• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.913-922
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• 2009

Fourteen model pile load tests using a calibration chamber and instrumented model pile were preformed to investigate the variation of the behaviors of driven piles in sands with soil and lateral cyclic loading conditions. Results of the model tests showed that the first loading cycle generated more than 70% of the pile head rotation developed for 50 lateral loading cycles. Lateral cyclic loading also made an increase of the ultimate lateral load capacity of piles for $K_0$=0.4 and an decrease for $K_0$ higher than 0.4. Higher portion of the increase or decrease in the ultimate lateral load capacity by lateral cyclic loading was generated for the first loading cycle due to densification of loosening of the soil around the pile by lateral cyclic loading. It was also observed that a two-way cyclic loading caused higher ultimate lateral load capacity of driven piles than a one-way cyclic loading. When the pile was in the ultimate state, the maximum bending moment developed in the pile increased with increasing $K_0$ value of soil and was insensitive to the magnitude and number of lateral cyclic loading.

• Journal of the Korean Geotechnical Society
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• v.37 no.4
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• pp.39-47
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• 2021

Recently, the enzyme-induced carbonate precipitation (EICP) technique has been considered as one of the alternatives to the cement-based soil reinforcing method. However, the problem with the emission of ammonium ion has not been solved. In this study, an experimental study on the EICP without releasing an environmental contaminant (Ze-EICP) is performed using calcium-exchanged zeolite. The results show that the Ze-EICP using calcium-exchanged zeolite reduced the amount of ammonium ions by 96.96% and precipitated almost the same amount of calcium carbonate, compared to the EICP using calcium chloride. In addition, the Ze-EICP shows higher strength improvement rate than the EICP due to densification of zeolite and cementation of calcium carbonate.

• Geomechanics and Engineering
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• v.19 no.1
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• pp.79-91
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• 2019

Renewed interest in the long-term pile foundations has been driven by the increase in offshore wind turbine installation to generate renewable energy. A monopile subjected to repetitive loads experiences an evolution of displacements, pile rotation, and stress redistribution along the embedded portion of the pile. However, it is not fully understood how the embedded pile interacts with the surrounding soil elements based on different pile geometries. This study investigates the long-term soil response around offshore monopiles using finite element method. The semi-empirical numerical approach is adopted to account for the fundamental features of volumetric strain (terminal void ratio) and shear strain (shakedown and ratcheting), the strain accumulation rate, and stress obliquity. The model is tested with different strain boundary conditions and stress obliquity by relaxing four model parameters. The parametric study includes pile diameter, embedded length, and moment arm distance from the surface. Numerical results indicate that different pile geometries produce a distinct evolution of lateral displacement and stress. In particular, the repetitive lateral load increases the global lateral load resistance. Further analysis provides insight into the propagation of the shear localization from the pile tip to the ground surface.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1173-1180
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• 2006

In this study, aluminum electrodes were put in marine clay which was taken from the south coast in Korea to increase the undrained shear strength by inducing the densification and cementation between clay particles and precipitates which were developed by electric decomposition in an electrode. To raise the cementation rate and reduce treatment time, high electric current (2.5A) was applied in each electrode at a semi-pilot scale soil box with marine clay. After the tests, the undrained shear strength was measured at designated points using a static cone penetration test device and sampling was conducted simultaneously in order to measure water content, pH and electric conductivity which would be the key for configuring the cementation effects indirectly. In the results of electric decomposition in aluminum electrode, the measured shear strength was increased considerably compared to the initial shear strength because of the cementation effect between iron ions and soil particles.

• Journal of the Korean Society for Railway
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• v.2 no.4
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• pp.9-19
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• 1999

The use of compaction grouting evolved in 1950's to correct structural settlement of buildings. Over the almost 50 years, the technology has been developed and is currently used in wide range of applications. Compaction grouting, the injection of a very stiff, 'zero-slump' mortar grout under relatively high pressure, displaces and compacts soils. It can effectively repair natural or man-made soil strength deficiencies in variety of soil formations. Major applications of compaction grouting include densifying loose soils or fill voids caused by sinkholes, poorly compacted fills, broken utilities, improper dewatering, or soft ground tunneling excavation. Other applications include preventing liquefaction, re-leveling settled structures, and using compaction grout bulbs as structural elements of minipiles or underpinning. In this paper, on the basis of the case history constructed in this year, a study has been performed to analyze the basic mechanism of the compaction grouting. Also, the effectiveness of the ground improvement and the bearing capacity of the compaction pile has been verified by the Cone Penetration Test(CPT) and Load Test. Relatively uniform compaction grouting column could be maintained by planning the quality control in the course of grouting. And, the Qualify Control Plan has been conceived using grout pressure, volume of grout and drilling depth.

• Geomechanics and Engineering
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• v.33 no.4
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• pp.341-352
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• 2023

Long-short pile composite foundations bear both vertical and horizontal loads in many engineering applications. This study used indoor model tests to determine the horizontal bearing mechanism of a composite foundation with long and short piles under horizontal loads. A custom experimental device was developed to prevent excessive eccentricity of the vertical loading device caused by the horizontal displacement. ABAQUS software was used to analyze the influence of the load size and cushion thickness on the horizontal bearing mechanism. The results reveal that a large vertical load leads to soil densification and increases the horizontal bearing capacity of the composite foundation. The magnitude of the horizontal displacement of the pile and the horizontal load borne by the pile are related to the piles' positions. Due to different pile lengths, the long piles exhibit long pile effects and experience bending deformation, whereas the short piles rotate around a point (0.2 L from the pile bottom) as the horizontal load increases. Selecting a larger cushion thickness significantly improves the horizontal load sharing capacity of the soil and reduces the horizontal displacement of the pile top.

• Journal of the Korean Geotechnical Society
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• v.22 no.1
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• pp.25-34
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• 2006

In this study an effective stress numerical procedure is used to assess the results of dynamic centrifuge tests under high effective stress. The centrifuge models consist of loose Nevada sand with an initial vertical effective stress of 380kPa at depth, and they are modeled as a one-dimentional soil column. Liquefaction occurred up to 37m or 22m at depth, and the onset of liquefaction triggering was opposite to the conventional liquefaction evaluation procedure. In other words, liquefaction occurs first at the top and propagates downward as shaking continues. The results observed in centrifuge tests are reasonably predicted by the effective stress model. It is noted that the degree of initial saturation and additional densification at depth arising from the application of the high acceleration field play a key role in capturing the results of dynamic centrifuge tests.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2C
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• pp.89-98
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• 2006

In this study, the iron and aluminium electrode was put in marine clay which was taken from south coast in Korea to increase the undrained shear strength by inducing the densification and cementation between clay particles and precipitation which was developed by electrode decomposition. For raising the cementation rate and reducing treatment time, high electric current( 2.5A) was applied in each electrode at semi-pilot scale soil box with marine clay. After the tests, the undrained shear strength was measured at designated points using cone penetration test device and sampling was conducted simultaneously in order to measure water content, pH and electric conductivity which would be the key for configuring the cementation effects indirectly. The iron electrode decomposition test results show that the water content adjacent to anode section decreased in 35% and increased in 13% at cathode section. The measured shear strength however, was increased considerably comparing to initial shear strength because of cementation effect between iron ions and soil particles. In case of aluminium electrode decomposition test, the distribution of measured shear strength and degree of improvement were more homogeneous than iron electrode decomposition test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1C
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• pp.29-38
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• 2011

The smaller diameter cone penetrometer has been widely used to estimate the characteristics of local area due to high vertical resolution. The half-bridge cirucits have been adopted to measure the mechnical strength of soil through the smaller diameter cone penetrometer due to the limitation of the areas for configuring the full-bridge circuit. The half-bridge circuit, however, is known as being easily affected to the temperature variation. The objective of this study suggests the temperature-compensated method in mini-cones. The diameter and length of the mini-cone is designed to 15mm and 56mm. The load cell of the mini-cone is extended about 54mm on the behind of the mini-cone to reflect the only temperature variation. The full-bridge circuit is installed to measure the temperature-compensated values in the mini-cone and the half-bridge circuit is also organized to compare the temperature compensated values with uncompensated values. The seasonal variation tests are performed to define the effect of temperature variation under summer and winter temperature condition. The densification tests are also carried out to investigate temperature effects during penetration. The measured mechanical resistances with temperature-compensated method show more reliable and reasonable values than those measured by thermal uncompensated system. This study suggests that the temperature-compensated method of the mini-cone may be a useful technique to obtain the more reliable resistances with minimizing the temperature effect.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4863-4868
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• 2012

Static pile load tests were conducted on the two piles which comprised group pile installed in sand and the test results were compared with those obtained from load transfer method. Predicted load bearing capacity of the pile which locates center portion of the group pile was less than that from the load test and the reason is thought to be the densification of the soil due to the installation of the group pile. Predicted pile capacity of the API method, Coyle and Sulaiman method were 77%, 90% of the bearing capacity obtained from the load test, respectively. Comparing ultimate bearing capacities of the pile locating at the edge of the group pile, those predicted by the API method, Coyle and Sulaiman method were 1.1 times, 1.3 times of the bearing capacity obtained from the pile load test, respectively.