The Highways Agency has a key new role in delivering the Government's integrated transport plans as set out in the recent White Paper. The agency will contribute to sustainable development by maintaining, operating and improving the motorway and trunk road network in support of
In this new role the agency will influence the range of services offered to road users and non users alike. This in turn will influence the range of services it purchases from its major suppliers.
What will be the effect on the range and scope of services supplied by the geotechnical industry?
While discussion following publication of the White Paper has concentrated on transportation issues, it is self evident that all transportation systems require infrastructure and all infrastructure is supported on the ground. There is a clear and continuing role for the geotechnical industry to 'support' government policy on integrated transport.
The Highways Agency will develop its role as network operator by implementing traffic management, network control and other measures aimed at making best use of the existing infrastructure and facilitating integration with other transportation modes. For example driver information systems are supported by gantries and the gantries are inevitably supported by piled foundations. There is scope for non destructive tests that provide assurance about the load carrying capacity of the pile without resorting to time consuming load tests and associated traffic management which disrupt the network. Gantries require the installation of cabling and there is a role for trenchless techniques to avoid carriageway closures.
Improving the range of services to users and non road users will include encouraging cycling and walking by providing more cycleways and footpaths near trunk roads. The geotechnical techniques developed for motorway widening such as soil nailing, gabions and reinforced soil are ideal for providing cycleways and bus lanes within the existing land take.
Maintaining the trunk road network will be a priority with the broad objective of minimising whole life costs and minimising disruption to the road user. Shallow slips on ageing earthwork slopes account for an increasing proportion of the trunk road maintenance budget. Innovative repair techniques will be needed to limit the traditional one of excavation and replacement, so there will be an emerging role for methods using vegetation, lime piles, geotextiles and soil nails.
Quantitative risk assessment strategies will be developed to ensure that repair techniques are deployed at locations where the consequences of failure are most severe. Managing and maintaining the asset will require a better understanding of the state of the network. Geotechnical data management systems are under development to assist with managing the earthwork asset. These systems are likely to include information ranging from the location of site investigation data to slip repair histories.
The Roads Review and the Comprehensive Spending Review have identified a tightly focused programme of improvements comprising 37 schemes at a cost of pounds1.4 billion. Historically, unforeseen ground conditions have been the major source of cost increases on traditional forms of highway construction contracts.
Management of geotechnical risk will be a key consideration in the selection of future forms of contract. The Highways Agency is participating in a DETR sponsored project with the Institution of Civil Engineers aimed at managing geotechnical risk to improve productivity in the UK construction industry.
Sustainable construction techniques will be required to minimise the impact of the trunk road network on the natural and built environment. Highway earthworks will need to make the maximum use of on site materials in order to reduce off site disposal and the import of valuable natural aggregates. The Landfill Tax provides a financial incentive to achieve this objective. Since the introduction of the tax there has been greater use of lime modification to render unacceptable materials acceptable.
The Specification for Highway Works has also been modified to encourage greater use
of asphalt planings as a capping material. Sustainable construction will require the use of innovative construction techniques and this has been achieved through the use of 'value engineering' and partnering arrangements.
The Highways Agency's business is underpinned through a programme of research & development to ensure value for money, safety of the road user and protection of the environment. The agency will be seeking to achieve more rapid implementation of the research results.
Geotechnical works are usually hidden below ground but the benefits are never out of sight.
Philip Wilson is group manager, Geotechnics & Ground Engineering, Highways Agency