• Journal of the Korean GEO-environmental Society
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• v.16 no.7
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• pp.35-42
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• 2015

Grouting method has been widely used for the ground improvement and stabilization: mostly to block or control the ground water in the early years and to improve the ground, repair the structure in recent years, ever increasing its use. Despite many advantages so far, the existing grouting method also has some shortcomings including uncertain permeation of grouting with gravity type if the voids between the soil particles are narrow, and problems due to the relaxation of the neighboring ground when injected using injection pressure. As an alternative, a vibration injection method with constant amplitude and frequency has been developed in recent years, with the vibration grouting being reported to have a permeability increasing effect of grout material compared with the positive pressure injection type. Accordingly, the purpose of this study is to investigate the improvement effect of the vibration grouting that applies short-period vibration energy by varying vibration cycle, vibration time and ground conditions to evaluate the strength enhancing effect of grouting materials, expansion effect of grouting body, ground improvement effect of the grouting and the penetration characteristics of the rock joint. The findings of this study show the improved compressive strength of grout, expansion of grouting body and increased penetration rate, according to the vibration compared with non-vibration under the loose soil condition.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1075-1082
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• 2008

Recently, coal ashes which are increasing annually are buried in ash ponds as industrial wastes. However, buried coal ashes can pollute ground water and ground due to leachate from coal ashes, which are serious environmental problem. Even though a lot of researches on recycling of coal ashes have been conducted, only 15% of coal ashes are recycled up to now. And those recycled coal ashes are not bottom ashes but fly ashes. So in this study, it was proved that Bottom Ash can be used as an alternative material to O.P.C(Ordinary Portland Cement) according to laboratory test results and test field construction. Also bottom ash is more economical and environmentally friendly than O.P.C.

• Korean Journal of Agricultural Science
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• v.37 no.1
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• pp.97-104
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• 2010

In this study, a laboratory model test on utilization of recycled aggregates and crushed stone as vertical drains to use alternative material of sand in soft ground is performed. The vertical and horizontal coefficient of permeability of the recycled aggregates and crushed stone showed largely 1.2~4.0 times and 3.0~3.3 times greater than sand, respectively. Therefore, it showed enough to be an alternative material to the sand which had been being used as the vertical and horizontal drainage material before. The variations of pore water pressure with time showed constantly regardless of the load in all vertical drainage materials. When water level drops suddenly, the pore water pressure of the recycled aggregate and crushed aggregate is reduced to nearly zero. Therefore, it was applicable to the field because discharge capacity was similarity to that of sand. The settlement in crushed aggregates and recycled aggregate decreases gradually with the load increase. When water level drops suddenly, earth pressure in all drains materials was evaluated the equivalent drainage capacity similarity to sand because it show approaching the nearly zero.

• Geomechanics and Engineering
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• v.18 no.1
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• pp.59-69
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• 2019

Grout injection is mainly used for permeability reduction and/or improvement of the ground by injecting grout material into pores, cracks, and joints in the ground. The oscillatory grout injection method was developed to enhance the grout penetration. In order to verify the level of enhancement of the grout, field grout injection tests, both static and oscillatory tests, were performed at three job sites. The enhancement in the permeability reduction and ground improvement effect was verified by performing a core boring, borehole image processing analysis, phenolphthalein test, scanning electron microscopy analysis, variable heat test, Lugeon test, standard penetration test, and an elastic wave test. The oscillatory grout injection increased the joint filling rate by 80% more and decreased the permeability coefficient by 33-68%, more compared to the static grout injection method. The constrained modulus of the jointed rock mass was increased by 50% more with oscillatory grout injection compared to the static grout injection, indicating that the oscillatory injection was more effective in enhancing the stiffness of the rock mass.

• Journal of the Korean GEO-environmental Society
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• v.12 no.11
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• pp.5-12
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• 2011

Numerous studies on the improvement of low strength for soft ground have been performed. EPS, light weight filling material, is used at the study site for stability on consolidation settlement. However, several problems such as settlement of pavement layer and damage of curb occurs. The elevation is lower 1 m than that of designed value by consolidation. It is caused by excessive load during construction. In this study, problems due to overloading on the soft ground where the EPS is used were analyzed and some cases for reasonable improvement method were described. From the results, instructions for design and construction are suggested.

• Journal of the Korean Geosynthetics Society
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• v.20 no.1
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• pp.35-44
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• 2021

This research studies the stabilization method for improved soil sloped through the on-site application of Paper Flyash ground stabilizers. The target strength required for improved soil is 500 kPa, and the compressive strength for the slope surface needs to be less than 1,000 kPa after the improvement in order to plant vegetation. To meet this condition, we mixed soil from the site and the ground stabilization material, which is the main material for surface improvement material, performed mixing design and conducted various tests including strength test, permeability test and plantation test. After analyzing the results of the compression test on improved soil slope, we proposed soil constants for the improved soil. In order to evaluate the applicability of the improved soil on the slope, the site construction was carried out on the collapsed slope and the reinforcement evaluation of the surface of the improvement soil was conducted. The stability was not secured before the reinforcement, but the test shows after the reinforcement with improved soil, the safety rate is secured up to 48 hours during the raining period. In addition, the compressive strength of the improved soil at the site was secured at more than 200 kPa adhesion as planned, and the soil hardness test result was also found to be within the specified value of 18-23 mm, which increased the resistance to rainfall and ability to grow plant on the surface for improved soil.

• Journal of the Korean GEO-environmental Society
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• v.5 no.1
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• pp.75-84
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• 2004

Stone column is one of the soft ground improvement method, which can enhance ground conditions such as the settlement reduction and the increasement of bearing capacity with applying the crushed stone instead of sand. In recent, general construction material, sand is in short of supply. Therefore, the bearing capacity improvement by the stone column is considered as the alternative method needed in many cases so the bearing capacity estimation is considered as important point. Nevertheless, adequate estimation methods to predict bearing capacity of stone column considering stone column and improvement effect of ground is not yet prepared. For the analysis of above mentioned points, the behavior of stone column were simulated as numerically on various property cases of crushed stone and surrounded ground. Through the numerical analysis of simulation results, the formula for the bearing capacity estimation of stone column was suggested. This formula was verified by comparing the prediction result of in situ test.

• Journal of the Korean GEO-environmental Society
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• v.22 no.12
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• pp.15-24
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• 2021

In Korea, which is mostly mountainous, the proportion of tunnel and underground space development are increasing. Although the ground is reinforced by applying the ground improvement method during underground space development, accidents still occur frequently in Korea. In the grouting method, a representative ground reinforcement method, the effect was judged by comparing the total amount of injection material with the amount of injection material used during the actual grouting construction. However, it is difficult to determine whether the ground reinforcement is properly performed during construction or within the target ground. In order to solve this problem, it is necessary to study a new method for quality control during or after construction by measuring electrical resistivity after performing grouting by mixing carbon fiber, which is a conductive material, and microcement, which is a grout material. In this study, as a basic study, a cement specimen mix ed with 0%, 3%, 5%, 7% of carbon fiber was prepared to evaluate the performance of the grout material mixed with carbon fiber, which is a conductive material. The prepared specimens were wet curing for 3 days, 7 days, and 28 days under 99% humidity, and then compression wave velocity and shear wave velocity were measured. As a result of the compression wave velocity and shear wave velocity measurement, it showed a tendency to increase with the increase in the compounding ratio of carbon fibers and the number of days of age, and it was confirmed that the elastic modulus and shear modulus, which are the stiffness of the material, also increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.541-542
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• 2007

The paper also introduces a new Distribution Class ground lead disconnector design that not only extends the claimable detonation range well below the 20 amps specified in industry standards, but is very durable when exposed to severe arrester durability tests. Finally. this paper shows how this next generation disconnector interacts with the connected arrester to improve the overvoltage withstand capability of the arrester assembly. The interaction of the disconnector grading capacitor with the series-connected arrester metal oxide disc elements actually improves the arrester assembly temporary overvoltage withstand capability, making the design less vulnerable to TOV failures. Since the vast majority of distribution class arresters are sold domestically with ground lead disconnectors, this design improvement in the disconnector to improve detonation reliability also translates into a significantly improved distribution class arrester design.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.750-758
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• 2009

This study, as basic research which was intended to develope the surface reinforcement method using reinforcement material which is applicable to very soft ground in Korea, was aimed at proposing the design parameter for the surface ground improvement method. To that end, a wide width tensile test using geotextile, geogrid and steel bar (substitute for bamboo) and 25 kinds of the laboratory model tests with the end restraint conditions of the reinforcement that comprises the constrained and partially constrained (3 types) conditions were conducted. And the result indicated that the modulus of subgrade reaction or $N_c$ value (5.3) apparently overestimated the bearing capacity of very soft ground such as dredged ground. Moreover, as a result of model test by partially constraining the preload of 23.0kgf using geotextile, the effect of bearing capacity($q_1$) appeared to be the largest till the loading stress was $0.4tf/m^2$ due to cohesion, while it reached 75% of the maximum bearing force after $0.4tf/m^2$ due to increase in the effect of bearing capacity($q_2$) caused by the tensile force of the reinforcement. Such results tended to have appeared constantly or very similarly with each other, irrespective of the type of reinforcement (geogrid, steel bar) and constraint conditions.