Abstract. Landslide in Indonesia usually occurs during the rainy seasons. Previous studies showed that rainfall infiltration has a great effect on the factor of safety (FS) of slopes. This research focused on the effect of rainfall pattern on the FS of unsaturated slope with different slope angle i.e.: 30°, 45°, and 60°. Three different rainfall patterns, which are normal, advanced, and delayed were considered in the analysis. The effects of low or high hydraulic conductivity of the soil are also observed. The analyses were conducted with SEEP/W for the seepage and SLOPE/W for the slope stability. It is found that the lowest FS for gentle slope is reached under the application of advanced rainfall pattern and the lowest FS for steep slope is reached under the application of delayed rainfall pattern. Reduction of FS is known to be the largest for gentle slope rather than steep slope due to negative pore water pressure reduction and the rising of ground water level. The largest FS reduction caused by rainfall was achieved for gentle slope under advanced rainfall pattern.

A landslide has been one of the many problems in geotechnical engineering, whereas, from one of the cases, a failure happened at the interface layer between the overburden and its underlying soil. As interface shear strength has become one of the growing topics in research, this paper summarizes and discusses the research development of interface shear strength and its possibility to explain the interface shear behavior at a slope. The discussion was limited to cohesive soils and experiment-based behavior of the interface shear. Some research has been selected in order to understand the development of interface shear strength through time and two examples of slope interlayer shear behavior were selected. It was known that there are three common tests of interface shear behavior used: simple shear, direct shear, and ring shear test. The development of interface shear strength started at 1960s between soil and construction materials where the four major components were defined. As the research grows, many other types of soils, interfaces, and the effect of the tests became the topic of the research. In the end, the examples given from modeling the interface shear behavior from a slope gives a new perspective of cases for interface shear strength in slope analysis.

No abstract

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.