• Journal of the Korean GEO-environmental Society
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• v.17 no.9
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• pp.37-45
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• 2016

This study analyzes the environmental and durability problems of traditional (LW) grouting method. And the proposed method was compared to the others effects by analyzing the in-situ applicability and effect of performance of the method using the silica sol. This study analyzed the eco-friendly, effects of high strength silica sol through laboratory tests. The effects of the construction process were identified through the field tests. The compressive strength was increased by 1.3 times compared to the LW method and the shrinkage is 3~8 times less than that of LW method with water glass. No toxicity, which could affect soil contamination. In particular, it was confirmed that the Toxicity fish also survived with little pH change in the concentration tank. Also it confirmed the construction effects through field test. Field tests are a standard penetration test, permeability test, LLT, BST. Permeability was reduced to $1{\times}10^{-5{\sim}-6}cm/sec$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.197-205
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• 2018

Recently, remodeling is increasing due to aging of buildings. Therefore, the importance of quality control of structures has been raised, and interest in safety diagnosis and evaluation of structures has been increasing. In order to accurately diagnose old buildings, a diagnostic evaluation technique is needed to evaluate the defects of structures in advance. In addition, as the safety diagnostic criteria for reconstruction are improved and the weight of structural safety is increased, researches on safety diagnosis techniques of structures that are faster and more reliable are needed. In this study, we tried to estimate the compressive strength by examining the correlation between ultrasonic pulse velocity and compressive strength of a 1 story structure consisting of vertical and horizontal members of reinforced concrete using ultrasonic pulse velocity method, which is one of the nondestructive testing methods. The purpose of this study is to examine the applicability in the field. As a result, the estimated average error rate of the compressive strength of the structure using the ultrasonic pulse velocity method was 28.7%, which confirmed the applicability in the field. However, in order to increase the accuracy of the estimation, the necessity of the reliable diagnostic method using the composite nondestructive testing method was confirmed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.377-386
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• 2010

This study was conducted to find out the characteristics of the expanded road embankment constructed by the lightweight air-mixed soil (slurry density $10kN/m^3$) for a short-term without any ground improvement. Compression strength, capillary rise height of the lightweight air-mixed soil and settlement behavior of soft ground were studied. Compression strengths of the specimens sampled at the site after 1 and 5 months of construction were all satisfied the required strength 500 kPa. However, it was not convinced the homogeneity construction, because the values of strength were depending on the sampled location. Also, strength difference between laboratory and site specimens were found about 19%, and thus it should be considered for mixing design. Capillary rise reached about 20 cm for 70 hours because of a numerous tiny pores existed inside the lightweight air-mixed soil. Relationship between settlement and time of the soft ground placed underneath the expanded embankment was estimated by using the measured data and back analysis technique. The current average consolidation ratio and the final settlement after 120 months later were estimated about 32% and 4.5cm, respectively. This settlement is much less value than the allowable settlement 10cm for this structure.

• Tunnel and Underground Space
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• v.33 no.6
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• pp.547-560
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• 2023

Recently, research on predicting ground classification using machine learning techniques, TBM excavation data, and ground data is increasing. In this study, a multi-classification prediction study for uniaxial compressive strength (UCS) was conducted by applying random forest model based on a decision tree among machine learning techniques widely used in various fields to machine data and ground data acquired at three slurry shield TBM sites. For the classification prediction, the training and test data were divided into 7:3, and a grid search including 5-fold cross-validation was used to select the optimal parameter. As a result of classification learning for UCS using a random forest, the accuracy of the multi-classification prediction model was found to be high at both 0.983 and 0.982 in the training set and the test set, respectively. However, due to the imbalance in data distribution between classes, the recall was evaluated low in class 4. It is judged that additional research is needed to increase the amount of measured data of UCS acquired in various sites.

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.5-13
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• 2012

This research have investigated the application and the injection effect of the alkaline silicasol grouting materia (which is) recently developed. To compare the engineering characteristics of the alkaline silicasol which is formed with 3D-gel and the sodium silicate, it have studied the strength and environmental effects through the laboratory test, and field application was investigated with a review of the injection effect and waterproof through the field test. As a result of the laboratory test, unconfined compression strength of alkaline silicasol was 5 times more than sodium silicate. As a result of the leaching test, a total amount of the eluviated elements was very small, it considered the environment-friendly material. As a result of the field test, considerable reduction of the coefficient of permeability at the hydraulic layer was confirmed, and it could secure that the coefficient of permeability showed a lower than standard value of $10^{-5}cm/sec$.

• 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 Korea Concrete Institute
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• v.27 no.6
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• pp.669-676
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• 2015

Time dependent model for prediction of compressive strength development of concrete cured by microwave heating form was presented in this study. The presented model is similar to the equation which is given in ACI 209R-92 but the constants which is dependent on cement type and curing method in the presented model are modified by the regression analysis of the experimental data. Laboratory scale concrete specimens were cast and cured by the microwave heating form and drilled cores extracted from the specimens were fractured in compression. The measured core strengths are converted to standard core and in-situ strengths. These in-situ strengths are used for the regression.

• Journal of the Korea Convergence Society
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• v.13 no.1
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• pp.229-234
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• 2022

The non-destructive method of easily evaluating concrete strength through the concept of maturity has been verified by many researchers. The current work introduced such a concept in concrete strength assessment that involved 843 variables and specific values that 11 papers used in experiments, including constant temperatures (5, 10, 20, 30, 40, 50℃) with a W/B range of 18 to 70% and different curing ages (0.5 to 182 days). The classification of concrete as being of normal-strength concrete (40MPa or less), high-strength concrete (40~70MPa), and Super high-strength concrete (70MPa or more) enabled this study to identify the relationship between maturity and concrete strength using the most convenient and easily applicable maturity model in the construction field. A regression formula of lowest guaranteed concrete strength on the basis of maturity was presented.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.163-172
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• 2003

The engineering properties of composite silicate grout materials that were developed recently were analyzed. In this laboratory tests, OPC (Ordinary Portland Cement) was mainly used as grout materials. Moreover, the properties of composite silica, silica sol and sodium silicate (No.3) acting as coagulating agent were analyzed and compared with each other. For the purpose of finding the engineering properties of composite silicate grout materials, various physical and chemical tests were performed : naked eye measurement, photographing by using SEM, uniaxial compression test and in-situ application test. A series of test results showed that the strength of composite silicate grout materials was about 3～6 times that of ordinary sodium silicate grout materials in 6～24hr. Especially, based on the evaluation of the application of JS-CGM grout to the construction fields, composite silicate grout would be very effective in reducing the coefficient of permeability.

• Computational Structural Engineering
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• v.7 no.4
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• pp.4-9
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• 1994

강섬유 보강 콘크리트는 콘크리트 내에 강섬유를 임의로 투입함으로써 취성의 콘크리트 물성을 연성적으로 향상시킴과 동시에 압축, 인장, 휨 강도를 증가시킨 새로운 구조 신소재라고 할 수 있다. 과거 70년대가 SFRC의 재료적 물성에 대한 실험적 시기였던 반면 현재는 현장에 SFRC를 시공하는 응용단계라 할 수 있다. SFRC의 우수성은 선진 외국의 경우 일반적으로 기업, 정부, 계약관계자 등에게 잘 인식되어 있어 이미 많은 시공현장에서 응용되고 있다. 이로 인하여 외국(미국, 일본, 유럽 등)의 경우 구조적으로 안정되고 경제적인 구조물을 실현하고 있으나 국내의 경우는 안타깝게도 SFRC에 대한 인식이 아직 일반화되어 있지 않으며 시공현장도 매우 드문 실정이다. SFRC에대한 연구는 국.내외 학회에서 꾸준히 연구, 개발하고 있으며 이들 연구결과가 경제적이고 우수한 구조물을 실현하는데 기여할 수 있기를 기대한다.