• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.218-231
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• 2006

Anisotropic/heterogeneous rock mass shows various deformation behavior types due to tunnelling because deformation behavior is largely controlled by the spacial characteristics of geological factors such as faults, joints and fractured zone in rock mass. In this paper 2-dimensional numerical analysis on the several influencing factors is performed considering fractured zone located near tunnel. This numerical analysis shows that deformation behavior of tunnel are very different according to the width and the location of fractured zone and supper method. However, 3-dimensional analysis is necessary to consider 3-dimensional geometrical characteristics sufficiently since discontinuity and fractured zone have 3-dimensional geometry. Also flexible design/construction guidelines for tunnelling are required to cope with uncertain ground condition and circumstance for technically safe and economic tunnel construction.

• Journal of the Korean GEO-environmental Society
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• v.11 no.1
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• pp.13-18
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• 2010

It is crucial to decide reasonably the parameters necessary for design through research on the characteristics of rock in order to analyze stability of rock structure. This article has conducted both pressure meter test, uniaxial and triaxial compression test to the areas of andesite or tuff located in local regions such as Yeosu, Gwangju, Yangsan, Busan, and Daejeon and has comparatively analyzed previously proposed estimative formulas. According to the result of estimating the deformation modulus through using the damping coefficient suggested by Nicholson & Bieniawski, when RMR is less than 60, it is desirable to use the result of the pressure meter test considering the damping coefficient. If the RMR value is over 60, however, the formula suggested by Kim Gyo-won has been proved to be the most applicable. Moreover, according to the result of comparing the RMR, adhesion, and angle of internal friction, both the adhesion and angle of internal friction best correspond to the formula proposed by Tsuchiya. Comparatively analyzing the relations between the rock deformation modulus and RMR and also suggesting the formula of calculating the shear strength parameter to use the RMR value, this study did not include the deformation modulus and shear strength parameter as factors to decide the RMR index. Since result can differ by several factors, it will be necessary afterwards to suggest practical estimative formulas applicable to the actual spots of Korea.

• Tunnel and Underground Space
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• v.17 no.5
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• pp.350-359
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• 2007

Most large cut slopes of open pit mines, roadways, and railways are steeply inclined and composed with rocks that do not contain soils. However, these rock slopes suffer both weathering and fragmentation. In the case of steep slopes, falling rock and collapse of a slope may often occur due to surface erosion. Cast-in place concrete and rubble work are the most widely used earth structure-based pressure supports that act as restraints against the collapse of the rock slope. In order to overcome the shortcomings of conventional retaining walls, a segmental grid retaining wall is being used with connects precasted segments to construct the wall. In this study, laboratory model test was conducted to estimate deformation behavior of segmental grid retaining wall with configuration of rear strecher, height and inclination of the wall. In order to examine the behavior characteristics of a segmental grid retaining wall, this research analyzes the aspects of spacial displacement through relative displacement according to change in the inclination of the wall. Also, the walls behavior according to the formation and status of the rear stretcher which serves the role of transferring the load from the header and the stretcher which make up the wall, the displacement of backfill materials in the wall, and the location of the maximum load were surveyed and the characteristics of displacement in the segmental grid retaining wall were observed. The test results of the segmental grid retaining wall showed that there was a sudden increase in failure load according to the decrease in the wall's height and the size of the in was greatly decreased. Furthermore, it revealed that with identical inclination and height, the structure of the rear stitcher did not greatly affect the starting point or size of maximum horizontal displacement, but rather had a stronger effect on the inclination of the wall.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.4
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• pp.369-376
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• 2003

In this paper, a nonlinear structural analysis for the composite structure composed of the spent nuclear fuel disposal canister and the 50㎝ thick bentonite buffer is carried out to predict the collapse of the canister while the horizontal symmetric sudden rock movement of 10㎝ is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Elastoplastic material model is adopted. Drucket-Prager yield criterion is used for the material yield prediction of the bentonite buffer and von-Mises yield criterion is used for the material yield prediction of the canister(cast iron, copper). Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffet, the canister structure still endures elastic small strains and stresses below the yield strength. Hence, the 50㎝ thick bentonite buffet can protect the canister safely against the 10㎝ sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the canister structure due to the shear deformation of the bentonite buffer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.229-239
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• 2013

Elastic modulus in rockmass is an important factor to represent the characteristic of rock deformation and is frequently used to estimate the displacement induced due to tunnel excavation or other activities in rockmass. Nevertheless, the study to estimate the elastic modulus, which considers the rock type and joint characteristics (joint shear strength and joint inclination angle), has been done in less frequency. Accordingly, this study is aimed at estimating of elastic modulus in jointed rockmass. For this purpose, numerical parametric studies have been carried out with a consideration of rock and joint conditions. Tunnel displacement results have been used to estimate the elastic modulus of jointed rockmass using the elastic theory of circular tunnel. From this study, the results would be expected to have a great practical use for estimating the displacement induced due to tunnel excavation or other activities in jointed rockmass.

• Tunnel and Underground Space
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• v.21 no.3
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• pp.205-215
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• 2011

In this study, we analyzed physical properties of granites and their correlation with rock mass classification methods. The granite samples were obtained from field survey, in-situ borehole tests and laboratory tests for a design phase of various roads, railways and other civil engineering works in Korea. Among the measured physical properties, the results of unit weight, compressive strength, tensile strength, seismic velocity, cohesion, friction angle, elastic modulus and deformation modulus were introduced. We also correlated these properties with the compressive strength. The results of different rock classification method of RQD, RMR, and Q-system against the granites in Korea were compared with each other, and the correlation equations were proposed in a more simplified form. We also derived RMR values using the compressive strength as well as the RQD values of in-situ drilled cores, and estimated the deformation modulus of in-situ rock mass in terms of the RMR values.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.2
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• pp.91-102
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• 1990

The representative tests in this study are performed at a selected site which has the soil layers to analyze the safety and economy of the dynamic analysis for the variable soil conditions. Crosshole test and downhole test of small strain level tests and triaxial test of large strain level test are performed in the soil layers, and in the rock layers, crosshole test and downhole in-situ tests and laboratory sonic test are performed to measure the dynamic shear modulus, damping ratio, and Poisson$\acute{s}$ ratio of the soil and the rock. The correlations between the dynamic soil properties from the tests and the basic soil properties are determined through the regression analysis. The representative design value of the soil is determined by probability analysis of the test results. It is determined from the nonlinear stress-strain model in soils, and the value at small strain level is computed in rocks according to the distribution of the type of soils and the affecting variables. The constitutive value is systematized to be utilized in the analysis of the test results, and computation of the input soil data.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2001.03a
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• pp.118-131
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• 2001

우리 나라의 양수발전소는 지금까지 단일공동을 굴착하였다. 그러나 양양 양수발전소는 두 개의 대공동 즉, 발전소와 주 변전소로 구성된다. 이 경우 공동 구조물의 안정성, 특히 두 공동사이에 형성되는 암주를 영구적으로 안전하게 유지 할 수 있도록 보장되어야 한다. 본 연구에서는 개별요소법을 이용하여 두 공동과 암주의 구조적 안정성을 평가하였으며, 구성모델로 Barton-Bandis의 절리모델을 이용하였다. 현지 암반의 초기응력, 자연절리면의 거칠기계수 불연속면의 공간적 분포 특성과 같은 중요한 요인들은 현지 조사를 통하여 구하였다. 이외에 두 가지 경우 즉, 무보강과 보강의 경우 지보시스템의 최적화를 분석하였으며, 또한 보강효과를 검토하였다. 연구결과 보강의 경우 수평변위와 절리의 전단변위가 감소되었으며 암주내 이완영역 역시 감소됨을 확인하였다. 두 공동사이에 있는 약 36m 두께의 암주에 적절한 보강조치를 취하여 안정성을 확보할 수 있었다.

• The Journal of Engineering Geology
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• v.13 no.4
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• pp.491-496
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• 2003

본 기술은 암반사면 보강공법에서 철근보강재인 네일(Nail)에 원추형콘(철근 규격에 따라 기울기 $19~23^{\circ}$, 높이 40~45mm, 아랫변 65~70mm)을 일정한 간격으로 다수 장착하여 그라우트재와 원 지반까지 방사입체형으로 힘을 미치게 하는 암반사면 보강공법이다. 본 신기술 공법은 네일링 공사 시 원추형 콘을 장착, 삽입함으로서 부착력과 인발력을 증가시켜 비탈면 보강공사 시에 안전성을 높인 공법이다. 따라서 네일링공법을 사면붕괴 방지공사에 적극 활용할 수 있으므로 네일링 공법의 사용을 활성화 하며, 지진이나 지반변형 등 외력에 의한 사면붕괴를 사전에 방지할 수 있어 사면재해를 미연에 방지하는 효과가 있다. 또한 현재가지 네일링공법은 인발톤수가 적고 네일에 대한 신빙성 결여로 아주 적은 인발톤수를 필요로 하는 현장이외에는 사용을 기피하는 일이 많았다. 그러나 본 원추형 콘네일 공법은 어스앙카, 록앵커, 보강토공법, 지지말뚝공법, 옹벽 등에 대한 대체공법으로 이용할 수 있는 여건이 충족됨으로 사면보강재로서의 사용 확산이 기대된다.

• Journal of the Korean Geotechnical Society
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• v.35 no.1
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• pp.5-15
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• 2019

In this study, the in situ deformation moduli, which were measured by borehole loading tests at basaltic rock masses located in the northeastern onshore and offshore and the northwestern onshore of Jeju Island, were examined in relation to RQD and RMR. The measured deformation moduli were also compared with the estimated deformation moduli from conventional empirical formulas using RQD and RMR. In addition, the measured deformation moduli were analyzed with respect to both the velocity ratio ($V_P/V_S$) and dynamic Poisson's ratio, which were obtained from the elastic wave velocities measured by velocity logging tests. As results, with only RQD, it was inappropriate to evaluate the quality of the Jeju island basaltic rock masses, which are characterized by vesicular structures, to select a measurement method of in situ deformation moduli, and to estimate the deformation moduli. On the other hand, it was desirable to evaluate the quality of the Jeju Island basaltic rock masses, and to estimate the deformation moduli by using RMR. The conventional empirical formulas using RMR overestimated the deformation moduli of the Jeju Island basaltic rock masses. There was qualitative consistency in the relation between velocity ratio and deformation moduli. To estimate appropriately the deformation moduli of the Jeju Island basaltic rock masses, empirical formulas were proposed as the function of RMR and velocity ratio, respectively.