堆石料剪切过程中的颗粒破碎研究

颗粒破碎直接改变堆石料本身结构,影响土体的剪胀、内摩擦角、峰值强度、渗透系数和流变变形。但是,目前对于堆石料在剪切过程中的破碎规律尚不明确。通过室内固结排水三轴试验,研究了古水面板坝玄武岩堆石料在制样、固结和剪切过程中的颗粒破碎规律。研究结果表明:堆石料在制样过程中会产生较为显著的颗粒破碎现象;在等向固结过程几乎不产生颗粒破碎。低围压下,颗粒间的翻越和滑移受围压约束较弱,剪切过程中的颗粒破碎不明显。髙围压下,颗粒间的翻越和滑移受到限制,颗粒间的咬合力显著提高,随着剪切应变的增大,土体颗粒不断发生破碎。在颗粒破碎过程中,大粒径颗粒首先破碎,破碎的颗粒从大粒径逐渐向小粒径扩展。粒径在0.5 mm以下颗粒的含量始终随剪应变的增大而增多,且增长幅度随着围压的增大而增大。土体颗粒破碎同时受围压和剪切变形的影响,相同围压下剪切过程中的相对破碎参量Br和剪应变之间的关系可采用双曲线公式描述。

Particle breakage of rockfill during triaxial tests

The particle breakage directly modifies the structure of the rockfill, influencing its dilatancy, friction angle, strength, permeability and creep deformation. However, the breakage law of the rockfill during shearing is still unclear. The particle breakage of the basalt rockfill of Gushui concrete face rockfill dam during the sample preparation, consolidation and drained triaxial shearing is studied by using the consolidated-drained triaxial tests. The research shows that the sample preparation of the rockfill generates notable particle breakage. The isotropic consolidation of the sample generates little particle breakage. Under low confining pressure, the particles can freely roll over and slide, and there is little particle breakage during the shearing. Under high confining pressure, the rolling and sliding of the particles are limited, which increases the interlocked force among the particles. And the particle breakage increases with shear strain. During the particle breakage, the large particles break first. The diameter of the broken particle decreases with the increasing confining pressure. The content of the particle less than 0.5 mm always increases with the increasing pressure and the amplification also increases with the increasing confining pressure. Under high confining pressure, the stress and shear strain both influence particle breakage. The relationship between the relative breakage parameter Br and the shear strain under the same confining pressure can be described by hyperbolic formula.