The Experts below are selected from a list of 3063 Experts worldwide ranked by ideXlab platform
Ahmed Melegy - One of the best experts on this subject based on the ideXlab platform.
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soil water distribution and movement in Layered Soils of a dam farmland
Water Resources Management, 2010Co-Authors: Peipei Zhao, Mingan Shao, Ahmed MelegyAbstract:In soil profiles, special emphasis has been placed on the migration of agricultural chemicals spread intentionally or accidentally into deep Soils or groundwater body. To prevent soil water pollution and estimate the magnitude of the hazard caused by these chemicals, it is necessary to know the processes controlling their movement from the soil surface, through the root zone and eventually to the water table. This paper deals with two-dimensional soil water distribution and movement in sloping Layered Soils of a dam farmland on the Loess Plateau of China. In the dam farmland, soil water content showed horizontal distribution corresponding to spatial patterns of the particle sizes. The soil water content of deeper soil was relatively stable compared with topsoil. Generally, rainfall infiltration was limited to 0.8 m in the study period. Funnel flows were found in the Layered Soils of the dam farmland after rainfall proving the existence of this phenomenon which was observed in simulation experiments and field observation by previous researches. In the study area, the wetting front was unstable due to the Layered Soils. The spatial correlation analysis of the soil water content showed water movement along the layers in the wetting process with 7 m day − 1 only on the first day after rainfall. On the vertical direction, the velocity of water movement was 0.3 m day − 1 on the first day after rainfall. The results indicated that the quantity of funnel flow increases with distance along the inclined interfaces in the dam farmland which can cause contamination of groundwater. Consequently, future studies should consider the funnel flow and the management of agriculture chemicals in dam farmlands. Copyright Springer Science+Business Media B.V. 2010
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soil water distribution and movement in Layered Soils of a dam farmland
Water Resources Management, 2010Co-Authors: Peipei Zhao, Mingan Shao, Ahmed MelegyAbstract:In soil profiles, special emphasis has been placed on the migration of agri- cultural chemicals spread intentionally or accidentally into deep Soils or groundwater body. To prevent soil water pollution and estimate the magnitude of the hazard caused by these chemicals, it is necessary to know the processes controlling their movement from the soil surface, through the root zone and eventually to the water table. This paper deals with two-dimensional soil water distribution and movement in sloping Layered Soils of a dam farmland on the Loess Plateau of China. In the dam farmland, soil water content showed horizontal distribution corresponding to spatial patterns of the particle sizes. The soil water content of deeper soil was relatively stable compared with topsoil. Generally, rainfall infiltration was limited to 0.8 m in the study period. Funnel flows were found in the Layered Soils of the dam farmland after rainfall proving the existence of this phenomenon which was observed in simulation experiments and field observation by previous researches. In the study area, the wetting front was unstable due to the Layered Soils. The spatial correlation analysis of the soil water content showed water movement along the layers in the wetting process with 7 m day −1 only on the first day after rainfall. On the vertical direction, the velocity of water movement was 0.3 m day −1 on the first day after
Peipei Zhao - One of the best experts on this subject based on the ideXlab platform.
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soil water distribution and movement in Layered Soils of a dam farmland
Water Resources Management, 2010Co-Authors: Peipei Zhao, Mingan Shao, Ahmed MelegyAbstract:In soil profiles, special emphasis has been placed on the migration of agricultural chemicals spread intentionally or accidentally into deep Soils or groundwater body. To prevent soil water pollution and estimate the magnitude of the hazard caused by these chemicals, it is necessary to know the processes controlling their movement from the soil surface, through the root zone and eventually to the water table. This paper deals with two-dimensional soil water distribution and movement in sloping Layered Soils of a dam farmland on the Loess Plateau of China. In the dam farmland, soil water content showed horizontal distribution corresponding to spatial patterns of the particle sizes. The soil water content of deeper soil was relatively stable compared with topsoil. Generally, rainfall infiltration was limited to 0.8 m in the study period. Funnel flows were found in the Layered Soils of the dam farmland after rainfall proving the existence of this phenomenon which was observed in simulation experiments and field observation by previous researches. In the study area, the wetting front was unstable due to the Layered Soils. The spatial correlation analysis of the soil water content showed water movement along the layers in the wetting process with 7 m day − 1 only on the first day after rainfall. On the vertical direction, the velocity of water movement was 0.3 m day − 1 on the first day after rainfall. The results indicated that the quantity of funnel flow increases with distance along the inclined interfaces in the dam farmland which can cause contamination of groundwater. Consequently, future studies should consider the funnel flow and the management of agriculture chemicals in dam farmlands. Copyright Springer Science+Business Media B.V. 2010
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soil water distribution and movement in Layered Soils of a dam farmland
Water Resources Management, 2010Co-Authors: Peipei Zhao, Mingan Shao, Ahmed MelegyAbstract:In soil profiles, special emphasis has been placed on the migration of agri- cultural chemicals spread intentionally or accidentally into deep Soils or groundwater body. To prevent soil water pollution and estimate the magnitude of the hazard caused by these chemicals, it is necessary to know the processes controlling their movement from the soil surface, through the root zone and eventually to the water table. This paper deals with two-dimensional soil water distribution and movement in sloping Layered Soils of a dam farmland on the Loess Plateau of China. In the dam farmland, soil water content showed horizontal distribution corresponding to spatial patterns of the particle sizes. The soil water content of deeper soil was relatively stable compared with topsoil. Generally, rainfall infiltration was limited to 0.8 m in the study period. Funnel flows were found in the Layered Soils of the dam farmland after rainfall proving the existence of this phenomenon which was observed in simulation experiments and field observation by previous researches. In the study area, the wetting front was unstable due to the Layered Soils. The spatial correlation analysis of the soil water content showed water movement along the layers in the wetting process with 7 m day −1 only on the first day after rainfall. On the vertical direction, the velocity of water movement was 0.3 m day −1 on the first day after
Maosong Huang - One of the best experts on this subject based on the ideXlab platform.
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upper bound stability analysis of slurry supported trenches in Layered Soils
Computers and Geotechnics, 2020Co-Authors: Hongyu Wang, Maosong HuangAbstract:Abstract A stability analysis of slurry-supported trenches in horizontally Layered cohesive-frictional Soils by using the kinematical approach of limit analysis is presented. To ensure the kinematical admissibility, the failure surface in the formulated multi-block rotational mechanism was composed of several segments of logarithmic spirals with a same rotation center. To account for varying soil properties among different layers, both toe and above-toe failure patterns were considered. The associated factor of safety was determined by the shear strength reduction technique and was verified by comparison with the shear strength reduction finite element method (SSRFEM). It was found that the results obtained from the simplified approach by using weighted average soil parameters were not reliable and sometimes led to significantly overestimated safety factors on trench stability in Layered Soils, which deserves more attention in practice.
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three dimensional upper bound analysis for ultimate bearing capacity of laterally loaded rigid pile in undrained clay
Canadian Geotechnical Journal, 2015Co-Authors: Maosong Huang, Chenrong ZhangAbstract:A new three-dimensional upper-bound combined failure mechanism is presented to analyze the lateral ultimate capacity of rigid piles embedded in various soil conditions, involving homogeneous Soils, Layered Soils, and Gibson Soils. The wedge curved failure surface function composed by rotating the Newton interpolation polynomial is adopted near the ground surface, and a plane strain collapse mechanism is employed at depth. Furthermore, the energy dissipation of the transition interface is introduced to keep a kinematically admissible velocity field between the wedge and the plane strain mechanism. An empirical equation is then proposed based on the upper-bound solutions for the homogeneous Soils, and extended to the Layered Soils and Gibson Soils. Meanwhile, the three-dimensional arbitrary Lagrangian–Eulerian (ALE) analysis is employed to investigate the distribution of limiting pressures along the pile shaft for different soil parameters. It is found that the upper-bound solutions based on the rigid-plast...
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analysis of pile raft foundations under complex loads in Layered Soils
International Journal for Numerical and Analytical Methods in Geomechanics, 2014Co-Authors: Maosong Huang, Kenan LianAbstract:SUMMARY Considering there is hardly any concerted effort to analyze the pile-raft foundations under complex loads (combined with vertical loads, horizontal loads and moments), an analysis method is proposed in this paper to estimate the responses of pile-raft foundations which are subjected to vertical loads, horizontal loads and moments in Layered Soils based on solutions for stresses and displacements in Layered elastic half space. Pile to pile, pile to soil surface, soil surface to pile and soil surface to soil surface interactions are key ingredients for calculating the responses of pile-raft foundations accurately. Those interactions are fully taken into account to estimate the responses of pile-raft foundations subject to vertical loads, horizontal loads and moments in Layered Soils. The constraints of the raft on vertical movements, horizontal movements and rotations of the piles as well as the constraints of the raft on vertical movements and horizontal movements of the Soils are considered to reflect the coupled effect on the raft. The method is verified through comparisons with the published methods and FEM. Then, the method is adopted to investigate the influence of soil stratigraphy on pile responses. The study shows that it is necessary to consider the soil non-homogeneity when estimating the responses of pile-raft foundations in Layered Soils, especially when estimating the horizontal responses of pile-raft foundations. The horizontal loads and the moments have a significant impact on vertical responses of piles in pile-raft foundations, while vertical loads have little influence on horizontal responses of piles in pile-raft foundations in the cases of small deformations. The proposed method can provide a simple and useful tool for engineering design. Copyright © 2013 John Wiley & Sons, Ltd.
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deformation analysis of tunnel excavation below existing pipelines in multi Layered Soils based on displacement controlled coupling numerical method
International Journal for Numerical and Analytical Methods in Geomechanics, 2012Co-Authors: Zhiguo Zhang, Maosong Huang, Mengxi ZhangAbstract:SUMMARY The effect of tunneling on surrounding environments, especially on existing buried pipelines is a problem that engineers designing and practicing in urban geotechnical environments encounter more frequently than in the past. However, previous studies are usually based on the assumption that the soil is homogeneous. How to reflect soil stratification is the main focus for the problem of tunneling in multi-Layered Soils. A displacement controlled coupling numerical method is presented for the displacement analysis of tunnel excavation below existing pipelines in multi-Layered Soils. On the basis of the Layered soil model, to consider the soil nonhomogeneous characteristic, the finite element method and boundary element method are coupled to simulate the deformation of existing pipelines induced by tunneling. The solutions indicate that good agreements are obtained between the proposed coupling numerical method and the commercial software. The accuracy of the proposed numerical method is better than the two stages method based on the existing closed-form solutions. Moreover, the results discussed in this paper show that the error obtained by the previous method of weighted average on the basis of homogeneous half space converted from Layered Soils is not negligible for the obvious difference of elastic parameters among successive layers. Copyright © 2012 John Wiley & Sons, Ltd.
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effects of tunnelling on existing pipelines in Layered Soils
Computers and Geotechnics, 2012Co-Authors: Chenrong Zhang, Maosong HuangAbstract:Abstract Soil movements caused by tunnel excavation can adversely affect and even damage underground pipelines in the vicinity. This paper provides a continuous elastic analysis in finite difference form aimed at simulating the responses of both continuous and jointed pipelines subjected to tunnel-induced soil movement in multi-Layered Soils. The effects of soil stratification on pipeline behaviour are analysed using the mathematical Hankel transform and transfer matrix technique, and the behaviour of the joints of a hinged pipeline is modelled as a plastic hinge. The accuracy of the proposed method is verified by comparison with a published study of elastic solutions used in homogeneous soil and centrifuge model tests. Finally, two case studies and a parametric analysis of the effects of different soil profiles in a sandwich soil model are presented to demonstrate the performance of the proposed method.
Stavros A Savidis - One of the best experts on this subject based on the ideXlab platform.
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upper bound analysis of tunnel face stability in Layered Soils
Acta Geotechnica, 2014Co-Authors: Xiaowu Tang, Wei Liu, Bettina Albers, Stavros A SavidisAbstract:The working face of tunnel constructions has to be kept stable during tunneling to prevent large soil deformations or fatal failure. In Layered Soils with lower cohesion, failures happen more often and more abrupt than in cohesive Soils. Therefore, the maintenance of a proper support pressure at the tunnel working face is of high importance. In this paper, an upper bound analysis is introduced to investigate the minimum support pressure for the face stability in Layered Soils. A three-dimensional kinematically admissible mechanism for the upper bound analysis is improved to model potential failure within different soil layers. An analytical solution for the support pressure assessment is achieved. The influence of the crossing and cover soil on the face stability is analyzed, respectively. This solution provides an analytical estimation of the minimum support pressure for the face stability. It may be used as a reference for projects under similar conditions.
Rao S Govindaraju - One of the best experts on this subject based on the ideXlab platform.
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a conceptual model for infiltration in two Layered Soils with a more permeable upper layer from local to field scale
Journal of Hydrology, 2011Co-Authors: Corrado Corradini, Renato Morbidelli, Alessia Flammini, Rao S GovindarajuAbstract:Summary A conceptual model with a semi-analytical formulation for estimating the expected field-scale infiltration in two-Layered Soils is proposed here. At the local scale, an upper layer with a vertically homogeneous saturated hydraulic conductivity, K 1 s , much greater than that of subsoil, K 2 s , is considered. The basic element of the local model is the relatively simple mathematical representation of infiltration as a function of time. This representation depends on whether the dynamic wetting front is entirely within the upper layer when surface saturation occurs, or if the front has moved past the interface into the subsoil at the time to ponding. This local-scale infiltration model is found to be very accurate when compared to the Richards equation. Moreover, the local model clearly identifies if infiltration is controlled by rainfall, the top soil layer, or the bottom soil layer. For upscaling to field-scale, K 1 s is represented by a spatial horizontal random field while K 2 s for the subsoil is assumed constant. Areally-averaged infiltration is obtained by integrating the local infiltration equations. Monte Carlo simulations over a vertical soil profile representative of a sandy loam top soil and a clay loam subsoil are performed for constructing the ensemble averages of field-scale infiltration to be used for model testing. The simulations reveal that the proposed model shows promise for field-scale infiltration computations with errors referred to the aforementioned numerical benchmark typically less than 10% and 5% for infiltration rates and cumulative infiltration, respectively. Conditions when spatial variability in infiltration properties of the top soil can be neglected are identified.
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a parameterized model for local infiltration in two Layered Soils with a more permeable upper layer
Journal of Hydrology, 2011Co-Authors: Corrado Corradini, Renato Morbidelli, Alessia Flammini, Rao S GovindarajuAbstract:Summary A simple conceptual model for local infiltration into a two-Layered soil profile with the upper layer much more permeable than the subsoil is proposed. It is a reformulation of a conceptual model of Corradini et al. (2000) [J. Hydrol. 273, 58–73] involving coupled ordinary differential equations that was developed for infiltration and soil water content distribution in a two-Layered soil under any rainfall pattern. The simpler model framework proposed here is restricted to the estimate of infiltration rate alone in cases where the upper layer is more permeable than the lower one. First, the maximum value, K 1 h , of the saturated hydraulic conductivity of the upper soil, K 1 s , that yields the time to ponding while the dynamic wetting front is entirely within this homogeneous layer is defined by a conceptual approach. Then, parameterized forms for the time when the wetting front reaches the interface, for time to ponding associated with K 1 s ⩾ K 1 h , and for the suction head at the interface as a function of time are determined. With these functional forms, the current model utilizes algebraic equations for ponding time and soil infiltration capacity, thus providing substantial savings in computational effort for describing infiltration in two-Layered Soils. When compared to the detailed conceptual model, the proposed model represents the infiltration rate accurately, with less than 10% average error on the dynamic cumulative infiltration depth. This simplified model offers potential for upscaling to field-scale infiltration over Layered Soils exhibiting spatial heterogeneity.