考虑颗粒破碎影响的堆石料临界状态理论及本构模型

The deformation of high earth and rockfill dams, especially the long-term deformation, is a difficult problem which has yet to be satisfactorily addressed. The deformation is related to the mechanical characteristics of rockfill materials, which are affected by the particle breakage. Therefore, in order to predict the deformation of the high earth and rockfill dams, it is necessary to establish a constitutive model for the rockfill materials considering the particle breakage. The constitutive model based on the critical state theory, is able to consider the influences of compactness and stress state of soils, but not sufficient to reflect the influence of the particle breakage. Hence, it can not be used directly on the rockfill materials. In this study, a core problem is that the critical state of the rockfill materials is affected by particle breakage. Based on the core problem, the constitutive model and rheological model for the rockfill materials are investigated. Through static tests, the rule of the particle breaking of the rockfill materials under the critical state is found out, and the influence of the scale effect on the rule is determined. And on the basis of the static tests, the effect of the particle breakage on the critical state is revealed, and the mathematical description on the three elements of the critical state is put forward, and a constitutive model for the rockfill materials considering the influence of particle crushing is established. From rheological tests, the law of the rheological deformation of the rockfill materials is clarified, and the quantitative relationship between the rheological time and particle breakage is proposed. And on the basis of the rheological tests, a rheological model for the rockfill materials considering the influence of particle crushing is also suggested. Using the constitutive model and rheological model established in this study, the accuracy of the prediction on the deformation of high earth and rockfill dams can be improved significantly.

高土石坝的变形问题尤其是长期变形问题是至今没有很好解决的科技难题。土石坝的变形与堆石料的力学特性相关，而堆石料的力学特性受其颗粒破碎影响，因此，为了能够准确预测高土石坝的变形，需构建考虑颗粒破碎影响的堆石料本构模型。基于临界状态理论的土体本构模型能够考虑密实度和应力状态的影响，但对颗粒破碎考虑的不够，不能直接用于堆石料。本项目抓住颗粒破碎影响临界状态这一核心关键，开展考虑颗粒破碎影响的堆石料本构模型和流变模型研究。拟通过静力试验，查明堆石料在临界状态下的颗粒破碎规律，以及缩尺效应对该规律的影响；在此基础上，揭示颗粒破碎对临界状态的影响，提出临界状态三要素的数学描述，建立考虑颗粒破碎影响的堆石料本构模型。利用流变试验，弄清堆石料的流变变形规律，提出流变时间与颗粒破碎的定量关系；基于此，建立考虑颗粒破碎影响的堆石料流变模型。利用本项目建立的本构模型和流变模型，可显著提高高土石坝变形预测的精度。

堆石料颗粒破碎影响堆石料的临界状态，使得其长期变形难以准确预测。此外，缩尺效应对堆石料颗粒破碎的影响也不可忽视。鉴于此，本项目抓住颗粒破碎影响临界状态这一核心关键，开展系列试验研究和理论分析，揭示堆石料在临界状态时的颗粒破碎规律及其对临界状态的影响，量化缩尺效应对堆石料长期变形的影响，建立考虑颗粒破碎影响的堆石料长期变形本构模，以提高高土石坝变形预测的精度。取得的主要创新成果如下：.（1）针对制样、固结和三轴剪切等不同试验阶段的试样进行颗粒筛分试验，得到了各试验阶段试样的颗粒级配曲线，查明了不同试验阶段的颗粒破碎规律、围压和初始孔隙率对饱和堆石料颗粒破碎的影响，进而建立了围压与颗粒破碎率的关系、初始孔隙率与颗粒破碎率的关系。.（2）临界状态偏应力和其正应力的关系可用幂函数拟合，有效平均应力的对数与对应的孔隙比关系呈现非线性特点，不同初始孔隙率试样的临界有效正应力和临界孔隙比为两条基本相互平行的直线。基于此，提出了考虑颗粒破碎影响的饱和堆石料临界状态方程。.（3）颗粒破碎导致堆石料强度降低，并抑制剪胀性。峰值内摩擦角与相对破碎率呈幂函数减少关系，非线性内摩擦角与相对破碎率呈线性减少关系，割线模量与相对破碎率呈线性增长关系。提出了堆石料力学参数与相对颗粒破碎程度的拟合公式，可预测堆石料原位力学参数及颗粒破碎程度。.（4）揭示了压缩系数随试样尺寸、最大粒径、缩尺方法的变化规律；建立了颗粒破碎率与竖向应力、颗粒破碎率与压缩系数的关系；引入强度折减参数对侧限压缩模型进行修正，建立了反映缩尺方法、最大粒径影响的本构模型；引入折减因子，建立了湿化变形和长期变形的计算方法。.（5）提出了考虑颗粒破碎影响的剪胀方程，能够同时描述应变硬化和应变软化时的剪胀特性。揭示了堆石料总输入能与剪应变成正比的规律，推导了临界状态剪应力、塑性势函数，建立了考虑堆石料颗粒破碎的临界状态弹塑性本构模型。