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以花岗岩为岩样在最低冻结温度为-40℃、融化温度为20℃的条件下对5组岩样开展了冻融循环试验,最高累积冻融循环次数为100次,并采用核磁共振(NMR)技术检测岩样内部损伤变化。试验结果表明,冻融作用会对岩石内部造成损伤,循环次数达到一定值时岩样表面产生明显裂纹;NMR T2谱图和成像结果表明,冻融作用使岩样孔隙结构重新分布,孔隙数量随循环次数增加而增加,产生裂纹后T2曲线信号幅度发生显著变化。最后使用损伤力学原理对花岗岩冻融损伤机制进行探讨,得到材料连续性与孔隙率的损伤关系、有效应力与孔隙率的关系表达式,并以岩样核磁共振结果为基础,得出其有效应力与循环次数的表达式。
Five samples were tested for freeze-thaw cycles with the lowest freezing temperature of -40 ° C and the melting temperature of 20 ° C. The highest cumulative number of freeze-thaw cycles was 100 times, and nuclear magnetic resonance (NMR) ) Technology to detect changes in rock specimen internal damage. The experimental results show that freezing and thawing can cause damage to the rock. When the number of cycles reaches a certain value, obvious cracks appear on the surface of the rock sample. NMR T2 spectrum and imaging results show that the pore structure is redistributed by the freeze-thaw action. The number of cycles increased and the signal amplitude of T2 curve changed significantly after the crack occurred. Finally, the mechanism of damage and freeze-thaw damage of granite was discussed by using the principle of damage mechanics. The relationship between material continuity and porosity, the relation between effective stress and porosity were obtained. Based on the NMR results, the effective stress The expression with the number of loops.