• Tunnel and Underground Space
• /
• v.11 no.2
• /
• pp.167-173
• /
• 2001

The joint model has influence on the results of discontinuum analysis. In this study the results of discontinuum analysis with Barton-Bandis joint model(BB model) and with Mohr-Coulomb joint model(MC model) are compared. The results of continuum analysis under the same condition are compared with the results of discontinuum analysis to investigate the behavior of rockmass around tunnel. The result of continuum analysis and that of discontinuum analysis with BB model show similar distribution of displacement and stress. On the other hand, the discontinuum analysis with MC model shows different displacement distribution and stress distribution. Moreover, the displacement and minor principal stress of the discontinuum analysis with MC model are smaller than those of continuum analysis, although the joints are explicitly considered in the discontinuum analysis. These results are originated from the limitation of MC model in simulating joint deformation behavior, especially the assumption of constant dilation jingle independent of it)int 7hear displacement.

• Tunnel and Underground Space
• /
• v.27 no.2
• /
• pp.77-88
• /
• 2017

The geology of the study area is composed mainly of conglomerate, sandstone, and shale and basalt. It is a rock that has been observed to move relatively recently through various brittle deformation and various stress fields during the recent period. To form a gentle terrain with severe crushing. The slope is located at the intersection of the Taegok Fault in the north-northeast direction and the Bukok Fault in the western north-west direction, and many faults, fault zones and fracture zones of various sizes are developed in the rock bed. In this study, the geological characteristics of the slope are investigated and the countermeasure method is suggested. It is suggested that periodical measurement and analysis should be performed by installing a measuring instrument according to each structure for safety management of the surrounding roads and grounds during construction or reinforcement by the countermeasure method for the slope of the study area.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.8
• /
• pp.15-27
• /
• 2004

Sliding aspects of rock slope, where large-scaled tension cracks are induced during preliminary excavation, have been analyzed. Structure of rock mass is investigated by performing the electrical resistivity survey and the orientations and positions of discontinuities are measured from DOM-drilled core log. Geological evidence far primary failure movement has been detected and clay minerals which possess swelling properties are identified through XRD analysis. Slope stability is examined by considering the orientations of discontinuities and their trace distributions on the cut-face and neighboring natural slope surface. Both orientations and positions of failure-invoking discontinuity planes, traces of which are exposed within the anticipated sliding region, are concerned fur analyzing the preferred sliding directions. Regional sliding vectors are assessed based on the relative positions of potential sliding planes in the boreholes and the general trend of anticipated failure movement of rock slope is also investigated.

• Journal of the Korean Society of Groundwater Environment
• /
• v.5 no.2
• /
• pp.101-109
• /
• 1998

Hydraulic property of fissured aquifers often depends on geologic structure which acts main channel of groundwater flow. We treated theories of linear flow related to vertical geologic structure. Then, we analyzed the result of two pumping tests conducted in Okmyeong-ri area (Kyeongbook province) using fractal model and found hydraulic characteristic of the fissured aquifer in this area. According to the pump test analyses, groundwater flow around the holes (pumping well D9; observation wells C3 and D7) of test 1 is linear. and is controlled by vertical geologic structure with infinite length and infinitesimally small width. On the other hand, around the hole D10 (pumping well) of test 2, groundwater flow is pseudo-radial (n=1.9) or radial (n=2). Thus, the characteristic of fractured aquifer often shows variable groundwater flow spatially and temporally.

• Tunnel and Underground Space
• /
• v.15 no.5 s.58
• /
• pp.378-386
• /
• 2005

Jook-Ryung roadway tunnel was constructed by drill-blast after pilot tunnelling by 2 TBMS. nis report analyzes the data for TBM performance in the total length of 7.3 km for the two pilot tunnels. Net penetration rates were recorded as high as 2.3 m/h and 2.0 m/h for the two different directions while degrees of operation were $31.4\%$ and $33.3\%$, respectively. The cutter lives for No.2 tunnel were evaluated $200\~280\;m^3/c$ and around 400 m/set as high as for Meraker 10 km tunnel in Norway. The relationship between net penetration rate and characteristics of rock mass which were obtained by RMR and TSP measurement, coincides with the prior studies. This kind of evaluation is expected to be used to design TBM tunnelling and to help to perform the TBM operation effectively

• Tunnel and Underground Space
• /
• v.16 no.5 s.64
• /
• pp.413-421
• /
• 2006

In order to explain entirely dynamic fracture process induced by blasting in rock mass, it needs to consider detonation pressure and gas pressure acting on blasthole wall simultaneously. In this study, prior to simulating the coupling between gas flow and rock mass, we analyzed effects of gas pressure-time history, length of cracks and equation of state adopted to calculate the gas pressure on the gas flow within a radial fracture created by single-hole blasting. The effects were investigated on two assumptions: (a) the radial fracture was composed of 5 cracks which were 0.01 m in length and 0.001 m in asperity each and (b) the PETN explosive which diameter was 36 mm was charged in a blasthole of 45 mm diameter. It was concluded that the maximum gas pressure and its travel time were dependent on characteristics of charged explosives and geometrical properties of radial fracture.

• Tunnel and Underground Space
• /
• v.19 no.4
• /
• pp.348-354
• /
• 2009

Slug test is a common characterization method that estimates aquifer hydraulic conductivity rapidly and economically. To characterize the hydraulic property near the borehole YS-4 in the Korea Atomic Energy Research Institute (KAERI) site, slug tests were performed, and oscillatory hydraulic responses were observed. We analyzed the observations with the modified Hvorslev and Bouwer&Rice methods considering the casing inertia, and then the results were compared with those from the general Hvorslev and Bouwer&Rice methods. The estimated hydraulic conductivities from the modified methods are ranged from $4.85{\times}10^{-6}$ to $5.44{\times}10^{-6}$ m/sec, but those from the general ones are ranged from $3.10{\times}10^{-6}$ to $3.63{\times}10^{-5}$ m/s, which shows that the oscillatory responses should be analyzed with consideration of the flowing water inertia effect.

• Journal of the Korean GEO-environmental Society
• /
• v.7 no.2
• /
• pp.25-32
• /
• 2006

The deformation modulus of rock masse is a very important design factor for the computation of stability of tunnels and their support systems. Several empirical formulas to estimate the deformation modulus using simple rock classification methods such as RQD or RMR are widely used because field tests to evaluate the deformation modulus are very expensive and time consuming work. However, these formulas can be depended on experiences from the characteristics of local sites in each country. Therefore, in this study, the applicability of empirical formulas was analyzed by comparing estimated value with the measured value from eight sites in South Korea. The results show that the estimated value based on the empirical formulas partially have tendency to overestimate. Especially, in case of sedimentary rocks, it was too difficult to apply to the empirical formulas because there was no relationship between estimated value and measured value. For these reasons, additional data from many tests and accurate analyses are necessary to evaluate the estimation method for the deformation modulus considering the local characteristics of rock masse.

• Journal of Soil and Groundwater Environment
• /
• v.7 no.1
• /
• pp.3-14
• /
• 2002

We analyzed hydrologic time-series data obtained from a fractured aquifer in Wonju and a porous shallow aquifer in Uiwang area. Auto-correlation, spectral density, and cross-correlation functions were used for the analyses. Water level at a shallow well in Wonju was weakly auto-correlated and it was sensitive to direct infiltration from rainfall through soil zone while that at a well screened in the fractured zone showed a relative stability to an outer stress (rainfall), which was derived from a delayed transmission of recharge stress through a fracture network from a remote area. Characteristics of time-series data in Uiwang area were similar to those in the fractured zone in Wonju. This was caused by a regional recharge from a distant area rather than a direct infiltration. This study demonstrated a usefulness of time series analyses for identification of recharge mechanism.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.5
• /
• pp.65-73
• /
• 2009

Large scale model tests and numerical analyses are performed to investigate the stress distribution of pillar due to surface loading nearby two-arch tunnel which is constructed in the regularly jointed rocks. It is observed that the influence of discontinuities on the stress distribution in the discontinuous rock mass and the underground stresses induced by surface loading are greater than those of linear elastic theory. Especially, lines of equal stresses are developed to the direction of inclination according to the inclined grade. In cases of discontinuities imbedded in parallel with or vertical to the ground, the pressure bulbs are formed symmetrically, however, the inclined ones result in stress distribution in parallel with and vertical to the planes of discontinuities. Results indicated that stress distribution is seriously affected by the angle of discontinuity. When stresses propagating to the pillar need to be estimated, relative location of surface loading, grade of discontinuous plane, and location of two-arch tunnel should be carefully considered.