A Novel Approach to Bracing a Piled Retaining Wall using Temporary Piled Buttresses-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes a temporary piled-buttress system used to brace a contiguous bored-pile retaining wall at a commercial arena project in Manchester, an area with a history of coal mining. The piling scope included 200 metres of retaining wall, 1,300 bearing piles, and grouting to stabilise historic coal workings.<br /><br />Traditional temporary works options—earth berms, props and raking shores—were considered impractical because they would take up space, restrict access or require additional foundations. Instead, temporary rotary-bored buttress piles were installed to support the wall during excavation. The sequence was to construct the wall and buttresses, excavate to formation, build the basement slab and then the ground-floor slab and permanent concrete abutments, before removing the temporary buttresses.<br /><br />The wall design was developed iteratively using WALLAP. Buttress piles were modelled in PLAXIS 2D using the Hardening Soil model, which accounts for stiffness changes with stress level. Modelled forces informed conventional pile design. Because services beneath an adjacent dual carriageway were sensitive to movement, wall deflection was limited to 25 mm.<br /><br />Predicted deflections ranged from 14 to 30 mm, while measured deflections were only 6 to 12 mm—below the specified limit and lower than predicted. The presentation concludes that temporary piled buttresses can provide an efficient alternative to conventional propping. It also identifies opportunities to improve future designs through more site-specific soil testing and more sophisticated monitoring, enabling better back-analysis and design efficiencies.

Keywords

temporary piled-buttress

retaining wall

bored piles

Manchester

coal mining

grouting

PLAXIS 2D

WALLAP

wall deflection

commercial arena project