土体含水率监测的移动点热源法研究

土体含水率监测的线热源法对加热功率要求较高，当热源强度不稳定时，监测结果容易受到影响。为了解决线热源法的不足，提出了土体含水率监测的移动点热源（point heat source，PHS）法。该方法利用土体热物性与含水率之间的相关性，通过监测土体中PHS的降温规律间接识别含水率。通过数值模拟研究了点热源在含水率均匀分布的土体中的传热规律，根据热源降温曲线的特征，定义了含水率判别指标η，进而建立了含水率与判别指标的拟合关系，并对监测灵敏度的影响因素进行了参数分析。在含水率非均匀分布的土体中开展了点热源降温规律的数值模拟，根据测点降温时程曲线计算含水率判别指标，并利用含水率与判别指标的拟合公式反演含水率分布。结果表明，点热源法反演得到的含水率分布与实际值吻合较好，验证了该方法的理论可行性。通过模型试验进一步验证了该方法的可行性。

A mobile point heat source method for soil moisture monitoring

The line heat source method of soil moisture monitoring requires higher heating power. When the intensity of the heat source is unstable, the monitoring results are easily affected. To solve the shortcomings of the line heat source method, a mobile point heat source (PHS) method for soil moisture monitoring is developed in this study. This method uses the correlation between the thermal physical properties of soil and the moisture content to indirectly identify the moisture content by monitoring the cooling law of the PHS in the soil. Firstly, the heat transfer law of the PHS in the soil with evenly distributed moisture content was examined through numerical simulation. According to the characteristics of the cooling curves of the heat source, the moisture content discrimination index η was defined, and then the fitting relationship between the moisture content and the discrimination index was established. In addition, parameter analysis was carried out on the factors affecting the monitoring sensitivity. Then, numerical simulation of the PHS cooling law was carried out in the soil with unevenly distributed moisture content, and the moisture content discrimination index was calculated according to the time history curve at the cooling stage of the measuring point. After that, the moisture content distribution was inverted by the fitting formula of the moisture content and the discrimination index. The results show that the moisture content distribution inverted by the PHS method is in good agreement with the actual value, which verifies the theoretical feasibility of the method. Finally, the feasibility of the method is further verified by model tests.