The Swarm, Thorpe Park, Surrey

THORPE PARK’S new adrenaline-inducing theme park ride, THE SWARM, is the UK’s first winged rollercoaster and sets a benchmark in ride experience.  As the nation’s Thrill Capital, THORPE PARK, owned by Merlin Entertainments, the leading name in location-based, family entertainment and Europe’s number one visitor attraction operator, is constantly pushing the boundaries with its new attractions and THE SWARM will not disappoint.  This extreme ride offers as many as five terrifying inversions and a unique 127 ft head-first inverted drop.

The dynamic load of 28-rider trains travelling at up to 100km per hour, on 1000 tonnes of track over a distance of 775m (2,543 ft), is supported with Saint-Gobain Weber’s high performance precision grouts.  Working with UK structural designer HBL Associates of Stockport, Cheshire, for Swiss-based ride manufacturer Bolliger & Mabillard, Saint-Gobain Weber, provided the extensive calculations and technical justification to support their product recommendation and meet the exceptional rider-safety demands and capacity of THE SWARM.

This enormous structure and the ground bearings would clearly be subjected to very high dynamic loadings generated by the fast and furious winged ride-cars.  HBL called in the expertise of Saint-Gobain Weber to specify the special grouting materials that would fix the steel mountings to the concrete ground bearings and be capable of absorbing these high loads. Selecting a material for fixing the plinth anchorages and the shear key anchorages had two main criteria; it had to have the ability to sustain high dynamic loadings and to transfer the stress from the structural steel components back into the concrete bases.

Saint-Gobain Weber has decades of experience with giant motorway structures, bridges and viaducts where structures are carried on bearings fixed to  structures and the company’s webercem five star repair concrete has been the standard for many Highways Agency specifications for this type of installation and complies fully with BS EN 1504. Tests have also confirmed that the shear bond resistance of webercem five star repair concrete is greater than 7.5MPa.

webercem five star repair concrete, is a permanent structural repair microconcrete, which provides both dynamic resistance properties and flexural strength. It has a minimum cement content of 400kg/m³, maximum aggregate size of 10mm, whilst maintaining a good flow rate and produces a minimum compressive strength of 60N/mm² at 28days after pouring at 200C.

The specialist applicators working for TG Cruse, the principal contractor, did a superb job in pouring and finishing the concrete to a very high standard.

The designers of THE SWARM had an additional challenge in that there were two anchorage locations on the structure where the ride cars generate 5G loading on sharp bends. Again Saint-Gobain Weber provided the technical solution with the specification of webertec EP pourable grout, an epoxy resin based precision grout fully capable of meeting the dynamic stress loads and stress transfer requirements.  It achieves exceptional toughness and chemical resistance, has good flow characteristics and there is negligible shrinkage.  This product cures within the temperature range of 5 degrees to 35 degrees Celsius and so was suitable for pouring by contractor T G Cruse Construction Ltd of Salisbury, Wiltshire, during the mild Christmas 2011 break. 

Due to the significant volume needed to fill and fix the anchor points, Saint-Gobain Weber recommended the inclusion of kiln-dry aggregate to bulk out the grout and to reduce the expected exotherm where heat generated in the curing process of the high volume would have reached over 100 degrees Celsius with a risk to the integrity of the grout. The inclusion of the aggregate material also reduced the volume of resin required and prevented excessive expansion and possible shrinkage.