1841.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



805 



wall of rough rubble stone, laid dry, with a slope of about two to one ; the 

 peat moss backing, cut into blocks lather thicker than usual, is laid in 

 courses well bonded and beaten together ; it is thus consolidated throughout 

 the height of the wall. Upwards of twenty years have elapsed since some of 

 the first embankments were made on this principle ; they have perfectly 

 answered the purpose, and have been the means of effectually reclaiming a 

 great extent of valuable land. 



n'arpinff sill. — The author also states, that he has lately been occupied in 

 forming a defence, by warping silt, with whin or gorse kids, laid horizontally ; 

 a method which he prefers to that practised in Liucolnsbire, where the kids 

 are placed upright. He keeps the kids in their positions by means of stones 

 laid on tliem, which are removed as the surface rises ; fresh kids are tlien 

 added, and the stones relaid. 



The communication is accompanied by three sections of the sea defences, 

 as they are executed, and by some corroborative testimony as to their effi- 

 ciency, by Mr. Lewiu, of Boston, who has examined and reported upon them. 

 Full instructions are also given for constructing the different kinds of de- 

 fences mentioned. 



" In account of the repairs done to the Beechwood Tunnel, upon the Lou- 

 don and Birmingham Railway, September 1840." By Thomas M. Smith, 

 Grad. Inst. C. E. 



The tunnel is built of brick, is 302 yards long, and passes through strata 

 consisting of alternate layers of rock and marie, abounding in springs of 

 water; it was completed at the latter end of the year 1837; that winter 

 being of unusual severity, many of the bricks were partially destroyed, owing 

 to their containing lime, upon which the weather acted. Mr. Robert Ste- 

 phenson first contemplated applying a coat of cement throughout the inside 

 of the arch, but it was apprehended that it would not adhere, in consequence 

 of the constant dripping of the water. No positive steps were, however, 

 taken until the effects of the winter of 1S39-40 had so injured the brickwork 

 as to render further delay dangerous ; it was then resolved to line the whole 

 length of the tunnel with an interior brick arch, 9 inches thick, so as to sup- 

 port and insure the stability of the old work. 



For the purpose of executing the work with facility, all the trains of car- 

 riages were diverted upon the down line through the tunnel, and for a quar- 

 ter of a mile at each end ; no up train was allowed to pass upon the single 

 iine while a down train was in sight ; a hoarding was then erected between 

 the lines of railway throughout the length of the tunnel, to protect the 

 workmen, and to prevent the building materials from interfering with the 

 trains. The internal casing of brickwork, 9 inches thick, of English bond, 

 was then carried up one side to the height of 4 feet 9 inches above the 

 springing ; a course of York paving 4* inches thick, was at this point bonded 

 into the old work, and the new work was securely attached beneath the 

 stone bond course by iron wedges, and regular half brick toothings were in- 

 serted, at intervals of 2 feet 3 inches apart, in chases cut into the old work ; 

 by these precautions the new work was secured from being detached, and 

 from falling upon the passing trains. 



One side being finished throughout its entire length, the trains were turned 

 upon the up line, and the same mode of proceeding followed with the other 

 side. A series of bearers, 6 feet apart, were then placed over head, and a 

 close flooring laid so as to serve for scaffolding for the workmen, and to pre- 

 vent the building materials from falling upon the rails. A pair of ribs were 

 then raised upon each bearer, and keyed with a strut, 7 inches below the 

 crown of the arch ; the supporting stays were fixed, the laggans laid upon 

 the ribs, and the brickwork of the arch was constructed in English bond 

 throughout the whole length, and on both sides of the tunnel, simultaneously, 

 to witiiin 2 feet of the crown ; a moveable centre, 2 feet 3 inches long, was 

 then introduced, and the arch was closed in with two half brick rings. 



The whole of the work was done with blue hard burnt Staffordshire bricks, 

 laid in cement and sand, in equal proportions, for the side walls ; for the 

 arch, up to within 15 inches of each side of the crown, two-thirds of cement, 

 and one-third of sand : the two rings for keying up the centre or crown were 

 laid entirely in cement, without any mixture of sand. Previous to commenc- 

 ing the new woik, a series of chases were made in tiie old wall, w hich, when 

 closed in front by the lining arch, formed drains, 4 J inches square, termi- 

 nating in the culvert beneath the centre of the railway, and conveying thither 

 all the water, wliich would otherwise have separated the new from the old 

 brickwork. 



Tiiis work was finished, and the scaffolding removed, within the short 

 space of forty days, by Messrs. Grissell and Peto, under the direction of Mr. 

 Robert Stephenson, and the immediate superintendence of Mr. Dockray. 



This communication was accompanied by a drawing, showing the details 

 of the scaffolding, and the mode of construction. 



" Oa the formation of Enibaiihneiits and the fiUinq in behind retaininr/ 

 Walls." By John B. Hartley, M. Inst. C. E. 



The numerous failures of the embankments in the construction of railways, 

 and the constant occurrence of defects in retaining walls, induced the author 

 to offer some remarks upon the suhiecf. He first examines the ordinary 

 mode of commencing the embankment at the contemplated finislied level, 

 and proceeding with the work at that height throughout, leaving the mate- 

 rial to find its own inclination ; forming the required slopes on the sides 

 when the filling is completed. This he contends (although without doubt 

 the most rapid mode of proceeding) is defective in principle, for the material 



as it is deposited forms layers or strata at such an inclination as its nature 

 permits, and always has a tendency to slide in the direction of the slope. 

 In such cases, as the centre sinks, the sides slide away, and having nothing 

 at the feet to resist such a tendency, they are carried out to a dangerous 

 extent. This is particularly the case with clay embankments, for the mate- 

 rial is generally brought from the cuttings in large lumps, which cannot be 

 consolidated as they are deposited ; the water lodges in the interstices, keep- 

 ing the bottom soft, and when it begins to subside it slides away, until it 

 has formed itself into a slope at which it can resist the pressure. To prevent 

 this sliding, the author recommends proper footings being prepared for the 

 sides of the embankments by cutting trenches, about 4 feet 6 inches deep, 

 along the bottom line of each slope, and forming a "cop" of sods or of 

 stones, placed at right angles to the line of the slopes. These footings must 

 be of a strength proportioned to the height of the embankment, and the 

 whole length should be completed before the filling is commenced, that they 

 may become solid, and the sods have grown together, before the weight is 

 brought upon them. 



Proposed mode of fllinij. — He advises, also, that instead of carrying on 

 tlie filling in one lift, two embankments should be made, varying in height 

 from 15 feet to 20 feet, according to the nature of the material, wide enough 

 for two earth wagons on the top, one of them running along each side of the 

 site of the contemplated embankment ; a valley would thus be left in the 

 centre at the junction of the two inner slopes. When they have been carried 

 along the whole length, or to such a distance as would insure their being 

 considerably in advance, the second or the final lift may follow. With clay 

 or soft materials, four low lifts following each other would be advisable ; 

 with these precautions slips of the embankments would be of rare occurrence. 

 The bottom would become solid by the passing of the weight over it, and the 

 succeeding lift being thrown into the centre valley, must settle vertically. 

 The subsidence, which is always in the line of inclination, would be concen- 

 trated and thrown inwards ; by these means the width of the slopes would 

 be restricted, and the work would be constructed much cheaper, there being 

 a saving of both land and labour. Land springs, which are usually only dis- 

 covered by the pressure of the weight above, woidd be more easily reached 

 with the low lifts than when covered by the heavy ones. 



This mode of construction has been practised by Mr. Jesse Hartley, on 

 the Manchester and Bolton Railway, where the embankments were very 

 heavy, and the material of the worst description ; yet the work was executed 

 in a most satisfactory manner, and the cost of the maintenance of way upon 

 that line is quoted as being less in pioportion than on any other railway in 

 the kingdom. Tliis method may require more time, and be a little more ex- 

 pensive, but the author is of opinion that the trifling difference in time and 

 cost would be amply repaid by the freedom from expense when the road was 

 opened. 



Retaining Walls. — The author then examines the subject of retaining walls. 

 He considers the method of fliling towards the wall from the natural bank 

 behind to he highly objectionable ; the material lies in strata at the angle at 

 which the deposit is made ; as the quantity increases, the subsidence com- 

 mences, and the earth slides dowiiwards, throwing its whole weight against 

 the back of the wall. The tendency to slide is frequently accelerated by the 

 natural form of the ground upon which the earth is thrown, as it not unfre- 

 quently inclines towards the wall, in which case the pressure will necessarily 

 be in proportion to the inclination of the slope, and the nature of the mate- 

 rial of which the fliling is composed. The wall at Hunt's Bank, on the 

 river Irwell, is instanced as a fadure of this description. The wall, about 

 100 feet in length, and 20 feet in height, 5 feet thick at the bottom and 

 3 feet 6 inches at the top, built of ashlar masonry strengthened by counter- 

 forts, was forced into the stream by the pressure of the earth behind it. 

 With proper attention to the manner of filling the ditferent materials, a com- 

 paratively slight wall may he constructed to sustain a considerable weiglit of 

 backing.' The author lays down as a rule that, wherever it is practicable, all 

 filling behind walls should be commenced at the wall, and be proceeded with 

 from thence towards the solid ground, by which means the strata would be 

 inclined in a simdar direction ; ledges or benches, either level or inclined in 

 an opposite direction to that of the bank, should be cut in the solid ground 

 to receive the filling, and counteract its tendency to slide. The weight 

 should not be laid too quickly upon a new wad, aud if with these precautions 

 care be taken that the couuteriorts are constructed simultaneously with, and 

 well tied into, the wall, a comparatively weak structure will bear a heavy 

 mass of filling. 



The author gives as an example the retaining wall constructed on the west 

 side of Jackson's dam, near the Brunswick Graving Docks, Liverpool. This 

 wall, although built of slight dimensions, and tilled behind with material of 

 the worst description, resisted perfectly all strain ; this could only be attri- 

 buted to the filling having been gradually done in the manner which the 

 author's practice leads him so strongly to recommend. 



This communication was accompanied by diagrams descriptive of the mode 

 of constructing embankments. 



May 25. — Henry Kodinsov Palmer, V.P., in the Chair. 



" A Tabular Statement of the Dimensions and Proportions of Forty Iron 

 Vessels." By Lieut. E. N. Kendall, U. .N'., Assoc. Inst. C. E. 



The vessels, the dimensions and proportions of which are given in this 

 communication, were all built by Mr. John Laird of Liverpool; they are 



