• Proceedings of the KSR Conference
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• 2001.10a
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• pp.410-415
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• 2001

Conventional Korean tunnel portals require a lot of overburden as, fer static reasons, about 1.5 to 2.0 times the tunnel diameter is needed for the height in order to achieve a sufficient arching effect. Thus, considerable movement of earth and support constructions are required which lead to undesirably large changes of and damage to the environment. With a massively designed pipe roof, tunnels with little overburden can be built. For the effective construction of a pipe roof as an advancing safeguarding method, the following properties are indispensable： stability, insensitivity to settling and drilling accuracy. With the AT casing system a new pipe roof method has been developed which on the one hand entirely combines the properties mentioned last, and which on the other hand permits safe, economical and environmentally friendly construction of tunnels at low overburden heights of 3 to 6 m.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.2
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• pp.151-160
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• 2004

This study has carried out a series of field investigation for a ASSM railway tunnel which was constructed several decades ago. It appears that the tunnel lining was cracked in the region of arching structure. Precise inspection is carried out for this region with various non-destructive testing equipments. Based on the inspection results, the cause and the effect of tunnel defects were discussed by conducting the evaluation of tunnel safety with numerical analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.595-606
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• 2009

This paper presents the characteristics of stress transfer around carven due to cavern size and rock joint properties by laboratory model test. In order to perform this study, eight different scaled model tests were carried out according to excavation stage. The limited numerical analysis were also performed to verify the model test results. The amount of stress transfer around the cavern is increased and then decreased by longitudinal arching effect according to tunnel excavation. It is founded that the stress developed around the cavern during excavation is increased when the cavern size and joint orientation are increased. It is also investigated that shear behaviour (such as stress, deformation) developed around cavern is considerably depended on the characteristic of fill material, dip and direction of joints. It is suggested that the behaviour will be verified throughout the 3D numerical prediction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.3
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• pp.133-149
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• 2021

This study aims to report the behavioral mechanism of steel pipe reinforcement grouting, which is being actively used to ensure the stability of the excavation surface during tunnel excavation, based on measurements taken at the actual site. After using a 12 m steel pipe attached with a shape displacement meter and a strain gauge to reinforce the actual tunnel surface, behavioral characteristics were identified by analyzing the measured deformation and stress of the steel pipe. Taking into account that the steel pipes were overlapped every 6 m, the measured data up to 7 m of excavation were used. In addition, the behavioral characteristics of the steel pipe reinforcement according to the difference in strength were also examined by applying steel pipes with different allowable stresses (SGT275 and SGT550). As a result of analyzing the behavior of steel pipes for 7 hours after the first excavation for 1 m and before proceeding with the next excavation, the stress redistribution due to the arching effect caused by the excavation relaxation load was observed. As excavation proceeded by 1 m, the excavated section exhibited the greatest deformation during excavation of 4 to 6 m due to the stress distribution of the three-dimensional relaxation load, and deformation and stress were generated in the steel pipe installed in the ground ahead of the tunnel face. As a result of comparing the behavior of SGT275 steel pipe (yield strength 275 MPa) and SGT550 steel pipe (yield strength 550 MPa), the difference in the amount of deformation was up to 18 times and the stress was up to 12 times; the stronger the steel pipe, the better it was at responding to the relaxation load. In this study, the behavior mechanism of steel pipe reinforcement grouting in response to the arching effect due to the relaxation load was identified based on the measured data during the actual tunnel excavation, and the results were reported.

• Tunnel and Underground Space
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• v.14 no.6 s.53
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• pp.440-449
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• 2004

Rock mass includes natural discontinuities such as joints and faults during its formation. Discontinuities are also referred as planes of weakness because of their weak mechanical characteristics. In the design of underground structures, it is necessary to consider the properties of discontinuities to insure the stability. During the excavation of a tunnel, these discontinuities have to be identified as early as possible so that proper change in excavation method or support design can be made accordingly. The excavation of the tunnel in a stable rock mass causes a 3-dimensional arching effect around the excavation face. It was revealed by previous studies that the existence of a weak zone or a fault zone ahead of tunnel foe induces a typical displacement tendency of convergence. For better understanding of the meaning of influence/trend lines of various displacement components, three-dimensional numerical analyses were conducted while varying deformation moduli, thicknesses and orientations of discontinuities. Numerical results showed that the changes in influence/trend lines of various displacement components were very similar to those by measurements. The discrepancies from the expected values were dependent on the physical properties, thicknesses and orientations of discontinuities.

• Korean Journal of Agricultural Science
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• v.19 no.1
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• pp.79-90
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• 1992

The embankment material of Andong Dam was the decomposed granite soil, and FEM analysis with settlement and stress characteristics were studied in this thesis. and also the results were as follows: 1. The vertical settlement of dam quite nearly coincides with the calculated one by FEM. A maximum value of the measured and the calculated is 40cm and 42cm, respectively, at the EL. 130m. 2. The measured settlement values of the central parts in elevation are nearly the same as those of the calculated, and the settlement values in order of magnitude are in core, filter, random and rock. 3. Horizontal deformation of max. 21cm in downstream is larger than that of max. 17cm in upstream, which is highly influenced by the water pressure of reservoir water level and the earth pressure of coffer dam in upstream. 4. Reverse arching effect of vertical stress in streamflow section are caused by the difference of stiffness, because stiffness is larger in core zone than in filter zone. 5. Load transfer ratio which is the ratio of principal stress of core zone and filter zone is 1.06, which clearly showes the reverse arching effect in vertical stress.

• Tunnel and Underground Space
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• v.20 no.4
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• pp.260-266
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• 2010

In this study, wish to analyze effect that affect on each tunnel (right and left tunnel) according as proceeding of leading tunnel (right tunnel), following tunnel (left tunnel) and pilot tunnel excavation through behavior of tunnel and surrounding base by model tests. And stress-transfer mechanism that occurs from in-situ loosing area and arching effect by difference of stiffness ratio and overburden heights were verified experimentally. The model tests were carried out by varying the stiffness of reinforced area and overburden height, measured deformation of tunnel and displacement of surrounding base. The model tests followed exactly the real 2-Arch tunnel construction stages.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.4
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• pp.1-7
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• 2015

In this paper, we present the result of analytical investigation pertaining to the structural behavior of steel-concrete composite plate girder with arch-type web stiffener. In the arch-type web stiffener located in the compression side of web, infill concrete is cast to strengthen the arch-type stiffener and also to exert resisting force against compression force. This type of composite steel-concrete plate girder bridge is built and is in service. To understand the behavior thoroughly, analytical parametric study was conducted by using the finite element method. As a result it was found that the effect of arch-type stiffener with infill concrete is considerable for the design of such type composite girder bridge.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.514-527
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• 2007

Earth reinforcement techniques are used worldwide and offer proven solutions to a wide range of geotechnical engineering problems. Here in this paper, recent developments of three major reinforced soil retaining wall methods in Japan were introduced in order to show how the current situation of this technique in Japan is. And the statistical data for the volume of the use was also shown, such as the total volume of the use, the scales of the structures, layout of the earth reinforcement, fill materials, and foundation conditions. Some of the case histories were also introduced with photographs and figures. And then, as one of recent research activity by the author, the study on the application of X-ray CT for the problem of earth reinforcement method combined with other method such as piling and soil improvement was introduced. In this study, a series of model test for several reinforced ground with geogrids was conducted using a newly developed test apparatus. Then, the behavior in the soil box was scanned after settlement using X-ray CT scanner. Based on these test results, the reinforcing effect by the geogrids and the soil arching effect over the pile heads was discussed precisely and those are done in 3-D with nondestructive condition. Finally, the effectiveness of the use of X-ray CT scanner in geotechnical engineering was promised.

• Journal of the Korean GEO-environmental Society
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• v.17 no.12
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• pp.65-72
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• 2016

There are numerous factors that affect stress distribution in a buried pipe, such as the shape, size, and stiffness of the pipe, its burial depth, and the stiffness of the surrounding soil. In addition, the pipe can benefit from the soil arching effect to some extent, through which the overburden and surcharge pressure at the crown can be carried by the adjacent soil. As a result, the buried pipe needs to support only a portion of the load that is not transferred to the adjacent soil. This paper presents numerical efforts to investigate the stress distribution in the buried concrete pipe under various environmental conditions. To that end, a nonlinear elasto-plastic model for backfill materials was implemented into finite element software by a user-defined subroutine (user material, or UMAT) to more precisely analyze the soil behavior surrounding a buried concrete pipe subjected to surface loading. In addition, three different backfill materials with a native soil were selected to examine the material-specific stress distribution in pipe. The environmental conditions considering in this study the loading effect and void effects were investigated using finite element method. The simulation results provide information on how the pressures are redistributed, and how the buried concrete pipe behaves under various environmental conditions.