Effect of placement of horizontal drain in irrigation channel on the slope stability in Neka plain channel

One of the sensitive and important problems during construction projects، such as choosing the spot in concrete or earth dams، open channel، choosing the highway، main road or sub road and etc، is studying the pore water pressure through the embankment and supplying their stability. One of the instability and failure reasons of slope is pore water pressure. This phenomenon، especially in moist region and in sites with saturated clay soils، is clear. Water pheratic level changes cause changing in pore water pressure in embankment which cause decrease in safety factor. In this paper and for a case study، effectiveness of horizontal drain in safety factor is done with PLAXIS-V8. 2 in three conditions (maximum level، rapid drawdown and slow drawdown) is evaluated which safety factors obtained 1. 6، 1. 73 and 2. 8 respectively. With location of horizontal drain، maximum increase for safety factor occurred when drain located in the roof which for rapid drawdown، slow drawdown and maximum water level equal to 1. 62، 2. 03 and 2. 8 respectively. The results indicate that horizontal drains role in slope stability is impressive and pore water pressure is a main factor in this regard. With change location of the horizontal drain، pore water pressure calculated by use two PLAXIS and PLAXFLOW software. Minimum pore water pressure equal to -63. 58 and -63. 60 respectively، obtained.