Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 53 4 2021 06 22 Performance of horizontal and chimney drainage in stability of retaining wall of earthen slopes Performance of horizontal and chimney drainage in stability of retaining wall of earthen slopes 1307 1322 3703 10.22060/ceej.2019.16868.6379 FA Meysam Nourighanli Urmia university Farzin Salmasi university of tabriz 0000-0002-1627-8598 Journal Article 2019 08 02 Due to heavy rainfall, underground water level, and pore water pressure increase each year, which can cause the  failure of the earthen slopes. A retaining wall is one of the main structures that is used to increase the stability of the earthen slope. In the present study, the stability of earthen slopes relative to the critical hydrological cases was simulated by Slope/w software, and the pore pressure behind the retaining walls over 10-meter height which causes instability was simulated using Seep/w software. The studied parameters are precipitation intensity, soil type, position and, the diameter of drainage. Also, the kind of drainage has been considered as a variable parameter and horizontal and chimney drainages were used. Results showed that for fine-grained soils with intensive rain conditions, using one horizontal drainage could not provide the stability of the retaining wall. While in the same conditions, for coarse-grained soils, the retaining wall will be stable by using one horizontal drainage and drainage will be able to discharge all of the excess water behind the retaining wall. Also, the chimney drainage system provided the best results and the stability of the retaining wall did not face any danger under the worst circumstances. For the overturning moment and water pore pressure behind the wall, linear and non-linear regression relations were produced in dimensionless form. The accuracy of the regression relations was proper and acceptable results could be expected. Due to heavy rainfall, underground water level, and pore water pressure increase each year, which can cause the  failure of the earthen slopes. A retaining wall is one of the main structures that is used to increase the stability of the earthen slope. In the present study, the stability of earthen slopes relative to the critical hydrological cases was simulated by Slope/w software, and the pore pressure behind the retaining walls over 10-meter height which causes instability was simulated using Seep/w software. The studied parameters are precipitation intensity, soil type, position and, the diameter of drainage. Also, the kind of drainage has been considered as a variable parameter and horizontal and chimney drainages were used. Results showed that for fine-grained soils with intensive rain conditions, using one horizontal drainage could not provide the stability of the retaining wall. While in the same conditions, for coarse-grained soils, the retaining wall will be stable by using one horizontal drainage and drainage will be able to discharge all of the excess water behind the retaining wall. Also, the chimney drainage system provided the best results and the stability of the retaining wall did not face any danger under the worst circumstances. For the overturning moment and water pore pressure behind the wall, linear and non-linear regression relations were produced in dimensionless form. The accuracy of the regression relations was proper and acceptable results could be expected. https://ceej.aut.ac.ir/article_3703_7d2a383e54274888b4b73b97e1aaa491.pdf