• Tunnel and Underground Space
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• v.8 no.2
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• pp.118-129
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• 1998

A three dimensional boundary element method-BEAP3D was applied to the stability analysis of the mine openings not only to improve the stability during mining operations but also to serve the evaluation of the mine openings for further utilization. Stability analysis on the stability of the room-and-pillar stopes underneath of the old mine openings and the openings to be created by the newly proposed sublevel stoping method at the Nowhado Pyrophyllite Mine, showed that rock mass around the old and new stopes would be stable. Six stopes of a sublevel stoping designed for the Choongmu Limestone Quarry would be stable, too. A sublevel stoping method consisting of six stopes was similarly suggested for the Keumpyung Quartzite Mine. The stability can be guaranteed through out six stopes. Since mining starts from the bottom 1st sublevel to the uppermost sublevel, the safety of the stopes will improve together with the mining process. It would highly be recommended to investigate in-situ rock properties and the rock stresses for future studies. Even though the rock around the uppermost part and bottom of all the stopes have a very high factor of safety, spot reinforcements such as rock bolting would be recommended to mitigate the intermediate and minor principal stresses acting in a tensile mode.

• Applied Biological Chemistry
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• v.35 no.6
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• pp.485-489
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• 1992

Plants are altered not only in the outward appearance but also in their physiological and biochemical properties with reaction to the environmental stresses; particularly, the biosynthetic system of protein in situ rapidly responds to this. In order to investigate the change of properties of polypeptides in rice plants induced by several stresses, the seedlings were subjected to exposure to NaCl, drought, and low and high temperatures, respectively, and then some aspects of polypeptide variations were compared. Without exception, the rice plant, which is somewhat tolerant to environmental change, shows the alteration in several polypeptides. Moreover, newly synthesized polypeptides were observed in response to stresses. The existing proteins for the primary metabolic pathways were markedly decreased as each treatment progressed.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.5-13
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• 1999

Maximum stress in pile is developed when it is driven. If the stress is greater than allowable stress of the pile, the pile will be damaged and result in stability problem. Therefore, the stress should be estimated correctly beforehand and overstress should be prevented during pile driving. There are many methods to estimate compressive stresses in concrete piles when they are driven. Nowadays, computer analysis on wave equation offers a satisfactory results. But. under certain circumstances, application of this method is difficult. Then, estimation of the stress utilizing simple formulae might be practical. In this study, relatively reasonable formulae were selected and the stresses which were measured in situ and calculated from the formulae were compared and analysed. The results show that the calculated values from Uto and Huyuki's formula were reasonably accurate and more accurate values were acquired if the values are modified by multiplying the reduction factors according to ground and construction conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.1
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• pp.31-40
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• 2006

The entrance and the exit structures of tunnels are often constructed on unfavorably soft soils (colluvial soils) as a result of environment-friendly design highlighted in recent years. For construction of such a tunnel, it is essential to secure sufficient bearing capacity of the lining supports as well as that of the surrounding soils. In this regard, H-shape steel-ribs with high stiffness are commonly used for lining supports. However, it was the past convention to ignore the effect of the steel-ribs in numerical evaluation of the structural safety. This study is intended to show how the shotcrete stresses are relieved by the steelribs, on the basis of numerical data obtained from 3-dimensional finite element analysis. The effect of steel ribs to shotcrete stresses is examined at different levels of application rates, i.e., 0%, 50%, 75% and 100% of the total stiffness. The data obtained from numerical analysis was compared with in-situ measurement. The effect of st eel ribs to shotcrete stresses was verified and appropriate total stiffness was proposed in the range of 50%~75%.

• Tunnel and Underground Space
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• v.21 no.2
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• pp.117-127
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• 2011

The purpose of this study is to demonstrate the effect of in-situ rock stresses on the deformability and permeability of fractured rocks. Geological data were taken from the site investigation at Forsmark, Sweden, conducted by Swedish Nuclear Fuel and Waste Man-agement Company (SKB). A set of numerical experiments was conducted to determine the equivalent mechanical properties (essentially, elastic moduli and Poisson's ratio) and permeability, using a Discrete Fracture Network-Discrete Element Method (DFN-DEM) approach. The results show that both mechanical properties and permeability are highly dependent on stress because of the hyperbolic nature of the stiffness of fractures, different closure behavior of fractures, and change of fluid pathways caused by deformation. This study shows that proper characterization and consideration of in-situ stress are important not only for boundary conditions of a selected site but also for the understanding of the mechanical and hydraulic behavior of fractured rocks.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.6
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• pp.354-359
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• 2000

A new method of measuring residual stress in micromachined film is proposed. An estimation of residual stress is performed by using least squares fit with an appropriate deflection modeling. an exact value of residual stress is obtained without any of the ambiguities that exist in conventional buckling method, and a good approximation is also obtained by using a few data points. Therefore, the test structures area could be greatly decreased by using this method. The measurement can be done more easily and simply without any actuation or any specific measuring equipment. The structure and fabrication processes described in this paper are simple and widely used in surface micromachining. In addition, in-situ measurement is available by using the proposed method when the test structure and the measurement structure are fabricated on a wafer simultaneously.

• Tunnel and Underground Space
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• v.7 no.1
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• pp.1-12
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• 1997

Engineering rock mass classification is extensively used to determine the reasonable support system throughout the tunneling process in the field. Selection of support system based on the results of engineering rock mass classification is simple and straight-forward. However, this method cannot consider the effect of in-situ stresses, mechanical properties of support material, and support installation time on the behavior or rock-support system To handle the various conditions encountered in the underground excavation sites rock-support system. To handle the various conditions encountered in th eunderground excavation sites rock-support interaction program has been developed. This program can analyze the interaction between rock mass and support materials and also can simulate the tunnel excavation-support insstallation process by controlling the support installation time and the stiffness of support system. Practical applicability of this program was verfied by comparing the results of support design to those from rock mass classification for virtual underground excavation at the drilling site KD-06 in Geoje island.

• Geotechnical Engineering
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• v.6 no.3
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• pp.31-40
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• 1990

The soil deformation due to a pile penetration in sandy soils has been analysed in model pile penetration tests. To simulate the actual ground conditions, especially the in-situ stress levee the tests were performed in a calibration chamber where both the vertical and the horizontal stresses could be applied separately. The deformation was monitored via 5 earth pressure cells. The results, were compared with the theortical values based on the theory of cavity expansion.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.135-142
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• 2000

A framework alternative to that of classical slope stability analysis is developed, wherein the soil mass is treated as a continuum and in situ soil stresses and strengths are computed accurately using inelastic finite element methods with general constitutive models. Within this framework, two alternative methods of stability analysis are presented. In the first, the strength characteristics of the soil mass are held constant, and the gravitational loading on the slope system is increased until failure is initiated by well-defined mechanisms. In the second approach, the gravity loading on the slope system is held constant, while the strength parameters of the slope mass are gradually decreased until well-defined failure mechanisms developed. Details on the applying both of the proposed methods, and comparisons of their characteristics on a number of solved example problems are presented.

• Geomechanics and Engineering
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• v.7 no.4
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• pp.431-458
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• 2014

Construction of a new cavern close to an existing cavern will result in a modification of the state of stresses in a zone around the existing cavern as interaction between the twin caverns takes place. Extensive plane strain finite difference analyses were carried out to examine the deformations induced by excavation of underground twin caverns. From the numerical results, a fairly simple nonparametric regression algorithm known as multivariate adaptive regression splines (MARS) has been used to relate the maximum key point displacement and the percent strain to various parameters including the rock quality, the cavern geometry and the in situ stress. Probabilistic assessments on the serviceability limit state of twin caverns can be performed using the First-order reliability spreadsheet method (FORM) based on the built MARS model. Parametric studies indicate that the probability of failure $P_f$ increases as the coefficient of variation of Q increases, and $P_f$ decreases with the widening of the pillar.