Abstract

We are grateful for the comments made by Colin Warren concerning the stratigraphy of the sediments beneath Dubai Dry Dock. Like him we have seen these sediments at various stages in the development of the Dry Dock and elsewhere. The great diversity of strength, particle size, and range of composition of these sediments had to be considered all too briefly in the paper which was already of considerable length. Paragraph 4 of page 118, however, covers most of the points relevant to this diversity. We considered in some detail the relative weighting to be attached to the loss of material as fine particles and loss due to solution of gypsum, concluding that gypsum solution was the main cause of the settlement. The evidence from early cores shows that weak, silty layers of gypsum occurred at depths of about -17.5 and -21mHD. These could not be found in subsequent boreholes. We consider that the main settlement related to the removal of one of these layers (the upper one). More general removal of sulphate also took place but did not appear to lead to settlement of the magnitude recorded because the gypsum was dispersed within stronger rocks. There can be no doubt that gypsum solution has occurred and that the amount of gypsum originally present was of the correct order to account for the settlement observed and the recorded progress of the settlement. We found several thin layers of uncemented carbonate clay and silt in cores taken at various stages in the

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