US2664714A - Dam - Google Patents

Description

Jan. 5, 1954 u. FINSTERWALDER ET AL 2,664,714

DAM

Filed Jan. 15, 1952 horizontal foundation.

Patented Jan. 5, 1954 DAM Ulrich Finsterwalder and Philipp Ebert,

Muenchen, Germany, assignors to Dyckerhofi & Widma'nn Kommanditgesellschaft, Muenchen, Germany, a German company Application January 15, 1952, Serial No. 266,468

3 Claims. 1

This invention relates to an arched or vaulted retaining wall for dams.

It isthe object of the present invention to improve the arch effect especially in low dams and dams of average height so as to transmit a larger part of the hydraulic pressure to the slopes of the valley by such arch effect.

The invention will be best understood and further objects will appear from a study of the following detailed description taken in connection with the accompanying drawing, with the understanding, however, that the invention is not confined to any strict conformity with the showing in the drawing, but may be changed and modified as long as such changes mark no material departure from the salient features of the invention as expressed in the appended claims.

Fig. 1 is a development of the dam, viewed from the air side,

Fig. 2 is a top plan view of the dam,

Fig. 3 is a section on line III-III in Fig. 2, on a larger scale, and

Fig. 4 is. a section on line IV-IV .of Fig. 3, on a still larger scale.

Solid dams are built substantially on two different constructional principles, i. e. either as a gravity dam or as an arched or vaulted dam. The gravity dam hangs over its foundation, so to speak, while the vaulted dam bears on the slopes of the valley. Since in vaulted dams the forces are transmitted by vault pressure to a solid foundation formed by the slope of the valley, such dams have a higher degree of safety than gravity dams. The latter is exposed to shearing and bending stresses and on principle is seated on a In spite of these undeniable advantages arched dams can be used only where the local conditions are particularly favorable. This is due to the fact that in order to ensure the setting up of an arch effect, elastic yielding of the arch is required which is impeded by the connection of the dam with its foundation. Thus an arched dam acts only partly as an arch, while partly its acts as an arm hanging over the foundation as in case of a gravity dam.

Moreover, the crown of the dam is stressed to a small extent only by the hydraulic pressure acting upon it and, therefore, will be flexed by a small amount only in the direction of the hydraulic pressure while much larger deflections are occurring, for instance, in the middle of the height of damming. Thus the arm projecting from the ground is supported by a bearing at the top end. As a result, bending stresses are caused in the central part of the dam, producing tensile 2 stresses on the air side of the dam, and at the point of fixation bending stresses with tension on the water side are set up.

On the point of fixation the tensile stresses can be avoided by an enlargement directed towards the air side which enlargement is shaped in accordance with the course of the moment taken about the point of fixation. In the central point of the dam the tensile stresses due to bending can be taken only by a thickening extending over the whole height of the wall. This, however, would again act to restrict the total vault effect, so that in the end a wall or dam laterally projecting from the foundation would again be obtained. These difficulties are avoided by my novel construction in which through-gaps are provided in the top part of the dam, at suitable intervals, whereby this part of the dam is prevented from transmitting compressive stresses in a peripheral direction and hence cannot act as a vault.

The extension of the gaps in a vertical direction is defined by the condition that the upper part of the dam has to act as a gravity dam with respect to the hydraulic pressure. It was found to be particularly advantageous to provide gaps having a vertical extension equalling about the 1.5 fold amount of the thickness of the wall.

By the provision of the radially extending gaps according to the present invention the hydraulic pressure bearing against the upper part of the dam and the appertaining bending moment is introduced into the vaulted dam at the upper edge of the same. Bythis stress the dam is bent backwards at this spot in a favorable manner whereby the moments setting up bending stresses on the air side in the central part of the dam are substantially reduced. Moreover, a vertical compression is exerted on the vaulted part of the dam by the part of the dam acting as a gravity dam, whereby the capacity of taking bending moments is increased.

Referring now to the drawing, it will be seen that 2 and 3 are the abutments by which the wall bears on the two slopes of the valley. The arched retaining wall or dam is vertical and is of uniform thickness in its crown I and middle part 4. Only the base part 5 is enlarged and constructed in the form of an abutment of corbel in such a way that the bearing pressure in the filled state of the basin is directed perpendicularly to the bottom joint.

Basing on the knowledge that an arch effect would be detrimental in the upper part of the wall, the head part I of the wall is provided with gaps or slits 6 which are radially directed, i. e.

they extend in the direction of the radius of curvation of the dam.

Preferably the gaps are spaced from each other by intervals corresponding to the conventional width of the sections of work provided for laying the concrete in building a retaining dam, as shown in Fig. 2. The gaps may be formed by conventional methods in working the concrete. In a vertical direction the gaps B extend over a height corresponding approximately to the 1.5 fold amount of the thickness of the wall at the crown, Figs. 1 and 3. 7

It will be understood that bythese gaps 6 the hydraulic pressure loading on the upper part of the wall and the appertaining bending moment are introduced into the arched wall at the upper border of the same. Thus the wall isbent back at this point in a favorable manner, whereby the moments producing bending stresses in the middle part of the Wall on the air side are substantially reduced.

The gaps 6 are stopped or made tight against passage of water in the manner which is known for such purposes. In the example illustrated the packing of each gap comprises a strip 1, e. g., of copper sheet extending over the whole height of the gap. The copper sheet may consist of several interconnected parts, if desired.

'Thepacking strip 1 has a fold 8 projecting into the gap 6 while its bent ends are anchored in t wall is prevented from transmitting any compressive stresses and hence from acting as an arched wall, the height of the same is theoretically reduced by the height of the gaps. In

this reduced height the valley to be barred by I .the dam as a rule is substantially narrower than at the top of the dam, so that the Wall can be made with a smaller radius. The upper part of the dam acts as a gravity wall. Its horizontal thrust acts to bend the upper zone of the wall to the air side in a favorable manner, whereby the maximum bending moment in a vertical direction, with tension stress on the air side, is reduced and displaced downwards to a point or plane where the load bearing thereon is heavier.

While the invention has been described in detail with respect to a now preferred example and embodiment of the invention it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended, therefore, to cover all such changes and modifications in the appended claims.

What is claimed is:

1. In an arc-shaped dam particularly for the control of flood waters a plurality of vertical spacedly adjacent recesses in the crest portion of the dam, said recesses extending in the radial direction of the dam crest from its one face to its opposite face, the size and the number of said recesses being controlled to prevent the dam crest to transmit compression stresses in the peripheral direction of the dam and means to close the said recesses.

2. An arc-shaped dam according to claim 1, said recess closure means consisting of resilient metal plates vertically extending through the height of said recesses from the dam crest to thebottom thereof and traversing the said recesses.

3. An arc-shaped dam according to claim 2, the height of the said recesses equalling to 1.5 times the thickness of the dam crest.

ULRICH FINSTERWALDER.

PHILIPP EBERT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,529,141 Danel Nov. 7, 1950

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