Damage evolution and failure warning in early-age flexible-formwork concrete for underground support

Geohazard Mechanics Pub Date : 2025-09-01 DOI:10.1016/j.ghm.2025.08.007

Zijun Han , Hongtao Liu , Xiaofei Guo , Jialu Liang , Zhongjin Qiao , Chenxiao Cao , Lei Guo , Xiaogang Chen

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Abstract

The evolution law of mechanical properties and damage characteristics of early-age flexible formwork filling concrete have a decisive influence on the stability control of surrounding rock of large deformation roadway. This study obtained the mechanical evolution characteristics of flexible formwork concrete filling body by using the standard ratio of engineering site and laboratory system test, clarified the time-space coupling mechanism of acoustic emission characteristic parameters and stress field evolution in the process of damage accumulation, and established a multi-parameter damage constitutive model of early-age concrete considering aging characteristics in combining with the theory of damage mechanics. The results show that: (1) Under the same curing age, the compressive strength of the filling body is significantly negatively correlated with the water-cement ratio, and the correlation decreases with the increase of the curing age, showing obvious strain softening behavior in the post-peak stage; (2) During the loading process, the concrete filling body presents a typical’ three-stage’ acoustic emission response characteristics, that is, the rising period of the initial micro-fracture accumulation, the active period of the main fracture development and the attenuation period after the failure; (3) At a certain curing age, with the increase of water-cement ratio, the total number of acoustic emission b-value signal points generated by the specimen during the test gradually decreases, and the b-value curve changes, and the minimum value appears near the peak stress point; and (4) The pre-peak and post-peak complete damage constitutive equations are established, which can accurately predict the mechanical response of concrete backfill under different curing times and water-cement ratios. The research results provide a basis for selecting the support time and support parameters for large deformation roadway.

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早期地下支护柔性模板混凝土损伤演化及失效预警

早期柔性模板填充混凝土力学性能演化规律及损伤特征对大变形巷道围岩稳定性控制具有决定性影响。本研究采用工程现场标准比和实验室系统试验，获得了柔性模板混凝土充填体的力学演化特征，阐明了损伤积累过程中声发射特征参数与应力场演化的时空耦合机制；并结合损伤力学理论，建立了考虑老化特征的早期混凝土多参数损伤本构模型。结果表明：(1)在相同养护龄期下，充填体抗压强度与水灰比呈显著负相关，且随养护龄期的增加相关性降低，峰后阶段表现出明显的应变软化行为；(2)在加载过程中，混凝土充填体呈现典型的“三阶段”声发射响应特征，即初始微裂缝聚集的上升期、主裂缝发育的活跃期和破坏后的衰减期；(3)在一定养护龄期，随着水灰比的增大，试件在试验过程中产生的声发射b值信号点总数逐渐减少，b值曲线发生变化，最小值出现在峰值应力点附近；(4)建立峰前和峰后完全损伤本构方程，可以准确预测不同养护时间和水灰比下混凝土充填体的力学响应。研究结果为大变形巷道支护时间和支护参数的选择提供了依据。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Geohazard Mechanics

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