Modeling Soil Hydraulic Conductivity Measurement in Workshop Conditions

Abstract

The aim of this study is to model the system that measures soil hydraulic conductivity using Programmable Logic Control (PLC), pressure transducer and motor pump in workshop conditions. In the study, a plastic pipe with a length of 2 m and a diameter of 100 was prepared to simulate an auger hole. In addition, a set was created using PLC and its module. In the hydraulic conductivity measurement system, the auger hole method (the bottom of the auger hole is above the impermeable layer) is used. Using the auger-hole equation, the system‘s program was written in CODESYS-ST language and uploaded to the PLC. As a result of the regression analysis between the water head in the pipe (auger-hole) measured by hand (ESY) and PLC (PLCSY), an equation as PLCSY = 0,99ESY + 1,69 (R² = 1) was obtained and the Mean Absolute Percent Error (MAPE) of these two data sets was calculated as 0,41%. Each hydraulic conductivity measurement time is approximately 5, 6 and 8 minutes when the valve is fully open and half open and one-third open. The distance from the pipe base to the static level (d, cm) was measured as averages of 122.83, 123.91 and 123.7 cm on, respectively. In the first quarter section, the average times taken for the water level to rise from 20 to 25, 25 to 30, 30 to 35 and 35 to 40 was determined as 4.4, 6.0 and 26.1 seconds, respectively. The hydraulic conductivity values were calculated as 18.6, 13.2 and 3.1 cm/hour at the valve openings, respectively. The measured data is saved on an SD card. All of these processes are done automatically. The expectation that this system will measure hydraulic conductivity accurately, economically and quickly in field conditions is high and should be tested in field conditions.