基于细观层次的轻骨料混凝土压缩破坏及端面效应数值模拟

Meso-scale Numerical Simulation of Compression Failure and End Effect of Lightweight Aggregate Concrete

为探索轻骨料混凝土力学性能及破坏规律,采用细观数值模拟方法,将轻骨料混凝土看作由球形轻骨料颗粒与砂浆基质组成的两相非均质复合材料,建立三维随机骨料模型,模拟轻骨料混凝土单轴抗压破坏过程,研究分析加载端面约束效应对其裂纹扩展及材料力学性能的影响。研究结果表明:(1)与普通混凝土相比,轻骨料混凝土压缩破坏时,裂纹最先发生在轻骨料处,且裂纹会直接贯穿轻骨料进行延伸;(2)加载端面无约束试件最终形成轴向劈裂破坏,有约束试件最终形成倒锥形破坏;(3)加载端面无约束试件的抗压强度与峰值应变相对于有约束试件分别降低了29.6%、45.5%。该模型及模拟结果为传统宏观试验的不足提供了有效补充。

The aim of this research is to explore the mechanical properties and failure law of lightweight aggregate concrete. Lightweight aggregate concrete is regarded as a two-phase heterogeneous composite composed of spherical lightweight aggregate particles and mortar matrix. A three-dimensional random aggregate model is established using mesoscopic numerical simulation method to simulate the uniaxial compressive failure process of lightweight aggregate concrete. The influences of constraint effect of loading end face on crack propagation and material’s mechanical properties are studied and analyzed. Results demonstrate that 1) compared with ordinary concrete, lightweight aggregate concrete sees the first crack at lightweight aggregate during compression failure, and the crack extends directly through the lightweight aggregate;2) specimens with unrestrained loaded end face finally witness axial splitting failure, and those with restrained loaded end face undergo inverted cone failure;3) compared with the constrained specimens, the unconstrained specimens see reductions of compressive strength and peak strain by 29.6% and 45.5%, respectively. The proposed model and simulation results provide an effective supplement to the shortcomings of traditional macro-level tests.