【摘要】 水电站地下洞室群埋深大,在动力分析时若将模型建至地表将使网格规模庞大,不利于分析效率的提高。提出适合于大型地下洞室群地震响应分析的动力子模型法。该方法将大范围、粗网格的地下地震波动场计算与小范围、细网格结构动力计算分开,分别建立粗网格和细网格模型进行分析。首先,根据深部基岩的地震波传播特性,采用幅值线性折减的方法对地表加速度时程向基岩深处推算,得到在模型底边界的加速度时程,再输入模型可算得大范围的地震波动场。其次,把结构计算模型边界节点放入波动场计算模型中插值,可获得计算模型边界条件,最后,完成地震荷载的输入。算例表明,推算所得模型底部加速度时程考虑工程具体条件,比规范规定的单一折减系数更能反映实际工程的地下地震动特性。同时,在地下洞室的地震响应分析中,地震波过早被地表反射或不考虑地震波的反射,都会对计算结果造成误差,动力子模型方法能够在保证计算结果精确性的同时,使细网格的计算模型不建至地表自由面,可显著缩减网格规模,提升动力计算效率。更多还原

【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.更多还原