THE PROBLEM

A grade separated crossing of provincial road 632 Nowe Miasto - Nasielsk over rail line E-65 was required. However, an adjacent road created width restrictions that did not leave enough space for a traditional approach embankment.

THE SOLUTION

Confine the approach embankments within parallel retaining walls constructed using the  TensarTech™ Wall System.

PROJECT DESCRIPTION

The provincial road 632 crossed the railway line E-65 at the same level before the construction upgrade commenced. The main objective of rebuilding the line was to increase the speed of trains to 200km/h, which resulted in the necessity of replacing the grade crossing by constructing an overbridge in its place.

During the project, three vertical retaining walls were constructed using the TensarTech system - precast modular concrete blocks facing reinforced soil structures reinforced with Tensar uniaxial geogrids.

Retained heights ranged from 1m to about 11m, and wall lengths from 80m to over 200m were required. The structures were reinforced by Tensar uniaxial geogrids spaced every third block connected to the modular block facing using Tensar’s high efficiency polymer connector. Directly behind the facing, a 300 mm wide drainage layer was installed to lead the water outside the reinforced soil block.  Due to weak ground conditions, a Tensar Mechanically Stabilised Layer (MSL) was proposed beneath the reinforced soil wall. The MSL is a composite made from layers of Tensar® TriAx® geogrids acting together with a well graded granular fill. The objective was to stabilise the subgrade under a block of reinforced soil and to create a uniform distribution of stresses on the subgrade.

The project was completed in the first quarter of 2012.