Google HQ: Pressuremeter Testing Approach

Adjacent to Kings Cross Station and in the vibrant Coal Drops Yard, construction has been in full swing since 2018, and it is exciting to see the UK Google HQ come to life. But the design, ground preparation and ground investigations commenced long before this. 

The unique, 11-storey structure, with a triple-storey basement, designed by BIG and Heatherwick Studio comprises adaptable space, and required floors spanning the full width of the building, with internal multi-storey spaces.

The design included impressive triple-storey internal spaces, a column-free western elevation and a notable roof structure with trees. Accordingly, the loads were concentrated and significant.

Challenges With Conventional Foundation Solutions

The conventional foundation solution would use piles terminating within the Thanet Sand Formation. However, this would require piles in excess of 40m long which would be timely and costly.

An alternative approach to investigation techniques and analysis was required, to ultimately limit construction risks.

Pressuremeter Testing Approach

Working with structural engineers AKT II, along with the usual investigation data, the use of pressuremeter testing was advocated within the London Clay as it can provide high-quality data at small strain levels.

Despite the technique being around for decades it is used sparingly within the ground investigation industry. There is still a reliance on Standard Penetration Tests (SPTs) as they can provide multiple data points for a relatively low cost.

In contrast, the pressuremeter takes time and requires more borehole preparation, and there is a reluctance to place reliance on fewer data points for a seemingly higher cost.

Pressuremeter Testing Benefits

The results from the pressuremeter testing indicated that the London Clay was significantly stronger than when estimated through SPTs and laboratory testing.

Accordingly, the foundation design could be leaner, achieving real cost savings and a reduction in concrete with associated carbon savings.

We continue to collaborate with our supply chain to provide innovative solutions. But sometimes it is simply a case of retrieving higher-quality data.

Of course, there is a cost and time implication but the overall benefit speaks volumes. Sometimes less really is more.

Following the publication of the AGS Guide to the Selection of Pressuremeter Testing, Soiltechnics is proud to have provided guidance on the utilisation of various pressuremeter techniques as part of our site investigations around the UK.

Collaborating For Design Efficiency: Soiltechnics and Cambridge Insitu

Soiltechnics has worked closely with Cambridge Insitu over many years bringing design efficiency to many complex foundation challenges.  

Working collaboratively with Cambridge Insitu to enable cost-effective testing campaigns, allows Soiltechnics to provide expert advice regarding the specification, correct deployment and interpretation of the pressuremeter test results.

Together, we bring confidence to enable the use of cleaner and more sustainable design solutions.

The Importance of Experienced Investigation Teams

As discussed in the AGS guide, it is important that the investigation team are experienced in the deployment and operation of the various pressuremeters used by Cambridge Insitu.

This is why talking to Soiltechnics at an early stage will help the project design team achieve the best results from the tests.

How We Can Help

If you would like to tap into the extensive experience Soiltechnics can offer and discuss the use of pressuremeters on any project, along with the benefits it may bring, Angus Wilson or Stephen Cragg would love to hear from you.

Call +44(0) 1604 781877 to find out more.