Documents disponibles écrits par cet auteur

Nongrouted ratio evaluation of rock bolts by reflection of guided ultrasonic waves / Jung-Doung Yu in Journal of geotechnical and geoenvironmental engineering, Vol. 139 N° 2 (Février 2013) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 2 (Février 2013) . - pp. 298-307 Titre : Nongrouted ratio evaluation of rock bolts by reflection of guided ultrasonic waves Type de document : texte imprimé Auteurs : Jung-Doung Yu, Auteur ; Myeong-Ho Bae, Auteur ; In-Mo Lee, Auteur Année de publication : 2013 Article en page(s) : pp. 298-307 Note générale : geotechnique Langues : Anglais (eng) Mots-clés : ultrasonic  methods;  rock  masses;  bolts;  wavelet Résumé : The objective of this study is to develop and apply reflection methods for guided ultrasonic waves used in evaluating the grout condition of rock bolts installed in a rock mass. Three types of rock bolts with different grouting ratios are prepared. First, piezoelectric disk elements are used as the source of guided ultrasonic waves to investigate grouted nonembedded rock bolts. Second, reflection methods with piezo disk elements and hammer impacts are used with rock bolts embedded in concrete columns. Third, a hammer impact with a center punch is applied for investigating rock bolts embedded in a rock mass in the field. The measured guided waves were analyzed using wavelet transforms. The peak magnitudes of the wavelet transform are used for group velocity calculations. Although piezo disk elements are sufficient as sources for nonembedded rock bolts and rock bolts installed in concrete columns, they do not provide sufficient energy in the field. However, a hammer impact with a center punch can generate guided ultrasonic waves with enough energy to evaluate the nongrouted ratio in rock bolts embedded in a rock mass. The group velocities of the guided ultrasonic waves increase with increasing nongrouted ratio. This study demonstrates that the suggested hammer impact method is effective for evaluating the nongrouted ratio of rock bolts in the field. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000767 [article] Nongrouted ratio evaluation of rock bolts by reflection of guided ultrasonic waves [texte imprimé] / Jung-Doung Yu, Auteur ; Myeong-Ho Bae, Auteur ; In-Mo Lee, Auteur . - 2013 . - pp. 298-307. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 2 (Février 2013) . - pp. 298-307 Mots-clés : ultrasonic  methods;  rock  masses;  bolts;  wavelet Résumé : The objective of this study is to develop and apply reflection methods for guided ultrasonic waves used in evaluating the grout condition of rock bolts installed in a rock mass. Three types of rock bolts with different grouting ratios are prepared. First, piezoelectric disk elements are used as the source of guided ultrasonic waves to investigate grouted nonembedded rock bolts. Second, reflection methods with piezo disk elements and hammer impacts are used with rock bolts embedded in concrete columns. Third, a hammer impact with a center punch is applied for investigating rock bolts embedded in a rock mass in the field. The measured guided waves were analyzed using wavelet transforms. The peak magnitudes of the wavelet transform are used for group velocity calculations. Although piezo disk elements are sufficient as sources for nonembedded rock bolts and rock bolts installed in concrete columns, they do not provide sufficient energy in the field. However, a hammer impact with a center punch can generate guided ultrasonic waves with enough energy to evaluate the nongrouted ratio in rock bolts embedded in a rock mass. The group velocities of the guided ultrasonic waves increase with increasing nongrouted ratio. This study demonstrates that the suggested hammer impact method is effective for evaluating the nongrouted ratio of rock bolts in the field. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000767

Tunnel reinforcement by using pressure-induced inflatable pipes method / Jeong-Jun Park in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 12 (Décembre 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 12 (Décembre 2012) . - pp. 1483–1491 Titre : Tunnel reinforcement by using pressure-induced inflatable pipes method Type de document : texte imprimé Auteurs : Jeong-Jun Park, Auteur ; In-Sung Cho, Auteur ; In-Mo Lee, Auteur Année de publication : 2013 Article en page(s) : pp. 1483–1491 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Tunnel  reinforcement  Umbrella  arch  method  Trapdoor  test  Inflatable  pipe Résumé : A new tunnel auxiliary method, the pressure-induced inflatable pipes method, is proposed in this paper. It utilizes the concept of cavity expansion for tunnel reinforcement by forming an umbrella arch on the roof of the tunnel. When each inflatable pipe is inserted and expanded by pressure in the boreholes of the umbrella arch, the ground around the borehole can be compacted so that the stress conditions above the tunnel perimeter are changed favorably. To verify the reinforcement effect of this new concept, a pilot-scale chamber test, numerical analysis, and trapdoor test were performed and compared. In the pilot-scale chamber test, three types of inflatable pipes were tested to check their capability for expansion and each type of pipe was demonstrate to function correctly by expanding only in the intended direction. Numerical analysis of a tunnel and the applied trapdoor tests using the inflatable pipes were also performed to determine the reinforcement effects of the proposed technique. The results imply that the new method with three-directional inflatable pipes can contribute to reducing tunnel convergence and face settlement. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000725 [article] Tunnel reinforcement by using pressure-induced inflatable pipes method [texte imprimé] / Jeong-Jun Park, Auteur ; In-Sung Cho, Auteur ; In-Mo Lee, Auteur . - 2013 . - pp. 1483–1491. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 12 (Décembre 2012) . - pp. 1483–1491 Mots-clés : Tunnel  reinforcement  Umbrella  arch  method  Trapdoor  test  Inflatable  pipe Résumé : A new tunnel auxiliary method, the pressure-induced inflatable pipes method, is proposed in this paper. It utilizes the concept of cavity expansion for tunnel reinforcement by forming an umbrella arch on the roof of the tunnel. When each inflatable pipe is inserted and expanded by pressure in the boreholes of the umbrella arch, the ground around the borehole can be compacted so that the stress conditions above the tunnel perimeter are changed favorably. To verify the reinforcement effect of this new concept, a pilot-scale chamber test, numerical analysis, and trapdoor test were performed and compared. In the pilot-scale chamber test, three types of inflatable pipes were tested to check their capability for expansion and each type of pipe was demonstrate to function correctly by expanding only in the intended direction. Numerical analysis of a tunnel and the applied trapdoor tests using the inflatable pipes were also performed to determine the reinforcement effects of the proposed technique. The results imply that the new method with three-directional inflatable pipes can contribute to reducing tunnel convergence and face settlement. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000725