US3722378A

US3722378A - Insulated trafficked surfaces

Info

Publication number: US3722378A
Application number: US00112635A
Authority: US
Inventors: J Best
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1971-02-04
Filing date: 1971-02-04
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27

Abstract

Trafficked surfaces built on foundations which remain substantially undisturbed during seasonal climatic cycles, particularly in permafrost and near permafrost regions where considerable disturbance of the ground beneath foundations is otherwise common. The foundations include combinations of insulation layers, heat sinks and/or thermal bleeds which dampen and prevent the cyclic climatic seasonal variations from affecting the earthen support under the foundations, in both cut and fill sections, and in embankments and backfills adjacent the sections.

Description

INSULATED TRAFFICKED SURFACES DESCRIPTION OF THE INVENTION This invention concerns itself with trafficked surfaces such as paved or unpaved roadways, airport runways, walkways, railroad roadbed foundations and the like. The present invention provides foundations for such trafficked surfaces so that the same are not disturbed by the climatic cycles experienced in regions having significant winter seasons where freezing and/or thawing conditions otherwise disturbtlie trafficked surface. Some attempts to avoid such problems have been tried with insulation layers alone in both permafrost and non-permafrost regions, in an attempt to keep the ground from freezing below the trafficked surface during the winter, and to prevent permafrost soil from thawing during the summer with attendant settlement of the trafficked surface. However, both of these applications fail to fully satisfy the problems to which they are directed, `particularly in borderline areas between seasonal frost and permafrost regions, and in many of the permafrost regions.

Particular `problem `areas are the permafrost regions found in the `middle and southem-middle parts of Alaska, for example, where the perrnafrosts specific heat capacity is not so great that it can absorb much heat without significant thawing. To prevent such thaw ing using only insulation such as a layer of insulating plastic foam as, for example, Styrofoam HI brand extruded expanded polystyrene produced by The `Dow Chemical Company, would be impractical. since it would'have to be Vso excessively thick to guarantee practically 100 percent resistance against thawing of the earthen material therebelow. Likewise, in the seasonal frost zone closely adjacent to the permafrost regions where it is desired to keep the ground underneath the foundation from freezing, the average temperature of the ground is so close to the freezing point that only a small amount of cold weather during the winter season would cause it to freeze up. Again, with only an insulation layer, such as the foam described, the layerwould have to be so thick in this extreme situation to guarantee no cold penetration to the supporting earthen frost susceptible material so as to be impractical. i

Accordingly, it is among the objects of the present invention to provide a construction for trafficked surfaces and adjacent areas which prevents degradation of the same due to the winter freezing in seasonal frost zones and during the summer in permafrost zones and, particularly, in those locations where the permafrost zone and the seasonal frost zone are closely adjacent to one another and the support of trafficked surfaces is a particular problem. i

It is amongfurther objects of the present invention to provide supplementation to customary insulation to absorb the deficiencies of the same in preventing degradation of foundation and earthen support for trafficked surfaces and to embankments and backfills ad jacent thereto.

Briefly, the primary objects of the present invention are accomplished by supplementing an insulation layer with an artificial thermal cell or heat sink where the natural specific heat capacity of the earthen support is insufficient to avoid significant degradation by varying climatic influences. The heat sink fluid or material absorbs or dissipates a given amount of heat as a phase change occurs, e.g., ice :melting to water or water crystalizing into ice. Different heat fluid materials require different amounts of heat gain or loss to effect a phase change. In the permafrost regions the fluid solution in the heat sink is substantially frozen at the cornmencement of the warm season and designed with sufficient capacity to absorb excess heat which passes therethrough such that substantially no heat reaches the permafrost located therebelo'w during that season. In the wintertime the heat absorbed by the heat sink is dumped into the adjacent freezing earth, which then has capacity to receive the same, and eventually into the atmosphere to prepare the heat sink for the next warm season. Thermal bleedsl can further supplement heat dissipation in special situations. Embankments, backfills, ditches, and other areas adjacent the trafficked surface can employ heat sinks and/or insulation layers to protect them from climatic disturbances. In the seasonal applications where it is desired to keep the cold `during `the winter from penetrating the frost susceptible soil beneath the trafficked surface foundation, the heat sink carries a fluid which has a phase A characters of reference designate` corresponding' material and parts throughout the several views thereof, in which:

FIG. A1 is a cross half-section of a fill section for a trafficked surface for permafrost regions constructed according to the principles of the present invention;

FIG. 2 is a cross half-section like FIG. 1 only showing a modified form thereof; I

FIG. 3 is a cross half-section through a cut section for a trafficked surface with an adjacent backfill area constructed according to the principles of the present invention;

FIG. 4 is a cross half-section of a modified form of a trafficked surface foundation including a two phase transfer fluid thermal bleed as one foundation element;

FIG. 5 is a detailed cross half-section of the thermal bleed of FIG. 4 containing such a transfer fluid;

FIG. 6 is a cross half-section of a fill section for a trafficked surface employed in a seasonal frost region according to the principles of the Vpresent invention; and

FIG. 7 is a graphical representation of the advantages of a specific example of the present situation.

The present invention concerns itself with minimizing the effect of environment ori trafficked surface constructions such as roadways, walkways, runways and the like, paved or unpaved; wherein the effect of freezing and thawing can be detrimental to such constructions.

By permafrost is generally meant soil, rock, tundra or other ground or earthen material which is frozen in the winter and which does not completely thaw out heat sink, permitting each to be of a practical design. However, during the winter season the insulation layer dampens the freezing effect of the colder season from regenerating the heat sink. But because in pennafrost and near permafrost regions the winter season is so severe and longer lasting than the summer season, proper designing of the insulation layer still permits regeneration of the heat sink in the winter while preventing undue heat penetration during the summer.

It is also possible to alter the order of the placement of the insulation in the thermocell but the preferred method is to place the thermocell next to the permafrost. It is also possible to locate a layer of insulation below the thermocell as well as on top of it where conditions are unduly severe or where the permafrost has already been substantially degraded. In the latter instance the insulation layer will permit the degraded area to gradually refreeze and once refrozen to remain the same. Such an arrangement is illustrated by the insulation layer 45 shown in FIG. 3, for example.

The embankment problem is greater than that at the center of the foundation since the cover over the permafrost layer decreases as the embankment leaves the traffic surface 14 and approaches the tundra 12. To compensate for the decreasing lack of cover, the insulation layers and/or the heat sinks have to be increased in capacity, due to the decreased resistance to heat penetration through the gravel Cover to the permafrost during the summer.

A specific example of a typical fill section constructed according to this invention, like fill section 10, has been taken for a situation where without any protection the permafrost would thaw to a maximum depth of at least 5 feet during the summer season. In prior art practice it normally would have taken at least a 14 foot depth of gravel to completely eliminate the thawing of the permafrost in such instance. In computing the effect of insulation, heat sink, and gravel according to Thermal conducitivity of insulation `=`0.020` BTU/hr/ftF.

Mean Vannual air tem-petre': 30 24.2 sin (2 1r r/365 1.98) (used as surface temperature where 1" is time in days) Freezing point of sink fluid 30F.

Considering that lthere may be some conduction by fluid motion in the heat sink, which can be kept to a minimum by use of some congealant such as methylcellulose or some other cellulose or like material added to the liquid 24, and ignoring the added insulation effect of melted liquid 24 after it thaws, so that the calculations are conservative, the computed relative effects `are shown in the Graph of FIG. 7. At one end it can readily be appreciated that with l foot of gravel an im practical 5% foot deep sink would be required with no insulation layer tovprevent thawing of the permafrost layer. At the other end, even with 7 feet of gravel and 2 inches of insulation some heat sink (greater than V4 foot in depth) is required to prevent thawing of the permafrost. Ideally some combination in between is the most advantageous practical solution to the situation, which is permitted by employing; the concepts of this invention.

Another advantage of the insulation heat sink combination of this invention over that of pure insulation is that the heat sink can more readily refreeze permafrost that has been thawed. The size of the heat sink, of course, varies directly with the thickness of the insulating layer as its purpose is to absorb any heat which flows through the insulating layer. It appears clear that if there were no insulation in this instance the sink would have to be impractically large to take care of total elimination of permafrost thawing or the insulation layer or gravel layer would have to be impractically thick to accomplish the same purpose.

Where conditions are not as sensitive as that contemplated by section 10 it may be possible to employ a section 30 as illustrated in FIG. 2. Here the insulation layer 18 is effective enough to prevent thawing during a reasonably short summer cycle where the temperatures do not get too high, such as found. in the northern parts of Alaska. ln thiscase the natural specific heat capacity of the ground in the center section A is able to generally accept the heat which might come through the insulation layer` 18 without undue degradation of the tundra 12 and permafrost 13. The side effectsl along the embankments 28 can adequately be taken care of by heat sinks 20 alone. The heat sinks 20 need no t be impractical in size even though they may be used generally without an insulation layer, because of the generally frigid climate and short summer season. An

overlapping of the insulation layer 18 and the upperA heat sink 20 is generally preferred underneaththe edge of the traffic surface 14 to provide a desirable transition between the two permafrost protective systems.

Yet another modification of the present invention is that of a cut section as illustrated, for example, in FIG. 3. Here the cut section 40 is'cut deeply through the tundra layer 12 and into the underlying permafrost layer 13 which might typically be the case where a roadway is being built along a hillside or on other unlevel terrain. The permafrost 13 is cut back generally to the line 42 and a leveling gravel layer 44 is `placed over the cut away section on top of the permafrost 13'. Optionally included is an insulation layer 45 much like layer 18, below uppermost heat sink 20 in foundation 16, to provide for effective refreezing of the permafrost 13, if the a ditch 48 which has special problems of its own since a ditch is adapted to receive water and the water, because of the heat from the summer, can present a greater and more persistent potential thawing problem for the permafrost 13 therebelow. Accordingly, to take care of this special ditch problem a much larger heat sink 50, perhaps with half again as much capacity as a usual heat sink 20, might be employed under the ditch to absorb extra quantities of heat flowing through the insulation layer 18. Also, a thicker insulation layer could be used if more resistance to heat transfer is required.

Extending upwardly from the ditch line up backslope 53 to the original ground elevation level 52 and tundra 12, heat sinks 20 and insulation 18 can be placed over the gravel leveling layer 44 to prevent thawing along the backfill 53. This will prevent thawing of the higher embankment so that it does not fall into the ditch or interfere with traffic surface 14. On top of the insulation 18 along backslope 53 can be soil 54 which can support vegetation, or gravel, or any other finish surface for the backfill embankment as may be desired.

FIG. 4 is a modification of the section 10 embodiment of FIG. l, wherein a foundation 53 includes a thermal bleed means 56, hereinafter referred to as thermal bleed 56, employed between the insulation layer 18 and the heat sink 20. The thermal bleed 56 of FIG. 4 serves to provide extra dissipation of heat as might be experienced especially in the marginal areas between permafrost and seasonal frost regions. Here greater quantities of heat then normally would be expected in the colder climates can be particularly hazardous-to the permafrost supporting the foundation for trafficked surfaces 14. To aid in the dissipation of such excess quantities of heat, a heat exchanger 58 and a condensing unit 60 can be employed acting cooperatively with a two phase heat transfer fluid 59 in thermal bleed 56. Also included under the heat sink 20 can be an insulation layer which serves again, as layer 45 previously described, to limit the heat flow associated with the refreezing of permafrost, which might have suffered some degradation before traffic surface and its foundation is applied thereto so heat flow to the heat sink is at a desired rate. The main difference here is the addition of the two phase thermal bleed 56 to the foundation. Thermal bleed 56 can be built like heat sink 20 but is filled with a two phase heat transfer fluid or dissipatoi' 59, like a methyl bromide/methyl chloride mixture solution, having a boiling point, for example, of 20 F. to 32 F. at 760 mm. of mercury.

Other suitable fluids for use in the present invention are materials such as dichlorodifluoromethane, sulfur dioxide, ethylchloride, trichlorofluoromethane, a lzl mixture of methyl bromide and methylchloride. Beneficially by employing such liquids the pressure within the thermal bleed can be maintained from about -25 pounds per square inch absolute and conventional pressure equipment avoided. This fluid can be filled to about half the level of thermal bleed 56. The thermal bleed 56 is connectedto a tubular system 63 within heat exchanger 58 by an upper flow passage 55 in open communication with the upper non-liquid part of thermal bleed 56 and by lower passageway 57 in open communication with the lower liquid filled portion of thermal bleed 56 for return of condensed fluid 59. As shown more particularly in FIG. 5, openings 23 in core 22 allow the liquid to vaporize into the upper half of thermal bleed 56 and pass as a gas to passageway 55. The heat exchanger is filled about tubular system 63 with a heat sink solution 24 which solution should have a freezing (phase change) point below the boiling point of two phase heat transfer fluid, or with cryogenic liquid or fluid cooled by mechanical'refrigeration. Extending out from heat exchanger 58 are condenser elements 60 in open communication with tubular system 65. An optional heat exchange bypass line y63 can be used for winter operations, by operation of a two-way valve. ln order to maintain a pressure system no greater than one atmosphere,`a vent 6I for exhausting excess gases from tubular system 63 can form part of the con-` denser system so the components need not be designed to take high pressures without failure.

The two phase fluid 59 in the thermal bleed 56 boils at a temperature greater than that of the heat exchanger 58 so that when solar heat is absorbed the phase changes and the generated vapor passes through passageway 55 to the heat exchanger 58 in the summer months. Since the heat sink solution 24 is at a lower temperature than the boiled off gas, heat is absorbed from the gas with the result that the gas condenses and returns to the thermal bleed as a liquid. The heat exchanger thus works as a refrigerator during the summer months. During the winter months the gas passes through the heat exchanger into the condenser elements 60 where the cold air around the condenser elements 60 absorb heat from the gas, resulting in condensation of the gas and its return to the thermal bleed 56 via passageway 57.

An application of the present invention to seasonal regions is illustrated by the section in FIG. 6. Again, a typical fill section is used wherein there is a traffic surface 14 supported on a foundation 72 comprising insulating

layers

74 and 76 and a thermocell or heat sink 78. The insulation layers and heat sink can be as those previously described in FIGS. l and 3. However, their function is significantly different in the seasonal application. Here the ground supporting the foundation is warmer than 32 and it is desired to protect .this ground during the winter season so as to prevent disruption, such as heaving of the traffic surface 14 due to frost action and the like as such problems are discussed in U.S. Pat. No. 3,250,188, for example. Again, this is essentially a borderline area use between seasonal frost and permafrost regions so that the seasonal application is considered to be supplemental to the more usual seasonal applications as contemplated by the aforesaid U.S. Pat. No. 3,250,188. Heat sink 78 in this application contains a fluid 82 which has a phase change temperature of at least 32 F., or in any event, greater than the freezing temperature of the ground 80 so that the latent heat of fusion of the solution can absorb the cold, i.e., lose heat without causing the ground 80 to lose heat. The heat sink can be designed so that by the end of the winter it will just about freeze and then when the summer comes it can again thaw, i.e., be regenerated so as to be able to lose heat during the next winter. The lower insulation layer 76 assures that the interface between the soil and the protection system will be greater than 32 F. The upper insulation layer 74 is optional depending on the severity of the winter season to which this section 78 will be subjected.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention. For example, various combinations of heat sinks, insulation layers, and/or thermal bleeds described hereinabove can satisfy special applications not specifically mentioned above and still come within the scope of this invention as claimed. Likewise the thermal bleed with heat sink/condensers can find year round use for special applications in and of itself.

AccOrdingly, what is claimed as new is: 1. A traffic surface exposed to an alfresco environ- 4ment and supported on a foundation, wherein said foundation serves to dampen substantially or eliminate the effect of climatic seasonal variances on the underlying earthen support; said foundation comprising a foam insulation layer resisting heat flow, and a thermal cell means comprising an artificial substantially impermeable envelope means above or below said foam insulation layer and containing a regenerative heat sink material having sufficient heat sink capacity with said foam insulation layer to prevent thermal degradation of said supporting earthen material.

2. The traffic surface and foundation of claim l wherein said foam insulation layer is located below said traffic surface and said thermal cell means is located below said foam insulation layer.

3. The traffic surface and foundation of claim 2 wherein said earthen material is permafrost.

4. The traffic surface and foundation of claim 3 wherein said foam insulation layer is located below said thermal cell means to control regenerating degraded permafrost earthen material therebelow.

5. The traffic surface and foundation of claim 3 wherein a gravel layer is located at least between said traffic surface and said foam insulation layer. y

6. The `traffic surface and foundation of claim 3 wherein said foam insulation layer is substantially uninterrupted over that part of the earthen support to be protected from thawing, said foam insulation layer serving `as a thermal resistance to prevent excessive heat flow to the thermal cell means.

`7. The traffic surface and foundation of claim l wherein said thermal cell means is located below said traffic surface and said foam insulation layer is located below said thermal cell means.

8. The traffic surface and foundation of claim 7 wherein said earthen material is in a non-permafrost condition.

9. The traffic surface and foundation of claim 8 wherein another foam insulation layer is located between said traffic surface and said thermal cell means.

l0. The traffic surface and foundation of claim 8 embankment thermal cell means. 1

13. The traffic surface and foundation of claim 12 wherein said embankment ends at a ditch area and said ditch area includes a thermal cell means therebelow.

14. The trafc surface and foundation of claim 13 wherein a backslope extends upwardly from said ditch area and includes a foam insulating layer and/or thermal cell means to prevent degradation thereto.

15. The traffic surface and foundation of claim 1 wherein said foundation is a cut or fill section.

16. The traffic surface and foundation of claim l wherein said foam insulation layer is located substantially continuously below the traffic'surface.

17. The traffic surface and foundation of claim 16 wherein said foam insulation layer is uninterrupted by high heat conductive elements which short circuit the thermal resistance provided by said foam insulation layer.

18. The traffic surface and foundation of claim 1 wherein said foam insulation layer is substantially uninterrupted below said traffic surface.

19. The'tratfic surface and foundation of claim 1 wherein foam insulation layers are located both above and below said thermal cell means.

20. A method for controlling heat flow between a traffic surface foundation and its earthen support, comprising the steps of locating a foam insulating layer or layers and heat absorbing and/or dissipating elements between said traffic surface and said earthen support, said elements comprising at least an artificial substantially impermeable envelope means containing a regenerative heat sink material, said locating occuring after first selecting said foam insulating layer or layers and said elements such that their determined combined insulation, heat absorbing and/or dissipating effect is to prevent disruption of said traic surface which could otherwise occur in a climatic region experiencing freezing temperatures.

21. The method of claim 20 wherein said earthen support can be permafrost or non-permafrost.

United States Patent Koester [75] Inventor: Waldemar Koester, Forsbach, Ger-V many [73] Assignee: Friedrich Mauer Soehne, Munich,

Germany [22] Filed: Mar. 10,1971

[2l] Appl. No.: 122,788

[30] Foreign Application Priority Data Sept. 19, 1970 Germany P 20 46 400.0

[52] Us. C1 U41m/68 [51] Int. Cl .t E016 11/10 [58] Field of Search ..94/18, 22, 51

[56] References Cited UNITED STATES PATENTS 3,474,589 lO/l969 Cheatwoocl ..94/18 X 3,447,430 6/1969 Gausepohl ..94/18 2,041,210 5/1936 Robertson ..94/18 2,246,903 6/1941 Spears ..94/18 3,172,237 3/1965 Bradley ..94/18 X u 3,722,379 [451 Mar. 27, 1973 Primary Examiner- Nile D. Byers, Jr. Attomey-Wolfgang G. Fasse [57] ABSTRACT The present invention relates to a method of constructing an expansion gap between two structural members such as concrete slabs in roads or on bridges. First the concrete slabs are Vformed with a gap between two adjacent slabs whereupon a surface layer is applied to the slabs to cover the slabs as well as the gap. rlhereafter, a recess is formed in the surface layer above the gap but wider than the gap. A lost casing is then inserted into the recess and gap and the space laterally adjacent to the lost casing is filled with a synthetic resin concrete. When the concrete is set, a cross portion of the lost casing which bridges the gap is removed, for example by sawing. An elastic sealing body or strip is inserted either as: a unit with the lost casing or it is snapped into position, after said `cross portion has been removed, in recesses formed by saidv lost casing in the synthetic resin concrete. The lost casing is a downwardly open profile with shaped side members for forming said recesses and interconnected by said cross portion.

Claims

1. A traffic surface exposed to an alfresco environment and supported on a foundation, wherein said foundation serves to dampen substantially or eliminate the effect of climatic seasonal variances on the underlying earthen support; said foundation comprising a foam insulation layer resisting heat flow, and a thermal cell means comprising an artificial substantially impermeable envelope means above or below said foam insulation layer and containing a regenerative heat sink material having sufficient heat sink capacity with said foam insulation layer to prevent thermal degradation of said supporting earthen material.

2. The traffic surface and foundation of claim 1 wherein said foam insulation layer is located below said traffic surface and said thermal cell means is located below said foam insulation layer.

5. The traffic surface and foundation of claim 3 wherein a gravel layer is located at least between said traffic surface and said foam insulation layer.

6. The traffic surface and foundation of claim 3 wherein said foam insulation layer is substantially uninterrupted over that part of the earthen support to be protected from thawing, said foam insulation layer serving as a thermal resistance to prevent excessive heat flow to the thermal cell means.

7. The traffic surface and foundation of claim 1 wherein said thermal cell means is located below said traffic surface and said foam insulation layer is located below said thermal cell means.

10. The traffic surface and foundation of claim 8 wherein a gravel layer is located at least between said traffic surface and said thermal cell means.

11. The traffic surface and foundation of claim 1 wherein an embankment extending from said traffic surface towards said earthen support includes at least additional thermal cell means having sufficient heat sink capacity to prevent degradation of said earthen support adjacent said embankments.

12. The traffic surface and foundation of claim 11 wherein a foam insulation layer is located above said embankment thermal cell means.

14. The traffic surface and foundation of claim 13 wherein a backslope extends upwardly from said ditch area and includes a foam insulating layer and/or thermal cell means to prevent degradation thereto.

16. The traffic surface and foundation of claim 1 wherein said foam insulation layer is located substantially continuously below the traffic surface.

19. The traffic surface and foundation of claim 1 wherein foam insulation layers are located both above and below said thermal cell means.

20. A method for controlling heat flow between a traffic surface foundation and its earthen support, comprising the steps of locating a foam insulating layer or layers and heat absorbing and/or dissipating elements between said traffic surface and said earthen support, said elements comprising at least an artificial substantially impermeable envelope means containing a regenerative heat sink material, said locating occuring after first selecting said foam insulating layer or layers and said elements such that their determined combined insulation, heat absorbing and/or dissipating effect is to prevent disruption of said traffic surface which could otherwise occur in a climatic region experiencing freezing temperatures.