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Numerical simulation of the free surface and water inflow of a slope, considering the nonlinear flow properties of gravel layers: a case study

Groundwater is an important factor of slope stability, and 90% of slope failures are related to the influence of groundwater. In the past, free surface calculations and the prediction of water inflow were based on Darcy's law. However, Darcy's law for steady fluid flow is a special case of...

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Autores principales: Yang, Bin, Yang, Tianhong, Xu, Zenghe, Liu, Honglei, Shi, Wenhao, Yang, Xin
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society Publishing 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5830793/
https://www.ncbi.nlm.nih.gov/pubmed/29515904
http://dx.doi.org/10.1098/rsos.172109
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author Yang, Bin
Yang, Tianhong
Xu, Zenghe
Liu, Honglei
Shi, Wenhao
Yang, Xin
author_facet Yang, Bin
Yang, Tianhong
Xu, Zenghe
Liu, Honglei
Shi, Wenhao
Yang, Xin
author_sort Yang, Bin
collection PubMed
description Groundwater is an important factor of slope stability, and 90% of slope failures are related to the influence of groundwater. In the past, free surface calculations and the prediction of water inflow were based on Darcy's law. However, Darcy's law for steady fluid flow is a special case of non-Darcy flow, and many types of non-Darcy flows occur in practical engineering applications. In this paper, based on the experimental results of laboratory water seepage tests, the seepage state of each soil layer in the open-pit slope of the Yanshan Iron Mine, China, were determined, and the seepage parameters were obtained. The seepage behaviour in the silt layer, fine sand layer, silty clay layer and gravelly clay layer followed the traditional Darcy law, while the gravel layers showed clear nonlinear characteristics. The permeability increases exponentially and the non-Darcy coefficient decreases exponentially with an increase in porosity, and the relation among the permeability, the porosity and the non-Darcy coefficient is investigated. A coupled mathematical model is established for two flow fields, on the basis of Darcy flow in the low-permeability layers and Forchheimer flow in the high-permeability layers. In addition, the effect of the seepage in the slope on the transition from Darcy flow to Forchheimer flow was considered. Then, a numerical simulation was conducted by using finite-element software (FELAC 2.2). The results indicate that the free surface calculated by the Darcy–Forchheimer model is in good agreement with the in situ measurements; however, there is an evident deviation of the simulation results from the measured data when the Darcy model is used. Through a parameter sensitivity analysis of the gravel layers, it can be found that the height of the overflow point and the water inflow calculated by the Darcy–Forchheimer model are consistently less than those of the Darcy model, and the discrepancy between these two models increases as the permeability increases. The necessity of adopting the Darcy–Forchheimer model was explained. The Darcy–Forchheimer model would be applicable in slope engineering applications with highly permeable rock.
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spelling pubmed-58307932018-03-07 Numerical simulation of the free surface and water inflow of a slope, considering the nonlinear flow properties of gravel layers: a case study Yang, Bin Yang, Tianhong Xu, Zenghe Liu, Honglei Shi, Wenhao Yang, Xin R Soc Open Sci Earth Science Groundwater is an important factor of slope stability, and 90% of slope failures are related to the influence of groundwater. In the past, free surface calculations and the prediction of water inflow were based on Darcy's law. However, Darcy's law for steady fluid flow is a special case of non-Darcy flow, and many types of non-Darcy flows occur in practical engineering applications. In this paper, based on the experimental results of laboratory water seepage tests, the seepage state of each soil layer in the open-pit slope of the Yanshan Iron Mine, China, were determined, and the seepage parameters were obtained. The seepage behaviour in the silt layer, fine sand layer, silty clay layer and gravelly clay layer followed the traditional Darcy law, while the gravel layers showed clear nonlinear characteristics. The permeability increases exponentially and the non-Darcy coefficient decreases exponentially with an increase in porosity, and the relation among the permeability, the porosity and the non-Darcy coefficient is investigated. A coupled mathematical model is established for two flow fields, on the basis of Darcy flow in the low-permeability layers and Forchheimer flow in the high-permeability layers. In addition, the effect of the seepage in the slope on the transition from Darcy flow to Forchheimer flow was considered. Then, a numerical simulation was conducted by using finite-element software (FELAC 2.2). The results indicate that the free surface calculated by the Darcy–Forchheimer model is in good agreement with the in situ measurements; however, there is an evident deviation of the simulation results from the measured data when the Darcy model is used. Through a parameter sensitivity analysis of the gravel layers, it can be found that the height of the overflow point and the water inflow calculated by the Darcy–Forchheimer model are consistently less than those of the Darcy model, and the discrepancy between these two models increases as the permeability increases. The necessity of adopting the Darcy–Forchheimer model was explained. The Darcy–Forchheimer model would be applicable in slope engineering applications with highly permeable rock. The Royal Society Publishing 2018-02-28 /pmc/articles/PMC5830793/ /pubmed/29515904 http://dx.doi.org/10.1098/rsos.172109 Text en © 2018 The Authors. http://creativecommons.org/licenses/by/4.0/ Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.
spellingShingle Earth Science
Yang, Bin
Yang, Tianhong
Xu, Zenghe
Liu, Honglei
Shi, Wenhao
Yang, Xin
Numerical simulation of the free surface and water inflow of a slope, considering the nonlinear flow properties of gravel layers: a case study
title Numerical simulation of the free surface and water inflow of a slope, considering the nonlinear flow properties of gravel layers: a case study
title_full Numerical simulation of the free surface and water inflow of a slope, considering the nonlinear flow properties of gravel layers: a case study
title_fullStr Numerical simulation of the free surface and water inflow of a slope, considering the nonlinear flow properties of gravel layers: a case study
title_full_unstemmed Numerical simulation of the free surface and water inflow of a slope, considering the nonlinear flow properties of gravel layers: a case study
title_short Numerical simulation of the free surface and water inflow of a slope, considering the nonlinear flow properties of gravel layers: a case study
title_sort numerical simulation of the free surface and water inflow of a slope, considering the nonlinear flow properties of gravel layers: a case study
topic Earth Science
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5830793/
https://www.ncbi.nlm.nih.gov/pubmed/29515904
http://dx.doi.org/10.1098/rsos.172109
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