Movement Joint & Water Ingress Investigation, M20 Bridge, Swanley
Project overview
Spectra were appointed to investigate water ingress into the main structure of a bridge carrying the principal route into Swanley over the M20, close to the M20 and M25 interchange. The project sponsor had commissioned a technical note to inform decisions on the structure, and Spectra delivered the full investigation programme, visual, non-intrusive and intrusive, under night time road closure.
Approach and delivery
The investigation combined three types of survey in a single programme. Visual assessment covered the bridge surfacing, the footways and the movement joint locations, together with geometry verification, while drainage surveys established whether surface water was pooling and whether the gullies were working.
A ground penetrating radar survey determined surfacing depth, reinforcement and whether water was trapped within the structure, with the services element carried out in accordance with PAS 128. Eight core samples were taken, principally at the movement joint locations, to verify whether a waterproofing membrane was present and to establish the road pavement construction, with tar and asbestos testing carried out at a UKAS accredited laboratory. Intrusive services investigation established the depth, type and location of services within the footway, and all intrusive investigations were permanently reinstated.
The whole programme was delivered under night time road closure on a live trunk road, which governs how much can be opened up, tested and made good again before the road has to reopen.
Outcome
The investigation found extensive micro cracking across the road surface, failed movement joints, and waterproofing absent at the majority of the intrusive investigation locations. The gullies were working as intended but silted by around 30 per cent. Tar and asbestos testing returned negative. The findings indicate the structure will require a new waterproofing membrane and full resurfacing, and the technical note has been issued to the project sponsor to inform that decision.
Related projects
Same disciplines, different settings. A sense of how we run this kind of work elsewhere.
Talk to Us About Your Project
If this looks like the work in front of you, tell us the site and the constraints and we will tell you how we would run it.
Contact Spectra today for trusted expertise in asbestos, demolition, fire protection, and environmental safety.
Prefer to speak to someone now? Call 01268 534380.
