等应力比路径下堆石料双屈服面弹塑性模型研究

RESEARCH ON ELASTOPLASTIC MODEL WITH DOUBLE YIELD SURFACES UNDER CONSTANT STRESS RATIO PATH

已有研究及实测资料表明,土石坝内堆石料在填筑期应力路径接近等应力比关系,且这种关系并不因材料混杂、施工分期复杂而发生本质性改变。应力路径较大程度上影响了堆石料的受力变形特性,以往按室内常规三轴试验路径建立的本构模型及标定的参数直接推广至实际坝体路径的计算可能存在较大的误差。通过分析糯扎渡、水布垭及三板溪等堆石料等应力比三轴试验应力-应变曲线特点,认为体积应力-体积应变(p-v)及偏应力与广义剪应变(q-s)曲线具有幂函数规律。以常规南水双屈服面模型(沈珠江模型)为基础,将等应力比应力-应变规律引入模型中,在p-q平面内推导适合等应力比应力路径的双屈服面弹塑性模型,通过对试样在等应力比三轴试验中塑性应变增量方向的分析,探讨适合等应力比路径变形特性的f1屈服面的合理形态。以糯扎渡水电站主堆料等应力比三轴试验为例确定模型参数标定方法,且对模型适应性进行初步分析。

The measured data from soil stressometer located in dam and achievements of previous researchers both showed that the stress path of rockfill during filling period is close to constant stress ratio state.This rule will not change because of the complicate material partition and construction stages.The stress path influences the deformation properties of rockfill in greater degree.The constitutive models and corresponding parameters obtained under the conventional triaxial experiments path may not play its role correctly for the real dam stress path.From the characters of stress-strain of Nuozhadu,Shuibuya and Sanbanxi rockfill materials,the v p-.and s q-.curves can be fitted with power function.Based on the Nanshui elastoplastic model with double yield surface（Shenzhujiang model）,an elastoplastic model with double yield surfaces in the p-q plane was established,which is suitable for constant stress ratio path.According to the direction of plastic strain increment,the reasonable shape of yield surface about 1 f under constant stress ratio path is investigated.Finally,taking the Nuozhadu dam main rockfill for case study,the model parameters are determined and the applicability of the model is analyzed primarily.