Our will to win solves London basement conundrum
22nd December 2020
Geotechnical
Our Client
Preliminary-Assessment
A basement was proposed to 4.25m below the ground level. The site was located on dense granular soils associated with the Kempton Park Gravel Member. The ground was so dense that the rig used was unable to drill to the proposed basement level. Given the experience, knowledge and resources Ground & Water has in the Belgravia area, the geological conditions (density/strength of soils and the top of the London Clay Formation) and hydrogeological conditions (groundwater level) could be inferred. This could lead to accurate and acceptable settlement/heave analysis of the basement.
Our Challenge
Not only do these projects require high level analysis of settlement, heave and movement of surrounding ground, they must comply with the guidance for basements documented by the Borough of Westminster. A way of overcoming ground access difficulties and complex ground movement issues had to be found.
The Ground & Water Approach
As part of the report, a suitable assessment of the damage to surrounding walls from ground movement was required. This was undertaken and multiple walls were noted to have slight damage. A discussion within the Ground & Water engineering team followed to assess the limitations in the software and the model. Conclusions included: all walls could be modelled at ground level, rather than the formation level of the foundations/basements; the interactions between multiple walls acting structurally as one and the changing the height of the walls. Further modelling was then carried out to try to reduce the damage category. This reflected the engineering team’s innovative thinking and determination to help solve the complex issues, it was faced with.
The Outcome