Tunnels and shaft mining roadways are often subjected to varying degrees of asymmetric loading due to terrain relief or project excavation. In order to analyze the influence of the asymmetric degree of loading on the mechanical properties and damage rupture law of coal rock, uniaxial compression tests of coal rock under four asymmetric loading modes were carried out, the influence of the asymmetric coefficients of loading on macro- and micromechanical properties of coal and rock was analyzed, and a statistical damage constitutive model of coal and rock was established to reflect the asymmetric loading degree. The results of the study show that the peak stress of the coal rock decreases gradually with the increase in the asymmetric coefficient of loading, and the two are linear functions of each other. The distribution of the acoustic emission ringing count peak value is concentrated under uniform loading, while the acoustic emission ringing count rate presents a multipeak phenomenon under asymmetric loading, and the peak value points are scattered. In the case of asymmetric loading, the stress concentration on the edge of the upper loading plate leads to shear failure, and the microscopic cracks are concentrated near the interface between the loading zone and the nonloading zone. According to the established damage constitutive model, when the damage degree is the same, the larger the asymmetric coefficient, the smaller the strain value, which indicates that the asymmetric loading promotes the damage of coal and rock.

中文翻译：

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非对称加载下煤岩损伤演化特征及本构模型

由于地形起伏或工程开挖，隧道和竖井采矿巷道经常受到不同程度的不对称荷载。为了分析不对称加载程度对煤岩力学性能和损伤破裂规律的影响，开展了四种不对称加载模式下煤岩的单轴压缩试验，研究了不对称加载系数对煤岩宏观力学性能的影响。对煤岩微观力学特性进行分析，建立反映非对称加载程度的煤岩统计损伤本构模型。研究结果表明，随着加载不对称系数的增加，煤岩峰值应力逐渐减小，且两者互为线性函数。均匀加载下声发射振铃计数峰值分布集中，而非对称加载下声发射振铃计数率呈现多峰现象，且峰值点分散。在非对称加载情况下，上加载板边缘应力集中导致剪切破坏，微观裂纹集中在加载区与非加载区界面附近。根据建立的损伤本构模型，当损伤程度相同时，不对称系数越大，应变值越小，说明不对称加载促进了煤岩的损伤。