• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.15-16
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• 2023

In this paper, we aimed to develop a new method for diagnosing the depth of neutralization in architectural and civil engineering structures using the core drilling method, which combines the speed of drilling with the accuracy of core ringing. When compared to the drilling method, the core drilling method showed a lower measurement deviation of 1-2mm (7.6%) in confirming the depth of neutralization. This is believed to be a result of potential interference during the sample collection process in the drilling method, where the drill may pass through aggregates, leading to overestimation, as indicated in previous studies. The rapid evaluation of neutralization using the core drilling method serves as an alternative to address the issues associated with both drilling and core ringing methods in diagnosing the depth of neutralization. It offers a solution to the inaccuracy caused by coarse aggregates and the cumbersome post-processing steps required for neutralization diagnosis. Our proposed technique aims to provide an accurate and expedited diagnosis of neutralization depth without the need for additional processes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.103-111
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• 2015

To evaluate the compressive strength of concrete, rebound test and ultra pulse velocity methods as well as core test were widely used. The predicted strength effected by age, maturity and degradation of concrete, is a slight difference between in-situ concrete strength. The compressive strength of standard cylinder specimens and core samples by obtained from drilling will have a difference since the concrete is disturbed during the drilling by machinery. And the rebound number and ultra pulse velocity are also changed according to the age and maturity of concrete that effected to the surface hardness and microscpic minuteness. The authors performed the experimental work to reflect the age and core effect to the results from NDE test. The test results considering on the core and age of concrete were compaired with the proposed equation to predict the compressive strength.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3175-3184
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• 1994

The high strength and wear-resistant metal bonded diamond wheel was applied to the drilling process of carbon fiber reinforced plastics (CFRP), The helical-feed drilling method was use for the first time to overcome the limit of drilling depth of the conventional drilling process and to improve the dressing of the wheel. The helical-feed drilling method was found effective at high cutting speed without the limit of drilling depth.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.95-103
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• 2008

Diamond core drills are applied to drill difficult-to-cut materials. This paper proposes basic understanding of ceramic drilling mechanics and characteristics of main factors affecting tool life, tool wear, cutting force, and chipping thickness. In contrast to conventional drilling, the core drilling process make deep grooves on the workpiece. One difficulty of it is the evacuation of chips from the drilled groove. As the drilling depth increases, an increased amount of chips tend to cluster together and clog the groove. Eventually severe wear develops and diamond grits are separated from the drill body. To relieve the clogging problem and to evacuate chips from the groove easily, the helical drilling process is applied for the core drilling process. To analyze drilling characteristics and derive optimal drilling conditions, tool life, tool wear, cutting force, and chipping thickness are quantified through the monitoring system and the Taguchi method. Mathematical models for the tool life and chipping thickness are derived from the response surface method. Optimal drilling database has been constructed through the experimental models.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.1
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• pp.135-144
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• 2020

Since the depth of tunneling with tunnel boring machine (TBM) becomes deeper and deeper, the expense for site investigation for coring and geophysical survey increases to obtain the sufficient accuracy. The tunnel ahead prediction methods have been introduced to overcome this limitation in the stage of site investigation. Probe drilling can obtain the core and borehole images from a borehole. However, the space in TBM for the probe drilling equipment is restricted and the core from probe drilling cannot reflect the whole tunnel face. Seismic methods such as tunnel seismic prediction (TSP) can forecast over 100 m ahead from the tunnel face though the signal is usually generated using the explosive which can affect the stability of segments and backfill grout. Electromagnetic methods such as tunnel electrical resistivity prospecting system (TEPS) offer the exact prediction for a conductive zone such as water-bearing zone. However, the number of electrodes installed for exploration is limited in small diameter TBM and finally the reduction of prediction ranges. In this study, the theoretical equations for the electrical resistivity survey whose electrodes are installed in the face and side of TBM to minimize the installed electrodes on face. The experimental tests were conducted to verify the derived equations.