基于高密度电阻率法的水分迁移模型试验研究

Model tests on moisture migration based on high-density electrical resistivity tomography method

在土工模型试验中,常用的应用于水分及溶质迁移过程量测的传感器量测、图像分析及取样分析等方法并不能充分满足三维、无损、实时的量测需求。高密度电阻率成像法为土工模型试验中三维、无损、实时量测需求提供了新的解决思路。基于高密度电阻率成像法发展一套适用于常规物理模型及超重力离心环境中土体电阻率测试设备和分析方法,并通过开展模型试验验证其应用于水分迁移过程量测的适用性及有效性。常规物理模型试验(1g)表明,该设备及方法能够获得模型土体中电阻率的三维时空分布,入渗过程中电阻率与含水率的分布及变化合理反映电阻率与含水率定性关系;在低有效饱和度区间,电阻率法具有很高的灵敏度。离心模型试验结果表明,重力水平的变化可导致水分在模型土柱中的分布发生显著变化;实时量测技术及分析方法可为土工离心环境中渗流及溶质运移过程的分析提供更为准确的依据。高密度电阻率成像法可以成功应用于常规物理模型及超重力离心环境中水分迁移过程量测,并保证一定的精度和灵敏度。

In geotechnical model tests, the methods conventionally employed in measuring water content and solute transport include sensor techniques, image processing techniques and direct soil sampling methods. However, these techniques cannot fully satisfy the necessities of three-dimensional, non-destructive and real-time measurement, especially in geotechnical centrifuge environment. A set of new measuring device and analyzing technique based on the high-density electrical tomography（ERT） method, is developed to investigate water migration at multiple gravitational levels. Two model tests, one on ground and the other in a geotechnical centrifuge, are conduced to verify the capability of the developed device in capturing moisture migration and distribution. The 3D infiltration model tests on ground（1g） show that the device is capable of measuring the 3D spatial and temporal distribution of soil resistivity in the model. The water migration and distribution during the infiltration process is reasonably reflected by the variation and distribution of soil resistivity. The resistivity method presents high sensitivity, especially when the soil is at relatively low saturation degree. In the 50 g centrifugal model tests, obvious non-uniformity of water content distribution is observed at the loading and unloading stages, which indicates that moisture migration is highly subjected to gravitational levels and boundary conditions. The capability of real-time measurement and analysis of the ERT method provides critical insights into moisture migration in geotechnical model tests at multiple gravitation levels, and can be fed into a wide range of investigations regarding seepage and solute transport.