Effect of Suction in the Infiltrometer on Water Infiltration into Crusted Soils

Abstract

【Objective】 Infiltrometer is a device to measure water infiltration into soil and soil hydraulic conductivity. Its performance depends on many factors. This paper aims to study the effect of the negative pressure in it on water infiltration in crusted soil. 【Method】 The crusts on the soil surface were created by artificial rainfalls on a loess slope; water infiltration into the soil was measured using a mini disc infiltrometer with the negative pressure in it varying from 1 to 5cm. We also measured saturated hydraulic conductivity of the soil using the constant-head method and then used it as a benchmark to test the results measured from the infiltrometer. Water flow under both methods was described by the Wooding and Philip model. 【Result】 The hydraulic conductivity measured using the constant head was more accurate and repeatable. The saturated hydraulic conductivity of the crust and soil matrix was 74.00 cm/d and 12.00 cm/d respectively. The indexes of cumulative water infiltration, steady infiltration rate, infiltration rate and hydraulic conductivity of the crust and soil matrix measured by the infiltrometer decreased with the increase in the negative pressure. Using the saturated hydraulic conductivity measured from the infiltrometer, the Philip model reproduced the infiltration process more accurately, despite the effect of the negative pressure. Fitting the results to the van Genuchten formula revealed that the parameters α and n were 0.039 cm and 2.72 respectively for the crusts, and 0.024 cm and 2.83 respectively for the soil matrix. 【Conclusion】 Negative pressure in the infiltrometer affects saturated hydraulic conductivity calculated using the measured data from crusted soil, and should be considered in data analysis.

Keywords

• mini disc infiltrometer
• structural crusts
• sedimentary crust
• saturated hydraulic conductivity
• van genuchten parameter