Ramboll - Underpinning project

Hi Micropilers,

We want to share an exciting experience with you!  On the 14th of October we went to visit the Ramboll office in Turku and a building site to see how micropiling is done in Turku.

Ramboll is a leading engineering, design and consultancy company and is active in the markets: Buildings, Transport, Environment, Energy, Oil & Gas and Management Consulting. It was founded in 1945 as the "Rambøll & Hannemann" partnership in Copenhagen, Denmark. Since then, Ramboll has expanded in to an international corporation employing 11,000 dedicated specialists in 21 countries. At the moment only in Finland 1900 people work for Ramboll in 26 different locations.  

Geotechnics is one of its main discipline with projects of all sizes and management of every phase – from planning, initial investigation, design and tender, too implementation, inspection and supervision. 

In the last years Ramboll-Finland has been appointed as the structural and geotechnical engineer for:

- harbors, for example in Helsinki;

- 51,3 km of the E18 motorway, which goes from the Southern of the country till the border of Russia;

- the new children’s hospital, Uusi Lastensairaala, in Helsinki;

- many others.

 Reino Heikinheimo has kindly shared his experience about micropiling with us.

In the 1900’s wooden piles were used for the foundations of the houses in Turku, these are still in the ground and are still working. Today the main problems are that the piles are rotting in old houses due to the fluctuation of the water level or they are settling into the ground because they were built in a thick layer of clay (for example the clay layer is 40-50 m deep in Turku).   

The underpinning technique provides the installation of additional piles which can bear the load of the building.  The most important issues to consider are:

- the costs

- the dimension of the machine, because the spaces for working are often very narrow

- the noise and the vibration for the neighbors

- the possibility of corrosion for the steel piles.

 

The building site is situated in the city center of Turku, not far from the market square, along the banks of the River Aura. It's a residential building of 7 floors, with many apartements.

The old foundation consists of friction piles, installed in the clay soil, which covers most of Finland. This type of soil causes big structural problems to the foundations, which over time sink into the ground.

For avoiding these type of problems, a new foundation is settled, without modifing the existing structure. 

 

This system is so called Underpinning.

  


 

The work consists of drilling in to the ground until the bedrock and embedding 87 new steel piles, much deeper than the oldest ones.

The positive aspect is that all the work is done in the basement, leaving the outer structure in function. The residents don't have to move while the work is done!

Drilling
 machine

Steel pile

 

 The hole for the new piles is made with an electronical or pneumatic drilling machine, as it is shown in the picture on the left.

Pile being drilled

Steel pile with concrete

An operator is using the drilling machine and the steel pile is being fixed in the ground in separated parts, which are welded together.

When the pile is fixed, concrete is put inside. The piles used in this project are

Ø140.

The load transfer structure is realised which connects the piles with the existing structure of the building.

The entire structure is first pre-stressed to minimize settlement and aftherwards stressed, for taking the load.

The new piles in the basement. Working and bearing the load.

This system does not change the existing spaces and so it'is a non-invasive system.