THE PROBLEM
By the Göta Älv river, the ground was very soft (Cu<10kPa) with sensitive and very deep clay, which had been the cause of a number of landslips in the past. Due to the low bearing capacity of the ground, the Contractor was faced with significant difficulties gaining site access for construction traffic and the 40 ton rigs for installing the lime-cement (LC) columns in the clay.
THE SOLUTION
The access roads were built with a Tensar MSL™ (Mechanically Stabilised Layer) incorporating two layers of Tensar TriAx geogrids and it was also possible to design for ground with particulary poor ground conditions.
In addition to this, the working platform for the LC-columns rigs was also stabilised. At this project, over 200,000m2 of TriAx geogrids was installed.
PROJECT DESCRIPTION
The Mechanically Stabilised Layer (MSL) consisted of 0-63 mm crushed rock with an average thickness of between 600 - 800mm. TriAx geogrid was placed directly on the sub-grade without a geotextile beneath and 400mm layer of crushed rock was placed on the grid and compacted. A second layer of TriAx was then installed and a further 200mm of stone placed and compacted.
For the working platforms, only a single layer of TriAx was required. The aggregate size of 0-63 mm was not selected to enable the LC column auger to penetrate through the platform.
The TensarTech TW1 system was also chosen as a solution because of its structural flexibility. Due to the dry laid construction of the facing, any anticipated post construction settlement could be accommodated without causing undesirable aesthetic facing issues.
