基于大型真三轴试验的粗粒料非线性剪胀模型研究

The engineering practices of construction high earth-rockfill dams show that, as the main filler of dams, the constitutive model of coarse-grained material will influnce the accuracy in analysis the deformation of dams greatly, especially whether the factor of dilatancy is taken into account reasonability. Although the non-linear and elastic-plastic are well depicted in some existing constitutive model of coarse-grained, but the dilatancy is not taken into account reasonablility. So, it's a key scientific problem to establish a new constitutive model for coarse-grained material, which is possible to reflect the dilatancy property in analysis the deformation mechanism of high earth-rockfill dams with complex stress paths. In this research project, large-scale true triaxial apparatus is used in researching the mechanical properties of coarse-grained material, and the factor of complex stress status and stress pathes are taken into account, it will reveal the deformation mechanism of coarse-grained material under complex stress conditions; the minimum energy ratio coefficient in Rowe's dilatancy equation is available in describing the mechanical response properties of coarse-grained material during the whole deformation process, a new dilatancy equation especially for coarse-grained material will be proposed. Then, combine with the nonlinear dilatancy constitutive model based on conventional triaxial test which is proposed by the applicant in former, a new nonlinear constitutive model that is possible to reflect the dilatancy of coarse-grained material reasonably will be established. On this basis, the FEM program of this model will be developed in ABAQUS, by comparison with the deformation monitoring data of typical high earth-rockfill dams, the applicability of this model can be verified. The research results will support a new theory method in analysis the stress distribution and deformation regular of high earth-rockfill dams.

高土石坝的工程实践表明，作为大坝主要填料的粗粒料，其本构模型反映其剪胀性的合理性直接影响大坝变形分析的准确性。现有常用的粗粒料本构模型对其非线性、弹塑性等特性均已有较好的反映，但对剪胀性的反映还不够合理。因此，发展能较好描述粗粒料剪胀性的本构模型是高土石坝变形分析的关键科学问题。本项目将以粗粒料为研究对象，首次采用大型真三轴仪开展复杂应力状态和应力路径下粗粒料的变形特性试验研究，揭示复杂应力条件下粗粒料的变形机理与变形特性；研究粗粒料的 Rowe剪胀方程中最小能比系数在复杂应力条件下的响应特征及其变化规律，提出适用于粗粒料的剪胀方程；结合申请人以往依据常规三轴试验提出的非线性剪胀模型，建立一种能合理反映粗粒料剪胀性的非线性本构模型；在此基础上，基于Abaqus平台开发模型有限元程序，并依据典型高土石坝监测成果，验证模型实用性。研究成果可为高土石坝应力变形分析提供新的理论基础和分析方法。

高土石坝的工程实践表明，作为大坝主要填料的粗粒土，其本构模型反映其剪胀性的合理性直接影响大坝变形分析的准确性。现有常用的粗粒土本构模型对其非线性、弹塑性等特性均已有较好的反映，但对剪胀性的反映还不够合理。本项目以我国西南某高土石坝粗粒土填料为研究对象，首次采用大型微摩阻真三轴仪开展复杂应力状态和应力路径下粗粒土的变形特性试验研究，揭示了复杂应力条件下粗粒料的变形机理与变形特性；在此基础上，假设土的应变分为弹性应变和剪胀应变，弹性应变与应力间服从广义虎克定律，剪胀应变服从Rowe剪胀方程，弹性泊松比为常数，完整的建立三参量Kp、Kq、G与应力关系式，提出了一种三参量的非线性K-G模型，模型参数均具有明确的物理意义，并给出了参数的确定方法；基于大型通用有限元计算软件ABAQUS开发了本构模型程序；依托某面板堆石坝工程，考虑实际工程的施工及分期蓄水过程，开展了三维数值仿真计算分析，研究结果表明，采用本研究提出的三参量K-G剪胀模型，计算得到的高面板堆石坝混凝土面板变形及受力状态、坝体沉降和水平变形关系方面更加符合客观实际，验证了模型实用性。研究成果可为高面板堆石坝工程的设计、施工及运行提供理论依据。