Engineering Wonders of the World
Volume I

THE MANCHESTER SHIP CANAL. 161 Embankment carried across Pool Hall Bay. Operations the first inter- rupted. therefor to be filled. Meanwhile the hearting had become sodden and covered with mud, and when fresh clay was tipped over it forced the soft clay and mud over the tops of the rubble banks on either side. The soft clay on the slopes had therefore to be cut back and replaced by rubble. Gradually the embankment reached the de- sired height across the full width of the bay ; and when it was seen to stand the test satis- factorily, an opening through which the tide had ebbed and flowed during the process of building was closed. A tim- ber viaduct was temporarily carried across the gap, and tipping operations began at low water, when the inner area was dry. This work was completed before the tide again flowed. Simultaneously, the facing of the outer slope of the embankment went on. The sandstone obtained from the rock cuttings of the Canal served excellently for the purpose. During the excavation, pockets of sand were found below the clay, and through one of these water forced its way under the embank- ment into the cutting. When blow ” made its appearance, sand and water accumulated in the cutting in quantities sufficient to interrupt operations, and the portion of the embankment directly affected indicated a settlement of between two and three feet. It was then decided to take borings along the base of the inner slope, in order that the full extent of the sand-pockets might be ascertained. The examination showed that protective measures were demanded for a distance of 860 feet. Accordingly a row of sheet-piling was driven in a line, 15 feet away from the base of the inner slope. “ This,” said Mr. Eliot, “ completely stopped the settling of the em- bankment, and reduced the run of water to a mere soakage.” (1,408) The second embankment, erected across Ellesmere Port Bay, differed from the others in that its main portion was not called upon to exclude tidal waters during con- struction, but only to retain the water in the Canal when the whole work had been finished. From end to end this embankment is 6,200 feet long. In the middle of the bay stands the little town of Ellesmere Port, with the docks through which the canal of the Shrop- shire Union Company have access to the Mer- The Second Embankment. SECTION OF CANAL AT ELLESMERE PORT. the sand-bank Thirteen Thousand Piles driven. sey estuary. Hence the prevailing conditions necessitated treatment of an exceptional char- acter. Many interests had to be protected, and it was not without some bold experiments that (he best means of carrying out the work were found. Thirteen thousand piles, each 12 inches square and 35 feet long, had to be driven, by means of a water jet, through facing Ellesmere Port. The sea-wall itself, 6,200 feet long and 12 feet wide, was formed with clay hearting protected by heavy blocks of stone laid on rubble backing and faced with heavy masonry. A little beyond Ellesmere Port the river Gowy is carried under the Canal by two cast-iron siphons, 400 feet in length and 12 feet in in- ternal diameter. Sluices are provided to scour out any deposit that might accumulate, but the work is so successful that the flow of the river keeps both siphons clear. The third embankment, constructed across Ince Bay, is 5,900 feet long, and its height averages 18 feet above the original surface of the ground. At the east side, for a distance of 3,400 feet, the embank- 11 The Third Embankment.