• Journal of the Korean Geotechnical Society
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• v.37 no.1
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• pp.29-41
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• 2021

Although underground works are essential to use underground spaces in urban areas efficiently, various damages caused by constructions have often occurred, making them major social problems. Since 2018, it is stipulated in the Special Act on Underground Safety Management that appropriate construction methods must be used in the design stage to prevent various damage cases. This Special Act includes establishing an area subject to underground safety impact assessment, analysis of ground and geological status, review of effects caused by changes in groundwater, review of ground safety, and establishment of measures to secure underground safety. This study area consists of various strata in order of landfill, sedimentary silt, sedimentary sand, sedimentary gravel, weathering zone, and foundation rock. Also, the slurry wall, a highly rigid underground continuous wall, was chosen as a construction method to consider high water table distribution and minimize the influence of the surroundings in this area. However, ground subsidence occurred on the road nearby in December 2019 due to the inflow of loosening soil to the construction area. Thus, several types of site investigations were conducted to suggest an appropriate analysis method and to find out loosed ground behavior and its area for the subsided site. As a result, new design soil properties were re-calculated, and the reinforcement measures were proposed through analytical verification.

• Geomechanics and Engineering
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• v.35 no.2
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• pp.121-133
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• 2023

The demand for cement and limestone crushed materials has increased many folds due to the tremendous increase in construction activities in Pakistan during the past few decades. The number of cement production industries has increased correspondingly, and so the rock-blasting operations at the limestone quarry sites. However, the safety procedures warranted at these sites for the blast-induced ground vibrations (BIGV) have not been adequately developed and/or implemented. Proper prediction and monitoring of BIGV are necessary to ensure the safety of structures in the vicinity of these quarry sites. In this paper, an attempt has been made to predict BIGV using artificial neural network (ANN) at three selected limestone quarries of Pakistan. The ANN has been developed in Python using Keras with sequential model and dense layers. The hyper parameters and neurons in each of the activation layers has been optimized using randomized and grid search method. The input parameters for the model include distance, a maximum charge per delay (MCPD), depth of hole, burden, spacing, and number of blast holes, whereas, peak particle velocity (PPV) is taken as the only output parameter. A total of 110 blast vibrations datasets were recorded from three different limestone quarries. The dataset has been divided into 85% for neural network training, and 15% for testing of the network. A five-layer ANN is trained with Rectified Linear Unit (ReLU) activation function, Adam optimization algorithm with a learning rate of 0.001, and batch size of 32 with the topology of 6-32-32-256-1. The blast datasets were utilized to compare the performance of ANN, multivariate regression analysis (MVRA), and empirical predictors. The performance was evaluated using the coefficient of determination (R²), mean absolute error (MAE), mean squared error (MSE), mean absolute percentage error (MAPE), and root mean squared error (RMSE)for predicted and measured PPV. To determine the relative influence of each parameter on the PPV, sensitivity analyses were performed for all input parameters. The analyses reveal that ANN performs superior than MVRA and other empirical predictors, andthat83% PPV is affected by distance and MCPD while hole depth, number of blast holes, burden and spacing contribute for the remaining 17%. This research provides valuable insights into improving safety measures and ensuring the structural integrity of buildings near limestone quarry sites.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.2
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• pp.191-201
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• 2024

In this study, three-dimensional finite element analysis was used to analyze the behavior of existing and reinforcing piles according to the pile support conditions for vertical extension remodeling. Cap support conditions (group pile, piled raft foundation) and pile tip conditions (rock, soil embedment) were considered as factors influencing existing and reinforcing piles behavior. For the quantitative analysis of existing and reinforcing piles, the displacement, load distribution ratio, and axial force by depth according to the analysis stage were analyzed. As a result of the analysis, it was confirmed that the largest settlement occurred in the reinforcing pile due to the pre-loading method. In particular, a large amount of settlement occurred in group piles regardless of the embedment conditions. In the piled raft foundation, it was confirmed that the displacement and load distribution ratio of existing piles and reinforcing piles were reduced due to the influence of the raft. The axial force by depth showed a difference between group pile and piled raft foundation, which appears to be a major factor affecting displacement and load distribution ratio. Based on the numerical analysis results, it was confirmed that cap support conditions and pile tip embedment conditions should be considered in the design of pile foundations for vertical extension remodeling.

• Economic and Environmental Geology
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• v.44 no.1
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• pp.37-48
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• 2011

Some industrial minerals used in domestic industries such as monazite, apatite, bauxite, and ilmenite belong to NORM (Naturally Occurring Radioactive Materials) because they show a high radioactivity. Products, semi-products, wastes, and by-products which show higher radioactivity than NORM belong to TENORM (Technologically Enhanced Naturally Occurring Radioactive Materials). Apatite used for manufacturing phosphate fertilizer in Namhae Chemical company belongs to NORM, and its by-product, phospo-gypsum, belongs to TENORM. A geological investigation is needed for the future environmental impact assessment of the Namhae Chemical company's site. According to survey results of the Namhae Chemical company's site, soil mineral composition indicated the mixture of minerals derived from the country rock (quartz, feldspar, mica, $l4{\AA}$ mineral, kaolin and amphibole) and minerals from the gypsum open-air storage yard (gypsum and apatite). Soil samples showed average content of U 4.6 ppm and Th 10 ppm, which are similar to average crustal abundances. They also show average contents of $^{40}K$ 191-1,166 Bq/kg, $^{226}Ra$ 15.6-710 Bq/kg, and $^{232}Th$ 17.4-72.7 Bq/kg, which indicate moderate levels of radio nuclide. But $^{226}Ra$ anomaly in the gypsum open storage yard is clearly confirmed and $^{232}Th$ anomaly is also confirmed in the east road side of the factory and nearby mountain areas. Soil external hazard indices ranged 0.24-2.01 with the average 0.54. Although most external hazard indices were lower than 1, which means radiation hazard index to be negligible, 5 samples out of total 40 samples showed higher values than 1, and further detailed investigation is needed.

• Economic and Environmental Geology
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• v.44 no.5
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• pp.399-412
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• 2011

A DEM (digital elevation model) is produced using a digital topographic map and is now a commonly used tool in geologic surveys. This study aimed to clarify the relationship between knickpoints and faults in the Namdae stream by analyzing a DEM of the area. The Namdae drainage basin was divided into three subbasins (S1, S2 and S3) and their knickpoints developed for the middle to mid-upper regions were extracted from the DEM. The relative steepness Ks and concavity depending on the incision rate was higher in S1 than in S2 and S3 regions. We assumed that the incision rate caused by active erosion resulted from several faults crossing the basins rather than differences in rock types. There are 77 knickpoints in the Namdae drainage area, including the low-ranking branch, and 24 of thses are on the main river system (S1, S2, S3). Of these 77 knickpoints, 27 (38%) are matched by faults, and from the three basins, 13 (54%) correspond with faults, indicating that the knickpoints are connected closely with the faults. For example the average Ks (relative steepness), was 38.8, but in the overlapping area of the Samdang and Doocheon faults the Ks value was 42.99~43.39. We suggest that the faults resulted in geomorphic deformation such as the high-Ksn knickpoints. There was little evdence of relationship between the knickpoints and rock boundaries, with 54% of the knickpoints distributed on the S1, S2, and S3 subbasins. We concluded that the drainage basin knickpoints are the result of fault movement and are a type of geomorphologic deformation that could be useful for surveying Quaternary faults or fault extension.

• Economic and Environmental Geology
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• v.50 no.6
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• pp.487-495
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• 2017

A granite rock body, called 'Bukbawi', located on a mountaineering trail at Mt. Palgong Provincial Park is popular among the public because it resembles a percussion instrument. If someone hits the specific surface area of this rock body, people can hear drum-like sound. Such phenomenon may be geologically associated with exfoliation process of the granite body or miarolitic cavity developed after gasses escaped during formation of granite. To understand better the inner structure causing drum-like sound, we carried out a non-destructive ground-penetrating radar survey. In this study, as our primary target is very close to the surface, we utilized 1 GHz antennas to produce high-resolution near-surface images. In order to construct 3-D internal images, the measurements were conducted along a pre-defined grid. The processed radargrams revealed that the locations associated with 'drum' sound coincide with strong reflections. In addition, both reflection patterns of fracture and cavity were observed. To further quantify the observed reflections, we simulated GPR scans from a synthetic fracture in a granite body, filled with different materials. The simulated results suggest that both exfoliation process and miarolitic cavity may have contributed to the 'drum' phenomena. Furthermore, the radargrams showed a well-developed cavity signature where two major reflection planes were crossed. Thus, our study is an example of non-destructive geophysical studies that can promote Earth Science in the broader community by examining geological structures attracting the public.

• Korean Journal of Ecology and Environment
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• v.48 no.1
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• pp.61-67
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• 2015

This study, which was conducted from Apr. 2013 to Jan. 2014, was carried out as part of a project of making a more detailed ecological zoning map with 1/5,000 scale. The necessity of electronic vegetation map with large scale has arisen in order to make the best use of basic research findings on resource monitoring of National Parks and to enhance efficiency in National Park management. In order to improve accuracy and speed of vegetation research process, the data base for vegetation research was categorized into five groups, namely broad-leaved forest, coniferous forest, mixed forest, rock vegetation and miscellaneous one. And then a vegetation map for vegetation research was created for the research on the site. What is in the database for vegetation research and the vegetation map reflecting findings from vegetation research showed similar distribution rate for broad-leaved forest with 71.965% and 71.184%, respectively. The distribution rate of coniferous forest (16.010%, 15.747%), mixed forest (10.619%, 12.085%), and rock vegetation (0.015%, 0.002%) did not have much difference. In a detailed vegetation map reflecting vegetation research findings, the broad-leaved mountain forest was the most widely distributed with 60.096% based on the physiognomy classification. It was followed by mountain coniferous forest (16.332%), mountain valley forest (15.887%), and plantation forest (3.558%) As for vegetation conservation classification evaluated in the national park, grade I and grade II areas took up 200.44 km2, 61.80% and 108.80 km2, 33.55% respectively. The combined area of these two amounts to 95.35%, making this area the first grade area in ecological nature status. This means that this area is highly worth preserving its vegetation. The high rate of grade I area such as climax forests, unique vegetation, and subalpine vegetation seems to be attributable to diverse innate characteristics of Odaesan National Park, high altitude, low level of artificial disturbance, the subalpine zone formed on the ridge of the mountain top, and their vegetation formation, which reflects climatic and geological characteristics, despite continuous disturbance by mountain climbing.

• The Journal of the Petrological Society of Korea
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• v.24 no.1
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• pp.25-54
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• 2015

Syenite is not a common rock, unlike granitic rocks formed the major component of the continental crust. The aim of this study is to decipher the occurrences and detailed descriptive characteristics of the syenite distributed in Sancheong area, and to investigate the petrogenesis of the syenitic magma based on geochemical study. The dominant minerals in syenite are alkali feldspar (usually orthoclase and rarely microcline), plagioclase, amphibole, biotite, and quartz. Syenites are found in a wide variety of colors. The anhedral hornblende and biotite filling the boundary of feldspar and quartz indicate that the hydrous minerals were crystallized lately, and that water was insufficient at the beginning of crystallization in magma. According to the analysis of mineral composition, amphibole in syenite is mostly ferro-edenite, and the pressure is calculated as 3.3~4.9 kb with 11.9~17.3 km of emplacement depth. Biotite and pyroxene are plotted in the region of annite and hedenbergite, respectively. Based on petrochemical studies of major elements, syenite belongs to alkaline series, metaluminous, and I-type. On the other hand, the variation patterns of trace and rare earth elements of syenite differ from the patterns of diorite and granite. In the geochemical characteristics, syenite is different from gabbro-diorite spatially adjacent to syenite, as well as granite. These results suggest that each rock has been generated from the different sources of magma. Additionally, based on the experimental data, the syenitic magma can be formed (1) by the partial melting at a high pressure and dry system, (2) when the initial crystallization minerals to be residue with migration of the residual melts separated from the ascending cotectic magma (3) when fluorine compositions to be plentiful in the protolith and/or at depth of the magma. Based on the petrographic characteristics of the syenite, Sancheong syenitic magma may have been formed by partial melting in a dry system.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.5
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• pp.431-449
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• 2022

As many tunnels generally have been constructed, various experiences and techniques have been accumulated for tunnel design as well as tunnel construction. Hence, there are not a few cases that, for some usual tunnel design works, it is sufficient to perform the design by only modifying or supplementing previous similar design cases unless a tunnel has a unique structure or in geological conditions. In particular, for a tunnel blast design, it is reasonable to refer to previous similar design cases because the blast design in the stage of design is a preliminary design, considering that it is general to perform additional blast design through test blasts prior to the start of tunnel excavation. Meanwhile, entering the industry 4.0 era, artificial intelligence (AI) of which availability is surging across whole industry sector is broadly utilized to tunnel and blasting. For a drill and blast tunnel, AI is mainly applied for the estimation of blast vibration and rock mass classification, etc. however, there are few cases where it is applied to blast pattern design. Thus, this study attempts to automate tunnel blast design by means of machine learning, a branch of artificial intelligence. For this, the data related to a blast design was collected from 25 tunnel design reports for learning as well as 2 additional reports for the test, and from which 4 design parameters, i.e., rock mass class, road type and cross sectional area of upper section as well as bench section as input data as well as16 design elements, i.e., blast cut type, specific charge, the number of drill holes, and spacing and burden for each blast hole group, etc. as output. Based on this design data, three machine learning models, i.e., XGBoost, ANN, SVM, were tested and XGBoost was chosen as the best model and the results show a generally similar trend to an actual design when assumed design parameters were input. It is not enough yet to perform the whole blast design using the results from this study, however, it is planned that additional studies will be carried out to make it possible to put it to practical use after collecting more sufficient blast design data and supplementing detailed machine learning processes.

• Journal of Korean Society of Forest Science
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• v.111 no.1
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• pp.115-124
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• 2022

This study was conducted to obtain basic data that could help prevent damage caused by slow-moving landslides (land-creep). Specifically, the geological, topographic, and physical characteristics of land-creep were analyzed in Jiphyeon-myeon, Jinju-si. The first and second analyzed land-creeps occurred in 1982 and 2019, respectively. The area damaged in the second land-creep was about 11.5-fold larger than that damaged in the first land-creep. The dominant constituent rock in the land-creep area was sedimentary rock, which seems to be weakly resistant to weathering. The areas that collapsed due to land-creep were related to the presence of separated rocks between the bedding plane in the estimated activity surface over the slope direction and the vertically developed joint surface. Thus, surface water and soil debris were introduced through the gaps of separated rocks. Additionally, the areas collapsed due to the combination of the bedding plane and joint surface shale and sandstone showed an onion structure of weathered outcrop from the edge to inner part caused by weathering from ground water. Consequently, core stones were formed. The study area was a typical area of land-creep in a mountain caused by ground water. Land-creep was classified into convex areas of colluvial land-creep. The landslide-risk rating in the study area was classified into three and five classes. The flow of ground water moved to the northeast and coincided with the direction of the collapse. Soil bulk density in the collapsed area was lower than that in ridge area, which was rarely affected by land-creep. Thus, soil bulk density was affected by the soil disturbance in the collapsed area.