Soil cracking induced by extreme drought represents a widespread natural phenomenon occurring across the earth surface, capable of triggering multiple weakening mechanisms within surface soils, potentially leading to the instability and failure of slopes and agricultural infrastructures. This study proposes an innovative geophysical monitoring framework for detecting field soil cracking by combining the actively heated fiber-optic (AHFO) method and distributed fibre optical sensing (DFOS) based on optical frequency domain reflectometry (OFDR) technique, referred to as AH-OFDR framework. Laboratory calibration tests, field monitoring tests, numerical simulations, and sensitivity analyses were employed to comprehensively evaluate the feasibility, effectiveness, and limitations of the AH-OFDR framework for soil crack monitoring. Laboratory calibration confirmed that the DFOS-OFDR technique achieves a minimum spatial resolution and readout accuracy of 1 mm, along with a temperature measurement accuracy of ±0.1 °C. Field monitoring verified that the AH-OFDR framework can accurately detect soil cracks ranging in width from 0.01 m to 0.12 m. Additionally, numerical simulations not only validated the effectiveness of the AH-OFDR framework across a broader range of crack widths, from 0.01 m to 0.50 m, but also established a quantitative relationship between temperature changes and the spatial distribution of crack positions and widths. Notably, a critical crack width threshold of 0.30 m was identified within the AH-OFDR framework, significantly impacting the prediction of soil crack widths. Sensitivity analysis demonstrated the remarkable crack detection capabilities of the AH-OFDR framework, irrespective of the soil crack width and spacing. The AH-OFDR framework holds substantial potential as an innovative and high-resolution observational method for advancing our understanding of diverse geological and hydrogeological processes.

中文翻译：

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使用基于 OFDR 的分布式温度传感框架监测土壤开裂


极端干旱引起的土壤开裂是地球表面普遍发生的自然现象，能够触发表层土壤内的多种弱化机制，可能导致斜坡和农业基础设施的不稳定和失效。本研究提出了一种创新的地球物理监测框架，通过结合主动加热光纤 （AHFO） 方法和基于光频域反射计 （OFDR） 技术的分布式光纤传感 （DFOS） 来检测田间土壤开裂，称为 AH-OFDR 框架。采用室内校准测试、现场监测测试、数值模拟和敏感性分析，全面评价 AH-OFDR 框架用于土壤裂缝监测的可行性、有效性和局限性。实验室校准证实，DFOS-OFDR 技术实现了 1 mm 的最小空间分辨率和读出精度，以及 ±0.1 °C 的温度测量精度。 现场监测验证了 AH-OFDR 框架能够准确检测宽度为 0.01 m 至 0.12 m 的土壤裂缝。此外，数值模拟不仅验证了 AH-OFDR 框架在 0.01 m 至 0.50 m 的更广泛裂缝宽度范围内的有效性，而且还建立了温度变化与裂缝位置和宽度的空间分布之间的定量关系。值得注意的是，在 AH-OFDR 框架内确定了 0.30 m 的临界裂缝宽度阈值，对土壤裂缝宽度的预测产生了重大影响。敏感性分析表明，无论土壤裂缝的宽度和间距如何，AH-OFDR 框架都具有出色的裂缝检测能力。 AH-OFDR 框架作为一种创新的高分辨率观测方法，在促进我们对各种地质和水文地质过程的理解方面具有巨大的潜力。