|Location||35 St Georges Road, London|
|Requirement||Bearing piles for Five Storey Mixed Use Building|
|Techniques||Grouted , Micro pile|
|Main Contractor||LR Lima Construction Limited|
TechnikGS was awarded the contract for the design and installation of permanent bearing piles following the completion of a substructure value engineering exercise.
The site had an infilled basement and both access and working area was severely restricted.
The works included the installation of over 50 vertical bearing piles carrying working loads of up to 325kN.
- Sensitivity of adjacent residential structures to noise and vibration.
- Restricted site with tight access requiring careful planning with regard to material storage, site deliveries and spoil management.
- Potential for obstructions in the ground.
- Tight programme and budget constraints.
The grouted micropile was the ideal solution on the site due to the presence of medium dense and dense granular material. It alleviated the need to penetrate the underlying London clay formation, which would have required a substantially deeper pile.
The drilling and continuous grouting process provides an effective pile diameter well in excess of the bit diameter. On this project a 200mm diameter drill bit was used and as a result the pile diameters measured greater than 300mm on excavation of the basement.
The geotechnical capacity is also enhanced due to the drilling and grouting injection process which provides a much greater grout-‐soil bond compared to more traditional piling methods.
The continuously grouted pile, which relies on the grouted annulus to maintain bore stability, was progressed to the design depth before the drilling system was fully withdrawn leaving the pile reinforcement in place. Installation of up to eight piles per shift was achieved.
A static load test was carried out on a working pile and the recorded settlement at working load was less than 3mm.
Conventional mini-‐piling techniques using casing and augers would have required a larger diameter and deeper depth, generating significantly more spoil which would have been time consuming and expensive to deal with in Central London.