To see the other types of publications on this topic, follow the link: Unsatured soil.
Journal articles on the topic 'Unsatured soil'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Unsatured soil.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Grünberger, O., J. L. Michelot, L. Bouchaou, P. Macaigne, Y. Hsissou, and C. Hammecker. "Capillary rise quantification by field injection of artificial deuterium and laboratory soil characterization." Hydrology and Earth System Sciences Discussions 7, no. 5 (October 5, 2010): 7757–78. http://dx.doi.org/10.5194/hessd-7-7757-2010.
Full textAbstract:
Abstract. In arid contexts, water rises from the saturated level of a shallow aquifer to the drying soil surface where evaporation takes place. This process plays important roles in terms of plant survival, salt balance and aquifer budget. A new field quantification method of this capillary rise flow is proposed using micro-injections (6 μL) of deuterium-enriched solution (δ value of 63 000‰ vs. V-SMOW) into unsatured soil at 1 m depth. Evaluation of peak displacement from a profile sampling 35 days later, delivered estimates that were compared with outputs of numerical simulation based on laboratory hydrodynamic measurements. A rate of 3.7 cm y−1 was observed in a Moroccan site where the aquifer level was 2.44 m deep. This value was higher, than other estimates based on natural diffusion with the same depth of aquifer, but lower than the estimates established using integration of van Genutchen closed-form functions for soil hydraulic conductivity and retention curve.
2
Fredlund, Delwyn G. "The 1999 R.M. Hardy Lecture: The implementation of unsaturated soil mechanics into geotechnical engineering." Canadian Geotechnical Journal 37, no. 5 (October 1, 2000): 963–86. http://dx.doi.org/10.1139/t00-026.
Full textAbstract:
The implementation of unsaturated soil mechanics into geotechnical engineering practice requires that there be a paradigm shift from classical soil mechanics methodology. The primary drawback to implementation has been the excessive costs required to experimentally measure unsaturated soil properties. The use of the soil-water characteristic curve has been shown to be the key to the implementation of unsaturated soil mechanics. Numerous techniques have been proposed and studied for the assessment of the soil-water characteristic curves. These techniques range from direct laboratory measurement to indirect estimation from grain-size curves and knowledge-based database systems. The soil-water characteristic curve can then be used for the estimation of unsaturated soil property functions. Theoretically based techniques have been proposed for the estimation of soil property functions such as (i) coefficient of permeability, (ii) water storage modulus, and (iii) shear strength. Gradually these estimations are producing acceptable procedures for geotechnical engineering practices for unsaturated soils. The moisture flux ground surface boundary condition is likewise becoming a part of the solution of most problems involving unsaturated soils. The implementation process for unsaturated soils will still require years of collaboration between researchers and practicing geotechnical engineers.Key words: unsaturated soil mechanics, soil suction, unsaturated soil property functions, negative pore-water pressure, matric suction, soil-water characteristic curve.
3
Alzaidy, Mohammed Nawaf Jirjees. "A Theoretical Study of Some Unsaturated Properties for Different Soils." Journal of University of Babylon for Engineering Sciences 26, no. 9 (November 1, 2018): 149–65. http://dx.doi.org/10.29196/jubes.v26i9.1720.
Full textAbstract:
Soil–water characteristic curves (SWCC) can be defined as the relationship between the water content and suction of an unsaturated soil. It considered a basic relation to explanation of the engineering behaviour of unsaturated soil such as hydraulic conductivity and shear strength, So the study of SWCC is useful to reduce the time and cost of unsaturated soil testing for different engineering purposes. An approach model has been used to predict the SWCC for different soils. The influence of the soils on SWCC shape, the unsaturated hydraulic conductivity and shear strength parameters have been studied in this paper using mathematical models. The results of SWCC show that suction of clay soil is bigger than sandy soil, while the clayey silt soils exhibit an intermediate behaviour at same water content. The values of unsaturated shear strength are increasing while the unsaturated hydraulic conductivity is decreasing with increasing soil suction. This behaviour of the last two parameters with soil suction should be taken in consideration for engineering purposes.
4
Koyluoglu, U. "Soil mechanics for unsaturated soils." Soil Dynamics and Earthquake Engineering 12, no. 7 (1993): 449–50. http://dx.doi.org/10.1016/0267-7261(93)90011-f.
Full text
5
Wang, Q., D. E. Pufahl, and D. G. Fredlund. "A study of critical state on an unsaturated silty soil." Canadian Geotechnical Journal 39, no. 1 (February 1, 2002): 213–18. http://dx.doi.org/10.1139/t01-086.
Full textAbstract:
Critical state models for unsaturated soils have been proposed in recent years; however, the proposed models have been based on limited experimental data. Compacted specimens have generally been used for research, and the complications of soil fabric resulting from the compaction procedures have brought difficulties into the interpretation of fundamental soil behavior. There is a need to undertake further laboratory research studies on unsaturated soils, particularly to obtain a fundamental understanding of the shear strength and critical state of unsaturated soils by testing soil specimens with simple soil structures. Suction-controlled triaxial drained shear tests on an unsaturated silt were carried out as part of this research program. Specimens were prepared by gradually consolidating the initially slurried soil. The resulting specimens had a relatively simple soil fabric and stress history. The results showed that applying suction to an initially saturated specimen has a similar influence on the stressstrain behavior and critical state characteristics as does increasing its density by applying a higher confining pressure. The critical state lines for the unsaturated soil corresponding to different soil suctions are parallel to those for the saturated soil on the (q : p' ' ), (v : p' ' ), and (vw : p' ' ) planes.Key words: critical state, shear strength, unsaturated soils, volume change, triaxial testing.
6
Wong, Tai T., Delwyn G. Fredlund, and John Krahn. "A numerical study of coupled consolidation in unsaturated soils." Canadian Geotechnical Journal 35, no. 6 (December 1, 1998): 926–37. http://dx.doi.org/10.1139/t98-065.
Full textAbstract:
This paper first describes the numerical implementation of the coupled formulation for the theory of consolidation of unsaturated soils. The developed computer code is verified using the Mandel-Cryer problem and then is applied to the solution of coupled multidimensional consolidation problems. Using a parametric study, it is demonstrated that, in unsaturated soils, the Mandel-Cryer effect is suppressed and the consolidation process in unsaturated soils is affected significantly by the shape of the soil-water characteristic curve. Finally, the developed model is used to analyze the consolidation of an unsaturated-saturated soil column. Analysis results indicate that the classical "undrained" pore-water pressure response to an externally applied load only occurs in the saturated zone while the pore-water pressure response is subdued in the unsaturated zone. This paper also shows a method of deriving one of the two additional material parameters required for the analysis of unsaturated soils from laboratory test results.Key words: coupled consolidation, unsaturated soils, Mandel-Cryer effect, soil-water characteristic curve.
7
Fredlund, D. G., Anqing Xing, M. D. Fredlund, and S. L. Barbour. "The relationship of the unsaturated soil shear strength to the soil-water characteristic curve." Canadian Geotechnical Journal 33, no. 3 (July 2, 1996): 440–48. http://dx.doi.org/10.1139/t96-065.
Full textAbstract:
The measurement of soil parameters, such as the permeability and shear strength functions, used to describe unsaturate soil behaviour can be expensive, difficult, and often impractical to obtain. This paper proposes a model for predicting the shear strength (versus matric suction) function of unsaturated soils. The prediction model uses the soil-water characteristic curve and the shear strength parameters of the saturated soil (i.e., effective cohesion and effective angle of internal friction). Once a reasonable estimate of the soil-water characteristic curve is obtained, satisfactory predictions of the shear strength function can be made for the unsaturated soil. Closed-form solutions for the shear strength function of unsaturated soils are obtained for cases where a simple soil-water characteristic equation is used in the prediction model. Key words: soil suction, soil-water characteristic curve, shear strength function, unsaturated soil.
8
Houston, Sandra, and Xiong Zhang. "Review of expansive and collapsible soil volume change models within a unified elastoplastic framework." Soils and Rocks 44, no. 3 (July 8, 2021): 1–30. http://dx.doi.org/10.28927/sr.2021.064321.
Full textAbstract:
Numerous laboratory tests on unsaturated soils revealed complex volume-change response to reduction of soil suction, resulting in early development of state surface approaches that incorporate soil expansion or collapse due to wetting under load. Nonetheless, expansive and collapsible soils are often viewed separately in research and practice, resulting in development of numerous constitutive models specific to the direction of volume change resulting from suction decrease. In addition, several elastoplastic models, developed primarily for collapse or expansion, are modified by add-on, such as multiple yield curves/surfaces, to accommodate a broader range of soil response. Current tendency to think of unsaturated soils as either expansive or collapsible (or, sometimes, stable), has likely contributed to lack of development of a unified approach to unsaturated soil volume change. In this paper, common research and practice approaches to volume change of unsaturated soils are reviewed within a simple macro-level elastoplastic framework, the Modified State Surface Approach (MSSA). The MSSA emerges as a unifying approach that accommodates complex volume change response of unsaturated soil, whether the soil exhibits collapse, expansion, or both. Suggestions are made for minor adjustments to existing constitutive models from this review, typically resulting in simplification and/or benefit to some of the most-used constitutive models for unsaturated soil volume change. In the review of practice-based approaches, the surrogate path method (SPM), an oedometer/suction-based approach, is demonstrated to be consistent with the MSSA framework, broadly applicable for use with expansive and collapsible soils, and yielding results consistent with measured field stress-path soil response.
9
Pham, Hung Q., and Delwyn G. Fredlund. "Volume–mass unsaturated soil constitutive model for drying–wetting under isotropic loading–unloading conditions." Canadian Geotechnical Journal 48, no. 2 (February 1, 2011): 280–313. http://dx.doi.org/10.1139/t10-061.
Full textAbstract:
A rigorous volume–mass constitutive model is proposed for the representation of drying–wetting under isotropic loading–unloading conditions for unsaturated soils. The proposed model utilizes concepts arising from soil physics and geotechnical engineering research and requires readily obtainable soils data for soil properties. The model can be used to predict void ratio and water content constitutive relationships (and therefore degree of saturation) for a wide range of unsaturated soils. Various stress paths (i.e., loading–unloading and drying–wetting) can be simulated, and hysteresis associated with the soil-water characteristic curve is taken into account. Two closed-form equations for the volume–mass constitutive relationships are presented for soils starting from slurry conditions. A number of test results (i.e., from experimental programs reported in the research literature) were used during the verification of the proposed volume–mass constitutive model. The volume–mass constitutive model captures key unsaturated soil conditions such as air-entry value, water-entry value, and residual conditions. The proposed model appears to satisfactorily predict unsaturated soil behavior for soils ranging from low compressible sands to high compressible clays.
10
Menon, Shashank, and Xiaoyu Song. "Coupled Analysis of Desiccation Cracking in Unsaturated Soils through a Non-Local Mathematical Formulation." Geosciences 9, no. 10 (October 2, 2019): 428. http://dx.doi.org/10.3390/geosciences9100428.
Full textAbstract:
The formation of desiccation cracks in unsaturated soils as a discontinuity phenomenon can compromise the integrity of civil infrastructure on unsaturated soils. Because of the singularity at such discontinuities, the mathematical modeling of desiccation cracking is challenging. In this study, we apply a coupled nonlocal peridynamic poroelastic framework to model desiccation cracking in unsaturated soils. The soil skeleton is modeled by a nonlocal peridynamic elastic solid. A peridynamic equivalence of the generalized Darcy’s law is utilized to model unsaturated fluid flow. Cracking is determined by a critical stretch criterion between material points as well as an energy criterion. We present numerical simulations of desiccation cracking in soil bars and thin soil discs for one-dimensional cracking and two-dimensional cracking networks, respectively. The numerical results have demonstrated that the proposed nonlocal mathematical framework is a promising and robust method for modeling desiccation cracking in unsaturated soils.
11
Zhang, Xiong, and Robert L. Lytton. "Modified state-surface approach to the study of unsaturated soil behavior. Part III: Modeling of coupled hydromechanical effect." Canadian Geotechnical Journal 49, no. 1 (January 2012): 98–120. http://dx.doi.org/10.1139/t11-089.
Full textAbstract:
A modified state-surface approach (MSSA) was proposed in the authors’ previous study to investigate volume change of the soil skeleton for unsaturated soils. This paper discussed the coupling effect between volume changes of soil skeleton, water phase, and air phase for unsaturated soils based on the proposed MSSA and experimental results presented by other researchers. The MSSA was further extended to study the coupled hydromechanical behavior for unsaturated soils. Besides void ratio constitutive surface, conventional unique water content and degree of saturation constitutive surfaces were also divided into elastic and plastic regions by loading–collapse (LC) yield curves and simultaneously used to describe the coupled hydromechanical behavior for unsaturated soils. A general theoretic formulation was derived for the simultaneous use of the MSSA under isotropic conditions. Based on the derived formulation, existing elastoplastic models were reviewed, and compatibility and consistency in modeling the mechanical and hydraulic behavior of unsaturated soils were discussed. Afterwards, the results of a number of suction-controlled laboratory isotropic compression tests at different suctions were used to demonstrate the ability of the proposed approach to reproduce the observed soil behavior quantitatively and soil behavior under undrained conditions qualitatively.
12
Camapum de Carvalho, José, and Gilson Gitirana. "Unsaturated soils in the context of tropical soils." Soils and Rocks 44, no. 3 (September 23, 2021): 1–25. http://dx.doi.org/10.28927/sr.2021.068121.
Full textAbstract:
The practice of geotechnical engineering in tropical climate regions must consider the use of unsaturated soil concepts. However, these concepts must also take into account the specific behavior traits of tropical soils, particularly those related to soil aggregation, pore structure, and mineralogy. This paper will initially present considerations on the typical properties of unsaturated tropical soils as well as fundamental concepts. Throughout the article, several engineering problems will be presented alongside reflections on the complex interaction between the numerous variables involved in the modeling and engineering practice of tropical unsaturated soil behavior. The paper addresses issues related to soil formation, chemical and mineral composition, physical properties, tropical soil classification, and structural characteristics of soils. Issues related to compaction and the influence of weathering, geomorphology and bioengineering are also addressed.
13
Liu, Cui Ran, Peng Li He, and Huai Feng Tong. "The Experimental Study of Permeability Coefficient of Unsaturated Soil." Applied Mechanics and Materials 71-78 (July 2011): 1158–62. http://dx.doi.org/10.4028/www.scientific.net/amm.71-78.1158.
Full textAbstract:
Due to the complexity and variability of unsaturated soil, the permeability property of unsaturated soils is clearly different from that of saturated soil. And because the test equipment is more complex and technical requirements are higher and diachronic cycle is longer, the researches related are slow. Using the triaxial apparatus of unsaturated soil, the direct and indirect experiments to study the permeability coefficient of unsaturated silty clay are done. Test results show that the permeability coefficient of unsaturated soil can be done by the indirect method and direct method. Not only the direct measurements of the permeability coefficient of unsaturated soil are realized through this trial, but also the reliability of indirect method is proved.
14
Sheng, Daichao, Delwyn G. Fredlund, and Antonio Gens. "A new modelling approach for unsaturated soils using independent stress variables." Canadian Geotechnical Journal 45, no. 4 (April 2008): 511–34. http://dx.doi.org/10.1139/t07-112.
Full textAbstract:
Although a number of constitutive models for unsaturated soils exist in the literature, some fundamental questions have not been fully answered. There are questions related to (i) the change of the yield stress with soil suction, (ii) modelling slurry soils, and (iii) the smooth transition between saturated and unsaturated soil states. This paper addresses these questions by proposing an alternative modelling approach. The paper first presents a volumetric model for unsaturated soils. This volumetric model is then used to derive the yield surface in the suction – mean stress space. Hysteresis associated with soil-water characteristic curves is then formulated in the same framework of elastoplasticity. It is shown that volume collapse during wetting and plastic shrinkage during initial drying are both direct results of a suction-dependent hardening law. The proposed model seems to be more flexible in modelling different types of unsaturated soils than most models in the literature. The model can be applied to soils that are dried or loaded from initially slurry conditions, for soils that have low to high air-entry values, and for compacted soils as well.
15
Oh, Seboong, Ki Hun Park, Oh Kyun Kwon, Woo Jung Chung, and Kyung Joon Shin. "On the Hypothesis of Effective Stress in Consolidation and Strength for Unsaturated Soils." Applied Mechanics and Materials 256-259 (December 2012): 108–11. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.108.
Full textAbstract:
The hypothesis on effective stress of unsaturated soils is validated by consolidation strength results of triaxial tests for the compacted residual soil. The effective stress can describe the unsaturated soil behavior, which was defined from shear strength or from soil water characteristic curves. Since the effective stress from consolidation agrees with that from the shear strength, the effective stress from soil water retention curve could describe the unsaturated behavior consistently on both consolidation path and stress at failure. The effective stress can describe the entire unsaturated behavior from consolidation to failure.
16
Schnellmann, Reto, Harianto Rahardjo, and Hans R. Schneider. "Controlling parameter for unsaturated soil property functions: validated on the unsaturated shear strength." Canadian Geotechnical Journal 52, no. 3 (March 2015): 374–81. http://dx.doi.org/10.1139/cgj-2013-0278.
Full textAbstract:
Prediction equations for unsaturated soil property functions have become more attractive because laboratory tests of unsaturated soils are time consuming and expensive. To ensure that predicted soil property functions represent soil behaviour reasonably well, appropriate selection of the parameter that controls the performance of these prediction equations becomes imperative. Deduced from the typical desaturation characteristics of a soil, the effective degree of saturation has emerged to be the controlling parameter for unsaturated soil property functions. In this paper, soil suction is considered to become ineffective in affecting unsaturated soil property functions at and beyond the residual state. Comparisons between experimental shear strength data and predicted values obtained using the concept proposed in this study show a good agreement.
17
Zhang, Xiong, and Robert L. Lytton. "Modified state-surface approach to the study of unsaturated soil behavior. Part I: Basic concept." Canadian Geotechnical Journal 46, no. 5 (May 2009): 536–52. http://dx.doi.org/10.1139/t08-136.
Full textAbstract:
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.
18
Lee, In-Mo, Sang-Gyu Sung, and Gye-Chun Cho. "Effect of stress state on the unsaturated shear strength of a weathered granite." Canadian Geotechnical Journal 42, no. 2 (April 1, 2005): 624–31. http://dx.doi.org/10.1139/t04-091.
Full textAbstract:
The effect of stress state on the unsaturated shear strength of a Korean residual soil was studied using modified triaxial tests. Experimental results show that the soil-water characteristic curve and shear strength of this soil are significantly affected by the change of net normal stresses. This effect should be taken into consideration in the model to precisely describe the shear strength envelope of unsaturated soils. Thus, a new model for estimation of unsaturated shear strength is proposed using the soil-water characteristic curve and the saturated shear strength parameters.Key words: prediction model, soil-water characteristic curve, matric suction, triaxial test, unsaturated shear strength.
19
Dong, Shaoyang, Yuan Guo, and Xiong (Bill) Yu. "Method for Quick Prediction of Hydraulic Conductivity and Soil-Water Retention of Unsaturated Soils." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 52 (September 28, 2018): 108–17. http://dx.doi.org/10.1177/0361198118798486.
Full textAbstract:
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.
20
Quevedo, Roberto, Celso Romanel, and Deane Roehl. "Numerical modeling of unsaturated soil behavior considering different constitutive models." MATEC Web of Conferences 337 (2021): 02007. http://dx.doi.org/10.1051/matecconf/202133702007.
Full textAbstract:
Recent advances, not only in fluid flow but also in soil mechanics, have allowed the understanding and forecasting of common engineering problems such as slope stability, soil shrinkage and soil collapse. However, owing to limited access to data or more sophisticated numerical tools, the modeling of soil behavior is usually carried out considering simpler constitutive models which cannot predict some important features of unsaturated soils. This study is focused on the numerical modeling of unsaturated soils, adopting four constitutive models based on theories of elasticity and plasticity. For each model, a numerical simulation of a circular footing resting over a soil that is subject to drying and wetting processes is analyzed. Through the comparison of results, it is possible to highlight the use of more sophisticated constitutive models for unsaturated soil behavior, particularly forecasting the phenomenon of pore collapse during wetting processes.
21
Zhou, Yi Yi, Jie Li, and Wen Hu Li. "Validation of the Volume Change Behavior in SFG Model Using a Soil Consolidation Test and a Soil Water Characteristic Curve Experiment." Advanced Materials Research 446-449 (January 2012): 1918–21. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.1918.
Full textAbstract:
Constitutive modeling in unsaturated soil is always a big challenge in Geo-technique problems. Since Alonso et al suggested the Basic Barcelona Model (BBM) in 1990. Many researchers contribute works on constitutive models in last two decades. The SFG model presented by Sheng, Fredlund and Gens describes the mechanical and hydraulic behaviors of an unsaturated soil accurately. It is currently considered the most reasonable model for unsaturated soil. In this paper, the authors attempts to prove the volume change behavior in SFG model by two basic unsaturated soil experiments in testing two different soils. The experimental data and the fitting processes are provided.
22
Barbour, S. Lee. "Nineteenth Canadian Geotechnical Colloquium: The soil-water characteristic curve: a historical perspective." Canadian Geotechnical Journal 35, no. 5 (October 1, 1998): 873–94. http://dx.doi.org/10.1139/t98-040.
Full textAbstract:
The constitutive relationship between water content or degree of saturation and suction is called the soil-water characteristic curve. The soil-water characteristic curve provides a conceptual framework in which the behavior of unsaturated soils can be understood. A historical review illustrates how the work of early researchers in soil science and geotechnical engineering laid the foundation for our current understanding of this relationship. Key elements of these early studies were a conceptual understanding of the soil-water characteristic curve as a relationship between the mass or volume of water stored within the soil and the energy in the water phase. It was on the basis of this conceptual model that current methods of measuring the soil-water characteristic curve were developed. Interpretative models for the distribution and geometry of the water phase in an unsaturated soil based on the capillary model have provided a useful conceptual model for understanding the effects of soil texture, gradation, void ratio, and compaction on the soil-water characteristic curve. The capillary model has also provided the foundation for recently developed techniques to predict the functional relationship between degree of saturation and shear strength, coefficient of permeability, coefficient of diffusion, and adsorption for unsaturated soils.Key words: unsaturated soils, soil-water characteristic curve, suction, shear strength, permeability, contaminant transport.
23
Tang, Liansheng, Haitao Sang, Liqun Jiang, Yinlei Sun, and Muhammad Ashraf. "New Progress in the Study of Intergranular Suction and Shear Strength of Unsaturated Soil." Earth Sciences Research Journal 20, no. 1 (April 30, 2016): 1–13. http://dx.doi.org/10.15446/esrj.v20n1.54139.
Full textAbstract:
<p>The suction between soil particles is the basis and core problem in the study of unsaturated soil. However, is the suction between soil particles just the matrix suction, which has been widely used since the discipline of unsaturated soil mechanics was established. In fact, the concept of matrix suction is from soil science and reflects the water- absorbing capacity of the soil. Matrix suction characterizes the interaction between soil particles and pore water rather than the interactions between soil particles, which are not in conformity with the principle of the effective stress of soils. The suction of unsaturated soil, in essence, is the intergranular suction composed of absorbed suction and structural suction. In this paper, first, the basic concepts of absorbed suction and structural suction were briefly introduced. Then, with soil mechanics, powder science, crystal chemistry, granular material mechanics and other related disciplines of knowledge for reference, the quantitative calculation formulas were theoretically deduced for the absorbed suction for equal-sized and unequal-sized unsaturated soil particles with arbitrary packing and the variable structural suction for equal-sized unsaturated soil particles with arbitrary packing and unequal-sized unsaturated soil particles with close tetrahedral packing. The factors that influence these equations were discussed. Then, the shear strength theory of unsaturated soil was established based on the theory of intergranular suction through the analysis of the effective stress principle of unsaturated soil. This study demonstrates that the shear strength of unsaturated soil consists of three parts: the effective, cohesive force, the additional strength caused by external loads and the strength caused by intergranular suction. The contribution of the three parts to the shear strength of unsaturated soil depends on the following influence factors: soil type, confining pressure, water content and density. Therefore, these factors must be comprehensively considered when determining the strength of unsaturated soil.</p>
24
Murray, Edward J. "An equation of state for unsaturated soils." Canadian Geotechnical Journal 39, no. 1 (February 1, 2002): 125–40. http://dx.doi.org/10.1139/t01-087.
Full textAbstract:
The enthalpy within a soil system under equilibrium conditions is investigated theoretically. Terzaghi's effective stress equation for a saturated soil is first examined and the approach extended to determine the enthalpy associated with the air, water, and solid phases, and the interactions between the phases, in an unsaturated soil. An equation of state is developed which links the stress state variables (p ua) and (ua uw) to the specific volume (v) and specific water volume (vw) and thus to the volumes of the phases. The equation is shown to provide a logical interpretation of the average volumetric "coupling" stress p'c within unsaturated soils which highlights the significance of the dual stress regime and bimodal structure. The new equation is compared with previously reported experimental data on kaolin and a lateritic gravel. The agreement is good and it provides insight into unsaturated soil strength and deformation behaviour and clarifies various previously identified anomalies.Key words: partial saturation, unsaturated soils, thermodynamics, effective stress, equation of state, critical state.
25
Werner, S. F., C. T. Driscoll, P. M. Groffman, and J. B. Yavitt. "Landscape patterns of soil oxygen and atmospheric greenhouse gases in a northern hardwood forest landscape." Biogeosciences Discussions 8, no. 6 (November 8, 2011): 10859–93. http://dx.doi.org/10.5194/bgd-8-10859-2011.
Full textAbstract:
Abstract. The production and consumption of the greenhouse gases, carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), are controlled by redox reactions in soils. Together with oxygen (O2), seasonal and spatial dynamics of these atmospheric gases can serve as robust indicators of soil redox status, respiration rates, and nitrogen cycling. We examined landscape patterns of soil oxygen and greenhouse gas dynamics in Watershed 3 at the Hubbard Brook Experimental Forest, NH, USA. We analyzed depth profiles of soil O2, CO2, N2O, and CH4 approximately bimonthly for one year. Soil gas depth profiles were obtained from several different soil types encompassing a range of topographic positions, drainage classes, and organic matter content. Soil O2 was a good predictor of greenhouse gas concentrations. Unsaturated soils always had O2 concentrations >18 %, while saturated soils had O2 ranging from 0 to 18 %. For unsaturated soils, changes in CO2 were nearly stoichiometric with O2. High concentrations of CH4 (>10 μL L−1) were typically associated with saturated soils; CH4 was typically below atmospheric concentrations (<1.8 μL L−1) in unsaturated soils. High concentrations of N2O (>5000 nL L−1) were found only in well-aerated soils after summer rainfall events and in marginally-anoxic soils; N2O was consumed (<200 nL L−1) under anoxic conditions. The production and consumption of greenhouse gases were linked to functionally distinct biogeochemical zones of variable redox conditions (hotspots), which exhibit dynamic temporal patterns of redox fluctuations (hot moments). These soil redox hot phenomena were temporally driven by climate and spatially organized by soil type (reflective of topographic position) further constrained by subsurface hydrology.
26
Pourfatollah, Amirreza, Ali Pirjalili, and Aliakbar Golshani. "Numerical study on bearing capacity of a pile group next to a slope in unsaturated soils." E3S Web of Conferences 195 (2020): 01006. http://dx.doi.org/10.1051/e3sconf/202019501006.
Full textAbstract:
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.
27
Huang, Shangyan, S. L. Barbour, and D. G. Fredlund. "Development and verification of a coefficient of permeability function for a deformable unsaturated soil." Canadian Geotechnical Journal 35, no. 3 (June 1, 1998): 411–25. http://dx.doi.org/10.1139/t98-010.
Full textAbstract:
The modelling of flow through saturated/unsaturated soils has become routine in geotechnical and geo-environmental engineering. The analysis requires that the coefficient of permeability for an unsaturated soil be defined. The coefficient of permeability can be estimated based on currently available procedures. However, each procedure has limitations and consequently cares should be taken in the selection of a proper procedure. The coefficient of permeability of a saturated soil is a function of void ratio. The coefficient of permeability of an unsaturated soil of constant volume, is a function of the degree of saturation. However, soil is deformable and both the degree of saturation and the void-ratio influence the coefficient of permeability of a compressible, unsaturated soil. In this paper, the literature pertaining to the coefficient of permeability function for an unsaturated soil of constant volume and the coefficient of permeability for a deformable saturated soil are reviewed. A new coefficient of permeability function for a deformable unsaturated porous medium is then developed. A series of triaxial permeameter tests on unsaturated silty sand are described and the results from the experimental program are analyzed using the general form of the newly developed permeability function. The results show good agreement between the experimental data and the proposed model for a deformable unsaturated porous medium.Key words: unsaturated soil, coefficient of permeability, permeability function, soil-water characteristic curve, triaxial permeameter, deformable porous medium.
28
Wang, Dong Lin. "Experimental Study on Soil Water Characteristic Curve of Compacted Unsaturated Soil." Advanced Materials Research 168-170 (December 2010): 1285–88. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.1285.
Full textAbstract:
Soil water characteristic curve is one of important topics of unsaturated soils. Pressure plate extractor and GDS unsaturated triaxial apparatus are used to study influencing factors including types of soils and net mean stress. Through method of least-squares, Fredlund five-parameter model were employed to fit soil-water characteristic curves. The results show that model provided a satisfactory fit to the experimental data. Through an analysis of influencing factors, we find that not only physical condition of samples but also external stress condition can affect the shape of soil water characteristic curve.
29
Bulolo, Sam, and Eng Choon Leong. "Modelling shear strength of compacted soils." E3S Web of Conferences 92 (2019): 15007. http://dx.doi.org/10.1051/e3sconf/20199215007.
Full textAbstract:
Compacted soils constitute most engineering projects such as earth dams, embankments, pavements, and engineered slopes because of their high shear strength and low compressibility. The shear strength of compacted soils is a key soil parameter in the design of earth structures but it is seldom determined correctly due to their unsaturated state. The shear strength of compacted soils can be better evaluated under the framework of unsaturated soil mechanics. Saturated and unsaturated tests were conducted on compacted specimens using conventional direct shear apparatus under constant water content condition. Tests were conducted at different water contents and net normal stresses. The main objective of this study is to develop a shear strength model for compacted soils. Initial matric suction was measured before the test using the filter paper method. The two-stress state variables together with the extended Mohr-Coulomb failure criterion for unsaturated soils were used to obtain a lower bound model of the shear strength. The model was demonstrated using published data.
30
Schwaerzel, K., and H. P. Bohl. "An easily installable groundwater lysimeter to determine waterbalance components and hydraulic properties of peat soils." Hydrology and Earth System Sciences 7, no. 1 (February 28, 2003): 23–32. http://dx.doi.org/10.5194/hess-7-23-2003.
Full textAbstract:
Abstract. A simple method for the installation of groundwater lysimeters in peat soils was developed which reduces both time and financial effort significantly. The method was applied on several sites in the Rhinluch, a fen peat land 60 km northwest of Berlin, Germany. Over a two-year period, upward capillary flow and evapotranspiration rates under grassland with different groundwater levels were measured. The installation of tensiometers and TDR probes additionally allowed the in situ determination of the soil hydraulic properties (water retention and unsaturated hydraulic conductivity). The results of the measurements of the unsaturated hydraulic conductivity demonstrate that more than one single method has to be applied if the whole range of the conductivity function from saturation to highly unsaturated is to be covered. Measuring the unsaturated conductivity can be done only in the lab for an adequately wide range of soil moisture conditions. Keywords: peat soils, soil hydraulic properties, evapotranspiration, capillary flow, root distribution, unsaturated zone
31
Xie, Xianqi, Yingkang Yao, Jun Liu, Peining Li, and Gui Yang. "Mechanical Behavior of Unsaturated Soils Subjected to Impact Loading." Shock and Vibration 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/4703981.
Full textAbstract:
This paper presents an experimental study on unsaturated soils. A designed test setup was used and the impact loading was applied with a drop hammer. The experimental results show that the soil properties, including water content, density, void ratio, and saturation, changed because of impact loading, and these variations of the soil properties affected the matrix suctions of the unsaturated soils. The impact hole depth increased with the increasing impact energy and gradually reached a critical value. The dynamic stress in soil increased with the increased impact loading. The results obtained in this work can be applied to optimize the effective reinforcement region of soils in the dynamic compaction construction.
32
Lu, Chuan Yin, and Sheng Zhu. "Overview of the Development of Consolidation Theory of Unsaturated Soils." Advanced Materials Research 734-737 (August 2013): 2318–23. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.2318.
Full textAbstract:
The consolidation theory and test results of unsaturated soils were summarized in detail in this article, which include the recent development. And some existent difficulties and problems for consolidation theory of unsaturated soil were also summarized. The consolidation theory of unsaturated soils have well applicable future, but the theory is not mature and need the investigators’ further research.
33
TAO, GAOLIANG, XIAOKANG WU, HENGLIN XIAO, QINGSHENG CHEN, and JIANCHAO CAI. "A UNIFIED FRACTAL MODEL FOR PERMEABILITY COEFFICIENT OF UNSATURATED SOIL." Fractals 27, no. 01 (February 2019): 1940012. http://dx.doi.org/10.1142/s0218348x19400127.
Full textAbstract:
Due to the significant challenges in the measurements, evaluation of permeability coefficient for unsaturated soil is of immense importance for investigating the seepage and hydro-mechanical coupling problems of unsaturated soil. However, the predictions of existing typical models reveal significance divergence for permeability coefficient of unsaturated soils even under identical conditions. In particular, the existing models are greatly restricted in their practical application due to their complexity in the form of integral expressions that require significant computational effort. Here, a simplified unified model is presented to estimate the relative permeability coefficient. First, a fractal-form of soil–water characteristic curve (SWCC) is derived from fractal theory. Then, on the basis of the proposed SWCC models, the classical models (i.e. Childs and Collis-George (CCG) model, Burdine model, Mualem model and Tao and Kong model, respectively) for evaluating the permeability coefficient of unsaturated soil are converted to be presented in fractal forms. It is interestingly found that the fractal forms of these models are enormously similar. Based on these observations, a simplified unified fractal model for the relative permeability coefficient of unsaturated soil is proposed, where only two parameters (i.e. fractal dimension and air-entry value) are included, thereby significantly reducing the computational efforts. The detailed procedure for determining model parameters is elaborated. The accuracy of this model is verified by comparing its predictions with the experimental data for over 12 types of unsaturated soils. The results highlight that, compared with existing models, the proposed model would be much more efficiently used for estimating the relative permeability coefficient of unsaturated soils, thereby facilitating its application for investigating the associated seepage and hydro-mechanical coupling problems in practice.
34
Syarifudin, Achmad, and Alfrendo Satyanaga. "Variability of Bimodal Soil-Water Characteristic Curves under Different Confining Pressures." Applied and Environmental Soil Science 2021 (June 5, 2021): 1–10. http://dx.doi.org/10.1155/2021/5569491.
Full textAbstract:
Soils with two subcurves of Soil-Water Characteristic Curve (SWCC) (dual porosity soils) might be found within various residual soils. Soils located in different depths have different confining pressure. Residual soils are found in the unsaturated zones due to the deep groundwater table. There is a linear correlation between the hydraulic properties of the soil in the unsaturated area and that of its unsaturated properties. This study aims to examine the influence of the confining pressure towards the SWCC of dual porosity soil. The scope of this study involves measurements of the drying and wetting SWCC using Tempe cells, pressure plates, and an advanced triaxial apparatus. In this study, the mathematical equations were developed to explain the effect of confining pressure on SWCC. The experimental results indicated that the dual porosity soil exhibits bimodal characteristics for the drying curve of SWCC and it exhibits unimodal characteristics for the wetting curve of SWCC. As the confining pressure increases, the air entry values, the inflection points, and the standard deviation of drying SWCC increase. In addition, the hysteresis of SWCC is becoming smaller with the increasing confining pressure.
35
Bruno, Agostino Walter, Domenico Gallipoli, Mohamed Rouainia, and Marti Lloret-Cabot. "A single-stress model for the prediction of yielding of unsaturated cemented soils under isotropic loads." E3S Web of Conferences 195 (2020): 02001. http://dx.doi.org/10.1051/e3sconf/202019502001.
Full textAbstract:
This paper presents a bounding surface model predicting the combined effects of cementation and partial saturation on the mechanical behaviour of soils subjected to isotropic loading. The loss of cementation caused by loading, wetting or drying of a normally consolidated soil is described by a “cementation bonding function”. This states that, under virgin conditions, the ratio between cemented and uncemented void ratios monotonically decreases with increasing levels of scaled stress. The scaled stress is the variable governing the intrinsic behaviour of the soil under both saturated and unsaturated conditions. Combination of the cementation bounding function with a previously proposed model for unsaturated soil behaviour leads to the formulation of a “cemented unified normal compression line” (CUNCL). This describes the virgin behaviour of both cemented and uncemented soils under saturated and unsaturated conditions. Progressive yielding is modelled by assuming that the slope of the generic loading curve tends towards the slope of the CUNCL as the soil state moves from overconsolidated to virgin conditions. The model has been calibrated and validated against existing experimental data demonstrating a good ability to predict the void ratio of cemented soils during isotropic loading, unloading and wetting under both saturated and unsaturated conditions.
36
Li, Lin, Xiong Zhang, Gang Chen, and Robert Lytton. "Measuring unsaturated soil deformations during triaxial testing using a photogrammetry-based method." Canadian Geotechnical Journal 53, no. 3 (March 2016): 472–89. http://dx.doi.org/10.1139/cgj-2015-0038.
Full textAbstract:
When characterizing an unsaturated soil using the triaxial test apparatus, it is required to measure the soil deformation during loading. Recently, a photogrammetry-based method has been developed for total and localized volume change measurements on unsaturated soils during triaxial testing. In this study, more in-depth discussions on the photogrammetry-based method are addressed, such as system setup, the measurement procedure, accuracy self-check, data post-processing, and differences from conventional image-based methods. Also, an application of the photogrammetry-based method on unsaturated soil deformation measurements is presented through a series of undrained triaxial tests with different loading paths. After testing, three-dimensional (3D) models of the tested soils at different loading steps were constructed based on the 3D coordinates of measurement targets on the soil surface. Clear barreling processes for soils during deviatoric loading were observed through the constructed 3D models at different axial strain levels. Soil volume changes and volumetric strain nonuniformities during isotropic and deviatoric loadings were extracted based upon detailed analyses of different soil layers. Through a full-field strain distribution analysis, a shear band evolution process was captured for the soil during deviatoric loading at a low confining stress. The photogrammetry-based method proved to be very powerful for in-depth soil deformation characteristics investigation.
37
Gan, J. K. M., D. G. Fredlund, and H. Rahardjo. "Determination of the shear strength parameters of an unsaturated soil using the direct shear test." Canadian Geotechnical Journal 25, no. 3 (August 1, 1988): 500–510. http://dx.doi.org/10.1139/t88-055.
Full textAbstract:
Multistage direct shear tests have been performed on saturated and unsaturated specimens of a compacted glacial till. A conventional direct shear apparatus was modified in order to use the axis-translation technique for direct shear tests on unsaturated soils. The soil can be subjected to a wide range of matric suctions. The testing procedure and some typical results are presented. Nonlinearity in the failure envelope with respect to matric suction was observed. Suggestions are made as to how best to handle the nonlinearity from a practical engineering standpoint. Key words: shear strength, unsaturated soils, negative pore-water pressures, soil suction, direct shear.
38
Morris, Peter H., J. Graham, and David J. Williams. "Cracking in drying soils." Canadian Geotechnical Journal 29, no. 2 (April 1, 1992): 263–77. http://dx.doi.org/10.1139/t92-030.
Full textAbstract:
Cracking in soils that are undergoing drying is controlled by soil suctions and by soil properties such as compression modulus, Poisson's ratio, shear strength, tensile strength, and specific surface energy. The paper reviews the occurrence and morphology of cracks in dry-climate regions of Australia and Canada. After reviewing the behaviour of unsaturated soils and the mechanics of cracking, solutions are developed based on (i) elasticity theory, (ii) the transition between tensile and shear failure, and (iii) linear elastic fracture mechanics. The solutions are compared and related to crack depths observed in the field. Key words : clay, cracks, crust, shear strength, soil suction, tensile strength, unsaturated soil, weathering.
39
Miao, Linchang, Sandra L. Houston, Ying Cui, and Junping Yuan. "Relationship between soil structure and mechanical behavior for an expansive unsaturated clay." Canadian Geotechnical Journal 44, no. 2 (February 1, 2007): 126–37. http://dx.doi.org/10.1139/t06-108.
Full textAbstract:
To investigate the soil structure and mechanical behavior of an unsaturated expansive clay soil, triaxial and mercury intrusion tests have been performed and are presented in this paper. Also an optical test system was developed for studying the internal structure evolution of the unsaturated expansive soil during shear-loading tests. The research results show a linear relationship between the cohesion intercept and the degree of saturation of the unsaturated clay for the test data. For the tested soil, the pore-size distribution curves were found to be bimodal. The measurement results from mercury intrusion tests confirm that the micropores of Guangxi expansive soils of this study remain constant, and that the macropores vary with the dry density of soil samples. Comparing the volumetric strain curves with the soil particle area curves, some correlation and dependence on the macropore variation of soil samples during shear-loading tests can be shown to exist.Key words: soil structure, mechanical behavior, unsaturated soil, mercury intrusion, expansive clay.
40
Li, Zhaoxin, Changguang Zhang, Jingyuan Zhao, and Qing Yan. "Safety Factor of Unsaturated Soil Slopes considering the Intermediate Principal Stress Effect and Different Profiles of Matric Suction." Mathematical Problems in Engineering 2021 (April 5, 2021): 1–10. http://dx.doi.org/10.1155/2021/6622522.
Full textAbstract:
Profiles of matric suction are critical for assessing the stability of unsaturated soil slopes, and the strength of unsaturated soils is affected by the intermediate principal stress. This study presents a theoretical formulation of safety factor for infinite unsaturated soil slopes under four different profiles of matric suction using the limit equilibrium method. The unified shear strength equation under plane strain conditions is adopted to capture the effect of intermediate principal stress on the strength of unsaturated soils. The proposed formulation of safety factor is found to have good comparability and broad applicability. The validity of the proposed formulation is demonstrated by comparing its predictions with the results of the extended shear strength method and the finite element method available in the literature. Parametric studies show that the effect of intermediate principal stress on the stability of unsaturated soil slopes is significant; the difference of safety factor among four suction profiles is pronounced, and the safety factor is highest for a linear suction profile. In addition, the safety factor changes with the infiltration depth in two stages, decreases with the slope angle, and increases with effective strength parameters. The results of this study are capable of providing beneficial guidance for optimization designs and disaster preventions of unsaturated soil slopes.
41
Wang, Jin Xing, Wei Min Liang, and Yong Qiang Yu. "Study on the Small-Strain Behaviors of Unsaturated Soils." Applied Mechanics and Materials 353-356 (August 2013): 1097–100. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.1097.
Full textAbstract:
Non-linear stress-strain characteristics and strain dependency of stiffness of saturated soils at small strain level have been reported by many researchers. However, the non-linear stiffness of unsaturated soils is not fully studied. The aim of this study is to clarify main factors affecting the non-linear stiffness of unsaturated soil at small strain range for a precise prediction of various ground deformations. Experiments were conducted with both sand and cohesive soil, by using a triaxial apparatus developed for small strain measurement. As the important factors for mechanical behaviour of unsaturated soils under small strain range, the effects of suction and mean net stress, which introduce the decrease of void ratio and degree of saturation, were discussed in the study.
42
Tun Tun, Win, Tomotaka Sato, Hirotaka Saito, and Yuji Kohgo. "Mechanical properties and stress–dilatancy relationships of unsaturated soil under various cyclic loading conditions." Acta Geotechnica 15, no. 7 (December 26, 2019): 1799–813. http://dx.doi.org/10.1007/s11440-019-00908-5.
Full textAbstract:
AbstractMost studies investigating the effect of cyclic loading on soil properties have been conducted for saturated soils. Embankments such as fill dams, roads and railways are usually constructed by unsaturated geo-materials and retained under unsaturated conditions during their in-service periods. Then when the stabilities of the embankments against dynamic motions such as earthquakes and traffic loads are evaluated, it is necessary to account for the cyclic properties of unsaturated soils. However, there are few studies investigating mechanical properties of unsaturated soils under cyclic loadings. There are two objectives in this paper. One objective is to investigate cyclic properties of an unsaturated silt under various cyclic loading conditions, while the other is to investigate the stress–dilatancy relationships; the relation of plastic strain increment ratio, − dεvp/dγp, versus stress ratio, q/p′; and to derive the plastic potential function of the unsaturated silt. Cyclic triaxial compression tests under various loading conditions were performed using the unsaturated silt. The material used is an artificial silty soil named DL clay. It was found from the series of the tests that the stiffness of the soil increased with an increase in suction and the number of cyclic loadings. The total volume reductions in the specimens decreased with an increase in suction. When the numbers of cyclic loadings and suction increased, the dilation also increased. Each unique stress–dilatancy relationship could be found in both loading and unloading processes. The relationships were similar to those of saturated soils under cyclic loadings. A unique plastic potential function could also be derived from the stress–dilatancy relationships.
43
Li, X., L. M. Zhang, and D. G. Fredlund. "Wetting front advancing column test for measuring unsaturated hydraulic conductivity." Canadian Geotechnical Journal 46, no. 12 (December 2009): 1431–45. http://dx.doi.org/10.1139/t09-072.
Full textAbstract:
Unsaturated hydraulic conductivity is the primary soil parameter required when performing seepage analyses for unsaturated–saturated soil systems. Unsaturated hydraulic conductivity is also one of the most difficult parameters to measure because of the time involved and the limited suction measurement range (e.g., 0∼1500 kPa in a test using the steady-state method). In this study, a new wetting front advancing method was developed for measuring unsaturated hydraulic conductivity. The wetting front advancing method simulates and monitors a soil wetting process through a large-scale soil column. A new interpretative procedure was developed to calculate the unsaturated hydraulic conductivity based on the monitored water content, suction, and wetting front advancing velocity. The proposed technique is used to measure the unsaturated hydraulic conductivities of five soils, which vary from gravel to clay. The results indicate that the proposed technique is time-saving (i.e., requires several days for a complete test) and is applicable over wide ranges of suctions and unsaturated hydraulic conductivities. The measured unsaturated hydraulic conductivity using the wetting front advancing method is similar to that obtained using the instantaneous profile method, with the latter covering narrower ranges of soil suction and hydraulic conductivity.
44
Kim, Tae-Hyung, and Stein Sture. "Capillary-induced tensile strength in unsaturated sands." Canadian Geotechnical Journal 45, no. 5 (May 2008): 726–37. http://dx.doi.org/10.1139/t08-017.
Full textAbstract:
While a majority of the studies related to unsaturated soils have focused on volume change, flow, and shear strength behavior, investigations of tensile strength of unsaturated soils, especially granular soils, have not received much attention except for those on cemented and clayey soils. This paper focuses on fundamental studies of tensile strength properties of granular soils in the unsaturated state, which were examined experimentally and theoretically. Experimental studies have shown that it is possible to accurately measure the tensile strength of sands at water contents in the range of 0.5%–17% by means of simple techniques. The method of specimen preparation has proved important, and the use of relatively large specimens has made development of homogeneous specimens and measurements relatively straightforward. The magnitude of the tensile strength of moist and relatively clean sands varies with water content, density, and soil type. The experimental data are also compared with mechanics-based models developed for monosized spheres, and their application for a real granular soil with a variety of particles is discussed in the unsaturated state, which includes the pendular, funicular, and capillary regions.
45
Roque, Pedro, Mariana Motta, and Tácio de Campos. "Suction effects on the tensile strength and unconfined compression of unsaturated soils." MATEC Web of Conferences 337 (2021): 01016. http://dx.doi.org/10.1051/matecconf/202133701016.
Full textAbstract:
The soil-water characteristic curve is an important relation of unsaturated soils, that expresses the variation of the amount of water retained in the soil as a function of its suction. In these soils, drying or wetting can have a great influence on their resistance parameters. This work presents and discusses the effects of increased suction on the tensile strength and unconfined compression of unsaturated soils. Suction was evaluated using the filter paper and the dew point technique, while the resistance parameters were obtained through the “Brazilian Test” and uniaxial compression. Three different soils from Rio de Janeiro were studied: two young residual soils, in which the influence of the soil structure was also verified through tests on undisturbed and reconstituted samples, and a colluvial soil. The results allowed to conclude that the increase of suction, in a first moment, generates an increase in the resistance parameters of these soils. With the continuation of the drying process, the mechanical behaviour of the soils varied, being able to maintain the resistance or showing a drop related to high suction values.
46
Monteiro, Fernando Feitosa, Renato Pinto da Cunha, Marcos Fábio Porto de Aguiar, and Carlos Medeiros Silva. "Bearing capacity assessment of bored piles equipped with expander body systems using the mechanics of unsaturated soils." MATEC Web of Conferences 337 (2021): 03011. http://dx.doi.org/10.1051/matecconf/202133703011.
Full textAbstract:
Bearing capacity of single piles are occasionally predicted using the renowned theoretical methods (α and β methods). These methods are based on laboratory tests, which can be time-consuming, but also applicable in foundation engineering practice for unsaturated soils. Full-scale pile load tests were carried out on bored piles equipped with Expander Body Systems in the Federal District of Brazil, known for its unsaturated, collapsible and porous soil. This paper has the aim to assess the applicability of the β method, considering the contribution of soil matric suction, in order to estimate the bearing capacity of these piles subjected to uplift and compression loads in unsaturated soils. Based on the experimental results, it is indicated that the use of the β method considering the matric suction, can be a useful tool for bearing capacity estimation of bored piles equipped with Expander Body Systems in unsaturated soils.
47
Rampino, Celestino, Claudio Mancuso, and Filippo Vinale. "Experimental behaviour and modelling of an unsaturated compacted soil." Canadian Geotechnical Journal 37, no. 4 (August 1, 2000): 748–63. http://dx.doi.org/10.1139/t00-004.
Full textAbstract:
This paper reports the experimental study and modelling of the mechanical response of a silty sand used in the core of the Metramo dam, Italy. Specimens were prepared by compacting the soil at optimum water content conditions using the modified Proctor technique. Tests were performed under suction-controlled conditions by a stress path triaxial cell and an oedometer. The experimental program consists of 23 tests carried out in the suction range of 0-400 kPa. The findings indicate the strong influence of suction on compressibility, stiffness, and shear strength. The mechanical properties of the soil improve with suction following an exponential law with decreasing gradient. Furthermore, the soil exhibited collapsible behaviour upon wetting even at low stress levels. Interesting results were also achieved in elastoplastic modelling as well. The results led to characterization of soil behaviour with reference to widely accepted modelling criteria for unsaturated soils, providing noteworthy suggestions about their applicability for granular materials with a non-negligible fine component. Finally, some remarks are made for the extension under unsaturated conditions of the "Nor sand" model for saturated granular soils. The proposed approach yields improved predictions of deviator soil response of the tested soil when Cambridge-type frameworks prove invalid.Key words: unsaturated soils, stress state variables, triaxial tests, oedometer tests, constitutive model.
48
Bashir, Rashid, Jitendra Sharma, and Halina Stefaniak. "Effect of hysteresis of soil-water characteristic curves on infiltration under different climatic conditions." Canadian Geotechnical Journal 53, no. 2 (February 2016): 273–84. http://dx.doi.org/10.1139/cgj-2015-0004.
Full textAbstract:
This paper presents results of a numerical modelling exercise that investigates the effects of hysteresis of the soil-water characteristic curve (SWCC) on the infiltration characteristics of soils subjected to four different climatic conditions — from very dry to wet — within the Canadian province of Alberta. Multi-year climate datasets from four different natural regions and subregions of Alberta are compiled, classified, and applied as the soil–atmosphere boundary condition in one-dimensional finite element unsaturated flow models using Hydrus-1D software. Multi-year simulations are carried out with and without consideration of the SWCC hysteresis. Simulation results are analyzed in terms of water balance at the ground surface and temporal distribution and storage of water within the soil domain. It is demonstrated that hysteresis of the SWCC can significantly affect the prediction of flow, redistribution, and storage of water in the unsaturated zone. It is found that for soils that exhibit hysteretic SWCC, consideration of hysteresis in unsaturated flow modelling results in the prediction of lower infiltration and less movement of water through the soil. It is also found that the use of wetting parameters results in the prediction of increased infiltration and movement of water compared with the predictions using drying or hysteretic parameters. It is concluded that, for soils that exhibit a greater degree of SWCC hysteresis, it is important to measure both the drying and wetting branches of the SWCC accurately and that accurate simulation of hysteretic behaviour requires climate datasets at appropriate resolution. The results presented in this paper highlight the importance of considering SWCC hysteresis for a wide range of geotechnical problems, such as soil cover design, prediction of groundwater recharge, contaminant transport through unsaturated soils, soil erosion, slope stability, and swelling–shrinkage of expansive soils.
49
Chen, Rui, Zhongkui Chen, Charles Wang Wai Ng, and Jian Liu. "Development of a pore gas pressure transducer used in unsaturated soils at high water content." E3S Web of Conferences 92 (2019): 02003. http://dx.doi.org/10.1051/e3sconf/20199202003.
Full textAbstract:
Pore gas pressure in soil is an important parameter in many geoscience applications such as evaluating the effects of trapped pore gas pressure on water infiltration through soil mass, optimizing the design of gas extraction wells in landfills and assessing the performance of landfill covers in reducing landfill gas emission. In addition, it has been observed that pore gas pressure affects slope stability in unsaturated soils. However, the pore gas pressure build-up induced by water infiltration is generally ignored in most slope stability analysis by assuming gas pressure to be zero. Therefore, pore gas pressure measurement in soils is crucial to better understand the unsaturated soil behaviour. However, most of current measuring techniques of pore gas pressure are affected by water interruption during the measurement in unsaturated soils, especially at high water content. In this study, a novel gas pressure transducer was developed to measure the pore gas pressure in unsaturated soil within a wide range of water content. The newly developed pore gas pressure transducer mainly consists of an electrical pressure sensor package and an integrated membrane filter which can prevent water leaching through the membrane but allow gas to pass it freely. The performance of the gas pressure transducer was evaluated by a series of permeation tests. The results show that the developed gas pressure transducer has a good repeatability to monitor gas pressure and has a relatively fast response to the gas pressure change in compacted soils. This transducer is able to measure pore gas pressure range of 0~50 kPa of soils within a relatively high range of soil water content.
50
Han, Bowen, Guoqing Cai, Lin Xie, Jian Li, and Chenggang Zhao. "Bounding surface constitutive model for unsaturated soils considering microscopic pore structure and bonding effect." E3S Web of Conferences 195 (2020): 02007. http://dx.doi.org/10.1051/e3sconf/202019502007.
Full textAbstract:
This article presents a bounding surface model for unsaturated soils by using skeleton stress and bonding variable based on microcosmic pore structure as constitutive variables. A Hydraulic hysteresis soil-water characteristic curve model considering deformation and hydraulic hysteresis is combined to achieve hydraulic coupling. The proposed model can capture the change of the inter-particles bonding effect in the deformation process of unsaturated soils and accurately predict the hydraulic mechanical behavior of unsaturated soils under complicated loading paths and wetting-drying cycles. The validity of the proposed model is confirmed by the results of unsaturated isotropic compression tests, wetting-drying cycles tests and unsaturated triaxial shear tests reported in the literature.