High density concrete aggregate
Worldwide, engineers are seeking new and sophisticated tunnelling and underground solutions. They do so to limit ground-borne noise and vibration and overcome hydrostatic pressure, in an environment where you have limited space. Similarly, sub-level structures are looking for solutions to withstand natural groundwater pressure. Therefore, many projects included our high density aggregate MagnaDense to solve this challenge.
Preventing vibration and noise from tunnels to surface
Crossrail, recently done in the UK, is a perfect example of where MagnaDense is the best fit in an area bound by many limitations. Because it is running beneath central London, the project encountered many constraints. Firstly, there is the challenge of the restricted volume of the tunnel, and secondly, the proximity of surrounding infrastructure, meaning space was limited.
Therefore, the solution was the construction of a High Density Floating Track Slab (FTS), utilising MagnaDense concrete. Due to the limited available construction space, the concrete, developed to include the heavy aggregate MagnaDense, was the most suitable option to prevent noise and vibration caused by the passing trains. Also, the project had to overcome many logistical challenges, primarily because the pumping site is within the city centre.
And finally, the Crossrail project saw the world’s first installation of a High Density Floating Track Slab. Additionally, it set a world record for pumping high density concrete. As a result, LKAB Minerals and partners got four nominations for the awards at the NCE Tunnelling Awards in 2017.
For more information about the project, or to hear about the technical details of this construction, you can listen to the Crossrail webinar we recorded.
Overcoming hydraulic pressure with heavy aggregate
The use of high density concrete in situations where there is a need to overcome hydrostatic pressure is not only limited to tunnelling projects. Therefore, you can also find this in more common constructions such as:
- sites with existing sewer networks,
- buildings with sub-level floors
- and underground parking garages.
In a second section of the Crossrail project, they required high dense concrete for the first stage concrete works. This was due to the location’s proximity to the River Thames. Again, due to tunnel bore restrictions, additional weight was required in the concrete to overcome hydrostatic pressure.
LKAB companies involved in tunnelling
Swedish-based LKAB Wassara, a company within the LKAB group, is also working in the tunnelling construction industry. Their unique water-powered drilling hammer proves over and over again to work very well within this segment.
Tunnelling presents drilling challenges such as:
- water-rich formations
- high back pressures
- requirements on the borehole (length, accuracy, etc.)
- environmental concerns in sensitive areas
Wassara drilling technology is the solution to these challenges and has been used successfully in many tunnelling applications over the years:
- Anchor drilling for immersed tunnels
- Cut-off walls
- Ground reinforcement
- Survey, grout and drainage holes
Another team-member of the LKAB group is LKAB Berg & Betong. This is the company that among other things, sprays concrete in the LKAB mine tunnels to keep them save. Both Wassara and LKAB Berg & Betong supply their products to external commercial projects as well.