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Roads and Engineering Construction, 97, 2, pp. 41-42, 44, 116, 1959-03-01
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Geology and transportation routes
Legget, R. F.
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by
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F.
A N A L Y Z E D
Reprinted from
Roads and Engineering Construction, Vol. 97, No. 2, FEBRUARY. I959
TECHNICAL PAPER
NO. 64
O F T H E
DIVISION
OF BUII.'DING
RESEARCH
OTTAWA
M A R C H , I 9 5 9
N R C 5 1 3 6
^3Lc t637
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Geology
and fransportation
Routes.
Thomas Jefferson, third President of the United States of America was probably the real founder of building research of North America. In keep-ing with his phenomenally wide in-terests, Jefferson had a lively appre-ciation of geology, even though this is perhaps not generally realized. Typical of his interests is this ex-tract from his Notes on Virginia, part of a discussion of the fossil shells found on "the eastern foot of the North mountain":
"But such deluges as these (one explanation of the fossils then cur-rent) will not account for the shells found in the higher lands. A second opinion has been enter-tained, which is, that in times an-terior to the records either of his-tory or tradition, the bed of the ocean, the principal residence of the shelled tribe, has, by some great convulsion of-nature, been heaved to the heights at which we now find shells and other marine animals. The favorers of this opinion do well to suppose the great events on which it rests to have taken place beyond all the eras of history; for within these, certainly, none such are to be found; and we may ven-ture to say farther, that no fact has taken place, either in our own days, or in the thousands of years recorded in history, which proves the existence of any natural agents, within or without the bowels of the earth, of forces sufficient to heave, to the height of fifteen thousand feet, such masses as the Andes." 1. Those who know Jefferson's writ-ings will recognize in this critical analysis of others' views the inquir-ing mind of the President, at work upon what was probably an un-familiar problem. It is to be noted that these words were written as early as 1781, four years before the first *A paper presented at the 9th Annual
Symposium on Geology as Applied to Highway Engiaeering, University of Virginia.
by Robert F. Legget
Director, Division of Building Reseorch, Nqfionol Reseqrch Council of Ccnqdq
publication of James Hutton's "Theory of the Earth".
Basically, this paper deals with the more general aspects of geologY in relation to transporation. Such gener-alizations can sometimes be helpful, if only in providing a background for more specific and more technical studies of particular problems.
H'isforicol Noles
There is, for example, an interest-ing tale to be told of the profound influence of geology upon the actual selection of early transportation routes. One can see that some of the oldest of the Roman roads followed the routes they did because of the local geology, and probably for no other reason. Think, for example, of the great road over the Julier Pass in the Alps which mounts to the sum-mit in fewer zigzags than the modern road and is even said to be less ex-posed to the wind with consequent less trouble in maintenance even to-d a y . 2 .
There is an old military canal in Canada, to give a more modern ex-ample, joining our capital city of Ot-tawa with Kingston at the foot of Lake Ontario. Built between 1826 and 1832, in its length of 130 miles it reflects quite remarkably the geology of the country it penetrates, one stretch (for example) being along the contact between the southern projection of the Pre-cambrian shield and the adjacent Palaeozoic rocks of the St. Lawrence Valley. This is the Rideau Canal. 3.
Inland waterways and pioneer high-ways had to be located in conformity with local geology and topography in' order to ensure suitable water levels for canals and a minimum of con-struction work for roads. Correspond-ingly, the first ports were not artifi-cially created but were centres of population which sprang up around naturally enclosed bodies of water, or at sheltered river mouths that provided natural harbours of refuge. The development, use and eventual
abandonment of the Roman port of Ostia due to the silting up of the mouth of the River Tiber is a vivid reminder, coming to us across two thousand years of history, of the fact that the great force of nature must be understood and controlled if the works of the engineer are to endure. 4.
Roilwcy Consfruelion
It was the coming of the railway in the early nineteenth century, as a world-wide means of swift and economical mass transport, that changed this simple picture of merely accepting the limitations imposed by geology in the locating of transporta-tion routes. With the spanning of the continents by railways, the routes they followed had to be, as closely as possible, the shortest distances be-tween the cities they joined. Great bridges and long tunnels were often the answer to the limitations imposed upon the railway pioneers bY the geology of the terrain they penetrated. This called for engineering and con-struction of a high order. [n this way came some of the most notable aP-plications of geology in engineering, many of them fortunately recorded in the annals of civil engineering, for our inspiration and guidance today.
Highwoy Locaiion rond Construciion
Only within the last two decades, however, has any comparable ad-vance been made in highway loca-tion and construcloca-tion. Highway en-gineers will know important roads that even today give one the im-pression that they are but little more than improved cowpaths. But the picture is changing rapidlY. Toll roads have had to meet standards as exacting in their way as those used for main line railways. In Canada, the Trans-Canada Highway, now ap-proaching completion as a fully paved road from Atlantic to Pacific, is being built to high standards, so similar to those in railway work that over the most difficult stretch of the
The flouting bridge at Kelowna, aroesing the Okanagan Lake, was the first of its kind in Canade, and only the second in North Amerioa. Unstable subsoil conditions precluded uhe use of heavy piers for a suspension span, and necessirtated the oonstruction of the rigid floating section. Altogether the bridge is 4584 ft. Iong.
route, in the heart of the Rocky Mountains, the new road is actually following the abandoned right-of-way of the Canadian Pacific Railway. This is in Rogers Pass, the old railway route having been given up when the Connaught Tunnel was opened in 1916. (See Roads and Engineering Construction, Sept., 1958, page 25). Tunnels cnd Bridges
Even tunnels are not unknown to the modern highway engineer. To-day, many Canadian and American cities are driving tunnels of no mean size to assist in solving their highway traffic problems. In other lands, too, the same thing is to be found. Re-cently when travelling in Norway, I was more than surprised to find what extensive hard-rock tunnels Nor-wegian engineers had had to excavate even on such a secondary road as that from Bergen to Nordheimsund. on the justly famous Hardanger Fjord.
Even this Scandinavian work, how-ever, fades almost to insignificance when compared with what French and Italian engineers are now ac-tively planning, this being the con-struction of the Mont Blanc vehicular tunnel. With test boring complete, construction will soon be underway (if, indeed it has not already started) with completion scheduled for the end of 1960. The tunnel will be 39. O32 feet long and will thus be the sixth longest in the world. Designed for two lines of traffic. it will be 27 ft. l0 in. wide and 22 ft. 8 in. high; naturally it will be equipped with artificial ventilation. It is antici-pated that it will carry as many as 350,000 cars and 1,500,000 people
every year. Passing directly under the Mont Blanc Massif, this great tunnel - when complete - is certain to add another significant chapter to the long record of the geology of tunnels.
Whether constructed for road, waterway or railway, or indeed for any other use, tunnels differ but little in conception or design. Consider, at the other extreme, a bridge re-cently completed in Canada which could not be visualized as serving anything but highway needs, even the character of which was determined by geology. This is the new crossing of Okanagan Lake in the interior of British Columbia, to give convenient access to the town of Kelowna. About 3,000 feet wide at this point, the lake has a bottom such that it gives most unsatisfactory conditions for bridge foundations. Accordingly, a floating reinforced concrete bridge was con-sidered, to consist of ten rigid pon-toons 200 ft. by 50 ft. and 15 ft. deep. (See Roads and Engineering Construction, July, 1958, page 39). The fact that the lake water level is controlled within a range of less than four feet made practicable a float-ing structure. The bridge had to be built, and so the floating structure was designed and is now in service. 5. The Kelowna bridge is not, of course, unique but just the most re-cent of a small but notable group of floating highway bridges which includes the well-known structure at Seattle over Lake Washington and the outstanding arched-floating bridge at Hobart. Tasmania.
Bridges and tunnels are not, how-ever, peculiar to highway engineering, interesting as they always are to the
student of the inter-relation of geology and engineering. Are there any as-pects of what we so loosely call en-gineering geology that are unique, or almost so, to highway design and construction? I submit that there are, and although they do not carry with them the dramatic intereSt of the foundations of great bridges, for ex-ample, they are equally important and so warrant careful study. They are all concerned with the links be-tween road structuie and the local terrain.
Airphoto I nferprel,cfion
In the first place, the location of new roads was one of the first civilian engineering tasks to which modern techniques of aerial photo-interpretation were applied. This branch of highway work is still a very special example of the use of this highly specialized procedure. (See Roads and Engineering Construction, Aug., 1958, page 58, and Nov., 1958, page 76). There is no need to discuss the methods now in use but it is salu-tory to recall that what started as a simple process of route delineation on unscaled photograps little more than a quarter of a century ago has now developed into a highly precise sur-veying tectmique. 6. The fact that such accuracy in aerial surveying is today possible may tend to obscure the vital necessity for ground recon-naisance and location as an essential supplement to even the best aerial photographic techniques.
Gr.'ound Surveys
Geology and lopography, it is true, can be studied on the grand scale
from the air, but, certainly for high-way location, patient examination of a selected route on the ground itself would appear to be a continuing nec-essity. Tractors and oversnow vehicles are taking groups of engineers and surveyors in to campsites along what will be one of the last (and one of the toughest) pioneer highways of North
America. This is the road that the Canadian Government has decided shall be built to link the extremity of the Alaska Highway, at Keno Hill, with the Arctic Coast at Tuktoyaktuk. It will have to penetrate the rugged and largely unexplored Yukon and Richardson Mountains. It will give access also to Aklavik, principal
set-tlement of northwestern Canada. which is being completely moved from one side of the great Mackenzie Delta to a much better site on the other. eastern side.
In connection with the survey for the new site for Aklavik, a study of aerial photographs of the great delta (an area of 5,000 square miles) had revealed what appeared to be an ideal site for the new town on al-luvial fans adjacent to the Richard-son Mountains. It was only as a result of test drilling in the permafrost, as a check on this selection, that it was found that the site was underlain by frozen silt and not by the sand and gravel that everyone had anticipated. 7. The search for the new site had to continue.
Muskeg ond Permqfrosl
Terrain conditions are not always what they appear to be at first sight. In northern Canada, for example, there are vast areas of muskeg, a word used to describe organic ter-rain. From the air, in summer time, and indeed even when viewed at a distance from the ground, muskeg can look quite beautiful-lush green in colour, compact and uniform in surface texture. Only when one has to traverse it,'does its real character begin to reveal itself-usually water-logged (with natural moisture con-tents up to 1,500 per cent), almost impossible to drain by ordinary methods, and frequently deriving what strength it has only from its surface mat of partially dried organic material.
Road construction over muskeg is therefore difficult work, requiring ac-curate foreknowledge of terrain con-ditions which is itself sometimes hard
;.:.tt"i
. ir I
With the Kelsh Plotter. terrain data derived from aerial photo-g'raphs are automatically reoonded
on punched pap€r tape. Disturbance of muskeg cover by pnssage of a heary tracked vcrhicle can caus€ road subsidence
to obtain, so treacherous can be even walking over some types of muskeg. Methods have been, and are being developed for road construction over such terrain. They need not be de-tailed here, but reference restricted to the fact that this somewhat unusual aspect of geology in highway con-struction has led to an entirely new branch of terrain investigation-the scientific study of muskeg. Dr. N. W.
llFl:ll j ';':i:l , .': :1.... . ii; ,: : , .: ,,1 ,, , '
flere, thawed soils are rnoving down
slope from beneath road fill about
one and one half miles fr.orn Uranium
City in northern Saskatchewan.
Radforth of McMaster University, Hamilton, Ontario, has been a pioneer in this field of palaeovegetography but even his good work is over-shadowed by what he recently saw in the U.S.S.R.. where he visited the Russian peat research institute which has a research staff of 400 and 1.600 students in residence.
'
Another a.spect of muskeg of vital importance to the highway engineer in northern regions is the protective effect which shallow muskeg deposits have upon permanently frozen ground, the "permafrost" which is such a problem in Alaska, in northern
Canada, in the U.S.S.R. and in Manchuria. (See Roads and Engi-neering Construction, Jan., 1959). If the ground beneath the muskeg is flne-grained soil, and especially so if it is silt, removal of the muskeg-the "obvious" procedure in road build-ing-can have permanently damaging effects. The muSkeg restricts the depth to which thawing will take place by the end of each summer
of the area covered. Soil moisture conditions are similarly affected, in some cases very seriously. As road building continues to spread over this continent, it is probable that these effects upon terrain will have to be given much more consideration than has been the case up to riow. For approximately 2 per cent of the total land area of the United States is al-ready taken up by road surfaces, not
(thus controlling the depth of what is called the "active layer"). If it is removed, soil previously frozen solid can quickly take on the consistency of soup, with results that can readily be imagined.
This is, perhaps, the most vivid example of the effect which highway construction can have upon the ter-rain which it traverses, and this is surely one of the most important inter-relations between geology and road engineering. Troubles with per-mafrost are just a reminder that the building of a road can have a perma-nent effect upon the thermal regime
An example of a large slrrmp caused
by thawing of an ice wedge on
finely-texturcd soil in a borr:ow pi't near
Inuvik, N.W.T., new location of
Ak-lavik. Such conditions add to the
difficulties of construction in
perma-frost areas.
all paved it is true, but different enough from the natural terrain to affect profoundly the subsurface regime.
Inportonce of DroincAe
There are locations, naturally, where subsurface conditions have to be deliberately changed in order to permit road construction to proceed. Drainage is the dominant require-ment in this respect. The modern use of sand drains in highway work has been a notable advance-although I find myself wondering if it really is such a modern advance when I recall
Typical of the rugged terrain found thr:oughout much orf British C-o,lumbia is this rock-s,trewn seoLi,on rin the Fraser Cranyon. Construetion o,f the Trans-Canada llighway past this point required the rernoval of ,about half of uhe slide in the foreground, and necessitated tunneling through the
blu{f overhanging the river.
the record I recently came across of the use of sand drains in building foundation work in France as early as
1830. Last summer I was privileged to see what must be one of the most extensive installations of highway sand drains. This is in Finland. The construction of the first divided land highway in this country, between Helsinki and the ancient capital city of Turku, has necessitated more than 500,000 metres of sand drains being installed over two relatively short stretches of the route where the road must traverse deposits of unusually sensitive marine clay.
"ln Silu" Use of Soil
There is yet another aspect of ter-rain study that deserves brief men-tion, this being the use ir? ,sifr, of the soil over which a highway is to be located as road building material. Some friends were rnildly amused when I included a reference to a pioneer Australian experiment of burning clay in situ-in a publication of 1939. 8. Earlier confidence has been justified by recent accounts of quite extensive experimental work in the treatment of "black cotton" soils, one of the most extensive and trouble-some soil groups of the tropical world, by burning it in situ and using the resulting hard material, when broken, as a coarse aggregate in the road bed.
9. We are so profligate in the use of the road-building material, which we have generally in such abundance in North America, that it is only the occasional reference to a shortage of sand and gravel (heard even in parts of Canada) that invites attention to the possibility that the day may come when "manufactured" road building materials may become a widespread necessity.
Geology qnd Moinlenqnce
Not only in the design and con-struction of highways does the local terrain play a dominant role in high-way work, leading to unique applica-tions of geological study, but it is significant also in road maintenance, the least publicised, the least exciting and yet in some respects the most important part of highway engineer-ing. And local geology is still of pro-found significance.
Geologic influence upon roadbed maintenance and drainage is obviously important. Less obvious is the sig-nificance of the geology of the ter-rain around the highway. In areas of incipient landslides, for example, local geology must be regularly ob-served. Similarly in precipitously rocky areas, it will often be necessary to study local geological features if maintenance troubles can include rock falls. Signs by the roadside indicating
the possibility of danger frorn rock falls may sometimes be thought to be a reflection upon the adequacy of geological studies in road main-tenance, and yet there are many loca-tions where certain protection from rock falls could be achieved only at prohibitive cost. There is at least one location in North America where highway practice has had to follow railroad practice, an electrically ac-tuated warning fence paralleling a particularly vulnerable stretch of road. In some mountainous regions there are hazards even worse than rock falls to be guarded against in road maintenance. Avalanches sweeping on to highways in areas of high snow-fall can exact terrible tolls of life and in property damage. Fortunately, there are few areas in North America where avalanche control work is a necessity but there are some. Notable work has been done in some western states. Canada now faces this problem quite critically since the finally selected route for the Trans-Canada highway through the Rockies goes through one of the very worst pos-sible areas for avalanches. A young Swiss-trained member of our own staff is now stationed at Glacier in the heart of the mountains. at work as research engineer with the Depart-ment of Public Works, (responsible for building the road), applying in
Canada the accumutated experience of Switzerland, a country pre-eminent in snow and ice research work. In one area of that lovely country, avalanche protective measures include even designing masonry buildings with wedge-shaped ends facing the avalanche slopes.
Having boldly, and without ques-tion, included snow as a geological agent I should bring this brief review to a speedy close before making further ventures into debatable ter-ritory.
Reciprocol Relciionships
One cannot mention a place with so romantic a name as Glacier with-out a final reminder that the inter-relation of geology and transportation routes is a reciprocal arrangement. Well over a century ago William Smith, the "Father of British Geology", gained his remarkable knowledge of the strata of Britain by his work as a builder of canals. Many were the early geological papers that described geology of the country traversed by pioneer railway lines. In more recent years, the same has been true of pioneer roads, a notable ex-ample being Charles Denny's paper
the Alcan Hig[way. 10. Just as long on the geology of the country along as there are new roads to be built, whether in unknown country or in the heart of the continent, if the highway engineer uses geology for his good purposes and remembers also that his works may reveal previously unseen exposures of the soils and of the rocks, so will the sum of human knowledge continue to advance hand in hand with the progress of the spreading network of transportation routes covering this vast continent.
REFERENCES
l. Part of the answer to Query VI: see pp. 199-2OO of "The Life & Selected Writings of Jefferson" ed. by Koch & Peden, 1944. 2. "Engineering" by A. P. Gest, in
"Our Debt to Greece & Rome" series Longmans Green & Co.,
1 9 3 0 , p . l 3 l .
3. "Rideau Wdterway" by R. F. Legget, Univ. of Toronto Press, 1 9 5 5 .
4. "The Development of Dock & Harbour Engineering" by Sir Cyril Kirkpatrick Vernon
Har-court Lecture, Inst. C. E. (London) 1926.
5. "Canada Builds Floating Bridge", Engineering News-Record, vol. 159 p. 46-5O,21 November, 1957. 6. See for example: "The Appraisal
of Terrain Conditions for High-ways Engineering Purposes", Bul-letin No. 13, Highway Research Board, Washington, 1948. 7. "Rapid Disintegration of Alluvial
Fan Material near Aklavik, N.W.T." by R. F. Legget and R. J. E. Brown (being submitted to
c.s.A.).
8. "Geology and Engineering", by R. F. Irgget, McGraw-Hill Book C o . I n c . , 1 9 3 9 ( s e e p . 2 5 4 ) . 9. "Airfield Construction on
Over-seas Soils: Part II, Tropical Black Clays" by K. E. Clarke, Proc. Inst. C.E. (London), Vol. 8 pp. 223-230, Nov., 1937.
10. "Late Quaternary Geology and Frost Phenomena along Alaska Highway, Northern British Col-umbia and South-eastern Yukon" by C. S. Denny, Bull G.S.A., Vol. 63 pp. 883-921, Sept., 1952.
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