US2666296A - Dam - Google Patents

Description

Jan. 19, 1954 A. COYNE ET AL 2,666,295

DAM

Filed Dec. 11, 1951' 5 Sheets-Sheet l Jan. 19, 1954 A. COYNE ET AL DAM 5 Sheets-Sheet 2 Filed Dec. 11, 1951 Jan. 19, 1954 A. COYNE- ET AL DAM 5 Shee'h-Sheet 3 Filed Dec. 11 1951 Jan. 19, 1954' A. COYNE ET AL DAM 5 Sheets-Sheet 4 Filed Dec. 11 1951 Jan. 19, 1954 A. COYNE ET AL DAM 5 Shee'ts-Sheet 5 Filed Dec. 11, 1951 Patented Jan. 19, 1954 UNITED STATES PATENT OFFICE DAM Andr Coyne, Jean Ghin, and Jean Bellier, Paris, France Application December 11, 1951, Serial No. 261,111

Claims priority, application France December 11, 1950 Claims. (01. 61-30) 1 While a great variety of types of concrete dams are known the greater number thereof can be grouped in three categories, namely the gravity type, the thin-arch type and the intermediate or thick-arch type of dam.

It is likewise known that according to an elementary theory it has long been attempted to of the arch, at the arch-springs, being definitely directed downwards, at an angle a more or less marked depending on individual instances. Substantial economy can be obtained by taking this effect intoconsideration in designing the dam, Whereas if said effect is not taken into account damdesigns are obtained in which the volume of masonry is unduly increased Without in any way enhancing the safety factor of the structure, and sometimes even impairing it.

It is comparatively-easy to make allowance for the force of gravity alone, even though the calculation is not strictly accurate. It will easily be understood, moreover, that the heavier the arch, the more marked will be the degree to which the forces generated by water pressure upon the extrados of the arch'should be deflected in. the downward direction.

This quite naturally leads to the idea of the thick-arch type of dam whose essential characteristic is quite clearly indicated by its name. It. is also referred to as the intermediate type, becauseits type of stability partakes both of that of the gravity dam and that of the thin-arch dam as defined above. This type of structure has wide popularity and its reliability is high. Against it however one can hold its very volume, which in all cases is comparatively high and becomes quite excessive in the case of very large dams. Moreover, this type of dam design is not economical, if not quite impracticable, where the valley is too wide, at any rate in the vicinity of the level of the impounded water.

It is the object of the present invention to provide a type of dam structure which, whilst it possesses the essential advantages of the thinarch type dam, further takes advantage of the inherent weight of the dam to provide stability, as do the gravity or the intermediate types of dams.

A dam structure according to the invention comprises an upstream Wall or screen of substantial weight but moderate'thickness which, over part at least of its length, takes support against the convex side of an arch extending continuously throughout its height, said arch being cut on the downstream side along a plane or surface inclined in the downstream direction, the stresses, including that due to theweight of the materials, being transmitted from the upstream wall to the supporting arch through spaced partitions or buttresses. The three constituent elements of a dam according to the invention, viz. the wall, the buttresses and the arch are made of the same materials and there is no break in continuity between the screen and the buttresses, nor be tween the buttresses and the arch, unlessit be temporarily for purposes of construction or mutualkeying of theelements. Any such provisional joints which maybe found necessary are sub-- sequently blocked at the time the dam is put into service, by any one of-th'e many methods provided for similar purposes by the known art, it being understood that such methods should be so applied as to take full advantage of all the forces considered, andchiefiy gravity.

In brief, adam designed according to the invention can be defined in its essence as deriving from an intermediate or thick-archtype of dam.

in which the upstream facing is hardly if at all curved;. the downstreamfacing is onthe other hand an arch. cradle having a marked curvature, said cradle being cut off at its top by a plane sloping downstream and, passing through the coping ridge of the upstream-facing; said thickarch dam being furthermore recessed by means of shafts extending as far as a short distance from the upstream facing, the length of which shafts in the downstream direction increases from the centre towards the banks of the valley and said shafts being separated by comparatively thin partitions:

According to another aspect, a dam according to the invention can be defined as deriving from a conventional triangular gravity dam of straight or near-straight configuration, said gravity dam being doubly recessed, in. the first place upstream,

somewhat in the core of the concrete structure,

by shafts similar to those defined above, and in the second place, downstream, by a vertical or inclined cylindrical sector or ungula the arris of which extends along'the base line of said gravity dam and which at the crown approaches the upstream facing at the crown throughout its entire height or at least in its upper portion.

The apparent complexity and at the same time the actual simplicity of the above definitions bring into evidence the originality of the invention. Moreover, they imply that stability is achieved by a combination of all three forces which are naturally brought into play excluding none namely the pressure of the water, the inherent weight of the dam and the reactions of the arch.

Structure according to the invention will be easy to erect in the usual valleys in which the sides slope uniformly or nearly so. However, it may also occur that a dam has to be built to a large height across a valley which is deep and the banks of which, as will often occur in such cases, show a marked and sudden change in slope at a level below that of the water to be impounded. In other words, the cross-sectional configuration of such a valley includes: a lowermost section in the form of a canyon or gorge which may be more or less narrow, and an upper section in which table-lands, which may be very protracted, border the gorge on one or both sides. A dam according to the invention is indicated as being especially well adapted, and economical for use with valleys of this shape. The arch-springs of the supporting arch are steadied against the sides of the canyon, while the upstream wall is extended laterally on the table-land or tablelands by wing dam structures of conventional design.

A dam structure according to this invention can also be repeated several times across a very wide valley, with the constituent elements joining one another. in this case, the thrusts from the adjacent arches combine into resultant thrusts directed on the one hand in the direction of the valley and on the other hand downwardly, owing to the efiect of gravity. There is obtained in this way a type of buttressed dam of particularly large weight which is more specifically described by the second one of the previously-given simplified definitions.

The dam composed of contiguous elements as described in the foregoing paragraph can also be associated with a buttressed dam of conventional type, especially a multiple-arch dam, said buttressed dam forming the base of the composite structure and the dam according to the invention being erected above and upon the same buttresses and thereby providing a very satisfactory solution to the difilcult constructional problems of erection, stability as well as aspect of the capping and the underlying sections of concrete, and also the use of the capping as a highway.

The ensuing description made with reference to the accompanying drawings, given for purposes of illustration and description but not of limitation, will provide a clear comprehension of the manner in which the invention may be performed. Any features that may stand out either from the disclosure or the drawings should of course be cont plane of section being indicated by lines IVIV of Fig. 5,

Fig. 5 is a section of the dam shown in Fig. 4 on line V-V,

Fig. 6 is a section on line VIVI of Fig. 5,

Fig. 7 is a section on line VIIVII of Fig. 4,

Fig. 8 is a plan view of a conventional archtype dam the impounding capacity of which has been increased by the adjunction thereto of an additional upper structure which converts it into a dam according to the invention,

Fig. 9 is a section on line IX-IX of Fig. 8, showing the structure in elevation from the rear,

Fig. 10 shows in perspective one possible form of a dam according to the invention including a plurality of contiguous elements across a very wide valley,

Fig. 11 similarly shows a dam according to the invention erected as a capping section for a conventional dam of the multiple-arch type.

The dam structure illustrated in Figs. 1 and 2 comprises an upstream facing or wall I here shown flat and with a certain degree of batter; it should be understood however that said upstream facing might be designed to some suitable shape other than flat and might be vertical. The upstream facing is subjected to the pressure or" the impounded water. This facing or wall is supported by buttresses 2 extending downstream and supported in turn against an arch 3 continuous throughout its height and having its top out along a plane or other surface dipping in the downstream direction along the line AB of Fig. 2.

The screen i, buttresses 2 and arch 3 constitute a unitary structure which are made integral during or after construction. For example, if the dam is erected in vertical monoliths according to the conventional method, each such monolith would ultimately preferably comprise one voussoir of the arch, one buttress and the adjoining portion of the wall.

The arch 3 rests on the bottom of the thalweg and abuts laterally against the banks, with the possible-but by no means necessary-interposal of abutments or bed-blocks adapted to distribute the transmitted forces, should the qualit of the fundation soil or the lay of the land require this.

To either side of the section supported by the arch 3, the wall I may be extended by dam elements of any desired type.

It is desirable for various reasons, such for instance as considerations of appearance or for facilitating the joining of the wings to the central portion or further for simplifying the layout.

of the building yard, that the said wings constitute an extension or" the wall l and of its buttresses, which latter, designated 2a in Fig. 1, will then rest directly on the ground.

As can be seen from Fig. owing to the integral joining of the wall with the arch through the buttresses, the hydrostatic pressure P acting on wall 5 is deflected under the action of the weight or" the wall, buttresses and arch. until it assumes a general direction approximately indicated by the arrow P, dipping at an angle that will depend on the respective magnitudes of the component forces. Because of the inclination of P, the pressures thus transmitted from the arch to the ground lie under all circumstances at an angle to horizon and it may be seen that the design of said arch may be calculated with a satisfactory degree of approximation by dividing it into a' number or" superimposed ring segments 7 lying in general planes inclined at the said angle in the downstream direction. Of course, any

other suitable mathematical expedient fmay. usedin designing the arch.

While in the form of construction, shown in Fig, 1,, the wall I is separate from the arch 3 throughoutits length, it maybe desirable. with a viewto reducing, the total bulk of materials used in the structure, to use a part of the arch in the area adjacent to its. crown. asthe wall for sealing the valley. Fig. 3 illustrates one example of such a construction. In the central portion, the extrados of arch 3 serves the function of wall I. To either side, the wall I isseparate from the,

arch against which it takes support, at least in the area where said arch is present behind it,

through the medium ofrthe buttresses 2, which may be-though they not necessarily are-pro:

vided as shown with flaring upstream ends 5. In

the end areas where the support of the arch 3 is;

In this case as in that of Fig. 3, thearch 3, near its crown, constitutes a part of the impounding wall. In the lower section of the dam, that is in the restricted part of the valley, as shown in Fig. 7, this arch by itself provides the entire dam. The arch is substantially vertical and is designed, in the fashion of usual arch-type dams, with a thickness varying according to its radius of curvature and of the pressure to which it is subjected, without it being ordinarily necessary to increase the thickness in order to increase the weight of this part of the dam, because it already is sufiiciently loaded by the weight of the overlyingstructure.

In the upper portion, the arch is designed with a downstream dip, as is conventional with recessed gravity dams, in order to secure a number of advantages one of the major of which is the production of an overload directed vertically, and therefore enhancing stability, equal in magnitude to the water pressure component exerted on the facing.

Outside from the central portion, the wall I is similar in profile to the crown of the arch, as shown in Fig. 6, which further shows the small surface area, and hence low volume, of the buttresses 2. The general outline of the wall I and consequently that of the crest is straight; however, it may be provided with broken or curved portions if found suitable for adaptation to local conditions. Such is the case illustrated for example in Fig. 8 which relates to another specific application of the present invention.

This construction is particularly useful in connection with the raising of existing arch-dams in the very frequent case where conditions are such that, if it were merely attempted to raise the existing arch, there would be no way of abutting the ends of the raised arch against the sides of the valley.

Thus, in the example shown in Figs. 8 and 9, the conventional arch-type dam 1 is shown as sealing the end of a valley. It would be impossible purely and simply to raise the dam l for want of suitable abutment surfaces. Accordingly the arch is raised by means of the structure 8 which may be designed and constructed as an arch of the inclined ring type. In its central part, this .arch'B seals the valley and it is laterally extended by wing walls 9 supported through but-- tresses '2 against the composite arch .'l-8 and through buttresses directly against the ground. As in the case of Figs. 4 to 7, the lower part of this dam. can be considered as an ordinary archdam, whilst the upper part is a dam of the novel type provided by this invention.

The arrangement shown in Fig. 10 would apply to the case of a very wide valley across which the erection of a single-span supporting arch would not be economically feasible. The total width to be crossed may then be divided into fractions and a plurality of contiguous supporting arches 3 provided, each of which receives, as shown in the previous instance, the buttresses that support the impounding wall.

As shown in Fig. 11 this arrangement can be applied at the top of a conventional multiple arch dam l0 abutted on buttresses ll, thus solving among other problems that relating to the upper termination of the arches, in that the upstream wall I of the invention prevents the access of water to the top of the buttresses.

From the above description and the drawings, there result a number of advantages in addition to those previously defined, a non exhaustive list of which can be given as follows:

(a) The weight of all the parts of the structure, and not only that of some components thereof, is used for stability, thereby affording a definite saving in material.

(b) The crest of the structure can be set out I as a straight line, without having to forego the advantages of a curved arch dam in the lower parts of the structure adapted for supporting high water pressures.

(c) As compared to a conventional dam of the recessed gravity type, for example a buttressed dam having as its contour the triangle CDE of Fig. 2, the necessity of providing foundations for such buttresses :is averted just in that area where, owing to the high transverse gradient of the ground, the provision of such foundations would be difficult and expensive. Instead of such imperatively located buttress foundations, it is now necessary to provide only the foundations of the arch, easier to make and the locations of which can be selected with greater freedom.

(d) In that the arch of a dam according to the invention stops short of the elevation of the impounded water, and therefore extends only to an elevation at which the valley still remains narrow, it may generally be designed with shorter radii than a conventional arch-dam in which the radius of curvature is usually imposed by the much greater width of the valley at the crest elevation. Thus, the thickness remaining equal, the strains in the materials are less.

Moreover, the forces due to water pressure are applied to an arch according to the invention through the medium of buttresses, and hence are all parallel, whereas in a conventional arch dam, said forces are normal to the extrados, converging towards the centre of the arches. The catenary curve of elastic forces is therefore more widely open, whereby it becomes possible, without increasing the strain in the materials, either to increase the radius and decrease the developed length with thickness retained equal, or to reduce the thickness while retaining an equal radius.

The strains in the upper part in any case remain comparatively low, as in gravity type and recessed gravity type dams.

It will be understood that many modifications may be made in the improved dam design and construction illustrated and described, without exceeding the scope of the invention as defined by the claims.

In the claims, the expression upstream will be used to refer to the side of the dam directed towards the body of impounded water, and the expression downstream to the opposite side.

What we claim is:

1. A concrete dam comprising a substantially flat impounding wall, an arch at least a portion of which extends downstream of said wall, the concave side of said arch facing downstream, and spaced rigid interconnecting means between said wall and said downstream portion of the arch, said wall, said arch portion and said interconnecting means forming a monolithic structure, whereby all the mechanical forces, including that of gravity, to which said wall is subjected, are transmitted from said wall to said arch.

2. A concrete dam comprising a substantially fiat impounding wall, an arch at least a portion of which extends downstream of said wall, the concave side of said arch facing downstream, and the upper face of said arch sloping in downstream direction and spaced rigid interconnecting means between said wall and said downstream portion of the arch, said wall, said arch portion and said interconnecting means forming a monolithic structure.

3. A dam as claimed in claim 2, wherein the rigid interconnecting means form buttresses extending generally perpendicularly to the impounding Wall.

4. A dam as claimed in claim 2, wherein the impounding wall is at an angle, in the upstream direction, with the vertical plane through the top thereof.

5. A dam as claimed in claim 2, wherein the impounding wall extends transversely beyond at 4o least one end of the arch, said extension being buttressed directly on the ground.

6. A dam as claimed in claim 2, wherein the crown portion of the arch merges into an intermediate portion of the impounding wall and the parts of said arch on both sides of said crown portion are connected to the impounding wall through buttresses which extend generally perpendicularly to said wall.

7. A dam as claimed in claim 6, erected across a valley having a narrow lower section and a widened upper section, wherein the arch is adapted, at its lower part, to impoundingly seal said valley in said narrow section thereof and the wall is adapted to impoundingly seal said valley in said widened upper section thereof.

8. A dam as claimed in claim 6, wherein the crown portion of the arch merges into the thickness of the impounding wall, whereby the impounding surface of the dam is flat throughout.

9. A dam as claimed in claim 6, wherein the crown portion of the arch protrudes from the flat impounding surface of the wall, whereby the impounding surface of the dam includes an intermediate convex part and a fiat part on either side of said convex part.

10. A dam as claimed in claim 2, wherein the arch is entirely located downstream of the wall and connected thereto through generally parallel buttresses extending substantially perpendicularly to said wall.

ANDRE coYNE. JEAN GE'HIN.

JEAN BELLIER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 374,378 Strong Dec. 6, 1887 1,610,570 Milburn Dec. 14, 1926 1,807,358 Wartemann May 26, 1931

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