• Journal of the Korean GEO-environmental Society
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• v.20 no.5
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• pp.13-21
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• 2019

There are many cuts or natural rock slopes that remain stable for a long time in the natural environment with steep slopes ($65^{\circ}$ to $85^{\circ}$). In terms of design practice, the rock mass consisting of similar rock condition and geological structures is defined as a good continuum rock slope, and during the process of decision making angle of this rock slope, it will be important to establish the geotechnical properties estimating method of the continuum rock on the process of stability analysis in the early stages of design and construction. In this study, the stability analysis of a good continuum rock slope that can be designed as a steep slope proposed a practical method of estimating the shear strength by induced from the Hoek-Brown failure criterion, and in addition, the design applicability was evaluated through the stability analysis of steep rock slope. The existing method of estimating the shear strength was inadequate for practical use in the design, as the equivalent M-C shear strength corresponding to the H-B envelope changes sensitively, even with small variations in confining stress. To compensate for this problem, it was proposed to estimate equivalent M-C shear strength by iso-angle division method. To verify the design applicability of the iso-angle division method, the results of the safety factor and the displacement according to the change in angle of the cut slope constructed at the existing working design site were reviewed. The safety factor is FS=16~59 on the 1:0.5 slope, FS=12~52 on the 1:0.3 slope, most of which show a 10~12 percent reduction. Displacement is 0.126 to 0.975 mm on the 1:0.5 slope, 0.152 to 1.158 mm on the 1:0.3 slope, and represents an increase of 10 to 15%. This is a slightly change in normal proportion and is in good condition in terms of stability. In terms practical the working design, it was confirmed that applying the shear strength estimated by Iso-angle division method derived from the H-B failure criterion as a universal shear strength for a good continuum rock mass slope was also able to produce stable and economic results. The procedure for stability analysis using LEM (Limit Equilibrium Analysis Method) and FEM (Finite Element Analysis Method) will also be practical in the rock slope where is not distributed fault. The study was conducted by selecting the slope of study area as a good rock condition, establishing a verification for which it can be applied universal to a various rock conditions will be a research subject later on.

• Journal of the Korean Geosynthetics Society
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• v.15 no.3
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• pp.27-37
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• 2016

Although many studies on the Granular Compaction Pile (GCP) have been done by many researchers, the GCP design has not been systematically done due to the absence of the rational design methodology. As the GCP design has been mostly done by engineers' own experiences, some failure cases have been reported to occur. For this reason, it is very difficult to confirm definite causes of the failure and establish the prevention plans for the failure. Therefore, this study aims to investigate the optimal mixing ratio of gravel and sand, the effects of the internal friction angle of the GCP on the stress concentration ratio and the vertical and horizontal settlements. In order to analyze the behavior of the soft ground reinforced with the GCP depending on the different design parameters such as the stress concentration ratio and the internal friction angle, a number of finite element (FE) analyses were performed. From the direct shear test, the optimal mixing ratio of gravel to sand was found to be 70:30. Based on the numerical analyses, as the internal friction angle increased, the stress concentration ratio increased and it converged to a constant value. In addition, the larger the internal friction angle, the smaller the settlements. Consequently, the use of the optimal mixing ratio of gravel and sand can lead to reducing both the lateral flow and the heaving phenomenon.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.3
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• pp.245-256
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• 2008

The steel rib, one of the main support of tunnel, plays a very important role to stabilize tunnel excavation surface until shotcrete or rockbolt starts to perform a supporting function. In general, a steel rib at the horizontal funnel is being installed in the direction of gravity which is known favorable in terms of constructability and stability. However, as the direction of principal stress at the inclined tunnel wall is different from that of gravity, the optimum direction of steel rib could be different from that at the horizontal tunnel. In this study, a numerical method was used to analyze the direction of force that would develope displacement at the inclined tunnel surface, and that direction could be the optimum direction of steel rib. The support efficiency of steel rib could be maximized when the steel rib was installed to resist the displacement of the tunnel. Three directions which were recommended for the inclined tunnels in the Korea Tunnel Design Standard were used for the numerical models of steel rib direction. In conclusion, the results show that all displacement angle of the models are almost perpendicular to the tunnel surface regardless of face angle. So if the steel rib would be installed perpendicular to the inclined tunnel surface, the support efficiency of steel rib could be maximized.

• Journal of the Korean Geotechnical Society
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• v.21 no.9
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• pp.87-102
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• 2005

In the congested urban areas, tunnelling close to existing structures or services often occurs due to the lack of surface space so that tunnelling-induced ground movements may cause a serious damage to the adjacent structures. This study focused on the two dimensional laboratory model pile-soil-tunnelling interaction tests using a close range photogrammetric technique. Testing equipments and procedures were Introduced, particularly features of aluminium rods regarded as the frictional granular material. The experimental result showed that the photo imaging process by the VMS and EngVis programs proved to be a useful tool in measuring the pile tip movements during the tunnelling. Consequently, the normalised pile tip movement data for the influence zones can be generated by the laboratory model tests using the Photogrammetric technique. This study presents influence zones associated with the normalized pile tip settlements due to tunnelling in the cohesionless material. The influence zones were Identified by both a laboratory model test and a numerical analysis. The normalized pile tip movements from the model test were in good agreement with the numerical analysis result. The influence zones proposed in this study could be used to decide the reasonable location of tunnel construction in the planning stage. However, the scale of model pile and model tunnel sizes must be carefully adjusted as real ones for practical application considering the ground conditions at a given site.

• Journal of the Korean GEO-environmental Society
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• v.13 no.3
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• pp.29-37
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• 2012

This study is to find out the characteristics of the behavior of Geosyntehtic Reinforced Retaining Earth Wall(GRREW) through the laboratory experiment with the reduced-scale model, and to verify the effect of reinforcement by materials of GRREW. The loading tests after combining nonwoven geosynthetic, re-bar mesh nets and drainage blocks respectively among the components of the GRREW were performed in three cases of their slopes. In the cases of the behavior analysis including all of the components of the GRREW, the maximum horizontal displacement was generated 8.4mm at the location of 0.57H in the slope of 1:0.3; 3.8mm at the location of 0.57H in the slope of 1:0.6; 3.6mm at the location of 0.86H in the slope of 1:1.0. On average, the horizontal displacements of the GRREW were reduced by 83.8% against those of the original slopes. Lastly, seepage analysis and slope stability analysis were performed by modelling section of field, to confirm the effect of installation of drainage block in GRREW. We can confirm to compare increasing the slope safe factor and decreasing ground water in accordance with drainage blocks.

• Journal of the Korean Geotechnical Society
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• v.34 no.1
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• pp.47-57
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• 2018

In recent years, vertical extension remodeling of apartment building is considered as one of the efficient ways to broaden and enhance the utilization of existing buildings due to the rapid development of population and decrement of land resources. The reinforcement of foundation is of great importance to bearing the additional load caused by the added floors. However, because of the additional load, the carried load by the existing piles would be in excess of its allowable bearing capacity. In this study, a conceptual construction method called preloading method was presented. The preloading method applies force onto the reinforcing pile before vertical extension construction. The purpose of preloading is to transfer partial load applied on the existing piles to reinforcing piles in order to keep each pile not exceeding the allowable capacity and to mobilize resistance of reinforcing pile by developing relative settlement. The feasibility and effect of preloading method was investigated by using finite numerical method. Two simulation models, foundation reinforcement with preloading and without preloading, were developed through PLAXIS 3D program. Numerical results showed that the presented preloading method is capable of sharing partial carried load of existing pile and develops the mobilization of reinforcing pile's frictional resistance.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.637-648
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• 2005

Innovative prestressed steel plate girders were presented in this study. Hot-rolled H beams were loaded first, then relatively high-strengthsteel plates were welded on the top and bottom flanges of preloaded H beams. Finally, high prestressed plate (HiPP) girder was manufactured by simply releasing prestresses of rolled beams. To verify prestress distributions induced in this girder, the experimental study was conducted and some guidelines to manufacture these girders effectively were addressed. In addition, methods to determine the allowable bending stress of HiPP girders and to check welding stresses were addressed for design of temporary bridges. The efficiency and effectiveness of the present girder were demonstrated through design examples of temporary bridges adapting the prestress-induced girder or the plate girder of the same section without prestresses. As a result, it has been found to be possible that the span length of HiPP girders for temporary bridges is longer than that of girders without prestresses.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.4
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• pp.114-123
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• 2012

This study is aimed to assess the stability of cable bridge by determining the geometric shape of the suspension bridge among the domestic coastal structures in public use after their completion of construction and the displacement of the target suspension bridge after public use. For this purpose, this study calculated the length between pylon piers for each period, sag, sag ratio and the displacement of pylon. Compared to the management standards for each step across different pylon behaviors of the target suspension bridge, this study found that the target suspension bridge behaves stably within the maintenance standards. To identify the behaviors of a suspension bridge accurately, the priority is put on the determination of geometric shape. Therefore, it is required to determine the surveyed shape model on a regular basis across public use period and increased traffics, which is expected to contribute considerably to ensuring the stability of the suspension bridge in its maintenance.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.1
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• pp.83-93
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• 2017

Recently, the development of multi-purpose tunnel that has functions of roads and waterways has been attention for efficient utilization of underground space. However, there is no study on the multi-functional tunnels behavior for the convert of iterative function and change of water pressure. In this study, the vulnerable section was analyzed due to repeated functional change. A basic review was implemented for the operation of the multi-purpose double-deck tunnel. Also, the vulnerable section for convert of iterative function of multi-functional tunnel has been analyzed by simulation. Management of multi-functional tunnel should considered in various analyzed and some problems. The criteria for management of multi-functional tunnels is proposed.

• Journal of Korean Society of Steel Construction
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• v.22 no.6
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• pp.599-608
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• 2010

Steel trusses that act compositely with concrete slabs have proven to be an economical system for long-span floors. The composite action is generally achieved by providing shear connections between the steel top chord and the concrete topping. The composite sections have greater stiffness than the sum of the individual stiffnesses of the slab and truss. Therefore, steel trusses that act compositely with concrete slabs can carry larger loads and are stifferand less prone to transient vibration. During the tests that were performed in this study, the crack pattern and deflection of the beam of the composte truss were investigated. The test results were compared with the results for the noncomposite trusses.