Engineering Wonders of the World
Volume III

GREAT UNDERPINNING ACHIEVEMENTS. BY W. T. PERKINS. A S a rule the public knows little of the / \ wonderful achievements of science in the field of what is technically known as “ underpinning,” a term signifying the substitution of new for old foundations or other supports of a building. Yet there is no class of work that involves more risk, and it is curious to note that, while superstructures are in the main raised from the designs of the architect, schemes of underpinning are very frequently entrusted to his companion the engineer. The author has selected three ex- amples of work of this kind, each employing features of its own, and they may be regarded as representing the best devices of some of the leading modern engineers. One of the most remarkable illustrations of underpinning is undoubtedly that which has recently been carried out so successfully at Winchester Cathedral. This Winchester veneraye structure, situated Cathedral. . at the bottom of a hill, near the river Itchin, is prominent among English cathedrals because of its great length. Serious Subsidences of the Structure. A few years ago, when the cathedral was being repaired by Mr. T. G. Jackson, R.A., the diocesan architect, in conjunction with Mr. J. B. Colson, the late ar- chitect of the cathedral, it was discovered that serious subsid- ences had occurred in various parts of the structure. The most alarming falling away, disclosed in the presbytery, amounted to nearly 2 feet 6 inches. Here the outer walls and their buttresses were considerably out of the perpendicular. The groined arches were distorted, and stones were occasionally falling from the roof, indicating that disintegration had actually begun. Sinking a trial pit some yards away, Mr. Jackson found under the clay a bed of peat eight feet thick, resting upon a solid formation of flint and gravel. Another excavation was made close to the south wall of the presby- tery, and at a depth of about eight feet below the turf the bottom of the masonry constitut- ing the foundation was laid bare. It was then ascertained that trees had been extensively em-