GROUND IMPROVEMENT USING PRE-FABRICATED VERTICAL DRAIN ALONG WITH

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Basal Reinforcement

1969

TRIPURA - NORTHEAST - India

Ircon International Limited

Nayak and Triveni

NIT Agartala

GROUND IMPROVEMENT USING PRE-FABRICATED VERTICAL DRAIN ALONG WITH

Problem

Agartala- Akhaura rail project is proposed to help increase railway connectivity between the two countries (india and Banagladesh). The Agartala Akhaura rail project was conceptualized in 2010. Later, India and Bangladesh signed a Memorandum of Understanding (MoU) on a couple of issues including the rail project in 2013. The 15.054 km long rail project in west Tripura district proposed to be constructed. It connects Akhaura in Bangladesh with Tripura’s capital Agartala through Nischintapur in the Indo-Bangla border. The railway track with embankment at different location is proposed. From chainage Ch 3+900 to Ch 5+100, the foundation stratum was found very weak soft clayey soils with maximum percentage of decomposed wood and which extends up to greater depth. Sand is not easily available as drainage layer. The bearing capacity of such soil is very low and settlement would be excessive. Hence, IRCON approached M/s Maccaferri Environmental Solutions Pvt. Ltd. to carry out the design for the ground improvement from Ch 3+900 to Ch 5+100.

Solution

Considering the extremely challenging site situation in terms of weak, compressible foundation strata, Maccaferri suggested the pre-fabricated vertical drain MacDrain V (PVD) with basal reinforcement ParaLink (BBA certified high strength uniaxial geogrid) as the ground improvement solution. The prefabricated vertical drain and basal reinforcement were provided as per IS15428 part II and IRC 113. In order to study the performance of compressible soils under reclaimed fill, geotechnical instruments like piezometers and settlement gauges were installed. Along with prefabricated vertical drains MacDrain V, the preloading of 6-9m was constructed for accelerated consolidation of soft soil. The preloading period was of 4 months to achieve appx 90% consolidation. A layer of ParaLink was laid for rotational stability and load distribution. Layer of MacDrain was used replacing conventional drainage layer of sand/gravel.