The Royal Engineers Journal
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THE ROYAL ENGINEERS JOURNAL. Vol. XV. No. 4. APRIL, 1912. OONTENTS. 1. The Holding Power of Earth in Connection with Anchorages for Military Bridges. By Capt. C. E. P. SANKEY, R.E. (With Plate) 209 2. Improvised Drawbridge. By Major C. S. WILSON, R.E. 21z 3. Notes on the Panama Canal. By Lieut. R. A. OWEN, R.E. (With Plaits) 219 4. Historical Documents of Major-General Sir J. T. Jones, Bart., K.C.B., R.E. (continued) .. .. ... ... 229 5. A Lady's Experiences in the Great Siege of Gibraltar (1779-83) (continued) ... 245 6. Transcripts:-" Nest" (or " Recess ") Fire Trenches. (From the Injenerni urnal). (With Plate) ... ... ... ... 263 Sand-Bags and their Application during the Russo-Japanese War. (Trans- lated from the In/enerni Jurnal by Lt.-Col. F. E. G. SKEY, R.E.)... 271 7. Notice of Magazine ... ... .... 277 8. Correspondencee:-Tactical Reconnaissance. By Capt. B. BORRADAILE, R.E. 279 INSTITUTION OF RE OFFICE COPY DO NOT REMOVE /,cJ) I _ GUARANTEED: Immunity from repairs. mooth on both sides. Roofs Trnelle Strength, 5,781 Ibs. covered with "Eternit" orushing Force, 8,281 Ibs. w h about 2 Ib Pr Square Inch and LI T T iles weigh about 22 lbs. Per uare Inch and per square yard. always increasing with aS. ON THE ADMIRALTY AND WAR OFFICE LISTS. \ For Diagonal or Honeycomb Style of Roofing. Colours: Grey, Blue and Red. Stock Size, 151" by 158\ "ETERNIT"ROOF TILES (HIatschek's Oiginal Patent). G. R. SPEAKER & CO., 29, MINCING LANE, LONDON, E.C. ENGINEERS Less than one-half the cost of / nd Broseley Tiles. SURVEYORS Prompt delivery. -- are earnestly warned not to confound " Eternit" Speedy fixing. WEATHER Tile with so-called Asbestos Slates varying in quality, thick- No breakages. P OF nes andcolour,advertled under fancy brands. Eternlt " endures not for an age, but for all time." G. E. CARRINGTON, For many years Master Tailor, Royal Engineers, TAILOR &MILITARY OUTFITTER, 53, HIGH STREET, OLD BROMPTON, KENT, And at CARLTON HOUSE, REGENT STREET, near Waterloo Place, S.W. HOURS OF BUI8NE88:- Old Brempton, 8.30 to 7.30; Saturdays, 8.30 to 2. Carlton House, 11 to 6; 8aturdays, 11 to 1. 1 Telephone No.-East 3. Telegraphic Address:-" Constructive Ironworks, London." MATTW. T. SHAW & CO., Ltd., MILLWALL, LONDON, E. CONSTRUCTIONAL STEELWORK, FRAMED BUILDINGS, BRIDGES, ROOFS, Etc. Large Stocks of Joists, Channels, Angles, Tees, Flats, Plates, Chequers, Rounds, Squares, Rivets, Bolts, Galvanized Sheets, etc., etc. VERY PROMPT DELIVERIES GUARANTEED. ADVERTISEMENTS. BY ROYAL m* WARRANT. THE GOLDSMITHS & SILVERSMITHS COMPANY, Ltd. Famous the World over for DESIGN. QUALITY. VALUE. V CUPS, B OWLS, AND TROPHIES IN '- GOLD, SOLID SILVER, SILVER . GILT, SUITABLE FOR PRIZES. MODELS AND STATUETTES PREPARED FROM PHOTOGRAPHS OR LIFE. 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Mr. J. A. 0. ALLEN, Aberdeen, Architect. REINFORCEMENTS FOR CONCRETE. EXPANDED STEEL SHEETS AND BARS FOR Foundations, Walls, Floors, Roofs, Bridges, Reservoirs, Sewers, Conduits, Hoppers, Silos, etc. LATHINGS FOR PLASTERWORK. EXPANDED METAL LATHINGS FOR Exterior Walls, Ceilings, Partitions, Steelwork-Encasings, etc. EXPANDED METAL SHEETS For use in Fencing, Divisions, Guards, Ventilators, Lockers, Baskets, etc. PLEASE WRITE FOR ILLUSTRATED HANDBOOK AND PRICE LIST. THE EXPANDED METAL CO, LTD. Head Office: YORK MANSION, YORK ST., WESTMINSTER, S.W. Telegrams:-" DISTEND, LONDON." Telephones:- Gerrard 819; Victoria 1514. Works: Stranton Works, West Hartlepool. Telephones 94 & 245. Telegrams: " Expansion, West Hartlepool." I CONTENTS. PAG.. I. THE HOLDING POWER OF EARTH IN CONNECTION WIIIT ANCHORAGES FOR MILITARY BRIDGES. By Capt. C. E. P. Sankey, R.E. (WitlA I'late) ... 209 2. IMPROVISED DRAWBIRIDGE. By Major C. S. Wilson, R.l'. ... .. ... 21 3. NOTES ON TIlE PANAMA CANAL. By Lieut. R. A. Owen, R.E. (Wlilh f'irtes) ... 219 4. HISTORICAL DOCUMENTS OF MAJOR-GENERAL SIR J. T. JONES, BARTI., I.C.I., R.E. (continued) ... ..... ... ... ... .. .... 229 5. A LADY'S EXPERIENCES IN IHE GREAT SIEGE OF GIBRALTAR (1779-S3) (continued) ... ... ... ... ... ... ... ... ... ... 245 6. TRANSCRIPTS:- "Nest" (or " Recess") Fire Trenches. (Fromll the Iji/eer,ni .,ritrial). (IVillh P/ate) ... ... ... ... ... ... ... ...... 26 Sand-Bags and their Application dining the Russo-Japanese \War. (Translated firom the IZjeinerni.yiri ataly Lt.-Col. F. E. G. Skey, R.E.) ... ... 271 7. NOTICE OF MAGAZINE :- A'ivista di Artigihi'in c Genio. By Col. Silr Edwd. T1. Thackeray, v.c., K.C.B., late R.E. ....... .. ... ... ..... 277 S. CORRESPONDENCE :- Tactical Reconnaissance. By Capt. 1B. Borradaile, R.E. .. 279 Au/lhors aloneeartesp onsi'ble ti thl/e stnaementcs nmade ant tlhe opirnions e.vpessed in their papers. 1912.] 209 TIIE HOLDIVG POWER OF EARTH IN CONNECTIONV WITH ANCHORAGES FOR MILITARY BRIDGES. By CAPT. C. E. P. SANKEY, R.E. ANCHORAGES buried in the earth have to be used in various military bridges, notably suspension, tension, and cantilever bridges. The subject is an important one, but it would almost seem that its importance has been under-estimated, as it is more often than not the case when a bridge of any of these types fails, to find that the failure is due to the dragging of the anchorage; an examination of the figures on which the calculations for such anchorages are based will therefore not be without interest. The pull that may safely be placed on an anchor beam in the earth depends upon a variety of factors, one of the most important being the holding power of the earth itself. This factor is characterised by not being easily measured directly, owing to the magnitude of the stresses involved, as any but full-size experiments are most unsatis- factory, and by not being readily calculable by any formula in common use. It is therefore necessary to have recourse to tables of accepted results or their equivalent; the tables one naturally turns to, are the two in Instruclion in Mlilitary Engineering, Part III., para. 34 and 35. The former gives the relative holding power of various soils, and the latter some definite values for one particular nature of earth, taken as the standard for the purposes of the first table. Considering the latter table first, it will be seen that it gives the ultimate resistance in lbs. per square foot, to a pull on a buried anchor beam, the values varying with the mean depth of the anchorage and with the inclination of the pull. In order to appreciate more distinctly the nature of this table, and to discover the basis on which it is founded, the first step seems to be to plot graphically the values given, with the depths as ordinates and the resistances per square foot as abscissae. Anyone who has plotted this table will have been struck by two things, its suspicious degree of accuracy, the ultimate resistance to a vertical pull on an anchor whose mean depth is 5' being given to five significant figures, and also the fact that the chart so obtained takes such a curious form that one is led to doubt even the approximate accuracy of some of the values. As a next step, it is desirable to compare this table with some other authority, but here, at all events as far as the author is concerned, a difficulty arises. He has not been able to find any other table of a 2I0 THE ROYAL ENGINEERS JOURNAL. [APRIL. similar nature, probably due to the fact that such results have an interest almost entirely confined to improvised or military bridges, the anchoring arrangements in permanent structures owing their security to very different considerations. It is therefore necessary to trace the origin of these tables, to see if anything can there be found to throw light upon these anomalies. These tables appeared, in their identical form, in one of the series of very- valuable articles contributed by Lieut. (now Major-General Sir Thomas) Fraser, to the Professional Papers of the Corps of Royal Engineers. The paper in question is entitled " Experiments on the Holding Power of Earth, and the Strength of Materials," and formed No. VIII. of Volume XXII. The present author has no intention of criticising the experiments there recorded, but it is possible to divide any paper of this nature into two portions, the results of the actual experiments, and the deductions made therefrom. It is therefore proposed to accept the results obtained as correct, within the limits of accuracy appertaining to the subject and the apparatus, and to limit the investigation to the laws deduced from them. Table I., in the Paper referred to, gives the results of the experi- ments ; these were 36 in number, and varied as regards soil, inclination of pull, depth, extent, surface, and shape of the anchor. Table II., reproduced in Instruction in Military zEngineering, Part III., para. 34, gives the relative holding power of different soils, and Table III., reproduced in para. 35, gives definite values for loam. In Table III., certain values are marked with an asterisk to show that they have been derived from calculation, and are not experimental values; these may obviously be removed for the present purpose, and the table will then appear as follows :- Vert.