• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.611-618
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• 2005

In this research, the effect of rock mass weathering on the side shear resistance of drilled shaft socketed into weathered rock was investigated. For that, a database of 23 cast-in-place concrete piles with diameters varying from 400mm to 1,500mm were socketed into weathered igneous/meta-igneous rock at four different sites. The static axial load tests were performed to examine the resistant behavior of the piles, and a comprehensive field/laboratory testing program at the field test site was also performed to describe the in situ rock mass conditions quantitatively. No correlation was found between the compressive strengths of intact rock and the side shear resistance of weathered/soft rock. The ground investigation data regarding the rock mass conditions (e.g. $E_m,\;E_{ur},\;_{plm}$, RMR, RQD, j) was found to be highly correlated with the side shear resistance, showing the coefficients of correlation greater than 0.7 in most cases. Additionally, the applicability of existing methods for the side shear resistance of piles in rock was verified by comparison with the field test data. The existing empirical relations between the compressive strength of intact rock and the side shear resistance(Horvath (1982), Rowe & Armitage(1987) etc.) appeared to overestimated the side shear resistance of all piles tested in this research unless additional consideration on the effect of rock mass weathering or fracturing was applied. The existing methods which consider the effect of rock mass condition were modified and/or extended for weathered rock mass where mass factor j is lower than 0.1, and RQD is below 50%.

• Tunnel and Underground Space
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• v.5 no.1
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• pp.1-10
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• 1995

The behavior of a jointed rock mass depends mainly on the geometrical and mechanical properties of joints. The failure mode of a rock mass and kinematics of rock blocks are governed by the orientation, spacing, and persistence of joints. The mechanical properties such as dilation angle, shear strength, maximum closure, strength of asperities and friction coeffiient play important roles on the stability and deformation of the rock mass. The normal and shear behaviour of a joint are coupled due to dilation, and the joint deformation depends also on the boundary conditions such as stiffness conditons. In this paper, the joint constitutive law including the dilatant behaviour of a joint is numerically modelled using the edge-to-edge contact logic in distinct element method. Also, presented is the method to quantify the input parameters used in the joint law. The results from uniaxial compression and direct shear tests using the numeical model of the single joint were compared to the analytic results from them. The boundary effect on the behaviour of a joint is verified by comparing the results of direct shear test under constant stress boundary condition with those under constant stiffness boundary condition. The numerical model developed is applied to a complex jointed rock mass to examine its performance and to evaluate the effect of joint dilation on tunnel stability.

• Journal of fish pathology
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• v.32 no.1
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• pp.1-8
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• 2019

Rock bream iridovirus (RBIV) is a member of the Megalocytivirus genus that causes severe mortality to rock bream (Oplegnathus fasciatus) with characteristic clinical signs of spleen enlargement. In this study, we assessed spleen size and RBIV copy number patterns in RBIV-infected rock bream to determine lethal and safe levels of virus copy number/spleen index that may define disease progress. We found that rock bream infected with RBIV ($1.1{\times}10^7virus\;copy\;number/100{\mu}l$) and held at 29, 26, 23 or $20^{\circ}C$ exhibited significantly higher levels of spleen size compared to $17^{\circ}C$. In dead condition (100% mortality at $20{\sim}29^{\circ}C$), the spleen index ($spleen\;weight/fish\;weight{\times}100$) and virus copy number were 3.00~5.38 and $10^6{\sim}10^8/{\mu}l$, respectively. Conversely, in survived condition (0% mortality at $17^{\circ}C$), spleen index and virus copy number was as low as not-infected control ($0.34{\sim}1.22/10^0{\sim}10^1/{\mu}l$, respectively). These findings suggest that spleen index can be an indicator of disease severity of RBIV disease.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.471-477
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• 1999

A new stress, load and displacement controlled direct shear apparatus has recently been developed at the Hyundai Institute of Construction Technology This direct shear apparatus is capable of testing of rock joint under constant normal stiffness, constant normal stress or constant normal load boundary conditions. This paper describes this direct shear apparatus and illustrates results of shear tests at constant normal stress condition, constant normal load condition and constant normal stiffness condition with dental stones which have a same joint roughness and unconfined compressive strength.

• Tunnel and Underground Space
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• v.13 no.5
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• pp.353-361
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• 2003

For RMR and Q rock mass classification at the design and construction stage, evaluation of groundwater condition is usually based upon the experience due to the restriction of available methods. Based on the results of Taejon LNG Pilot Cavern which acquire joint water pressure, inflow rate of ground water and hydraulic conductivity model, estimates from numerical analysis and analytical solutions were compared to verify each evaluation method. As the result, the Raymer(2001) approach was found to be efficient for estimating inflow rate and corresponding value.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.277-284
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• 1999

This study describes the influence factors related to slope failure pattern and dimension in the southern Kyounggi area. Intrusive and metamorphic rocks are distributed in the study area. Geological condition, rainfall property and slope geometry are influence on slope failure characteristics in the study we& Geological factors related to slope failure are rock type, geological structure and weathering condition. Because of deep soil (RS-CW) depth of granite region, circular failure type is major failure pattern in granite region. Almost granite slopes with circular or surface failure pattern are failed during heavy rainfall season. But typical wedge failure type related to geological structure factor is a main failure pattern of metamorphic rock slope. Additionally failure dimension is influenced by geological factors and several factors, i.e. natural slope condition, failure type, rainfall intensity and etc. failure height/width ratio and thickness/length ratio of granite slope are 0.88 and 0.23. But the ratios of metamorphic rock slope are 1.36 and 0.19.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.3
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• pp.45-56
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• 2001

It is very important to survey in construction for acquiring informations about geological structure which influence the tunnel construction. Usually, TSP(Tunnel Seismic Prediction) one of the seismic survey method in tunnels in Korea has been used for prediction of geological condition ahead of tunnel face, but in this study HSP(Horizontal Seismic Profiling) was used. As a result of field application, we predicted that there exist rock discontinuity such as fault, joints and bedding planes. In addition, RMR value from rock mass evaluation coincided with that from seismic survey for rock condition. We compared with rock classifications and evaluation results for proving.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.4
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• pp.11-20
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• 1997

The aseismic capacity of a traditional three-bay-straw-roof wooden house for rock site condition is quantitatively estimated. One 1/4 scale model was tested for the Nahanni Earthquake with peak ground accelerations from 0.1g to 0.6g. The natural frequency of the wooden house in elastic range is 1.66 Hz and 2.15 Hz in longitudinal and transversal direction, respectively. Damping ratio of the house in elastic range is 7%. The horizontal acceleration response of the house is significantly reduced compared with the input motion due to the nonlinear inelastic characteristics of the Sagae-machum joint of the frame. The traditional wooden house has high aseismic capacity in the rock site condition where high frequency contents of motion are predominant.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.17-26
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• 2014

Tunneling-induced displacement in a jointed rock mass is an important factor to control tunnel stability and to secure a demanded space and construction quality. The magnitude of the inducible displacements is significantly affected by an elastic modulus and therefore, in a rock mass where a joint controls tunnel behavior, it is very important to estimate an elastic modulus of jointed rock mass reliably. Elastic modulus of jointed rock mass is affected by many factors such as rock type, joint condition, and loading condition. Nevertheless, most existing studies were focused on rough empirical relationships based on compressive loading conditions, which are different from tunnel excavation loading conditions, without a systematic approach of rock, joint, and loading conditions together. Therefore, this study considered rock and joint conditions systematically to estimate an elastic modulus of jointed rock mass under tunnel excavation loading. The controlled factors considered in this study are rock types and joint conditions (joint shear strength, joint inclination angle, number of joint sets, and joint spacing). Numerical parametric studies have been carried out with a consideration of different rock and joint conditions; the results have been compared with existing empirical relationships; and charts of elastic modulus change of different rock and joint conditions have been provided. The results are expected to have a great practical use for estimating the convergence induced by tunnel excavation in jointed rockmass.

• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.83-95
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• 2017

This study examined the magnitude and distribution of earth pressure on the excavation wall in jointed rock mass by considering different groundwater conditions under various rock types, joint inclination angles, and earth pressure coefficients. Based on a physical model test (Son and Park, 2014), extended studies were conducted considering rock-structure interactions based on the discrete element method, which can consider the joints characteristics of rock mass. The results showed that the earth pressure was highly influenced by the groundwater condition as well as the rock type, joint inclination angle, and earth pressure coefficient. The results were also compared with Peck's earth pressure for soil ground, and clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground.