Abstract Due to the wide existence of tensile stresses in cemented paste backfill (CPB) mode-I fracture toughness (KIC) plays a crucial role in the mechanical stability of CPB under complex field loading conditions. However, the studies on KIC of CPB materials and associated influential factors are very limited. Hence, the main objective of this study is to experimentally investigate the effects of curing time (3, 7, 28, and 90 days), cement content (2%, 4.5%, and 7%) and saturation state (unsaturated and saturated states) on the evolution of KIC through single-edge-notch bending tests on CPB specimens. The obtained results show that KIC displays a strongly time-dependent and nonlinear evolution with curing time, especially during the early age. Moreover, the development of KIC is sensitive to changes in cement content, which can be attributed to the precipitation of cement hydration products as well as the self-densification process in CPB. In addition, through the vacuum-based rapid re-saturation approach proposed in this study, it has been concluded that the re-saturated CPB has a lower KIC compared with the CPB without re-saturation treatment and thus confirm the dependence of KIC on the saturation state.

中文翻译：

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固化时间、水泥含量和饱和状态对水泥浆充填体I型断裂韧性的影响

摘要 由于水泥浆充填体（CPB）I 型断裂韧性（KIC）中广泛存在拉应力，在复杂的现场加载条件下对CPB 的机械稳定性起着至关重要的作用。然而，关于CPB材料的KIC及其影响因素的研究非常有限。因此，本研究的主要目的是通过实验研究养护时间（3、7、28 和 90 天）、水泥含量（2%、4.5% 和 7%）和饱和状态（不饱和和饱和状态）的影响) 通过对 CPB 试样进行单边缺口弯曲试验，了解 KIC 的演变。获得的结果表明，KIC 表现出强烈的时间依赖性和非线性随固化时间的演变，尤其是在早期。此外，KIC 的发展对水泥含量的变化很敏感，这可以归因于水泥水化产物的沉淀以及 CPB 中的自致密化过程。此外，通过本研究中提出的基于真空的快速再饱和方法，得出的结论是，再饱和的 CPB 与未经再饱和处理的 CPB 相比具有更低的 KIC，从而证实了 KIC 对饱和状态。