18J5.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



45 



He liad used benching with good effect, where an ovcrlny of wet gravel 

 rested on day ; the method he adopted was to remove the gravel in the up- 

 per part of tlie slope, sulticicntly to enable a good catch-water drain to be 

 formed, along the bench in tlie clay, as shown at A, Fig. 2. 



Fig. 2. 



This plan he considered very effectual in certain positions, as a means of 

 preventing slips. Slopes of 1 J to 1 for a maximum height of 40 feet, which 

 had been so constructed, had stood well for upwards of :> years. 



In other situations, after sHps had occurred, he had used back-draining 

 witli good effect, where tapping and leading-drains had failed. The method 

 pursued, (Fig. 3) was to cut a drain at the back of the slip, (13,) so as to 



Fig. 3. 



— r.^rtp:v?T;J5l!i^'P 



intercept the water which flowed thither, either from tprines or bv infll 

 tration. " •' 



At the bottom of the drain was placed a round pot drain (C ) covered 

 with a tliickness of brushwood, (I),) and the remaining depth was filled in 

 with gravel or rubble. For positions where it was practicable to cut the 

 back-drain, he recoriimended this system. 



With reference to llie depth of cuttings and the angle of slopes, iu various 

 matertals and under dillereut conditions, he thouglit that each case must he 

 regulated by the particular nature of the soil, the facilities for draina-^e 

 and the means adopted, besides many other local consideration, so that 

 It was nearly impossible to lay down any arbitrary rules on the sul.iect 



In one situation, he had seen a cutting throuKh cravel and sin,l \t,^A 

 excellently at an inclination of li to l%l.hou!h tircutting w, 86 ?eet 

 deep and on one side was placed a spoil-bank of 21 feet in height, makin" 

 no feet in all forming a regular slope. In another position, he had rnade , 

 cutting of 57 feet in depth, through gravel, which stood well atalTope of 1 



Eastern Couiilks Railway. 



Mr BnuFF stated that the timber staging erected on some of the Eastern 

 Counties Railway embankments, had not been resorted to for obviatin,, tl,» 

 formation of the clay banks in wet weather, but was merelv contrived for 

 expediting the work, so as to admit of the railwav being opened to the nut I> 

 at an earlier period than would have been possible had solid embankments 

 been first formed. The timber stagmg was erected on thrre embankments 

 which could not be completed in time, and on another where the nature of 

 the material, in its then wet state, would not admit of its beins formed tn 

 more than half its height; all these embankments had, however: since been 

 filled up to the regular level. " 



The cutting through lirentwood Hill, presented some features in the eve. 

 cution difierent from those on the Croydon Railway ; he presented to the 

 Ins itution a copy of the contract plan of the Eastern Counties Railwav with 

 such amendments and additions as were considered desirable, during the 

 progress of the works, and since their completion ^ 



The drawing gave a ground plan, (Fig. -t,) exhibiting the position of the 

 cutting, spoil-banks, ice, with longitudinal and transverse sections (Figs. 5 



Fig.' 



Brentiviiofl Ilill Cuttiii(j. Eastern Counties Hailway. 



and C) of the cutting, showing the extent of the excavation and the slopes, 

 the benchings, culverts, wells, drain-pipes, and gravel counterforts. 



The nature of the material of the cutting was sand, sand with loam, gravel, 

 and silt. 



The great difficulty experienced in draining the slopes, had arisen from the 

 slimy nature of the silt, from which the water could 'not be separated. Its 

 power of bohling water might be imagined, from the fact of a face of nearly 

 00 feet of slope, being expo'^ed during 2 years, without producing any sen- 

 sible effect in the drain:ige of the material. 



The silt had a constant tendency to How away with the water, and great 

 attention was directed to that point, in order to prevent the slopes from being 

 injured. 



The provision for upholding and draining the slopes comprised in the con- 

 tract, consisted of a fence ditch at the top of the cutting, a benching 10 feet 

 wide, half way down, and the ordinary side drains at the foot, with drain 

 pipes, running in various directions, along the face of the slopes. To this 

 was subsequently added a culvert, on the benching on each side, with proper 

 outfalls; then the wells (Fig. 10,) were adopted, and lastly gravel counter. 

 ^orts. The wells were not placed with any rcgiilaritv, but were sunk at (he 



wettest parts of the slope ; they were steined as in the ordinary well work, 

 until within a distance of about 3 feet from the bottom, where an inner ring 

 of brickwork 4i inches thick, was built in cement. The bottoms of the 

 wells were not bricked, but each had an outlet pipe of about 2 inches 

 diameter, into the open drain below it. There were twenty of these wells, 

 in the upper port of the north slope, ranging in depth from 15 feet to 20 

 feet, and 3^1 feet in diameter. In the lower part of the same slope, there 

 were twenty-five wells of the same diameter, but (uily 10 feet deep. In the 

 same slope, seven gravel counterforts of a prismoidal shape were afterwards 

 added ; they were formed by cutting out the requisite cavity, and harrowing 

 in dry gravel from above, without pounding. 



Neither wells nor counterforts bad liecn adopted on the south slope, which 

 was on the lower side; the cutting being through ground slightly inclined to 

 the south. 



These plans for draining the cutting were, Mr. Bruff believed, all designed 

 by Mr. John Braithwaite. 



Mr. Phii'I's had tried a somewhat different plan. .\ narrow trench was 

 cut along the wettest part of the slope, as deep as it could be excavated, 

 without much shoring of the sides ; a small ciilvcrt was laid in the bottom, 



