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采用CT技术和TH204型非金属超声波仪测试,探讨了干湿循环作用下膨胀土的细观结构及其平均纵波波速的变化规律,并运用损伤力学的研究方法定义基于CT数的损伤变量,据此建立了干湿循环作用引起的细观结构变化与平均纵波波速变化之间的关系。研究结果表明:第1~4次干湿循环对膨胀土细观结构变化影响较大,内部微裂隙发育明显,第7~8次干湿循环对细观结构影响甚微;膨胀土的平均纵波波速随着循环次数的增加呈非线性衰减,并最终趋于稳定;随着干湿循环次数的增加,膨胀土损伤变量逐渐增加,其细观结构损伤演化是一种非线性累积过程;膨胀土平均纵波波速与基于CT数的损伤变量具有良好的指数衰减关系。
Using CT technology and TH204 non-metallic ultrasonic testing instrument, the change law of mesostructure and average longitudinal wave velocity of expansive soils under wetting and drying cycles was discussed. The damage variables based on CT numbers were defined by the method of damage mechanics. According to This establishes the relationship between the mesoscopic structure change caused by the wetting and drying cycles and the variation of the average longitudinal wave velocity. The results show that the first to the fourth wet-dry cycles have a great influence on the microscopic structure of the expansive soils, and the micro-cracks in the inner part of the expansive soils have obvious development. The dry-wet cycles 7-8 have little effect on the mesostructure. The wave velocity decays non-linearly with the increase of the number of cycles, and finally tends to be stable. With the increase of the number of wet-dry cycles, the damage variable of expansive soil increases gradually, and the damage evolution of mesostructures is a nonlinear cumulative process. The average longitudinal wave velocity has a good exponential decay relationship with the damage variables based on CT numbers.