![\"York](\"https:\/\/www.europesays.com\/uk\/wp-content\/uploads\/2025\/05\/York-Road-map.webp.webp\")
<\/a>Current works<\/strong><\/p>\nThe second phase of the York Road river wall repairs will initially focus on the Banana Bridge site, where two sections of stone retaining wall either side of the bridge abutment have been gradually pushed out into the river and effectively failed.<\/p>\n
The team started work at Banana Bridge first, because the tiltmeter monitoring equipment installed at the site measured continued movement.<\/p>\n
A project team representative told GE that the ground conditions at Banana Bridge comprise superficial soils of made ground and soft alluvial clays and silts, overlying mudstone, beneath which lies Redcliffe Sandstone.<\/p>\n
Banana Bridge strata<\/p>\n The provisional design option for the Banana Bridge project involved installing piles at the carriageway.<\/p>\n \u201cThe initial sketch showed anchored bored piles, but due to the proximity of sensitive services and considerations of stability under plant loading, a vibration-free pushed sheet piling system was implemented,\u201d the spokesperson said.<\/p>\n \u201cThe anchors were eventually replaced with buttressing sheet piles, providing greater design certainty and avoiding clashes with local services.\u201d<\/p>\n The overall design is still being finalised, but the project team expects to replace the Odex bored piles behind the existing wall with push driven sheet piles.<\/p>\n \u201cRegardless, the two sets of piles are tied together using a reinforced concrete (RC) ground slab and a skeletal revetment slope including scour protection using Geobrugg products, all of which offer a 120-year design life. The interim area is stabilised using screw piles to enable plant access,\u201d the spokesperson added.<\/p>\n \u201cFor future projects, the observed issues strongly suggest that a similar approach will be undertaken in areas of the New Cut of similar instability and geological characteristics.\u201d<\/p>\n In contrast to the Banana Bridge site, where soft and loose superficial soils feature behind the failing river wall, the channel sides of the Avon New Cut further west at the Cumberland Road site and beyond are primarily composed of sandstone, both bedded and massive, resting on mudstone.<\/p>\n \u201cThe main challenge is the extreme tidal conditions, with a range of up to 7m between high tide and low water riverbed level, coupled with high storm and tidal flow rates that carry small to moderate-sized scree. This results in mechanical and hydraulic erosion of the channel sides, particularly at the lower levels,\u201d the spokesperson explained.<\/p>\n \u201cThe masonry walls are founded on the lower-level mudstone, which was notched to create a foundation platform. However, the mudstone, being a weaker argillaceous stratum, erodes more quickly than the overlying sandstone. This leads to the loss of the wall foundation bed and undercutting of the upper sandstone strata.<\/p>\n \u201cFrom a design perspective, it is evident that while the mudstone has remained intact globally since 1809, it is no longer suitable as a near surface foundation stratum from a continued serviceability point of view.\u201d<\/p>\n<\/a><\/p>\n