1844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



359 



REVIEXVS. 



Practical Tannelling. By Frederick Walter Simms, C.E. London : 

 Trougliton and Simms. 1844. 



This is an excellent instance of what may be done for the interests 

 of science by an engineer closely engaged in professional pursuits, by 

 the proper adaptation of his exertions. Mr. Simms, as many other 

 engineers have been, was employed in superintending a considerable 

 tunnel, and by making careful and copious memoranda during the pro- 

 gress of the works he has been able (o produce a volume of verv great 

 value. He might, like many others, have pleaded want of time to 

 write a book, and so glossed over the want of industry or inclination, 

 which are too often the real grounds of neglect when parties are en- 

 trusted with the conduct of extensive operations. Mr. Simms, how- 

 ever, fortunately for the profession, and we think we shall in time be 

 able to say fortunately for himself, has made no such idle plea, but 

 given convincing proofs of its futility. We hope, indeed, this exam- 

 ple will not be without its fruit, but that many more, having much 

 better opportunities, may be urged to take advantage orthem. How- 

 ever well trained a man may be in a particular pursuit, however much 

 experience he may have had, and however well he may think ho is 

 acquainted with his duties, he will always derive benefit from the 

 careful perusal of the evidence of other men. Engineering after all, 

 however large its operations, has to deal with innumerable and minute 

 particles, with cubic feet of earth, with blocks of stone, with single 

 pieces of brick, and economy of materials, is only attainable by care- 

 ful calculation and comparison systematically carried out. In the 

 same way, much economy of labour, economy of time, safety and cer- 

 tainty of execution, could be obtained, and no one of his own indivi- 

 dual knowledge dare say that he has attained the maximum of these, 

 or is justified towards his employers in neglecting the proper and ob- 

 vious means of acquiring information. On the one hand, by obstinate 

 and ignorant adherence to old routine, we find scores of thousands of 

 the public money wasted on sewers; on the other, by the careful ap- 

 plication of science we find as many thousands saved. Nothing is 

 more easy than to say, make a tunnel of such a length, through such a 

 hill, give it an elliptical, parabolic, or other arch; but where, perhaps, 

 a hundred thousand pounds is to be expended, it becomes the peremp- 

 tory duty of the engineer to ascertain that the form he proposes, the 

 dimensions he has adopted, and the course he is about to pursue are 

 such as to elFect the end in view with the greatest regard to the inte- 

 rests of his employers ; and thus we say, however clever he may be, 

 he will do most satisfactorily to himself, and them, by availing himself 

 not only of his own experience, but of all records of the experience of 

 others. In the same way, too, that it is his duty to take advantage of 

 others' labours, and as he profits by them, does it become his moral 

 duty to repay the obligation by communicating also the results of his 

 own experience. This the Institute of Civil Engineers strongly in- 

 culcates and highly encourages; but we regret that many of its mem- 

 bers, old and young, do not practise it. There can, indeed, be little 

 doubt that from the want of such information being afforded, many 

 millions have been expended in the railway system alone, which could 

 well have been avoided. We therefore strongly urge all parties to 

 avail themselves of the opportunities within their reach for the illus- 

 tration of engineering science. 



Mr. Simms was employed first in constructing the Blechingley tun- 

 nel, on the South-Eastern Railway, and afterwards the Saltwood tun- 

 nel on the same line, works the joint cost of which was upwards of 

 £200,000, and he has minutely described the whole progress of the 

 works, with copious illustrations, and full details of every item of ex- 

 pense, so as to present a manual not merely useful, as he modestly 

 represents, to the beginner, but, for the reasons we have already men- 

 tioned, to the engineer of extensive knowledge and experience. 



In the first chapter Mr. Simms explains the geological character of 

 the country through which both tunnels pass, and the several difficul- 

 ties with which he had to contend. He shows by an abstract of the 

 payments that the works of the Blechingley tunnel, which is 1324 

 yards in length, cost £95,236, or about £72 per lineal yard. This 

 tunnel was entirely executed under the superintendence of Mr. Simms, 

 without any contractor, the company doing tlie work themselves, in- 

 cluding the making of the bricks. The other tunnel at Saltwood was 

 executed by contractors ; the first one failed, — the works were car- 

 ried on at the commencement with considerable difficulty in conse- 

 quence of the great body of water in the lower green sand, through 

 which the tunnel passes. After great labour, a neading or adit was 

 made quite through the bill, on a level with the bottom of the tunnel ; 



this being accomplished, the subsequent works were carried on with 

 comparative facility. The company then entered into contracts with 

 responsible contractors for the execution of the works at the sum of 

 £85,000, which, added to the previous expense, made a total cost of 

 £112,542 for a tunnel 954 yards in length, being at the rate of £118 

 per lineal yard. The size of both tunnels was 24 ft. wide in the 

 broadest part of the curve, 30 ft. including walls, and 25 ft. high in 

 the clear, or 30 ft. including the invert and arch at top, or 21 ft. above 

 the level of the rails ; the thickness of the brickwork varied from 2A 

 bricks to 4 bricks in thickness, and the invert three bricks. 



The second and third chapters explain the construction of the Ob- 

 servatory, the Transit Instrument, and the setting out the line ; the 

 fourth chapter the sinking of the trial shafts, by which it appears that 

 one of them was sank 35^ yards, and that the estimated cost of the 

 shaft, G feet in the clear with a 9-inch rim, was £3 8s. per yard down, 

 the price of 18s. per yard down being allowed for the sinking, and 

 £1G per rod for the brickwork, but in consequence of the large quan- 

 tity of water constantly coming into the shaft, the expense was in- 

 creased £50 for the lower 5 yards. The cost of sinking a similar shaft 

 for the Saltwood Tunnel, 25 yards, was £77 14s., or £3 2s. per yard 

 down. Mr. Simms carefully details the whole of the process in sink- 

 ing the shafts, illustrated with engravings, and also points out how the 

 various difficulties arising from water and sand were overcome. The 

 next chapter proceeds in like manner to show the cost and the pro- 

 gress of the works connected with the working shafts, they were 9 feet 

 in the clear with a 9-inch rim of brickwork, the cost of these by Mr. 

 Simms' calculation appears to be about £6 per yard down for the 

 Blechingley shafts in the weald clay, and £4 15s. for the Saltwood 

 shafts in the lower green sand. Afterwards the erection of the horse- 

 gins and plant connected therewith is detailed, which brings us to the 

 seventh and eighth chapters, on driving the heading. Here we have 

 some valuable statistical tables on the work done by horses in drawing 

 water up the shafts by horse-gins ; the following are the mean results 

 of the weight of water raised one foot high in a minute. 



Horses working three hours per diem, mean of 112 results, = 32,943 lb. 



Horses working (our hours per diem, mean of 4 results, = 37,151 lb. 



Horses working foiir-and-half hours per diem, mean of 1 2 results, = 27,056 lb. 



Horses working six hours per diem, mean of 212 results, = 24,360 lb. 



Horses working eight hours per diem, mean of 4 results, = 23,412 lb. 



In the determination of the value of horse power from the above results, 

 the three and six-hour experiments alone should be adopted. The other re- 

 sults were more or less objectionable, from a variety of causes over which 

 there could be no controul ; and are therefore of less practical value. 



By working at the maximum, lifting 36,000 lb. to 48,000 lb. per 

 day, the horses sank under the excessive fatigue, and 11 of them died. 

 The horses were of good quality and cost from £20 to £40 each. The 

 expense of horse labour, including boy to drive was about '2'id. per 

 ton lifted 100 feet high. 



The four chapters 9, 10, 11, and 12 bring us fairly into the con- 

 struction of the tunnel itself, here we must let Mr. Simms give the 

 explanation himself. 



The excavations for the tunnels at Blechingley and Saltwood were carried 

 on in a similar manner. One description of the general process will therefore 

 suffice ; with such occasional particulars of any peculiarity in the circum- 

 stances of either, as may have arisen in the course of those works. 



The work was commenced by removing some of the polings, or deal ends, 

 from behind the two top settings of the square timbering of the shafts; and 

 driving a narrow heading, about twelve feet long, at the top, and in the mid- 

 dle of the intended tunnel. Where the ground is good, and will stand with- 

 out much timbering, the top heading (as it is usually called) may have rather 

 large dimensions ; but must be limited in this respect where the ground is 

 loose or treacherous. The headings at Blechingley and Saltwood were suffi- 

 ciently high for a man to stand upright in, and about three feet in width. 

 In some of the headings at tlie former tunnel no poling hoards were required 

 in so small an excavation, but at the latter place they were in all cases ne- 

 cessary. No regular system of framing was used, but pieces of poling boards 

 were put up and secured in the best and most couvenient manner, wherever 

 the earth showed symptoms of falling in, but so arranged (where it was pos- 

 sible) as to form part of the subsequent roof of tlie excavation. Tlie top of 

 this heading was so much above tlie intended soffit of tlie arch of the tunnel, 

 as to admit the proposed thickness of the brickwork, and that of the crown 

 bars, packing and poling boards, together with the allowance of several inches 

 for the settlement of the timber which is certain to take place when more of 

 the excavation is made, and before the brickwork can be inserted to take the 

 weight, and relieve the bars of their burthen. J his allowance should never 

 be omitted, for when such settlement takes place, and no room has been 

 previously left for its occurrence, a part or the whole of the crown bars in 

 sinking occupy the position of the intended brickwork ; and therefore, in or- 

 der to insert a tunnel of the required dimensions, the bars and poling boards 

 must be raised to their proper level : whicli is only to be done piecemeal, 

 by removing the earth over each bar, and then raising them one at a time : 

 this involves considerable labour and care, and uo trifling expense. 



31* 



