Weathering the storm In 2009, Odd-Björn Kleven became director of tunnelling and special projects at underground construction-equipment manufacturer Normet International. He talks to George Demetri about developments at the firm and in technology.
Please outline your career to date I have had more than 25 years’ experience in the underground construction industry, both as a contractor and as a supplier of products and equipment.
To this add wide-ranging experience in supervision and troubleshooting on important international projects in numerous fields of underground construction: sprayed concrete; injection; grouting; anchoring; fire protection and concreting. I have helped to create and promote new technologies, and I have been among the leading individuals in the development of wet-mix sprayed concrete and the use of steel fibres. Since 1981, my managerial experience has included building up the subsidiaries of a Norwegian contracting company and the development of Degussa’s Underground Construction Group. As technical manager for sprayed concrete at BASF UGC International, I was responsible for all underground, sprayed-concrete construction activities worldwide, spanning the management of product development and the global implementation of new technologies suitable for the promotion of more effective undergroundconstruction processes. This typically focused on sprayed-concrete rock-support technology. I have also been a tutor on courses for accrediting examiners for the EFNARC Nozzleman certification scheme. In my current role, as Normet International’s director of tunnelling and special projects, I am responsible for tunnelling activities and building up Normet’s chemical business. This involves a partial secondment as COO of construction chemicals company TAM Group.
You were recently appointed director of tunnelling and special projects. What do you hope to bring to the role?
With more than 25 years’ experience in the underground industry, I hope to strengthen knowledge of the tunnelling process and the know-how of the already experienced team at Normet International Frontline. Furthermore, with Normet entering the chemical market, I hope my background in construction chemicals will enable us to build a profitable business and bring added value to both the Normet Group and our customers. With its equipment and LTC (lifetime care) offering, Normet has become successfully established as a major player in the underground construction-equipment sector, particularly in mining. I now want to strengthen this position in civil construction and complete our offering with the inclusion of construction chemicals. In addition, the target is to establish Normet as a major player in underground-construction chemicals. With the recent acquisition of 40% of the shares of TAM Group, we have created a solid base for a successful and rapid entry into the underground-construction market. Just as we have done with Normet equipment and LTC, we will drive Normet’s undergroundconstruction chemicals division to become known for quality products, process knowledge, excellent service, reliability, and for furthering new technology that brings added value to our customers and partners.
How has Normet fared in the global economic downturn?
Like everyone else in the tunnelling industry, Normet has been affected by the financial crisis. But, the drop from the heights of 2008 was not significant, and Normet got through 2009 without laying off a single employee at the factory. At the end of 2009, we had a couple of very good months in terms of incoming orders. The first part of 2010 has been good and, even with increased production capacity, the factory has kept busy.
What significant tunnel jobs do you have on the books at present?
I want to mention the HATS project in Hong Kong, where we have supplied significant quantities of equipment, but are, in addition, heavily involved in the supply of chemicals through our recent acquisition of 40% of construction chemicals supplier TAM Group. Normet and Tam ha ve entered into a partnership whereby TAM will distribute Normet equipment in the UK, Ireland and certain markets in Asia, such as Singapore, Hong Kong, Taiwan and ASEAN. Normet will be the distributor of TAM Chemicals for underground-construction works in other markets around the globe.
What are the recent advances in sprayed concrete technology that you feel are really making a difference to today’s tunnelling?
Recent years have not seen any real groundbreaking developments in sprayed-concrete technology and, in my opinion, since the introduction of alkali-free accelerators to the market, greater advances have been made on the equipment front than in concrete technology and chemicals. Greater focus has gone on application technology while there has been wider recognition of impact application and its effect on safety during tunnel construction, end quality and the long-term durability of sprayed-concrete linings. The introduction of the EFNARC nozzleman certification scheme at the end of last year was a great advance, which I feel sure will improve the quality and recognition of sprayed-concrete linings, and lead to further progress in the acceptance of sprayed concrete as a final lining. Even though there has not been any really significant advances in concrete technology and chemicals over the last few years, technology levels still vary hugely from one market to the other, and many markets have a long way to go to catch up and adopt the latest technology.
What have been the overall cost trends of sprayed concrete in the past 20 years – are costs going up or down, and why?
In terms of cost trends, it depends on how you look at it. The cost of concrete per cubic metre has been increasing over the past 20 years as technology, working safety and end quality have undergone major improvements. But, increased application rates and improved quality have created significant time savings, and reduced the overall cost of rock support and tunnel linings. These have proved to result in major reductions in total project time and total project costs.
What is a typical failure mode in a primary sprayed-concrete lining and how has new technology helped to avoid it?
Many things could be mentioned here, but I want to highlight the layering from pulsation of the concrete coming out of the nozzle during application; this creates layering of the sprayed-concrete lining and reduces loadbearing capacity, as well as affecting other quality aspects of the sprayed-concrete lining, such as long-term durability. This pulsation is a result of low workability of the concrete and/or the engineering of the sprayed-concrete pumps. Improvements in concrete technology allowing for a low water/cement ratio in combination with high workability, and concrete pumps especially engineered for sprayed-concrete applications have improved the situation.
What, in your opinion, is the best way to waterproof a tunnel – is it to apply a waterproof concrete that includes some sort of additive or is it better to incorporate a waterproofing membrane in the construction?
Because concrete carries the risk of cracking, there is no way to really waterproof a tunnel 100%, whether it is a sprayed-concrete lining, a cast-concrete lining or a segment lining. In my opinion, the best way to waterproof a tunnel is to implement a proper pre-injection procedure. With proper pre-injection, it is possible to reduce water ingress to a minimum. Typical results from large road and twin-track rail tunnels in Scandinavia reveal water ingress levels of less than 10 litres/min per 100m (often as low as two to three litres are achieved) with proper pre-injection. In terms of waterproofing membranes, new technology such as sprayable membranes has been introduced and shows good potential in comparison to traditional sheet membranes. If a leak of two to three litres per 100m is not acceptable, this can be solved with a sprayable waterproofing membrane or by post-injection. What can we look forward to in terms of developments in sprayed concrete in the immediate future, wheth er in terms of technology, time, costs, etc. There is a saying that to tell fortunes is not easy, especially about the future, so to predict what is to come in terms of new technology is hard. But, certainly, we, at Normet, will work hard to drive the technology forward in all areas of the tunnelling process, including concrete technology, chemicals, and equipment and application technology. Anyhow, I strongly believe that we will see a trend towards the use of sprayed concrete as a final lining, as well as towards single-shell linings and single-shell composite linings, including sprayable waterproofing membranes. This will reduce project times and total project costs compared to traditional lining concepts.
What are the most common on-site practical problems that a tunnel contractor must face when applying sprayed concrete?
The major reason for on-site practical problems is related to water-to-cement ratio and temperature. A high water-cement ratio, as well as low temperatures, will result in slow setting and slow strength development, as well as problems in building the required thickness and drop-outs. Another problem often seen is the short open time of the concrete, resulting in low workability. Furthermore, in tunnels and mines using equipment without on-board compressors, and where air is supplied from a centralised compressor, an often reoccurring problem is compaction and, consequently, the creation of a low-strength, porous concrete.
Has improved technology resulted in thinner and therefore lower-cost sprayed concrete?
Improvements in terms of concrete technology, chemicals and equipment, as well as application technology, have all improved the ability to apply a more even and controlled thickness. A more even thickness reduces the amount of overspraying in certain areas; a problem that had previously been common. At the same time, this, together with improvements in fibre technology, has improved the quality and load-bearing capacity of sprayed concrete. This has all had a positive effect on the overall cost of a sprayed-concrete lining.
www.world-tunnelling.com
For more information, please contact:
Odd-Bjørn Kleven
+47 90 688 577
odd-bjorn.kleven@normet.fi