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Abstract The overburden depth of underground caverns in hydropower plants is always huge. When earth surface is considered in mesh discretization，the computation cost is considerable and the computation lowers analysis efficiency. To solve this issue，the dynamic sub-model method is proposed for earthquake response analysis of large-scale underground caverns. This method separates large-scale，coarse-grained calculation of underground seismic motion and small-scale，fine-grained calculation of structural dynamic analysis by performing calculation on seismic field wave model and structural analysis model，respectively. Firstly，based on the transmitting characteristics of seismic wave in deep bedrock，the acceleration data in deep rock mass are estimated by linearly reducing the time-history of ground acceleration data. By inputting the estimated acceleration data along bottom boundary，seismic wave field covering wide range is derived. Afterwards，boundary points of structural analysis model are interpolated in seismic wave field model. The boundary conditions of structural model are then obtained and the earthquake input of structural model is realized. The numerical example indicates that the estimated acceleration data at the bottom boundary take specific engineering conditions into consideration. Therefore the estimated results are more efficient in reflecting actual underground seismic motion than the fixed reduction coefficient in design codes. Meanwhile，the simulation of earth surface reflection of seismic wave has considerable influences on the accuracy of calculation results. The proposed dynamic sub-model method not only guarantees the accuracy of calculation results but also ensures that the earth surface needs not to be modelled. The computation cost is therefore lowered considerably and the computation efficiency is greatly enhanced.
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Received: 09 October 2010
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2011, Vol. 30 
