Figure 10.
The image compares two cofferdam designs, the original and the strengthening works. Both diagrams display vertical cross sections with marked geological layers. The left section, labelled Original cofferdam design, features a cofferdam platform at 104.6 metres A T D and a foreshore level at 96.6 metres A T D. Below, it lists various geological layers, including cofferdam backfill, alluvium, river terrace deposits, London clay formation, and Lambeth group, with depth levels indicated as 94.5, 92, and 91 metres A T D. The right section, labelled Cofferdam strengthening works design, includes similar depth markers but shows slight variations in the geological layers, with the foreshore level also at 96.6 metres A T D, and the deeper layers ranging from 93 to 91 metres A T D. Distinct patterns in the textures represent each geological material, contributing to the visual distinction between the two designs.Simplified comparison of the geotechnical model used for the cofferdam design and strengthening works (ATD = above tunnel datum)