A tunnel that bored 40m under the sea floor, for a distance of 38 km, would undoubtedly present an epic challenge. Back in 1988, the Channel Tunnel project was to become the starting point for Bennett Associates’ journey into the world of tunnelling. This year sees the 20th anniversary of their involvement in the tunnelling industry.

Over the last two decades, M G Bennett & Associates Ltd has been involved with some of the world’s largest tunnelling projects including the Channel Tunnel, the Channel Tunnel Rail Link, the Tai Lam Tunnel in Hong Kong, the Storebaelt Tunnel in Denmark and a tunnel for the Heathrow Express. More recently, Bennett Associates has worked on major tunnelling projects in Asia.

The Channel Tunnel became a defining moment in Bennett Associates’ presence in the industry. The company designed the 235m long back-up system to the tunnel boring machines on what would be the world’s largest undersea tunnelling project. Bennett Associates was also contracted to carry out a full stress analysis of the cutter head support, TBM structure and gripper body and pads, which was done by Finite Element Analysis using ANSYS software solid modeling elements.

In 1991, construction began on the Storebaelt Rail Tunnel, which would provide a high speed rail link between Europe and Scandinavia. Bennett Associates were involved in a design audit using Finite Element Analysis of the major structural components of the four Tunnel Boring Machines that were used to bore the twin 7.5km tunnels. Dr Chris Bird, Technical Director of Bennett Associates, was seconded to the project on a full time basis for three years overseeing tunnel safety and providing additional technical advice. In the latter part of the project, additional responsibility was taken on for the technical management of the TBMs, both in the operational and dismantling phase of the project.

Following the success of their work on the Channel Tunnel, Bennett Associates subsequently went on to design the back-up system for the 7.5km Channel Tunnel Rail Link between Stratford and St Pancreas. This crucial part of the project provided the final link between the Channel Tunnel and London.

Bennett Associates’ expertise in tunnelling infrastructure, including segment handling equipment, shaft and tunnel systems and material handling, has been called upon for many projects throughout the last two decades. Their design of two 26 metre sliding crossover doors for the Tai Lam tunnel train track in Kowloon, Hong Kong, included the mechanism to close the 45 tonne doors to provide a 4 hour fire barrier. They were also involved in a noise pollution project involving the design of an acoustic shroud during the construction of the Jubilee Line extension, as well as the design of a submerged shaft excavator that was used during the Fylde Coastal Water Improvement Scheme.

In recent years, there has been an increasing interest in the cost and time advantages offered by the redesign and conversion of existing equipment. In addition to providing bespoke new build equipment, Bennett Associates' technical expertise has allowed them to develop cost effective solutions for this equipment including cutter heads and backup systems.

Evolving steadily over the last two decades, the company has built a worldwide reputation as an authority in tunnelling and is able to offer litigation and arbitration services to clients and contractors. Based in Rotherham, the firm has grown from three founding employees to a current staff of nearly 30. In addition to their tunnelling expertise, Bennett Associates are involved in a broad spectrum of engineering fields including movable structures, aerospace, nuclear, materials handling and sub sea oil production.

“Our ability to meet the challenges that our clients face is the cornerstone of our business. Ourexperience means that we can understand specific problems and adapt throughout the design process. As a result, we are able to deliver solutions that are within budget, and that ensure projects remain on schedule”, said Nick Cooper, Managing Director of Bennett Associates. “This milestone is a tribute to everyone at Bennett Associates who has worked so hard to make the business a success.”