Effect of Unsaturated Flow on the Groundwater Table in Drainage Layer and Saturated Model Modification

2011 ◽  
Author(s):  
Han-Cheng Dan ◽  
Liang Li ◽  
Hui Yao ◽  
Su-Ping Luo
Keyword(s):  
Unsaturated Flow ◽  
Groundwater Table ◽  
Saturated Model ◽  
Drainage Layer ◽  
Model Modification

Capillary effect on flow in the drainage layer of highway pavement

2012 ◽  
Vol 39 (6) ◽  
pp. 654-666 ◽  
Author(s):  
Han-Cheng Dan ◽  
Pei Xin ◽  
Ling Li ◽  
Liang Li ◽  
David Lockington
Keyword(s):  
Unsaturated Flow ◽  
Groundwater Table ◽  
Richards Equation ◽  
Capillary Effect ◽  
Saturated Flow ◽  
Drainage Layer ◽  
Flow Models ◽  
Model Based ◽  
D Model ◽  
Highway Pavement

This paper aims to examine capillarity effect on flows in the drainage layer of highway pavement. A two-dimensional (2-D) model based on the Richards equation was used to simulate saturated and unsaturated flows in the drainage layer. For comparison, flows were also simulated using a 1-D Boussinesq equation based model and a 2-D model based on the Laplace equation, both assuming saturated flow only. The drainage layer was modeled with sand and gravel, which possess similar hydraulic properties to those of commonly used filling materials in practice. The results showed that the two saturated flow models agreed well with each other, indicating the dominance of horizontal flow in the drainage layer. However, their predictions differed significantly from those of the variably saturated flow models. The latter model predicted significant flow activities in a relatively large unsaturated zone, especially for a sandy drainage layer. Such unsaturated flow contributes to and enhances the capacity of the drainage layer. With the unsaturated flow neglected, the saturated flow models over-predicted the extent of the saturated zone and hence the groundwater table elevation. As the current engineering design of the drainage layer is typically based on the groundwater table elevation predicted by the saturated flow models, the finding of this study suggests that the design criterion is likely to lead to over-design of the drainage system. Further work is also required to prove the practical significance of the capillary effect and account for other factors.

Transient unsaturated flow in the drainage layer of a highway: solution and drainage performance

2017 ◽  
Vol 20 (3) ◽  
pp. 528-553 ◽  
Author(s):  
Han-Cheng Dan ◽  
Zhi Zhang ◽  
Xiang Liu ◽  
Jia-Qi Chen
Keyword(s):  
Unsaturated Flow ◽  
Drainage Layer

scholarly journals Simulation of saturated and unsaturated flow in karst systems at catchment scale using a double continuum approach

2012 ◽  
Vol 16 (10) ◽  
pp. 3909-3923 ◽  
Author(s):  
J. Kordilla ◽  
M. Sauter ◽  
T. Reimann ◽  
T. Geyer
Keyword(s):  
Unsaturated Flow ◽  
Small Scale ◽  
Saturated Model ◽  
Spring Discharge ◽  
Karst Spring ◽  
Continuum Approach ◽  
Catchment Scale ◽  
The Matrix ◽  
Karst Systems ◽  
Linear Exchange

Abstract. The objective of this work is the simulation of saturated and unsaturated flow in a karstified aquifer using a double continuum approach. The HydroGeoSphere code (Therrien et al., 2006) is employed to simulate spring discharge with the Richards equations and van Genuchten parameters to represent flow in the (1) fractured matrix and (2) conduit continuum coupled by a linear exchange term. Rapid vertical small-scale flow processes in the unsaturated conduit continuum are accounted for by applying recharge boundary conditions at the bottom of the saturated model domain. An extensive sensitivity analysis is performed on single parameters as well as parameter combinations. The transient hydraulic response of the karst spring is strongly controlled by the matrix porosity as well as the van Genuchten parameters of the unsaturated matrix, which determine the head dependent inter-continuum water transfer when the conduits are draining the matrix. Sensitivities of parameter combinations partially reveal a non-linear dependence over the parameter space. This can be observed for parameters not belonging to the same continuum as well as combinations, which involve the exchange parameter, showing that results of the double continuum model may depict a certain degree of ambiguity. The application of van Genuchten parameters for simulation of unsaturated flow in karst systems is critically discussed.

Estimation of Unsaturated Flow Parameters Using GPR Tomography and Groundwater Table Data

2008 ◽  
Vol 7 (4) ◽  
pp. 1239-1252 ◽  
Author(s):  
M. Bagher Farmani ◽  
Nils-Otto Kitterød ◽  
Henk Keers
Keyword(s):  
Unsaturated Flow ◽  
Groundwater Table ◽  
Flow Parameters ◽  
Table Data

scholarly journals Simulation of saturated and unsaturated flow in karst systems at catchment scale using a double continuum approach

2012 ◽  
Vol 9 (2) ◽  
pp. 1515-1546
Author(s):  
J. Kordilla ◽  
M. Sauter ◽  
T. Reimann ◽  
T. Geyer
Keyword(s):  
Unsaturated Flow ◽  
Small Scale ◽  
Saturated Model ◽  
Spring Discharge ◽  
Karst Spring ◽  
Continuum Approach ◽  
Catchment Scale ◽  
The Matrix ◽  
Karst Systems ◽  
Linear Exchange

Abstract. The objective of this work is the simulation of saturated and unsaturated flow in a karstified aquifer using a double continuum approach. The HydroGeoSphere code (Therrien et al., 2006) is employed to simulate spring discharge with the Richards equations and van Genuchten parameters to represent flow in the (1) fractured matrix and (2) conduit continuum coupled by a linear exchange term. Rapid vertical small-scale flow processes in the unsaturated conduit continuum are accounted for by applying recharge boundary conditions at the bottom of the saturated model domain. An extensive sensitivity analysis is performed on single parameters as well as parameter combinations. The transient hydraulic response of the karst spring is strongly controlled by the matrix porosity as well as the van Genuchten parameters of the unsaturated matrix, which determine the head dependent inter-continuum water transfer when the conduits are draining the matrix. Sensitivities of parameter combinations partially reveal a non-linear dependence over the parameter space. This can be observed for parameters not belonging to the same continuum as well as combinations, which involve the exchange parameter, showing that results of the double continuum model may depict a certain degree of ambiguity.

Dynamics of groundwater table and soil desalination of platform fields in coastal wasteland

2012 ◽  
Vol 19 (6) ◽  
pp. 1354-1358
Author(s):  
Xiao-Xia DONG ◽  
Xue-Jun WANG ◽  
Zhao-Hui LIU ◽  
Ze-Qiang SUN ◽  
Dong-Feng ZHENG
Keyword(s):  
Groundwater Table ◽  
Soil Desalination

Parameter Determination for Chloride and Tritium Transport in Undisturbed Lysimeters during Steady Flow

1992 ◽  
Vol 23 (2) ◽  
pp. 89-104 ◽  
Author(s):  
Ole H. Jacobsen ◽  
Feike J. Leij ◽  
Martinus Th. van Genuchten
Keyword(s):  
Experimental Data ◽  
Unsaturated Flow ◽  
Transport Model ◽  
Time Moment ◽  
Breakthrough Curves ◽  
Coarse Sand ◽  
Retardation Factor ◽  
Parameter Determination ◽  
Model Parameters ◽  
Water Fraction

Breakthrough curves of Cl and 3H2O were obtained during steady unsaturated flow in five lysimeters containing an undisturbed coarse sand (Orthic Haplohumod). The experimental data were analyzed in terms of the classical two-parameter convection-dispersion equation and a four-parameter two-region type physical nonequilibrium solute transport model. Model parameters were obtained by both curve fitting and time moment analysis. The four-parameter model provided a much better fit to the data for three soil columns, but performed only slightly better for the two remaining columns. The retardation factor for Cl was about 10 % less than for 3H2O, indicating some anion exclusion. For the four-parameter model the average immobile water fraction was 0.14 and the Peclet numbers of the mobile region varied between 50 and 200. Time moments analysis proved to be a useful tool for quantifying the break through curve (BTC) although the moments were found to be sensitive to experimental scattering in the measured data at larger times. Also, fitted parameters described the experimental data better than moment generated parameter values.

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