Arifan Jaya Syahbana

Rain-Induced Failure of Railway Embankment at Double Track Lane at Bogor and Its Countermeasure

Open image in new window Slope failure occurred in a 100-m railway embankment between Jakarta and Bogor City during a heavy rainfall period in November 2012, causing disconnection of one railway line and damaged several houses below the railway embankment. Sub-surface investigations and numerical analyses were carried out to evaluate hydrological and geotechnical conditions of the embankment for the purpose of an immediate embankment reconstruction and a long-term stabilization. The geotechnical drilling data show that a soft clayey silt layer, acting as the slip zone, exists at the top of a volcanic rock layer. The groundwater monitoring data show that a shallow groundwater table exists in the upper and the middle parts of the embankment slope. Based on the geotechnical data, the embankment was then reconstructed using woven geotextile reinforcement. However, the numerical analysis indicates the safety factor of the reconstructed embankment was still below the required safety factor under a low train load and a slow train speed. Under a time and space constraints, one line of bored piles of 1 m in diameter was selected to increase the embankment stability. The numerical analysis showed that the bored pile reinforcement was effective to increase the safety factor of the embankment slope to more than 1.3 under a train load of 18 tonnes with a maximum speed of 80 km/h. The inclinometer data also suggest the effectiveness of this bored pile for long-term stabilisation of the new embankment.

Open image in new windowUnderstanding of Landslide Movement at Bumi Waluya Railway Station, Garut, Indonesia

Mitigation of a slow-moving landslide hazard requires a good knowledge of the landslide movements. This paper presents results of geophysical investigation and slope movement monitoring to understand the characteristics of an active landslide above a railway station in Garut, Indonesia. For this purpose, a series of resistivity surveys was then conducted using a dipole-dipole method to map the hydrological condition of the landslide area, and geotechnical monitoring was conducted to characterize the movement. Based on the N–S resistivity profiles, highly saturated zones, indicated by low resistivity values, exist in soil layers at a depth greater than 7.5 m. The saturated zone also develops in the near-surface soil layer in the landslide body. The slope movement monitoring records suggest that the landslide consists of several landslide segments with different rates of movement and deep sliding zone. Based on this current study, the characteristics of landslide movement is very site specific and is mainly associated with localized hydrological conditions. Because the surface water infiltration from the irrigation ditches and rice fields controls the landslide reactivation, a better surface water and sub-surface water management is, therefore, necessary to reduce the landslide risks to the railway infrastructures.