考虑骨料尺寸的混凝土岩石边界效应断裂模型

发布时间：2018-04-02 21:32

本文选题：准脆性断裂　切入点：骨料粒径　出处：《工程力学》2017年12期

【摘要】：该文比较了边界效应模型(BEM)和尺寸效应模型(SEM)在研究材料断裂性能方面的不同。提出了由处于准脆性断裂状态的三点弯曲试件的峰值荷载P_(max),同时确定材料参数——断裂韧度K_(IC)与拉伸强度f_t的理论与方法。由于实验室条件下混凝土试件高度W与骨料最大粒径d_(max)的比例W/d_(max)约为5~20,试件的非均质性明显,破坏为准脆性断裂控制。因此,区别于以连续介质力学为基础的应用于准脆性断裂研究的力学模型,该文研究将骨料最大粒径d_(max)引入相应的断裂模型解析表达式中,由参数组合β·d_(max)来计算结构峰值状态对应的裂缝扩展量,通过离散参数β的不同取值,实现了对材料参数——断裂韧度与拉伸强度的准确预测。基于不同学者的相同尺寸W而不同初始裂缝长度α_0,以及相同初始缝高比α_0/W而不同尺寸W的几何相似的砂浆、混凝土及岩石类材料试件的试验成果(骨料最大粒径d_(max)从1.2 mm~40 mm变化),验证了所提理论与方法的合理性。
[Abstract]:In this paper, the boundary effect model (BEMM) and the size effect model (SEM) are compared in studying the fracture properties of materials.The theory and method of determining the material parameter, fracture toughness (K / C) and tensile strength (ft) by the peak load of three point bending specimens in quasi brittle fracture state are presented in this paper.Under laboratory conditions, the ratio W / D _ (max) of concrete specimen height to the maximum aggregate size D _ (max) is about 5 ~ 20, the heterogeneity of the specimen is obvious, and the failure is controlled by quasi-brittle fracture.Therefore, different from the mechanical model applied to quasi-brittle fracture research based on continuum mechanics, this paper studies the introduction of maximum aggregate particle size d _ max) into the corresponding analytical expression of fracture model.The crack propagation corresponding to the peak state of the structure is calculated by the parameter combination 尾 _ DX _ max, and the accurate prediction of the material parameter -fracture toughness and tensile strength is realized by taking different values of the discrete parameter 尾.Based on the same size W of different scholars and different initial crack length 伪 _ 0, as well as the same initial joint height ratio of a _ 0 / W, and the geometric similarity of different sizes of W,The experimental results of concrete and rock material samples (maximum aggregate size d _ (max)) vary from 1. 2 mm~40 mm to 1. 2 mm~40 mm, which verifies the rationality of the proposed theory and method.
【作者单位】：华北水利水电大学土木与交通学院;西澳大学机械与化学学院;北京科技大学材料科学与工程学院;
【基金】：国家自然科学基金项目(51779095,51679092) 澳大利亚国家基金项目(DP0346198) 郑州市科技攻关项目(153PKJGG111) 河南省高等学校青年骨干教师资助计划项目(2013GGJS-084)
【分类号】：TU528

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