• Journal of the Korean Geotechnical Society
• /
• v.19 no.4
• /
• pp.201-209
• /
• 2003

For the purpose of research study, a vertical shaft of 98m in length and 3.05m in diameter was constructed in the layer of conglomerate by using the Raise Boring Machine (RBM). In order to estimate the net penetration rate of the RBM, which can be used in the stage of design, the in-situ test results were analysed and correlated to data from the boring log in situ and laboratory testing. Its average net penetration rate is 2.233mm/rev while its average advance rate is 0.382m/hr, which is lower than that of TBM(Tunnel Boving Machine). It turns out that the net penetration rate increases with the increase of strength characteristics in rock mass (e.g., uniaxial compression strength, tensile strength, etc.). Similarly, the net penetration rate increases linearly with the hardness of rock mass. These results are contrary to the results of the previous construction sites where the TBM was generally used in the layer of hard rock. However, the trend obtained in this study is in accordance with the findings of Barton suggesting the relationship between Q$_TBM$ and penetration rate in the layer of soft rock. Thus, the trend is valid in soft and/or weathered rocks.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.4
• /
• pp.31-42
• /
• 2000

In this study, the stability of group piles installed in deep sea to the seaquake was studied by performing the calibration chamber model tests for open-ended pipe piles, grouted piles under soil plug and close-ended piles installed in the simulated deep sea. For each case (a single pile, 2-pile and 4-pile groups), series of seaquake tests were performed. While, during the simulated seaquake, the compressive capacity of the single open-ended pile depended on pile penetration depth(=7m), were found to be stable. But, a single grouted pile with penetration depth of 13m kept "mobility" state, the one with penetration depth of 20m was stable and grouted pile groups with penetration depth of 7m were stable regardless of pile penetration depth. By grouting soil plug of open-ended piles and soil under the pile toe of open-ended pipe piles installed in the deep sea, failure of soil plugging was prevented. Thus, close-ended piles were more stable than open-ended pile against the seaquake motionake motion.

• Journal of the Korean Geotechnical Society
• /
• v.27 no.2
• /
• pp.43-52
• /
• 2011

The characteristics of shear zone in granular soils largely affect the stability of geo-structures. The goal of this study is to evaluate shear zone in a direct shear test using shear wave, electrical resistivity, and cone tip resistance. Bender elements and electrical resistivity probe are embedded into the wall of a direct shear box made of transparent acrylic material to estimate the shear wave velocities and the electrical resistivity at shear and non-shear zones. At the point of peak and residual strength, micro cone penetration test which can be available to measure tip resistance has been performed. Experimental results show that the shear wave velocities at upper shear zone increase during shearing while the values remain constant at bottom and lower shear zone. Also, resistivities at lower shear zone depend on relative density while resistivities at bottom remain constant. The results of cone penetration test demonstrate the correlation of the cone tip resistance and small strain shear modulus at shear zone. This study suggests that the application of the modified direct shear box including shear wave, electrical resistivity and the micro cone tip resistance may become effective tools for analyzing the characteristics of a shear zone.

• Journal of the Korean Geosynthetics Society
• /
• v.9 no.4
• /
• pp.9-15
• /
• 2010

In this study, a non-open cut method using a round or square pipe which has been commonly employed in Korea was experimentally evaluated and the behavioral features resulting from the friction while the pipe is penetrated into the ground was identified through the scale model test. To that end, a test device was fabricated by type of penetration pipe, by which the surface displacement caused by surrounding friction resistance was monitored. To simulate the settlement and heaving by excavation stage, the test was conducted based on generalized friction condition and surface displacement and the result therof was compared and analyzed, considering the type of penetration pipe.

• Journal of the Korean Geosynthetics Society
• /
• v.16 no.1
• /
• pp.53-61
• /
• 2017

Seabed settlement and erosion sometimes occurr when a artificial reef is installed in soft seabed. Therefore, this study carried out CBR test and water tank settlement test to investigate settlement behavior of artificial reef according to reinforcement characteristics such as reinforced types and reinforced area. Soil types of ground are sand, silt and clay deposits. Three reinforced types were prepared: unreinforced, geogrid and hybrid bamboo mat(HBM) with different reinforced area. Laboratory test results indicated that reinforced artificial reef improved bearing capacity of ground and reduced settlement as reinforced area increased. Especially, reinforced HBM provided more bearing capacity and less settlement than reinforced geogrid.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.3C
• /
• pp.201-207
• /
• 2006

Soil tests are generally conducted using a membrane to measure a pore water pressure. However, it has also been recognized that the membrane penetrates into the specimen by the change of the confining pressure, and it results in the erroneous measurement in the pore water pressure and the volumetric strain. This study examined the effectiveness of the correction equation of the membrane penetration on the basis of the experimental data acquired during the isotropic unloading and the cyclic shear process using the hollow cylindrical shear test equipment. The results showed that the membrane penetration by the correction equation could be overestimated when the mean effective stress was lower than 20kPa in this study. The limitations originated from the sudden increase near the zero effective stress, and in order to prevent the overestimation in low effective stress condition, the use of the constant a was proposed in this study. Furthermore, the correction equation for the membrane penetration had to be applied carefully when the initial relative density was high and the density changes were occurred by the relocation of the soil particle by the liquefaction.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.3
• /
• pp.119-129
• /
• 2000

국내에서 가장 많이 사용되는 현장조사방법인 표준관입시험의 결과로 얻어지는 N값에 대해 가장 큰 영향을 미치는 롯드 에너지 전단률(깽 Energy Ratio)을 지반조건이 상이한 3개 현장에서 항타분석기(Pile Driving Analyzer)를 이용하여 실측하였다. 에너지 전달률에 영향을 미치는 요인들 중엣 해머의 종류, 로프의 상태, 자아틀에 감은 횟수 등의 조건을 달리하여 롯드 에너지 전달률에 미치는 영향을 측정/분석하였다. 실험결과에 의하면 도넛해머, 안전해머, 개량형 도넛해머(Modified Automatic Donut Hammer)는 롯드에너지 전달률이 각각42%, 66%, 57% 정도로 측정되었으며 로프의 상태와 자아틀에 감은 횟수는 상대적으로 영향이 적은 것으로 측정되었다. 실험결과를 바탕으로 실측된 N값을 해머의 이론적 위치에너지의 60%에 해당하는 에너지가 롯드에 전달되었을 때의 N값(N60)으로 변환하기 위한 식을 제안하였다.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.5
• /
• pp.123-132
• /
• 2003

The final purpose of driveability analysis is to confirm whether a selected hammer drives a pile to a desired penetration depth and/or capacity without damage. The capacities from static analysis methods are meaningless if the pile cannot be driven to the required design depth and the ultimate capacity without damage. It often occurs that there are big differences between the capacities from measurements and calculations. It may be because the driveability is not evaluated due to the lack of engineers' understanding of the driveability of pile driving. The engineers in the field sometimes assume simply the penetration depth with standard penetration value only. In this study some test pilings with dynamic pile loading tests were performed to give an understanding about the driveability. The influence factors(driving resistance, impedance, material strength, hammer) on the driveability of steel piles were analysed with the monitoring data obtained from the dynamic load tests. It was shown that more cost-effective design can be made in case the driveability analysis and high strength steel pile are appropriately adopted in the design.

• Geotechnical Engineering
• /
• v.11 no.4
• /
• pp.25-36
• /
• 1995

A specially designed model open -ended pile, which was composed of inner tube and outer tube, wry driven in the pressure chamber by two diffenent intallation methods, that is, impact -driving and vibratory driving, and static compression loading test was done for that pile. Through the measurement of bearing capacities in the separated resisting parts of open -ended pile, bearing mechanism of open-ended pile and soil plugging behaviors for different installation methods were studied. It appears that 20% out of soil plugging force of impact -driven pile was developed during driving, while the rest was developed during static compression loading and t.he magnitude of confining pressure applied to the chamber did not affect soil plugging behavior. Also. it appears that, soil plugging force of vibratory pile was not developed during driving, while it was developed weakly as about 0.5~0.7 times as that of impact pile during static compression loading. and the confining pressure of pressure rhamber had an effect on the soil plugging. In the ultimate loading condition unit soil plugging force did not approach to the failure condition.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.5C
• /
• pp.313-320
• /
• 2008

The discharge capacity testing apparatus using penetration method, being able to simulate in laboratory the condition of embedding plastic board drains in field, was developed to investigate consolidation characteristics of ground and to figure out discharge capacity of drains. The developed apparatus with a mandrel and penetrating device was designed to insert PBD into the ground prepared by previously applied pressure, being different from the conventional testing method that the drain was installed and the ground material was poured subsequently. Discharge capacity tests with the conventional apparatus as well as the newly developed one were performed to assess the applicability of the latter. As a result of tests, the conventional method showed delayed consolidation due to overall disturbance of ground and local deformation of drain caused by inhomogeneity of ground. Therefore discharge capacity of drain with the conventional apparatus was measured more or less larger than the expected values whereas discharge capacity with new one could be measured similar to the actual value in field.