Engineering Wonders of the World
Volume I

162 ENGINEERING WONDERS OF THE WORLD. ment is 30 feet wide ; but on the western side, over a length of 2,500 feet, the width is reduced to 20 feet. Here the ground consisted of very soft mud and silt, which extended below the bottom of the Canal cutting. The engin- eers were convinced that the ordinary sec- tion of embankment, with an inner slope of 1 to 1, carried down to the bottom of the Canal, would never rest upon such a foun- dation. A row of sheet-piling was therefore driven along the line where the inner slope cut the surface of the mud, and the width of the em- bankment was reduced so as Soft Mud £0 njne f eef, £0 ^].ie wijth of sl°Pe fr°m the top of the dealt with sheet-piling to the bottom of the Canal, the whole of this slope being formed of rubble. The soft mud, extending to a depth of four or five feet, was taken out of the space between the sheeting and the rubble. In its place clay was tipped to form the Centre heart of the bank, and simul- ^Canal taneously faced on both slopes changed with rubble. But when the excavation for the Canal began, the ground was so soft that the top of the sheet-piling gave way towards the cutting. In these circumstances, the centre line of the Canal had to be removed for a certain dis- tance landwards, so as to allow of a slope of 4 to 1 from the top of the sheet-piling to the bottom of the cutting. This arrangement proved effective, and the formation of the embankment was continued. In the next (centre) section sandstone rock lay at the foot of the inner slope, close to the surface of the mud. Here a trench nine feet wide and about nine feet deep A Trench wag formej jn the mud by in the „ _ . Mud means of a Priestman grab, and filled in with rubble, to form a footing for the outer slope of the embankment. The rock on the inner slope, being soft in places, was liable to be scoured away, and the precaution was adopted of in- INCE BAY EMBANKMENT (WEST SECTION). troducing a brickwork facing to that portion of the rock. For a distance of 1,400 feet the foundation for the eastern section of the embankment consisted of sand, with an upper layer of soft mud. This formation neces- sitated a different method of t procedure ; and in order that use(j the weight might be kept down as much as possible until the excavation had advanced sufficiently to permit of the inner INCE BAY EMBANKMENT (CENTRE SECTION). slope being formed, the boulder clay was not in the first instance tipped to the full height of the bank on the outer slope. The sand was very wet, and the excavation at the back had to be carried out with extreme care. INCE BAY EMBANKMENT (EAST SECTION). Gradually the sand was drained, and it then became safe to place rubble on the slope,