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<br />Assembly pole is crane-placed on foundation anchor-6olts.
<br />Crew guides pole into place and prepares to "bolt-down"
<br />grad� by a 65-ton winch. A Chantillon gauge was used
<br />to measure increment of loads. Ground deflections were
<br />rccorded and �raphs of defiection versus load were
<br />plottcd. �From these graphs, the optimum required
<br />passi�•c-resistance dcsign valucs wcre established based
<br />on the assumptian that the yielding of poles at b ound
<br />linc tuncicr full loadJ should not exceed 1/a in.
<br />An additional acivantagc was gained from these prc-
<br />!iminar}' tests�inder-compact fill around the test pole
<br />with bad sub-soil helpe�l to cxtend the pole yield-paint
<br />tu much higher loads than wcre cxpected. Therefore,
<br />in thc foundation dcsibn, as an additional factor af
<br />safcty a�ainst ground movcmcnt, a hard, br�ken stone
<br />collar at �round le��el was specifieci for all poles.
<br />Thc linc had to be energized in March, 1967. The
<br />I'oundation construction began in late S�ptember, 1966,
<br />and by micl-Novcmbcr only i"s foundations were
<br />finishcd.
<br />Work methods yose problems
<br />The methocl of construction consisted of impact-
<br />driving a stecl casing [comprised of two or three sections
<br />of various lengths) into tt�e bround to prevent cave-in.
<br />The soil within thc; casing was excavated at intervals
<br />during the clriving. Thcn the reinforcing cage and
<br />anchor bolt assembly were set in place, and concrete
<br />pourr..d. The first 10 to 15 ft of casing were usually
<br />driven into the ground without too much effort. The
<br />next 10 ft were, most of ihe time, very hard to get in.
<br />�th a 3,SOQ-lb impact-hammer dropping 8 ft, one
<br />blow could drive the casing down only �/a in.—the skin
<br />frietion outside of the 25-ft casing was tremendous.
<br />Alternate methods o£ construction were explored-
<br />pressure groutiing, Vibro-Hammer, sonic hammer, and
<br />steel sheet piling.
<br />Pressure grouting of an oversized hole outside of a
<br />plain steel casing was the second altemate method tried.
<br />Theoretically, this method should have done the job;
<br />$8
<br />a s enl fo�ur fo -
<br />howeyer after seven�'king d y, y undations
<br />were stabilized. The: failure of grout material to show
<br />at the ground line, indicated an unsatisfactar� condition. -
<br />One of ths foundations was excavated around t�e casing -
<br />ta 10 ft below grade, and no grout was found azound
<br />the casing. In this case the equipment was �ot capable
<br />of spreading the grout.
<br />The use of a Vibro Hammer, which is powered by �
<br />two 50-hp motors and vibrates 1,050 cycles per min,
<br />was attempted. It sent out mueh stronger shoek waves ,
<br />than fhe impact hammer.
<br />Upon considering the use and availability of a sonic
<br />hamm�r, it was decided not to try it because th� pro-
<br />cedure would b� an expensive one for the small number
<br />of foundations invol �ed. Also, it would have #aken tw�
<br />weeks—which could not be spared—to fahricate a
<br />"follower" as go-between-hardware between hammer
<br />and casing.
<br />The use of steel sheet-piling was suggested as a_ re-
<br />placement for the plain steel casing to reduce the skin
<br />friction. This idea was not used beca�se bent web steel
<br />piling was not available for early delivery; also, because
<br />driving steel sheet-pi':ing requires much time and hig�y
<br />specialized labor.
<br />Stabilization with lean concret�e answers proble�s
<br />Finally, it was decided to construct the pole founda-
<br />tions by stabilizing the foundation shafts with Iean con-
<br />crete—the job was completed on time using this
<br />method. ihe procedure was as follows:
<br />1] Thc earth, arou�d the foundation saaft was excavated
<br />with a bucket, down to 2/a of the depth of ihe fountla-
<br />tions, less 5 ft.
<br />2] �it the bottor.-� of this excavation, two air-operated
<br />tampers compacted the soil around the casing.
<br />3] The excavated hole was then filled with lean �oncrete
<br />or broken stone.
<br />With this method, it was certain that at least 2/3 of the
<br />shaft foundation �vas embedded with solid material.
<br />Tho�ghts of a Monday-morning quarterback
<br />In future applications the following refinements
<br />would be considered:
<br />❑ Most of the poles �ould be designed to "strength"
<br />criteria, but all poles above 30 deg would be designed
<br />to an additional "rigidity" requirement to reduce de-
<br />flection and improve appearance i�nder normal loading
<br />conditions.
<br />❑ All poles would be fabricated of Type 304 stainless-
<br />clad steel plate to avoid taking the li�ne nut of service
<br />for painting.
<br />❑ The base plate would be redesigned. Its thick�ess
<br />can be rerluced by welding numerous stiffer plates
<br />around the pole base between pole body and base plate.
<br />❑ All the welds connecting take-off plates and arms
<br />would be designed to develop the full strsngth of the :
<br />take-off plate to reduce the possibility of any fatigue
<br />failure.
<br />❑ The same round shaft foundation design would be
<br />used again for all types of soils except in s�aimps.
<br />Bent-web steel-sheet piling, rather tha.B. round casings,
<br />would be ciriven ahead of the excavaiinn to prevent
<br />cave-in where necessary. This i� the ' best methpd of
<br />construction to insure c1�se contact- of the foundation
<br />structure with the-surrounding soil.
<br />Electrical World, J�ne 26, 1967
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<br />Test transrnission line with 446 polzs shows G'
<br />full-length treatment cut sapwood decay to 5.A�%;
<br />butt protection proved less effectiue
<br />'; Strength characteristi'cs, shape, size and availability of r
<br />; lodgepole pine make it suitable �or use in rural electric
<br />' and telephone lin�es. Its susceptibility to decay, �owever, "
<br />' and the availability of decay-resistant western red cedar
<br />have retarded its use for these purpos�s. �
<br />, Full-length treatment with a recognized preservative `�'
<br />improves lodgepole pine's decay resistance, making it ��
<br />better thau that of western red cedar. After 15 years
<br />service, t�sts show, full-length Osmose-treated pnles re- ��� `�
<br />tain original color, appearance, and lustre, and show `����
<br />almost no evidence of decay.. �`�����_
<br />���b�
<br />The sub-alpine eastern slope of the Rocky Mountains �°�' �;� _
<br />constitutes a considerable portion of Alberta's forested
<br />area. Because of repeated large-scale fires over much of
<br />this land, a pioneer species, lodgepole pine [Pinus con-
<br />torta var. latifolia] is th� principal forest cover. High
<br />altitude, and the inheren� nature of the species, stimu-
<br />lates growth to a size which makes it ideal for poles,
<br />piling, mine props, and fence posts.
<br />It is apparent frum the size of the timber that poles
<br />can be produced in the medium to smaller sizes �[short
<br />poles] in quantity and that such poles should, theoreti-
<br />cally, find a ready market in the consumer fields of rural
<br />electrification and telephone lines. Lodgepole pine poles
<br />have not been in demand for such uses and an effort - --- - �- -
<br />has been made to ascertain why this should be so. '
<br />We�tern red cedar is used by preference, reaching its }
<br />present posit:on as tlie accepted standard, no dou'ut, ��E
<br />because of its natural durability and an abundant supply
<br />in the Bri+ish Columbia interior. Nevertheless, pine has �t�
<br />better mechanical stren th as '�
<br />g, good if not better ��
<br />physical form, and. is in abundant supply in Alberta. •;; �
<br />In 1948, a surve y was made to discover the reasons '� _ ��
<br />for consumer antipathy tawards lodgepole pine as a ��: .�k .,
<br />utility pole. The two major consuu�ers in Alberta—Ca1- �"�_
<br />gary Power Co and Alberta Government Telephones—
<br />were questioned, as well as Canada �reosoting Co
<br />which is the majar treating concern there. Scme engi-
<br />neers had adopted the policy of using pine poles only
<br />when cedar poles were _not available. This decision
<br />apparently vvas hased mainly on experience with one `
<br />line of pressure-treated loc�gepole pine poles set in 1927;
<br />after 13 years, 4.75% 'of the poles �vere badly rotted
<br />at the graund-line and several had been replaced after
<br />breaking o$ above the ground-line. It was,,impossible to
<br />G. �ramhalt, Research Scientist, Depf of Forestry and
<br />-Rural' Development of �anada, Fores4Products Laboratory, �51'IliiS@=i
<br />Vancouver„8. �.,,Canada t@St pp1@;
<br />Electric�l World, June 26, 1967 '
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<br />Advanced de�ay appears along checks in butt-trea�ed
<br />lodgepole pine; discoloration shows ciearly
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<br />tee! lodaepole pine pole shows,no
<br />spected tie#ore treatmeht, clear .of
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