混凝土中裂纹起裂和损伤演化的离散元模拟

doi:10.12382/bgxb.2025.0111

摘要/Abstract

摘要： 为研究混凝土中损伤演化过程,采用离散元方法对不同加载模式下含预制裂纹混凝土试件的裂纹起裂和扩展演化过程进行数值模拟。基于混凝土材料中骨料几何特征,构建了具有不规则多面体骨料的三维混凝土离散元模型;并采用平节理模型对4种加载模式下的混凝土试件中裂纹产生和扩展行为进行研究,揭示了混凝土宏观失效破坏的细观损伤机理。结果表明:1) 加载初期,混凝土试件内部裂纹较少,由于压缩应力集中效应影响,剪切裂纹主要聚集在加载端两侧,而预制裂纹尖端则产生拉伸裂纹;加载后期,裂纹沿着骨料边界迅速扩展导致裂纹弯折扩展,加载端附近产生次生裂纹并向试件中部延伸,同时承载高应力的骨料内部出现少量裂纹。2) 加载角从0°增至28°时,预制裂纹尖端处的剪切裂纹占比呈现增加的趋势,体现了混凝土从拉伸破坏到剪切破坏的转变;4种加载模式下拉伸破坏仍是主导混凝土试件破坏的主要因素。3) 加载角度在0°~28°范围内,预制裂纹尖端处的起裂角随加载角增大而增大;采用广义最大切应力准则预测结果在纯Ⅰ型及Ⅰ-Ⅱ混合加载阶段与模拟结果吻合性较好,在纯Ⅱ型加载下预测结果偏高。

关键词: 混凝土, 离散元模型, 起裂角, 广义最大切应力准则

Abstract:

To investigate the damage evolution process in concrete, numerical simulations were conducted using the Discrete Element Method(DEM) to study crack initiation and propagation evolution in pre-cracked concrete specimens under different loading modes. Based on the aggregate geometry in concrete materials, a three-dimensional discrete element model incorporating irregular polyhedral aggregates was developed. The flat-joint model was then employed to investigate crack initiation and propagation behavior in concrete specimens under four loading modes, revealing the meso-scale damage mechanisms underlying macroscopic failure in concrete. The results demonstrate that: (1) During the initial loading phase, fewer internal cracks were observed in the concrete specimen. Due to the compressive stress concentration effect, shear cracks predominantly clustered near both loading ends, while tensile cracks initiated at the pre-existing crack tip. In the later loading stage, cracks rapidly propagated along aggregate boundaries, resulting in crack deflection. Secondary cracks emerged adjacent to the loading ends and extended towards the specimen mid-section, accompanied by limited crack development within highly stressed aggregates. (2) As the loading angle increased from 0° to 28°, the proportion of shear cracks at the pre-existing crack tip exhibited an increasing trend, demonstrating the transition from tensile-dominated to shear-dominated failure mechanisms in concrete. However, tensile failure remained the predominant factor governing specimen failure across all four loading modes. (3) Within the loading angle range of 0°-28°, the crack initiation angle at the pre-existing crack tip exhibited a positive correlation with increasing loading angles. The predictions based on the generalized maximum tangential stress (GMTS) criterion showed good agreement with simulation results for pure Mode I and mixed Mode Ⅰ-Ⅱ loading conditions, while demonstrating higher predictions under pure Mode Ⅱ loading.

Key words: concrete, discrete element model, crack initiation angle, generalized maximum tangential stress criterion

檀日晶, 任会兰, 李涛. 混凝土中裂纹起裂和损伤演化的离散元模拟[J]. 兵工学报, 2025, 46(10): 250111-.

TAN Rijing, REN Huilan, LI Tao. Discrete Element Simulation if Crack Initiation and Damage Evolution in Concrete[J]. Acta Armamentarii, 2025, 46(10): 250111-.

图/表 25

图1 粗骨料几何模型

Fig.1 Geometry model of a coarse aggregate

图2 刚性簇模型图

Fig.2 Illustration of clump model

图3 混凝土离散元模型建模流程图

Fig.3 Flow chart of concrete model construction

图4 混凝土试件中粗骨料模型

Fig.4 Illustration of coarse aggregate inside concrete

图5 混凝土内部骨料颗粒范围

Fig.5 Aggregate particle range inside concrete

图6 混凝土离散元模型

Fig.6 Three-dimensional discrete element model of concrete

图7 平节理模型

Fig.7 Flat-joint contact model

图8 接触模型中的三组接触

Fig.8 Three groups of contacts in the numerical simulation

图9 单轴压缩应力-应变曲线

Fig.9 Stress-strain curves in the uniaxial compressive test

图10 巴西劈裂破坏的力-位移曲线

Fig.10 Force displacement curves in the Brazilian test

表1 平节理模型细观参数

Table 1 Parameters of Flat-Joint Model contacts

参数	水泥砂浆	骨料	ITZ
弹性模量E_c/GPa	2	4	1.2
抗拉强度σ_t/MPa	8.5	20	5.1
粘结强度c/MPa	13.5	35	8.1

图11 含预制裂纹混凝土试件试验与仿真结果

Fig.11 Comparison between experimental results and simulation results

图12 0°加载下数值模型及力位移曲线

Fig.12 Simulation model and force displacement curve under 0° loading

图13 裂纹演化

Fig.13 Evolution process of microcracks

图14 受力分布

Fig.14 Force distribution

图15 试件横截面

Fig.15 Cross section of specimen

图16 微裂纹在砂浆和ITZ中的分布图

Fig.16 Illustration of microcracks in mortar and ITZ

图17 阶段三中裂纹分布

Fig.17 Illustration of microcracks in stage 3

图18 三种加载角度下的裂纹扩展过程

Fig.18 The crack propagation process under three loading angles

图19 不同加载阶段拉伸裂纹和剪切裂纹

Fig.19 The change of proportion of tensile cracks and shear cracks at different loading stage

图20 试件起裂角示意图

Fig.20 Illustration of crack initiation angle

图21 3种模型内部骨料内剖图

Fig.21 Internal profile of aggregate distribution in three models

图22 4种加载模式下力-位移曲线

Fig.22 Force displacement curve under four loading modes

表2 试验和数值计算的峰值载荷

Table 2 Comparison of experimental and numerical peak loads

模型	0°	10°	18°	28°
试验/kN	15.7	16.3	15.9	13.6
模型1/kN	16.4	15.1	14.3	12.8
模型2/kN	15.3	14.6	13.5	12.1
模型3/kN	15.5	15.0	13.8	12.0
均值/kN	15.7	14.9	13.8	12.3
误差/%	0	9.3	13.2	9.5

表3 理论预测、试验结果和数值计算起裂角对比

Table 3 Comparison of theoretical, experimental and numerical fracture initiation angles

项目	0°	10°	18°	28°
GMTS/(°)	0	16.9	33.7	59
试验/(°)	4.4	17.4	29.2	49.1
模型1/(°)	1.0	18.5	28.5	51.0
模型2/(°)	0.6	17.9	28.3	49.0
模型3/(°)	1.3	17.4	33.2	52.3
均值/(°)	1.0	17.9	30.0	50.8
误差1/%		5.9	10	13.9
误差2/%		2.8	2.6	1.7

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