Presidentveita i Trondheim JETGRUNN

Basic conditions

The terrain on the plot is at elevation 12.0 – 12.5. In the upper part is

the 0.5 – 1.0 m filled sand and gravel. Under the layer with met

sand and gravel is a cultural layer down to elevation 8.9 – 10.1. Furthermore

in depth there is sand and gravel to a great depth. It is expected

transition to silt and clay with depth. The mountain lies deep,

perhaps over 100 m below ground. It is assumed that the groundwater

located at approx. elevation 3.0.

Solution

The culture team that is protected gave guidance for

the foundation solutions. A building located on terrain,

without relief, would probably get big sentences.

The original proposal was to base the building on floating foundations

piles (friction piles). Framing of concrete piles through

the culture team would, however, cause damage to the culture team.

The National Archives’ wish was to limit the damage to

cultural layer to a minimum.

In this connection, the possibility of using jet piles was looked at

in combination with casing through the culture layer. This

the solution was chosen and limited the number of piles in relation to

the option of concrete piles, as the capacity of each jet pile is

larger than a concrete pile. By using jet piles, the number

piles reduced from 49 to 37 pcs.

Reinforcing cages were threaded through the casing and down into it

the jetpack after production. After the jet pile was hardened became

the casing cast with structural concrete.

The project was completed without any problems or obstacles.

All piles were set in 8 days. Sentence measurements on

adjacent buildings and on the soil surface/cultural layer exceeded

never the measurement accuracy of 2 mm. Measurements were taken before,

during and after production.