on the relationship of hydraulic gradient and seepage velocity. After 180 days in using sea water, the coefficients of permeability of samples A and B decreased ten times smaller than those initial values, and after that time continually decreased as for till 360 days. Finally, filling with voids in high-calcium quicklime(CaO) may result in the reduction of coefficient of permeability. In-situ coefficient of permeability however was Practically satisfactory.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.114-119
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• 1992

The main disadvantages of destructive testing methods are the delay in obtaining test results, the relatively high cost of testing, and the lack of reproducibility in the test results. As a result, nondestructive testing methods are generally used. There are three objectives in this paper. The first is to determine the equations of the compressive strength of concrete estimated by Schmidt hammer technique, ultrasonic pulse velocity method and combined method respectively in laboratory. The second is to determine the correction factors according to the concrete age which affects most in evaluating the compressive strength of in-situ concrete. The third is to examine the applicability of the equations to evaluation of the compressive strength of in-situ concrete structures.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.119-126
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• 2008

Ground stiffness(shear wave velocity) is one of the key parameters in geotechnical earthquake engineering. An In-situ seismic technique has its own advantages and disadvantages over the others in stiffness measurements. By combining the crosshole and seismic cone techniques and utilizing favourable features of bender elements, a new hybrid probe has been developed in order to enhance data quality and easiness of testing. The basic structure of the probe, called "MudFork", is a fork composed of two blades, on each of which source and receiver bender elements were mounted respectively. To evaluate the disturbance caused by the penetration of the probe, shear wave velocity measurements were carried out in the Kaolinite slurry in the laboratory. Finally, the probe was penetrated in coastal mud near Incheon, Korea, using SPT(standard penetration test)rods pushed with a routine boring machine and shear wave velocity measurements were carried out. The results were verified with data from laboratory and cone testing. The performance of the probe turns out to be excellent in terms of data quality and testing convenience.