Dublin: Merrion Square Secant Wall

DAWSON-WAM Ltd was contracted by Stewart Construction to construct a new secant wall to facilitate the construction of the new basement and extension of the German Embassy Building. 

The site was extremely restricted for working space with the site only 30m by 9m which presented many challenges organising the delivery of rebar and concrete to site and spoil arisings off site whilst all the time working with other subcontractors on site. With careful planning DAWSON-WAM were able to successfully complete the secant wall within the client’s required program period. To maximize the basement footprint the secant piles were installed to within 100mm of existing 4 storey facades. 

With the limited space available on site it was critical to maximum the basement footprint where possible. DAWSON WAM’s Cased CFA system was employed to prevent flighting and also ensure piles did not encroach into the basement footprint where tolerances of over 1:150 were achieved. 

DAWSON WAM provided a heavily reinforced 420mm diameter hard / hard secant piled wall so that the 6m deep basement only required temporary props at capping beam level to mitigate deflections. This was extremely beneficial for the constructability of the basement for the follow on trades such as bulk excavation and the construction of the basement walls and floor slabs.

Noise and vibration levels were continuously monitored throughout the course of the works together with deflections in the secant wall as the bulk excavation progressed.