Investigation of performance of horizontal drains in increasing slope stability in intense rain conditions by numerical simulation

Every year heavy rainfalls cause many slope failures. In these rainfalls, the groundwater table increases that cause in increasing of pore water pressure and reduction of slope stability. Using of horizontal drains is an effective and economic method to control the slope stability in this condition. The purpose of this study is to investigate the performance of horizontal drains in increasing slope stability. For this purpose, the SEEP/W and SLOPE/W (subgroups of Geo-Studio software) were implemented. Results showed that increasing in the length, thickness, and number of horizontal drains causes increasing in slope stability during the heavy rainfalls and keep the slope more stable. In addition, installation of drains in the down part of slope is more effective than in the middle or top part of the slope. Relative drain length equal to 0.4 is proper for improving of slope stability. Increasing of drain thickness have more positive effect on slope stability than the drain length.