PSI - Issue 5

K Bouzelha et al. / Procedia Structural Integrity 5 (2017) 77–84 K Bouzelha et al./ StructuralIntegrity Procedia 00 (2017) 000 – 000

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Table5: Safety factor F s considering the seismic effect. Parameter Low (I) Medium (IIa)

Medium (IIb)

High (III)

A

0.12

0.2

0.25

0.3

M s (t.m) M m (t.m)

536,658 297,104 1.8062

531,391 313,586 1.6945

527,045 323,763 1.6278

522,677 333,827 1.5657

F s

The influence of the saturation line on the upstream slope of the embankment is also analyzed for the different seismic zones (Table 6). We notice that the safety factors F s are lower than the admissible value (Fs<1.4) given by the Maghreb guide of the small dams design (PNUD, 1987).

Table 6: Safety factor Fs considering the seismic effect and the saturation line. Parameter Low (I) Medium (IIa) Medium (IIb)

High (III)

A

0.12

0.2

0.25

0.3

M s (t.m) M m (t.m)

918,614 907,783

905,074 958,146

895,534 989,486

885,954 1020,699

F s

1.01

0.94

0.91

0.87

The results presented in tables 4, 5 and 6 show that the not taken into account of the seismic effect and the saturation line in engineer calculation can compromise the stability of the embankment. To ensure accuracy of failure probability results obtained, convergence tests were performed for the limit state function, as shown in Fig. 4. These results show that the convergence and the stability of failure probability values are obtained from a number of simulations equal to 20 000. Therefore, the number 30 000 is used to generate Monte Carlo samples.

0,030

0,025

Pf zone I Pf zone IIa Pf zone IIb Pf zone III

0,020

0,015

0,010

0,005 failure probability Pf

Draw number

0,000

10000

20000

30000

Fig. 4. Stability of failure probability P f with draw number.

The evolution of failure probability P f obtained for various seismic zones, without considering the saturation line, is given in Fig. 5. We notice that the failure probability increases with the seismic intensity. In the low seismicity zone, the value of P f is less than the admissible value (P f =10 -3 ) for civil engineering structures (Dehmous et al. 2011), while it is greater than the admissible value in the three other zones.