US788885A - Dam. - Google Patents

Description

PATENTED MAY 2, 1905.- W. L. CHURCH.

DAM.

APPLICATION FILED APR. a, 1904.

Patented May 2, 1905.

VV'ILLIVAM L. CHURCH, OF BOSTON, hlASSACItlUSETTS.

DAlVl.

SPIECIIICTION forming part of Letters Patent No. 788,885, dated May 2, 1905.

Application filed April 8, 1904. Serial No, 202,153.

To (all 107mm/ 7115 mln/y colte/7mm Be it known that I, WILLIAM L. CHURCH, of Boston, in the county of Suffolk and State of Massachusetts, have invented certain new and useful Improvements in Dams, of which the following is a specification.

This invention has the twofold object of increasing the stability and decreasing' the cost of dams, the said objects being attained, primarily, by the employment of a construction whereby the water liowing over the lip of the dam is in part retained, preferably in a descending' series of reservoirs, and adds its weight to that of the material of the dam. in this way a reduction of cost is attained, because in place of concrete or masonry weighing, say, one hundred and fifty pounds per cubic foot and costing from five to nine dollars per cubic yard there is partially substituted a greater cubic volume of water weighing 62.5 pounds per cubic foot, but costing nothing. Owing, further, to a better disposition of the material and giving' it increased leverage in its parts, owing to its more open or extended structure, in order to minimize strains upon it, there is a decrease in cost.

The invention consists in the novel features of construction and arrangement and in the novel method of filling' andretaining full the cells or chambers of a multicellular dam.

Of the accompanying drawings, Figure 1 represents a longitudinal vertical section of a dam constructed according to my invention. Fig'. 2 represents a section on line 2 2 of Fig. 1. Fig. 3 represents a plan View of one end of the dam, showing' the well for filling and draining the cells. Fig. 4 represents a section on line 4 4 of Fig. 3. Fig. 5 represents a plan view showing a modification. Fig. 6 represents a diagrammatic section to illustrate the strains to which the parts of the structure are subjected.

The same reference characters indicate the same parts in all the figures.

The term longitudinal may be considered as referring to the direction of pressure and iiow of the water and transverse as referringl to a direction across the flow of the water.

The preferred construction of the dam is that of a cellular' monolith, the term monolith implying a concrete or masonry construction, steelreinforced, if desired, as this is the most practical material for construction, although it will be understood that other materialsv-such, for instance, as wood would in general be considered equivalents.

1() is the base of the darn.

11 is the upstream-wall for receiving the pressure of the pond, and 12 is the toe of the dam, securely stepped in the bed-rock on the downstream side of the wall Il.

13 13 are a series of cells whose transverse walls are arranged step-like in a descending' series at dilierent levels, said cells being' formed by a series of longitudinal buttresses 14, extending' from the main wall 11 to the toe of the dam, and a series of transverse Vertical intersecting walls 15 15.

The material of the walls is preferably concrete reinforced by horizontal rods or bars 16 in the transverse walls 11 and 15 and vertical bars 17 in the buttresses 14, said bars being preferably some one of the well-known forms of self-locking bars. l do not wholly limit myself to a steel-reinforced construction. One alternative method of obtaining strength in the transverse walls would be to crown or arch them in an upstream direction, as shown at 15 in Fig. 5. As a supplementary means of securing additional stability I have shown the rear wall 11 anchored to the bed-rock or dam-foundation 40 by means of vertical anchor-bars 18, embedded in said wall and in a dovetail footing-wall 19, keyed into the bed-rock and made integral with the walls of the dam.

20 is a sloping apron integral at its upper edge with the crest of the rear wall 11 and at its lower' edge with thc toe 12 of the dam, said apron preferably consisting' of longitudinal slabs located between the buttresses 14 and integrally united therewith. Openings 21 21 are left in this apron, preferably at the upper and lower lips of each cell, so as to allow water to iiow into and out of the cells and to stand level therein. The apron is preferably composed of concrete reinforced by longitudinal and transverse steel bars 22 23 of the type already described.

At one end of the dam outside of an abut- IOO ment 24 I have shown a well 25,1iavinga pipe 2.6 connecting it with the pond back of the rear wall 11 and provided with valve 27, a drainage-pipe 28, provided with valve 29, and pipes 30 30, connecting said well with the lower portions of the rows of cells 13 and provided with valves 31. Openings 36 are left in the buttresses 14 to 'provide communication between lthe cells in each lateral row or series,

so that between any pair of the transverse walls the several cells in a row form virtually one large cell or compartment as respects their water-retaining function.

The base 10 of the dam is preferably arched underneath each cell, as shown, the buttresses 14 being extended down between the arches to form piers or sills 32, on which the dam is supported. This arch transmits the weight of the water in the cells to the buttresses and to the structure as a whole instead of directlyT onto the bed-rock, which would be the case if there were no space underneath the floor. The vertical bars in the buttresses transmit this weight through the entire mass of the buttress without permitting a theoretical tensile strain on the concrete in case the dam were about to overturn. The spaces underneath the arches, furthermore, serve as an efficient drain to prevent any accumulation of static pressure from accidental leaks, but instead carry olf s'uch leakage rapidly and freely into the tail-race. I do not, however, limit myself to the arched bottoms of the cells, as under some conditions it may be preferable to lay a flat concrete base directly on the bed-rock, but integrally joined to the buttresses, as shown at 37.

The stability of my improved dam is due principally to three factors. The first factor' of stability is the weight of the structure itself and of the water in cells 13. These cells are kept full to overiiowing so long as there is any water flowing over the lip or crest of the rear wall 11. In times of drought, when no water is passing over the dam, any slight losses from evaporation or leakage may be made good by a supply from the pond by the well Q5 and gates 9.7 31. The hydrostatic pressure of the water upon the transverse walls 15 is only that due to the difference in head between two adjacent cells, which in general would not exceed five feet. The thickness of reinforced concrete necessary to stand this slight pressure is quite small, so that I prefer to make the walls thick enough to stand an unbalanced pressure, which practice will admit of any series of cells being emptied for inspection without emptying the adjacent cells. In filling' the dam, however, the preferred method is to avoid the heavy unbalanced pressures which would arise in filling any one or more series of cells singly, but instead to lill all of the cells simultaneously from the well 25 by way of pipes 30, each cell being cut off fro1n`the well by its corresponding gate 31 as soon as it overflows. In emptying the dam the cells are preferably drained simultaneously. The hydrostatic pressure on the buttresses 14 is always balanced, and the thickness of the buttresses is therefore determined with reference to transmitting the total pressure from the head of water in the pond to the foundationrock. It will be observed that the base 10 is an important feature in the monolithic structure of the dam, inasmuch as it ties the vertical walls and buttresses together along their lower edges, and thus causes the dam to act as a unit in transmitting pressures and resisting overturning, as well as being effectual in preventing leakage from the dam through the bed-rock. If desired, any one or more rows of cells 13, preferablyv the upstream row or rows first, may be filled, as indicated at 34, with loose gravel, cobbles, loose quarrystone, or any other cheap material at hand and the voids then filled with water. The total weight of material in the cell under these conditions will be about double that of water alone and the stability of the dam correspondingly increased. This procedure is applicable when it is desired to shorten the base of the dam and increase the pitch of the apron. The second factor of stability is the apron 20. This is an important feature, inasmuch as it ties the structure together along the top and braces the rear wall 11 and all of the transverse cell-walls, transmitting the pressures substantially in a right line to the toe of the dam. For this purpose the toe 12 should be substantially in line with the slope of the apron, as shown. The transverse walls 11 and 15 tend to overturn from the pressure of the water in the pond or cells about their lower edges as fulcrums or hinges; but the apron 2O opposes this tendency with a resisting force applied with the greatest possible mechanical advantage at the upper ends of the walls. The buttresses 1e also materially' oppose the tendency of the structure as a whole or its transverse-walls to overturn. It will be evident in view of the above that the dam as a whole is subject to strains of compression. The apron 2O has an additional function in protecting the upper edges of the cells from damage by ice, logs, and other iioating matter and excessive ioods and in reducing the velocity and impact of the water on the bed-rock at the foot of the dam. So far as this function is concerned the apron might be composed of logs, timbers, railroad-iron, 85o., with spaces between for the admission of water to the cells. The effect of a flood is to increase the weight of the dam by the weight of water superimposed on the apron 20, and the dam may be so proportioned that this weight will more than balance the additional horizontal pressure due to the increased head. The dam therefore becomes increasingly stable as the flood height increases and to that extent op- IOO IOS

IIO

crates as a so-called gravity-dam, although with the difference of having its inclined face on the downstream side instead of the upstream side. The third factor of stability is the anchorage by means of bars 18 or equivalent at the heel of the dam. The pressure of the water in the pond back of the dam acts horizontally at the center of pressure of the dam, and so through a lever equal to its ver tical height above a fulcrum at the toe 12. The resistance offered to this overturning moment by the bars 18 and footing-wall 19 is applied on a much longer lever-arm, equal to the whole length of the base from the heel of the darn to the toe 12. These three factors of stability are more clearly seen by reference to the diagrammatic view, Fig. 6. Assume that at first only that portion of the dam shown in heavy shading were huilt and without anchorage. Manifestly the dam would not be stable, and the pressure of a sufficientlyhigh flood applied at 88 would overturn it about the point 39. Now add the light-shaded apron and the numerous supporting-buttresses 14, and the overturning eort is resisted in the most efficient manner. Finally add the anchor-wall 19 and integrally join it to the dam by the tension-bars 18, and the total stability of the structure can be raised to any desired factor. Indeed, this modification of actual construction made by omitting one or more of the transverse walls forming one or more of the lower series of cells may be found economical under certain conditions and will not avoid the essential principles of my invention.

1t will be seen that in the construction shown in Fig. 6 the downstream-wall of the water-confining structure or pound is supported by the buttresses 14 and that these buttresses also support the lower portion of the apron, which is extended beyond the said downstream-wall. It will also be seen that my invention is embodied in a water-im pounding structure formed as a dam and composed of a floor and retaining-walls so formed that the liquid contents of the structure constitute the major portion of the bull; and weight of the dam, the structure therefore being completed and becoming an operative dam when charged with water.

1. A dam comprising a unitary artificial structure of floor and upright walls forming a series of water-retaining cells downstream from the crest, plural in number longitudinally of the stream-flow, and open to communication with the pond, said longitudinal cells having overflows respectively at different levels.

2. A dam comprising a unitary artificial structure of floor and upright walls forming longitudinally, downstream from the crest, a plurality of cells open at their upper ends respectively at different levels, the crest of the dam forming a spillway over which water on the .downstream side, a foundation therefor, and an anchorage for the upstream heel of the dam comprising' a footing locked to the foundation, and tension members embedded in the heel of the dam and said footing.

5. A dam formed with a plurality of cells, and means for simultaneously filling said cells.

6. A dam formed with a plurality of cells, and means for simultaneously draining said cells.

7. A dam formed with a plurality of cells, and conduit connections from the pond to the several individual cells whereby any cell may be separately filled from the pond, said connections having valves.

8. A cellular dam, a well at the flank of said dam, individual pipes connecting' said well with the several cells and provided with valves, a pipe connecting said well with the pond and provided with a valve, and a drainpipe leading from said well and provided with a valve.

9. A cellular dam having a cell-covering sloping apron stepped at its downstream end in the dam foundation and apertured to admit water to the cellular interior of the dam.

10. A cellular dam having a cell-covering sloping apron stepped at its downstream end in the dam foundation and open in structure to admit water to the interior of the dam, and upright buttresses supporting said apron.

11. A multicellular dam having a sloping covering for the cells apertured to admit water to the latter and extending on the downstream side from the crest of the dam to an anchorage-point substantially in line with the slope of said apron.

12. A dam provided with intersecting longitudinal and lateral upright walls forming cells plural in number, and a sloping pervious apron covering said cells and integral with said walls.

13. A dam composed of a plurality of waterretaining cells on its downstream side open at their upper ends, one or more of said cells containing a body of loose comminuted material whose voids are adapted to be filled by the water in the cell.

14. A dam comprising a plurality of waterballasted cells, and means for supplying them successively in a descending series with the excess water traversing the dam.

15. A dam, the major portion of whose bulk is composed of cells or receptacles adapted to impound water.

16. A dam formed with a plurality of cells, and connections between said cells and av source of water-supply to permit inflow of water simultaneously to adjacent cells.

17. A dam formed with a plurality of cells having outlets arranged to permit outflow of water simultaneously from adjacent cells.

18. A dam comprising a water-impounding structure of floor and retaining-walls, the crest of the dam forming a spillway over which water flows to supply said structure.

19. A dam comprising a water-confining structure or pound, of floor and retainingwalls, and having a pound-covering sloping apron apertured to permit the entrance of water between said walls.

20. A dam comprising a water-impounding structure or pound. of floor and retainingwalls, having a pound-covering sloping apron apertured to permit the entrance of water between said walls, the said apron extending beyond the downstream-wall of the structure, and buttresses supporting the said downstream-wall and the portion of the apron eX- tending beyond the same.

21.' A dam comprising a water-impounding structure of floor and retaining-walls, and having a crest forming a spillway over which water ows to supply said structure, and additional means for conducting water from the pond to the interior of said structure to compensate for loss of water therefrom.

22. A dam comprising a water-impounding structure of loor and retaining-walls, and adapted to be completed or converted into an operative dam by a charge of water, said charge constituting the major portion of the bulk and weight of the completed dam.

23. The herein-described method of preventing unbalanced pressure in filling a multicellular dam which consists in causing the water to rise at a substantially uniform level in adjacent cells.

24. The herein-described method of preventing unbalanced pressure in draining a multicellular dam which consists in causing the water to subside simultaneously in adjacent cells.

25. The herein-described method of lling a dam having a series of cells with overflowoutlets at different heights, and preventing unbalanced pressures on the walls or' said cells, which consists in causing the water to rise at a uniform level in adjacent cells and successively up to the overflow-outlets of the several cells.

In testimony whereof I have affixed my signature in presence of two witnesses.

NILLIAM L. CHURCH.

Witnesses:

R. M. PIERsoN, A. C. RATIGAN.

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