bridge piers and structures

concrete mattress protection against accelerated flows.Using Concrete Mattress
Concrete mattress is an effective protection against accelerated flows at bridge piers and other structures, Locally accelerated flows during storm or other peak exposure conditions can cause undermining to structures. Due to its low construction depth, concrete mattress can be installed without significant excavation which may otherwise may threaten undermining of the foundations. For existing structures, foundation formation levels can be surveyed and any underscour holes infilled as shown in Foundation Underscour Repairs

Mattress thicknesses are usually determined by a reference to proven performance and relevant design guides. CFD modelling has been utilised where accelerated flows are significant to larger structures, above 2-3 m/s.

mattress thicknessThe scour apron is usually extended upstream and downstream to areas of lower scour potential for the formation of important toe edge details. The edge embedment protection should be greater than the scour potential at that point. (See edge details B103)The mattress system is additionally effective in remote locations and for working under bridge structures.

Procedure

Diver Survey - Survey bed & voids after removing any soft deposits, typically recording scour area & any infill void height, depths and lengths.
Form Design - Design & fabricate mattress protection & manufacture underpin forms with typically 10% surplus to ensure good void infill.
Mix Preparation - Prepare fluid and pumpable micro concrete as outlined on B65 and B66.
Position Forms - Divers roll out mattress into place.
Pump Infill - Pump fill mattress with micro concrete.
bridge scour protection specifics

mattress thicknessAdvantages

- low thickness
- low invert levels possible
- less effect of flooding levels
- protection to shallow foundations
- high performance and durability

Published Papers


“Bridge Scour Protection”, ICSE Scour and Erosion Conference, UK (2016)

Past Projects

Cogrie Viaduct (B129)



General

Bridge Scour Protection (B130)