Support Trestle For Permafrost Areas

Abstract

A trestle system is made to support fluid material conveyors in the air above the earthen overburden covering permanently frozen earth that is generally referred to as permafrost. The system comprises aligned trestles each embodying two limbs crossing each other at a point spaced well above the overburden surface, the limbs having their lower end portions embedded in the frozen earth and having portions above their crossing point connected by a tie beam upon which the conveyor is carried. The limbs extend outwardly and downwardly from their point of crossing at substantially right angles to each other and to the longitudinal axis of the conveyor. Each limb comprises a horizontal footplate embedded in the frozen earth, a steel lower portion secured to the footplate and extending up through and above the overburden, a mid portion of wood, or equivalent nonconductor of heat, overlapped with and affixed to the lower portion and a steel upper portion overlapped with and affixed to the mid portion, the steel upper portion being affixed to the tie beam and to the other limb of the trestle. Certain of the trestles embody braces to oppose leaning of the trestle lengthwise of the supported conveyor. These braces are each made up of a footplate embedded in the frozen earth and spaced endwise of the conveyor from the crossed limbs, steel lower brace portion affixed to the footplate and extending upwardly and toward the trestle, mid-limb portions of wood or equivalent heat insulating material overlapped with and affixed to the steel lower brace portion and a steel cable connecting the upper end of the mid limb portion to the crossed limbs.

Description

BACKGROUND OF THE INVENTION

This invention lies in the broad field of Earth Engineering. It is concerned specifically with providing support means to carry conveyors of fluid material, such as pipelines over areas where the near surface and surface earth consists of a frozen earth subsoil layer that remains frozen throughout the year and a shallow top layer that freezes and thaws with the seasonal changes of the atmosphere. The frozen subsoil layer is often referred to as permafrost. The fluid material carried in the conveyor may often be at a temperature substantially higher than the atmosphere temperature. The top layer or overburden above the permafrost varies in thickness and cannot be depended upon to carry the load on the trestles that support the conveyor. It becomes necessary, therefore, to keep the heat emanating from the conveyor and from the sun from going down the trestle limbs to the footing within the permafrost enough to cause instability of the footing within the permafrost. Since these permafrost areas are difficult to travel in and include trails over which the wild animals roam freely, it is essential that the conveyor be supported well above the ground so it will be readily visible from the air for inspection and so the wild life can cross the conveyor line at will.

A novelty search through the prior patents found in the U.S. Patent Office resulted in finding the patents listed below as most pertinent to the present invention in the opinion of the searcher:

U.s. pat. to Dustman, No. 2,405,819

U.s. pat. to Boucher, No. 2,579,447

U.s. pat. to Miller, No. 2,684,222

U.s. pat. to Schroeter, No. 2,846,168

U.s. pat. to Degen, No. 3,288,406

U.s. pat. to Prouty, No. 3,493,204

U.s. pat. to Davies, No. 3,554,474

An examination of these patents will show that they contain no information directly relating to the problems specifically due to the effect of permafrost conditions upon the support trestles for conveyors such as pipelines.

SUMMARY OF THE INVENTION

The invention comprises a trestle system wherein a series of trestles each including two metal footplates embedded in the permafrost, and spaced apart transversely of the conveyor. A trestle limb is secured to and carried by each footplate. These trestle limbs extend upward and toward each other, crossing each other at right angles several feet above the ground and extending beyond the point of crossing far enough to provide space for a tie beam to connect them and support a saddle for the conveyor above the crossing point. These upward portions above the tie beam provide lateral stops to limit the horizontal transverse movement of the conveyor. Each trestle limb includes a heat insulating portion above the ground and below the crossing to avoid heat conduction downward from the conveyor along the limb to the footplate. All metal parts of the trestle above ground include a covering of insulation to limit transferring of heat from the sun to the footplate. The trestles along the conveyor have braces in alignment with the conveyor to hold the trestles against trestle tilting lengthwise of the conveyor. These braces too embody heat insulating portions below their connection to the transverse limbs and have footplates embedded in the permafrost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a section of a conveyor (pipeline) supported on a plurality of trestles.

FIG. 2 is a fragmentary view showing a lower portion of a trestle connected to and supported on a footplate that is embedded in the permafrost.

FIG. 3 is a side view of a trestle looking lengthwise of the conveyor.

FIG. 4 is an enlarged sectional view on line 4--4 of FIG. 3.

FIG. 5 is an enlarged sectional view on line 5--5 of FIG. 3.

FIG. 6 is an enlarged sectional view on line 6--6 of FIG. 3.

FIG. 7 is an enlarged fragmentary side view of a brace with its lower end secured to a footplate which is set into the permafrost in the same manner as shown in FIG. 2.

FIG. 8 is an enlarged sectional view on the line 8--8 of FIG. 7.

FIG. 9 is a fragmentary topside view of a part of the brace of FIG. 7 as seen from the line 9--9 on FIG. 7.

FIG. 10 is a fragmentary side view of the upper portion of a brace, above that portion shown in FIG. 7.

DESCRIPTION OF PREFERRED EMBODIMENT

A plurality of trestles T of which three are shown in FIG. 1 are used to support a conveyor C of fluid material such as a pipeline. Each trestle T has two trestle limbs 1 and 2 that cross each other at right angles and are bolted together by a bolt 6. A footplate 4 of steel supports the limb 1 and a like footplate 5 supports the limb 2. Bolt 6 connect the limbs 1 and 2 where they cross. The limbs extend above the bolt 6 a substantial distance to provide lateral support for the conveyor C. A tie beam 7 is bolted by bolts 7b to the limbs 1 and 2 at a level spaced above the point where the limbs 1 and 2 cross each other to support the weight of the loaded conveyor C. This tie beam 7 has a block 8 of heat insulating material resting on it and forming a saddle for the conveyor. The two limbs 1 and 2 are also connected to each other by a cross brace 9 that is spaced below the bolt 6 and bolted to both limbs by bolts 9b.

The two limbs 1 and 2 are substantially alike. Each limb comprises an upper portion 1a or 2a which is an angle iron that extends downward from the top of the limb to a point below the brace 9 far enough to provide for an overlapping connection with a mid-portion lb or 2b of heat insulating material such as water-proofed wood. The mid portion is square in cross section so as to fit within the angle of the upper portion. Bolts 10 connect the portions in the manner illustrated in FIG. 4. The lower portions 1c and 2c of the limbs 1 and 2 are angle irons overlapped and connected with the mid portions. The above ground parts of the angle irons are covered with a heat insulating material shown at 11 in FIG. 4. Asbestos filled white paint is a good material for covering the angle irons. The lower ends of the portions 1c and 2c are bolted to upstanding brackets 12 on the footplates 4 and 5 by bolts 13. The footplates 4 and 5 and their brackets are frozen in the permafrost. The limb portions 1c and 2c extend upward and toward each other at an angle of about 45.degree. to the horizontal and terminate above the ground surface. They are partially covered by the earth about the permafrost yet they are supported and anchored by the footplates which are set down deep enough in the permafrost so they will not be loosened by freezing and thawing of the covering layer of earth and the snow and sun upon the exposed upper parts of the portions 1c and 2c above the level of the ground. FIG. 2 of the drawings depicts graphically the preferred relation between the length of the part underground to the part above ground in the limb portions 1c and 2c. Only enough of the angle iron should be above ground to provide mounting for the mid portion 1b or 2b to keep this mid portion spaced above the ground surface at all times.

It is necessary to provide stability endwise of the conveyor for the several trestles T. This is accomplished by utilizing the braces shown in FIGS. 1, and 7 to 10 inclusive. These braces 14 and 15 are alike so a description of one will cover both of them. Footplate 16 is set into the permafrost directly below the conveyor C and on opposite sides of the plane of the trestle limbs 1 and 2. Each brace embodies a lower angle iron brace portion 18 that is bolted on a bracket ear 19 on the respective footplate 16 by a bolt 20. The lower end of the angle iron 18 is flattened transversely as indicated in FIG. 7, at 18a to fit over the bracket ear 19. The upper end of the angle iron 18 is overlapped with a mid-brace portion brace 21, and bolted to the brace portion 21 by a bolt 22. A short angle iron 23 overlaps and is bolted to the top of the mid portion 21 and connected at its upper end to an extensible cable portion 24. The cable portion 24 of the brace is secured by a connector 25 to the bolt 6 connecting the trestle limbs 1 and 2. This connection may be made through the tie beam 7 is desired. Changes in the length of the cable portion 24 are made by a turnbuckle 26.

Braces 14 and 15 are not necessary on all trestles but may be used at intervals along the conveyor wherever necessary.

The trestle assembly is so constructed that any repair or replacement is made quite easy. The wide spread between the footplates 4 and 5 with respect to the conveyor protects it against displacement by wind and drifting snow. More or less height of a trestle above ground is had by using longer or shorter mid portions 1b and 2b. Where the ground slopes transversely to the conveyor longer mid portions in the downhill limbs of the trestle and shorter mid portions in the uphill limbs of the trestle are used.

Claims

The invention is defined in the following claims:

1. A trestle for support of an above-ground conveyor of fluid material over permafrost ground area, comprising:

a pair of upright trestle limbs;

the lower end of each trestle limb being adapted to be embedded within a permafrost zone below ground level;

a relatively broad footplate mounted to the lower end of each limb and adapted also to be embedded within the permafrost zone, each footplate having a horizontal area sufficient to assure permanent support of the trestle limb by the permafrost;

each limb embodying a lower limb portion of metal extending from the footplate through the ground surface, a mid-limb portion of heat insulating material affixed to and projecting upward from the lower limb portion, and a top limb portion of metal affixed to the mid-limb portion;

the top limb portions of the respective trestle limbs being joined to one another;

said top limb portions of the trestle limbs being crossed and fixed to one another;

a tie beam connecting the top limb portions of said limbs above the point where they cross;

and conveyor support means mounted to the top limb portions of the trestle limbs having a saddle for supporting the conveyor.

2. A trestle as set out in claim 1 further comprising:

paired braces extending lengthwise of the conveyor, each brace fixed to the trestle limbs beneath the conveyor support means and extending downwardly and oppositely outward from the trestle limbs.

3. A trestle as set out in claim 2 further comprising:

a relatively broad footplate mounted to the lower end of each brace adapted to be embedded within the permafrost zone, each footplate having a horizontal area sufficient to assure permanent anchoring of the brace by the permafrost.

4. A trestle as set out in claim 1 wherein the mid-limb portion of each trestle limb is constructed of wood.