US2047197A - Revetment - Google Patents

Description

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/nVen/of HN l?. fPD V55 l 15% o //O/Wy Patented July 14, 1936 UNITED ys'r'Al'rEs PATENT' oFFicE BClaims.

This invention relates generally to the protection revetments such as those used on levees, river banks, canals and irrigation ditches, and particularly to revetment mats and the method of making. and applying the same to the levee or bank, or other earthen surfaces exposed to the erosive action of water.

In protecting mats employed upon the banks of streams, levees and the like, metallic reenforcements which may bein the" form of woven wire or wire cables have heretofore been employed. Such a mat is disclosed in the prior copending application, Serial No. 646,471, f iled December`3, 1932, .of which. this application is the breaking or cracking of the matrix in which they are embedded they are exposed to corrosion 'and often becomefso seriously corroded that portions of the matrix break away and large sections of the earthen surfacesare exposed to erosion. Indeed, such metallic reenforcements may in some cases, because of expansion and contraction, actually cause such breakingof the mat.

'I'he object of the present invention, generally stated, is to y.provide -a revetment mat whichl is so pliable that it will readily conform itselflto .the contour of the earthen surface upon which lt is launched, but which will later beco'ie of such character as to resist the erosive action of a hard revetment mat provided with a reenforcement of such character that the mat will `not be cracked or broken by expansion and contraction of the reenforcement.

A more specific object of this invention is to 59 provide a revetment mat wherein the matrix is hard and resistant to erosion at normal atmospheric or watertemperatures but capable of being softened upon heating so as -to be workable at a temperature below that which will injure anN organic brous reenforcing material employed in connection therewith which has been precoated with a protecting material.

Other objects will become apparent to those 60 skilled in the art when the following description in part a continuation. Such metallic reenforce-j' ments, however, have the disadvantage that upon AnotherA object of the invention is to provide is read in connection with the accompanying drawing, in which':

' Figure 1 is a sectional view of a slab of reenvforced mat constructed in accordance with the present invention; 1

Figure 2 is a perspective view of an openwork material such as burlap which in accordance with one embodiment is used as the reenforcing material ofthe present invention;

Figure 3 is a perspective view of an openwork of cords or ropes of organic material such as #'cotton, hempfjute, grass, sisal, or the like, employed as the reenforcing material in accordance with anotherembodiment of this invention.

In accordance with the present invention, generally stated, a revetment mat may be formed having a -matrix of a suitable water and erosion resistant material which, although capable of being softened is,v nevertheless, hard at normal atmosphericor water temperatures. The matrix 20 may be composed of an asphaltic substance together with a suitable quantity of mineral aggregate. According to this invention such a matrix may be reenforced by an organic ibrous material 'woven into a network or fabric which is suill- 25 ciently open thatthe `binder may flow through the interstices, and embed it in the matrix. Accordingly, in the selection of the binding material, such as asphaltum, care should be exercised that the bindermay be softened so as to become workable ata temperature below that which will injure theeenforcing organic material which has been/coated by a protecting, material. After the organic reenforcing material is embedded in. the asphaltic or other matrix, the resultant mass may be launched into the water and anchored to the bank even while it remains in a soft and pliable condition and thus better conforms itself to the irregularities of the bank. However, when the mat is cooled to normal atmospheric or water temperatures it will become hard and resistant.

The organic fibrous reenforcing materials which may be used in accordance with the present invention may consist of loosely woven bagging such as' burlap or even loosely woven textile fabrics made from other materials as illustrated in Figure 2. Moreover, rope formed of cotton, jute, hemp, sisal, or grass may be tied together so as to form the network such as that illustrated in Figure 3. Such an organic brous openwork may be treated as by being dipped in a suitable preserving uid so as to make it water and heat resistant before it is embedded in the matrix.

. Asphaltum is a suitable preservative for this purpose and to secure the desired penetration conveniently it may be applied either in the form of a water emulsion or in a suitable solvent.

When such an organic fibrous material is used as the reenforcement in a revetment mat, it will be understood that in addition to the mat being 00 extremely flexible so that it may readily conform itself to irregularities in the bank, the reenforcement is not subject to corrosion and deterioration upon the cracking of the matrix as frequently corporated as in a pug mill and, if the temperav ture of incorporation is high enough to injure the reeenforcement, the mixture is cooled until a temperature which will not injure the reenforcement is attained. This is generally 150 F. or below.

As a specic illustration of a practical embodiment of the invention, the aggregate may be sixty-six per cent of river sand and other mineral, twenty-two per cent of loess, or the material of which the bluffs along the lower Mississippi River are composed, and twelve per cent of asphaltum. In order to weight the mat the aggregate employed may contain a heavy mineral such as barytes or hematite.

The asphaltum binder material employed may be one which is hard at ordinary temperatures and little affected by water or climatic temperature-changes, but which may be softened at about -150 F. Which temperature is not injurious to the vegetable reenforcement.

The asphaltum employed should not contain such a high percentage of volatiles that it will not retain its binding qualities but should no t be brittle. A good test for determining the suita- Ibility of the asphaltum is the A. S. T. M. penetration test under which an asphaltum having a penetration of between 40 and 100 is satisfactory as to binding properties. This penetration may be obtained by driving oi the lighter volatiles as in the vacuum distillation until the desired point is reached.

A typical example of asphaltum suitable for use in accordance with this invention may have the following characteristics:

softening point -155 F. Specific gravity min. 1.01 Ductility at 32 F.-.25 cm. per min 3.5 cm. min. Ductility at 77-5 cm. per min 60 cm. min.

Penetration 32 F. 200 gr. 60 sec 10 min. (A. S. T. M.)

Loss on heating 50 gr. 5 hrs. 325 F 0.15 max.

Residue penetration at 77 F 80% min.

It is the intention of this process to use a reenforcing material made of vegetable fiber, and

,to permeate this ber with a preserving fluid like emulsied asphaltum, which can be applied at low temperatures, whicll will not injure the fibers. The permeated fiber is then used in making the mat by embedding it in the hot matrix.

It is also contemplated to use when necessary as aggregate, substances such as barite or hematite, which have a greater specific gravity than sand or loess. The occasions upon which this heavy material should be used, depends upon the swiftness of the Water currents. l

On a platform or other surface of suitable size the asphaltum aggregate mixture may be formed into sheets or slags While the asphaltum is maintained at a workable temperature. The platform may be dusted over with limestone dust, talc or Portland cement or covered with paper or cheese cloth in order to prevent the asphaltum from sticking thereto. Across the platform the reenforcing material may be spread and on to this the desired quantity of the asphaltum aggregate mixture may'be spread. Enough of the asphaltum aggregate mixture may be spread to form a sheet or slab of the desired thickness and the mixture may then be compacted about the reenforcing material, as by tamping or rolling to an extent suicient that the mixture entirely surrounds and encloses the reenforcements so as to form a waterproof coherent mass. It will be understood that during al1 these operations the temperature of the asphaltum aggregate mixture is maintained about the softening point for the asphaltum and sufficiently high that the asphaltum may completely coat the reenforcing material so as to protect the same from deterioration but the temperature should be controlled so that it is not injurious to the reenforcing material.

Before the sheet or slab thus formed has cooled below the hardening point for the asphaltum and preferably while the same is at a temperature considerably above that point, the sheet or slab may be launched or applied to the levee or stream bank. In accordance with the present invention the temperature of the slab or sheet is preferably at this time sufficiently above the softening temperature for the asphaltum that the slab or sheet may sink into position beneath the water and conform itself to the contour of the stream bank before hardening.

When the aggregate employed contains a heavy mineral such, for instance, as a class including barite and hematite, it is apparent that the sheets or slabs formed in accordance with the present invention may be caused to sink beneath the surface of the water without the use of extraneous means, the specific gravity of the mineral being sufficient to sink it and maintain the same against displacement even by swift currents. It will be understood, of course, that the mats may be formed of lighter minerals and the sheets or slabs suitably anchored or otherwise secured to the stream banks to prevent displacement.

It will be understood that the amount of asphaltum may be varied in accordance with the requirement of a. particular stream and the size of the aggregate employed, as from 5% to 25% by weight of the mat. The thickness of the mat may be varied from one-half to six inches, depending upon stream conditions and the character of materials employed.

From the foregoing description it is apparent tha'tthe present invention contemplates a method of protecting banks wherein the revetment mat employed is of such composition as to effectively resist the erosive action of the sand carried by a stream and that the revetment mat of the present invention, although sufciently pliable to conform itself to the contour of lthe stream bank at the time of launching, will imme- 7 5 diately become suiliciently hard to be'resistant. It is apparent that many modifications of the revetment mat and the process of making and applying the. same lhereinbefore described will occur to those skilled in the art which will not depart from the spirit of this invention. It is to be distinctly understood, therefore, that the invention is not limited to the specific details hereinbefore described for the purpose of illustration, but that such modifications and the use of such individual features and sub-combinations of features as do not depart from the spirit of this invention are, although not speciiically described herein, contemplated by and within the scope of the appended claims.-

Having thus described the invention, what is claimed is:

1. A revctment mat, comprising, an organic fibrous reenforcing material embedded in matrix of material which is resistant to erosion.

2. A revetment mat, comprising an organic fibrous reenforcing material embedded in matrix of a plastic material which at normal atmospheric temperatures is hard and resistant to erosion.

3. A revetment mat, comprising an organicl brous reenforcing material embedded in matrix of normally hard asphaltum which may be softened by heating to a temperature which will not injure the organic reenforcing material.

4. A'revetment mat, comprising an openwork 5 fabric embedded in matrix of material which is resistant to erosion.

5. A revetment mat, comprising a. net work of organic fibrous material embedded in matrix of material'which is resistant to erosion. 10

6. A revetment mat, comprising burlap em-Y bedded in matrix of material which is resistant to erosion. l

'7. A revetment mat, comprising a net work of rope embedded in matrix of material which is 15 resistant to erosion.

8. In the art of making revetment mats, the

process comprising, treating an organic fibrous openwork with a preservative, .and heat resistant l substances maintaining an asphaltum aggregate 2o mixture in softened condition at a temperature below that which will injure the fibrous openwork, embedding the fibrous openwork in the mixture and thereafter hardening the asphaltum aggregate mixture. x 25 JOHN R. FORDYCE.

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