• Journal of Korean Society for Geospatial Information Science
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• v.15 no.4
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• pp.89-96
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• 2007

The tunnel measurement data such as deficiency quantity, outbreak quantity, inner displacement and crown settlement are very important elements in tunnel sites under construction and obtained mostly by displacement gauge and total station. However, it is difficult and dangerous to install targets or measurement equipments on the points in tunnel construction site and also we need several persons to work in the tunnel. Non-prism total station with remote control system which is developed recently has various efficient functions for tunnel measurement. Therefore, for efficient tunnel measurement, this study suggested one person surveying system which consisted of non-prism total station and notebook PC to control total station remotely, and we evaluated the suggested tunnel measurement system. In this study, the tunnel site under construction was chosen as the test field and tunnel surveying was done by existing surveying method and suggested method separately. As result of the test, we analyzed processing time and accuracy to demonstrate the superiority of suggested one person non-prism surveying system.

• Explosives and Blasting
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• v.22 no.3
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• pp.13-26
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• 2004

This work reports results of our study on the dynamic response of buried pipelines depending on their boundary conditions. We have studied behavior of the buried pipelines both along the axial and the transverse direction with a boundary condition of free ends. The buried pipelines are modeled as beams on elastic foundation while the seismic wave as a ground displacement in the form of a sinusoidal wave. The natural frequency, its mode, and the effect of parameters have been interpreted in terms of the free vibration. In order to investigate the response on the earthquake, the resulting frequency and the mode shape obtained from the free vibration have been utilized to derive the mathematical formula for the farced vibration. We have also completed the computer program to simulate the time-displacement graphs of the pipe lines with free ends for both cases of vibrations.

• Explosives and Blasting
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• v.27 no.1
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• pp.21-31
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• 2009

An excavation damaged zone (EDZ) is created by fracturing, excavation or stress redistribution of tunnels. In this zone the mechanical and hydraulic properties of rock are changed, which makes additional cracks and serves as a dominant pathway of groundwater flow. In this study, an assessment on an EDZ size was practiced by the measurement of the deformation modulus at the KAERI underground research tunnel (KURT), and the information was applied to the modelling analysis using FLAC2D software. The EDZ at KURT fell into the range of 0.6~1.8m and the deformation moduli of the EDZ generally correspond to about 40% of intact rock mass. With a consideration of the EDZ in numerical analysis, tunnel displacements increased by about 65% and the maximum principal stress decreased to 58% from the case without EDZ. The plastic zone of the tunnel was enlarged to the crown and invert zones of the tunnel within the range of the length of rock bolts. About 2% of the total tunnel displacement with EDZ was suppressed by the KURT support system. It is anticipated that the investigation of an EDZ can be used as an important and fundamental research for validating the overall performance of a high level waste disposal system.

• Journal of the Korean Geotechnical Society
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• v.33 no.10
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• pp.59-69
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• 2017

The tension load of the ground anchor inserted in the ground gradually changes over time. In this regard the change of the initial tension load is primarily decreased by the fixation condition of the fixing head and the mechanical characteristics of the tensile material. The subsequent additional tension load is a time-dependent loss mostly due to the fixing conditions of the bonded length and the surrounding ground properties of the field. In this paper, therefore, a measurement system using a relative displacement detector that can relatively easily measure the change of tension load is discussed. As a result of the review, it was confirmed that the results using the relative displacement detector are similar to those of the real scale model test, and it was also confirmed that similar results were obtained with the result of the pull-out test conducted on the ground anchors fixed to weathered rocks condition. In addition, a pull-out test was conducted on the test anchors whose initial tension load loss was relatively large and through this test pull-out behavior of the tension type ground anchors was verified.

• Journal of the Korean GEO-environmental Society
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• v.4 no.1
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• pp.19-28
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• 2003

Current methods for lateral thrust calculations are based on the classical formulations of Rankine or Coulomb. However, the previous studies indicate that lateral earth pressures acting on the wall stem, which is the function of deformation parameters of the backfill, are close to the active condition only in the top half of the wall stem and in the lower half of the wall stem, the lateral earth pressures are significantly in excess of the active pressures. This paper presents the compressible inclusion function of EPS which can results in reduction of static earth pressure by accomodating the movement of retained soil. A series of model tests were conducted to evaluate the reduction of static earth pressure using EPS inclusion and determine the optimum stiffness of EPS. Also, field test was conducted to evaluate the reduction of static earth pressure using EPS inclusion. Based on field test it is found that the magnitude of static earth pressure can be reduced about 20% compared with classical active earth pressure.

• Geotechnical Engineering
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• v.14 no.1
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• pp.93-108
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• 1998

In this study, the analytic solutions and numerical methods were used to estimate the shape and size effects on the stability of underground openings. The stability of underground openings was evaluated by scrutinizing the effects of the rock mass quality, the state of in-situ stresses and the lateral earth pressure coefficient on the displacement, the stress concentration and the plastic region developed in the vicinity of the openings. The analytic solutions have shown that the stress concentration factor is inversely proportional to the radius of curvature of openings. Through parametric study on the various shapes and sizes of underground openings the characteristics of the controlling factors concerned with the stability were analyzed. Then, the study was extended to the horseshoe-shaped openings commonly used for under ground storage. Through the extended study the effects of the stress ratio and the height-towidth ratio of openings on the maximum displacement and plastic region developed around the openings were estimated. The results have shorn that the height-to-width ratio of domestic storage caverns can be increased economically without stability problem, as far as the lateral earth pressure coefficient is appropriate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.133-141
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• 2020

Korea Infrastructure Safety and Technology Corporation (KISTEC) specifies that the safety inspection and precise safety diagnosis of concrete structures shall be conducted in accordance with the 'Special Law on Safety Management of Infrastructure'. The detailed safety inspection and precise safety diagnosis guidelines presented by KISTEC, however, gives only the grade of members and structures, and thus it is impossible to quantify remaining service life (RSL) of the structures and to quantitatively reflect the effect of differential settlements on the RSL. Therefore, this study aims to develop a RSL evaluation model considering the differential settlements. To this end, a simple equation was proposed based on the correlations between differential settlements and angular distortion, by which the angular distortion of structures was then reflected in nominal strengths of structural members. In addition, the effects of the differential settlements on the RSL of structures were analyzed in detail by using the safety diagnosis results of actual concrete structure.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.287-294
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• 2021

In this study, tests were performed to analyze the feasibility of using the ground stabilizer from recycled resources such as blast furnace slag powder as filling material of prebored piles. For this, specimens were prepared by applying 70% and 83% of the general water/binder ratio of the filling material of prebored piles. And compression test, model test, and shaking table test were performed to determine the compressive strength, skin friction on the surface between prebored pile and filling material, and seismic performance of ground stabilizer. As a result of the tests, the compressive strength exceeded the relevant domestic standards, and the skin friction was equivalent to that of ordinary portland cement. In addition, the amount of vertical and horizontal displacement caused by earthquakes was found to be much smaller than the domestic standard. Therefore, when considering the test results comprehensively, it is judged that the feasibility of using a ground stabilizer from recycled resources as filling material for prebored pile is sufficient.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.727-732
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• 2022

Applying the calculated cross-sectional reduction due to the corroded rebar investigated in the field to the numerical analysis model, the damage pattern and delamination of concrete in the field showed a tendency relatively similar to the numerical analysis results. It was analyzed that when the expansion pressure due to corrosion of the reinforcing bar is greater than the tensile stress of the concrete, cracks are generated and the concrete cover can be fracture. As a result of this study, the correlation between the corrosion rate of reinforcing bars and the crack occurrence of the concrete cover of the subway box structure was verified based on the numerical analysis and field test results. To prevent rebar corrosion, the corrosion rate can be reduced by applying rust prevention to the reinforcing bar and changing the material. In the case of exposed to a corrosive environment, the tensile strength of the concrete is improved by adjusting the concrete compressive strength to secure durability against the expansion pressure caused by the corroded rebar.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.1
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• pp.1-11
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• 2023

In this study, the stability of the room-and-pillar underground method was investigated using numerical analysis method. In-situ geotechnical investigation was conducted, and a supporting pattern was selected based on the geotechnical investigation data. For the supporting pattern, Type-1, 2, 3 were selected for each ground condition. A 3D numerical analysis model was developed for effective simulation as the room-and-pillar underground method consist of a pillar and room. As a review of numerical analysis, it was confirmed that the crown settlement, convergence, shotcrete and rock bolt were all stable in all supporting patterns. As a result of the analysis by the construction stage, it was confirmed that excessive stress was generated in the room when the construction stage of forming pillar. So, precise construction is required during the actual construction stage of the pillar formation.