Slopes Stability Safety Factor On Existing Condition and After Strengthening by Counterfort Type Retaining Walls

The Middle Aceh / Gayo Lues-Blangkejeren boundary section Km 438 + 775 is one of the Aceh Provincial National roads, which often experiences landslides. Avalanches that occur due to scour of runoff water, lack of optimal drainage and the absence of outlets for water disposal and the soil layer under asphalt pavement consists of loose material . Therefore, it is necessary to study the strength of slopes with Counterfort type retaining walls . This study aims to analyze slope stability by obtaining safety factor figures and identifying patterns of slope collapse by using the Plaxis program and the slice method. The input soil parameters used are dry volume weight, wet volume weight, permeability, young modulus, paisson's ratio , shear angle, cohesion. The results of the analysis of the slope stability in the existing conditions using the Plaxis program and the slice method with a radius of 65.06 meters obtained safety factor figures of 1.038 and 1.079, the slope is not safe (FK <1.25). The results of the analysis after reinforced counterfort type retaining walls and minipile with a length of 12 meters obtained a safety factor of 1.268, unsafe slopes (FK <1.5). Thus, additional reinforcement is needed using anchors. The results of slope stability analysis after being strengthened by counterfort type retaining walls, minipile and anchor with a length of 20 meters and a slope angle of 30 ° obtained a safety factor of 1.513, indicator safe slope (FK> 1.5).