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Local Dynamic Response of a Masonry Structure to the Vibrations of Tunnel Blasting
(1 School of Civil Engineering, Qingdao University of Technology, Qingdao 266033; 2 Hebei Research Institute of Construction &
Geotechnical Investigation Co. Ltd., Shijiazhuang 050031; 3 Hebei Research Center of Geotechnical Engineering Technology of
Province, Shijiazhuang 050031; 4 School of Civil Engineering, Beijing Jiaotong University, Beijing 100044; 5 School of Civil
Engineering, Tsinghua University, Beijing 100084; 6 Beijing No.2 Municipal Construction Engineering Ltd. Corp., Beijing 100037)
Abstract Based on the New Hongyan tunnel of the Chengdu- Chongqing Passenger Dedicated Line, a typical
blasting vibration wave and a two-layer masonry structure were selected to analyze the low-order integrated mode and high-order local mode of the masonry structure. The characteristics of displacement and the stress response of the structure to vibrations during tunnel blasting were studied using the modal displacement superposition method.The distribution and variation of the principal tensile stress of brick walls under different particle peak velocities were calculated. The results show that for a typical two-layer masonry structure, the first five stages are of a low-or?der integrated mode with natural frequencies in the range of 8.80~24.86 Hz and vibration modes that are integrated uniform deformations, while the 6th to 20th stages are of a high-order local dense mode with natural frequencies in
the range of 25.96~36.14 Hz and local deformations that are significantly larger than the integrated deformations;the structural displacement induced by high-frequency vibration modals is very small, but the internal force response of local elements are much larger than the displacement since the modal amplitude vector of the internal force calculation is multiplied by the square of the modal frequency; the structure dynamic damage induced by the tunnel blasting vibration is mainly controlled by the instantaneous high stress rather than the displacement; and under intense vibrations, tensile stresses are high at the brick doors, window corners, contact areas of brick and concrete elements with a stress concentration, parapet wall, side-walls, partition walls and balconies and this is where damage often occurs.
Abstract：
Based on the New Hongyan tunnel of the Chengdu- Chongqing Passenger Dedicated Line, a typical
blasting vibration wave and a two-layer masonry structure were selected to analyze the low-order integrated mode and high-order local mode of the masonry structure. The characteristics of displacement and the stress response of the structure to vibrations during tunnel blasting were studied using the modal displacement superposition method.The distribution and variation of the principal tensile stress of brick walls under different particle peak velocities were calculated. The results show that for a typical two-layer masonry structure, the first five stages are of a low-or?der integrated mode with natural frequencies in the range of 8.80~24.86 Hz and vibration modes that are integrated uniform deformations, while the 6th to 20th stages are of a high-order local dense mode with natural frequencies in
the range of 25.96~36.14 Hz and local deformations that are significantly larger than the integrated deformations;the structural displacement induced by high-frequency vibration modals is very small, but the internal force response of local elements are much larger than the displacement since the modal amplitude vector of the internal force calculation is multiplied by the square of the modal frequency; the structure dynamic damage induced by the tunnel blasting vibration is mainly controlled by the instantaneous high stress rather than the displacement; and under intense vibrations, tensile stresses are high at the brick doors, window corners, contact areas of brick and concrete elements with a stress concentration, parapet wall, side-walls, partition walls and balconies and this is where damage often occurs.
2017, Vol. 54 