• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.241-250
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• 2011

The design method of IGM proposed by FHWA to predict bearing capacities of drilled shaft socketed in weathered granite has been used generally. In this study, site investigations were performed in a pilot test site, and disturbance and roughness were measured. Geotechnical properties were assorted as cohesive material and undisturbed and smooth surface. A simple relationship was proposed to predict unconfined strength ($q_u$) of weathered granite using static load test results, load transfer test results and N values. It was confirmed that the design method to estimate bearing capacities of drilled shaft could improve IGM's theory for weathered granite from this research.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1D
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• pp.71-77
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• 2010

This study presented the operation method through of productivity on eight analysis work items (TBM boring, cutter check and exchange, TBM maintenance, succeeding facilities, reinforcement in tunnel, operation alternation, a tram car) which have developed equipment at WRITH with TBM a waterway tunnel works. It was inquired lose time with analyzed result by work items and removed lose time. It was analyzed TBM boring length, TBM boring length percentage and TBM boring length time. This study analyzed TBM operation utility factor of a foreign work with TBM operation boring length percentage, a monthly average boring length, pure boring length percentage etc. and assumed a monthly average boring length and a monthly average boring length of rise forecast. Based on analyzed Data, TBM boring has been forecasted propriety pure boring length at compressive strength $675{\sim}1662kgf/cm^2$.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.101-113
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• 2001

Structural and geological engineering properties of the rock mass distributed in the Yokmang mountain area were investigated to detenninc the usable cut-out volume and quarrying efficiency. The study area is located in the southern tip of the Yangsan fault system which controls the geological structure of the Kvungsang basin. As a result, the study area is mainly composed of andesicic. rhyolitic. and granitic rocks of the Cretaceous Kyungsang Supergroup and a series of right-handed strike-slip faults is developed along NNE-SSW direction. These regional faults significantly affect the spatial and meclwnical characteristics of joints such as spacing, frequency, and compressive strength. The joint frequency is highest along the fault zones and decreases toward the remote region. Based on the geological information obtained from the field survey, the detailed structure of the Yokmang mountain was analyzed and the volume of the rock mass was assessed. Considering the minimum rock block size required for the construction of a coastal dumping site, potential cut-out volume is then estimated to be 4,018,000m$^3$ the volume % of which is 48% of Yokmang mountain including the soil and weathered rock and 61% of the unweathered rock mass.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.441-453
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• 2016

This study aimed to develop a two-component TSL suitable for reducing dust and guaranteeing homogeneous qualities during its spraying. Its performance was evaluated by a series of laboratory and field tests. High ductility of two-component TSL prototypes resulted in increasing their elongation at break even though their tensile strengths were slightly lower than those of one-component powder TSLs. One prototype of the two-component TSLs developed in this study was verified to satisfy every criterion specified by EFNARC (2008). Especially, it increased the average compressive strength of mortar specimens by 50% even when it coated them only with the thickness of 3 mm. From a preliminary spraying test, a spraying machine suitable for the developed TSL prototype was derived and modified. After its field application, dust and rebound generated during its spraying works were found to be very minimal. Its spraying rate was recorded to be approximately $60m^2/hr$. In addition, it showed a very rapid hardening characteristic compared with general sprayable waterproofing membranes.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.97-107
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• 2017

Recently, there have been a lot of incidents related to ground sinks in urban areas, but restoration work is complicated and inconvenience due to on-site control, and particularly, grouting and soil filling are generally applied as recovery measures, but when the grouting or the soil filling is carried out, material segregation phenomenon occurs in the ground or a lot of restoration amount is often required, depending on the state of sinks and the existence of groundwater under the ground and the soil can be lost due to the flow of the ground water, and thus the purpose of this study is to develop a pouch-type filler applied to a trenchless method for emergency reinforcement of the ground sinks with the aim of quick recovery of the ground sink in urban areas, and as a result, it was confirmed that compression strength and the expansion ratio were different according to the temperature of ground water and the compression strength and the expansion ratio could be controlled by mixing alumina powder.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.47-54
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• 2017

This study aims to develop a bio-grouting material in a powder form like cement. Sand gel samples were produced with the ratio of sodium silicate No.3 to water (50 : 50, 35 : 65, 20 : 80), and the ratio of cement to bio-grouting material (100 : 0, 90 : 10, 70 : 30) to select a mixing ratio of bio-grouting, respectively, and then analyzed the geltime over time. The uniaxial compressive strength was evaluated to select and suggest a mixing ratio optimized for construction conditions. The indoor test reveals that preferred geltime and uniaxial compressive strength is obtained in 35 : 65 with respect to the ratio of sodium silicate No.3 to water, and 90 : 10 with respect to the ratio of cement to bio-grouting material to demonstrate best optimal mixing ratios.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.109-116
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• 2010

The Water glass grouting method has been applied frequently to penetration grouting in practice, but some problems, such as decrease of durability with the elapsed time and environmentally adverse effect, are raised recently. Hence, the Earth Natural Grouting method which uses micro cement and inorganic material is developed to overcomes those problems of the water glass grouting method, and is aimed for extensive ground injection bound. Volumetric strain test, syneresis test, unconfined compression test, triaxial permeability test, in-situ permeability test and heavy metal analysis were conducted to verify application of the ENG. As the result of tests, volumetric strain, syneresis and unconfined strength of the ENG were superior to those of the Water Glass SGR and ENG was proved to be impermeable. Also it is expected that the ENG would not have an effect on environmental pollution.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.111-121
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• 2022

It has been reported that current amount of coal ash remains almost 100 million tons and 5.85 million tons of blast furnace slag are generated annually in Vietnam. Vietnam government has encouraged the industries to increase the use of coal ash and blast furnace slag as construction materials as well as in cement production institutionally. However, limited can be applied in the construction field yet. Therefore, in this study, basic performance analysis on five different kinds of fly ash from Vietnam was conducted. In addition, the performances of blast furnace slags generated in Vietnam and Korea were compared and evaluated. Soil stabilizer compressive strength test and solidified soil unconfined compressive strength test were conducted as the basic data for the development of soil stabilizer applied to the soil mixing method using fly ash and blast furnace slag generated in Vietnam. The results showed that the Vietnamese fly ash and blast furnace slag can be used as the raw materials for soil stabilization and improvement.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.387-394
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• 2009

The objective of this study is to evaluate the durability and deterioration of concrete lining in the seven conventional tunnels. These tunnels were constructed about 40~70 years ago, and closed about 10~40 years ago. The field investigation and various laboratory testings were performed for this study. It was observed from the visual, examinations that the concrete linings of 7 tunnels were severely deteriorated, such as, cracks, leakages, desquamation, and exploitations. The compressive strengths obtained from rebound hardness method and uniaxial compressive strength test on core specimens largely differed depending on the locations in the tunnel. The maximum compressive strength of concrete lining was greater about 2 times than the minimum compressive strength of concrete lining in the same tunnel. The results of micro-structural analysis showed that the substances deteriorating the concrete lining, such as ettringite and thaumasite, were detected in the concrete lining of tunnel.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.341-348
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• 2023

In this study, in order to minimize the increase in the amount of various industrial by-products due to the rapid growth of the industry and the intensification of the depletion of natural aggregate resources, the material test using recycled aggregate and steelmaking slag and the proper mixing ratio of recycled concrete were to be derived. In this study, first, the conformity of the quality standards of the materials used in the field was confirmed, and the workability and molding results were shown when used alone or mixed. Therefore, the feasibility of application as aggregate for concrete was evaluated through a total of 4-type mixtures of cement types, admixtures, coarse aggregates, and fine aggregates. As a result of the experiment, it was confirmed that the slump of unhardened concrete, the amount of air, chloride and compressive strength of hardened concrete according to the replacement rate were different from the measured values of general concrete quality characteristics. According to this, it was confirmed that the quality characteristics of the standard design criteria were satisfied.