• The Journal of Engineering Geology
• /
• v.19 no.3
• /
• pp.323-330
• /
• 2009

Electrical resistivity survey is applied for estimation of inferred fault and fractured zone in civil engineering and environment field. While 15 m diameter and 3 lines tunnels are excavated. It is recognized that core stone and fractured zone is existed in the weathered slope of the entrance to a tunnel. To make confirmation geological characteristics, dipole-dipole electric resistivity survey was carried out in weathered slope of the entrance to a tunnel. Core stone distribution and fracture zone characteristics are estimated by reverse analysis and 2D-resistivity structure using FDM.

• Journal of the Korean Geosynthetics Society
• /
• v.17 no.1
• /
• pp.33-43
• /
• 2018

Two-row Overlap Pile wall is a novel retaining wall system with high flexural rigidity and waterproofing for deep excavation support currently being developed in Korea. The Two-row Overlap Pile wall is constructed by making an overlap between consecutive four-axis (or two-axis) auger piles which themselves are overlapped and arranged in zigzag manner. In this study, the flexural rigidity of the Two-row Overlap Pile wall, including the effect of cross-sectional shape, was examined using both theoretical and numerical approaches. The results of investigation suggested that the Two-row Overlap Pile wall formed with two-row piles exhibit greatly higher flexural rigidity than conventional one-row pile walls such as Cast in place pile (CIP) and Secant pile wall (SPW), whereas the effect of overlap length between piles on the flexural rigidity is relatively minimal.

• Tunnel and Underground Space
• /
• v.20 no.4
• /
• pp.252-259
• /
• 2010

In urban tunnels, namely, in case there are residents in the near distance, we normally use non-vibration and ambient vibration which are not blasting methods because it’ impossible to meet the blasting vibration regulation with only normal explosives. However, non-vibration methods not only cause increase of excavating cost, but need much time than explosives. Generally, the lower velocity explosives with 2,000 m/s VOD have been applied to ambient vibration blasting in open cut area, but difficult in tunneling in its use. However, by charging the hole together with lower velocity explosives and normal explosives, we have got the result which shows 20~30% vibration decrease compared with using only normal explosives. Therefore, I’ like to suggest the blasting method which is able to do as ambient vibration using lower velocity explosives mixed with normal explosives in urban tunnel and the area which is adjacent to security facilities within the vibration regulation.

• Tunnel and Underground Space
• /
• v.15 no.4 s.57
• /
• pp.250-263
• /
• 2005

Progressive and localized brittle failures around an excavated opening by the overstressed condition can act as a serious obstacle to ensure the stability and the economical efficiency of construction work. In this paper, the characteristics of the brittle failure around an circular opening with stress level was studied by the biaxial compressive test using sealed specimen and by the numerical simulation with $PFC^{2D}$, one of the discrete element codes. The occurring pattern and shape of the brittle failure around a circular opening monitored during the biaxial loading were well coincided with those of the stress induced failures around the excavated openings observed in the brittle rock masses. The crack development stages with stress level were evaluated by the detailed analysis on the acoustic emission event properties. The microcrack development process around a circular opening was successfully visualized by the particle flow analysis. It indicated that the scaled test had a good feasibility in understanding the mechanism of the brittle failure around an opening with a high reliability.

• Journal of the Korean Institute of Gas
• /
• v.4 no.2 s.10
• /
• pp.37-45
• /
• 2000

The underground buried pipelines of Natural gas are relatively safer than any other pipelines of chemical plants, because Natural gas is non-corrosive fluid. But Natural gas is supplied normally the downtown area. So, it may be a disaster because of corrosion which is caused interference facilities, environment and third party accident which is caused facilities construction. Especially, it is very difficult to find out and inspect damages of pipeline because of buried pipelines. Therefore this paper approached to select and manage risk region pipelines according to introduction of underground buried pipeline's risk concept. Risk was indicated three parts - corrosion factor, design and construction factor, maintence and management factor - in this paper, Therefore qualitive risk of pipelines showed score as quantitative number. Also it was thought to be helpful in confidence and safety management that the concept of key index and failure supplementation measures to cost introduces this program. We developed this risk assessment program using visual basic tool and interfaced GIS.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.18 no.4
• /
• pp.341-354
• /
• 2016

This article is to apply the tunnel support system selected after comparatively analyzing of RMR and tunnel instrumentation between the tunnel behavior characteristic predicted through geotechnical investigations and the numerical analysis at the design stage and the properties deformation occurred at the construction stage. This attempt results from the behavior characteristic of the tunnel excavation ground shown differently in accordance with the ground quality and reinforcement method. This, therefore, provide the data and results analysed the actual decision RMR-crown settlement & convergence and reduction of material property of ground as parameters. Also, it's shown that the tunnel designer is able to predict tunnel behavior characteristic when designing in bedrock areas excessively distributed faults and fractured zones.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.18 no.6
• /
• pp.557-568
• /
• 2016

Squeezing is a phenomenon that may occur in deep tunneling and could bring about a large plastic deformation, tunnel closure and collapse of tunnel supports. Therefore, quantitative estimations of deformation and stress from squeezing and its possibility are necessary for establishment of a rational tunneling method. This study carried out three dimensional numerical analyses using a strain softening model in order to simulate the behaviour of squeezing and to estimate deformation and yield area around tunnels quantitatively. Numerical analyses were performed for 42 cases of various stress and strength conditions. As a result, the maximum tangential stress and strength of rock mass ratio could estimate plastic deformation and yield depth around tunnels and equations of relations between them were proposed.

• Journal of the Korean Geosynthetics Society
• /
• v.17 no.2
• /
• pp.19-31
• /
• 2018

Recently the ground subsidence which seriously weakens the safety of cities tends to increase. The purpose of this paper is to develop the materials by using industrial by-products for the application to emergency restoration process in case of ground subsidence. In this paper the laboratory tests including pH test, initial setting test, unconfined compressive strength test, and flow test were performed in order to evaluate the design properties of Controlled Low Strength Material (CLSM). The field test was carried out for evaluating the performance for the early strength of CLSM and the workability for emergency restoration. Test results showed that the strength will be too high to re-excavate the ground when the cement ratio is more than 4%. The optimum mixing ratio appears to be most effective when the mixing ratio of the bottom ash and the gypsum is approximately 50:50 and the cement content is 2%.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.1
• /
• pp.83-97
• /
• 2000

In the present study, artificial neural network based on the multi-layer perceptron is used and an optimum model is chosen through the process of efficiency evaluation in order to develop a system predicting maximum displacements of the earth retaining walls at various excavation stages. By analyzing the measured field data collected at various urban excavation sites in Korea, factors influencing on the behaviors of the excavation wall are examined. Among the measured data collected, reliable data are further selected on the basis of the performance ratio and are used as a data base. Data-based measurements are also utilized for both teaming and verifying the artificial neural network model. The learning is carried out by using the back-propagation algorithm based on the steepest descent method. Finally, to verify a validity of the formulated artificial neural network system, both the magnitude and the occurring position of the maximum horizontal displacement are predicted and compared with measured data at real excavation sites not included in the teaming process.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.10 no.1
• /
• pp.1-15
• /
• 2008

Recently, because of the various factors by uncertainty of underground, the risks in tunnelling have been occurred increasingly. Therefore, it is very important to estimate and control the risks considering geotechnical conditions for tunnel stability and environmental problems by tunnel construction. In this study, the risk analysis for tunnel stability was carried out by classifying the risk factors such as ground support capacity, ground settlement, the inflow of groundwater into the tunnel and the damage by the earthquake. Also, the risk assessment for the environmental problems was performed by calculating the vibration and noise by blasting and the drawdown of the groundwater level caused by tunnel construction. Each risk factor was evaluated quantitatively based on the probabilistic and statistic technique, then it was analyzed the distribution characteristic along overall tunnel site. Finally, it was evaluated that how much each risk factor influences on the construction cost with a period for tunnel construction, so it is possible to perform reasonable tunnel design which was capable of minimizing the risks in the tunnel construction.