Key Takeaways & Executive Findings
- •• Fracture toughness and fracture energy of rock-concrete interfaces decrease with increasing temperature across different lithologies, with sandstone-concrete interface most affected. • At elevated temperatures, fracture parameters become less sensitive to interface strength factor, indicating thermal effects dominate failure. • Fracture process zone length increases linearly with temperature, signifying a brittle-to-ductile transition. • Findings provide critical insights for designing and ensuring safety of deep underground structures under thermo-mechanical coupling.
Abstract
Studying the fracture behavior of rock-concrete interface (RCI) of various lithologies under temperature and loading is crucial for the safety of structural systems involving these interfaces. In this study, the implications of temperature and interface strength factor (ISF) on the fracture mechanics of rock-concrete composite specimens with varying lithologies were studied using three-point bending numerical experiments with rock-concrete bi-material (RCB) notched semi-circular bending (NSCB) specimens. The findings indicate that the fracture toughness (KIC) and fracture energy (Gf) of RCI with various lithologies are negatively correlated with temperature, and SCI is most significantly affected by temperature. Meanwhile, at higher temperatures, the KIC and Gf of RCI exhibited lower sensitivity to the ISF, indicating that the failure of the specimen was driven by thermal effects. Furthermore, the length of the fracture process zone (rc) of the RCB specimens of varying lithologies exhibited a linear increasing trend with increasing temperature. This phenomenon indicates a transition from brittle to ductile materials. This study provides critical insights for ensuring the long-term safety and enhancing the disaster resilience of major infrastructure in extreme environments.
1. Introduction
In deep underground engineering (such as nuclear waste disposal reservoirs [1], geothermal reservoir development [2], and deep tunnels [3]), the mechanical characteristics of rock-concrete interface (RCI) structures are the core factors determining the long-term stability of the project. However, as the transition zone of heterogeneous materials, the fracture mechanical response of the interface is affected by lithological differences, temperature changes, load distribution, and micro-scale structural evolution. Especially in the thermal-mechanical coupling environment, the interface debonding and slippage inflicted by the difference in thermal expansion coefficient, mineral phase transformation and fracture propagation between rock and concrete seriously threaten the integrity of the structure [4−7]. Hence, a systematic investigation of the thermal damage mechanisms and mechanical responses of RCI with varying lithologies is essential. Such research is pivotal for developing predictive models and durable design strategies for deep engineering structures subjected to thermo-mechanical coupling.
In the past, numerous scholars have researched the mechanical characteristics and failure properties of rock or concrete under temperature or load. For example, ZUO et al [8] and ZHU et al [9] investigated the cracking behavior and mechanical properties of rocks under the influence of heat, and they pointed out that after the temperature reaches a certain level, thermal cracking increases sharply with the increase of temperature, and the mechanical properties decrease linearly with the increase of temperature. ZHANG et al [10] investigated the evolution trend of granite fault characteristics. They noted that the failure patterns of granite become more complex under THM-coupling factors. GUO et al [11] and ZHOU et al [12] studied the genesis and distribution of intergranular cracks after heat treatment, and pointed out that high temperature will promote the development of microcracks and change the crack morphology in the rock. ZHAO et al [13] noted that the compressive strength of prefabricated cracked concrete specimens increased at 300 ℃ and under subsequent air-cooled conditions, and the brittleness was obvious. CUI et al [14] found that the Gf of shotcrete increased first and then decreased with the increase of temperature (peaking at 60 ℃), and the initial KIC was negatively correlated with the instability KIC and temperature, and the fracture process length also increased first and then decreased.
Recently, considerable attention has been paid to the mechanical characteristics and failure modes of RCI, particularly the eff...
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LU Jian-you, CHEN Xiao-nan, ZHOU Zi-long, CHANG Xu (2026). Fracture response characteristics on model I of rock-concrete interface with different lithologies after heat treatment. Journal of Central South University. https://doi.org/10.1007/s11771-026-6239-9
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Frequently Asked Questions
What is the effect of temperature on fracture toughness of rock-concrete interfaces?
The study found that fracture toughness (KIC) of rock-concrete interfaces decreases with increasing temperature across different lithologies, with the sandstone-concrete interface being most significantly affected.
How does interface strength factor influence fracture behavior at high temperatures?
At higher temperatures, fracture toughness and fracture energy become less sensitive to the interface strength factor, indicating that thermal effects dominate the failure process.
What is the significance of fracture process zone length in this study?
The fracture process zone length increases linearly with temperature, indicating a transition from brittle to ductile behavior in the rock-concrete interface.
What are the practical implications of this research?
The findings provide critical insights for ensuring long-term safety and enhancing disaster resilience of major infrastructure, such as deep tunnels and nuclear waste repositories, under extreme thermal-mechanical conditions.
What method was used to study the fracture behavior?
Three-point bending numerical experiments were conducted using rock-concrete bi-material notched semi-circular bending (NSCB) specimens.
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