• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.700-707
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• 2008

As plan connecting island to island or island to land is needed, a lot of long-span bridge is being designed lately in Southern part of Korea. With development of pile equipment, overhanging large-scaled concrete pile are adopted to foundation type of main tower or pylon. About the number of 15~30 group piles per tower foundation is designed to resist long-spaning super-structure load, but by restricted condition of site investigation cost, a few boring-hole tests are performed to identify sub-ground layers. Up to now, direct-curved method connecting two or three known boring logs and representative interval method are usually used to evaluate unknown depth and rock properties at locations where piles are constructed. Because this approach is not logical and so rough, much difference occurs between designed length of piles and real length of it. In this paper, using a lot of various prediction method(reciprocal distance method, inverse square distance method and kriging method etc.), we suggest optimum length of group piles.

• The Korean Journal of Zoology
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• v.5 no.2
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• pp.9-12
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• 1962

The present observations on the perforation bored into young bivalve Tapes philippinarum (less than 2 mm in shell length) by boring snails were conducted at Sunjae Island in 1960 and Inchon Harbor inn 1962. 1. Young bivalves of the species which were left with bored in them were found both in Inchon Harbor and Sunjae Island. 2. The location of the holes in the valves of the young bivalve varied widely, while the holes of the adult bivalve were located at relatively definite position in the valves. 3. The author realized that the holes are bored by a species of snails that have radulas, for the inner diameters of the holes were much smaller than the router diameters. 4. The size of the holes in the valves of young bivalve was much smaller than those holes bored in adult valves. The minimum size of the holes was only 7.5microns in diameter. 5. The author considered that the boring snail is Natica severa that is found abundantly in Inchon Harbor and Sunjae Island and that this snail is the only species found in the particular areas and performs the above mentioned behavior. However, the author could not confirm experimentally the snail drilling young bivalve of Tapes philippinarum .

• The Korean Journal of Quaternary Research
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• v.20 no.1 s.26
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• pp.1-8
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• 2006

Many boring investigations were achieved in Youngjong-North tidal flat to construct the Incheon International Airport Expressway. Vertical sedimentary profile of this tidal flat has been studied by analyzing these boring data. The deposits of Youngjong-North tidal flat are about 30 meters thick, and the sedimentary layers consist of basal gravel, lower mud, middle silt, middle mud, and upper silt layers in ascending order. Semi-consolidated and oxidized belt with yellowish brown color, which appears above or within middle mud layer, exists in $-3{\sim}-5$ meters altitude. There are some stratigraphical problems to admit the top surface of this oxidized belt as the unconformity surface between Holocene and Pre-Holocene tidal flat deposit.

• Geomechanics and Engineering
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• v.19 no.1
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• pp.93-104
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• 2019

Anomalies and/or fractured grounds not detected by the surface geophysical and geological survey performed during design stage may cause significant problems during tunnel excavation. Many studies on prediction methods of the ground condition ahead of the tunnel face have been conducted and applied in tunneling construction sites, such as tunnel seismic profiling and probe drilling. However, most such applications have focused on the drill and blast tunneling method. Few studies have been conducted for mechanized tunneling because of the limitation in the available space to perform prediction tests. This study aims to predict the ground condition ahead of the tunnel face in TBM tunneling by using an electrical resistivity tomography survey. It compared the characteristics of each electrode array and performed an investigation on in-situ tunnel boring machine TBM construction site environments. Numerical simulations for each electrode array were performed, to determine the proper electrode array to predict anomalies ahead of the tunnel face. The results showed that the modified dipole-dipole array is, compared to other arrays, the best for predicting the location and condition of an anomaly. As the borehole becomes longer, the measured data increase accordingly. Therefore, longer boreholes allow a more accurate prediction of the location and status of anomalies and complex grounds.

• Geomechanics and Engineering
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• v.30 no.1
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• pp.75-91
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• 2022

This paper aims to show how to use several Machine Learning (ML) methods to estimate the TBM penetration rate systematically (TBM-PR). To this end, 1125 datasets including uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), punch slope index (PSI), distance between the planes of weakness (DPW), orientation of discontinuities (alpha angle-α), rock fracture class (RFC), and actual/measured TBM-PRs were established. To evaluate the ML methods' ability to perform, the 5-fold cross-validation was taken into consideration. Eventually, comparing the ML outcomes and the TBM monitoring data indicated that the ML methods have a very good potential ability in the prediction of TBM-PR. However, the long short-term memory model with a correlation coefficient of 0.9932 and a route mean square error of 2.68E-6 outperformed the remaining six ML algorithms. The backward selection method showed that PSI and RFC were more and less significant parameters on the TBM-PR compared to the others.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.301-310
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• 2022

Accurate prediction of mixed ground conditions ahead of a tunnel face is of vital importance for safe excavation using tunnel boring machines (TBMs). Previous studies have primarily focused on electrical resistivity surveys from the ground surface for geotechnical investigation. In this study, an FE (finite element) numerical model was developed to simulate electrical resistivity surveys for the prediction of risky mixed ground conditions in front of a tunnel face. The proposed FE model is validated by comparing with the apparent electrical resistivity values obtained from the analytical solution corresponding to a vertical fault on the ground surface (i.e., a simplified model). A series of parametric studies was performed with the FE model to analyze the effect of geological and sensor geometric conditions on the electrical resistivity survey. The parametric study revealed that the interface slope between two different ground formations affects the electrical resistivity measurements during TBM excavation. In addition, a large difference in electrical resistivity between two different ground formations represented the dramatic effect of the mixed ground conditions on the electrical resistivity values. The parametric studies of the electrode array showed that the proper selection of the electrode spacing and the location of the electrode array on the tunnel face of TBM is very important. Thus, it is concluded that the developed FE numerical model can successfully predict the presence of a mixed ground zone, which enables optimal management of potential risks.

• Geomechanics and Engineering
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• v.29 no.5
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• pp.523-533
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• 2022

Several prediction model of penetration rate (PR) of tunnel boring machines (TBMs) have been focused on applying to design stage. In construction stage, however, the expected PR and its trends are changed during tunneling owing to TBM excavation skills and the gap between the investigated and actual geological conditions. Monitoring the PR during tunneling is crucial to rescheduling the excavation plan in real-time. This study proposes a sequential prediction method applicable in the construction stage. Geological and TBM operating data are collected from Gunpo cable tunnel in Korea, and preprocessed through normalization and augmentation. The results show that the sequential prediction for 1 ring unit prediction distance (UPD) is R²≥0.79; whereas, a one-step prediction is R²≤0.30. In modeling algorithm, a gradient boosted regression tree (GBRT) outperformed a least square-based linear regression in sequential prediction method. For practical use, a simple equation between the R² and UPD is proposed. When UPD increases R² decreases exponentially; In particular, UPD at R²=0.60 is calculated as 28 rings using the equation. Such a time interval will provide enough time for decision-making. Evidently, the UPD can be adjusted depending on other project and the R² value targeted by an operator. Therefore, a calculation process for the equation between the R² and UPD is addressed.

• Educational Technology International
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• v.19 no.1
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• pp.35-60
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• 2018

The purpose of this study was to analyze the types of lesson and its effectiveness with digital textbook. To address those goals, we had observed five classes of the primary school, which designated as a research pilot school for digital textbook. Based on the result of observation, 3 types of lesson with digital textbook were categorized: Teacher-directed lecture (type 1), Blended learning (type 2), and Flipped learning (type 3). Depending on the type of lesson was analyzed the positive and negative effectiveness by means of matrix analysis method. As a result, in Teacher-directed lecture (type 1), there was found out the participation of the lesson in atmosphere of stable and comfortable as positive experience, also digital textbook operating immature and boring as negative experience. In Blended learning (type 2), there was found out the fun by sharing the product and peer feedback, and flow by learning transfer as positive experience, also digital textbook operating immature and understanding the difference between assignments as negative experience. In Flipped learning (type 3), there was shown the positive attitude and ownership in the lesson as positive experience, also distracting and boring in the lesson when learner was excluded in participation as negative experience. Based on the results, we suggested some strategies for improving positive experience and protecting negative experience in the lesson with using digital textbook.

• Korean Journal of Environmental Biology
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• v.40 no.4
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• pp.413-422
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• 2022

Barnea manilensis is a bivalve which bores soft rocks, such as, limestone or mudstone in the low intertidal zone. They make burrows which have narrow entrances and wide interiors and live in these burrows for a lifetime. In this study, the morphology and the microstructure of the valve of rock-boring clam B. manilensis were observed using a stereoscopic microscope and FE-SEM, respectively. The chemical composition of specific part of the valve was assessed by energy dispersive X-ray spectroscopy (EDS) analysis. 3D modeling and structural dynamic analysis were used to simulate the boring behavior of B. manilensis. Microscopy results showed that the valve was asymmetric with plow-like spikes which were located on the anterior surface of the valve and were distributed in a specific direction. The anterior parts of the valve were thicker than the posterior parts. EDS results indicated that the valve mainly consisted of calcium carbonate, while metal elements, such as, Al, Si, Mn, Fe, and Mg were detected on the outer surface of the anterior spikes. It was assumed that the metal elements increased the strength of the valve, thus helping the B. manilensis to bore sediment. The simulation showed that spikes located on the anterior part of the valve received a load at all angles. It was suggested that the anterior part of the shell received the load while drilling rocks. The boring mechanism using the amorphous valve of B. manilensis is expected to be used as basic data to devise an efficient drilling mechanism.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.2 no.1
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• pp.63-70
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• 1969

1. This paper deals with the natural mortality of the early young bivalve, Meretrix lusoria, (less than 13mm in shell length) and the perforations bored in the bivalve by bering snails, Neverita didyma and Natica severa. The investigation was carried out in the Kunsan area and in the laboratory from May to October of 1968. 2. The natural mortality of the field population during this period was $12.1\%$ and among this number $38.1\%$ were drilled by boring snails. 3. The common species of the Naticid gastropods, boring snails-Neverite didyma and Natice severa - are encountered in the habitat of M. lusoria. The perforations drilled by these species were broadly bevelled. 4. The location of the holes on the valves varied widely, while most of holes on the valves were located at a relatively definite umbo position. 5. The inner and outer diameters of the holes varied in proportion to the shell length of the clam; each ranging in shell length from 1 to 3mm, 3 to 6mm, and 6 to 13mm, and the outer diameters were 0.4-0.5mm, 0.7-0.9mm and 0.9-1.2mm. On the other hand, the ratio of the inner and outer diameters differed in proportion to the shell length of the clam. 6. Predation rates of Neverita didyma was much greater at night than during the day at room temperature. An average of 1.7 young clams was drilled and consumed, per snail, per day. This rate was greater than that of the Natica severa. 7 Predation rates varied in proportion to the shell length of the clam and the shell height of the snails.