Having accurate ground investigation information (GI) is a good start. However, as the settlement analysis below shows, with detailed modelling techniques we can take preliminary substructure designs much further forward, in this case offering our client a significant cost saving over a deeper foundation solution.
In challenging economic times, adding value to commercial, residential and infrastructure development projects by economising design with high-quality technical, environmental and financial solutions can be critically important to the quantum of development, and thus key go/no go decision-making.
Many developers want to invest capital … and invest it well. The Government is equally anxious that they should too. Future returns can be significant. However, the balance of profitability versus risk has seldom been higher. Our aim with our clients is to reduce this uncertainty.
This is a speciality area where I am privileged to take the lead at Enzygo Geo-environmental Limited (www.enzygo.com).
Going ahead on a safe footing
Specifically, by taking and interrogating existing, often ‘preliminary’ ground investigation information, we can identify opportunities and risks. By applying a range of modelling technologies to analyse this data, and often obtaining more information to further quantify risk, we can save time, money, and unforeseen disruption[s].
What our work demonstrated on the residential proposals outlined below was that removing uncertainty allowed us to prove how using conventional spread footings would be a more environmentally friendly, lower-cost foundation option than a more intrusive piling programme.
Enhanced design and better results
With building, construction and many other sectors currently facing soaring inflation, high and rising interest rates, plus increasing material costs, I thought it would be useful to quickly sketch out how we added value through design in one case as an example of what we can achieve over a wide spectrum of similar projects.
In this case at Kidlington in Oxfordshire, we were commissioned to carry out a detailed settlement assessment for a proposed residential development that involved two separate four and five storey apartment blocks.
Enzygo Geo-Environmental Ltd (https://www.enzygo.com/geo-environmental/)
To put our involvement here into context, I should explain that as part of our specialist offering, we provide a full range of geotechnical and geo-environmental services throughout the UK.
Our multi-disciplinary team of chartered engineers, geologists and geo-environmental specialists pride themselves on firstly creating and then delivering highly tailored cost-effective solutions. The aim is to create and release maximum site value for all client schemes.
The geotechnical design we put forward – including the interpretation and determination of the ground model – was to current UK [British] Standards.
Immediate [Elastic] settlements of the underlying soils were modelled using the displacement software programme Oasys PDisp, Version 19.4 (2018). This calculates settlements and stresses within a layered linear elastic soil mass and is based on varying applied loaded areas and deformation moduli for each soil layer adopting a Boussinesq stress distribution consistent with Hooke’s law in a linear stress-strain relationship.
The analysis considered the serviceability limit state in accordance with BS EN 1997-1:2004+A1:2013, Eurocode 7: Geotechnical Design Part 1. Undrained and drained analyses were undertaken to calculate the anticipated immediate and total (elastic) settlement movements.
As a result of this very detailed modelling, we were able to derive anticipated settlements movements that enabled a more traditional spread footing option to be used vs a deep piled solution.
Further case studies
We have successfully both reduced and removed the need for extensive heave protection under large, piled basements on several development sites, which has added significant value to the quantum of development.
Several opportunities to change recommended foundation solutions to more traditional shallow spread and strip options have been successfully implemented on numerous residential schemes after reviewing factual ground investigation reports packaged as part of the land purchase.
If you would like more information, or want to discuss specific opportunities or geotechnical issues, please feel free to contact me directly.
David Frayne – Associate Director, Enzygo Geo-environmental Limited