Hydraulic Conductivity 
Knowing the coefficient of permeability (i.e., hydraulic conductivity) of a soil is vital to modeling the movement of water through saturated and unsaturated soils. Considerable effort has been expended to develop computer models capable of analyzing seepage through saturated/unsaturated soil systems. The movement of water through an unsaturated soil takes on the form of a function since its permeability varies with the degree of saturation of the soil. Determination of the hydraulic properties of an unsaturated soil is time consuming and expensive since several measurements must be made with the soil at various degrees of saturation. Consequently, it has become quite acceptable in many cases to utilize simplified estimation methods for the prediction of the hydraulic conductivity of saturated/unsaturated soil systems.
An understanding of the hydraulic properties of unsaturated soils is critical when modeling complex seepage problems. The permeability function of a soil is related to the soilwater characteristic curve. As a result, the unsaturated permeability of a soil is commonly estimated based on the soilwater characteristic curve. SVSOILS provides the ability to both store unsaturated soil data as well as estimate the unsaturated soil permeability function which is related to soil suction. The software has implemented the management of saturated soil permeability data as well as a number of methods that can be used to estimate the saturated permeability of a soil.
Saturated Hydraulic Conductivity The saturated hydraulic conductivity, ksat value is the hydraulic conductivity of the material in the xdirection when soil suction is zero (or the porewater pressure is zero or positive).
ksat Options: SVSOILS software contains 15 ksat methods for estimating the saturated coefficient of permeability. However, the ksat methods shown in the drop list are those that have their required inputs entered into the software. The table below shows the required inputs for each ksat option. A description of these methods can be found in the sections below and in the SVSOILS Theory Manual.
Constant ksat: The Constant ksat field displays the ksat value.
Unsaturated Hydraulic Conductivity The Unsaturated Hydraulic Conductivity drop list contains the estimation methods that are currently implemented in the SVSOILS software.
The estimation methods provide a smooth representation of the saturated/unsaturated permeability (or hydraulic conductivity) curve. SVSOILS also allows for the input of laboratory data where linear interpolation is used to determine the permeability between measured laboratory data points. It should be noted that the interpolation procedure may not be ideal under some circumstances.
If “None” is selected, the ksat value will be used to generate the unsaturated hydraulic conductivity function. If Laboratory Data is selected the data entered in the Laboratory Data section of the tab will be used.
The Ksat vs Void Ratio method droplist contains all the methods currently implemented in SVSOILS for the fitting of laboratory data using mathematical equations. A description of these methods can be found in the following sections and in the SVSOILS Theory Manual.
Related Links (Topics relating to this section): Saturated Hydraulic Conductivity Unsaturated Hydraulic Conductivity
