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摘要: 對低溫凍結紅砂巖進行動態沖擊實驗,研究高應變率下紅砂巖動態力學特性的溫度效應,運用損傷理論和能量理論,分析不同負溫對紅砂巖強度、損傷變量及能量耗散的影響,結合斷口形貌分析,探究紅砂巖在較低負溫下動態力學強度出現劣化的原因.研究表明:較低的負溫(-30℃后)會使紅砂巖出現"凍傷",導致高應變率下巖石動態力學強度的急劇降低,宏觀上則容易出現動力擾動下的瞬時工程災變.根據斷口形貌分析,較低的負溫會導致紅砂巖內部組成物質間界面處生成大量裂紋,這些裂紋尖端塑性變形能力差,在高應變率加載下極易失穩擴展發生低應力脆性破壞,而膠結物由于組成礦物成分復雜更易受負溫影響,因此在動荷載和負溫雙重作用下往往是膠結物處先產生破壞,進而引起紅砂巖整體的破裂.Abstract: Under the action of negative temperature, the static strength of a rock increases; however, the rock will tend to be brittle, failure strain will decrease, and the rock will also bear the action of internal ice heave force, which leads to complex dynamic behavior of rocks under high strain rate loading. In addition, the geotechnical structures in cold regions are prone to sudden engineering disasters under dynamic disturbance. In this study, a dynamic impact experiment of low-temperature frozen red sandstone was carried out to investigate the temperature effect on the dynamic mechanical properties of red sandstone under high strain rate. Based on the damage theory and energy theory, the effects of different negative temperatures on the strength, damage variables, and energy dissipation of red sandstone were analyzed, and the reasons for the dynamic mechanical strength deterioration of red sandstone at lower negative temperatures were explored using fracture morphology analysis. Research shows that the low negative temperature (after -30℃) can cause a "frostbite" red sandstone, resulting in a sharp decrease in the dynamic mechanical strength of rocks under high strain rate, and transient engineering disasters can easily occur under dynamic disturbance. According to the fracture morphology analysis, the low negative temperature will cause a large number of cracks to be generated at the interface between the components in the red sandstone. The plastic deformation ability of the crack tip is poor, and the crack can easily lose stability and expand under high strain rates, resulting in the low-stress brittle failure. However, due to the complex mineral composition of the cementitious materials, they are more susceptible to negative temperature. Therefore, under the double action of dynamic load and negative temperature, the damage usually occurs first at the cementitious materials and then results in the fracture of the whole red sandstone.
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Key words:
- red sandstone /
- rock dynamics /
- dissipation energy /
- fracture morphology
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表 1 紅砂巖基本物理參數
Table 1. Basic physical parameters of red sandstone
縱波速度/(m·s-1) 干密度/(kg·m-3) 飽和密度/(kg·m-3) 飽水率/% 干燥 飽水 2780 3651 2292 2371 3.46 -
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