Study On Dynamic Response And Safety Criterion Of Buildings To Blasting Vibration Waves

At the meantime of widespread application of the blasting technology, a series of negative effects induced by engineering blasting especially blasting vibration effect which is regarded as head of blasting hazards has been commonly focused with the increasing of complication of blasting surroundings and people's consciousness for environmental protection. To study the damaging mechanism of blasting vibration effect especially to study the mechanism of dynamic response of surrounding buildings induced by blasting vibration waves is the key and difficult subject in research field for blasting vibration effect, which is also the important content for blasting safety technique.Combining National Natural Science Foundation of China named "Study on Characteristics of Blasting Vibration and Structural Damaging Mechanism Induced by Blasting Vibration" (No:50778107)and Research Fund for the Doctoral Program of Higher Education of China named "Study on Characteristics of Blasting Vibration and Safety Control Theory of Structural Blasting Vibration" (No:20060424002), on the background of consulting and lucubrating on a great many domestic and overseas references related and with the support of related theories and analytical methods such as explosion dynamics, structural dynamics, numerical analysis, signal analytical technology, dynamic finite element theory and etc., characteristics of propagation of blasting vibration waves and structural dynamic response induced by blasting vibration waves and its corresponding safety standard were discussed deeply and systematically by the main studying means of numerical calculation, finite element simulation and field tests in this dissertation. The main research findings are as follows:(1) Based on discussing the influence-zone division of blasting vibration by numerical calculation and a large number of data obtained by field monitoring, the attenuation laws of the amplitude and basic frequency of blasting vibration waves versus scaled distance and spectrum and energy characteristics of blasting vibration waves in different vibration zone were studied.(2) Velocity loads of blasting vibration waves of different characteristic parameters were applied to the foundation base of a multi-freedom elastic structural system, and dynamic responses of the structural system under different conditions were calculated in central impulse method. By analyzing changes of peak values of all the structural dynamic responses, effects of the amplitude, frequency and duration of blasting vibration waves on dynamic response of the multi-freedom elastic structure were discussed.(3) A set of programs for solving elastic-plastic seismic response of multi-storey masonry buildings was written by Matlab, which combined Newmark time-history method with two-linear model of stiffness degradation. A four-storey masonry building was taken as the analyzed object, and the actual and artificial-simulated blasting vibration waves of different characteristic parameters were used as the input loads. According to the calculated results of amplitude for all structural elastic-plastic seismic response, effects of the amplitude, basic frequency and duration of blasting vibration waves on elastic-plastic seismic response of multi-storey masonry buildings were discussed respectively.(4) A large number of blasting vibration response signals of a reinforced concrete building were monitored by locating monitoring points on the multi-storey reinforced concrete building along the height and horizontal direction, which was under-drilled through in the course of blasting excavation of a tunnel. Distribution characteristics of the spectrum, energy and amplitude variation laws of structural response of the reinforced concrete building to the blasting vibration waves in all directions along the height and horizontal direction of the building were studied with the method of wavelet analysis combined with FFT.(5) Complex monitoring velocity signals of blasting vibration waves were transformed to superposition of several simple harmonic waves by the means of decomposition and reconstruction of wavelet packet. In this way, the problem of structural dynamic response under the action of blasting velocity loads became the problem of that under a series of simple harmonic loads. By introducing a new concept of velocity factor and bringing it into the calculation model of blasting vibration effect, the contribution of structural transient response was considered into structural dynamic response. At the meantime, normalized energy proportion was added to the calculation model, and only dominant frequencies of relatively large energy proportions could be included when considering the influence of frequencies of blasting loads. Then, a new safety criterion of blasting vibration effect was put forward on the model above, which can reflect the relation among value of structural velocity response under stimulation of blasting loads and parameters of structural characteristics, amplitude, frequencies (including several dominant frequencies), duration and energy proportion of blasting vibration waves.(6) A three-dimensional solid model was built for an actual three-storey masonry building in blasting filed with dynamic finite element method. Monitoring signals of blasting vibration waves at the bottom of the building were loaded onto the foundation base of the masonry model, and values of blasting vibration response of the other masonry storey calculated with dynamic finite element method were compared with the monitoring results. One representative structure was separately selected among common masonry buildings of 2～4 storeys to build finite element model, and blasting vibration waves of different basic frequencies were loaded on its base nodes in vertical direction and cracking course of the model was simulated. Safety standards of blasting vibration for representative masonry buildings of 2-4 storeys under blasting vibration waves of different basic-frequency bands were given, which were obtained by defining critical failure state of structural element.The research findings obtained in this dissertation are of important theoretical values and practical significance for scientifically forecasting and controlling hazards of blasting vibration effect of surrounding buildings and improving and consummating the existing safety criterion of blasting vibration.