A new publication from the UK's Construction Industry Research & Information Association provides a guide to the latest thinking on scour.
Structures built in or near rivers and other channels can be vulnerable to scour around their foundations. If the depth of the scour becomes significant, the stability of the foundations may be endangered, with a consequent risk of damage or failure of the structure.
In the past 15 years, there have been several bridge failures, resulting in transport disruption, economic loss and, on occasion, loss of life.
Some of these failures are included as case studies in CIRIA's comprehensive new guidance manual, Coastal and marine environmental site guide which aims to fill the shortfall of information on the complex factors concerning scour.
Protection works for preventing scour need to be designed to withstand the flow forces imposed on the structure and have to be practicable to build and install, while minimising adverse environmental effects.
The manual covers methods for estimating scour and related hydraulics, geotechnics, risk assessment procedures, remediation of affected structures, design for scour protection and monitoring, environmental factors, risk assessments, and cost and benefit analyses.
The protection measures covered in the report are relevant worldwide, and to new as well as existing structures. These start some way remote from the structure for scour reduction, the design of the structure itself against scour, and the use of additional protection measures.
Included are gabions, articulated concrete blocks, falling aprons, grout-filled mattresses and bags, bituminous systems, concrete aprons, stone pitching, sheet piling, protective collars, and pile caps and footings.
Aware of an absence of guidance in a format suitable for use on site, the emphasis of the CIRIA guide is on accessible information on appreciating, avoiding and mitigating the effects of poor environmental practice of coastal and marine construction projects.
The guide provides practical advice on the potential impact of construction works. It intended as an essential reference book, user-friendly guide and a training aid.
Research role CIRIA (Construction Industry Research and Information Association) is concerned with improving the performance of all involved in construction and the environment. CIRIA provides real industry solutions through its collaborative research programme, the results of which are published and made openly available to industry.
The collaboration and input of stakeholders from all areas of industry is a significant element in producing authoritative industry-wide guidance.
As a result, many CIRIA publications are used all over the world, such as the Beach management manual, the Manual on the use of coastal rock in coastal and shoreline engineering and Design of flood storage reservoirs.
The Manual on scour at bridges and other hydraulic structures is an international report, with input from organisations in Hong Kong, USA, Denmark, UK, Czech Republic and New Zealand.
CIRIA takes a leading role in many water-related engineering and environmental issues including coastal and marine, sustainable options for drainage, beach management, scour and flood storage reservoirs as well as organising international conferences such as 'European marine sand and gravel - shaping the future' in February 2003.
For further information, visit www. ciria. org. uk or contact CIRIA, 6 Storey's Gate, London SW1P 3AU, UK. Telephone: +44 20 7222 8891; Fax: +44 20 7222 1708; Email: enquiries@ciria. org. uk