342 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[September, 



work enclosing the area of the pier, keeping the cylinders in position 

 below, the same object being gained above by means of a guide band 

 of wrought iron, with friction rollers playing against the sides of the 

 cvlindcrs, and kept in position by chain guys with adjusting screws. 

 This plan was adopted at the T head, tlie amount of excavation being 

 less, and some of the cylinders of this portion of the pier were bot- 

 tomed in three or four tides, and the excavation got out dry from the 

 ground being less disturbed ; for, in the other case, the larger cylin- 

 ders, notwithstanding all the care taken to support them, followed the 

 inner cylinders either by sliding through the clamps, or dragging 

 down those temporary piles driven to the least depth. 



When the cylinders were placed in position a weight of from 5 to 

 10 tons was placed on them, driving them from 4 to 5 feet into the 

 mud, and the excavation being carried 12 inches below the sharp edge 

 of the bottom cylinder, the weights were again applied. 



The cylinders being sunk to the required depth upon the solid sub- 

 stratum, and the bottom levelled, a floor vpas formed of a couple of 

 courses of dry bricks, and a thickness of IS inches or 2 feet of brick- 

 work, from thence brought up in Roman cement, with two courses of 

 plain tiles also in cement to break joint. This preoautinn was taken 

 to keep out the land springs, which in some of the foundations came 

 up in considerable volume ; the spring water was led up through the 

 brickwork by an iron pipe bedded upon the dry bricks below, channels 

 being led to it ; the suction pipe of the pump being connected with it, by 

 this means the water was kept below the work as it was got in ; when 

 the cement bottom was finished it was left a tide, the spring water 

 flowing over it through the pipe, and the river water by plug holes in 

 the cylinders; at low water the cylinder was again pumped dry, the 

 pipe was then filled up with concrete, formed of tine Thames ballast 

 and cement, to set quickly, and a blank flanch screwed on at top. In 

 some cases it was necessary to bring up an additional length of pipe, 

 and a larger body of brickwork, before stopping out the spring water. 

 This on account of a larger supply, and with the outer foundations of 

 the T head a large bodv of cement concrete was put in through the 

 water imtil sufficiently "high to get in the cement brick bottom, the 

 springs from the chalk being very powerful at the extremity of the T 

 head and varving with the tide, the concrete being put in at low 

 water, when the springs were weakest. 



The brickwork above the cement bottom was brought \ip in pozzo- 

 lana mortar, iron hooping being introduced every fourth course laid 

 crosswise to bond the whole together; a cast iron cross is in each 

 foundation bedded in the brickwork, at the level shown; through this 

 a 2 inch wrought iron bolt is led and built into the work, leaving a space 

 of 4i inches square around it for play, to assist in adjusting it in its 

 place by wedges upon the completion of the brickwork, and the space 

 around the bolt is filled with thin concrete. This hold down bolt 

 passes through the Bramley Fall stone base, which forms the cap to 

 the pier and upon which the column is bedded, the base flanch of 

 which is let in for its thickness into the stone ; the through bolt is 

 screwed down upon the inner flanch of the column through the medium 

 of a cast iron cross, the arms of which bed upon the flanch, the nut of 

 the through bolt being screwed down against the boss of the cross. 



Two lengths of cylinders are left in around the brick pier, thus 

 forming a casing to it; the upper lengths of cylinders were unbolted 

 at the second horizontal joint from the bottom when the work was up 

 to that level ; and when the stone was set and the column fixed, the 

 temporary lengths of cylinder were drawn up over the shaft, the caps 

 being cast separate and bolted permanently to the shafts upon the re- 

 moval of the temporary cylinders. 



The prinripal novelty in these foundations is, applying cast iron 

 cylinders in such a way as to exclude the flow of a rapid tideway, 

 tiius enabling the men to work at nearly all times of tide, and when 

 the bottom is once got in, at any time; thus dispensing with a large 

 amount of pumping, which is proved by the fact that these foimdations, 

 at so great a depth and with so large a head of wafer, were kept clear 

 of water by hand-pumps, and a steam engine dispensed with; with the 

 greater number of the foundations but little dilflculty was experienced 

 in keeping down the water v;ith single 6 inch pumps, but with the 

 outer ibundations of the T head a double-headed pump worked by a 

 large gang of men was used, on account of the powerful springs before 

 referred to, coming into some of the cylinders at certain times of tide 

 at the rate of SO gallons per minute, nor could the water in these cases 

 be kept down beyond a certain point, viz. 12 to 18 inches above the 

 bottom, for which reason it was found next to impossible to get in 

 brickwork, although clamps of several bricks cemented together were 

 tried, and the cement concrete was adopted, let down in buckets and 

 upset after passing through the water, and trod down by the workmen 

 at the same time. 



It was usual to have a tier of three cylinders in hand at one time, 

 and at one period at the T bead four were in operation at once ; but 



it was found advisable not to bottom more than one at a time, as, 

 the experiment being tried, it was found that on tapping the springs 

 in two cylinders at once there was a communication between the two, 

 and if the pumps were not kept at work in each at the same time an 

 increased supply ensued, from the water accumulating in the other 

 cylinder, and the height of this column of water determining the force 

 of the spring in the other cylinder. 



The usual course was for one cylinder to be pitched and loaded, in 

 another digging proceeding, and in tlie third for the builder's work 

 to be in hand. 



The cylinders or wells of brickwork used for foundations in India in 

 sinking through sand, as described by Capt. Goodwyn at the Institu- 

 tion of Civil Engineers the session of 1842 (See Vol. 5, p. 164), are 

 sunk with the water within them, and the iron cylinders used by Messrs. 

 Walker and Burges for the Point of Air lighthouse, as described in 

 the last number of this Journal, were only sunk when the tide had left 

 the sand bank on which the foundations for that structure are formed ; 

 and we believe this is the first instance of cylinders being applied so 

 as to exclude the tidal flow of a rapid river, making them eft'ect the 

 same object as a cofferdam ; or that cylinders have before been applied 

 for the purposes of foundations for a structure of this kind on so large a 

 scale. In reference to these cylinders, it may be observed in conclusion 

 that the principal difficulty experienced in sinking them was — The 

 extreme accuracy required in placing them in position, and the still 

 greater care required in keeping them there and upright, though this 

 may be most certainly effected by a proper system of guides to keep 

 the cylinder in position, but leaving it free enough to sink readilv. 

 In one or two cases, when these cylinders were first commenced, 

 considerable difficulty was entailed from not attending sufficiently to 

 this, as the cylinders got out of position, and in replacing them the 

 ground got disturbed and caused blows through the sand stratum over- 

 lying the chalk, the mud and sand coming up into the cylinder; as, 

 however, the work advanced, this was entirely obviated, and the ex- 

 cavation got out comparatively dry, and in the majority of cases with- 

 out a blow. 



Great care was requisite in fixing the columns, for each being 

 placed on a separate base, rendered greater attention necessary in 

 setting them. They are, considering these circumstances, remarkably 

 level and lineable with one another. There are three columns in the 

 width of the pier at each point of support, and they are 15 ft. apart 

 from centre to centre, leaving a space of 10 ft. between the caps, which 

 is occupied by a cross brace bolted to the caps ; and the columns most 

 exposed to vibration are farther secured by 2-in. wrought-iron dia- 

 gonal tie-rods, bolted to lugs cast upon the columns and tightened 

 up by gibes and keys ; the iron girders supporting the platform and 

 entablature are bolted to the caps of the columns, the bolt-holes 

 being slotted and spaces left between the ends of the girders to allow 

 of expansion and contraction of the metal, the large girders, six of 

 which are 55 ft. and three 56 ft. in length, weigh eight tons each, they 

 are parallel, 3 ft. in depth, and are cambered U in. to allow for de- 

 flection ; to diminish their weight the sectional area is reduced to a 

 minimum at the ends in the thickness of the top and bottom flanches 

 and connecting web ; the seats were carefully fitted to the plane sur- 

 faces of the capitals by means of wrought fillet pieces rivetted to the 

 seats; projections are cast on the upper side of the girders to receive 

 the joists, which are fastened to them by clip-bolts, taking hold of the 

 girder underneath the top flanch, thus obviating the weakening of the 

 metal by holt holes. All the large girders were proved up to a weight 

 of 45 tons in the middle, with which they deflected on an average li 

 in. coming back to their original curve ; and the smaller girders up to 

 20 tons. The cast iron pilastre standards have a bearing upon the top 

 of the girder by means of a bracketted projection with a clip embra- 

 cing it, and the bottom of it abuts against the face of the girder on 

 the outside: at the centre? of the girders, where the bottom web is 

 thickest, it also obtains a bearing, and is secured to the girder at the 

 centre by one inch wrought-iron bolt, by this arrangement bolt-holes 

 are almost dispensed with; the standards being hollow form the pipes 

 to carry the water oft' from the roof, the projecting foot resting on the 

 girder forming the shoot to deliver the same. The entablature, which 

 is seven feet in height, and of cast iron, forms also the parapet to the 

 platform, and is formed of three tiers of castings, bolted together and 

 strengthened by feathers and brackets: this entablature when fitted 

 has a bearing upon the capitals, and is kept in position laterally by 

 bolts fixed to lugs cast upon the standards, with pipe washers to keep 

 them in position; the bolt-holes are slotted so that the entablature 

 may be affected by expansion or contraction without reference to the 

 girders, or standards, provision being made for it at either end, at the 

 south end next the abutment by a recess in the stone work: the en- 

 tablature while fitting obtains a bearing upon the lower web of the 

 girder, but when fixed will be unaffected by any deflection in the 

 girders, supporting itself, andi forming a horizontal line. 



