In Delft a co-operative association of commercial and public organisations known as the Delft Cluster pools knowledge on a variety of geotechnical and hydraulic subjects, including many aspects of tunnelling work. The organisations work chiefly on geotechnical and associated technologies and are based on and around the campus of the Technical University of Delft.
Sometimes termed a ‘virtual organisation’, the Delft Cluster has as the basis of its work in the particular need of the Netherlands for scientific intelligence on development and maintenance of sustainable delta areas. As well as the nation’s own ‘mature’ needs, there is a clear international need for such work since it is anticipated that 80% of the world’s population in urban areas will live in coastal areas and deltas by 2050. Given the population densities and resultant criss-crossing of infrastructure routes, underground development will play a significant part in the development of such regions.
The ‘Cluster’ was officially formed in May 1999 and the main participants are:
Finance
Funding for the Delft Cluster Foundation comes from commercial customers (30% or DFl30M – $12.2M), its partners (28%) and the government (42%), according the first four-year programme. It contributes to the Netherlands’ ‘Impulse Programme Knowledge Infrastructure’ from ICES/KIS (the Interdepartmental Committee for Economic Structure Strengthening, Knowledge Infrastructure). It submitted a research programme to ICES/KIS for the period 1999-2010, with funding for the first four years being approved in January 1999, accelerating its establishment.
The programmes of the Delft Cluster are more than a loose association since a combined schedule of research has been defined, and the combined concept has been marketed to target customers. This not only aids the establishment of an economic basis for research and development, but also gives effective interaction between theory and practice. A key is the management of knowledge both internally and with other institutes and market participants.
Long-term knowledge development by the Cluster is directed into three areas:
The first of these includes acquisition and development of technology for underground construction.
Within the programme for the first four years there are seven themes of which that on ‘Soil and Structure’ has the most significant content on underground construction. The Netherlands has long established, stringent requirements for the functionality and sustainability of infrastructure and water retaining structures. One example is the depth of passage of tunnels and bored utility lines under waterways, not only to provide sufficient cover to the greatest depth on any dredging programme, but also avoid the base of piles which sustain the banks of the waterway or drain, or which form the main structure of dykes. A particular concern is the soft clay and peat ground of the Randstad area. The HSL Zuid high-speed rail route is being directed through the Randstad where environmental concerns have resulted in the Groene Hart tunnel project (T&TI News February ’01).
Three sub-themes in the Soil and Structure programme, including one on underground infrastructure, have both generic and specific components. Generic parts are :
Specific parts are:
The sub-theme on underground infrastructure includes a wide variety of structures such as cellars, construction pits, foundations, junctions, and underground space as well as bored tunnels and the interaction with the surroundings including existing buildings. The last item now forms a specific Delft Cluster research programme (No.4) titled ‘The effects of underground building activities to surroundings’. This includes some GeoDelft work on TBM face stability and the effects of excavation rates on soft ground stability.
Japan links
Soil and structure is a particular focus for international co-operation by the Cluster, especially with Japan. This draws on Japanese expertise in implementation and technology development, mainly for the requirements of the large urban areas. In exchange the Netherlands has been a long-term partner in discussions about model formation and forecasting models. Cluster participants GeoDelft and TNO have active co-operation agreements with the Osaka GeoResearch Institute and various Japanese contractors such as Shimuzu Corporation. There are also string links between the Centre for Underground Research (COB) and the Japanese Tunnelling Association. The strong relationship between the Delft Cluster and the COB has resulted in an examination of research needs. Consequently there is now a distinction between short-term, project-led research run by the COB and long-term, fundamental research run by the Delft Cluster.
Knowledge management is a strong theme throughout Delft Cluster’s programmes, and accounts for 40% of its budget. The main aim is to have a systematic, efficient approach to information gathering, distribution and utilisation. This needs to be productive, and adaptable to demonstrate competency within the context of frequently erratic social change. Information held in various media has to be made readily available. For this purpose great use is to be made of information and communication technologies (ICT) to work with creative and innovative human capacity. An international ICT may be included in the project in order to share experience of implementing management systems and drawing on practices from outside the civil and hydraulic engineering sector. Both individual and organisational learning is being promoted in an atmosphere of knowledge sharing throughout Delft Cluster projects. A principal challenge is identified as the utilisation of hidden knowledge such as people’s experience, ideas and opinions.
GeoDelft
Despite its location on the campus of Delft University, GeoDelft is not part of the university, although it co-operates closely with it on many projects. Perhaps better known by its pre-1999 name of Delft Geotechnics, GeoDelft acquired its new image to reflect increased international co-operation and an accumulation of expertise and projects in other disciplines such as risk and cost management in general construction and environmental matters such as nature conservancy and pollution control. GeoDelft was founded in 1934 as a government department but has since been privatised into a commercial foundation with a turnover in excess of DFl44M ($17.9M) and 300 employees. It has permanent offices in England and Northern Ireland (chiefly engaged in environmental projects) but is active in many other countries.
As with other organisations in the Delft Cluster, GeoDelft’s main areas of expertise reflect the traditional concerns of the Netherlands and its mainly estuarine conditions, such as soft ground geotechnics, water control and risk management. Thus, as part the recent impetus on bored tunnelling as opposed to immersed tube or cut and cover construction, projects have mainly centred on the efficiency of TBM methods in the generally fine, organic and waterlogged deposits of the central and western parts of the country. This obviously includes the effects of tunnelling on adjacent structures such as dykes, waterways, bridges, piles and the foundations of ancient buildings.
Risk limitation management is central to current and developing client services. In the underground construction sector this allows the optimisation of the construction methods within the actual risk envelope rather than risk perceived without a scientific basis. This, in turn, can permit improved construction efficiency.
These are only the end results however, and they have to be based on strategic development which GeoDelft carries out in co-operation with it network partners. Such work is part of the ‘innovation cycle’, which is used as the basis for all project control in which there is continual interaction of calculation models, practical experience and physical modelling. The aim is for calculation models to increasingly match real conditions, and so improve design efficiency and risk control.
Thus, GeoDelft and other Dutch research and development organisations with which it co-operates use both monitoring of full-scale tunnelling projects and physical monitoring under laboratory conditions. The physical modelling promotes better understanding of the processes involved in, as examples, ground movements in settlement, piling and soil improvement.
Underground structures and infrastructure is one of four main lines of activity at GeoDelft, the others being the environment, surface structures and infrastructure, and dynamics. Current major activities within the underground construction sector include centrifuge work, research into grouting processes and their effects, and use of ground freezing in clays, sands and similar soft ground conditions.
The first of the r&d programmes in the current ‘push’ for underground construction development was led by COB, the Centre for Underground Construction, but its first programme is complete.
H M Schroten, chairman of COB’s Supervisory Board, commented on GeoDelft’s role, in the early 1990s, in the drive for more underground research and development. "That profuse initiative still continues to characterise the institute. It is alert, looks to the future, carries our practical trails, and has good contacts in the field."
Continuing Schroten said, "The Department of Public Works, Water Management and Transport (Rijkswaterstaat), for instance, would no contemplate carrying out large innovative projects such as the Heinenoord Tunnel, the HSL-Zuid or the Amsterdam Noord-Zuid metro line without GeoDelft." Schroten cites other qualities of GeoDelft such as its contacts with other research bodies (through the Delft Cluster for example), its testing of theories into practice, and its contacts with industry.
The early research by Dutch tunnellers into methods new to the Netherlands included visits to many parts of the world. That to Japan has resulted in permanent links including a partnership between GeoDelft and the GRI geotechnical institute. This is part of a general co-operative programme carried out by the Delft Cluster.
Current GeoDelft underground construction research topics include:
Studies on pile extraction centre on the Sophia rail tunnel on the Betuweroute. Here a combi-wall of pipe and sheet piles was lifted by various methods so that they could be compared in terms of technical feasibility, the effects on the subsoil, and also on surrounding structures. Sheet pile and combi-walls are frequently used to form pits for tunnel access shafts or trenchless technology pits, but in emphasising their support function, the possible deleterious effects of support removal can be overlooked. The incentive for such research is the many pits that will be required on the HSL-Zuid route for tunnel shafts, cut and cover pits and aqueducts.
The chosen design and construction method for the Westerschelde highway tunnel in the south of the Netherlands (T&TI Jan ’01 and Feb ’00) necessitates ground improvement for the excavation of cross passages between the tunnel twin bores. The freezing work, and its effects, in the main ground types (clay and sand) is being heavily monitored to provide data for mathematical models which, in turn, can be used for future designs.
Grouting
GeoDelft’s work on grouting is concerned mainly with the pressure at which annular grout is injected into the tail gap of TBMs. It has been shown that the pressure has a great influence on deformation of the surrounding (soft) ground. Practical text programmes mainly using GeoDelft’s Geocentrifuge are aimed at creating calculation models. Part of the monitoring programme for the second Heinenoord Tunnel has shown that current three-dimensional calculation models cannot easily predict resultant soil deformation in advance. Analyses showed that particular areas for weakness were the pressure distribution in the grout and the time taken for the grout to harden. The Geocentrifuge models to 1:150 scale, subjected to centrifuge forces 150 times that of normal gravity, show patterns of grout distribution with full instrumentation in the surrounding ‘ground’.
Related Files
Measurement test field
‘Innovation Cycle’
Subsidence trough measurements
Laser measurements
