• Tunnel and Underground Space
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• v.14 no.4
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• pp.295-303
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• 2004

For the deep underground excavation site with the geological complexity of soft seam and hard rock, the numerical analysis and in-situ measurement on the behaviors of roadway and surrounding rock according to stepwise excavation of the steep soft seam are carried out. The strata behavior is modeled using elasto-plastic FEM considering the empirical failure criteria of Hoek ＆ Brown and the strain-softening model. Hydraulic pressure capsule, MPBX and tape extensometer are installed around the roadway for the in-situ measurement of rock stress and deformation. Despite the complexity of geology and excavation procedure, the elasto-plastic analysis considering the empirical failure criteria of Hoek ＆ Brown and the strain-softening model shows good agreement with the in-situ measurement. Comparison of numerical modeling with in-situ measurement enables to predict the behaviors of the roadway and to obtain design parameters for the excavation and support at depth.

• Tunnel and Underground Space
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• v.18 no.3
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• pp.226-238
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• 2008

The steel ribs which are used to enhance the supporting capability of the shotcrete are estimated to be very effective, but their characteristics depending on the types of steel support are not well understood enough to be considered in the design stage. This paper describes the behavior of the shotcrete reinforced by various types of steel supports. Through flexural toughness test, major strength parameters such as flexural tensile strength, equivalent flexural tensile strength and residual tensile strength were obtained and used in the numerical analyses. Test results show that steel rebar was not as dependable as H-beam or lattice girder but close examination of the test results revealed that the specimen was failed in shear because of the shorter span than desired. Therefore tests on the properly dimensioned specimens are necessary for valid evaluation of the steel rebar reinforced shotcrete. In the first set of numerical stability analyses, shotcrete and steel supports were modelled separately. Then compared with the second set of analyses in which shotcrete and steel supports were regarded as a composite material. The two results coincided reasonably and this equivalent model turned out to be useful.

• Tunnel and Underground Space
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• v.13 no.4
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• pp.304-315
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• 2003

In this paper, the DDA method with a new hydro-mechanical algorithm is used to study the effect of rock discontinuities on uplift and seepage in concrete gravity dam foundations. This paper presents an alternative method of predicting uplift and seepage at the base of concrete gravity dams. A sensitivity analysis was carried out to study the importance of several parameters on dam stability such as the orientation, spacing, and location of discontinuities. The study shows that joint water flow and adverse geological conditions could result in unusual uplift at the base of concrete gravity dams, well in excess of what is predicted with the classical linear or hi-linear pressure assumption. It is shown that, in general, the DDA program with the hydro-mechanical algorithm can be used as a practical tool in the design of gravity dams built on fractured rock masses.

• Structural Engineering and Mechanics
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• v.72 no.5
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• pp.541-555
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• 2019

Wind induced dynamic responses on hyperbolic cooling tower (HCT) shells are complicated functions of structure and wind properties, such as the fundamental frequency f_min, damping ratio ζ, wind velocity V, correlationship in meridian direction and so on, but comprehensions on the sensitivities of the dynamic responses to these four factors are still limited and disagree from each other. Following the dynamic calculation in time domain, features of dynamic effects were elaborated, focusing on the background and resonant components σ_B and σ_R, and their contributions to the total rms value σ_T. The σ_R is always less than σ_B when only the maximum σ_T along latitude is concerned and the contribution of σ_R to σ_T varies with responses and locations, but the σ_R couldn't be neglected for structural design. Then, parameters of the above four factors were artificially adjusted respectively and their influences on the gust responses were illustrated. The relationships of σ_R and the former three factors were expressed by fitted equations which shows certain differences from the existing equations. Moreover, a new strategy for wind tunnel tests aiming at surface pressures and the following dynamic calculations, which demands less experiment equipment, was proposed according to the influence from meridian correlationship.

• Tunnel and Underground Space
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• v.25 no.1
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• pp.46-55
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• 2015

A water tube with detonating cord was devised to control the blast dust. Water diffusion experiments with different detonating cord positions were conducted during the series of experiments to optimize the design parameters of the tube. Images from high speed camera were analyzed to evaluate the results. AUTODYN program was adopted to simulate the diffusion process of water and compared with the images. Diffusion of water shows cross flow in case of external charge while the internal case shows radial flow. A bubble ring was formed during the numerical analysis of internal charge case as occurred in underwater blast. An additional bubble ring was formed by the reflection pressure from the ground. And the Weber number was determined as sufficient for spray atomization performance of the water tube.

• Tunnel and Underground Space
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• v.24 no.1
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• pp.1-10
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• 2014

This paper presents a case study that performed simulations on shovel-truck haulage systems in an open-pit mine by considering truck's breakdown and crusher's capacity. The SSangyoung limestone open-pit mine in Korea was selected as a study area and investigated to design the simulation algorithms. The GPSS/H simulation language is used to implement the simulation algorithms as a console application(simulator). The values of input parameters for simulator were measured by field investigation in the study area. The simulation results showed that 7 trucks can maximize the daily profit of haulage operations(i.e., 73,775 USD) when considers the frequency of trucks' breakdown as 1/40 $hour^{-1}$. In addition, the crusher capacity of 1300 tph is required to improve the efficiency of shovel-truck haulage systems in the study area.

• Tunnel and Underground Space
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• v.33 no.1
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• pp.10-28
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• 2023

Long-term shear behavior of the rock discontinuities should be analyzed and its stability should be evaluated to ensure the long-term stability of a high-level radioactive waste disposal repository. The long-term shear behavior of the discontinuities can be modeled with creep and RSF models. The shear creep test, velocity step test, and slide-hold-slide test can be performed to determine their model parameters or analyze the shear behavior by experiments under various conditions. Testing apparatuses for direct shear, triaxial compression, and biaxial shear were mainly used and improved to reproduce the thermo-hydro-mechanical conditions of local bedrock, and it was confirmed that the shear behavior could vary. In order to design a high-level radioactive waste disposal site in Korea, the long-term behavior of rock discontinuities should be investigated in consideration of rock types, thermo-hydro-mechanical conditions, metamorphism, and restoration of shear resistance.

• Tunnel and Underground Space
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• v.26 no.2
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• pp.87-99
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• 2016

We developed a Windows-based program for discrete event simulation of truck-loader haulage systems in an underground mine. The Daesung MDI limestone mine located in Samcheok City, Gangwon Province, Korea was selected as the study area to design the program. The developed program is composed of the graphic user interface (GUI) and simulation engine implemented by Visual Basic.NET 2012 and the GPSS/H simulation language, respectively. When a user sets up input parameters for the discrete event simulation through GUI, the program activates the simulation engine, and then simulation results are displayed on GUI. This paper describes the details of the program development as well as its applications to the study area to determine the optimal number of trucks dispatched at each loading point under different operating conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.6
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• pp.637-652
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• 2013

After studying the characteristics of three different evaluation methods of rock load; namely theoretical method, empirical method and numerical method, there were too many limitations for them to be applied on tunnels. Therefore, in this research paper, the method based on numerical analysis is selected to use as this method is the most reasonable one since it considers all parameters that are necessary for rock load estimations, and it also considers the interaction between ground and tunnel support. The critical shear strain concept formulated by Sakurai (1981) was used in order to measure exact rock load values based on numerical analysis. Evaluation on a Level 1 rock load height, which is depicted by the stable region in the graph shows that rock load is not affecting between ground grade 1~3, and it was evaluated that the fourth and fifth grades show less values of rock load height which led to the conclusion of a more economical design of concrete lining.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.5
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• pp.483-496
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• 2013

This paper presents the shield TBM technology in soft ground tunnelling. In order to perform this study, a scale model test was carried out using the developed small scaled shield TBM machine. The various instrumentations were conducted during the simulation of tunnelling. In addition, the ground behavior due to the shield TBM operation parameters was measured during the simulation. Based on the simulation results, the stability of the ground was evaluated and the fundamental shield TBM tunnelling technique in the soft ground was suggested. In conclusion, design's reliability through laboratory small scale model test about Shield-TBM section was obtained, and both the improvement plan for safety during construction and the construction plan for securing airport runway's safety during tunnel passing by Shield-TBM propulsion were suggested.