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postgraduate thesis: The effects of joints on rock masses under blast-induced vibrations

TitleThe effects of joints on rock masses under blast-induced vibrations
Authors
Issue Date2016
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Citation
Zhou, J. [周建梅]. (2016). The effects of joints on rock masses under blast-induced vibrations. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5736694
AbstractExplosive controlled blasting is an effective method in underground construction for rock breakage in the utilization of urban underground space. At the same time, the blast-induced vibration is a major concern. In general, site specific empirical relationships between the maximum vibration magnitude (called peak particle velocity, PPV) and the scaled distance (SD), which is a collective parameter taking into account the amount of explosive and spatial distance between the explosive source and the point of measurement are derived using filed records. Yet, the influence of rock joints on the wave propagation has been seldom systematically investigated. The prime objective of this study was to achieve a better understanding of the effects of joints in the propagation of vibrational waves. A number of sub-tasks were performed to reach the goal. A transmitted plane wave propagating through a jointed rock mass was investigated with the finite difference package FLAC2D. The joint was simulated as an interface between two elastic rock bodies. As the properties of joint have great effects on the amplitude and frequencies of transmitted wave, the relationship between joint stiffness and the amplitude of transmitted wave in form of transmitted coefficient was described. The wave propagation through multiple joints with different orientations and various spacing was studied. The influence of roughness in joint during wave transmission was examined. With different frequencies of incident wave applied to the jointed rock mass, the effects of frequency in wave propagation were studied. It was found that the properties of joints have great effects on the transmitted coefficients. The number and orientations of joints influence the amplitude of transmitted wave pronouncedly. The numerical study on propagation of blasting wave in hypothetical rock slopes with and without joints applied was carried out. The blast wave was simulated using AUTODYN in which the amount of explosive was considered as an input. The relationship between peak PPV and SD was studied by considering different distributions of joints and different locations of the blasting source. It was found that the joints have noticeable influence on the relationship between PPV and SD. The influence on the slope angle on PPV and SD was also examined. The extensive numerical simulations showed that the empirical relations between PPV and SD obtained at early stages of a tunnel blasting where the blasting source was noticeably away from the slope might give unsafe prediction of PPV when the blast source became close to the slope.
DegreeDoctor of Philosophy
SubjectBlasting
Rock mechanics
Dept/ProgramCivil Engineering
Persistent Identifierhttp://hdl.handle.net/10722/225223

 

DC FieldValueLanguage
dc.contributor.authorZhou, Jianmei-
dc.contributor.author周建梅-
dc.date.accessioned2016-04-28T06:50:58Z-
dc.date.available2016-04-28T06:50:58Z-
dc.date.issued2016-
dc.identifier.citationZhou, J. [周建梅]. (2016). The effects of joints on rock masses under blast-induced vibrations. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5736694-
dc.identifier.urihttp://hdl.handle.net/10722/225223-
dc.description.abstractExplosive controlled blasting is an effective method in underground construction for rock breakage in the utilization of urban underground space. At the same time, the blast-induced vibration is a major concern. In general, site specific empirical relationships between the maximum vibration magnitude (called peak particle velocity, PPV) and the scaled distance (SD), which is a collective parameter taking into account the amount of explosive and spatial distance between the explosive source and the point of measurement are derived using filed records. Yet, the influence of rock joints on the wave propagation has been seldom systematically investigated. The prime objective of this study was to achieve a better understanding of the effects of joints in the propagation of vibrational waves. A number of sub-tasks were performed to reach the goal. A transmitted plane wave propagating through a jointed rock mass was investigated with the finite difference package FLAC2D. The joint was simulated as an interface between two elastic rock bodies. As the properties of joint have great effects on the amplitude and frequencies of transmitted wave, the relationship between joint stiffness and the amplitude of transmitted wave in form of transmitted coefficient was described. The wave propagation through multiple joints with different orientations and various spacing was studied. The influence of roughness in joint during wave transmission was examined. With different frequencies of incident wave applied to the jointed rock mass, the effects of frequency in wave propagation were studied. It was found that the properties of joints have great effects on the transmitted coefficients. The number and orientations of joints influence the amplitude of transmitted wave pronouncedly. The numerical study on propagation of blasting wave in hypothetical rock slopes with and without joints applied was carried out. The blast wave was simulated using AUTODYN in which the amount of explosive was considered as an input. The relationship between peak PPV and SD was studied by considering different distributions of joints and different locations of the blasting source. It was found that the joints have noticeable influence on the relationship between PPV and SD. The influence on the slope angle on PPV and SD was also examined. The extensive numerical simulations showed that the empirical relations between PPV and SD obtained at early stages of a tunnel blasting where the blasting source was noticeably away from the slope might give unsafe prediction of PPV when the blast source became close to the slope.-
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subject.lcshBlasting-
dc.subject.lcshRock mechanics-
dc.titleThe effects of joints on rock masses under blast-induced vibrations-
dc.typePG_Thesis-
dc.identifier.hkulb5736694-
dc.description.thesisnameDoctor of Philosophy-
dc.description.thesislevelDoctoral-
dc.description.thesisdisciplineCivil Engineering-
dc.description.naturepublished_or_final_version-

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