Document Type : Original Article

Authors

1 : Associate Professor, Department of Water Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran.

2 Ph.D. Candidate of Hydraulic Structures and Water Engineering, Department of Water Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran.

Abstract

Extended Abstract



Probabilistic Analysis of Seepage in Earth dam by using Monte Carlo Simulation and Considering Soil Permeability and Body Geometry





Introduction

Seepage through the soil is one of the most important issues of Fluid-Structure Interaction (FSI) that can lead to liquefaction, boiling of sand in downstream, settlement of hydraulic structures, instability and failure of embankments and earth dams. Accurate calculation of the amount of leakage passing through the earthen dam is an important factor in ensuring its safety and stability. On the other hand, the results of seepage analysis in calculating the dimensions of drainage and filters of the dam deformation is very important (Kalateh and Afshari, 2018; Jafarzadeh and Asadnia, 2005).



Methodology

To deterministic solving of the Laplace equation in soil medium is performed by Smith and Griffiths (2004), FORTRAN programming code is written that calculates the flow rate and piezometric head in the body of a homogeneous and non-homogeneous earth dam. The FORTRAN code for solving seepage equations is similar to the code for solid mechanics equations. In this code, inspired by solving the equations of static and dynamic equilibrium in solid mechanics and using the finite element method, the differential equation of seepage is solved with the difference that instead of displacement and force components in mechanical problems of seepage and pizometric head is used.

In the present paper, a program based on the finite element method in FORTRAN programming language has been developed by the author that solves the Laplace equations to determine the leakage discharge of an earth dam assuming the uncertainty of the components involved. In fact, in the previous code related to seepage, soil permeability has been considered definitively, which in this study is probabilistically investigated.

First, the FORTRAN code is assumed that the permeability values of the materials are constant, and the results are expressed as two leakage currents, input and output, in which case these two values are equivalent. The results show that in the isotropic state where the permeability is equal in the vertical and horizontal directions, the slope of the line is greater than the two non-isotropic states.

As mentioned for deterministic modeling, the permeability of dam materials is constant in this case and is solved analytically by the Seep_4 subroutine, but in the probabilistic model and the Monte Carlo method, instead of the stability of the conductivity coefficient, the mean and standard deviation are entered in the calculations.



Results and Discussion

Figure 1 shows the relationship between the average seepage resulting from Monte Carlo Simulation for downstream reservoir ratios of 0.087, 0.136 and 0.19, which shows a graph in the range of 0.71<Kx/Ky<1 inequality slope. It has an ascending interval of 1<Kx/Ky<1.41 To be more precise, the slope of the descending section in the definite position for downstream ratios to the reservoir is 0.087, 0.136 and 0.19, respectively, equal to 0.96, 0.96 and 0.48 in the descending position and 0.73. 0, 0.88 and 1.032 are in the ascending state, with no significant difference. But in probabilistic mode for downstream ratios to reservoir 0.087, 0.136 and 0.19 with 0.41, 0.48 and 0.069 in descending mode and 0.78, 0.91 and 1.032 respectively is in the ascending state, in which the slope of the ascending part is at least one and a half times greater in all three states. It is worth mentioning that in all three cases and in both intervals, the coefficient of explanation of the linear relationship is above 0.98, which was calculated by SPSS software and linear regression method.



Fig 1-a- Average seepage flow of earthen dam for changes in horizontal to vertical permeability ratio (Kx/Ky) in deterministic analysis. 1-b- The amount of flow through the Earth dam in change for changes in the ratio of horizontal to vertical permeability (Kx/Ky) in probabilistic analysis.



Conclusions

• In the deterministic analysis, the effect of horizontal permeability on the seepage flow rate not show a significant difference compared to the effect of vertical permeability, but in probabilistic analysis, the effect of horizontal permeability on average of seepage flow rate is at least 89% higher than vertical permeability.

• The results of probabilistic leakage study show that with increasing the ratio of downstream to upstream, the range of discharge in the frequency distribution function (PDF) and the average leakage discharge decreases.

• With decreasing the width of the earthen dam crown, the average seepage flow decreases and with the upward movement of the dam crown, this amount increases.

• In all cases, the average seepage flow calculated in different cases of Monte Carlo Simulation (MCS) models is 16 to 270% less than the seepage flow in the definite case.



Keywords: Uncertainty Analysis, Saturated and Unsaturated Soils, FORTRAN Programming, Porous Media, Finite Element (FE).

Keywords

Main Subjects

Ahmed, A. S., Revil, A., Bolève, A., Steck, B., Vergniault, C., Courivaud, J. R., Jougnot, D., & Abbas, M. (2020). Determination of the permeability of seepage flow paths in dams from self-potential measurements. Engineering Geology Journal, 268, 105514.
Ashnab Advisor Company. (2014). Guide to seismic analysis and design of earthen and gravel dams. Report, Publications of the technical and executive system of the Iran (in Persian).
Carpenter, L. C. (1980, July). Computer rendering of fractal curves and surfaces. In Proceedings of the 7th annual Conference on Computer graphics and interactive techniques, p. 109,‏ July 14 – 18, Seattle, Washington, USA: Association for Computing Machinery.
Casagrande, A. (1937). Seepage through Dams. Journal of New England Water Works Association, 52(2), 131-172.‏
Chang, C. S. (1987). Boundary element method in drawdown seepage analysis for earth dams. Journal of Computing in Civil Engineering, 1(2), 83–98.
Chen, Q., & Zhang, L. M. (2006). Three-dimensional analysis of water infiltration into the Gouhou rockfill dam using saturated unsaturated seepage theory. Canadian Geotechnical Journal, 43(5), 449–461.
Choopan, Y., Emami, S., & Kheiri Ghooje Bigloo, M. (2020). Evaluating Election, Imperialist Competitive Algorithms and Artificial Neural Network Method in Investigating the Groundwater Level of Reshtkhar Plain. Amirkabir Journal of Civil Engineering, 52(6), 1333-1246.‏ Doi: 10.22060/CEEJ.2019.15344.5888.
Dagan, G. (1976). Comment on ‘Stochastic‐conceptual analysis of one‐dimensional groundwater flow in nonuniform homogeneous media’by R. Allan Freeze. Water Resources Research, 12(3), 567-568.
DeGroot, D. J., & Baecher, G. B. (1993). Estimating autocovariance of in-situ soil properties. Journal of Geotechnical Engineering, 119(1), 147–166.
Desai, C. S. (1972). Seepage analysis of earth banks under drawdown. Journal of the Soil Mechanics and Foundations Division, 98(11), 1143–1162.
Dvinoff, A. H., & Harr, M. E. (1971). Phreatic surface location after drawdown. Journal of the Soil Mechanics and Foundations Division, 97(1), 47–58.
Emami, S., Choopan, Y., Kheiry Goje Biglo, M., & Hesam, M. (2020). Optimal and Economic Water Allocation in Irrigation and Drainage Network Using ICA Algorithm (Case Study: Sofi-Chay Network). Irrigation and Water Engineering, 10(3).‏ Doi: 10.22125/iwe.2020.107104.
Fenton, G. A., & Vanmarcke, E. H. (1990). Simulation of random fields via local average subdivision. Journal of Engineering Mechanics, 116(8), 1733–1749.
Fournier, A., Fussell, D., & Carpenter, L. (1982). Computer rendering of stochastic models. Communications of the ACM, 25(6), 371–384.
Freeze, R. A. (1971). Three‐dimensional, transient, saturated‐unsaturated flow in a groundwater basin. Water Resources Research, 7(2), 347–366.
Fukumoto, Y., Yang, H., Hosoyamada, T., & Ohtsuka, S. (2021). 2-D coupled fluid-particle numerical analysis of seepage failure of saturated granular soils around an embedded sheet pile with no macroscopic assumptions. Computers and Geotechnics, 136, 104234.
Gelhar, L. W. (1977). Effects of hydraulic conductivity variations on groundwater flows, in Hydraulic Problems Solved by Stochastic Methods. Water Resources Publications, Fort Collins, Colo, PP. 409-431.
Ghias, M. (2014). An Introduction to the Monte Carlo Simulation Methods. Basparesh, 4(1), 67-77 doi: 10.22063/basparesh.2014.1062.
Giglou, K. A., Biglou, M. K. G., Mehrparvar, B., & Naghadeh, A. S. (2019). Investigating Amount of Leakage, Sediment and Durability in Geosynthetic Cover of Pumping Channel 3 at Irrigation Network of Moghan. Revista Geoaraguaia, 9(2).‏
Griffiths, D., & Fenton, G. A. (1993). Seepage beneath water retaining structures founded on spatially random soil. Geotechnique, 43(4), 577–587.
Gui, S., Zhang, R., Turner, J. P., & Xue, X. (2000). Probabilistic slope stability analysis with stochastic soil hydraulic conductivity. Journal of Geotechnical and Geoenvironmental Engineering, 126(1), 1–9.
Helton, J. C. (1997). Uncertainty and sensitivity analysis in the presence of stochastic and subjective uncertainty. Journal of Statistical Computation and Simulation, 57(1–4), 3–76.
Helton, J. C. (2011). Quantification of margins and uncertainties: Conceptual and computational basis. Reliability Engineering & System Safety, 96(9), 976–1013.
Helton, J. C., & Johnson, J. D. (2011). Quantification of margins and uncertainties: Alternative representations of epistemic uncertainty. Reliability Engineering & System Safety, 96(9), 1034–1052.
Helton, J. C., Johnson, J. D., & Sallaberry, C. J. (2011). Quantification of margins and uncertainties: Example analyses from reactor safety and radioactive waste disposal involving the separation of aleatory and epistemic uncertainty. Reliability Engineering & System Safety, 96(9), 1014–1033.
Jafarian, Y., Nasri, E. (2016). Evaluation of uncertainties in the existing empirical models and probabilistic prediction of liquefaction-induced lateral spreading. Amirkabir Journal of Civil Engineering, 48(3), 275-290. Doi: 10.22060/ceej.2016.674 (in Persian)
Jafarzadeh, F., & Asadnia, M. (2005). Considering Three-and Two-Dimensional Seepage Analysis for Inhomogeneous Earth Dam Constructed in Narrow Valleys, 73RD INTERNATIONAL COMMITTEE OF LARGE DAMS (ICOLD), Tehran, IRAN, Vol 126-S5.
JamshidiChenari, R. and Behfar, B. (2017). Stochastic analysis of seepage through natural alluvial deposits considering mechanical anisotropy. Civil Engineering Infrastructures Journal, 50(2), 233–253.
Johari, A., & Heydari, A. (2018). Reliability analysis of seepage using an applicable procedure based on stochastic scaled boundary finite element method. Engineering Analysis with Boundary Elements, 94, 44–59.
Kalateh, F and Afshari, S. (2018). Three-dimensional analysis of Kalghan dam seepage and evaluation of the alluvial roof on the dam foundation sealing according to software Seep3D (Master Thesis), Faculty of Civil Engineering, Department of Water Engineering, University of Tabriz (in Persian)
Kalateh, F, & Hoseinnejad, F. (2018). Using the Finite Element Method in the Coupled Analysis of Earth Dams and Estimating the Associated Pore Water Pressure. Ferdowsi Civil Engineering, 31(2), 23–40. https://doi.org/10.22067/civil.v31i2.54955 (in Persian)
Kalateh F, Hosseinejad F, Kheiry M. (2022). Uncertainty quantification in the analysis of liquefied soil response through Fuzzy Finite Element method. Acta Geodynamica et Geomaterialia, 19, No. 3 (207), 177–199, 2022. DOI: 10.13168/AGG.2022.0007.
Kheiry Ghojeh Biglou, M., Pilpayeh, A. (2020). Optimization of Height and Length of Ogee-Crested Spillway by Composing Genetic Algorithm and Regression Models (Case Study: Spillway of Balarood Dam). Irrigation and Drainage Structures Engineering Research, 20(77), 39-56. Doi: 10.22092/idser.2019.124750.1368.
Kheiry, M. & Pilpayeh, A. (2019). Effect of geometric specifications of ogee spillway on the volume variation of concrete consumption using genetic algorithm. Revista INGENIERÍA UC, 26(2), 145-153.‏
Kouhpeyma, A., Kilanehei, F., Hassanlourad, M., & Ziaie-Moayed, R. (2021). Numerical and experimental modelling of seepage in homogeneous earth dam with combined drain. ISH Journal of Hydraulic Engineering, 1–11.
Lam, L., Fredlund, D. G., & Barbour, S. L. (1987). Transient seepage model for saturated–unsaturated soil systems: A geotechnical engineering approach. Canadian Geotechnical Journal, 24(4), 565–580.
Lumb, P. (1966). The variability of natural soils. Canadian geotechnical journal, 3(2), 74–97.
Liu, K., Vardon, P. J., & Hicks, M. A. (2018). Probabilistic analysis of seepage for internal stability of earth embankments. Environmental Geotechnics, 6(5), 294–306.
Neuman, S. P. (1973). Saturated-unsaturated seepage by finite elements. Journal of the hydraulics division, 99(12), 2233–2250.
Peck, R. B. (1967). Stability of natural slopes. Journal of the Soil Mechanics and Foundations Division, 93(4), 403–417.
Salami, A.B. (2003). An overview of the Monte Carlo simulation method. Economic Research Journal, 3(8), 117-138.
Sharafati, A. and Mirfakhraee, S. (2019). Uncertainty Analysis of Seepage Flow in Soil Foundation of Small Concrete Dam. Journal of Civil and Environmental Engineering, 49.2(95), 95-105.
Silva, A.V., Neto, S.A.D. and de Sousa Filho, F.D.A. (2016). A Simplified Method for Risk Assessment in Slope Stability Analysis of Earth Dams Using Fuzzy Numbers. Elecronic Journal of Geotechnical Engineering, 21(10), 3607–3624.
Smith, I. M., & Griffiths, D. V. (1998). Programming the finite element method, John Wiley & Sons. 2-nd edition.‏
Smith, L., & Freeze, R. A. (1979a). Stochastic analysis of steady state groundwater flow in a bounded domain: 1. one‐dimensional simulations. Water Resources Research, 15(3), 521–528.
Smith, L., & Freeze, R. A. (1979b). Stochastic analysis of steady state groundwater flow in a bounded domain: 2. two‐dimensional simulations. Water Resources Research, 15(6), 1543–1559.
Vanmarcke, E. H. (1977). Probabilistic modeling of soil profiles. Journal of the Geotechnical Engineering Division, 103(11), 1227–1246.