Development of moisture content distribution of triaxial samples during drying process

The real-time measurement of moisture content distribution in the triaxial tests is significant to suction balance, shear rate and wetting deformation. The principle of water content tests on triaxial samples is proposed by extending van der Pauw (vdP) resistivity theory. Moreover, the flexible printing electrode (FPE) with 0.1 mm in thickness and the vdP method device are developed. The compatibility and reliability of the device are verified through the sensitivity factor tests such as net confining pressure and temperature. Finally, the triaxial drying-wetting cycle tests under constant pressure are carried out. At the same time, the layered resistivity is monitored. The test results show that the test device needs the preloading of net confining pressure of at least 120 kPa to ensure the complete cover between the FPE and the samples, and the net confining pressure shall be more than 20 kPa to ensure the cover status in the tests. The temperature has a certain influence on the results of resistivity tests, and the Campbell model can effectively correct the temperature-introduced errors. In the process of moisture wetting, the resistivity decreasing from bottom to top can be observed dramatically. In the process of drying, the resistivity decreases gradually from top to bottom. Finally, the method for calculating the layered moisture content during drying process is proposed, and the evolution law of moisture content distribution is analyzed.