基于颗粒破碎的堆石料长期变形特性与分数阶弹粘塑性模型研究

In recent years, much more attention has been paid to the safety of dams. However, studies on the long-term deformation mechanism of high earth rockfill dams and prediction method of dam deformation cannot meet the demand of practical engineering. The accuracy of deformation prediction is quite unsatisfactory. The particle breakage of coarse-grained soil (such as rockfill) is an important factor affecting the long-term deformation of earth rockfill dam. Hence, it is necessary to study and establish new constitutive model which can capture the long-term deformation of earth dams reasonably. In this project, large-scale triaxial tests will be conducted to investigate the potential factors affecting particle breakage of coarse-grained materials. The influence of rock strength, particle size distribution and stress state on the particle breakage will be studied. A relationship among particle breakage, rock strength, particle size distribution and stress state will be proposed. By conducting particle breakage and CT tests, expression method of particle damage degree from single grade to full grades will be built. By conducting long-term one-dimensional compression and CT tests (i.e., the longest time is no less than one year) on dry and saturated coarse-grained soils, the long-term deformation under dry, wetting softening and high pressure conditions and evolution law of particle deterioration will be studied. The relationship between meso-structural change and macro mechanical properties will be established to reveal the long-term deformation mechanism. Fractional elastic visco-plastic rheological model for coarse-grained soil will be established to predict the long-term deformation of earth rockfill dams more accurately.

大坝安全已提到前所未有的关注程度。尽管我国大坝设计水平据世界领先水平，但对高土石坝长期变形机理及预测方法的研究跟不上实际工程的需求，变形预测精度很不令人满意。堆石料等粗颗粒土的颗粒破碎是土石坝长期变形的重要因素，因此，对此进行深入研究并建立能合理反映其长期变形特性的新型本构模型十分必要。本项目拟通过大型三轴试验，研究颗粒破碎影响因素，揭示岩石强度、级配及应力状态对颗粒破碎的影响规律，提出颗粒破碎与各因素间的定量表述方法；开展颗粒破碎和CT试验，建立从单粒组颗粒到全级配颗粒损伤度的表述方法；进行粗颗粒土干样及饱和样超长期（最长时间不小于1年）高压下侧壁透视单向压缩流变试验、CT试验等，研究风干、浸水软化及高应力下粗颗粒土长期变形及颗粒劣化破碎演化规律；寻找细观结构变化与粗颗粒土宏观力学性质间的联系，揭示堆石料长期变形机理；建立粗颗粒土分数阶弹粘塑流变模型，实现更准确预测土石坝长期变形的目标。

土石坝长期变形的准确预测是困扰工程界及学术界多年的难题，随着坝工技术的发展，坝高达到300m级，这个问题尤为突出，急需解决。本项目针对堆石料等粗颗粒土，采用宏细观试验研究、理论分析、数值模拟等多种手段，深入研究了粗颗粒土的长期变形机理，建立了合理的本构模型，为土石坝长期变形准确计算提供了基础。主要研究内容及成果包括：.（1）深入研究了颗粒破碎的影响因素，进行了大量的大型三轴固结排水剪试验，研究风干、浸水软化及高应力下粗颗粒土长期变形及颗粒劣化破碎演化规律；开展了不同母岩性质粗颗粒土（包括多种强度的人工模拟粗颗粒土）三轴剪切试验三轴试验，研究不同岩石强度和围压下粗颗粒土的破碎规律，建立岩石强度、围压与颗粒破碎间的关系；.（2）开展了不同初始级配的粗颗粒土三轴剪切试验，研究初始级配曲线对粗颗粒土颗粒破碎的影响。对试验前后试样进行颗粒分析，揭示不同颗粒直径对颗粒破碎的影响，建立粗颗粒土直径与颗粒破碎率之间的定量描述；.（3）进行了大量不同岩性、不同级配粗颗粒土的单向压缩长期及超长期流变试验，揭示了粗颗粒土的长期变形特性；进行了高压条件下单粒组粗颗粒土侧壁透视单向压缩流变试验，监测颗粒位移重分布与土体变形，研究颗粒位移与变形演化规律；.（4）进行了大量不同岩性粗颗粒土的平板压缩颗粒破碎试验；进行了粗颗粒土颗粒压缩破碎CT扫描试验，分析了颗粒尺寸与微裂纹关系，从而揭示了颗粒强度尺寸效应的机理； .（5）基于试验结果，寻找细观结构变化与粗颗粒土宏观力学性质间的联系，揭示堆石料长期变形机理；研究了长时间高应力及浸水条件下粗颗粒土强度性质演化规律，变形性质演化规律，颗粒破碎演化规律（宏观试样尺度）；建立了强度演化方程。.（6）提出了适合粗颗粒土的剪胀方程、蠕变方程，建立了考虑颗粒破碎等效应的粗颗粒土分数阶弹粘塑流变本构模型，并进行了试验验证，从而可更准确预测土石坝长期变形。