Issues‎ > ‎vol4n5en‎ > ‎


Effect of the existence of under drain on Uplift pressure and Exit Gradient.
Prof. Dr.Rafa Hashim Al-Suhili , Goran O.Hussien 

  Civil Eng. Dept. City College of New York, New York, USA ,Irrigation Engineering Dept. , Collage of Engineering , University of Sulaimania, Iraq

Received : 19/02/2017, Accepted : 06/09/2017
DOI Link:

    The effects of the existence of an under drain pipe beneath the foundation of a hydraulic structure, on both the uplift pressure under the structure and the exit gradient on its downstream side are investigated.  More specifically the effect of the horizontal and vertical locations and the diameter of this under drain pipe were investigated. The Geo-Studio Seep/w software is used for simulating different geometrical configurations of a typical hydraulic structure model. Results indicate that the existence of this drain will reduce the pressure head beneath the foundation of the structure. The observed reduction in uplift pressure is found huge. As the drain diameter increases the pressure head decrease more and more. This results in a  required volume against overturning to decrease with using greater diameter which is tend to 100% decrease in (V) especially where the under drain location near u/s sheet pile (location –D-). The exit gradient decrease with using drain pipe near upstream sheet pile but it increase where the drain pipe below downstream sheet pile especially (location-G-) which is downstream length of protection (L) increase from (2.837m for without drain) to (4.70 m with location G) that means about  65.67% increase.

KEYWORDS :under drain, Hydraulic Structures, foundation

1. Al-Suhaili R. S. H., & Karim, R. A., (2014), “Optimal Dimensions of Small Hydraulic Structure Cutoffs Using Coupled Genetic Algorithm and ANN Model” Journal of Engineering Number 2 Volume 20 February 2014
2. El-Jumaily, and AL-Bakry, (2013), “Seepage Analysis Through and under Hydraulic Structures Applying Finite Volume Method” Eng. &Tech. Journal, Vol. 31,Part (A), No.9, 2013
3. Mussawi, W. A., (2006), “Optimum Design of Control Devices for Safe Seepage under Hydraulic Structures” Journal of Engineering and Development, Vol. 10, No.1, March (2006) ISSN 1813-7822
4. Azizi, S. et al., (2012), “Weep Hole and Cut-off Effect in Decreasing of Uplift Pressure (Case Study: Yusefkand Mahabad Diversion Dam” Journal of Civil Engineering and Urbanism Volume 2, Issue 3: 97-101 (2012.)
5. Al-Suhaili R. S. H., (2009), “Analytical solution for exit gradient variation downstream of inclined sheet pile” the 6th engineering conference college of engineering 5-7-April 2009 .
6. Mansuri B., Salmasi F., (2013) “Effect of Horizontal Drain Length and Cutoff Wall on Seepage and Uplift Pressure in Heterogeneous Earth Dam with Numerical Simulation” Journal of Civil Engineering and Urbanism Volume 3, Issue 3
7. Shayan H. K., Tokaldany E. A., (2015) “ Effects of blanket, drains, and cutoff wall on reducing uplift pressure, seepage, and exit gradient under hydraulic structures” International Journal of Civil Engineering, Vol. 13, No. 4A, Transaction A: Civil Engineering, December 2015
8. Geo-Studio Seep/w software/(
9. Das, B. M.,(2008), ”Advanced Soil Mechanics" Third Edition. Taylor and Francis, 270 Madison Ave, New York, NY 10016, USA.
10. Mansuri, B., et al., (May 2014), “Effect of Location and Angle of Cutoff Wall on Uplift Pressure in Diversion Dam” Geotechnical and Geological Engineering • May 2014
11. Varshney, R.S., Gupta, S.C. and Gupta, R.L., 1977. Theory & design of irrigation structures.