Investigation of drainage effect stone - sand filling applications for the increase of security of rubble stone walls

In this study, in order to evaluate the effect of stone-sand fillings made on the back of the retaining wall in decreasing the groundwater level, analyzes were carried out using the Plaxis 2D finite element program by using fillers in various sections and selecting different soils. For the analyzes, a stone retaining wall with h=5 m height which has two weep holes and drainage pipe placed on the back was selected. Weep holes and drainage pipe were modeled as well and they were presumed to drain the water at 0.005 m3/day. The soil on which the retaining wall was built was selected as sand, gravel, clay and silt; the backfill made behind the retaining wall was considered as stone, stone and sand, sand. For the analyzes, the fill widths were assumed to be 30-90 cm, 80-140 cm, 130-190 cm and the initial groundwater level was 3,800 m. The permeability coefficients (kx and ky) were assumed to be 86 m/day for sand, 10000 m/day for stone-gravel, 0,005 m/day for clay and 0,09 m/day for silt. Groundwater level changes were obtained by using groundwater levels that emerged as a result of the analyzes. As a result; it has been determined that if the soil on which the retaining wall is built is sand or gravel, it will provide maximum change for the groundwater level by making stone filling with a small width behind the wall; if the soil is clay or silt, sand filling with a small width behind the wall will prevent piping and provide maximum change for the groundwater level.