Automated Method for Determining Infiltration Rate in Soils

The first goal of this study was determining in-situ soil's vertical saturated hydraulic conductivity (Ks) from the measured steady infiltration rate, initial soil parameters, and test arrangements of the Double Ring Infiltrometer (DRI) test. This was done by conducting 30 small scale DRI lab experiment, 9 full scale in-situ DRI, 9 in-situ Mini-Disk infiltrometer experiments, several lab measurements, and 864 simulated DRI tests using finite element program HYDRUS-2D. The effects of the ring diameter, head of ponding, ring depth, initial effective saturation, and soil macroscopic capillary length on measured steady infiltration rates was fully studied. M5' model trees and genetic programming methods were applied on the data to establish formulas for predicting the saturated hydraulic conductivity of the sand to sandy-clay materials. The accuracy of Ks measurements of each method was estimated using 30% of 864 data by comparing the predefined Ks measured from the initial assumptions of the finite element programs with the estimations of the suggested formulas. Another comparison was done by using the derived formulas to predict Ks values of the 9 field DRI experiments and comparing the predicted values with the Ks values measured with the lab falling head permeability tests. Compared to genetic programming method, M5' model had a better performance in prediction of Ks with correlation coefficient and the root mean square error values of 8.618E-01 and 2.823E-01, respectively. Tension Disc Infiltrometer was needed during the first part of the research. This test is a commonly used test setup for in-situ measurement of the soil infiltration properties. In the second part of this study, Mini Disk Infiltrometer was used in the lab to obtain the cumulative infiltration curve of the poorly graded sand for various suction rates and the hydraulic conductivity of the soil material was measured from the derived information. Various methods were proposed by several researchers for determination of hydraulic conductivity from the cumulative infiltration data derived from Tension Disc Infiltrometer. In this study, the hydraulic conductivity measurements were estimated by using eight different methods. These employed methods produced different unsaturated and saturated hydraulic conductivity values. The accuracy of each method was determined by comparing the estimated hydraulic conductivity values with the values obtained from the falling head permeability test. Finally, as the third part of the research, a system of automated DRI using Arduino microcontroller, Hall effect sensor, peristaltic pump, water level sensor, and constant-level float valve was designed and tested. The advantages of the current system compared to previous designed systems was discussed. The system configuration was illustrated for better understanding of the set-up. The system was mounted in a portable and weather resistant box and was applied to run DRI testing in the field to check the applicability and accuracy of the portable system in field measurements. Results of the DRI testing using the automated system were also presented.