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Yan P.,Hubei Engineering University | Yan P.,East China Investigation and Design Institution under CHECC | Lu W.B.,Hubei Engineering University | Luo Y.,Hubei Engineering University | Chen M.,Hubei Engineering University
Rock Fragmentation by Blasting - Proceedings of the 9th International Symposium on Rock Fragmentation by Blasting, FRAGBLAST 9 | Year: 2010

Field observation and primary study indicated that the vibration induced by blast excavating process under high in-situ stress condition consists of vibration induced by blasting load (VIB) and vibration induced by in-situ stress dynamic (or transient) unloading (VIDU). In this paper, the vibration monitored in the process of blasting excavation under both low and high geo-stress condition are analyzed with the help of wavelet transform. Firstly, the arriving moment of VIDU in the monitoring vibration is identified, employing the time-energy density analysis based on the wavelet transform method. Secondly, by means of the wavelet packet analysis technique, the energy distribution of the monitoring vibrations on different frequency bands is studied. The result reveals that VIDU falls behind the VIB for about 10∼100 ms in the monitoring vibration signals corresponding to every millisecond delay of blast, which is in accordance with theoretical analysis and the results of high-speed photography experiments. And the proportion of low frequency energy of the vibration monitored in high geo-stress area is higher than that monitored under low geo-stress condition, which indicates that the VIDU contains much more low frequency energy. The effect of dynamic unloading is determined by the magnitude of in-situ stress and the length of unloading contour, and both of them are determined by the arrangement of blast holes and explosive circuit. © 2010 Taylor & Francis Group.


Shan Z.-G.,East China Investigation and Design Institution under CHECC | Yan P.,East China Investigation and Design Institution under CHECC
Bulletin of Engineering Geology and the Environment | Year: 2010

Rock mass breakage induced by high in situ stresses during excavation of deep tunnels is one of the key problems in the construction of the Jinping II Hydropower Station. It is not only a threat to the safety of workers, but also seriously affects the construction process. This paper discusses where the rock bursts occur, how they occur and how to reduce their effect. © 2010 Springer-Verlag.


Li S.,CAS Wuhan Institute of Rock and Soil Mechanics | Feng X.,CAS Wuhan Institute of Rock and Soil Mechanics | Zhang C.,East China Investigation and Design Institution under CHECC | Li Z.,Northeastern University China | And 3 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

It presents the in-situ test on excavation damaged zone(EDZ) evolution of TBM tunnel No.3in Jinping II hydropower station using digital panoramic borehole camera. Firstly, through the pre-excavated diversion tunnel No.2-1, several boreholes vertical to sidewall of TBM tunnel No.3are drilled for digital camera, and a series of digital images of borehole wall are obtained during the whole TBM driven time. Afterwards, the images will be digitally processed; geological structural surface and fractures of surrounding rock mass are also analyzed, which makes it possible for the whole procedure of cracks formation, development and close to be obtained. Finally, the depth of damage zone is recognized; the relationship between fractures evolution and TBM construction progress is given; and the mechanism of EDZ evolution is discussed as well. It will not only provide the direct data for geological exploration but also contribute greatly to support design and analysis of deformation behaviors of deep-buried tunnels.


Zheng H.F.,East China Investigation and Design Institution under CHECC | Wu G.Y.,East China Investigation and Design Institution under CHECC
Rock Mechanics: Achievements and Ambitions - Proceedings of the 2nd ISRM International Young Scholars' Symposium on Rock Mechanics | Year: 2012

Block element method (BEM) for dynamic analysis is developed and applied to historic stability analysis of rock slope. Combining the idea of visco-elastic boundary with the theory of BEM, the artificial boundary condition of BEM is formulated. Visco-elastic boundary has the merits of numerical stability and convenience to integrate with computational program. The inertial force of rock block is firstly computed from its acceleration obtained by dynamic analysis and then decomposed according to supposed sliding model into sliding force and force perpendicular to the supposed sliding direction, which is used for calculating resistance force. The stability factor against sliding is defined by the ratio of the resistance force to the sliding force. As the seismic process finishes, the time-history curve of stability factor against sliding of rock block can be obtained. The application of the water intake slope in a hydropower project demonstrates the capacity of this method. © 2012 Taylor & Francis Group.

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