Development of simple and compact in-situ testing system measurement in unsaturated soils

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It is well noticed that in-situ measurement and evaluation of saturated-unsaturated soil hydraulic properties is essential to practical and accurate prediction of water movement in soil such as natural slope, embankment, landfill and agricultural field.In this research, firstly a fast, simple and nondestructive procedure to measure near-surface soil water content profiles in unsaturated sandy soils is proposed. Surface ground-penetrating radar (GPR) system is employed to estimate the average soil water content in the survey region as a function of the soil dielectric constant measured by electromagnetic wave velocities. GPR has a couple of advantages over the intrusive soil moisture sensors. GPR system offers a simple approach for in-situ determination of soil water content and a completely non-intrusive measurement. GPR may be a suitable for low-cost mapping of soil water content profiles in large sample volume.Secondly, a new field experimental method of determining field-saturated and unsaturated hydraulic conductivity continuously in the near surface of unsaturated soils is proposed. In this method, a ponded single-ring infiltrometer technique, such as the Guelph Pressure Infiltrometer (GPI) method has been investigated based on the field and numerical experiments in our study. The GPI method is performed to determine the field-saturated hydraulic conductivity. The instantaneous profile method with the unit gradient assumption was applied to determine unsaturated hydraulic conductivity as a function of volumetric water content during drainage period. The vertical soil moisture profiles were measured by using a portable device for collecting soil water content information from multiple depths. The advantage of the proposed method is that it allows measurement of hydraulic conductivity of the unsaturated soils by quite simple in-situ permeability test data. The utility of our proposed method is demonstrated by using numerical models.