• Geomechanics and Engineering
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• v.13 no.6
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• pp.997-1010
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• 2017

The black box model is a relatively new option for nonlinear dynamic system identification. It can be used for prediction problems just based on analyzing the input and output data without considering the changes of the internal structure. In this paper, a black box model was presented to solve unconstrained overlying strata movement problems in coal mine production. Based on the black box theory, the overlying strata regional system was viewed as a "black box", and the black box model on overburden strata movement was established. Then, the rock mechanical properties and the mining thickness and mined-out section area were selected as the subject and object respectively, and the influences of coal mining on the overburden regional system were discussed. Finally, a corrected method for height prediction of the fractured zone was obtained. According to actual mine geological conditions, the measured geological data were introduced into the black box model of overlying strata movement for height calculation, and the fractured zone height was determined as 40.36 m, which was comparable to the actual height value (43.91 m) of the fractured zone detected by Double-block Leak Hunting in Drill. By comparing the calculation result and actual surface subsidence value, it can be concluded that the proposed model is adaptable for height prediction of the fractured zone.

• Tunnel and Underground Space
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• v.3 no.2
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• pp.167-174
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• 1993

Index tests are useful because they are rapid and cheap-and if bias is known the fundamental property can be estimated, as when estimating the compressive strength or the tensile sterngth from the rock test hammer value. Index tests which have proved to be very useful are the rock test hammer, the point load test and sonic velocity test. These can provide index values in their owing right or be used to estimate the compressive strength, the tensile strength and elastic modulus. Because of the heterogeneous and fractured nature of rock, many index tests have been developed for a variety of purposes, e.g.for use in rock mass classification schemes.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.453-454
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• 2004

Hydrogeochemical and isotopic characteristics were investigated for groundwater of Tertiary basin in southeastern part of Korea where deep drilling is in progress for geothermal investigation. According to geology, aquifer was distinguished as alluvial, tertiary sedimentary bedrock (bedrock groundwater), and fractured volcanic rock (deep groundwater). Groundwater of each aquifer is distinctively separated in Eh-pH conditions and concentrations of Cl, F, B and HCO$_3$. Deep groundwater has very low level 3H and 14C whereas alluvial groundwater has those of recent precipitation level. However one of deep groundwater show mixed characteristics in terms of hydrochemistry which indicates effect of pumping. Deep groundwater have temperature of 38 to 43$^{\circ}C$ whereas bedrock and alluvial groundwater have temperature less than 2$0^{\circ}C$. Fractured basement rock aquifer has different hydrogeologicalsetting from bedrock and alluvial aquifer considering hydrogeochemical and isotopic characteristics, and temperature.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05b
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• pp.769-774
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• 1995

In this study, a transport model was developed in order to analyze and predict the transport behaviors of radionuclides mediated by pseudo-colloid in the fractured rock media. It was resulted that the transport of Pu-239 was faster than Ni-63 because pseudo-colloid formation constant of Pu-239 was greater than that of Ni-63. Also, the effect of pseudo-colloid formation on the transport of a radionuclide was shown to be very significant when the apparent pseudo colloid formation constant, $K_{ap}(m^{3}/kg)$, was greater than 100. Thus, it can be concluded that acceleration of radionuclide migration may be occurred because the pseudo-colloid formation of radionuclides increases the amount of mobile components in the solution and consequently decreases the amount of radionuclides adsorbed on the stationary solid medium.

• Tunnel and Underground Space
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• v.8 no.1
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• pp.17-25
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• 1998

This paper investigates coupled thermal, mechanical and hydraulic phenomena in deep rock mass especially for underground heat storage system. Firstly, concepts of underground heat storage were presented and coupling phenomena in this area were illustrated. In order to understand the basic mechanism of thermal, hydraulic and deformation behavior in rock cavern disturbed by thermal gradient about 10$0^{\circ}C$, various numerical experiments were conducted using several codes. The study involves the behavior of fractured rock mass including rock joint. In spite of the limitation of codes modelling fully coupled effects, these codes could be applied in analysis of underground heat storage. The heat loss in rock mass, which is a major factor in heat storage, is insignificant in all results.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.59-72
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• 2022

This study employed a 3-D numerical analysis based on the distinct element method to estimate the strength and deformability of a Cretaceous biotite granitic rock mass at Gijang, Busan, Korea. A workflow was proposed to evaluate the scale effect and the representative elementary volume (REV) of mechanical properties for fractured rock masses. Directional strength and deformability parameters such as block strength, deformation modulus, shear modulus, and bulk modulus were estimated for a discrete fracture network (DFN) in a cubic block the size of the REV. The size of the mechanical REV for fractured rock masses in the study area was determined to be a 15 m cube. The mean block strength and mean deformation modulus of the DFN cube block were found to be 52.8% and 57.7% of the intact rock's strength and Young's modulus, respectively. A constitutive model was derived for the study area that describes the linear-elastic and orthotropic mechanical behavior of the rock mass. The model is expected to help evaluate the stability of tunnels and underground spaces through equivalent continuum analysis.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.361.2-361
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• 2001

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.121-128
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• 1998

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.276.1-276
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.344.3-344
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• 2002