• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.2
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• pp.147-155
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• 2013

In this paper structural analysis of underground electrical power cable structures which is excavated below the surface of the earth in the downtown area is carried out considering the effect of construction sequence. There are many various life-line facilities below the surface of the earth in the downtown area. MPDAP was used for finite element analysis of underground electrical power cable structures. Three typical sections are simulated by finite element models. Unbalanced equilibrium problems may be occurred when conventional finite element procedures were used for simulation of tunnel excavation. Therefore equilibrium perturbation concept was applied to solve these problems. The effects of time-dependent deformations in advancing tunnel excavation are considered in the stages of construction sequences as using the load distribution factor. It is shown that values of maximum displacement of both soil and rock surrounding underground electrical power cable structures obtained by our numerical studies are less than allowable values.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4977-4983
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• 2015

The full depth excavation induces couple of technical and social problems like increase of construction cost and time for excavation and backfill, increase of public complains and delay of traffic, and so force. In order to overcome these problems, lots of laboratory tests were carried out for sewer pipeline of maintenance materials with trenchless methods. The testing materials are PVC strip and then the lab tests were followed by Korean Standard. We will treat the structure safety and pipe integrity of PVC profile more excellent than the profile have application to SPR. There is no side-effect to process and to satisfy the criteria of tensile strength, impact strength and softening temperature. The profile with resin adhesive showed no leakage of water at specific pressure.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1409-1416
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• 2010

It is essential to predict a blasting-induced excavation damage zone (EDZ) beyond the proposed excavation line of a tunnel because the unwanted damage area requires extra support system for tunnel safety. Complicated blasting process which may hinder a proper characterization of the damage zone can be effectively represented by two loading mechanisms. The one is a dynamic impulsive load generating stress waves outwards immediately after detonation. The other is a gas pressure that remains for a relatively long time. Since the gas pressure reopens up the arrested cracks and continues to extend some cracks, it contributes to the final formation of EDZ induced by blasting. This paper presents the simple method to evaluate EDZ induced by gas pressure during blasting in rock. The EDZ is characterized by analyzing crack propagation from the blasthole. To do this, a model of the blasthole with a number of radial cracks of equal length in an infinite elastic plane is considered. In this model, the crack propagation is simulated by using three conditions, the crack propagation criterion, the mass conservation of the gas, and the adiabatic condition. As a result, the stress intensity factor of the crack generally decreases as crack propagates from the blasthole so that the length of the crack is determined. In addition, the effect of rock properties, initial number of cracks, and the adiabatic exponent are investigated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1089-1095
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• 2014

In this study, we compared and analyzed the displacement of final excavation with measured value through an inverse analysis method used in urban excavation construction. We maximized the effectiveness of the inverse analysis method, and plan to achieve cost-effective and practical construction management in the field with identical conditions. As the first stage, we suggest an example of a field which has the inverse analysis method. We applied the inverse analysis method to three different fields on which construction and measuring were finished. Of these three fields, two fields showed a very satisfactory result. However, in one field, there were significant differences between the analysis and measured value. The result of our analysis indicated that, we should unite the conditions of the inverse analysis method and field construction. We need to thoughtfully reconsider the RANKINE earth pressure application in a triangle type. This is because the uniformity of earth pressure is made by its arching effect, in the condition of the displacement of lower underground occurring widely, which is differentiated with the earth pressure conditions of RANKINE, even if the slurry wall has stiffness. Also, when recalculating the soil parameter, we should emphasize the adhesion of the weathering zone, and give experimental consideration to ground water level.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.69-79
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• 2012

This pre-supported nail method is able to decrease ground displacements more than NATM because this method reinforces ground with grouted steels before tunnel excavation. Therefore this method has advantage of being able to increase the stability and workability. This study presents applicability of pre-supported nail method with case of site measurement for shallow tunnel composed with high groundwater level and unconsolidated soil, performs this research the mechanism of new supporting system is compared with the conventional existing supporting system in terms of soil reinforcement. NATM has characteristics that construction stage displacement of the apparent height difference is observed in the step of divided excavation processing. Otherwise it is analyzed that pre-supported nail method is not sensitive in the displacement problem of excavation processing in comparison to NATM. It is found that this method is very applicable in shallow depth tunnel such as portal area, tunnel in soil and weak zone without arching effect.

• Journal of the Korean Institute of Gas
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• v.21 no.6
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• pp.8-14
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• 2017

One of the main causes of gas pipeline accidents is mechanical impact(third party damage). The majority of high pressure gas pipelines buried in major domestic industrial complexes are old pipes which have being operated over 20 years. Therefore, if an accident occurs, there will be a full scale accident because there is no additional inspection and reinforcement time. In this study, the defects on the piping during the mechanical impact were studied through the third party damage(excavation) experiments. Experiments were carried out using the 21 ton excavator which is operated in the actual excavation work and the type of pipe to be struck are ASTM A106 Grade.B and ASTM A53 Grade.B. As a result, when the bucket used during excavator operation is a sawtooth bucket, the defect is more bigger. And the smaller the diameter of the pipe, the smaller the depth and length of the defect. Also, it was confirmed that the impact height had no effect on the defects on the buried pipe, during the excavation work.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.4
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• pp.289-305
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• 2006

This paper presents the effect of excavating methods on tunnel behavior. As part of this study, it is preliminarily focused on the comparison of two different excavation methods, center diaphram (CD) method and ringcut (RC) method. Especially, the purpose of this research is to study the behavioral mechanism of two tunnels which share the same construction environment but different excavating method. Two numerical analysis models with the same tunnel section and material properties are compared in this study, and they are analyzed by 3D finite element analysis. In each model, face stability, crown displacement, ground settlement, and shotcrete-lining stress are computed, then the general behavior of CD method and RC method is studied. The results indicate that the CD method tends to be effective in controlling tunnel displacement while the RC method is more effective in controlling ground settlement. Design implications of the findings from this study are discussed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.333-339
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• 2015

In this paper, the surface settlement resulted from the shallow TBM tunnelling has been numerically simulated. TBM tunnelling is especially used in urban area to avoid serious vibration and noise caused by explosion in NATM. Surface settlement is one of the most important problems encountered in all tunnelling and critical in urban areas. In this study, face vibration of TBM excavation is considered to estimate surface settlement trend according to TBM extrusion. The dynamic excavation forces are calculated by total torque on the TBM cutterhead in mixed-face of soil and weathered rock condition with shallow depth. A 3-dimensional FDM code is employed to simulate TBM tunnelling and mechanical-dynamic coupling analysis is performed. The 3D numerical analysis results showed that dynamic settlement histories and trend of surface settlement successfully. The maximum settlement occurred at the excavation point located at 2.5D behind the face, and the effect of face vibration on the surface settlement was verified in this study.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.109-122
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• 1993

ln this paper, a finite element analysis procedure is proposed for the incremental multi-step excavations in a fluid-saturated porous medium such as saturated soil ground. As the basis of derivation, Biot's equation was used. The proposed procedure was applied to some one- and two-dimensional problems under incremental excavations. Unsaturated cases as well as saturated cases were considered for comparison. Through numerical tests, the effects of permeability and excavation speed on the deformation history was investigated. Results showed that pore pressure built up during incremental excavation has a significant effect on the deformation and stresses of solid skeleton and validated the use of the present procedure for the analysis of multi-step excavations in fluid-saturated media such as in saturated shallow ground.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.3
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• pp.217-226
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• 2003

This study is focused on the finding out load transfer mechanism in the ground near the tunnel during tunnel excavation in the jointed sandy ground. Laboratory model tests were performed on various cases of the overburden heights above tunnel crown, location, and degree of discontinuity planes. For model tests, a movable plate was installed in the midst of the bottom of sandy ground. This plate, moving downwards, was intended to model the stress relaxation during tunnel excavation. The load transfer was measured at the fixed separated bottom plates adjacent to the movable plate. As the result, the loosening zone and the load-transfer form around the tunnelling site were affected by the overburden height and the characteristics of discontinuous planes. And large loosening zone was developed along the discontinuous planes which were close to the tunnel.