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Interception by vegetation is one of the main variables controlling hydrological and geo-environmental problems such as erosion, landslides and floods. Interception, along with precipitation and evapotranspiration, is required for the modeling of infiltration, percolation and runoff. Unfortunately, the measurement of interception in the field is time consuming, burdensome and subject to testing parameters with relatively high variability. In this context, experiments using rainfall simulators (RSs) have the potential to provide an alternative approach that addresses most of the limitations of field experiments. This paper presents a new approach to evaluate interception that combines a RS and the monitoring of the wetting front using pore-water pressure instrumentation at specific locations of the specimen. Two specimens are required, one with and another without vegetation. The proposed approach was applied to Paspalum notatum (bahiagrass) and a tropical soil. The results indicated an average interception of 5.1 mm of the simulated rainfall for a slope at 15 degrees, rainfall intensity of 86 mm h−1, and duration of 60 min. Furthermore, the vegetation decreased the surface runoff that contributes to erosion. The proposed method will enable studies on the interception mechanisms and the various involved variables, with benefits to the modeling of soil-vegetation-atmosphere interaction.
Thiago Mendes; Roberto Alves; Gilson Gitirana; Sávio Pereira; Juan Rebolledo; Marta da Luz. Evaluation of Rainfall Interception by Vegetation Using a Rainfall Simulator. Sustainability 2021, 13, 5082 .
AMA StyleThiago Mendes, Roberto Alves, Gilson Gitirana, Sávio Pereira, Juan Rebolledo, Marta da Luz. Evaluation of Rainfall Interception by Vegetation Using a Rainfall Simulator. Sustainability. 2021; 13 (9):5082.
Chicago/Turabian StyleThiago Mendes; Roberto Alves; Gilson Gitirana; Sávio Pereira; Juan Rebolledo; Marta da Luz. 2021. "Evaluation of Rainfall Interception by Vegetation Using a Rainfall Simulator." Sustainability 13, no. 9: 5082.
Crops cultivated in greenhouse normally use soilless substrates as a growing medium. In this production process, strict control of the application of water and fertilizers is required. The availability of sensors that measure accurately and at low cost the matric suction in the culture medium enables the automation of irrigation. Currently available sensors have deficiencies such as reduced sensitivity at low suctions, interference from ambient temperature and being affected by the salinity of the substrate. The cost of commercially available sensors is also a challenge. In this context, the objective of this study was to develop a heat dissipation sensor for measuring matric suction in the range of 0 to 5 kPa, as required by most agricultural substrates. The sensor consists of two parts, the first being an active core comprised of a heat source and a temperature sensor. The second part is a specially designed porous body that comes to hydraulic equilibrium with the medium in which the sensor is inserted. The porous body was produced using sintered glass microspheres. The data acquisition system uses the Arduino Uno platform. Sensors were calibrated and tested using a coconut fiber substrate submitted to water tensions between 0 and 10 kPa, using Haines’ funnels. Good correlations were observed between temperature variations in the sensor and water tension variations in the substrate between 0 and 5 kPa. The low cost and the adequate sensitivity of the sensor indicate that it can be used in the automatic control of irrigation systems in cultivation of plants in substrates.
Wilson N. da Mota; Adão W.P. Evangelista; Lauro J.Q. Maia; Vladia Correchel; Jose Alves; Luiz Felipe R. Varrone; Gilson De F.N. Gitirana. Development of a heat pulse sensor for measuring matric suction on soilless substrates. Computers and Electronics in Agriculture 2021, 185, 106119 .
AMA StyleWilson N. da Mota, Adão W.P. Evangelista, Lauro J.Q. Maia, Vladia Correchel, Jose Alves, Luiz Felipe R. Varrone, Gilson De F.N. Gitirana. Development of a heat pulse sensor for measuring matric suction on soilless substrates. Computers and Electronics in Agriculture. 2021; 185 ():106119.
Chicago/Turabian StyleWilson N. da Mota; Adão W.P. Evangelista; Lauro J.Q. Maia; Vladia Correchel; Jose Alves; Luiz Felipe R. Varrone; Gilson De F.N. Gitirana. 2021. "Development of a heat pulse sensor for measuring matric suction on soilless substrates." Computers and Electronics in Agriculture 185, no. : 106119.
Pressure and suction plate tests are among the most common techniques for determining the soil–water characteristic curve. The required testing period depends on many parameters and equilibrium times may vary from a few minutes to several weeks. This paper presents a numerical evaluation of the equilibrium process, considering the influence of soil type, equipment specifications, the use of thin high air-entry value (HAEV) membranes, and the employment of the interrupted outflow method (IOM). A fully coupled numerical model was developed and verified for the analysis of the conservation and flow of water and air in the specimen-HAEV interface system. Verification and sensitivity analyses showed, however, that the suction and pressure plate tests may be adequately represented using a simplified decoupled version of the full model. The results of the sensitivity analysis showed not only the role of the HAEV interface characteristics, but also the effect of soil type, suction value, suction step magnitude, and the suction path. It was found that the IOM offers greater control over testing times, but may cause undesirable suction reversals within the specimen. Finally, a simple method is presented to estimate the equilibrium times using basic testing parameters.
E. F. Vaz; G. F. N. Gitirana; T. A. Mendes; J. F. R. Rebolledo. On the equilibrium of suction and pressure plate tests. Acta Geotechnica 2021, 1 -18.
AMA StyleE. F. Vaz, G. F. N. Gitirana, T. A. Mendes, J. F. R. Rebolledo. On the equilibrium of suction and pressure plate tests. Acta Geotechnica. 2021; ():1-18.
Chicago/Turabian StyleE. F. Vaz; G. F. N. Gitirana; T. A. Mendes; J. F. R. Rebolledo. 2021. "On the equilibrium of suction and pressure plate tests." Acta Geotechnica , no. : 1-18.
Laboratory apparatuses for the analysis of infiltration and runoff enable studies under controlled environments and at reduced costs. Unfortunately, the design and construction of such systems are complex and face difficulties associated with the scale factor. This paper presents the design, construction, and evaluation of a portable rainfall and runoff simulator. The apparatus allows the evaluation of unsaturated soils with and without vegetation cover, under a wide range of simulation scenarios. The apparatus also enables the control of the intensity, size, and uniformity of simulated raindrops for variable surface slope, specimen thickness, and length conditions. The monitoring of the volumetric water content and matric suction and a rigorous computation of water balance are ensured. The obtained results indicate that the automated rainfall generator produces raindrops with Christiansen uniformity coefficients higher than 70%, and with an adequate distribution of raindrop sizes under a range of rainfall intensities between 86.0 and 220.0 mm h−1. The ideal rainfall generator conditions were established for a relatively small area equal to or lower than 1.0 m2 and considering rainfall events with return periods of 10 to 100 years.
Thiago Mendes; Sávio Pereira; Juan Rebolledo; Gilson Gitirana; Maria Melo; Marta Luz. Development of a Rainfall and Runoff Simulator for Performing Hydrological and Geotechnical Tests. Sustainability 2021, 13, 3060 .
AMA StyleThiago Mendes, Sávio Pereira, Juan Rebolledo, Gilson Gitirana, Maria Melo, Marta Luz. Development of a Rainfall and Runoff Simulator for Performing Hydrological and Geotechnical Tests. Sustainability. 2021; 13 (6):3060.
Chicago/Turabian StyleThiago Mendes; Sávio Pereira; Juan Rebolledo; Gilson Gitirana; Maria Melo; Marta Luz. 2021. "Development of a Rainfall and Runoff Simulator for Performing Hydrological and Geotechnical Tests." Sustainability 13, no. 6: 3060.
A theoretical model for the prediction of the soil–water characteristic curve (SWCC) is presented using pore-scale analysis and three-dimensional approximations of pore geometry employing the concept of unit cells. The model considers the effect of particle size and packing porosity on funicular and pendular retention. The unit cell was upscaled to non-uniform soils using the grain-size distribution curve. SWCC experiments on uniform and graded glass beads were carried out to provide verification data. Predictions for the glass beads showed reasonable results for drying SWCCs. The nonionic surfactant Triton X-100 and sodium chloride were utilized to demonstrate the role of the contact angle and surface tension. The modeling of wetting curves using advancing contact angles indicated the need to consider additional hysteresis mechanisms. The hypothesis of independent grain-size fractions often underestimated matric suctions, leading to the proposal of a correction function using the coefficient of uniformity. The proposed approaches were compared to four previously published models, using 58 glass beads and sandy materials. The new models provided superior results for most of the materials studied. The proposed framework offers a general approach that may be modified in the future by including other retention mechanisms and unit cell geometries.
Roberto D. Alves; Gilson De F.N. Gitirana Jr.; Sai K. Vanapalli. Advances in the modeling of the soil–water characteristic curve using pore-scale analysis. Computers and Geotechnics 2020, 127, 103766 .
AMA StyleRoberto D. Alves, Gilson De F.N. Gitirana Jr., Sai K. Vanapalli. Advances in the modeling of the soil–water characteristic curve using pore-scale analysis. Computers and Geotechnics. 2020; 127 ():103766.
Chicago/Turabian StyleRoberto D. Alves; Gilson De F.N. Gitirana Jr.; Sai K. Vanapalli. 2020. "Advances in the modeling of the soil–water characteristic curve using pore-scale analysis." Computers and Geotechnics 127, no. : 103766.
The resilient modulus (MR) is essential for the understanding of pavement response to climate effects, and to seasonal fluctuations of water content and matric suction. Unfortunately, only few studies have been directed towards the unsaturated resilient behavior of tropical soils and the influence of weathering and degree of laterization. This paper presents a study of the unsaturated resilient behavior of two tropical soils with distinct degrees of laterization, used as subgrades of highways in Brazil. The experimental program involved the measurement of the soil-water characteristic curve (SWCC), and the MR at different water contents and matric suctions. Eight models for MR, taken from the literature, were evaluated, and a new family of equations is proposed. The obtained SWCCs of the lateritic soil presented bimodal behavior, while the non-lateritic soil is unimodal. The bimodal behavior was attributed to clay aggregates produced by the laterization process. The observed relationship between MR and the stress-state variables depended on the degree of laterization. The lateritic subgrade soil showed significantly higher values of MR, but the resilient behavior was more sensitive to the water content when compared to the non-lateritic soil. The analysis of the literature models for MR indicated limitations in the manner how the unsaturated behavior was incorporated, producing adjusted coefficients of determination (Adj. R2) between 0.48 and 0.77. The newly proposed MR model was based on the statistical analyses of seven equations. The final proposed model includes two independent stress-state variable and a third state variable, that accounts for the water content deviation from optimum conditions. Finally, the proposed model was validated using MR data from the literature. The proposed model produced superior results when comparing to the previously proposed equations, resulting in values of Adj. R2 varying between 0.93 and 0.99. The newly proposed model proved to be flexible, being capable of modeling both the lateritic and non-lateritic soils in an accurate manner. These results are expected to offer significant improvements to the Brazilian mechanistic-empirical pavement design guide, and for similar guides in other countries where tropical soils are found.
Jeferson Barbosa de Freitas; Lilian Ribeiro de Rezende; Gilson De F.N. Gitirana Jr.. Prediction of the resilient modulus of two tropical subgrade soils considering unsaturated conditions. Engineering Geology 2020, 270, 105580 .
AMA StyleJeferson Barbosa de Freitas, Lilian Ribeiro de Rezende, Gilson De F.N. Gitirana Jr.. Prediction of the resilient modulus of two tropical subgrade soils considering unsaturated conditions. Engineering Geology. 2020; 270 ():105580.
Chicago/Turabian StyleJeferson Barbosa de Freitas; Lilian Ribeiro de Rezende; Gilson De F.N. Gitirana Jr.. 2020. "Prediction of the resilient modulus of two tropical subgrade soils considering unsaturated conditions." Engineering Geology 270, no. : 105580.
The analysis of the stability of slopes using the limit equilibrium method largely depends on the use of an adequate procedure for finding the position and shape of the critical slip surface. Critical slip surfaces have been traditionally determined using brute force techniques that rely on assumptions regarding the shape of the slip surface, thereby imposing considerable constraints. Several optimization methods have been proposed in the literature to improve the search procedure for critical slip surfaces. Unfortunately, most research involving optimization methods has been confined to two-dimensional analysis. This paper examines the use of an optimization technique to different slope stability problems in three dimensions. The presented results show that the procedure is capable of locating a lower minimum factor of safety when compared to conventional approaches, even if the initial arbitrary slip surface adopted for the optimization procedure is not close to the converged slip surface. It was also demonstrated that the optimization procedure is capable of identifying composite shapes produced by the presence of a weak layer. The shape of the critical slip surface obtained using the optimization procedure was shown to deviate from an ellipsoidal shape when conditions such as weak layers of material anisotropy are present.
Murray D. Fredlund; Gilson Gitirana Jr.; Zenja Ivkovic; Haihua Lu. Influence of Slip Surface Shape on 3D Slope Stability Analysis. Geo-Congress 2020 2020, 1 .
AMA StyleMurray D. Fredlund, Gilson Gitirana Jr., Zenja Ivkovic, Haihua Lu. Influence of Slip Surface Shape on 3D Slope Stability Analysis. Geo-Congress 2020. 2020; ():1.
Chicago/Turabian StyleMurray D. Fredlund; Gilson Gitirana Jr.; Zenja Ivkovic; Haihua Lu. 2020. "Influence of Slip Surface Shape on 3D Slope Stability Analysis." Geo-Congress 2020 , no. : 1.
Runoff apparatuses (RA) are developed to study infiltration, runoff generation, and erosion processes. Several RA designs are available, but limited attention has been given to the effects of the equipment scale, initial, and boundary conditions on measured runoff. This paper presents a model-based evaluation of RAs using a finite element solution for Richard’s equation and a novel ground surface boundary condition designed to accommodate unsaturated soil behavior. The hydraulic properties of two tropical soils were considered, with multiple combinations of initial water contents, specimen dimensions, and sloping angle. The numerical exercises indicate that soils with lower air-entry values require an equilibrium stage for the establishment of initial conditions. Testing protocols with equilibrium times of 48 hours are recommended. Moisture flow produced by gravity when sloping the specimen was shown to potentially affect surface conditions and, consequently, runoff. Testing specifications to minimize the effects of specimen sloping are presented. The runoff mechanism in an RA was shown to have up to three stages, all with clear physical meaning. The third stage is an undesirable consequence of the influence of the RA’s impervious bottom. The establishment of the minimum specimen thickness that prevents boundary effects was shown to have major importance to testing results.
Thiago Augusto Mendes; Gilson De Farias Neves Gitirana Jr.; Juan Félix Rodriguez Rebolledo; Emílio Farias Vaz; Marta Pereira da Luz. Numerical evaluation of laboratory apparatuses for the study of infiltration and runoff. RBRH 2020, 25, 1 .
AMA StyleThiago Augusto Mendes, Gilson De Farias Neves Gitirana Jr., Juan Félix Rodriguez Rebolledo, Emílio Farias Vaz, Marta Pereira da Luz. Numerical evaluation of laboratory apparatuses for the study of infiltration and runoff. RBRH. 2020; 25 ():1.
Chicago/Turabian StyleThiago Augusto Mendes; Gilson De Farias Neves Gitirana Jr.; Juan Félix Rodriguez Rebolledo; Emílio Farias Vaz; Marta Pereira da Luz. 2020. "Numerical evaluation of laboratory apparatuses for the study of infiltration and runoff." RBRH 25, no. : 1.
RESUMO: A falha da Barragem de Fundão, o maior desastre de seu tipo no mundo, foi estudada por Morgenstern et al. (2016) através de abordagens bidimensionais. A investigação realizada não apontou mecanismos de instabilidade de taludes como sendo as causas do desastre. No entanto, o formato complexo da face da barragem, com regiões côncavas e convexas, não foi considerado devido às limitações das ferramentas empregadas. Este trabalho apresenta análises bidimensionais (2D) e tridimensionais (3D), teoricamente mais rigorosas e adequadas para a geometria da barragem. As análises de estabilidade do maciço foram realizadas utilizando o Método Geral das Fatias e das Colunas (GLE), por meio do software SVSLOPE. Foram realizadas buscas por superfícies críticas 2D e 3D, ao longo de todas as zonas da estrutura. Considerando-se parâmetros de resistência drenada, observou-se que Fundão se encontraria em condições de elevada segurança, sendo o menor Fator de Segurança igual a 1,744. Valores próximos de 1,0 foram obtidos considerando rejeitos na condição não drenada, supostamente menos representativa das condições reais de campo. Os Fatores de Segurança 3D se mostraram muito próximos dos 2D, porém com variações significativas nas regiões côncava e convexa. Desta forma, conclui-se que o formato próximo à região do recuo exige maior atenção e análises 3D podem identificar as regiões críticas. The failure of the Fundão Dam, the largest disaster of its kind in the world, was studied by Morgenstern et al. (2016) using two-dimensional approaches. The carried out investigation did not point to mechanisms of slope instability as the causes of the disaster. However, the complex shape of the dam and its concave and convex regions were not originally considered due to limitations of the analysis tools employed. This paper presents two-dimensional (2D) and three-dimensional (3D) analyses that are more rigorous and well suited for the Fundão dam geometry. Slope stability analyses were accomplished using the General Limit Equilibrium Method of Slices and Columns (GLE) using the SVSLOPE software. Critical slip surfaces were searched in 2D and 3D, across the entire dam face. Drained shear strength parameters led to Factors of Safety that would indicate fairly stable conditions, with a lowest Factor of Safety of 1.744. Values close to 1.0 were obtained considering undrained conditions of the tailings, which are supposedly less representative of field conditions. The 3D factors of safety were very close to the 2D values, but with noticeably higher variations near the concave and convex regions. This leads to the conclusion that the dam shape near the setback region requires closer examination by means of 3D analyses that enable the identification of critical zones.
Gilson Gitirana Jr.; João Paulo Tavares Souza; Nícolas Rodrigues Moura. ANÁLISE 2D E 3D DA ESTABILIDADE DA BARRAGEM DE FUNDÃO. REEC - Revista Eletrônica de Engenharia Civil 2019, 15, 123 -136.
AMA StyleGilson Gitirana Jr., João Paulo Tavares Souza, Nícolas Rodrigues Moura. ANÁLISE 2D E 3D DA ESTABILIDADE DA BARRAGEM DE FUNDÃO. REEC - Revista Eletrônica de Engenharia Civil. 2019; 15 (2):123-136.
Chicago/Turabian StyleGilson Gitirana Jr.; João Paulo Tavares Souza; Nícolas Rodrigues Moura. 2019. "ANÁLISE 2D E 3D DA ESTABILIDADE DA BARRAGEM DE FUNDÃO." REEC - Revista Eletrônica de Engenharia Civil 15, no. 2: 123-136.
O artigo propõe metodologias de laboratório simples para obter a envoltória de ruptura em solos não saturados. A primeira metodologia é baseada em ensaios de tração indireta de corpos de prova usados para a definição da curva característica do solo e o ensaio de cisalhamento direto saturado. Esta metodologia é avaliada numericamente a partir da distribuição do estado de tensões usando o modelo de elementos finitos em 3D. As outras metodologias consistem na combinação dos ensaios de cisalhamento direto em amostras saturadas e o ensaio de compressão simples, assim como da combinação do ensaio de compressão simples com o ensaio de tração indireta, junto com a curva característica. Estas metodologias têm como vantagem a simplicidade e economia, possibilitando a avaliação de parâmetros de resistência, para a condição não saturada, e que pode ser uma alternativa razoável quando os parâmetros de tensão não podem ser obtidos diretamente dos ensaios de cisalhamento com sucção controlada.
Yamile Valencia Gonzalez; Jose Camapum De Carvalho; Gilson Gitirana Jr.. Metodologias simples para determinar em solos parcialmente saturados a envoltória de resistência ao cisalhamento. Revista EIA 2019, 16, 43 -53.
AMA StyleYamile Valencia Gonzalez, Jose Camapum De Carvalho, Gilson Gitirana Jr.. Metodologias simples para determinar em solos parcialmente saturados a envoltória de resistência ao cisalhamento. Revista EIA. 2019; 16 (32):43-53.
Chicago/Turabian StyleYamile Valencia Gonzalez; Jose Camapum De Carvalho; Gilson Gitirana Jr.. 2019. "Metodologias simples para determinar em solos parcialmente saturados a envoltória de resistência ao cisalhamento." Revista EIA 16, no. 32: 43-53.
The flow of water in mining tailings and waste rock may cause serious environmental impacts associated with acid rock drainage. Soil cover systems have been used to control or minimise such damages. In relatively dry climates, ‘store-and-release’ covers, also known as dry covers, have been considered as feasible alternatives. The objective of this paper is to evaluate the influence of atmospheric conditions and soil type in the performance of dry cover systems, considering conditions typical of tropical climates found in Brazil’s centralwest region. Numerical analyses using the finite element method were performed considering four different systems composed of tropical soils. Among the proposed arrangements, three use a soil that presents a bimodal soil–water characteristic curve and the fourth cover employs a unimodal soil. The thicknesses of intermediate materials were varied, and different representative precipitation parameters were considered for a period of one year. The results obtained were compared in terms of the internal flow and the capacity of the system to store water. The results indicate that bimodal soils may not be ideal cover materials and require specific compaction conditions that would reduce their macropores. Unimodal tropical soils presented adequate response as store-and-release materials. The use of an intermediate layer acting as a capillary barrier did not offer significant improvement to the cover systems evaluated.
Deborah Perotti; Gilson Gitirana Jr.; Murray Fredlund. Analysis of dry cover systems composed of tropical soils for mining waste. Proceedings of the 13th International Conference on Mine Closure 2019, 579 -592.
AMA StyleDeborah Perotti, Gilson Gitirana Jr., Murray Fredlund. Analysis of dry cover systems composed of tropical soils for mining waste. Proceedings of the 13th International Conference on Mine Closure. 2019; ():579-592.
Chicago/Turabian StyleDeborah Perotti; Gilson Gitirana Jr.; Murray Fredlund. 2019. "Analysis of dry cover systems composed of tropical soils for mining waste." Proceedings of the 13th International Conference on Mine Closure , no. : 579-592.
Most unsaturated soil problems are intrinsically related to the analysis of soil-atmosphere phenomena and cannot be solved without the establishment of design pore-water pressures. This paper presents an overview of soil-atmosphere modeling applied to near ground surface problems and presents examples of how weather conditions can be considered in practice. Some of the main modeling approaches are presented. The analysis of the relation between weather conditions and soil behavior is shown as the combination of models for the internal fluxes of mass and energy within the soil and appropriate boundary conditions that take into account their dependency on ground surface conditions. The use of some of these modeling approaches is illustrated by considering two problems. First, the establishment of design pore-water pressures for the design of retaining structures. Next, the use of soil-atmosphere modeling on slope stability analysis. The paper presents these subjects in a way that is intended to raise awareness to the importance of advancing current engineering protocols.
G. F. N. Gitirana. Soil-Atmosphere Interaction in Unsaturated Soils Problem Solving. PanAm Unsaturated Soils 2017 2018, 1 .
AMA StyleG. F. N. Gitirana. Soil-Atmosphere Interaction in Unsaturated Soils Problem Solving. PanAm Unsaturated Soils 2017. 2018; ():1.
Chicago/Turabian StyleG. F. N. Gitirana. 2018. "Soil-Atmosphere Interaction in Unsaturated Soils Problem Solving." PanAm Unsaturated Soils 2017 , no. : 1.
Este artigo apresenta um estudo do fenômeno de barreira capilar a partir da modelagem física e numérica. Foi desenvolvido um modelo físico unidimensional contendo duas camadas de solos arenosos submetidas a infiltração. A simulação numérica utilizou o método dos volumes finitos para solução da equação de Richards. Os resultados demonstram o efeito e a falha da barreira capilar e sua relação com as propriedades e variáveis de estado do solo. O modelo numérico proposto foi capaz de reproduzir adequadamente os fenômenos observados no modelo físico. Demonstrou-se como a barreira capilar depende da diferença de carga piezométrica e condutividade hidráulica não saturada próxima à interface. Foi apresentada a evolução das condições de interface durante o processo de formação e quebra da barreira e demonstrada sua capacidade de recomposição após interrupção da infiltração.
Paulo Augusto Diniz Silva; Gilson De F. N. Gitirana Jr.. Avaliação física e numérica da formação e quebra de barreira capilar. Águas Subterrâneas 2017, 31, 393 .
AMA StylePaulo Augusto Diniz Silva, Gilson De F. N. Gitirana Jr.. Avaliação física e numérica da formação e quebra de barreira capilar. Águas Subterrâneas. 2017; 31 (4):393.
Chicago/Turabian StylePaulo Augusto Diniz Silva; Gilson De F. N. Gitirana Jr.. 2017. "Avaliação física e numérica da formação e quebra de barreira capilar." Águas Subterrâneas 31, no. 4: 393.
The availability of statistical values for soil parameters is essential in reliability-based geotechnical design and sensitivity analysis. Unfortunately, there are few statistical studies available about unsaturated soil parameters. The primary objective of this paper is to present a methodology for the statistical assessment of hydraulic properties of unsaturated soil and to present the results of a statistical study carried out using a large database of soil properties. Two fundamental unsaturated soil properties are considered; namely, the soil-water characteristic curve (SWCC) and the hydraulic conductivity function. Appropriate nonlinear functions and fitting parameters with well-defined and unique physical and/or geometrical meanings were adopted. The main contribution of this article is the establishment of central tendency measures, standard deviations, and correlation coefficients for the unsaturated soil parameters, considering soil datasets grouped according to soil texture. It was determined based on the analyses results that the air-entry value, primary SWCC slope, residual SWCC slope, saturated hydraulic conductivity, and hydraulic conductivity function slope could be well described using lognormal probability density functions. Finally, general guidelines are provided regarding the statistical values to be adopted for the unsaturated soil properties studied.
Gilson De F. N. Gitirana; Delwyn G. Fredlund. Statistical Assessment of Hydraulic Properties of Unsaturated Soils. Soils and Rocks 2016, 81 -95.
AMA StyleGilson De F. N. Gitirana, Delwyn G. Fredlund. Statistical Assessment of Hydraulic Properties of Unsaturated Soils. Soils and Rocks. 2016; ():81-95.
Chicago/Turabian StyleGilson De F. N. Gitirana; Delwyn G. Fredlund. 2016. "Statistical Assessment of Hydraulic Properties of Unsaturated Soils." Soils and Rocks , no. : 81-95.
Deborah Mayara A. Amoroso Amoroso; Gilson De F. N. Gitirana Júnior Gitirana Jr.; Paulo Augusto Diniz Silva Silva; Gustavo Ferreira Simões. Curvas características solo-água de duas areias submetidas a ciclos de molhagem e secagem. XVIII Congresso Brasileiro de Mecânica dos Solos e Engenharia Geotécnica 2016, 1 .
AMA StyleDeborah Mayara A. Amoroso Amoroso, Gilson De F. N. Gitirana Júnior Gitirana Jr., Paulo Augusto Diniz Silva Silva, Gustavo Ferreira Simões. Curvas características solo-água de duas areias submetidas a ciclos de molhagem e secagem. XVIII Congresso Brasileiro de Mecânica dos Solos e Engenharia Geotécnica. 2016; ():1.
Chicago/Turabian StyleDeborah Mayara A. Amoroso Amoroso; Gilson De F. N. Gitirana Júnior Gitirana Jr.; Paulo Augusto Diniz Silva Silva; Gustavo Ferreira Simões. 2016. "Curvas características solo-água de duas areias submetidas a ciclos de molhagem e secagem." XVIII Congresso Brasileiro de Mecânica dos Solos e Engenharia Geotécnica , no. : 1.
Murray Fredlund; Haihua Lu; Matthew Donaldson; Gilson Gitirana Jr.. Multi-Directional 3-D LEM Slope Stability. XVIII Congresso Brasileiro de Mecânica dos Solos e Engenharia Geotécnica 2016, 1 .
AMA StyleMurray Fredlund, Haihua Lu, Matthew Donaldson, Gilson Gitirana Jr.. Multi-Directional 3-D LEM Slope Stability. XVIII Congresso Brasileiro de Mecânica dos Solos e Engenharia Geotécnica. 2016; ():1.
Chicago/Turabian StyleMurray Fredlund; Haihua Lu; Matthew Donaldson; Gilson Gitirana Jr.. 2016. "Multi-Directional 3-D LEM Slope Stability." XVIII Congresso Brasileiro de Mecânica dos Solos e Engenharia Geotécnica , no. : 1.
The numerical modeling of unsaturated soil processes is becoming more prevalent worldwide. Although numerical modeling is becoming increasingly accepted in geotechnical engineering practice, care must be exercised and improper modeling techniques and procedures must be avoided. Many issues such as nodal resolution and imperfect convergence can result in inaccurate solutions. Unfortunately, analyses of highly nonlinear unsaturated soil flow and slope stability models can significantly increase the modeling time required. As a result, there is a trend to reduce the number of model runs. Results are often presented to client as single model runs or simplistic sensitivity analysis. This paper presents methodologies for applying probabilistic methods to unsaturated soils seepage and slope stability analysis models. The focus is on the application of the alternative point estimate method to practical problems in such a way as to minimize the number of model runs. The demonstration of a successful application to a waste rock pile is presented.
Murray Fredlund; Gilson Gitirana. Probabilistic Methods Applied to Unsaturated Numerical Modeling. Geotechnical and Geological Engineering 2011, 29, 217 -223.
AMA StyleMurray Fredlund, Gilson Gitirana. Probabilistic Methods Applied to Unsaturated Numerical Modeling. Geotechnical and Geological Engineering. 2011; 29 (2):217-223.
Chicago/Turabian StyleMurray Fredlund; Gilson Gitirana. 2011. "Probabilistic Methods Applied to Unsaturated Numerical Modeling." Geotechnical and Geological Engineering 29, no. 2: 217-223.
Methods for application of unsaturated soils analysis have progressed greatly in the past few years. The consideration of unsaturated scenarios in the numerical modeling of seepage in soils as well as the influence on slope stability is becoming more commonplace in geotechnical consulting firms. Given that the dissipation of soil suction is often a trigger mechanism in slope failures it is becoming increasingly important to apply probability theory to the determination of reasonable flow scenarios in soil slopes. This is especially true in light of the reasonable variation in climatic influences. This paper intends to describe a reasonable methodology for the describing of unsaturated hydraulic properties of a soil for application in a numerical modeling seepage analysis.
Murray Fredlund; Gilson Gitirana; Hung Pham. A Methodology for Applying Probability Theory to Unsaturated Hydraulic Properties as the Foundation for Seepage Analysis. GeoCongress 2008 2008, 902 -909.
AMA StyleMurray Fredlund, Gilson Gitirana, Hung Pham. A Methodology for Applying Probability Theory to Unsaturated Hydraulic Properties as the Foundation for Seepage Analysis. GeoCongress 2008. 2008; ():902-909.
Chicago/Turabian StyleMurray Fredlund; Gilson Gitirana; Hung Pham. 2008. "A Methodology for Applying Probability Theory to Unsaturated Hydraulic Properties as the Foundation for Seepage Analysis." GeoCongress 2008 , no. : 902-909.
Weather-related geo-hazards are a major concern for the railway industry m Canada. The financial losses that result from derailments and delays amount to millions of dollars every year. On the other hand, the assessment and management of geo-hazards is a difficult problem that involves complex coupled phenomena and numerous soil and weather parameters. The primary goal of this paper is to illustrate the manner whereby unsaturated soil mechanics can be taken from the soil property assessment level using techniques based on the soil-water characteristic curve (SWCC), to the solution of this real and highly complex problem. First, a concise description of the weather-related geo-hazards assessment model (W-GHA model) is given. Deterministic and probabilistic aspects of the model were developed within a Decision Analysis framework. The deterministic core of the model consists of a two-dimensional stability analysis combined with the analysis of the effects of weather conditions on the pore-water pressures. According to the proposed model, weather conditions interact with the ground through the flow of liquid water, water vapour, and heat. Critical embankment stability conditions are determined using a Dynamic Programming Method (DPM) combined with Finite Element based stress fields. The soil system is ultimately represented by a series of partial differential equations (PDE’s) governing conservation of mass and momentum. A discrete stochastic analysis is implemented within the proposed framework. Several unsaturated soil property functions are required as input to the system of PDE’s. The hydraulic conductivity (i.e., coefficient of permeability), vapour diffusion coefficient, thermal conductivity, volumetric specific heat, and shear strength are all nonlinear functions physically related to the SWCC. The methodology by which these soil property functions can be inter-related to the SWCC is presented. The theoretical model illustrates the manner whereby it is possible to quantitatively assess embankment stability based on weather conditions. The methodology is feasible and yet relatively comprehensive.
Gilson Gitirana; Delwyn G. Fredlund. From experimental evidence towards the assessment of weather-related railway embankment hazards. Springer Proceedings in Physics 2005, 93, 435 -467.
AMA StyleGilson Gitirana, Delwyn G. Fredlund. From experimental evidence towards the assessment of weather-related railway embankment hazards. Springer Proceedings in Physics. 2005; 93 ():435-467.
Chicago/Turabian StyleGilson Gitirana; Delwyn G. Fredlund. 2005. "From experimental evidence towards the assessment of weather-related railway embankment hazards." Springer Proceedings in Physics 93, no. : 435-467.