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Muskeg access: the slipe - haul method
MUSNl6 ACCEdS
I
ipe
-
Hau
method
Iwtrad~etiee conditions in northern Canada and Technique 06 Te~eaiw Seisc~iom
Northern organic terrain Qmus-
keg) has come to be recognized as
the most difficult medium in Cam-
ada to traverse. I n many eases it is not simply a transitory problem f o r engineering implementatis~a, it is a constant limiting factor to progress for northern development. It adds millions of dollars as a coat barrier t o oil explor.atiopn, Bfeters mining in general, controls eomrnu- nicertion and community develop- ment and year by year becomes in-
creasingly significant in the for- estry industry.
The situation is important in aev- era% countries but in none is it of such fundamental signif ieance as in Canada and the U.S.S.R. Uni-
northern Britain. It is designed t o
apply where haulage sf large ton- nage over virgin terrain is con- templated.
Wherever the system is to be used, a basic first step requires consideration of the great diversity of conditions and combinations of fidd circumstances that organic terrain is known to portray ( I ) .
RQUEQ Seleetiope
The siipe-haul operation is n function of two major factors ; one
is terrain analysis, characterization and selection, the other is mech- anical adaptation. Both must be ad- justed to each other before opera- tions proceed.
For convenience of estimating physical characteristics in the pro- posed line of traverse and in order to provide a baais f o r eomplatation ila estimating the economics sf travel, t h e authors have arbitrarily chosen a unit of one hundred miles as the working dimension of r ~ r r t e length. In practice it is frequenGy the case that route length will be several to many times this length, but i t may be less. Before position for the haulage route is fically de- fined, t h i s mstter
must
be earef uEly camsidered. Total route length or the positions of the iermfnals may bear on the positioning of the hucdred-mile intervale used for detailed analysis.versaily, the basis of the difiieultg~ is the inherent nature of organic terrain.
Passage over muskeg by foot
duri"g the requires Powered 381'p@1 with &iyer's cab shewing sobla over ewgiwe hood, and winch-
grdimiaaarg plalalling involving ing d ~ v i e c . Note wheels are not powered. E ~ a ~ g l y for B P O R I ~ O ~ ~ i s applied directty
route survey. Travsrsability by te the sable.
vehicle in the same period caw
b
guaranteed only when a programme sf aerial survey of a special and highly critical nature has been ap- plied wherever the distances csn- template6 exceed n mile. Even when the route proposed is shorter than this, failure car, be expected where a suitable vehicle is lacking and the mechanics of over-muskegtl.sve.1 ztre not considelsed.
Becaaase of the pressing need to provide operating security in ac- cessibility problems, the authors have set down what .they consider
t o be the primary t e r x s of refer- ence prescribing f o r over-muskeg travei. The system has been design- ated the Slipe-Haul method ( c f . Figs. 1 - 4 ) . It is new and is based on field knowledge and tested mechanics pertinent to comparative
Using s i r photos, the shorteet
distance between the two termini
should f i r s t be inspected. It is in- evitable because of economic and engineering requirements that this line will have to be modified. This
leads to the process of proctarinp the best choice of terrain that will give the shortest possible route to replace t k ~ t which would have co- incided with the straight line join-
ing the termini. It is easy t o realize that extension sf route length aver the theoretically ideal straight line will not be an embarrassment
to the operation if the longer
modified route can he traversed in shorter time and with greater ef- fectiveness a t less cost.
It is likely that air photo records provided f o r the work wiiH have been taken a t aititudea exceeding
16,0680 feet. Air form features, t h e first data, that an& be secured, will therefore fall into categories already defined by one of t h e au- thors as ""clrmzttoid, stipploicf, marbloid, tsrrazzoid and reticuloid" (4). If the prcposed route Is a
short one, a matter of say, ten
to f i f t y miles, i t may be the case that only one a i r form is encount- e red* W h a ~ e v e r t h e situation, %is form category muat he provided.
The next step is 60 resolve the air form pattern into its various characterietics t h a t csaln he lander-
stood in terms of lour altitude and eventually prorrnd level. This can be achieved by applying the tech- niques descl-ibad in Defeece Re- search Board Publication DR 95
(3).
Consideration of the f i n d d a t s
will lead lo the detailed position- ing of the traverse. At this time the purpose f o r which the route is required, the laateare of the terrain and t h e kind and availability of haulage equipment wiIB become critical factrrrr in route deaigna- tiora.
P#Iuch is nclx known about the
Iimitatic~ns of vehicle performance cn organic terrain. The slipe-hacl
-method is hnsed on mecknniesl
principles t h a t apply most appro- priately f a r grc~und farms chame- terizing organic t e r ~ a i n properties.
The method facilitates shortening
o f the line of traverse as rnr~ch as from 25 to 50 piercent of a routs that would have-to be used if other mechanical principle8 are utilized. Ae s feature of the route se- lection process, each hilrtdreci-mile unit of route is divided into hun- dredths, and each of'tEse latter in- to quarters. Ronte characten-iza- tion f o r each quarter is then pros.-
ided according t o the following
headings :
Air Pnrix, route devistion factor,
vegetation hindrance, proximity to
aggregate, organic terrain depth, terrain bearing strength, sub-sur- face ice interference, water rela- tions, terrain roughness, factor and availability of corduroy.
Mechanical Adaptatien
0th-si- con iide~.:ttions of o p w s t i n g technique relate to meehanic~l principles.
The ability to apply tractivs ef- fort to the surface of the organic terrain ifr in a11 cases limited by the shear strength
-
of the oraanie-
mat, Since this varies so markedly in.;hear streagfh. depending en the ground fcrrn, in order t h a t eontinu- ed travel can be assumed, an ak- termtive means raf producing trsc- tire effort must be supplied as
methods normaIly applied ore sub-
ject 90 unfortunate limitations.
The sIipa-had method is achieved by the laying of wire rope on the surface with breaking strain suit- ably related fa the loads to be car- ried. Organic terrain has the p ~ -
tentiaily of buoyancy eqrlal
at
Ieast to that of free water and sometimes greeter. In order to take
advantage of this situation, the
vehicle, whether it is in tractor form (Figs. 2, 3 ) to supply tractive e f f o ~ e , o r ir, conveyor form (Fig.
41, should h a ~ 8 a bearing pressure of not more than a pound a d a half to the square inch when on the mat surface.
It
shou%d be com- pletely buoyrantiin free wakr(Fig, 3 ) .
In order to cross intermittent mineral -axposurw it is also aeces- serg that track eonetructio;.a be rapped enough to wfthsbnd the severe strains imposed.
Ia
the case of the conveyor, ap-propriate wheeled or track units ehou'ld be built into the huEl and a t the same time protrude below the base of the structure to eliminate high friction (Figs. 1, 4).
T p a e t ~ r Requlremmnts for Load Towlwg a~sd Tcw-lime E*blishmassa~t.
ICnowledge of the field suggests %ha% track area must be su3plied to appropriatehy cornform to the re- quirement of a pound and
a
halfper square inch 0% ground pres- sure. The suggestion is that to overcome limiting c m d i t i o n ~
BW
the terrain. the track should be driven from the front, not the rear driving sprocket ( 5 ) . Lower idlersshould ht. arranged in such fashion that the lower line of track should show $light curvature with the track as .a whole t h u ~ sirnu%atimp in some respects a large wheel com- bined with track flexibility. The latter afford8 lower power con- sumption (cf. Fig. 3 ) .
Engine gearing must be housed in a fully b u o y ~ n t hull.
An essential feature of the trae- tor is a capstan-type winch co- ordinated in ail gears to haul on %he cable exactly at track EIP)B&
(Fig. 2 ) . It must also be provided that the cable is ejected
at
the same speed as i t is pieked up during oger8tions. An exception t o thiswill be in conditions of short haul
when the cable may remain aboard.
Laad Cargyimg U ~ i t s (SIiped Clperatimg ew E&o$Plishcd Taw-Miwe,
No tractor
is
required f o r tran- sportation of loads once the tow- line is in position for the length ofthe selected route. Movemetmt of load is achieved by one to several conveyors generally conforming to the foIlaws.4ng principles and sup-
pestians ( c f . Pigs. I, 4).
A sBfpe having csmp%ete buoyancy is, relsztion to its total dead weight (include that af the load) k link- ed to the line. Wheel or track mech- =ism protruding below the slipe and ~ e t into it a r e stee~-able by the movement of the load in arrange-
ment with a capstan-type winch
ealready referred to for the tractor.
The winch is power driven by
an
ernpine carried on the sIipe. The System in Qperetigsa
The tractor lays two lines over the selected route. Its directly at- bched slipe (there may
be
morethan one) carries the Isad of wire and other equipment associated with taw-line establishment. One line links the field origin with the destination. The second is utilized for the return journey. Anchors for the line are inserted a t the points of origin and destination. Thus a circuit i s established with a kr,own tractive effort and a known Isuoywncy factor.
I t should be emphasized that neither line "will be necessarily straight due to the peculiarities of the terrain. However, the tractor.
o r the power-driven slipes are
steered independently. Thus an- chorage a t intermediate positions on the towline is avoided.
When considerable tonnage ha8 been delivered in the coarse of the advancing season, segments gf the terrsin will deteriorate and Icseie their initial mat qualities. Rere the buoyancy factor gains promin- ence over tractive effort which de- creases. In the majority of ~ase8, this may facilitate, not hindm kan- sportation.
Subsurface lee conditions and topographic change in the mineral suh-layer may however hecome more prominent for some cases ( 2 ) . Generally it should be predict- ed that the trdfieabflity situation should improve, not deteriorate. This cmtsasts with the 'esult to he expected in tractor train oger- ation, the only alternative to the slipe-haul eystem.
ossd traveBl1rap om Q mLle amd mew ~mady
I t is also reasowable to sagpeat that this method of transport can be used in winter if the cablea
can
be kept from freezing into the ground when frset conditions ariee, Thus summer routes may be used for winter transport possibilitfee, even by wheeled vehicles-
Other attractive features perti- newt to the slipe-haul system that only one combined-season route is required, aninimutra s-oute devia- tic11 is achieved, least time for total operational aspects is required, and costs for all phases including main- tenance are substantially reduced.
1. Rsdfouth, NOW. 1952. The Sug- gested CTlassiffcation of Muskeg for the Engineer. The Engineer- ing Journal, November, 1962. 2. Radfsrth, N.W. 1964. Palaeo-
botanicall Nethod in the Predic- tion sf Sub-surfsee Bummer lee Conditions in Northern Organic Terrain. Transactions of the
BoyaI Society of Canada, Vol.
WLVIII, Series 111, Section
V.
3. Badforth. N. W. 1956. Organic Terrain Organization from the Air (Altitudes less than 1,880 feet) Handbook No. 1, Defence Besesreh Board, DR No. 9%. 4. Radforth, N. W, 1956. The Ap-
plication of Aerial Survey over Organic Terrain. Roads and En- gineering Construction, Augu~te, 1956.
5. Badforth, N.W. 1957. ProlbEeagta of Access as Pertaining to Off- the-Road Vehicles. Proceeding8 of the Third N u ~ k e g Beseareh Conference, Twhnica1 Memoran- dum No. 47, Natfsne! Research Council, Ott~wta.
