Speeding up the journey from Surat to Bharuch

National Highway Authority of India

Project Title Speeding up the journey from Surat to Bharuch
Owner National Highway Authority of India
Contractor Name IRB Infrastructure Developers Ltd.
Max. Height of Wall 10.5m
Project type Construction of Reinforced Soil Wall using StrataGrid
Location Surat - Bharuch (NH- 8 in the state of Gujarat)
System Offered StrataGrid + StrataBlock
Consultant STUP Consultants Pvt. Ltd.
Completion Year 2009

Project Brief

The section of the National Highway (NH – 8), connecting Surat to Bharuch needed a site solution that would create additional roadway access to the prevailing high density in order to ease the traffic on the National Highway. The National Highway Authority decided to construct three flyovers and one vehicular underpass. The StrataBlock reinforced soil wall system was selected due to its ease in construction in constrained spaces, cost benefits and quality assurances.

Challenge

In addition to erection of the structures, a large quantum of blocks were to be casted. The biggest challenge faced by the design team was that each location faced unique problems ranging from erratic soil conditions to seepage water. The onsite soil investigation report, which was carried out to assess the bearing capacity of the soil indicated the soil was weak which could lead to excessive settlement of the structures. The results of the Standard Penetration Test (SPT) showed a variation from 7 to 21 indicating erratic ground conditions. The depth also varied from 1.5m to 4.0m. From 3.0m downwards, the soil profile consisted of blackish yellow plastic silt clay with sand and natural moisture content which was less than the plastic limit. Seepage (ground) water was present near the base (leveling pad) of the proposed site of construction of reinforced soil wall. About 25m of the area was subjected to seepage water.

Strata Solution

Based on the prevailing soil conditions, reinforced soil wall system was the most preferred solution for this project. StrataGrid and StrataBlock units were used for the construction of the reinforced soil wall due to their proven performance and easy installation procedure. The StrataBlock system has been used as it has a built-in-slope, is self-aligning and cast with an inter-locking system. Faced with problems of tough soil properties and ground water, the innovative design team at Strata revamped the designs of the structures to address these problems. Federal Highway Administration – National Highway Institute (FHWA) guidelines were followed and at the same time comprised checks for external, internal and global stability under static and seismic conditions. The weakened soil at the site was replaced by well compacted granular soil. The soil below the leveling pad was replaced with graded free draining soil wrapped in geotextile. To address the factor of water pressure the spacing of the StrataGrid reinforcement was reduced above the leveling pad to provide stronger reinforcement.

Benefits to the Client

Strata Geosystems (India) Pvt Ltd, not only completed the structures on time after tackling difficult challenges but also provided the client with superior quality service which was well appreciated by the client. Regular coordination with the client and monitoring the progress of the project on site as well as from the head office was done by the company. This level of efficiency enabled the client to start traffic on the structures on time.