Discussion. The Royal Portbury Dock, Bristol.

Abstract

The Royal Portbury Dock, Bristol F. IRWIN-CHILDS, W. J. SlVEWRlGHT 81 P. T. SHAW Messrs Irwin-Childs, Sivewright and Shaw Among the interesting features in the scheme not fully dealt with in the Paper are the unusually large mitre gates with their unique action which has enabled the range to be extended. The latest comparable examples of locks built in Europe and Russia are all reinforced concrete cantilever structures of conventional form and proportions, built in open excavation in the dry, with a concrete volume ranging from 2 to 4 times that of Portbury. Indirect savings arose from the overall concept at Portbury and particularly from major excavation and filling executed in the dry.71. There were constraints imposed by the largely rural site which nevertheless carried a number of public utilities which had to be maintained. 72.In the diaphragm work the closeness of the bond between soils and concrete was illustrated by the appearance of the walls after exposure. The greater thickness of the overlying silts was largely discounted when assessing the resistance to overturning of the structure, greater reliance being placed on the mart, the quality and dryness of which were shown after excavation of the cross-lock tunnels and the circular arch cofferdam.73. There were no fatalities among the labour force over the 5 year construction period.M r A. J. S. Mansfield, Edmund Nuttall Ltd The.diaphragm walling contract at Bristol, on which I was agent, represented about 1% of all the world's diaphragm walling then constructed and was the largest single contract let for the Royal Portbury Dock.75. My comments will be confined to construction details. The contract was undertaken by the joint venture of Edmund Nuttall Limited and SIF Entreprise Bachy of Paris. Possibly the greatest contribution to success made by Bachy was the grab which they brought to Bristol (Fig. 17). The characteristics which are noteworthy are the rope suspension, giving speed and simplicity of operation, and the long body which provided vertical directional accuracy so essential to the diaphragm walling operation. The grab dealt successfully with both the hard and soft ground found at Bristol.76. There were 500 reinforcement cages in the contract which were necessarily constructed horizontally on the ground, and had to be lifted to a vertical position to place them within the trench. The danger of permanently distorting a cage during lifting was overcome by providing adequate bracing within the cage, by using a stiffening strong back frame externally and by utilizing two cranes to carry out the lift.77. I should like to ask the Authors whether, with the benefit of the experience gained on other contracts since 1973, they would now adopt a different configuration for the panel layout, and in particular perhaps incorporate a shear connector such as the type used at Redcar.