New Broad Gauge Railway embankment was being constructed between Agartala- Sabroom. Udaipur Station yard was situated on Agartala-Sabroom new railway line project at chainage 41-43.
Earthwork for station yard started in Dec 2010, yard was located in marshy land and no ground improvement measures were adopted before constructing the embankment. Hence, failure of embankment had occurred at few locations in Sept 2011 and March 2012 respectively.
Rehabilitation of Railway track at Udaipur station yard in Agartala- Udaipur-Sabroom New B.G. Line
New Broad Gauge Railway embankment was being constructed between Agartala- Sabroom. Udaipur Station yard was situated on Agartala-Sabroom new railway line project at chainage 41-43.New B.G. Line.Earthwork for station yard started in Dec 2010, yard was located in marshy land and no ground improvement measures were adopted before constructing the embankment. Hence, failure of embankment had occurred at few locations in Sept 2011 and March 2012 respectively.
Railway station yard and Station building site are situated in low lying area previously known as Sukhsagar, consisting of poor quality soil up to 13.25m below ground. During monsoon the whole catchment area was filled up with water and water table was raised even by 3.0 to 4.0 m above the ground level. Constructed embankment divided low lying area in two parts. Water used to flow from upstream to downstream through openings provided in the embankment. The drainage of nearby embankment was very poor. RDSO requested to suggest remedial measures in connection with failure of Railways embankment at Udaipur Station yard. After evaluating various ground improvement techniques; it was decided that Prefabricated Vertical Drain (PVD) is the best solution for accelerating consolidation and reducing pore pressure for the prevailing site conditions.
Soil had moderate swelling in nature and sub soil at
depth below top of embankment had high swelling in nature. Therefore, consolidation of soil
should be accelerated in order to reduce pore pressure and settlement.
Considering the project stretch, the depth of soft strata from bore log was considered up to
13.25m.For design and analysis, the soil was considered as fully submerged. For the stretches,
where soft soil was encountered, 95% consolidation had to be achieved.
A woven geotextile was installed at base to increase the overall stability of the embankment. This
will also act as a separator between embankment fill and drainage layer. The drainage layer was
installed to be of 30cm along with an additional layer of non-woven geotextile as shown in the cross
section. All layers starting with 15 cm of sand layer, layer of nonwoven geotextile, 30 cm thick
drainage layer followed by layer of woven geotextile was proposed to be installed. It was decided to
install settlement gauges and piezometers in order to monitor the consolidation process.
As calculated, time required for 95% consolidation of foundation soil was
143 years; which is too long therefore needed to consider installation of Techdrain (PVD) to
TechdrainPVD (100 days).
The ground improvement was executed on site as per approved scheme along with proposed instrumentations and had performed successfully for the intended purpose with satisfactory results.