Evaluation of Ground Anchor Design on Man-made Cut Slope of Cemented Sand: A Case Study

A system of ground anchor and horizontal drain on a steep cut-slope in Bogor, West Java was designed to stabilize the slope below a bridge structure spanning across a river. Due to the difficulties in the construction of the ground anchor, the design of the ground anchor was evaluated and analyzed for its effect on the stability of the slope. The slope is assumed to have three layers of soil consist of sandy clay (medium stiff), sandy silt (hard), sandy silt (medium stiff), and cemented sand gravel. Four scenarios were evaluated to examine the slope stability: initial stage, the addition of horizontal drain, construction of bored piles with horizontal drain, and addition of ground anchor after the construction of bored piles and horizontal drain. Analysis were done with evaluating the Factor of Safety (FS) of the slope. It was found that the addition of horizontal drain played a big part in stabilizing the slope from initial stage (FS = 0.933 to FS = 1.546), whereas the addition of ground anchor and bored piles were not apparent after the addition of horizontal drain (FS = 1.545 and FS = 1.555), indicating that the main problem of the slope was the high groundwater level. Other than the constructed solutions, shortcrete should also be given at the critical slip surface at the top and surface of the slope in order to reduce erosion by run-off water.