• Korean Journal of Agricultural Science
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• v.23 no.1
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• pp.13-24
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• 1996

The following results were obtained by analyzing the displacement, strain and stability of ground at the soft ground excavation using sheet pile. 1. Before setting the strut, the horizontal displacement was large on the upper part of excavated side, but after setting the strut, it showed concentrated phenomenon while being moved to go down to the excavated side. 2. After setting the strut, the displacement of sheet pile was rapidly decreased about a half compared with before setting the strut. The limitation of excavation depth was shown approximately GL-8m after setting double stair strut. 3. Maximum shear strain was gradually increased with depth of excavation, and local failure possibility due to shear deformation at the bottom of excavation was decreased by reinforcement of strut. 4. Maximum horizontal displacement of sheet pile at GL-7.5m was shown 0.2% of excavation depth in elasto-plastic method, and 0.6% in finite-element methods, and the maximum displacement was occurred around the bottom of excavation. 5. To secure the safety factor about penetration depth in the ground of modeling, D/H should be more than 0.89 in the case of one stair strut, and more than 0.77 in the case of double stair strut. 6. The relation of safety factor and D/H about the penetration depth was appeared, Fs=0.736(D/H) + 0.54 in the case of one stair strut, and Fs=0.750(D/H) + 0.62 in the case of double stair strut.

• Tunnel and Underground Space
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• v.17 no.2 s.67
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• pp.109-118
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• 2007

The excavation damaged zone (EDZ) is an area around an excavation where in situ rock mass properties, stress condition. displacement. groundwater flow conditions have been altered due to the excavation. Various studies have been carried out on EDZ, but most studies have been focused on the mechanical bahavior of EDZ by in situ experiment. Even though the EDZ could potentially form a high permeable pathway of groundwater flow, only a few studies were performed on the analysis of groundwater flow in EDZ. In this study, the' hydraulic EDZ' was defined as the rock Lone adjacent to the excavation where the hydraulic aperture has been changed due to the excavation. And hydraulic EDZ (hydraulic aperture changed zone) estimated by two-dimensional DEM program was considered in three-dimensional DFN model. From this approach the groundwater flow characteristics corresponding to hydraulic aperture change were examined. Together. a parametric study was performed to examine the boundary conditions that frequently used in DFN analysis such as constant head or constant flux condition. According to the numerical analysis, hydraulic aperture change induced by the hydraulic-mechanical interaction becomes one of the most important factors Influencing the hydraulic behavior of jointed rock masses. And also from this study, we suggest the proper boundary condition in three-dimensional DFN model.

• Journal of Convergence for Information Technology
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• v.11 no.8
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• pp.84-91
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• 2021

In the 21st century, a number of storm and flood disasters caused by rapidly changing climate change is increasing, and the number of flood accidents at construction sites is also increasing. However, no specific reduction measures have been presented and thereby safety management to prevent flood accident need to be improved. Therefore, in this study, the inundation pattern by downpour at the excavation site was interpreted and the inundation risk quantification method was used to classify the risk magnitude. Finally, using the fish-bone diagram, we derived the major reasons of inundation accident at construction site systematically. The simulation results showed that the inundation depths of small-scale excavation sites and excavation sites exceeded 3 m due to the fluid flowing through the excavation surface. In addition, depending on the excavation site, a high velocity temporarily observed and decreased due to the storage effect, or high velocity surpassing 10 m/s continued. Since this type of flooding can pose a risk to most or all workers, if proper management measures are insufficient, fatal damage to life and property could occur. Consideration of the roots of these disasters is judged to be helpful in understanding the causes of inundation accidents that result in casualties and presenting accident reduction measures.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.998-1007
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• 2006

In former times, It is obvious that the earth retaining cantilever wall using stabilizing piles is definitely superior to the other methods due to economical efficiency and the efficiency of construction through model tests using a soil tank and practical application(Kim, 2006). However, this method was not proved in theoretical basis from the viewpoint of geotechnical engineering. Accordingly, a variety of model experiments in order to analyze the behavior of the earth retaining cantilever wall and stabilizing piles according to excavation step and earth pressure and stress acting on stabilizing piles according to excavation step were performed. On the basis of analyzing the result of model tests using a soil tank, this study suggests failure mechanism of clods and a method calculating virtual supported point. In addition, this study contributes to developing the analyzing method of retaining piles, stabilizing piles and beams connecting two piles and, this study helps this method to be established as a new design method through analyzing the results of model tests using a soil tank.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.808-813
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• 2009

Top-down method is widely used for urban area construction for its advantages in reducing environmental problems such as dust and noise, and saving construction cost depending on given conditions of a construction site. Because the excavation and construction of super- and sub-structures of the building have to be proceeded simultaneously, a column has to be embedded prior to excavation. This column is called a pillar column or pre-founded column. Usually a wide flange section is used for these columns. To place the columns, usually the diameter of casing holes needs to be larger than the section of the wide flange itself in order to accommodate a couple of tremie pipes for pouring concrete. In this paper, a newly developed method of using circular pipe as an alternative to the existing wide flange section is discussed. The crucial part of the new method is to develop a connection between the circular column and concrete flat slabs. For shear force transfer from concrete slab to the concrete filled tube (CFT) column, shear jackets with studs and shear bands are proposed. The studs are welded on the jackets at shop and placed around the circular column on site. The shear bands are welded on the outer side of the CFT at shop and inserted into ground with the CFT. Test results and application of the method to a construction site are also provided in this paper.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.129-136
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• 1999

The use of strut preloading method is gradually increasing in braced excavations in Korea. And it is necessary to analyse the effects of strut preloading on the wall deflection, bending moment and strut axial force etc. In this study, by using the analysis method of beams on elasto-plastic foundations, parametric studies of correlation between preloading and earth retaining structures in sandy soils were peformed in strut preloading application. As results, about 50% of design strut load was effective as a preloading force in considering the displacement and member forces of structures. And at least the effective stiffness of strut should be over 25% of the ideal value in order to restrain the excessive increase of wall deflection and bending moments. In order to protect excessive movements in braced excavation, to preload the strut was rather effective way than to increase the stiffness of strut and braced wall, but the excessive axial force of strut should be checked simultaneously.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.166-178
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• 1991

Using FLAC, which is an explicit finite difference code written for analysis of problems in geotechnical engineering, a particular example 2 in the Korean Geothechnical Society News has been analysed. The elastoplasticity formulation in FLAC assumes an elastic, perfectly plastic solid in plane strain which conforms to a Mohr-Coulomb yield condition. During tunnel excavations by stages, stresses and diaplacements in region around the tunnel varies according to distance from the face of tunnel and installation of tunnel supports, and soon. In this analysis, the three dimensional support effect of the rock mass during the process of excavation is simulated by using the stress distribution method, and varying the material constants of shotcrete in each stage also considered. The maximum convergency is occured at the crown of the tunnel and estimated to be about 12mm.

• Geomechanics and Engineering
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• v.11 no.2
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• pp.269-288
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• 2016

The jointed rock mass behavior often plays a major role in the design of underground excavation, and their failures during excavation and in operation, are usually closely related to joints. This research attempts to evaluate the effects of two basic geometric factors influencing tunnel behavior in a jointed rock mass; joints spacing and joints orientation. A hybridized indirect boundary element code known as TFSDDM (Two-dimensional Fictitious Stress Displacement Discontinuity Method) is used to study the stress distribution around the tunnels excavated in jointed rock masses. This numerical analysis revealed that both the dip angle and spacing of joints have important influences on stress distribution on tunnel walls. For example the tensile and compressive tangential stresses at the boundary of the circular tunnel increase by reduction in the joint spacing, and by increase the dip joint angle the tensile stress in the tunnel roof decreases.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.43-48
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• 2001

To overcome the disadvantages of conventional excavation technology, various trenchless (or excavation free, or no-dig) repair-reinforcement technologies have been developed and tried. But trenchless technologies so fat developed have some brawbacks such as high cost and inconvenience of operation. In this study, a repairing-reinforcing process for underground pipes with glass fiber fabric polymer composites using VARTM(Vacuum Assisted Resin Transfer Molding) has been developed. The developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than those of the conventional trenchless technologies. For the reliable operation of the developed method, a simple method to apply pressure and vacuum to the reinforcement was devised and flexible mold technology was tried. Also, resin filling and cure status during RTM process were monitored with a commercial dielectrometry cure monitoring system, LACOMCURE. From the investigation, it has been found that the developed repairing-reinforcing technology with appropriate process variables and on-line cure monitoring has many advantages over conventional methods.

• Journal of the Korean Geotechnical Society
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• v.16 no.2
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• pp.23-30
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• 2000

The use of strut-preloading method is gradually increasing in braced excavations in Korea. And it is necessary to analyze the effects of strut preloading on the wall deflection, wall bending moment and strut axial force, etc. In this study, by using the analysis method of beams on elasto-plastic foundations, measured data and calculated results of 2 sites are compared and parametric studies of correlation between preloading and earth retaining structures in sandy soils are carried out in strut preloading application. As results, about 50%~75% of design strut load is effective as preloading force in considering the displacement and member forces of earth retaining structures. And the effective stiffiness of strut should be at least 25% of th ideal value in order to restrain the excessive increase of wall deflection and bending moments. As one of some methods to prevent excessive movements in braced excavation, to preload the strut is confirmed as more effective way than to increase the stiffiness of strut in braced wall, if the excessive axial force of strut due to preloading can be avoided.