A geo-technical survey was completed to determine how deep the foundations of a new bridge over Norway’s biggest lake, Mjøsa, should be. The scope of the project was a survey along two lines across the lake by undisturbed sampling, sonic sampling and – parallel to the sampling – a complete CPTu test from a barge. This project was carried out with Royal Eijkelkamp sonic drilling equipment.
Why sonic drilling is used.
Moritz Aydt, project manager at BTR Bohrtechnik Roßwag, explains why BTR used the Royal Eijkelkamp sonic drilling equipment for this project. To be able to engineer the bridge foundation, their client needed some soil data. They accomplished that with sonic sampling and CPTu. They did the CPTu testing to extreme depths.
First, they went down through 80 meters of water and continued CPTu from the lake bed till they reached an overall depth of 140 meters. The cone penetration or cone penetrometer test (CPT) is a method used to determine the geotechnical engineering properties. The parameters measured are tip resistance, sleeve friction, pore pressure, inclination and penetration speed. This data shows their client the condition of the soil and how deep the foundations of the bridge should be.
Nice core samples and an unbeatable production speed.
Their company chose sonic drilling because it’s perfect for soft rock formations, silts and gravels. They come from an area where they mostly do rock drilling. But occasionally they must go through overburden or do sampling in landfills and softer formations. This is where sonic is perfect because it gets you nice core samples at an unbeatable production speed. This makes sonic very efficient and fast. TDI would definitely recommend sonic because of all its advantages. Its production speed allows them to be much more competitive. With the dual head sonic rig – that is, sonic plus high speed rotary – they can apply their sonic rig for multi purposes.
About the Moelv-Roterud project.
The Moelv–Roterud project, which includes a new 9-km bridge across the Mjøsa lake, is one of three EPC contracts on the Moelv–Øyer stretch, which is a 44-km four-lane highway project run by Nye Veier AS. The existing bridge is not dimensioned for the future traffic. Therefore, Nye Veier AS started this project to investigate the possibilities for a new bridge.
The project includes the 4-lane highway across the bridge, the bridge itself, and 2 interchanges and 8 smaller structures over a distance of 1.6 km. This project is technically unique because of the depth of the lake (80–90 metres), the depth to solid rock (deeper than 80 metres) and the conditions of the soil.
Royal Eijkelkamp’s companies produce and supply products and services for soil and water research. In this way they contribute to a more durable use of our earth.