Abstract:
Railway embankment construction is a very familiar and one of the most critical subject in the construction world. Being such a sensitive and important structure, it is very important to design the embankment properly and to construct the same complying all the codal as well as design specifications. Some of the most critical parameters of a railway embankment design are (A) sub-soil condition and fill material for the embankment, (B) ground water table, (C) dynamic as well as static loads during operation, (D) geometry of the embankment. This paper covers probable reasons for the initial collapse and proposed restoration scheme for the railway embankment in the eastern part of India.
In the above mention location it was seen that an embankment collapse occurred during the peak time of the rainy season. The embankment adjacent to the railway track got settle vertically along with the side shifting of a cantilever retaining wall placed at the bottom part of the embankment. From the available geotechnical report it is seen that half of the portion adjacent in the embankment profile where the embankment height is gradually decreasing from maximum height , the sub soil strata is stiff to hard clay having an undrain cohesion value of around 50kpa followed by dense sand, while in the rest half portion the sub soil strata is soft clay having undrain strength of 15kpa followed by dense sand. As a result in the rainy season due to the sudden increase in the water table the self-weight of the embankment increased and further causing the under laying soft clay to get squeezed away and settle. Due to this squeeze / settlement effect of the soft clay layer the retaining wall got disturbed along with the generation of an undulated embankment top profile.
As a remedial measure, it is proposed to construct a contiguous bored pile wall at the toe of the embankment to make slope stable and additionally compaction grouting is recommended beneath the embankment to improve the soft clay. In order to carry out the analysis, certain commercial geotechnical software like Slide, wallap and Plaxis 2D are used. The factor of safety of the embankment slope considering the above restoration scheme is adequate under static and seismic condition.
Abstract: Theme 1