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Ground improvement programme at JNPT

Ground Improvement for Road Projects – A case study for JNPT Road connectivity

Introduction Part of SH-54 (section of JNPT Road connectivity) passes through marshy soil having depth 3.0 m – 15.0 m. Properties of soft marine clay were found as follows: -	Natural moisture content	:	50 – 80 % -	Liquid limit			:	46 – 91 % -	Plastic limit			:	27 – 34 % -	Cohesion (kg / sqcm)	       :	0.10 -	Compression Index		:	0.55 -	Initial void ratio		:	1.70 -	Coefficient of consolidation	:	1.25 (m2/year) -	Ratio Ch/Cv			:	1.5

Following proposals were made to take the load of embankment & vehicular traffic safely & to restrict the post construction settlement within permissible limit: 1. Removal & replacement of soft clay upto 3.0m 2. PVD with strength geo-textile for soft clay for depth 3.0 m – 15.0 m. High strength geo-textile (200 KN/m2) were proposed for placing 3-4 m preloading in a single stage. This ensured uniform settlement below preloaded embankment. PVD @.15 m in triangular grid upto hard strata.

Following conclusions are made: -	Marshy land can be successfully used for construction by appropriate ground improvement technique. -	Geosynthetics can be successfully used for speedy construction of road (allowing single stage preloading by distributing load over a wider area. -	About 90 % theoretical settlement achieved using appropriate technique, proper selection of material & its careful installation. -	Piezometer, settlement gauge & inclinometer installed for monitoring performances.