为探究寒区岩土工程在冻融循环和长期荷载共同作用下的变形特性，本文以陕西彬长矿区红砂岩为研究对象，首先对冻融循环作用后的不同饱和状态岩样开展电镜扫描、核磁共振、常规单轴压缩及分级加载蠕变试验，分析冻融作用下岩样细-微观结构、力学特性及蠕变特性变化，研究饱和度和冻融循环次数对岩石孔隙度、常规力学参数及蠕变参数的影响。其次依据岩石流变力学及损伤力学等理论知识，建立了冻融环境下砂岩冻融-损伤蠕变模型。本文主要结论如下：

(1) 对冻融作用后不同饱和度岩样进行质量和纵波波速测定，试验结果表明：饱和状态及冻融循环条件下造成红砂岩质量损伤差异显著，岩样质量衰减幅值随冻融循环次数的增加逐渐增加，且当饱和度达到70%时，岩样质量衰减幅值显著增大；随着冻融次数和饱和度增大，纵波波速整体呈减小趋势，且随饱和度增大减小速率变大，当饱和度大于70%，纵波波速降低幅值随冻融次数增加逐渐增大。

(2) 对冻融作用后不同饱和度岩样开展核磁共振和电镜扫描试验，研究饱和度对岩样内部微细观冻融损伤差异，试验结果表明：随着饱和度的增大，胶结物的溶蚀作用逐渐加速，颗粒间连接减弱，溶蚀孔洞变多；岩样冻融循环后裂隙平均长度和孔隙平均面积均随饱和度增大逐渐增长；岩样孔隙分布特征呈现三峰分布，随着饱和度增大，中孔隙面积所占百分比逐渐增加，且当饱和度达到90%，中孔隙代替微小孔隙成为主要孔隙形式，中孔隙所占峰面积逐渐成为主峰。

(3) 对冻融作用后不同饱和度岩样进行常规单轴压缩试验，研究饱和度对抗压强度、弹性模量及变形特性影响规律，建立冻融-受荷损伤演化方程，试验结果表明：抗压强度和弹性模量均随饱和度增大呈“上凸式”指数衰减；当饱和度从30%增加到70%时，饱和度对岩样力学性能影响较小；当饱和度大于70%以后，岩样冻融损伤过程中力学性能的劣化速率随饱和度的持续增大而逐渐加快；随着冻融循环次数增多，抗压强度和弹性模量均呈“下凹式”指数衰减。

（4）对冻融作用后的不同饱和度岩样进行单轴分级加载蠕变试验，研究饱和度对蠕变特性的影响规律，试验结果表明：随着饱和度增大，岩样瞬时应变和蠕变应变逐渐增大，且相同应力水平荷载下，蠕变变形逐渐增大；不同应力水平增加幅度存在差异，随着应力水平的增加，蠕应变增加幅度逐渐增大，且当应力水平达到70%时，这种现象逐渐显现。岩石稳态蠕变速率受饱和度的影响较大。同一应力水平下，岩样稳态蠕变速率随饱和度增大呈非线性增长；在当饱和度达到70%后，由于内部水分子的增加，冻胀力增大，造成岩样结构内部劣化速率逐渐增大。稳态蠕变速率增长幅度逐渐增大。

(5) 饱和度的不同对岩样破坏模式有较大影响，岩样破坏方式以剪切破坏和张拉破坏为主。随着饱和度逐渐增大，岩样破坏裂缝逐渐增多，并出现微小裂纹，岩样裂纹间距逐渐形成，张拉特征显现。

(6) 根据冻融后岩样蠕变试验结果，提出考虑冻融作用及蠕变损伤的非线性粘性元件，建立考虑饱和度影响的冻融-损伤蠕变模型。依据三种不同理论，推导了一维应力状态下岩样蠕变本构方程。通过蠕变试验结果对模型进行参数识别及模型拟合，理论值与试验值拟合度高。建立的蠕变模型能够很好的说明冻融后不同饱和度岩样蠕变全过程

In order to explore the deformation characteristics of geotechnical engineering in cold regions under the combined effects of freeze-thaw cycles and long-term loads, this paper takes the red sandstone as the study object. Nuclear magnetic resonance, conventional uniaxial compression and staged loading creep tests, through the analysis of the fine-microstructure, mechanical properties and creep characteristics of rock samples under freeze-thaw cycles. Rock porosity, conventional mechanical parameters and creep parameters are affected by saturation and the number of freeze-thaw cycles.Finally, based on theoretical knowledge of rock rheology and damage mechanics, a freeze-thaw-damage creep model of red sandstone under freeze-thaw environment is established. The research conclusion includes six main aspects:

(1) After freez-thaw the quality and longitudinal wave velocity of the rock samples are measured. The test results show that the rock sample quality damage is significantly under the different saturated state and the freeze-thaw cycle conditions. When the saturation reaches 70%, the attenuation amplitude of the rock sample mass increases significantly; With the the number of freeze-thaw cycles and the saturation increases, the longitudinal wave velocity decreases. The speed becomes larger. When the saturation is greater than 70%, the margin of decrease in the longitudinal wave velocity gradually increases with the number of freeze-thaw cycles increase

(2) To study the microscopic freeze-thaw damage of the rock samples caused by the saturated state, NMR and scanning electron microscopy tests were carried out on rock samples with different saturation levels after freeze-thaw cycles .The test results show that: the dissolution of the cement gradually accelerates, the connection between particles is weakened, and the dissolution pores increase with the increase of saturation; The pores average length of the cracks and area of the gradually increase with the increase of saturation after the freeze-thaw cycle of the rock sample, The T₂ spectrum shows that pore distribution characteristics is a three-peak distribution. As the increase of saturation, the percentage of mesopore area gradually increases, and when the saturation reaches 90%, mesopores become the main pore form through replace micropores. The occupied peak area gradually become the main form.

(3) The conventional uniaxial compression tests on rock samples were carried out after freeze-thaw cycles. The law of compressive strength, elastic freeze-thaw-load damage evolution equation modulus and deformation characteristics with saturation and the number of freeze-thaw cycles has been established. The results show that the elastic modulus and peak strength decay exponentially as the saturation increases; when the saturation increases from 30% to 70%, Saturation has little effect on the mechanical properties of rock samples. When the saturation is greater than 70%, The degradation rate of the mechanical properties of rock samples gradually increases with the continuous increase of saturation, the peak strength and elastic modulus are both " "Concave" exponential decay with the number of freeze-thaw cycles increases

(4) The uniaxial hierarchical loading creep test was carried out on the rock samples with different saturation after freezing and thawing, and the influence of saturation on the creep characteristics of red sandstone was studied. The specific conclusions are as follows: the instantaneous strain and creep strain of the rock sample vary with the saturation The increase gradually increases. As the stress level increases, the creep strain increases gradually, and when the stress level reaches 70%, this phenomenon gradually appears. The steady-state creep rate of rock is greatly affected by saturation. Under the same stress level, the steady-state creep rate of the rock sample increases nonlinearly with the increase in saturation; when the saturation reaches 70%, the frost heave force increases due to the increase of internal water molecules, resulting in internal degradation of the rock sample structure The rate gradually increases. The steady-state creep rate increases gradually

(5) The difference of saturation has a great influence on the failure mode of rock samples.   the damaged cracks of the rock sample gradually increase with the increase of the saturation, and small cracks appear, the crack spacing of the rock sample gradually forms, and the tensile characteristics appear.

(6) According to the creep test results of rock samples after freezing and thawing, a nonlinear viscous element considering the effects of freezing and thawing and creep damage is proposed, and a freezing-thawing-damage creep model considering the effect of saturation is established. Based on three different theories, the constitutive equation of rock sample creep under one-dimensional stress state is derived. Parameter identification and model fitting are performed on the model through the results of the creep test, and the theoretical value and the test value have a high degree of fit. The creep model can well explain the whole process of creep of different saturation rock samples after freeze-thaw cycles.

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