Abstract
Boltzmann transform method, wetting front advancing method and instantaneous profile method are widely used in measuring hydraulic conductivity of unsaturated soils. However, all the three methods are based on relatively strong assumptions. In this study, a new Boltzmann variable was proposed based on the experimental observation that the wetting front advancing distance is not always proportional to the square of time. The improved Boltzmann transform method incorporating the new Boltzmann variable can significantly improve the accuracy of hydraulic conductivity determination. For the wetting front advancing method, a new formula for calculating the hydraulic gradient using central difference was proposed to reduce the fluctuation of determined hydraulic conductivity curve while using data recorded with small time intervals. A series of numerical tests including the horizontal absorption test, vertical ponding test and vertical capillary rise test were performed to verify the accuracy of hydraulic gradient and water flow rate calculated by wetting front advancing method. Results show that the calculated hydraulic gradients in low suction range are far from the real values except for the vertical ponding test and only the vertical ponding test can give reasonable hydraulic conductivity in both low and high suction ranges. For the instantaneous profile method applied in infiltration test with one end of soil column maintained at saturation, using the connected linear line with consideration of the location of wetting front to represent profiles of water content and suction can improve the accuracy significantly.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.