Finite Element Analysis of Seepage and Exit Gradient underneath Jinnah Barrage Weir Foundation by Using Geo-Slope (Slope/W) Software

Abstract

In the present research work a slave program (SEEP/W) of a Geo-Slope Software, was used to compute the seepage flux and exit gradient under Jinnah barrage weir foundation. 2-D FE model was generated by using four types of elements, i.e. triangular, square, rectangular and trapezoidal. Water seepage is one of the major issues which is to be encountered emphatically as main structure of the weir very much dependent on seepage due to obvious reasons. Based on the pertinent technical data at its original shape and size at the time of construction the seepage and exit gradient was carried out numerically and further the exit gradient was compared with Khosla’s Method. The results showed that at lowest water level at the upstream of the barrage; minimum seepage (5.0995 × 10^-6 m³/sec/m) and at the highest water level maximum seepage (6.7994 × 10^-6 m³/sec/m) occurs respectively. The exit gradient for all the scenarios was found within the permissible limits of (0.25 to 0.20) for single material; which conforms the safety criteria of the weir. The theoretical and simulated exit gradient values was compared to counter check the efficiency of numerical model which showed that amongst all the data sets the RMSE, ME, and AMRE was found (0.007354), (0.006180), and 0.98% respectively. The performance efficiency of the model was founded as 99.995%. The FE model was also verified by comparing the theoretical and simulated values of exit gradient which showed that the slope line was observed to be approximately at 45 degree; which is an evidence that there was no significant difference between theoretical and simulated exit gradient values. Thus it is concluded that theoretical values of exit gradient are not much different than the simulated one.