• The Journal of Engineering Geology
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• v.17 no.3
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• pp.339-350
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• 2007

Content, swelling, concentration, drainage of clay are critical factors that could control rock failures as well as discontinuous geological structures like faults and joints. Especially, the proportional components of clay minerals can be one of few direct indicators to a rock failure caused well by rainfall. Criticality of the role of clay mineral contents gets bigger in the slope and tunnel design. This study, using a horizontal boring core of pelitic/psammitic phyllite from the OO tunnel construction site, aims to investigate mineral composition changes related to fault distribution and their mechanical effects to the activity of these discontinuous layers (i.e., clay-filled fault layers), and eventually to define correlation among rock compositions, weathering products and rock instabilities. Field survey and lab tests were carried out for the composition and strength index of fault clay minerals within the core samples and microscopic analysis of fresh and weathered rock samples.

• Journal of the Korean GEO-environmental Society
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• v.9 no.5
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• pp.61-69
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• 2008

In general, it has been usually used the method that assess rock slope stability using stereographic projection method, limit equilibrium analysis, numerical analysis and slope stability evaluation table. Several methods for assessing the stability of rock slopes has been proposed on the basis of site investigation data. These method adopted different evaluation items and weighting factors by researchers, organization and nation. But the researches for each evaluation items were insufficient. So the effectiveness of rock slope stability evaluation items for geometrical configuration (slope height, slope direction and angle, dip and dip direction of major discontinuity, absolute value for the direction difference for slope and major discontinuities) and topographical characteristic (possibility of topographical water concentration, upper natural slope angle, slope configuration) using 315 failure and stable highway rock slope analysis data, AV (abnormal value) analysis and NMAV (normalized maximum abnormal value) analysis were evaluated.

• Tunnel and Underground Space
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• v.33 no.1
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• pp.10-28
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• 2023

Long-term shear behavior of the rock discontinuities should be analyzed and its stability should be evaluated to ensure the long-term stability of a high-level radioactive waste disposal repository. The long-term shear behavior of the discontinuities can be modeled with creep and RSF models. The shear creep test, velocity step test, and slide-hold-slide test can be performed to determine their model parameters or analyze the shear behavior by experiments under various conditions. Testing apparatuses for direct shear, triaxial compression, and biaxial shear were mainly used and improved to reproduce the thermo-hydro-mechanical conditions of local bedrock, and it was confirmed that the shear behavior could vary. In order to design a high-level radioactive waste disposal site in Korea, the long-term behavior of rock discontinuities should be investigated in consideration of rock types, thermo-hydro-mechanical conditions, metamorphism, and restoration of shear resistance.

• Journal of the Korean Geotechnical Society
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• v.27 no.2
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• pp.35-42
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• 2011

The residual stress on drilled shafts is often neglected. Neglect of the existence of locked-in loads in the shaft is the main reason for conclusions of instrumented tests which suggest that shaft resistance is smaller when the shaft is loaded in tension than when it is loaded in compression. A few researchers studied the residual stress and mentioned that the residual stress is influenced by either the physical expansion/contraction of concrete during the curing or site stratigraphy. In this study, field measurements of residual stress on test shafts were conducted and the factors influencing the residual stress were figured out.

• Tunnel and Underground Space
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• v.2 no.2
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• pp.199-211
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• 1992

Blasting vibrations of 3 quarries and 5 construction sites were measured and investigated with two reference data. Square and cubic root scaled distance were similar in fitness to peak particle velocity of individual blasting site, but the former is better fitted in total. It was suggested that the limit scaled distance for domestic surface blasting be 40kg/$\textrm{cm}^2$ for 10mm/s level and 60kg/$\textrm{cm}^2$ for 5mm/s level, which were lower than the OSM's regulation. Prevailing vibration components were in the order of radial, vertical and transverse directions. Prevailing vibration components were in the order of radial, vertical and transverse directons. Site factors K and m were 242 and -1.283 for all studied area, 357 and -1.348 for construction sites, 118 and -1.160 for quarries. Most prevailing frequency was in the range of 10~2Hz. Overlapping effect of delayed blasting vibrations were insignificant. Vibration history of delayed blasting was longer than simultaneous blasting, and it became longer as measuring distance increased. Wave form and predominant frequencies were more complicated for delayed blasting than instantaneous blasting. The influence of blasting scale and measuring distance were not significant to determine peak particle velocity equation.

• Journal of the Korean GEO-environmental Society
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• v.2 no.1
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• pp.5-13
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• 2001

The purpose of this paper is to present the pressuremeter test result and analysis for Yulchon Combined Cycle Power Plant(CCPP) site. The CCPP site is old backfill area with the hillcut materials obtained from the borrow sources near the mountains. The geology of this area consists of 6-layers from the ground level such as hillcut material, dredged clay fill, silty sand, original marine clay, weathered rock, soft rock, etc.. The pressuremeter test has been carried out with three different probe, in size and membrane type for all layers except the clay layers. The cone penetration test has been also carried out to collaborate with the pressuremeter test in the hillcut material layer.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.4
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• pp.59-64
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• 2018

Construction schedule acceleration due to unreasonable construction planning frequently leads to construction accidents. In order to avoid such inevitable acceleration and to ensure safety in construction sites, there is a need for objective standards to determine appropriate construction duration for each construction process earlier in the process. In order to achieve the goal, intensive experts interviews were firstly conducted to identify candidate drivers affecting construction schedule of road tunnel excavation works. Then, a total of 34 field data was collected from on-going sites to analyze. It was found that actual excavation length per one day on site is varied mostly by Rock Mass Rating(RMR) types from various statistical analyses. Therefore an one-way table of excavation length per a day by RMR types were presented in a form of percentile. The results will help industry experts determine the most appropriate construction schedule for the works, which eventually lead to a zero accident site in many ways.

• Tunnel and Underground Space
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• v.19 no.3
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• pp.236-247
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• 2009

Overpopulation has significantly increased the use of underground spaces in urban areas, and led to the developments of shallow-depth underground space. Due to unexpected rock fall, however, it is very necessary to understand and categorize the rock mass behaviors prior to the tunnel excavation, by which unnecessary casualties and economic loss could be prevented. In case of cave-in, special attention should be drawn since it occurs faster and greater in magnitude compared to rock fall and plastic deformation. Types of cave-in behavior are explained and categorized using seven parameters - Uniaxial Compressive Strength (UCS), Rock Quality Designation (RQD), joint surface condition, in-situ stress condition, ground water condition, earthquake & ground vibration, tunnel span. This study eventually introduces a new index called Cave-in Behavior Index (CBI) which explains the behavior of cave-in under given in-situ conditions expressed by the seven parameters. In order to assess the mutual interactions of the seven parameters and to evaluate the weighting factors for all the interactions, survey data of the experts' opinions and Rock Engineering Systems (RES) were used due to lack of field observations. CBI was applied to the tunnel site of Seoul Metro Line No. 9. UDEC analyses on 288 cases were done and occurrences of cave-in in every simulation were examined. Analyses on the results of 288 cases of simulations revealed that the average CBI for the cases when cave-in for different patterns of tunnel support was estimated by a logistic regression analysis.

• Tunnel and Underground Space
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• v.15 no.2 s.55
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• pp.119-128
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• 2005

Although the evaluation of the mechanical properties and behavior of jointed rock masses is very important for the design of tunnel and underground openings, it has always been considered the most difficult problem. One of the difficulties in describing the rock mass behavior is the selection of the appropriate constitutive model. This limitation may be overcome with the progress in discrete element software such as PFC, which does not need the user to prescribe a constitutive model for rock mass. In this paper, a 30\;m\;\times\;30\;m\;\times\;30\;m m jointed rock mass of road tunnel site was analyzed. h discrete fracture network was developed from the joint geometry obtained from core logging and surface survey. Using the discontinuities geometry from the DFN model, PFC simulations were carried out, starting with the intact rock and systematically adding the joints and the stress-strain response was recorded for each case. With the stress-strain response curves, the mechanical properties of jointed rock masses were determined. As expected, the presence of joints had a pronounced effect on mechanical properties of the rock mass. More importantly, getting the mechanical response of the PFC model doesn't require a user specified constitutive model.

• Tunnel and Underground Space
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• v.20 no.6
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• pp.475-490
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• 2010

The analysis of slope stability was performed from seven sites among total eleven sites of waste rock which are divided into two objects (mullock-pile and rock mass) according to the location of dumping-dropping point in L limestone Mine. The analysis of circular failure using Bishop's simplified method and the finite element method for mullock-pile slopes were adopted. For rock mass slopes, identification of failure modes on stereonet projection was determined, thereby limit equilibrium analysis was applied to obtain the safety factor of slopes and the finite element method was used to understand overall behavior of slope. Phi-c reduction method was used to calculate the safety factor of slopes through the finite element method. In mullock-pile slope of zone D and rock slopes of zone F and G, the assurance of slope stability was difficult, and the plans to assure the stability of slopes were proposed on the basis of the analysis of slopes at disposal sites of waste rock. Therefore, the method of piling with waste rock by dozer pushing after dumping for mullock-pile slope of zone D is required, and the method of piling after moving to the place which has no fault zone for rock slope of zone F and G is recommended.