A study on the geotechnical characterization and water retention characteristic curve of pond ash

2019 ◽  
Vol 80 (5) ◽  
pp. 929-938
Author(s):  
Janmeet Singh ◽  
Sanjay Kumar Singh ◽  
M. A. Alam
Keyword(s):  
Hydraulic Conductivity ◽  
Water Retention ◽  
Characteristic Curve ◽  
Input Parameter ◽  
Wetting And Drying ◽  
Pond Ash ◽  
Retention Characteristic ◽  
Unsaturated Hydraulic Conductivity ◽  
Conductivity Function ◽  
Engineering Practices

Abstract The understanding of the engineering behaviour of unsaturated soil is totally dependent on the water retention characteristic curve (WRCC). In this paper, a comprehensive study of the WRCCs of pond ash along with the ash's geotechnical behaviour has been made. The WRCC has been drawn experimentally using a Fredlund device based upon the pressure plate technique for both wetting and drying cycles. Further, an investigation was carried out to study WRCC hysteresis of pond ash. There exists a considerable hysteresis in drying and wetting curves of pond ash sample. The different WRCC models were used to fit the experimental WRCC data. The effect of compaction on WRCC was also studied. The air entry value in the case of a loose sample is low and the sample gets nearly desaturated at low soil suction as compared to a dense sample. Also, the wetting WRCC is predicted using the Feng and Fredlund model as it is difficult and time consuming to measure the whole hysteresis. The predicted results are compared with the measured wetting WRCC. Since the direct measurement of unsaturated hydraulic conductivity is difficult to obtain in engineering practices, the unsaturated hydraulic conductivity function is predicted using the measured WRCC as the input parameter using SEEP/W software.

Physically based closed-form expression for the bimodal unsaturated hydraulic conductivity function

2013 ◽  
Vol 68 (2) ◽  
pp. 328-334
Author(s):  
Shiyu Liu ◽  
Noriyuki Yasufuku ◽  
Qiang Liu ◽  
Hazarika Hemanta
Keyword(s):  
Experimental Data ◽  
Hydraulic Conductivity ◽  
Closed Form ◽  
Characteristic Curve ◽  
Complex Structure ◽  
Closed Form Expression ◽  
Form Expression ◽  
Unsaturated Hydraulic Conductivity ◽  
Physically Based ◽  
Conductivity Function

Simulation of flow and contaminant transport through the vadose zone requires accurate parameterization of the soil hydraulic properties. This requirement is particularly important for soils with a complex structure. In the present study, a physically based closed-form expression for the bimodal unsaturated hydraulic conductivity function is proposed for soils with bimodal pore-size distribution. It combines the bimodal representation of the soil-water characteristic curve (SWCC) function of Liu with the conductivity representation model of Mualem. The proposed equations are defined by parameters that have physical significance, which can be related to the properties of the materials. Experimental data for the representation of bimodal SWCCs and corresponding hydraulic conductivity curves were used to demonstrate the applicability of the proposed functions. The proposed approaches resulted in good agreement with experimental data. These functions can potentially be used as an effective tool for identifying hydraulic porosities in mediums with a complex structure.

Application of the Groenevelt - Grant soil water retention model to predict the hydraulic conductivity

Soil Research ◽  
2010 ◽  
Vol 48 (5) ◽  
pp. 447 ◽  
Author(s):  
C. D. Grant ◽  
P. H. Groenevelt ◽  
N. I. Robinson
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Water Retention ◽  
Soil Water Retention ◽  
Retention Model ◽  
Unsaturated Hydraulic Conductivity ◽  
Incomplete Gamma Functions ◽  
Relative Water ◽  
Van Genuchten Model ◽  
Conductivity Function

We outline several formulations of the Groenevelt–Grant water retention model of 2004 to show how it can be anchored at different points. The model is highly flexible and easy to perform multiple differentiations and integrations on. Among many possible formulations of the model we choose one anchored solely at the saturated water content, θs, to facilitate comparison with the van Genuchten model of 1980 and to obtain a hydraulic conductivity function through analytical integration: where, k0, k1, and n are fitting parameters. We divided this formulation by θs to obtain the relative water content, θr(h), and inverted the function to produce a form required for integration, namely: in which the parameter β is introduced to accommodate both the ‘Burdine’ and ‘Mualem’ models. The integrals are identified as incomplete gamma functions and are distinctly different from the incomplete beta functions embodied in the van Genuchten–Mualem models. Rijtema’s data from 1969 for 20 Dutch soils are used to demonstrate the procedures involved. The water retention curves produced by our Groenevelt–Grant model are virtually indistinguishable from those produced by the van Genuchten model. Relative hydraulic conductivities produced by our Mualem and Burdine models produced closer estimates of Rijtema’s measured values than those produced by the van Genuchten–Mualem model for 19 of his 20 soils. This work provides an alternative to the widely used van Genuchten–Mualem approach and represents a preamble for the, as yet unsatisfactory, treatment of the tortuosity component of the unsaturated hydraulic conductivity function.

Method for Quick Prediction of Hydraulic Conductivity and Soil-Water Retention of Unsaturated Soils

2018 ◽  
Vol 2672 (52) ◽  
pp. 108-117 ◽  
Author(s):  
Shaoyang Dong ◽  
Yuan Guo ◽  
Xiong (Bill) Yu
Keyword(s):  
Finite Element ◽  
Hydraulic Conductivity ◽  
Soil Properties ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Characteristic Curve ◽  
Soil Water Retention

Hydraulic conductivity and soil-water retention are two critical soil properties describing the fluid flow in unsaturated soils. Existing experimental procedures tend to be time consuming and labor intensive. This paper describes a heuristic approach that combines a limited number of experimental measurements with a computational model with random finite element to significantly accelerate the process. A microstructure-based model is established to describe unsaturated soils with distribution of phases based on their respective volumetric contents. The model is converted into a finite element model, in which the intrinsic hydraulic properties of each phase (soil particle, water, and air) are applied based on the microscopic structures. The bulk hydraulic properties are then determined based on discharge rate using Darcy’s law. The intrinsic permeability of each phase of soil is first calibrated from soil measured under dry and saturated conditions, which is then used to predict the hydraulic conductivities at different extents of saturation. The results match the experimental data closely. Mualem’s equation is applied to fit the pore size parameter based on the hydraulic conductivity. From these, the soil-water characteristic curve is predicted from van Genuchten’s equation. The simulation results are compared with the experimental results from documented studies, and excellent agreements were observed. Overall, this study provides a new modeling-based approach to predict the hydraulic conductivity function and soil-water characteristic curve of unsaturated soils based on measurement at complete dry or completely saturated conditions. An efficient way to measure these critical unsaturated soil properties will be of benefit in introducing unsaturated soil mechanics into engineering practice.

scholarly journals A numerical study on the effect of salinity on stability of an unsaturated railway embankment under rainfall

2020 ◽  
Vol 195 ◽  
pp. 01004
Author(s):  
Ali Kolahdooz ◽  
Hamed Sadeghi ◽  
Mohammad Mehdi Ahmadi
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Water ◽  
Water Retention ◽  
Numerical Study ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Unsaturated Hydraulic Conductivity ◽  
Influence Of Water ◽  
Dispersive Soils

Dispersive soils, as one of the main categories of problematic soils, can be found in some parts of the earth, such as the eastern-south of Iran, nearby the Gulf of Oman. One of the most important factors enhancing the dispersive potential is the existence of dissolved salts in the soil water. The main objective of this study is to explore the influence of water salinity on the instability of a railway embankment due to rainfall infiltration. In order to achieve this goal, the embankment resting on a dispersive stratum is numerically modeled and subjected to transient infiltration flow. The effect of dispersion is simplified through variations in the soil-water retention curve with salinity. The measured water retention curves revealed that by omitting the natural salinity in the soil-water, the retention capability of the soil decreases; therefore, the unsaturated hydraulic conductivity of the soil stratum will significantly decline. According to the extensive decrease in the hydraulic conductivity of the desalinated materials, the rainfall cannot infiltrate in the embankment and the rainfall mostly runs off. However, in the saline embankment, the infiltration decreases the soil suction; and consequently, the factor of safety of the railway embankment decreases.

scholarly journals Estimation of Unsaturated Hydraulic Conductivity of Granular Soils from Particle Size Parameters

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1826 ◽  
Author(s):  
Ji-Peng Wang ◽  
Pei-Zhi Zhuang ◽  
Ji-Yuan Luan ◽  
Tai-Heng Liu ◽  
Yi-Ran Tan ◽  
...  
Keyword(s):  
Grain Size ◽  
Hydraulic Conductivity ◽  
Water Retention ◽  
Intrinsic Value ◽  
Estimation Method ◽  
Sandy Soils ◽  
Saturated Hydraulic Conductivity ◽  
Water Retention Curve ◽  
Porosity Variation ◽  
Unsaturated Hydraulic Conductivity

Estimation of unsaturated hydraulic conductivity could benefit many engineering or research problems such as water flow in the vadose zone, unsaturated seepage and capillary barriers for underground waste isolation. The unsaturated hydraulic conductivity of a soil is related to its saturated hydraulic conductivity value as well as its water retention behaviour. By following the first author’s previous work, the saturated hydraulic conductivity and water retention curve (WRC) of sandy soils can be estimated from their basic gradation parameters. In this paper, we further suggest the applicable range of the estimation method is for soils with d10 > 0.02mm and Cu < 20, in which d10 is the grain diameter corresponding to 10% passing and Cu is the coefficient of uniformity (Cu=d60d10). The estimation method is also modified to consider the porosity variation effect. Then the proposed method is applied to predict unsaturated hydraulic conductivity properties of different sandy soils and also compared with laboratory and field test results. The comparison shows that the newly developed estimation method, which predicts the relative permeability of unsaturated sands from basic grain size parameters and porosity, generally has a fair agreement with measured data. It also indicates that the air-entry value is mainly relative to the mean grain size and porosity value change from the intrinsic value. The rate of permeability decline with suction is mainly associated with grain size polydispersity.

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