Prediction of Coupled Hydro-Mechanical Behavior of Unsaturated Soils Based on Seasonal Variations in Hydrologic Conditions

2020 ◽  
Author(s):  
Majid Mahmoodabadi ◽  
Lindsey Sebastian Bryson
Keyword(s):  
Mechanical Behavior ◽  
Unsaturated Soil ◽  
Seasonal Variations ◽  
Unsaturated Soils ◽  
Wetting And Drying ◽  
Water Characteristics ◽  
Hydrologic Data ◽  
Prediction Approach ◽  
Hydrologic Conditions

Seasonal variations in hydrologic conditions greatly influence the hydro-mechanical properties of unsaturated soils. There are several models available to estimate shear strength of unsaturated soil under various hydrologic conditions. However, many of these existing models provide little to no data regarding the deformations associated with wetting and drying of unsaturated soils. The incremental hydro-mechanical behavior for an unsaturated soil is generally described by a constitutive framework. In this study, a modified-Sheng, Fredlund and Gens (SFG) soil constitutive model was utilized with in-situ hydrologic data to simulate fully coupled mechanical behavior for an unsaturated slope over different hydrologic events. This paper also presents a hydrological prediction approach to estimate hydrologic characteristics of unsaturated soils over several wetting and drying events using only the soil-water characteristics parameters of the main drying curve. The proposed approach provides a possibility of describing long-term hydrologic behavior of unsaturated soils by means of limited amount of in-situ hydrologic data. The outcome of this study provides geotechnical engineers with a capability of estimating deformational behavior of unsaturated soils under various real-time rainfall/evapotranspiration conditions and implementing more effective emergency planning.

scholarly journals Novel rapid measurement system of undisturbed soils water characteristics curve utilizing the continuous pressurization method

2019 ◽  
Vol 92 ◽  
pp. 07008 ◽  
Author(s):  
Adel Alowaisy ◽  
Noriyuki Yasufuku ◽  
Ryohei Ishikura ◽  
Masanori Hatakeyama ◽  
Shuu Kyono
Keyword(s):  
Soil Water ◽  
Unsaturated Soils ◽  
Natural Soil ◽  
Undisturbed Soil ◽  
Water Characteristics ◽  
Undisturbed Samples ◽  
In Situ Conditions ◽  
Undisturbed Soils ◽  
Short Time

Through this paper, a sampling methodology and a novel full automatic system adopting the continuous pressurization method which is capable of determining the Soil Water Characteristics Curve (SWCC) for both remoulded and undisturbed samples in a very short time were developed. The proposed system was validated by comparing the SWCCs of standard testing soils obtained using the developed system to the SWCCs obtained using a conventional method. Remoulded and undisturbed natural soil samples were tested, where the degree of disturbance influence on the obtained SWCC was discussed. In addition, the undisturbed samples containing moulds material influence on the obtained SWCC was investigated. It was found that remoulded samples do not properly represent the in-situ conditions with significant error that should be carefully considered when conducting analysis and proposing countermeasures against unsaturated soils related Geo-disasters. In addition, the material which the containing mould is made from has minor influence on the obtained SWCC which can be neglected. Finally, it can be concluded that the developed undisturbed soil water characteristics curve obtaining system is direct, rapid, reliable and simple. In addition, the proposed undisturbed sampling and testing methodology can be used to accurately evaluate the spatial variations of the SWCC regardless the heterogeneity of the soil profile.

Experiment Research and Design of a Field Test Device for Permeability of Pore Air of Unsaturated Soils

2012 ◽  
Vol 170-173 ◽  
pp. 256-260
Author(s):  
Song Xu ◽  
Fu You Zhang ◽  
Jun Pin Yuan ◽  
Hong Wei Chen ◽  
Ming Gu
Keyword(s):  
Field Test ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Test Field ◽  
Experiment Research ◽  
Test Device ◽  
Relationship Of ◽  
The Relationship ◽  
Research And Design

Permeability of pore air is one of the main basic characters of unsaturated soil. Measuring it accurately is important in anti-seepage design. In this paper, a new kind of device was invented that could test permeability of pore air of unsaturated soil in situ quickly and accurately. With this apparatus, the relationship of air permeability coefficient with various dry densities and saturation of ground soils were obtained in a reservoir. Compared with routine indoor test, field test can decrease the disturbance to the soil and the result is more accurately.

scholarly journals Numerical study on bearing capacity of a pile group next to a slope in unsaturated soils

2020 ◽  
Vol 195 ◽  
pp. 01006
Author(s):  
Amirreza Pourfatollah ◽  
Ali Pirjalili ◽  
Aliakbar Golshani
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Numerical Study ◽  
Pile Group ◽  
Soil Strength ◽  
Strength Parameters ◽  
Water Characteristics ◽  
Soil Shear Strength

The bearing capacity of a pile group mostly depends on parameters of the soil shear strength affected by the soil-water characteristics, especially in unsaturated soils. The soil shear strength is entirely affected by hydraulic stresses in unsaturated soil, such as precipitation and evaporation. Further, the bearing capacity of the pile installed on unsaturated soil depends on hydraulic stresses applied to the soil. Furthermore, slope vicinity may cause a severe decline in the pile bearing capacity. The present study aimed to investigate a pile group in unsaturated soil adjacent to a slope and analyzed the effect of the rainfall on the soil strength parameters. Thus, a numerical study has been performed using a finite difference software,i.e., FLAC2D. Besides, to investigate the model in a real situation, the intensity and duration of rainfall are considered to evaluate changes in hydraulic stresses. Finally, the results show that the rainfall causes a considerable decrease in soil strength parameters in unsaturated soil, leading to the reduction of the pile group bearing capacity and slope stability.

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 Numerical Implementation of a Hydro-Mechanical Coupling Constitutive Model for Unsaturated Soil Considering the Effect of Micro-Pore Structure

2021 ◽  
Vol 11 (12) ◽  
pp. 5368
Author(s):  
Guoqing Cai ◽  
Bowen Han ◽  
Mengzi Li ◽  
Kenan Di ◽  
Yi Liu ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Mechanical Behavior ◽  
Pore Structure ◽  
Unsaturated Soil ◽  
Fortran Program ◽  
Numerical Implementation ◽  
Numerical Application ◽  
Integration Algorithm ◽  
Mechanical Coupling ◽  
Numerical Program

An unsaturated soil constitutive model considering the influence of microscopic pore structure can more accurately describe the hydraulic–mechanical behavior of unsaturated soil, but its numerical implementation is more complicated. Based on the fully implicit Euler backward integration algorithm, the ABAQUS software is used to develop the established hydro-mechanical coupling constitutive model for unsaturated soil, considering the influence of micro-pore structure, and a new User-defined Material Mechanical Behavior (UMAT) subroutine is established to realize the numerical application of the proposed model. The developed numerical program is used to simulate the drying/wetting cycle process of the standard triaxial specimen. The simulation results are basically consistent with those calculated by the Fortran program, which verifies the rationality of the developed numerical program.

In Situ Characterization of the Mechanical Behavior of Gecko's Spatulae by Atomic Force Microscopy

2013 ◽  
Vol 22 ◽  
pp. 85-93
Author(s):  
Shuang Yi Liu ◽  
Min Min Tang ◽  
Ai Kah Soh ◽  
Liang Hong
Keyword(s):  
Mechanical Behavior ◽  
Hierarchical Level ◽  
Intrinsic Properties ◽  
In Situ Characterization ◽  
Force Microscopy ◽  
Atomic Force ◽  
Theoretical Predictions ◽  
Multi Mode

In-situ characterization of the mechanical behavior of geckos spatula has been carried out in detail using multi-mode AFM system. Combining successful application of a novel AFM mode, i.e. Harmonix microscopy, the more detail elastic properties of spatula is brought to light. The results obtained show the variation of the mechanical properties on the hierarchical level of a seta, even for the different locations, pad and stalk of the spatula. A model, which has been validated using the existing experimental data and phenomena as well as theoretical predictions for geckos adhesion, crawling and self-cleaning of spatulae, is proposed in this paper. Through contrast of adhesive and craw ability of the gecko on the surfaces with different surface roughness, and measurement of the surface adhesive behaviors of Teflon, the most effective adhesion of the gecko is more dependent on the intrinsic properties of the surface which is adhered.

Measurement of Soil Suction and Soil-Water Characteristics of Bentonite-Sand Mixtures

2010 ◽  
Author(s):  
Pan Hu ◽  
Qing Yang ◽  
Maotian Luan
Keyword(s):  
Soil Water ◽  
Vapor Phase ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Phase Method ◽  
Soil Suction ◽  
Compacted Bentonite ◽  
Water Characteristics ◽  
Wide Range ◽  
High Level

The soil-water characteristic curve (SWCC) is a widely used experimental means for assessing fundamental properties of unsaturated soils for a wide range of soil suction values. The study of SWCC is helpful because some properties of unsaturated soils can be predicted from it. Nowadays, much attention has been paid to the behaviours of highly compacted bentonite-sand mixtures used in engineering barriers for high level radioactive nuclear waste disposal. It is very important to study the various performances of bentonite-sand mixtures in order to insure the safety of high-level radioactive waste (HLW) repository. After an introduction to vapor phase method and osmotic technique, a laboratory study has been carried out on compacted bentonite-sand mixtures. The SWCC of bentonite-sand mixtures has been obtained and analyzed. The results show that the vapor phase method and osmotic technique is suitable to the unsaturated soils with high and low suction.

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