| With the spread of international terrorism and the increasing chemical explosion accident, anti-explosion, explosion protection and disaster mitigation for various kinds of urban infrastructure and lifeline projects have been become one of the more and more important research projects. Presented in this dissertation are systematic research results on experimental tests, numerical simulation and physical interpretation for dynamic responses of urban shallow-buried tunnels subjected to explosion loadings. Special attention has been paid to developing the explosion centrifugal modeling technology and research method of combining physical modeling and numerical simulation. The main achievements and conclusions can be drawn as follows:1) A new explosion centrifugal modeling system and related testing technologies were successfully developed. The system has high data acquisition frequency (maximum frequency up to 20MHz/s), small boundary effect and stable testing performance. A series of explosion centrifugal modeling tests confirmed that the similitude laws can be well satisfied in all the tests and consequently the explosion centrifugal modeling technology is a very effective, reliable and low-cost approach to realize the actual dynamic response of level ground and shallow-buried tunnels under various explosion loadings.2) Three kinds of explosion centrifugal modeling tests, including level ground, shallow-buried tunnel explosion and explosion protection, have been made with the new developed test system. Several valuable experimental facts and laws are observed and found in the following: (1) For the conditions where the dynamite quality, buried depth of the explosives and soil property are the same. there exists a unique relationship between the level ground model peak acceleration and Hopkinson scale distance centrifugal geometric scale, independent of the centrifugal geometric scale N. From this important fact, the parameters in the widely used Drake equation C, n can be easy to be determined by centrifugal modeling, which provides an efficient and convenient way to predict the peak acceleration attenuation of the prototype level ground; (2) Dynamic response laws and failure modes of shallow-buried tunnels were revealed by explosion centrifugal modeling under the conditions of different explosive quality, depth, soil character, medium moisture content and thickness of the tunnel structure. With the increasing intensity of explosion the structure near the source of explosion displays such a damage or failure mode from a slight crack, local cracks, penetrating cracks, bending damage to punching failure, even overall collapse; (3) Blast-resistant protective tests confirmed that the dynamic response of the tunnel is significantly reduced through lining a soft backfill material layer outside the tunnel, showing the effectiveness of the protective composition structure composed of the"foundation-backfill layer-tunnel".3) Numerical model of the"explosives-structure-geomedia-backfill layer"and contact algorithm of different parts are rationally considered based on the famous software ANASYS/Ls-Dyna. Their validity is then verified through comparing the numerical simulation and centrifugal modeling tests. The anti-explosion or anti-seismic effects of the backfill layer are intensively investigated for different complex conditions, showing that the methodology of research and analysis by combining the physical test and numerical simulation is a powerful tool to the study on various anti-explosion problems. |
