• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.147-160
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• 2008

This paper presents the results of full-scale loading tests performed on 54 passive anchors and 4 group anchored footings grouted to various lengths at several sites in Korea. The test results, the failure mechanisms as well as uplift capacities of rock anchors depend mostly on rock type and quality, embedded fixed length, properties of the discontinuities, and the strength of rebar. Anchors in poor quality rocks generally fail along the grout/rock interfaces when their depths are very shallow (a fixed length of less than 1 m). However, even in such poor rocks, we can induce a more favorable mode of rock pull-up failure by increasing the fixed length of the anchors. On the other hand, anchors in good quality rocks show rock pull-up failures with high uplift resistance even when they are embedded at a shallow depth. Laboratory test results revealed that a form of progressive failure usually occurs starting near the upper surface of the grout, and then progresses downward. The ultimate tendon-grout bond strength was measured from $18{\sim}25%$ of unconfined compressive strength of grout. One of the important findings from these tests is that the measured strains along the corrosion protection sheath were so small that practically the reduction of bond strength by the presence of sheath would be negligible. Based on test results, the main parameters governing the uplift capacity of the rock anchor system were determined. By evaluation of the ultimate uplift capacity of anchor foundations in a wide range of in situ rock masses, rock classification suitable for a transmission tower foundation was developed. Finally, a very simple and economical design procedure is proposed for rock anchor foundations subjected to uplift tensile loads.

• Journal of the Korean GEO-environmental Society
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• v.16 no.4
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• pp.5-12
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• 2015

Civil engineers have taken the numerous slope monitoring data for an engineering project subjected to hazard potential of slide. However, the topics on how to deal with and draw out proper information from the data related to the slope behavior have not been widely discussed. Recently, several researchers had installed the real-time monitoring system to cope with slope failure; however they are mainly focused on the hardware system installation. Therefore, this study tries to show how the measured data could be grouped and connected each other. The basic idea of analyzing method studied in this paper came from the clustering, which is the part of data mining analysis. Therefore, at the base of classification of time series data, the authors suggest three mathematical data analyzing methods; Average Index of different displacement ($AD_{i,j}$), Difference of average relative displacement ($\overline{RD}_{i,j}$) and Coordinate system of average and relative displacement ($\overline{RD}$, AD). These analyzing methods are based on the statistical method and failure mechanism of slope. Therefore they showed clustering relationships of the similar parts of the slope which makes the same sliding mechanism.

• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.49-62
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• 2006

The republic of korea has put a great emphasis on the role of the road as widening a social infra-structural facility. Thus, vast amount of money has been invested on the road establishment. As a result, there has been fruitful outcomes in establishing the road system of the nation especially for the flat road with ease. However, in order to have more systematic and sustainable road system, we should turn our attention to more painful and high-cost regions such as mountainous districts and those are to be developed effectively. The configuration of the road is an important factor to be considered in making a decision for the road planning. Nevertheless, current road planning criterion has no such clarified and objective judging standard for figuring the configuration of the road out and, as a result, speed planning can be decided incorrectly. our research has acknowledged the necessity of estimating the configuration of the road and aimed to make it organized and sorted according to the height, slope, and the vehicle's speed. The results are as follows. First, our research made use of GIS data and classified the road into 9 different areas according to the height and the slope. Also, road classification being matched to the data of vehicle's speed, it has been shown that those characteristics of different areas have made an influence on vehicle's speed. Secondly, based on the results of the similarity between geographical classification and, vehicle's speed of sorted groups according to the height and the slope, conclusively we have classified as flat, rolling region and mountain. Since our research has made use of vehicle's speed for National Highway, it is not applicable to different functional highways. However, for the highway to be established hereafter, it can be a standard for reflection geographical characteristics.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.108-113
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• 2006

Urban conditions, such as existing underground facilities and ambient noise due to cultural activity, restrict the general application of conventional geophysical techniques. At a tunnelling site in an urban area along an existing railroad, we used the refraction microtremor (REMI) technique (Louie, 2001) as an alternative way to get geotechnical information. The REMI method uses ambient noise recorded by standard refraction equipment and a linear geophone array to derive a shear-wave velocity profile. In the inversion procedure, the Rayleigh wave dispersion curve is picked from a wavefield transformation, and iteratively modelled to get the S-wave velocity structure. The REMI survey was carried out along the line of the planned railway tunnel. At this site vibrations from trains and cars provided strong seismic sources that allowed REMI to be very effective. The objective of the survey was to evaluate the rock mass rating (RMR), using shear-wave velocity information from REMI. First, the relation between uniaxial compressive strength, which is a component of the RMR, and shear-wave velocity from laboratory tests was studied to learn whether shear-wave velocity and RMR are closely related. Then Suspension PS (SPS) logging was performed in selected boreholes along the profile, in order to draw out the quantitative relation between the shear-wave velocity from SPS logging and the RMR determined from inspection of core from the same boreholes. In these tests, shear-wave velocity showed fairly good correlation with RMR. A good relation between shear-wave velocity from REMI and RMR could be obtained, so it is possible to estimate the RMR of the entire profile for use in design of the underground tunnel.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.891-894
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• 2008

This study was performed to investigate how to design, where to construct, why to degrade, what plan to use systematically the underground structures such as underpass, underground passageways. About 50% of the underground structures are located on Seoul, Kyungi-Do. In design of the underground structures such as underpass, underground passageways, the required conditions are defined. And also in construction stage, the conditions of soil, required structure depth, site characteristics, reasonable construction method, are investigated. In the selection of details for underground structure, the items mainly considered, are the wall and column type, the sidewalk type, anchoring-system type, the water-proofing method, entranc shape. The reason and the adequate measures for the degradation of concrete structure are also investigated. The initial cracking properties due to the thermal characteristic are considered. The state of the art report on the new technologies are reviewed. The recent project for the systematically application to the underground structures is reviewed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.2
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• pp.97-111
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• 2013

It is very important to understand the condition of the surround rock for the successful construction of underground space. Representative methods of estimating the rock mass condition are RMR method and Q-system, and they are applied on design, construction, and maintenance. However, many problems with the accuracy of the measurement method and the subjective viewpoint are questioned continuously, so many researchers have been studied for estimating rock condition from various methods. Most of them show only the local relation and a tendency between site investigation data and rock conditions. In this paper, the relationship between RMR method and electrical resistivity is deducted using the analytical equation derived theoretically from electric field analysis on jointed rock mass. And also, probabilistic relationship between RMR method and electrical resistivity is deducted for the increase of accuracy. If a suggested method is applied with the conventional method for estimating the rock condition, it will be helpful to estimate RMR values on the field.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.4
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• pp.31-38
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• 2014

Seismic of the Korean Peninsula is terrible about 1,900 times. Lately, because of a world-occurring seismic, investment of seismic design about ground & structures come to the force as means to protect national life and property. This study evaluated having seismic performance above design criteria among the existing port structures not applied seismic design. Based on the results, classified apprehensive area of liquefaction from seismic performance evaluation and made hazards according to liquefaction risk & structural performance using the analysis of seismic performance and GIS method. After Establishing quantitative & detailed input database through liquefaction evaluation and seismic performance, analysed all seismic data are used directly valuation data on repair reinforcement for apprehensive area of earthquakes.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.4
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• pp.257-268
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• 2016

In the companion papers (I, II), site-specific response analyses were performed at more than 300 domestic sites and a new site classification system and design response spectra (DRS) were proposed using the results of the site-specific response analyses. In this paper, the proposed site classification system and the design response spectra are compared with those in other seismic codes and verified by different methods. Firstly, the design response spectra are compared with the design response spectra in Eurocode 8, KBC 2016 and MOCT 1997 to estimate quantitative differences and general trends. Secondly, site-specific response analyses are carried out using $V_S$-profiles obtained using field seismic tests and the results are compared with the proposed DRS in order to reduce the uncertainty in using the SPT-N value in site-specific response analyses in the companion paper (I). In addition, site coefficients from real earthquake records measured in Korean peninsula are used to compare with the proposed site coefficients. Finally, dynamic centrifuge tests are also performed to simulate the representative Korean site conditions, such as shallow depth to bedrock and short-period amplification characteristics. The overall results showed that the proposed site classification system and design response spectra reasonably represented the site amplification characteristic of shallow bedrock condition in Korea.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.4
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• pp.245-256
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• 2016

In the companion paper (I - Database and Site Response Analyses), site-specific response analyses were performed at more than 300 domestic sites. In this study, a new site classification system and design response spectra are proposed using results of the site-specific response analyses. Depth to bedrock (H) and average shear wave velocity of soil above the bedrock ($V_{S,Soil}$) were adopted as parameters to classify the sites into sub-categories because these two factors mostly affect site amplification, especially for shallow bedrock region. The 20 m of depth to bedrock was selected as the initial parameter for site classification based on the trend of site coefficients obtained from the site-specific response analyses. The sites having less than 20 m of depth to bedrock (H1 sites) are sub-divided into two site classes using 260 m/s of $V_{S,Soil}$ while the sites having greater than 20 m of depth to bedrock (H2 sites) are sub-divided into two site classes at $V_{S,Soil}$ equal to 180 m/s. The integration interval of 0.4 ~ 1.5 sec period range was adopted to calculate the long-period site coefficients ($F_v$) for reflecting the amplification characteristics of Korean geological condition. In addition, the frequency distribution of depth to bedrock reported for Korean sites was also considered in calculating the site coefficients for H2 sites to incorporate sites having greater than 30 m of depth to bedrock. The relationships between the site coefficients and rock shaking intensity were proposed and then subsequently compared with the site coefficients of similar site classes suggested in other codes.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.825-835
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• 2019

When the tunnel is designed, the ground is classified into several grades and the corresponding support system is applied according to the support pattern table. However, a simple pattern application based on rock grade does not take into account the longitudinal stress transitions occurring at rock grade boundaries. In this study, three-dimensional numerical analysis was performed to estimate the stress change in the longitudinal rock grade change of NATM tunnel, and the influence zone of load transfer was investigated using the influence line and trend line. As a result, the downward change of rock grade in the direction of tunnel excavation occurs in the range of 0.35~0.7D from low-strength rock to high-strength rock around the grade change boundary. It is necessary to apply a downward pattern of about 1.0D to the safety direction in consideration of the influence range of 0.35D to 0.7D.