河床式水电站厂房地震响应软弱基岩弹模敏感性分析

针对水工抗震设计规范的修订情况,以某软弱基岩河床式水电站厂房为例,对中间标准机组段建立基础—厂房整体有限元模型,研究设计反应谱特征周期和下降段衰减系数变动对厂房结构地震动响应的影响,然后依据《水电工程水工建筑物抗震设计规范》(NB 35047—2015)定量分析软弱基岩弹模变化对河床式水电站厂房自振特性及静动力响应的影响规律。结果表明:由于反应谱特征周期与衰减系数的调整,该厂房依照《水电工程水工建筑物抗震设计规范》(NB 35047—2015)所得响应较《水工建筑物抗震设计规范》(DL 5073—2000)更为剧烈,第一主应力与总位移可分别提高36.3%和29.8%,增强程度不可忽视。基岩弹模低于5.0 GPa时,厂房对基岩弹模的变化十分敏感,较小的改变也会显著影响厂房在静动力荷载环境下的应力、位移和变形等响应;基岩弹模高于5.0 GPa时,厂房对其变化不再敏感。可见,必须重视软弱基岩弹性模量参数改变的情况,这种改变将对其上建筑物的静动力计算结果产生不可忽视的影响。

Analysis on sensitivity of soft rock foundation elastic modulus on seismic response of run-of-river hydropower station

In accordance with the revision of the specifications for seismic design of hydraulic structures, a holistic finite element model of foundation-powerhouse for the intermediate standard section for generating unit is established by taking a run-of-river hydropower station on soft foundation rock as the study case, and then the impacts from both the characteristic cycle of the design response spectrum and the change of the attenuation coefficient of the declined section on the dynamic seismic response are studied, thereafter, the changing law of the impact from the elastic modulus of the soft foundation rock on the self-vibration characteristics and the static-dynamic response of the powerhouse of the run-of-river hydropower station is quantitatively analyzed in accordance with “Code for Seismic Design of Hydraulic Structure of Hydropower Project” ( NB 35047—2015) . The result shows that due to the adjustments of both the cycle of the response spectrum and the attenuation coefficient, the response of the powerhouse obtained according to“Code for Seismic Design of Hydraulic Structure of Hydropower Project” ( NB 35047—2015) is more strong than that got from“Specifications Seismic Design of Hydraulic Structures” ( DL 5073—2000) , from which the first principal stress and the total displacement are increased by 36. 3% and 29. 8% respectively, which cannot be neglected. When the elastic modulus of the foundation rock is lower than 5. 0 GPa, the powerhouse is quite sensitive to the change of the elastic modulus; that is to say, under static-dynamic loading condition, the responses of stress, displacement and deformation of the powerhouse can be significantly impacted by only a little change. When the elastic modulus of the foundation rock is higher than 5. 0 GPa, the powerhouse is not so sensitive to the change. It is thus obvious that it is necessary to pay an important attention to the change of the parameter of the elastic modulus of the soft foundation rock, as the change is to cause non-negligible impact on the static-dynamic calculation result of the superposed structure over it.