• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.77-84
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• 2003

Deep excavations in the urban areas have been frequently going on in large scale. Soil-nailing and Earth-anchor supporting methods are generally used in deep excavation. These construction methods cause ground disturbances during drilling process, and damages of adjacent structures and ground due to the differential settlement throughout construction period, and unexpected behaviors of supporting system according to the characteristics of drilling machine and ground condition. This article introduces two actual examples of adjacent deep excavation for the construction of university buildings in granitic Seoul area. The important results of construction and measurements obtained using Crawler drilling machine for Soil-nailing and Earth-anchor supporting methods are summarized. And some suggestions are given to improve and develop the technique of design and construction in the deep excavation projects having similar ground condition and supporting method.

• Journal of the Korean Geosynthetics Society
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• v.11 no.4
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• pp.45-53
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• 2012

Ground drilling is a common method to conduct site investigation, soil improvement, and pile installation. In the point of construction ground drilling requires electrical energy to drill a hole in ground in which the energy exerts into the motor located on the head of auger and generates rotational power. In this paper it is verified that the exerted electrical energy is closely related to the strength characteristics of ground. Measurement sensors, recording system, and drilling system were developed to obtain exerted motor current and drilling depth and laboratory soil box tests were carried out. The measured motor current and boring depth were applied to predict SPT N-value and the prediction results were compared to SPT N-value of laboratory tests. The test results show that the exerted electrical energy to bore ground be a good index to estimate SPT N-value.

• Journal of the Korean Geotechnical Society
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• v.23 no.7
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• pp.57-64
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• 2007

This study proposes a method to estimate drilling torque during ground boring with an aid of electrical energy required for rotating a boring-auger. Ground boring is commonly used in geotechnical engineering such as preboring precast pile installation, soil-cement grouting, ground exploration and so forth. In order to understand the correlation between required electrical energy to rotate the boring auger and the drilling torque, a small laboratory apparatus was designed and a pilot study was performed. The apparatus rotates common drill bits of $D=5{\sim}25mm$ in CBR specimens. The velocity of a bit is 19 RPM and predefined using a reduction gear which connects a main rotation axis to a 25 Watts AC electrical motor shaft. In the middle of drilling the motor current increments and the drilling torque were measured and the correlation between the current and the torque was obtained through linear square fits. Based on the correlation the acquired motor current during drilling was applied to predict the drilling torque in consequent testing and the prediction results were compared to the measured torque. The comparison leads a conclusion that the motor current during drilling using electrical power may be a good indicator to estimate/determine strength characteristics of the ground.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.05a
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• pp.116-119
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• 2000

There has been a steady increase in geoenvironmental engineering projects where geotechnical engineering has been combined with environmental concerns. Many of these projects involve some investigation on contaminant and leachate flume in the ground and landfill. In this study, investigation and assesment on soil and groundwater around the waste landfill was carried out. Many techniques such as drilling and sampling method were applied. As a result of this study, the concentration of soil and groundwater were investigated and analysed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.4
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• pp.561-571
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• 2019

Drilling and charging of the blast holes during NATM tunneling works take more than 30% of construction time among the whole tunneling work process. Prediction of ground condition ahead of tunnel face has been studied by several researchers by correlating percussion pressure and drilling speed during tunneling work with the ground condition and/or RMR values. However, most of the previous researches were conducted in the granite rock condition which is the most representative igneous rock in the Korean peninsula. In this study, drilling speeds in igneous rocks were analyzed and compared with those in sedimentary rocks (most dominantly composed of conglomerates, sandstones, and shales) under the similar RMR ranges; it was identified that the drilling speed is pretty much affected by rock types even in a similar RMR range. Under the similar RMR values, the drilling speed was faster in sedimentary rocks compared with that in igneous rock. Moreover, while the drilling speed was not much affected by change of the RMR values in igneous rocks, it became faster in sedimentary rocks as the RMR values got lower.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.481-485
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• 2000

Vibration screening trench is very effective to reduce the ground vibration, but to construct the trench in the rock mass is not easy. Various line drilling methods have been tried to replace the trenching. In this study, UDEC was applied to simulate the screening effect of drilling holes in 2 dimensional ground model. Field measurement was conducted and compared to numerical analysis.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.235-239
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• 2000

Vibration screening trench is very effective to reduce the ground vibration, but to construct the trench in the rock mass is not easy. Various line drilling methods have been tried to replace the trenching. In this study, UDEC was applied to simulate the screening effect of drilling hopes in 2 dimensional ground model. Field measurement was conducted and compared to numerical analysis.

• Journal of Environmental Science International
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• v.27 no.8
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• pp.677-688
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• 2018

The purpose of this study was to minimize salt water intrusion into freshwater aquifers and limit the development of freshwater aquifers, by selecting an appropriate excavation depth of in the western coastal area of Jeju Island. The study site was mostly basaltic lava, which was mainly composed of trachy basalt. A vertical logging test was conducted to investigate the vertical distribution of the groundwater and saline groundwater interface in the study well. It was found that freshwater groundwater, saline groundwater, and freshwater groundwater are distributed from the surface to approximately 16 m, 16~50 m, and 50~60 m, below the ground, respectively. In order obtain saline groundwater and minimize the inflow of freshwater into this well, the drilling depth should be limited in the range of 16~50 m from the surface. Thus, saline groundwater well development should be carried out with reference to the measurement results, which depend on the drilling depth and EC (electrical conductivity) obtained with drilling apparatus for geology and ground handling.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.698-705
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• 2005

This study contains actual scaled site experiments on mediation factors affecting ultimate pulling force of the buoyancy resisting anchor which is installed underground water level suffering buoyancy force and breaking mechanism. Site buoyancy test selected the buoyancy acting site where acting buoyancy to the station structure since the stream and reservoir is neighboured to the vicinity ground and executed site experiments leading to variation of anchoring length, drilling diameter and tendon diameter at the weathered rock ground. The test result showed that pulling force getting increased more and more proportionate to increase of anchoring length, drilling diameter and tendon diameter, and as a result of analysis for correlations between anchoring length-ultimate limited load and drilling diameter-ultimate load (on the basis of 254mm settlement), modulus of correlation showed very high relation 0.9 and 0.99 respectively and correlation formular showed the limited load is increasing proportionate to cubic meters of anchoring length as well as the ultimate load proportionate to alignment of drilling diameter. It is also showed that limited load increased about 42.5% from 392kN to 559kN as a result of change the tendon diameter to 36mm and 50mm.

• Journal of the Korean Geosynthetics Society
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• v.11 no.4
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• pp.55-62
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• 2012

In this application study, field pilot tests were performed to evaluate the validity of a proposed formula between the exerted electrical energy and SPT N-value based on the result of the basic study. Measurement sensors and recording system were developed to obtain exerted motor current and drilling depth in a field. By using the correlation formula proposed in the basic study, the measured motor current and boring speed were applied to predict SPT N-value and the predicted N-values were compared to SPT N-value of site exploration. From the comparisons it is verified that the exerted electrical energy to bore ground might be used to predict SPT N-value and pile tip location.