New Cementless TBM Backfill Grout
May 27, 2019
Together with PORR Bau GmbH, MC has developed a new TBM backfill grout based on a geopolymer that is suitable for use in swelling rock formations. This cementless annular gap filler prevents swelling pressures, is sulphate-resistant and provides a permanent bedding for securing the tunnel tube.
In order to enable transmission of the drilling forces and reduce surface subsidence, this annular gap has to be completely filled with grouting materials in a process generally referred to as backfilling, with the materials used falling into one of two categories – singlecomponent (1C) and two-component (2C) grouts.
The 1C grouts contain cement, additives, aggregates and water. Concrete admixtures are used to create specific application properties. 2C backfill grouts consist of cement, bentonite and water.
Here stabilisers are used to provide for the necessary application properties while ensuring a working time of 48 to 72 hours. 2C grouts are suspensions made up with large amounts of surplus water, allowing them to be pumped over distances of several kilometres. They are thus comparatively easy to use. In Asia, 2C backfill grouts have been in use for many years.
They were applied for the first time in Germany for the Emscher Project. And here too, MCBauchemie worked closely with PORR Bau as a key player in developing the required formulation. MC supplied all the necessary additives and provided the application engineering support.
Limits of conventional TBM backfill systems
Both methods – 1C and 2C – have their advantages, but cannot be used for boring swellable rock, e.g. that containing anhydrite, because both are cement-based and release excess water to the surrounding substrate. If anhydrite comes into contact with water, gypsum is produced as the reaction product. This reaction is accompanied by a volume increase of around 60 per cent.
The associated swelling pressures are so enormous that elevations at the earth’s surface can occur and underground structures can be permanently damaged or even destroyed. When working in strata containing anhydrite, therefore, it is essential to prevent the release of surplus water from the grout to the surrounding rock. This is not possible with cement-bound materials.
A backfill grout suitable for anhydrite rock
The binder of the new backfill grout consists of granulated blast furnace slag and fly ash. Aggregates are used to stabilise the mix. An activator is added to the supply device via which the backfill grout is introduced into the annular space. This triggers the binder reaction.
The grout also contains a variety of phosphates that suppress anhydrite swelling. The concrete-like properties of this TBM backfill grout enable production in a ready-mix concrete plant located at the construction site.
The long processing time of the material gives tunnel builders more flexibility, as without addition of the activator the grout can be stored for long periods without deterioration. This novel grout material is currently being successfully used in the anhydritebearing unleached gypsum keuper of the “Stuttgart 21” project.
MC-Bauchemie Müller GmbH & Co. KG is a leading international manufacturer of building chemical products and technologies. Headquartered in Bottrop, Germany, the group of companies with over 2,500 employees operating in more than 40 countries around the world has – in the 50-plus years of its existence – consistently made a name for itself through the development of advanced solutions for the treatment of concrete and the protection and maintenance of buildings and structures.
More News and Articles
Dec 06, 2023
The UK’s largest water and wastewater company, Thames Water, has selected Ovarro’s end-to-end service LeakNavigator to deliver a three-year leakage reduction contract, writes Tony Gwynne, global leakage solutions director at Ovarro.
Dec 04, 2023
In an effort to combat water loss, a global collaboration involving organizations from the UK, US, and Mexico is launching a long-term project in Querétaro, Mexico. Utilizing actionable AI, the initiative aims to manage and conserve water resources across 350km …
Dec 01, 2023
A microtunnel boring machine (TBM) has arrived on Elizabeth Street to help deliver one of the biggest upgrades to Melbourne CBD’s sewer network in more than a century.
Nov 29, 2023
Researchers at MIT (Massachusetts Institute of Technology) have made a groundbreaking discovery that could change our understanding of evaporation, a ubiquitous process in our environment. They found that under certain conditions, light can directly cause evaporation without the need for …
Nov 27, 2023
NEW UNITRACC Construction Site Documentation: "Rehabilitation of a DN 400 Concrete Gravity Sewer with a SAERTEX-LINER® MULTI over a Length of 69 m" (CIPP)
New construction site documentation in the renovation section of the e-learning platform: Rehabilitation of a DN 400 concrete gravity sewer with CIPP lining using SAERTEX-LINER® MULTI, type S+ Standard. The objective of this rehabilitation measure was to enhance the structural …
Nov 27, 2023
Digitising water management
Nov 24, 2023
Budleigh Salterton is a popular and picturesque seaside town situated within the East Devon Area of Outstanding Natural Beauty. Located at the start of the stunning Jurassic Coast; a UNESCO World Heritage Site recognised for its outstanding rocks, fossils and …
Nov 22, 2023
Having been in business for 86 years, Interflow has proven it knows a thing or two about longevity. Right now, that requires an all-encompassing sustainability strategy, as Richard McCarthy, Interflow’s executive general manager southern region, explained.
Nov 20, 2023
An interview with Managing Director Robert Ristow
Nov 17, 2023
Tractebel and Aurecon forge strategic partnership to revolutionize dam projects in Queensland, Australia
Tractebel and Aurecon form a strategic alliance to revolutionize dam projects in Queensland, Australia, combining their global expertise and local knowledge to meet the rising demand for dam upgrades.
Nov 15, 2023
SA Water will use horizontal directional drilling (HDD) to assist in installing a section of pipe underneath the Melbourne to Adelaide rail corridor.
Nov 13, 2023
Saudi Arabia’s visionary city, Neom, is leading the way in sustainable water solutions with the construction of a desalination plant powered entirely by renewable energy.