• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.11a
• /
• pp.21-22
• /
• 2022

High fluidity concrete has excellent workability, and if the cross-section of the building is complicated, it is possible to place good quality concrete and increase the construction speed, so its utility value is very high. However, it is premised on the accuracy of concrete formwork assembly. Concrete leakage through formwork gaps is an important consideration when applying high flow concrete. In order to quickly solve the leak of high fluidity concrete caused by formwork gap occurring at the site by accelerator injection, we proceeded with research to confirm the possibility of reducing the amount of formwork leakage of high fluidity mortar. It was confirmed that the injection of the accelerator could reduce the amount of mortar leakage.

• Journal of the Korean Geotechnical Society
• /
• v.38 no.2
• /
• pp.15-27
• /
• 2022

Despite the increasing applicability of rock grouting as a method for strengthening or disaster prevention by improving the stability of ground, criteria for planning parameters which can be used as minimum guideline are required since the current practice is mainly dependent on experience. In this study, the fundamental criteria for important parameters of rock grouting in terms of injection conditions such as water-cement ratio, injecting pressure, cement take and resulting effects such as deformation modulus and permeability are proposed. Those criteria are the results of analyses of a series of hydraulic fracturing tests and Lugeon tests, in-situ grouting tests at 17 sites in Korea and other countries, combined with the literature analyses of standards and previous research. In addition, the method for modifying proposed criteria according to water-cement ratio is also addressed since that in Korean practice is too high and therefore, should be adjusted to satisfy the conditions of balanced stable grouting. The results of this study can be used as a fundamental reference for more refined research in the future although they are still somewhat experience-dependent.

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

• Journal of the Korean GEO-environmental Society
• /
• v.18 no.12
• /
• pp.13-23
• /
• 2017

This paper discusses about the reinforcement materials and construction method in order to cope with roadbed settlement in operating railway. In Korea, concrete tracks have been introduced to urban railways, high-speed railways, and general railways, but some recently constructed concrete tracks have experienced roadbed settlements. Reinforcement of the railway roadbed is urgent task for safe operation of railway, but it is difficult to reinforce the roadbed and there are no case history of reinforcing railway roadbed under an operating railroad track. Therefore, in this study, the target performance level for roadbed reinforcement was determined, and infiltration and solidity injection efficiency were investigated for selected reinforcement materials. As a result of the study, it was found that the generally used reinforcement materials and methods for geotechnical works need to be improved for applying in railway roadbed reinforcement.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.10
• /
• pp.25-31
• /
• 2010

Anchor, soil nail, micropile have been widely used for slope reinforcement and foundation. These all methods need grouting work after placing reinforcing member. In domestic case, gravity fill techniques and pressure grouting techniques are mainly used. In contrast the pressure re-injection grouting method is not commonly used because grouting equipment and lack of practical application example is short and the verification of reinforcing effect is difficult. Pressure re-injection grouting is a kind of post grouting which technique increases the radial stresses acting on the grout body and causes irregular surface to be developed around bond length that tends to interlock the grout and the ground. In this study, the field test was performed to evaluate the reinforcing effect with the variation of grouting methods and pullout characteristics of reinforcing member placed by pressure re-injection grouting method. The test results showed that the post-grouting methods were useful to increase the pullout capacity.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.5
• /
• pp.37-43
• /
• 2008

Inorganic injection material, which is one of the ground improvement materials, consists of cement accelerator and inorganic micro particle. The inorganic injection material is known to overcome the major limitations of water glass type improvement materials, which are leaching and accompanying strength loss. The inorganic injection material is superior in durability and strength, and environmentally friendly since leaching is prevented. In this study, the effectiveness and environment-friendliness of the MIS(Micro Injection-process System) using the inorganic injection material is compared to SGR, which uses the water glass. The performed tests were unconfined compression test, chemical resistance test, and fish poison test. The unconfined compression tests showed that the MIS results in 1.7 times higher 28 day strength compared to the SGR. In addition, the strength continually increased with time for the MIS, while it decreased for the SGR. The chemical resistance tests indicated that the rate of change in length using the MIS is 10~25 times smaller than when using the SGR. The fish poison test proved that MIS was more environmentally friendly. The analysis of chemical ingredients of leached showed that the amount of $Cr^{6+}$, Pb and Si leached from the MIS is less compared to the SGR. Accordingly, the MIS grout is more high-strength than existing SGR grout. It is excellent in shortening of construction period, structural stability of foundation and environmentally friendly. So, it is considered that it has not little the problem about groundwater pollution.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2004.05b
• /
• pp.1062-1066
• /
• 2004

암반 내에 공동을 굴착하여 LPG 혹은 원유를 저장하는 경우 공동에서의 지하수 유입량은 공동상부의 수압과 공동내의 가스압과의 관계를 파악할 수 있는 정량적인 지표가 된다. 공동내의 유입량은 되도록 일정하게 유지되는 것이 굴착등의 시공단계와 공동 운영 및 유지관리면에서 유리하며, 유입량의 급증 혹은 급감이 일어나는 경우는 그 원인을 조기에 규명하여야 한다. 이를 위해서는 지하수위, 가스저장압, 수막공 주입압 등에 따른 공동주변의 유동장 해석, 공동내로의 지하수 유입량 해석을 실시해야 한다. 지하저장공동의 유입량 해석에 있어서는 공동의 정확한 형상을 반영하기 위해서 유한요소법이 보편적으로 사유되어 왔으나 한번 설정한 유한요소망으로부터 공동의 설계요소를 변경하는 작업은 수원하지 않아 설계전단계에서 공동 및 수막 시설의 다양한 배치에 따른 모의를 수행하는데는 다소 무리가 있다. 이러한 불편함은 경계부의 형상과 조건만으로 내부점에서의 미지변수 계산을 효과적으로 수행할 수 있는 경계요소법을 도입함으로써 극복할 수 있다. 따라서 본 연구에서는 지하공동으로 배수되는 유입량 산정을 위해 경계요소법을 근간으로 한 2차원 지하수 흐름모형을 구성하였고, 이를 지하저장공동이 위치한 A기지에 적용하여 상부경계조건인 지하수위의 변화, 수막공 주입압 등에 따른 공동내의 유입량과 공동저장압과의 관계를 정량적으로 분석하였다. 분석 결과를 지하저장공동의 운영 및 유지관리에 활용될 수 있도록 수식화하여 제시하였다.

• Journal of the Korean Geosynthetics Society
• /
• v.14 no.2
• /
• pp.95-103
• /
• 2015

In this study, the causes and countermeasures for the leakage of a sea dyke under construction are analyzed. In general, the seabed ground is clearly divided from the embankment but a lot of parts show abnormal zones with low resistivity from the results of electric resistivity survey. Hence the causes of the leakage are considered as following: three-dimensional shear strain behavior, irregular compulsory replacement of the soft seabed ground with low strength and quality deterioration of the waterproof sheets during the closing process. The improvement method is determined by considering the constructability in the seawater and its velocity condition, durability, economic feasibility, similar application cases and so on. Consequently, a combination of low slump mortar and slurry grouting and injection method is selected as an optimum combination. Mixing ratio and improvement pattern are determined after drilling investigation and pilot test. The improvement boundary is separated into general and intense leakage area. The construction is performed with each pattern and the improvement effects are confirmed. The confirmed effects with various tests after completion show tolerable ranges for all of the established standards. Finally, various issues such as prediction of length of the waterproof sheet, installation of it against seawater velocity, etc. should be considered when sea dykes are designed or executed around the western sea which has high tide difference.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.11
• /
• pp.61-68
• /
• 2012

Most widely methods for reinforcement of soil utilized in Korea are anchor method, soil nail method and micro pile method. These methods are classified by the intended use of the structure to be constructed, but the reinforcement of the ground is accomplished contains in common the process of grouting work after inserting the reinforcements. Domestically, gravity grouting has been used mostly so far, but there has always been the risk of insufficient restoration of the loose ground area from the drill holes because the grouting is conducted only by gravity. On the other hand, pressure reinjection grouting may enhance the grouting quality by solving the problem of the existing grouting method considerably since it additionally reinjects grouting through pre-installed tube a certain time after the first grouting. Accordingly, this study evaluated the pullout characteristics by the grouting methods by performing model test on decomposed granite soil, and investigated the support increasing characteristics of reinforcements depending on the curing time, reinjection pressure, and uplift force variation of the pressure reinjection grouting. The result of this research shows that the pressure reinjection grouting demonstrated 1.1~1.3 times of performance of the gravity grouting, and suggests some analysis on optimal water content, reinjection pressure and curing time of the pressure reinjection grouting.

• Journal of the Korean Geosynthetics Society
• /
• v.15 no.3
• /
• pp.57-66
• /
• 2016

In this study, to prevent possible collapse caused by hydraulic or mechanical instability, liquid nitrogen injection method is developed and implemented at the tip of drilling auger of steel pipe propulsion tunneling. In this study, 1/5-scale model auger and sand chamber were manufactured. The prototype diameter of steel pile (or casing) is assumed about 1,000 mm. For the frictional sandy soils and plastic weathered soils, liquid nitrogen injection methods were tested varying water contents of the soils. For the induced hydraulic instability, the ground near the drilling auger was frozen within approximately 5 minutes preventing mechanical collapse and water infiltration. Securing stability of steel pile propulsion tunneling using liquid nitrogen was much more effective for which the water content of the soil somewhat exceeds the optimum water content.