• Journal of the Korean Society of Safety
• /
• v.15 no.2
• /
• pp.103-110
• /
• 2000

This paper deal with the stability evaluation and suggestion of progressive failure slope in biotite granite area of Andong. Based on geological site investigation and field test, stability analysis of slope was performed in conjunction with limit equilibrium methods and stereographic projection. Additionally, initial design and construction procedure was critically evaluated. Series of the slope stability analysis reveals the detection of local wedge and plane failure under the current slope condition. It is additionally appeared that a certain synthetic behavior of circle and plane failure exists on the right spot where the overall failure's going in progress. In order to construct more stable slope based on the suitability for the real state of the slope circumstances, this study issues a solution to eliminate the primary factors which cause the instability, by means of the grade of weathering and RMR classification of rock mass.

• The Journal of Engineering Geology
• /
• v.12 no.2
• /
• pp.167-178
• /
• 2002

Properties of discontinuity for Seoul Granite in northeastern part of Seoul City were analyzed by dividing structural domains into Surak and Bulam Mtn. areas. Important parameters measured among several engineering properties of a rock during tunnel excavation and road construction are as follows: 1) Orientation of joint, 2) joint spacing, 3) joint density, and 4) uniaxial compressive strength. Orientation, spacing, and density of joints can be directly measured during field investigation using scanline survey, circle-inventory method, and window survey. Uniaxial compressive strength of the rock was calculated by a simple correlation equation although it is originally necessary to prepare core samples in measuring it. Major orientations of joints measured from both areas are 3 sets of joints with different orientations. In other words, they are 2 sets of orthogonal joint and 1 set of sheet joint that is dipping at low angle, and have very similar orientations in both areas. Joint densities in both areas range from 0.039 and 0.066/cm, and average joint length are between 1.30 and 4.52m. Average joint spacing also has values from 10.3cm up to 59.6cm, and shows significant difference along specific orientation of scanlines measured. Values of uniaxial compressive strength calculated on the basis of Schmidt hammer rebound values range from 217 to 335 MPa, which indicates very strong rock type by classification of wall strength.

• The Journal of Engineering Geology
• /
• v.28 no.4
• /
• pp.673-686
• /
• 2018

The physical properties of rocks constituting the rock mass were analyzed by using various methods such as 7 kinds of physical properties of about 2,400 data. The correlation equation was derived from the correlation equation with the dependent variables by screening independent variables through the significance level using multiple regression analysis. In order to verify the reliability of this equation, verification was performed through comparison with actual data using artificial neural network learning. The analysis results by petrogenesis and strength confirmed that the elastic wave velocity (compressional wave) and elastic modulus as the main influence factors for the independent variables affecting the dependent variables. This proves that most of the correlation equations using the above items are found in existing studies. And through this study, it is confirmed whether the rock classification is based on the above items in various standards. In addition, the analysis results of representative rocks showed a high correlation as the equation for estimating unconfined compressive strength and elastic modulus exceeds the coefficient of determination 0.8.

• Tunnel and Underground Space
• /
• v.31 no.4
• /
• pp.289-308
• /
• 2021

This study conducts coupled thermo-hydro-mechanical numerical modeling to investigate the maximum temperature and conditions for securing mechanical stability of the high-level radioactive waste repository when temperature criteria of bentonite buffer are 100℃ and 125℃, respectively. In case of temperature criterion of buffer as 100℃, the maximum temperatures at the interface between canister and buffer are calculated to be 99.4℃ and 99.8℃, respectively for a case with disposal tunnel spacing of 40 m and deposition hole spacing of 5.5 m and for the other case with disposal tunnel spacing of 30 m and deposition hole spacing of 6.5 m. In case of temperature criterion of buffer as 125℃, spacings of disposal tunnel and deposition hole could be decreased to 30 m and 4.5 m, respectively, which reduces the disposal area up to 55% compared to the disposal area of KRS⁺. According to analysis of mechanical stability for various disposal spacings, RMR of rock mass for KRS⁺ should be larger than 72.4 which belongs to good rock in RMR classification to prevent failure of rock mass. As disposal spacing is decreased, required RMR of rock mass is increased. In order to prevent failure of rock mass for a case with disposal tunnel spacing of 30 m and deposition hole spacing of 4.5 m, RMR larger than 87.3 is needed. However, mechanical stability of the repository is secured for all cases with RMR over 75 considering the enhancement of rock strength due to confining stress induced by swelling of the bentonite buffer and backfill.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.21 no.2
• /
• pp.95-103
• /
• 2017

In order to modeling seismic isolation system such as lead-rubber bearing (LRB), bilinear model is widely used by many researchers. In general, an actual force-displacement relationship for LRB has a smooth hysteretic shape. So, Bouc-Wen model with smooth hysteretic shape represents more accurately actual hysteretic shape than bilinear model. In this study, seismic responses for seismically isolated nuclear power plant (NPP) with LRB modelled by Bouc-Wen and bilinear models are compared with those of NPP without seismic isolation system. To evaluate effect of earthquake characteristics for seismic responses of NPP isolated by LRB, 5 different site class earthquakes distinguished by Geomatrix 3rd Letter Site Classification and artificially generated earthquakes corresponding to standard design spectrum by Reg. Guide 1.60 are used as input earthquakes. From the seismic response results of seismically isolated NPP, it can be observed that maximum displacements of seismic isolation modelled by Bouc-Wen model are larger than those by bilinear model. Seismic responses of NPP with LRB is significantly reduced than those without LRB. This reduction effect for seismic responses of NPP subjected to Site A (rock) earthquakes is larger than that to Site E (soft soil) earthquakes.

• Geomechanics and Engineering
• /
• v.8 no.5
• /
• pp.675-685
• /
• 2015

Weathering is the breaking/cutting down process of rocks due to physical and chemical processes in natural as well as artificial environment including $CO_2$ injection for storage in the sediment, or natural resource recovery process. This study suggests an alternative method to estimate the degree of weathering for granites. A series of laboratory and field experiments are performed to measure electrical resistivities on various rock samples experienced different degrees of weathering and their residual soils under different saturation conditions. It is found that the normalized electrical resistivity increases with a decrease in water absorption and the saturation. Simple boundaries are suggested to identify the weathering degree of granites, based on limited data. Field test results for three sites confirm that the suggested method could be estimated well the degree of weathering of granites compared with the other methods suggested previously. Although further research is required, this study suggests that an electrical resistivity could be an effective approach to estimate the degree of weathering of granites compared with the other methods suggested previously.

• The Journal of Engineering Geology
• /
• v.24 no.3
• /
• pp.383-396
• /
• 2014

The condition, characteristics, and stability of slopes, as well as the consequences of slope failure, need to be understood for the proper stabilization of slopes and preclusion of potential disasters arising from slope failure. Here, a slope code system (SCS) that succinctly and accurately reflects the various conditions of a slope is proposed. The SCS represents the condition, characteristics, and geotechnical stability of slopes, as well as the consequences of slope failure, and the method is quickly and easily applied to a given slope. The SCS comprises five elements: 1) the slope material; 2) the genetic origin (rock type) and geological structure of the slope; 3) the geotechnical stability of the slope; 4) the probability of failure and remedial works made upon the slope; and 5) the consequences of failure. A letter code is selected from each element, and the result of the evaluation and classification of the slope is given as a five-letter code. Because the condition, characteristics, and geotechnical stability of a slope, as well as the consequences of slope failure, are provided by the SCS, this system will provide an effective mechanism for the maintenance and management of slopes, and will also allow more informed decision-making for determining which slopes should be prioritized for remedial measures.

• The Journal of Engineering Geology
• /
• v.19 no.1
• /
• pp.43-50
• /
• 2009

A 3-D numerical analysis was carried out to observe potential effects of orientation of inherent weak zones to tunnel behaviors and stress distributions during tunnel excavation. Weak zones used for the analysis were placed at the upper 1D part from crown, on the crown and on the center of face, using orientations derived from the 6th RMR parameter for assessment of joint orientation effect on tunnel. Mechanical properties of rock mass were derived through a in-situ displacement measurement-based back analysis. Finally, a classification chart for crown settlement with five ranks based on orientation and location of weak zones is suggested.

• Tunnel and Underground Space
• /
• v.11 no.2
• /
• pp.174-181
• /
• 2001

The cavities created by underground mining, if remained unfilled, can cause ground settlement and surface subsidence as a result of relaxation and breakdown of the carven roof. Construction of structures above the underground mine cavity will have serious problems concerning both structural stability and safely even if the cavity is back-filled. This study was conducted to confirm the location and condition of the cavern as well as the state of the back-fill in A mine area using core logging and borehole camera. The bearing capacity and other mechanical properties of the ground were also measured by the standard penetration test(SPT). Obtained data were used to assess the stability of the ground and the structures to be built by numerical analysis using FLAC. The site investigation results showed that the mine cavities were filled with materials such as boulder and silty sand(SM by unified classification). Result of the numerical analyses indicated that constructing building structures on the over-lying ground above the filled cavities is secure against the potential problems such as surface subsidence and ground settlement.

• Journal of the Korean Geotechnical Society
• /
• v.34 no.9
• /
• pp.43-49
• /
• 2018

Seismic hazard assessments are performed on a variety of infrastructure projects. One component of a seismic hazard assessment is the attenuation relationship. Several attenuation relationships have been developed over the decades to predict peak ground acceleration under a variety of site conditions. For example, many attenuation relationships were designed to estimate peak ground acceleration, as well as other intensity measures, under a variety of soil conditions, mostly using the average shear wave velocity for the upper 30 m of earth material as a classification scheme. However, certain types of infrastructure, such as tunnels and nuclear power plants, are typically founded on and in bedrock. Using data from Japan, we developed a simple correlation to estimate peak ground acceleration for rock sites and compare the results from another popular attenuation relationship. Results indicate the popular attenuation relationship to be less than the proposed model for distances less than 200 km.