The artificial ground freezing is an important technique for soft soil reinforcement and underground water sealing carried out by continuously refrigerating ground. It is of great significance to monitor the soil strength development in artificial ground freezing projects not only for better evaluation of the soil freeze–thaw status but also for predicting and controlling the concurrent adverse effects which may cause serious engineering accidents. In this study, the electromechanical impedance method was explored in monitoring the soil strength development in the freeze–thaw process. The lead zirconate titanate transducer was embedded inside the soil specimen, and changes in the conductance signatures were monitored throughout the soil freeze–thaw process. The experimental results indicate that the resonant frequency of the embedded lead zirconate titanate transducer can serve as a reliable index for assessment of the soil’s dynamic elastic modulus in the freeze–thaw process. More importantly, an analytical model was developed based on the piezo-elasticity theory to characterize the correlation between the electromechanical impedance of the lead zirconate titanate transducer and the soil’s mechanical properties, and its validity was further confirmed by the experimental research. Based on the proposed model, the development of the soil’s strength can be well predicted from the measured conductance signatures. As a nondestructive testing method, the proposed soil testing technique will help save considerable time and resources by avoiding the conventional sampling, specimen preparation, and testing of soil. The theoretical and experimental research will contribute to the future application of the electromechanical impedance method in real-life artificial ground freezing engineering projects.

中文翻译：

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基于机电阻抗技术的人工冻结工程软土强度变化监测新方法：理论建模与实验验证

人工冻结地面是对地面连续冷冻进行软土加固和地下水封堵的一项重要技术。监测人工冻融工程中的土体强度发展情况，不仅对更好地评价土体冻融状况，而且对预测和控制可能导致严重工程事故的并发不利影响具有重要意义。在这项研究中，探索了机电阻抗方法在冻融过程中监测土壤强度发展。锆钛酸铅传感器嵌入土壤样品中，在整个土壤冻融过程中监测电导特征的变化。实验结果表明，嵌入式锆钛酸铅换能器的共振频率可作为评价冻融过程中土壤动态弹性模量的可靠指标。更重要的是，建立了基于压电弹性理论的解析模型来表征锆钛酸铅换能器的机电阻抗与土壤力学特性之间的相关性，并通过实验研究进一步证实了其有效性。基于所提出的模型，可以从测量的电导特征很好地预测土壤强度的发展。作为一种无损检测方法，所提出的土壤检测技术将通过避免传统的取样、样品制备、和土壤测试。理论和实验研究将有助于机电阻抗法未来在现实人工地面冻结工程中的应用。