榆神矿区是我国重要的煤炭生产基地之一，许多千万吨级的现代化煤矿急需建设，人工冻结法是富水洛河组地层煤矿斜井施工的重要方法之一，开展西部冻结斜井井筒解冻后双裂隙类砂岩蠕变损伤破坏机理试验与理论研究对人工冻结斜井井筒解冻后的长期稳定性评价及煤矿安全生产具有重要意义。本文以榆神矿区四期某煤矿冻结斜井工程为依托，将洛河组砂岩作为原岩，利用相似材料制备的双裂隙类砂岩作为研究对象，采用室内试验与理论分析相结合的方法对双裂隙类砂岩解冻后三轴压缩试验下变形与破坏特征、解冻后双裂隙类砂岩蠕变力学特性进行研究，主要工作和结论是：

（1）基于研究得到合理的相似配比，使用相似材料制作含有不同预制裂隙倾角的双裂隙类砂岩，完成了双裂隙类砂岩在不同冻结温度下的冻结-解冻试验。随着裂隙倾角的增大解冻后冻胀力对试件造成的局部化损伤效应逐渐减弱；随着冻结温度的降低，类砂岩岩样的损伤程度增大，在岩样预制裂隙边缘及端部区域剥落量逐渐增加，并且在预制裂隙尖端由初始损伤萌生的次生裂纹数量及贯通程度均有不同程度的增加。

（2）完成了不同冻结温度时双裂隙类砂岩解冻后三轴压缩试验。随着围压增加，双裂隙类砂岩的力学性能不断提高，破坏模式由劈裂破坏逐渐向沿着预制裂隙进行扩展的剪切滑移破坏过渡，双裂隙类砂岩次生主裂纹周围颗粒破碎情况有所减少，说明随着围压的逐渐增加，双裂隙类砂岩塑性增加。随着裂隙倾角的增加，双裂隙类砂岩的力学性能先降低后增大，变化趋势整体呈“U”型，在裂隙倾角为30^°时力学性能最弱。随着冻结温度的降低，不同裂隙倾角类裂隙砂岩解冻后力学性能随之降低，破坏后沿预制裂隙边缘处的次生裂纹数量增加。

（3）完成了不同冻结温度下不同裂隙倾角双裂隙类砂岩解冻后分级加载三轴压缩蠕变试验。随着裂隙倾角的逐渐增加总蠕变量先增大后减小，裂隙倾角为30^°时蠕变速率变化最快。随着冻结温度的降低，造成岩样初始损伤增加，导致各级蠕变应力水平下轴向蠕变量及蠕变速率相应增加。随着荷载等级的不断提高，砂岩进入稳定蠕变阶段所经历的时间越长，粘滞性越明显。双裂隙类砂岩岩样的蠕变破坏模式与三轴压缩条件下的破坏模式基本相同。随着冻结温度的降低，不同裂隙倾角类裂隙砂岩次生裂纹越来越多，损伤破坏程度越来越大。

（4）通过对原状双裂隙类砂岩、解冻后类裂隙砂岩及解冻后类裂隙砂岩三轴压缩蠕变破坏后三种状态核磁共振试验，分析了三种状态下类裂隙砂岩孔隙结构随裂隙倾角及冻结温度等因素的变化规律。结果表明，含有不同裂隙倾角的双裂隙类砂岩在冻结-解冻试验后，T₂谱的分布均出现一定程度的向右移动，信号幅度均有所增强，冻结前后类砂岩的孔隙半径主要集中在之间，占总比例的98%以上，其余孔径孔隙的占比不到2%。蠕变破坏后的双裂隙类砂岩T₂谱向右移动的明显，第一峰的占比有所降低，第二、三峰的占比升高，并且出现了新的第四峰。裂隙倾角为30^°时类砂岩在长期荷载作用下宏观蠕变力学性能的总蠕变量及加速阶段蠕变速率最大，对应破坏后谱面积也最大。

（5）基于岩石蠕变损伤力学理论，通过引入非线性粘塑性体及时效劣化因子来改进Burgers蠕变模型，构成考虑原生节理影响的非线性蠕变模型。根据三轴分级加载蠕变试验数据对蠕变模型进行拟合验证，拟合结果与试验数据基本吻合。

Yushen mining area is one of the important coal production bases in China. Many modern coal mines are in urgent need of construction. Artificial freezing method is one of the important methods for inclined shaft construction in Luohe formation. It is of great significance to carry out the experimental and theoretical research on the creep damage mechanism of double fractured sandstone after thawing in the West frozen inclined shaft for the long-term stability evaluation and coal mine safety production after thawing in the artificial frozen inclined shaft. Based on the frozen inclined shaft project of a coal mine in Yushen mining area, this paper takes the sandstone of Luohe formation as the original rock, and uses the double fracture sandstone made of similar materials as the research object. The research methods of indoor test and theoretical analysis are used to analyze the deformation and failure characteristics of double fracture sandstone under triaxial compression test after thawing, and the creep mechanical properties of double fracture sandstone after thawing The main work and conclusions are as follows:

Based on the reasonable similar ratio, similar materials are used to make double fractured sandstone with different prefabricated fracture dip angles, and the freezing thawing tests of double fractured sandstone under different freezing temperatures are completed. With the increase of crack dip angle, the local damage effect of frost heaving force on the specimen decreases gradually. With the decrease of freezing temperature, the damage degree of sandstone like rock sample increases, and the amount of spalling at the edge and end of prefabricated crack increases gradually. The number and penetration degree of secondary cracks initiated by initial damage at the tip of prefabricated crack increase in varying degrees.

(2) The triaxial compression tests of double fractured sandstone after thawing at different freezing temperatures are completed. With the increase of confining pressure, the mechanical properties of fissured rock are improved. The failure mode changes from splitting failure to shear sliding failure. The particle breakage around the secondary main crack of fissured rock decreases. It shows that the plasticity of fissured rock increases with the increase of confining pressure. With the increase of fracture dip angle, the mechanical properties of double fracture sandstone first decrease and then increase, and the overall change trend presents a "U" shape. When the fracture dip angle is 30°, the mechanical properties are the weakest. With the decrease of freezing temperature, the mechanical properties of rock with different dip angles decrease after thawing, and the number of secondary cracks along the edge of prefabricated cracks increases after failure.

(3) The triaxial compression creep tests of the sandstone with different fracture angles and different freezing temperatures were completed. With the increase of fracture dip angle, the total creep first increases and then decreases, and the creep rate changes fastest when the fracture dip angle is 30° degrees. With the decrease of freezing temperature, the initial damage of rock sample increases, resulting in the increase of axial creep and creep rate at different creep stress levels. With the continuous improvement of load level, the longer the rock enters the stable creep stage, the more obvious the viscosity is. The creep failure mode of double fracture sandstone is basically the same as that of triaxial compression. With the decrease of freezing temperature, there are more and more secondary cracks in rocks with different dip angles, and the failure phenomenon is more and more obvious. 

(4) Through the nuclear magnetic resonance (NMR) tests of the undisturbed fractured rock, the unfrozen fractured rock and the unfrozen fractured rock after triaxial compression creep failure.The variation of pore structure of fractured rock with fracture dip angle and freezing temperature under three conditions is analyzed. The results show that the T₂ spectrum of the sandstone with different fracture angles moves to the right to a certain extent after the freeze thaw test. The signal amplitude is enhanced. The pore radius of the sandstone before and after freezing is mainly concentrated between , accounting for more than 98% of the total proportion, and the proportion of the remaining pore radius greater than the above is less than 2%. T₂ spectrum of the sandstone with double fracture type moves to the right after creep failure, the proportion of the first peak decreases, the proportion of the second and third peaks increases, and a new fourth peak appears. The creep rate of the sandstone with a fracture angle of 30° is the largest, and the corresponding spectrum area is the largest.

(5) Based on the damage mechanics and creep theory of rock, the burgers creep model is improved by introducing nonlinear viscoplastic body and aging deterioration factor. A nonlinear creep model considering the effect of primary joints is constructed. According to the creep test data of triaxial graded loading, the creep model is fitted and verified, and the fitting results are basically consistent with the test data.

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