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140 MPa Tip Resistance – A New Record?

Gouda Geo-Equipment BV

Maasvlakte 2 is the latest expansion project of the port of Rotterdam. With this new 2,000 hectare area in the sea, the port will be 20% larger.

One of our clients, Dutch soil investigation specialist Mos Grondmechanica, has been asked to carry out Cone Penetration Tests up to 58 m deep for the foundation of loading and unloading quays. This depth is not that shocking, but the base soils appeared to be heavily compacted and cemented sands. It proved to be impossible to reach that depth with the traditional 200 kN rigs. It is for this reason that Mos Grondmechanica turned to Gouda-Geo.

Gouda-Geo developed a basic 350 kN CPT penetrometer platform that could be ballasted with 4 nr. 10 T heavy ballast blocks to provide counterweight for the CPTu tests. For this specific project the pushing force even was increased to 380 kN. The CPTu tests themselves were carried out with the latest generation fully digital P15CFPTxy piezocone with real time temperature compensation. Instead of the industry standard 36 mm CPT tubes, tubes with an outer diameter of 44 mm were used for this project. These tubes are 2.2 times more resistant to buckling than the 36 mm tubes.

Since the top layers were man made (dredged up loose sands) it hardly provided lateral support. For this reason special “jumbo” casing was developed to prevent buckling of the string of CPT tubes.

All this effort did let to the desired result. The CPTu tests reached indeed the target depth of 58 meter and during the tests tip resistance values of 140 MPa were recorded. A new record? Maybe, but it proved that the P15CFPTxy piezocone is an extremely sturdy instrument.

We would like to compliment the CPT operators of Mos Grondmechanica for a job well done!