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| United States Patent | 3,909,143 |
| Cushman | September 30, 1975 |
Roadway construction and method therefor
Abstract
A roadway has a containerized roadbed of a width sufficient to support a road surface and a depth sufficient to extend below the frost line of the earth in the area; the containerized roadbed has an outer enveloping wall of suitable elastomeric material which contains therein suitable filler material such as, for example, dirt, sand and rock; the containerized roadbed is evacuated to remove moisture from the filler material and hermetically sealed; a suitable road surface, as for example a layer of concrete, is formed atop the containerized roadbed.
| Inventors: | Cushman; Walton W. (Fraser, MI) |
| Assignee: |
Romanski; Lon H.
(Sterling Heights,
MI)
|
| Appl. No.: | 05/376,396 |
| Filed: | July 5, 1973 |
| Current U.S. Class: | 404/27 |
| Current International Class: | E01C 3/06 (20060101); E01C 3/00 (20060101); E01C 003/00 () |
| Field of Search: | 404/28,29,31,19,17,27 52/169,294,515 206/45.33 |
| 1565682 | December 1925 | Strahan |
| 2044498 | June 1936 | Pearce |
| 2211649 | August 1940 | Drury |
| 2649101 | August 1953 | Suits |
| 3279334 | October 1966 | Quartararo |
| 3424647 | January 1969 | Callahan |
| 3474625 | October 1969 | Draper |
| 3577893 | May 1971 | Towner |
| 3646721 | March 1972 | Becker |
| 3659812 | May 1972 | Carlsson |
Attorney, Agent or Firm:
RELATED APPLICATION
This application is a continuation of my copending application Ser. No. 144,447 filed May 18, 1971 now abandoned, for "Roadway Construction and Method Therefor."
I claim:
1. A roadway, comprising a roadbed, and a road surface carried atop said roadbed, said roadbed comprising a relatively flexible and moisture impervious outer container of exclusively plastic material having an upper wall surface a lower wall surface side wall portions and end wall portions, filler material filling the interior of said outer container, said outer container being hermetically sealed with said interior and said filler material contained therein being evacuated to a gas pressure of a magnitude substantially less than the magnitude of the surrounding ambient atmospheric pressure, said plastic material being elastomeric, said lower wall surface of said outer container being situated at a level below the frost line of the surrounding earth, a trench excavated in the earth, said trench having a lower surface below the frost line of the surrounding earth, and wherein said lower wall surface of said outer container is supported by said lower surface of said trench, and wherein said filler material comprises such earth as was obtained in the excavation of said trench.
2. A method of constructing a roadway, comprising the steps of forming an outer casing from a relatively flexible and moisture impervious exclusively plastic material, filling said casing with a suitable filler material, hermetically sealing said outer casing, subjecting the interior of said outer casing and said filler material contained therein to a process of evacuation so as to produce within said outer casing a gas pressure of a magnitude substantially less than the magnitude of the surrounding ambient atmosphere pressure, laying a layer of material atop said outer casing for forming a road surface, digging a trench within the earth so as to have a lower surface of said trench at a level below the natural frost line of the surrounding earth, forming said outer casing as to have an upper wall surface a lower wall surface opposed end wall portions and opposed side wall portions, placing said casing within said trench as to have said lower wall surface supported by said lower surface of said trench, returning the earth excavated during digging of said trench to the interior of said outer casing so as to thereby form at least a portion of said filler material, and wherein the step of evacuation includes the removal of at least a substantial amount of any water vapor contained within said outer casing.
According to the disclosure a method of constructing a roadway includes excavating a ditch of the required width and depth with the depth being of a dimension to sufficiently extend below the natural frost line, placing a suitable liner of elastomeric material in the trench or ditch, filling the liner with material removed in the process of forming the ditch or trench, hermetically sealing the liner as to contain the filler material within the liner, evacuating the interior of the liner as to thereby remove any moisture from within the liner and to atmospherically compact the material within the liner, and then placing a layer of material atop the liner to form a road surface.
BACKGROUND OF THE INVENTION
Heretofore, various methods have been proposed and employed in the construction of roadways. However, such roadways, especially in areas where the earth is subjected alternately to freezing and thawing, undergo progressively increasing deterioration and breakage. Such deterioration is principally caused by the moisture contained in the roadbed. That is, because of rain and sub-surface seepage the material forming the roadbed usually contains a degree of water which, when freezing conditions occur, freezes and expands. Such expansion results in the uneven application of upward forces against the material forming the road surface causing cracks and other failures therein. The same results are obtained, for example, during seasonal changes where snow may be deposited on and about the roadway one day then melt and after melting again freeze because of atmospheric changes.
Those skilled in the art have been aware of the damage caused by the freezing of water because of the elaborate steps taken to try to provide material for the roadbed which would enhance drainage. However, as is evident from the damaged state of roadways which are more than a year old indicates that the prior art roadbeds still contain a high degree of water and the roadways are still just as susceptible to damage from cyclic freezing and thawing of such water.
Accordingly, the invention as herein disclosed and described is primarily directed to the solution of the above as well as other related problems.
SUMMARY OF THE INVENTION
According to the invention, a roadway comprises a roadbed, and a road surface carried atop said roadbed, said roadbed comprising a relatively flexible and moisture inpervious outer container having an upper wall surface a lower wall surface side wall portions and end wall portions, and filler material filling the interior of said outer container, said outer container being hermetically sealed with said interior and said filler material contained therein being evacuated to a gas pressure of a magnitude substantially less than the magnitude of the surrounding ambient atmospheric pressure.
DESCRIPTION OF THE DRAWINGS
In the drawings, wherein for purposes of clarity certain details and/or elements may be omitted from one or more views:
FIG. 1 is a perspective view of a roadway, embodying the teachings of the invention, shown in cross-section at one end thereof and with some of the surrounding earth removed for purposes of clarity; and
FIGS. 2, 3, 4, 5 and 6 pictorially illustrate the various steps employed in constructing the roadway of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now in greater detail to the drawings, FIG. 1 illustrates a roadway 10 comprised of a containerized roadbed 12 situated generally within a ditch or trench 14 and a road surface 16 formed thereatop as by a concrete slab 18.
In the embodiment shown, the trench 14 would be formed as to have the lower surface 20 thereof below the level of the natural frost line as depicted generally at 22. The frost line is, of course, the depth of the terrain to which freezing temperatures above the surface of the terrain will be effective in freezing that terrain as well as any moisture contained therein. Therefore, a frost line of, for example, three feet would mean that any material or moisture at such a depth greater than three feet from the surface would not become frozen due to prolonged freezing temperatures above the surface.
The roadbed 12, as generally shown in both FIGS. 1 and 4, is comprised of an outer container 24 which has upper and lower walls 26, 28, opposed side walls 30, 32 and opposed end walls 34, 36. The container 24 may be formed of, for example and not by way of limitation a suitable elastomeric material such as polyethylene or polypropylene. Such material would be impervious to water vapor at pressures at least equal to and at least somewhat greater than atmospheric pressure.
The interior of the container 24 would be filled with material as, for example, was excavated during the formation of the trench 14 and the side walls 30, 32, end walls 34, 36 and top wall 26 would be formed as by wrapping the material (which may originally be in sheet form) forming the container 24 about such filler material and hermetically sealing the edges of such material. Once the roadbed is thereby formed, the road surface can be layed atop thereof in any conventional manner as by the pouring of a concrete slab 18.
One method particularly suitable for the construction of such a roadway 10 is illustrated by FIG. 2, 3, 4, 5 and 6 to which specific reference will now be made.
The first step of the disclosed method would be the formation of a suitable trench 14 in the earth 38 as fragmentarily illustrated in perspective and cross-hatched as in FIG. 2. The trench would be elongated having a lower surface 20, below the natural frost line 22, and opposed side walls 40 and 42 (which need not be substantially perpendicular to the lower surface 20 as shown). By way of example, the ditch or trench 14 may, arbitrarily be 20.0 feet wide by 4 feet 8 inches deep on the assumption that the road surface slab 18 will be 8.0 inches thick. The dirt, sand, rock or other material removed during the excavation of the trench 14 may be deposited in close proximity to the trench 14 for purposes to be described.
After the trench 14 is properly formed, a liner or sheet 44 of elastomeric material is laid within the trench 14 as to have a bottom portion thereof 28 lying against and supported by the lower surface 20 of trench 14 and upwardly directed portions 30 and 32 of the sheet 44 juxtaposed to side walls 40 and 42 of the trench 14. The sheet 44 would continue having portions 26a and 26b overlying the surrounding surface of the ground 38 as generally shown in FIG. 3.
After the liner 44 is placed within the trench 14, it may be filled with the material excavated during the formation of the trench 14. The liner 44 is then folded, much in the manner as in wrapping a package, thereby forming end walls 34 and 36 as well as employing portions 26a and 26b to form the upper wall 26. When the sheet 44 is thereby folded it assumes a configuration somewhat as depicted in FIG. 4 wherein an outer container 46, which may have seams 48, 50, 52, 54, 56, 58 and 60 relatively tightly contains the filler material 62 (in this case, the earth excavated during formation of the trench 14). The seams 48-60 are then hermetically sealed by any suitable means such as, for example, through the application of a suitable impervious cement, adhesive or tape, or, by means of the application of heat thereto as to cause a heat weld of the seams.
Next, as generally depicted in FIG. 5, suitable aperture means 62 is formed through, for example, the upper wall 26 of the container 46 and a suitable conduit-like adapter 64 is inserted therein and operatively connected to a vacuum pump 66. The adapter 64 may, as shown, include a rather large annular flange portion (which may be flexible) so as to in and of itself act as a seal during the time that the vacuum pump 66 is energized.
Vacuum, created by the pump 66, is thereby applied to the interior of casing 46 and may be in the order approaching 14.7 pounds per square inch. Generally, the higher the value of the vacuum, the better the results will be.
Because of the application of such vacuum at least two beneficial results are obtained. First, whatever moisture was contained within the casing 46 or the filler material therein is removed by the lowering of the pressure within casing 46. That is, once the pressure within casing 46 is reduced, the vapor pressure of the moisture causes the interior of the casing to be filled with water vapor which, in turn, is progressively and continually removed by the action of the vacuum pump 66. The vacuum thereby produced is applied to the interior of the casing 46 for a time sufficient to assure the removal of substantially all of the water vapor contained therein.
As somewhat pictorally represented in FIG. 5, the adapter 64 may include a valve member 68 which can be actuated to a closed position after the interior of the casing 46 has been sufficiently evacuated thereby sealing the interior of casing 46 from the ambient atmosphere. It should be apparent that the relative sizes of the adapter 64 and casing 46 are shown out of proportion merely for purposes of illustration and disclosure. In reality any suitable connection could be made as between the interior of casing 46 and pump 66 including tubing means which could be collapsed upon a force greater than 14.7 pounds per square inch in order to close-off the interior of the casing 46 with respect to the ambient atmosphere. Such suitable adapter means as 64 could then be further sealed with cement, adhesive or heat in order to assure the hermetic sealing the casing 46.
The second major benefit of such evacuation of the casing 46 is the resulting strength and rigidity of the roadbed 12. That is, because of the flexibility of the liner of casing 46, when the interior thereof is evacuated the resulting pressure differential between the interior and the atmospheric pressure externally thereof causes the filler material 60 within the casing 46 to become compacted and extremely rigid. The rigidity of the roadbed 12 becomes much greater than what can be achieved with the use of crushed stone as is employed by the prior art. The net result is that a beam effect is obtained with the materials contained within the casing reacting against atmospheric pressure.
After the roadbed 12 has been formed, evacuated and hermetically sealed as set forth above, a suitable road surface is formed atop the roadbed as by, for example, pouring a layer of concrete to form a slab 18 as generally depicted in FIGS. 1 and 6.
Depending upon the constituency of the earth where such a roadway is being constructed, there may be instances where considerable care would have to be exercised when replacing the excavated earth to avoid puncturing the elastomeric sheet or liner 44. Accordingly, to assist in avoidance of such punctures, the elastomeric sheet may be first lined with such materials as, for example, sand, sawdust, building paper, old newsprint or straw (as generally depicted by the layer 70 in FIG. 6) since none of these materials will decompose after evacuation and each will compress sufficiently to offer adequate strength.
In view of the above, it can be seen that the invention provides a roadway having an extremely rigid roadbed which is substantially free from water vapor thereby not being susceptible to upheavals due to the freezing and expansion of moisture as in the prior art.
In practicing the method herein disclosed, it should be apparent that it is not absolutely necessary to first form a trench or ditch 14. That is, the roadbed 12 may be formed, as generally described above, and placed atop the surface of the earth after which, as by backfilling or grading operations the dirt or earth can be brought up against the sides of the roadbed 12 and graded to a height sufficient to, in effect, place the lower wall 28 of the casing 46 below the resulting frost line. This, of course, becomes of major benefit where a roadway is being constructed through hilly terrain and it is desired to reduce the relative heights of the peaks and valleys of the general path of the roadway. This is, some of the dirt removed in cutting away a part of a hill can be graded downwardly and about a roadbed 12 formed atop the surface within the adjoining valley.
Even though it is believed apparent, it should nevertheless be made clear that the invention is not limited to the use of sheet-like elastomeric material as at 44. On the contrary, it is also contemplated that such material could be preformed so as to generally define a flexible or collapsible countainer having already formed end walls, side walls and bottom wall thereby reducing the number of seams to be hermetically sealed. Such could be made in modular lengths if desired.
Further, although the invention has been presented as solving a long standing problem, namely, the damage done to prior art roadways due to roadbed upheaval arising out of the freezing and thawing of moisture within the roadbed, the invention can, nevertheless, be practical in geographical areas which are not subjected to freezing conditions. In such situations it would not be necessary, for purposes of avoiding surface upheavals due to frost, to dig or otherwise provide a ditch or trench for the reception therein of the roadbed 12. In such situations the roadbed 12 could be formed as previously described and placed atop the surface of the terrain. The benefit derived would be the rigidity of the evacuated roadbed 12. That is, it would continue to act as a rigid beam because of the atmospheric pressure continually holding all of the particles forming the filler of the roadbed, in a compacted condition.
Although only one preferred embodiment and selected modifications of the invention have been disclosed and described, it is apparent that other embodiments and modifications of the invention are possible within the scope of the appended claims.
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