The freezing method is an effective approach for constructing coal mine shafts through water-rich soft rock strata. The frozen wall produced by this technique stops the movement of water and offers temporary support, ensuring the safety and stability of the shaft working face. However, most frozen rock masses generally comprise ice-filled flaws and frozen intact rock. A frozen fissured rock mass undergoing the long-term effects of excavation unloading under in situ stress gradually accumulates damage or creep deformation over time; this damage is mainly responsible for the significant deformation, cracking and even instability of the frozen rock wall. To study the creep characteristics of ice-filled fissured rock masses under unloading conditions, a series of conventional triaxial compression tests and triaxial unloading creep tests were performed on ice-filled flawed red sandstone specimens from the Shilawusu mine in Northwest China using a self-developed DRTS-500 subzero rock triaxial testing system. In conjunction with the experimental data, the instantaneous strength and deformation characteristics of the rock specimens were analyzed, and their creep deformation characteristics and damage evolution characteristics were discussed. In this paper, based on the nonlinear creep characteristics of frozen rock, fractional calculus theory and damage theory, a new nonlinear creep damage model of frozen fissured red sandstone was defined in series with the improved Burgers model and elastoplastic damage model. The proposed creep model can reasonably describe the creep deformation of frozen fissured red sandstone. Classical elastoplastic mechanics and creep theory were used to derive the three-dimensional creep damage constitutive equation, and the results of creep experiments and simulation results of the creep damage constitutive model were very consistent in this study. The new creep model not only reflects the whole creep deformation process of frozen fissured red sandstone but also exhibits better performance than the classical Burger model and improved Nishihara model in describing the primary creep stage and accelerating creep stage. Therefore, the proposed nonlinear creep damage model is suitable for studying the mechanical creep properties of frozen fissured rock under unloading conditions. The results can provide an important reference for the long-term stability assessment of frozen rock walls of coal mine shafts.

中文翻译：

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含单一充冰缺陷红砂岩三轴卸载蠕变力学特性及损伤本构模型研究

冻结法是一种通过富水软岩地层建设煤矿竖井的有效方法。该技术产生的冻结壁阻止了水的运动并提供了临时支撑，确保了竖井工作面的安全和稳定。然而，大多数冻结岩体通常包括充满冰的裂缝和冻结的完整岩石。冻结裂隙岩体在地应力下长期经受开挖卸载的作用，随着时间的推移逐渐积累损伤或蠕变变形；这种破坏是造成冻结岩壁显着变形、开裂甚至失稳的主要原因。为研究卸载条件下充冰裂隙岩体的蠕变特性，使用自主研发的DRTS-500零下岩石三轴试验系统，对西北石拉乌苏矿含冰裂纹红砂岩试样进行了一系列常规三轴压缩试验和三轴卸载蠕变试验。结合试验数据，分析了岩石试样的瞬时强度和变形特性，讨论了其蠕变变形特性和损伤演化特性。本文基于冻结岩石的非线性蠕变特性、分数阶微积分理论和损伤理论，结合改进的Burgers模型和弹塑性损伤模型，定义了一种新的冻结裂隙红砂岩非线性蠕变损伤模型。所提出的蠕变模型可以合理地描述冻裂红砂岩的蠕变变形。采用经典弹塑性力学和蠕变理论推导出三维蠕变损伤本构方程，本研究中蠕变实验结果与蠕变损伤本构模型模拟结果非常吻合。新的蠕变模型不仅反映了冻裂红砂岩的蠕变变形全过程，而且在描述初级蠕变阶段和加速蠕变阶段方面比经典 Burger 模型和改进的 Nishihara 模型具有更好的性能。因此，所提出的非线性蠕变损伤模型适用于研究冻结裂隙岩石在卸载条件下的力学蠕变特性。