scholarly journals Analysis of Rainfall Infiltration Velocity in Unsaturated Soils Under Both Continuous and Repeated Rainfall Conditions by an Unsaturated Soil Column Test

2011 ◽  
Vol 21 (2) ◽  
pp. 133-145 ◽  
Author(s):  
Kyu-Bo Park ◽  
Byung-Gon Chae ◽  
Hyuck-Jin Park
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Soil Column ◽  
Rainfall Infiltration ◽  
Column Test

Soil Strength Reduction Method Induced by Variation of Water Content

2012 ◽  
Vol 170-173 ◽  
pp. 847-852
Author(s):  
Peng Ming Jiang ◽  
Zhong Lei Yan ◽  
Peng Li
Keyword(s):  
Slope Stability ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Strength Reduction ◽  
Actual State ◽  
Soil Slope ◽  
Simple Method ◽  
The Common ◽  
The Stability

As the complexity of unsaturated soil theory, and it must have a long test period when we study the unsaturated soils, so the conventional design analysis software does not provide such analysis, so we can imagine that such a slope stability analysis does not accurately reflect the actual state of the slope. Based on the known soil moisture content，this paper use the soil water characteristic curve and strength theory of unsaturated soil to calculate the strength reduction parameters of soil which can calculate the stability of the soil slope when using the common calculation method. It is noticeable that this method can be extended and applied if we establish regional databases for this simple method, and these databases can improve the accuracy of the calculation of slope stability.

scholarly journals A method for predicting the factor of safety of an infinite slope based on the depth ratio of the wetting front

2015 ◽  
Vol 3 (1) ◽  
pp. 791-836 ◽  
Author(s):  
B.-G. Chae ◽  
J.-H. Lee ◽  
H.-J. Park ◽  
J. Choi
Keyword(s):  
Steady State ◽  
Slope Stability ◽  
Unsaturated Soil ◽  
Landslide Susceptibility ◽  
Shallow Landslides ◽  
Rainfall Infiltration ◽  
Wetting Front ◽  
Operating Characteristics ◽  
Infinite Slope ◽  
Depth Ratio

Abstract. Most landslides in Korea are classified as shallow landslides with an average depth of less than 2 m. These shallow landslides are associated with the advance of a wetting front in the unsaturated soil due to rainfall infiltration, which results in an increase in water content and a reduction in the matric suction in the soil. Therefore, this study presents a modified equation of infinite slope stability analysis based on the concept of the saturation depth ratio to analyze the slope stability change associated with the rainfall on a slope. A rainfall infiltration test in unsaturated soil was performed using a column to develop an understanding of the effect of the saturation depth ratio following rainfall infiltration. The results indicated that the rainfall infiltration velocity due to the increase in rainfall in the soil layer was faster when the rainfall intensity increased. In addition, the rainfall infiltration velocity tends to decrease with increases in the unit weight of soil. The proposed model was applied to assess its feasibility and to develop a regional landslide susceptibility map using a Geographic Information System (GIS). For that purpose, the spatial databases for input parameters were constructed and landslide locations were obtained. In order to validate the proposed approach, the results of the proposed approach were compared with the landslide inventory using ROC (Receiver Operating Characteristics) graph. In addition, the results of the proposed approach were compared with the previous approach used steady state hydrological model. Consequently, the approach proposed in this study displayed satisfactory performance in classifying landslide susceptibility and showed better performance than the steady state approach.

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.

Examination of the Penetration of Enteric Viruses in Soils under Simulated Conditions in the Laboratory

1985 ◽  
Vol 17 (10) ◽  
pp. 197-199 ◽  
Author(s):  
P. H. Jørgensen
Keyword(s):  
Sewage Sludge ◽  
Unsaturated Soil ◽  
Sandy Loam ◽  
Soil Column ◽  
Enteric Viruses ◽  
Soil Surface ◽  
Coxsackievirus B3 ◽  
Soil Columns ◽  
Sand Column ◽  
Loam Soil

In two different unsaturated soil columns percolated with artificial rainwater under simulated aerated conditions, transport of coxsackievirus B3 and adenovirus 1 below 3.5 cm under the soil surface could not be demonstrated. The viruses were applied to the columns as seeded sewage sludge. Under saturated conditions transport of water-suspended coxsackievirus B3 was faster in a soil column with sandy loam soil than in a diluvial sand column.

scholarly journals Determination of transport parameters for heavy metal in residual compacted soil using two methodologies

2006 ◽  
Vol 33 (7) ◽  
pp. 912-917
Author(s):  
Izabel Christina Duarte Azevedo ◽  
Cleidimar Rejane Nascentes ◽  
Antonio Teixeira de Matos ◽  
Roberto Francisco de Azevedo
Keyword(s):  
Heavy Metals ◽  
Dispersion Coefficient ◽  
Soil Column ◽  
Optimization Procedure ◽  
Retardation Factor ◽  
Hydrodynamic Dispersion ◽  
Column Test ◽  
Transport Parameters ◽  
Compacted Soil ◽  
Cumulative Mass

Values of the hydrodynamic dispersion coefficient and retardation factor obtained using the traditional and cumulative mass methods of column test analysis for zinc, manganese, and cadmium in a compacted soil are compared. The soil under study is from the B horizon of a residual gneissic tropical soil used for construction of the liner for the sanitary landfill in the District of Visconde do Rio Branco, Minas Gerais (MG), Brazil. To evaluate the behavior of landfill leachate heavy metals through the soil, soil column tests were performed on samples of compacted soil. A computational program that uses an optimization procedure to generate values of the hydrodynamic dispersion coefficient and retardation factor was developed to facilitate interpretation of the results obtained by the cumulative mass method. Values of the retardation factor and hydrodynamic dispersion coefficient were not influenced by the method of determination, even when a reduced number of effluent samples was used by the cumulative mass method. The use of the cumulative mass method, based on a reduced number of pore volumes, reduces the time and cost involved in the tests.Key words: heavy metals, column test, cumulative mass method.

Modified state-surface approach to the study of unsaturated soil behavior. Part I: Basic concept

2009 ◽  
Vol 46 (5) ◽  
pp. 536-552 ◽  
Author(s):  
Xiong Zhang ◽  
Robert L. Lytton
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Stress Path ◽  
Complex Stress ◽  
Soil Behavior ◽  
Elastic Surface ◽  
Surface Approach ◽  
Basic Model ◽  
Plastic Hardening ◽  
Complex Stress Path

The traditional state-surface approach to the study of unsaturated soil behavior is becoming much less popular these days, as it uses unique constitutive surfaces to represent unsaturated soil behavior. This approach is essentially a nonlinear elastic formation and cannot be used to explain complex stress-path dependency for unsaturated soils. In this paper, a modified state-surface approach (MSSA) is proposed to represent unsaturated soil behavior under isotropic stress conditions in which a conventional void-ratio state surface is considered to be made up of an elastic surface and a plastic hardening surface. The plastic hardening surface remains stationary at all times, whereas the elastic surface remains unchanged when the soil experiences elastic deformation and moves downward when there is plastic hardening occurrence. Using the MSSA, the loading–collapse (LC) and the suction increase (SI) yield curves in the Barcelona basic model (BBM) are derived. The prediction of three typical cases of soils under isotropic conditions and experimental results using the proposed approach confirmed its feasibility, simplicity, and potential for the study of unsaturated soil behavior.

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