• Journal of the Society of Disaster Information
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• v.18 no.4
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• pp.769-777
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• 2022

Purpose: This study analyzes and studies the characteristics of the Jeju area and uses them as basic data such as construction method design in the future development project. Method: Based on the ground survey data of the construction conducted in Jeju, the depth, relative density, N value, function state, color tone, groundwater level, and compressive strength were analyzed and studied. Result: Studies show that Jeju has columnar joints consisting of ancient volcanic activity and rapid cooling by nearby seawater, thick sand layers found on the coast, and clinker layers and Seogwipo layers formed by Mercury volcanic activity. Conclusion: It is hoped that it will be used as data for selecting basic design and basic construction method by understanding the special ground form of Jeju area and reflecting its characteristics well when designing construction.

• Geomechanics and Engineering
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• v.31 no.3
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• pp.237-248
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• 2022

Nowadays, more and more subway tunnels were planed and constructed underneath the ground of urban cities to relieve the congested traffic. Potential damage may occur in existing tunnel if the new tunnel is constructed too close. So far, previous studies mainly focused on the tunnel-tunnel interactions with circular shape. The difference between circular and horseshoe shaped tunnel in terms of deformation mechanism is not fully investigated. In this study, three-dimensional numerical parametric studies were carried out to explore the effect of different tunnel shapes on the complicated tunnel-tunnel interaction problem. Parameters considered include volume loss, tunnel stiffness and relative density. It is found that the value of volume loss play the most important role in the multi-tunnel interactions. For a typical condition in this study, the maximum invert settlement and gradient along longitudinal direction of horseshoe shaped tunnel was 50% and 96% larger than those in circular case, respectively. This is because of the larger vertical soil displacement underneath existing tunnel. Due to the discontinuous hoop axial stress in horseshoe shaped tunnel, significant shear stress was mobilized around the axillary angles. This resulted in substantial bending moment at the bottom plate and side walls of horseshoe shaped tunnel. Consequently, vertical elongation and horizontal compression in circular existing tunnel were 45% and 33% smaller than those in horseshoe case (at monitored section X/D = 0), which in latter case was mainly attributed to the bending induced deflection. The radial deformation stiffness of circular tunnel is more sensitive to the Young's modulus compared with horseshoe shaped tunnel. This is because of that circular tunnel resisted the radial deformation mainly by its hoop axial stress while horseshoe shaped tunnel do so mainly by its flexural rigidity. In addition, the reduction of soil stiffness beneath the circular tunnel was larger than that in horseshoe shaped tunnel at each level of relative density, indicating that large portion of tunneling effect were undertaken by the ground itself in circular tunnel case.

• Journal of Engineering Education Research
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• v.13 no.6
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• pp.152-163
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• 2010

Civil engineering based on construction and maintenance of infrastructures for social and human development, it has a conservative aspects to adopt the high-technology and pace of change from ancient society. Therefore, the education of civil engineering consists of very similar contents from the past until now. Also, civil engineering, area is established the infrastructure widely included structure, geotechnical, hydraulic, environmental, surveying, construction management. Civil engineering have totally difference characteristics compared to manufacturing industry field for market interests such as mechanical engineering, chemical engineering, material engineering etc. Therefore, the capstone design concepts of civil engineering for public interests must be changed and applied unlike any other engineering areas capstone design. In this paper, the modified capstone design contents and instruction in civil engineering of Yonsei University is informed and evaluated using undergraduate students' course evaluations and learning assessment to verify the efficiency of modified capstone design in civil engineering.

• Journal of the Korean Geotechnical Society
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• v.28 no.5
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• pp.41-54
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• 2012

The weathering process of rocks leads to the reduction of geotechnical bearing capacity. The weathering of granite is frequently used to refer to the degradation of geotechnical property in the design and construction of infra-structure. In this study, the range of values of CIA (chemical index of alteration) and the change of mineral compositions by weathering have been analysed with igneous rock, which covers 45.5% in South Korean territory. Several weathering indices were studied for various rocks found in Korea and significant relationships between different indices were delineated via statistical analysis. The applicability of CIA was found to be the most significant among all weathering indicies. The composition of illite, the secondary weathering residual, generally increases for the felsic rock, and swelling clay material is not included. The weathering of felsic rock will follow a sequential process, starting from bed rock, illite, and chlorite to kaoline. The mafic rock will show weathering process, from bed rock, smectite, and chlorite to kaoline. The intermediate rocks such as andesite and tuff will show similar weathering procedure and the composition of kaoline, chlorite, and smectite tends to increase more than that of illite when the mafic rock is dominated. This means the increase of rock material which has high CEC (cation exchange capacity) during secondary weathering process. However, the characteristics of a specific rock cannot be completely analyzed using merely CIA, since it is exclusively based on chemical composition and corresponding alteration. The CIA can be used to quantify the weathering process in a limited range, and further considerations such as rock composition, strength characteristics will be required to configure the comprehensive weathering impact on any specific region.

• Journal of the Korean Geotechnical Society
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• v.38 no.7
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• pp.5-24
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• 2022

The current performance evaluation of slope anchors qualitatively determines the physical bonding between the anchor head and ground as well as cracks or breakage of the anchor head. However, such performance evaluation does not measure these primary factors quantitatively. Therefore, the time-dependent management of the anchors is almost impossible. This study is an evaluation of the 3D numerical model by SfM which combines UAS images with terrestrial LiDAR to collect numerical data on the damage factors. It also utilizes the data for the quantitative maintenance of the anchor system once it is installed on slopes. The UAS 3D model, which often shows relatively low precision in the z-coordinate for vertical objects such as slopes, is combined with terrestrial LiDAR scan data to improve the accuracy of the z-coordinate measurement. After validating the system, a field test is conducted with ten anchors installed on a slope with arbitrarily damaged heads. The damages (such as cracks, breakages, and rotational displacements) are detected and numerically evaluated through the orthogonal projection of the measurement system. The results show that the introduced system at the resolution of 8K can detect cracks less than 0.3 mm in any aperture with an error range of 0.05 mm. Also, the system can successfully detect the volume of the damaged part, showing that the maximum damage area of the anchor head was within 3% of the original design guideline. Originally, the ground adhesion to the anchor head, where the z-coordinate is highly relevant, was almost impossible to measure with the UAS 3D numerical model alone because of its blind spots. However, by applying the combined system, elevation differences between the anchor bottom and the irregular ground surface was identified so that the average value at 20 various locations was calculated for the ground adhesion. Additionally, rotation angle and displacement of the anchor head less than 1" were detected. From the observations, the validity of the 3D numerical model can obtain quantitative data on anchor damage. Such data collection can potentially create a database that could be used as a fundamental resource for quantitative anchor damage evaluation in the future.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.101-114
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• 2008

Pressurized grouting is a common technique in geotechnical engineering applications to increase the stiffness and strength of the ground mass and to fill boreholes or void space in a tunnel lining and so on. Recently, the pressurized grouting has been applied to a soil-nailing system which is widely used to improve slope stability. Because interaction between pressurized grouting paste and adjacent ground mass is complicated and difficult to analyze, the soil-nailing design has been empirically performed in most geotechnical applications. The purpose of this study is to analyze the ground behavior induced by pressurized grouting paste with the aid of laboratory model tests. The laboratory tests are carried out for four kinds of granitic residual soils. When injecting pressure is applied to grout, the pressure measured in the adjacent ground initially increases for a while, which behaves in the way of the membrane model. With the lapse of time, the pressure in the adjacent ground decreases down to a value of residual stress because a portion of water in the grouting paste seeps into the adjacent ground. The seepage can be indicated by the fact that the ratio of water/cement in the grouting paste has decreased from a initial value of 50% to around 30% during the test. The reduction of the W/C ratio should cause to harden the grouting paste and increase the stiffness of it, which restricts the rebound of out-moved ground into the original position, and thus increase the in-situ stress by approximately 20% of the injecting pressures. The measured radial deformation of the ground under pressure is in good agreement with the expansion of a cylindrical cavity estimated by the cavity expansion theory. In-situ test revealed that the pullout resistance of a soil nailing with pressurized grouting is about 36% larger than that with regular grouting, caused by grout radius increase, residual stress effect, and/or roughness increase.

• Geotechnical Engineering
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• v.2 no.1
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• pp.27-44
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• 1986

The measured soil data are analyzed to the descriptive statistics and classified into the four models of uncorrelated-normal (UNNO), uncorrelated-nonnormal (VNNN), correlatedonnormal(CONN), and correlated-nonnormal(CONN) . This paper presents the comparisons of reliability index and check points using the advanced first-order second-moment method with respect to the four models as well as BASIC Program. A sin91e-mode Performance function is consisted of the basic design variables of bearing capacity and settlements on shallow foundations and input the above analyzed soil informations. The main conclusions obtained in this study are summarized as follows: 1. In the bearing capacity mode, cohesion and bearing-capacity factors by C-U test are accepted for normal and lognormal distribution, respectively, and negatively low correlated to each other. Since the reliability index of the CONN model is the lowest one of the four model, which could be recommended a reliability.based design, whereas the other model might overestimate the geotechnical conditions. 2. In the case of settlements mode, the virgin compression ratio and preccnsolidation pressure are fitted for normal and lognormal distribution, respectively. Constraining settlements to the lower ones computed by deterministic method, The CONN model is the lowest reliability of the four models.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.368-376
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• 2010

The bent foundation with single drilled shafts is suitable and economical in South Korea, which has good rock in a shallow depth. This foundation has been designed with an elastic design concept. To apply a plastic design concept written in Korea Bridge Design Criteria, a detail design regulation, which includes the method for a plastic hinge point to occur above the ground, rebar arrangement and soil modelling, should be defined. Soil modelling should be considered in the respect of structural engineer's practicality. In this paper, single drilled shaft piers with 1m diameter are constructed, and cyclic lateral load tests loaded at 4m above the ground are taken to examine the behavior. Reduced diameter shaft above the ground and remaining the steel casing under the ground were used to induce plastic hinge to occur above the ground. Simplified soil models such as elastic relation and p-y curve are adapted, and the prediction results are compared with test results. Prediction results of a model bridge were compared according to soil models with time domain analyses, and design criteria of soil were proposed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.3
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• pp.201-220
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• 2023

Power cable tunnels is one of the underground structures meant for electricity transmission and are constructed using shield TBM method when transitting across urban and subsea regions. With the increasing shaft depth for tunnels excavation when the shield TBM excavated the rock mass, the review of selecting closed-type shield TBM in rocks becomes necessary. A simplified shield TBM design method is also necessary based on conventional geotechnical survey results. In this respect, design method and related design program are developed based on combined results of full-scale tests, considerable amount of accumulated TBM data, and numerical simulation results. In order to validate the program results, excavation data of a completed power cable tunnel project are utilized. Thrust force, torque, and power of shield TBM specification are validated using Kernel density concept which estimates the population data. The robustness of design expertise is established through this research which will help in stable provision of electricity supply.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.185-192
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• 1999

It had found that, as a result of cross-hole tonic logging test, concrete was not filled partially within the bottom 2.0 m of the large diameter (Ø= 2,500mm) rock socketed pile, MP20-P11(socket diameter (Ø= 2,200mm), which was a pile among piles group supporting a pier of Kwangan Grand Bridge. The pile was repaired by the combined cement grout injected through the pipes for the cross-hole sonic logging test and the bore holes for core samples. A month after the cement grouting, repairing was checked by coring and cross-hole sonic logging then 3 times of grouting and 2 times of coring were, in turns, peformed, then repairing was completed successfully. The vertical compressive capacity of the repaired large diameter socketed pile was evaluated by several formulas and software ROCKET, and was more conservative than design load (1,882 ton) of MP20-P11. It is expected that, in the case of the battered socketed piles, it could be more reasonable to analyze the behaviors of a battered pile using 3-D model. A 3-D analysis will be peformed in the future study.