US2133256A - Method of building a dam - Google Patents

Description

Oct 11, 1938. S. W. STEWART ET A1. I 2,133,256

t METHGD OF BUILDING A DAM Filed Feb. 28, 1936 3 sheets-sheet 1 Ymh ' Y E12-f f- /KW ATTORNEY Ot- '11,' 1938. s. W. STEWART ET L 2,133,256

METHOD OF BUILDING A'DAM Filed Feb. ze, 193e s sheets-sheet 2 l A ATTORNE I Oct.l 11, 1938. s. w. STEWART r-:T A1. l l 2,133,256

' METHOD 0F BUILDING A DAM Filed Feb.' 28,'1936 3 Sheets-Sheet 5 ,fv/, @if y Patented Oct. 11, 1938 UNITED STATES PATENT OFFICE METHOD F BUILDING A DAM Application February 28, 1936, Serial No. 66,172

Claims.

This invention relates to a novel and improved dam and method of building the same, and the novel features will be best understood from the following description and the annexed drawings, in which we have shown selected embodiments of the invention, and in which:

Fig. 1 is a vertical section through a dam showing one form which the invention may take;

Fig. 2 is a section on the line 2 2 of Fig. 1;

Fig. 3 is a vertical section on a plane parallel to that of Fig. 1 and showing an intermediate step in the building of the dam;

Fig. 4 is another view on a plane parallel to that of Fig. 3, but on a greatly enlarged scale and showing other features ofthe invention;

Fig. 5 is a View similar to Fig. 1, but showing a dierent embodiment which the invention may take;

Fig. 6 is a view similar to Fig. 1, but showing the invention as applied to a different type oi dam;

Fig. '7 is a fragmentary View on the same plane as Fig. 1, but showing different types of joints in a buttress;

' Figs. 8 to 12, inclusive, are fragmentary sections on the lines A-A of' Fig. '7, and showing different detailed constructions of the joints;

Fig. 13 is a fragmentary view on the same plane as Fig. 5, but showing details of a diiferent construction of joint.

The invention finds use in a variety of forms of masonry dams. For example, it may be used either in the gravity type, the so-called Ambursen type, or the so-called multiple arch type, as well as in other types.

Referring iirst to Figs. 1, 2, 3, and 4, we have shown the invention as applied to a dam of the so-called Ambursen type, which has an upstream water bearing'deck l inclined to the horizontal and supported by buttresses 2 disposed beneath the deck and extending down-stream therefrom, although, as noted above, the invention may be used with other types of dams. In building a dam of any substantial height, trouble has been experienced from cracking caused by temperature stresses, particularly in localities where Wide variations in temperatureV take place. Y

'Ihe temperature of concrete masonry is greatly increased during the process of mixing by chemical changes that take place in the hydration of the cement, particularly when ne cement is used as is the present practice. This high temperature is often augmented by the presence of free water in the concrete, and these factors combined with wide changes in temperature caused by the climatic conditions arerof substantial extentand have in practice often caused serious damage in the way of cracks which form after Vconstruction has been completed.

According to one feature of our invention, we plan to avoid the formation of cracks by building the dam in sections extending lengthwise of the dam or, in other words, placed so that one section is up-stream from another. are separated by joints so situated asV not to impair the strength of the dam and so constructed as to permit free movement along the joints be'- tween the adjacent sections. In the embodiments being described, we have shown such an arrangement of sections in buttresses used to support the water-bearing deck of an Ambursen dam, although they may be used equally well to support the arches of a multiple arch dam.

For example, in Fig. 1 is shown a joint 3 separating adjacent sections 4 and 5, this joint being formed by contacting surfaces on the adjacent sections. This joint 3 is preferably located along a surface of minimum shear or at least of a small shear so that there will be practically no tendency under normal conditions of full load for one section to move along the joint relatively to the other, in a direction lengthwise of the joint. If for various reasons it is found undesirable to construct the jointsy continuously, they may be staggered as shown by 22', Fig. 5. Movement transversely of the joint may be prevented by suitable keys formed of projections on one section received in grooves in another, such as will be described presently in connection with another feature of the invention.

'Ihe surfaces forming the joint are provided with steps, these steps being disposed at angles to the surfaces or to the joint and preferably alternating as shown in Fig. l, with alternate steps substantially normal. For example, the steps 6 and 1 are vertical, whereas the intermediate step 8 is horizontal. Normally, the joint 3 will be inclined to both the horizontal and vertical, andrtherefore by making the steps alternately horizontal and vertical as indicated,rthe desired conditions are obtained. These vconditions are that when a tendency does occur for one section to move with respect to the other along the joint, as will occur under partial load, there is no abrupt step or shoulder or feather edges between adjacent sections. The steps will resist movement,

These sections l but at the same time will kpermit normal conperature contraction to take place While at the same time the different parts of the dam are adequately tied together.

According to another feature of our invention, we so build the part of the dam subjected to greatest temperature change that the temperature stresses will be taken in compression rather than in tension, and also provide other means for preventing damage as will be seen presently.

In Figs. l, 3, and 4, the lines 9, I0, and II indicate the usual horizontally disposed construction joints, and preferably the steps 6, l, and 8 are placed at said joints, although this is not essential. It will be seen that the buttress 2 shown in Fig. l has a section I2 spaced from the section 5 in an 11p-stream and down-stream direction, and preferably these sections are poured at the same time, leaving the relatively narrow space therebetween vacant, and then this space between the sections is filled at a later time for a reason which will presently appear.

The method will be better understood from an inspection of Fig. 3, wherein the sections 5 and I2 are shown as complete up to the construction joint I, whereas the intervening space I3 has not been filled above the construction joint 9, but has been partially filled beneath it. In practice, the sections 5 and I2 are poured at the same time up to, say, a construction joint 8, and this may be done during the heat of the day when the temperatures are high. The concrete itself develops additional temperatures to add to the temperature due to the climate, and therefore a certain amount of expansion will take place, which expansion can be absorbed in the space I3. Then, after the sections 5 and I2 have had opportunity to cool, and preferably at a cooler period of the day, the space I3 may be filled.

It will be noted that the sections 5 and I2 are relatively massive compared to the space I3 intermediate thereof, and therefore the space can be quickly lled. The result will be that, as the temperature of the entire structure increases due to the climate, both the sections 5 and I2 and the new section I4 in the space I3 will be in compression, because substantially all of the shrinkage has already taken place, and, in any case, the amount of shrinkage which might take place in the small section I4 would be less than the expansion of the relatively large sections 5 and I2 on opposite sides thereof. Y

The process, of course, is repeated between successive construction joints until the entire buttress or other portion of the dam is completed.

The joints between the sections 5 and I2 and the intermediate section I4 are preferably formed in the same manner as previously described for the joint 3. That is to say, they are provided with steps I5 and I5 which are horizontal and vertical, respectively, and which operate in the same manner as described for the joint 3. In this connection, it may also be said that the section I4 is preferably built along or parallel to a line or surface of minimum shear or, in other words, along or parallel to a line of principal stress. The contacting surfaces between each section 5 and I2 and the intermediate section I4 are preferably formed with keys II (Fig. 2) preventing lateral displacement between the sections while permitting limited movement longitudinally of the joints to permit contraction of the masonry between adjacent steps. Preferably, also, a similar key arrangement is used at the joint 3 to prevent lateral displacement between the portion of the buttress on opposite sides of the joint.

The section I4 may be connected with adjacent sections by reinforcing steel placed where desired and which has been indicated at I8 in the various figures. This steel may be embedded in the sections 5 and I2 when poured and with its ends projecting outwardly into the space I3. These ends, of course, become embedded in the masonry of the section I4 when it in turn is poured.

While the cooling of the sections 5 and I2 or other similarly arranged sections may be caused by merely allowing such cooling to take place from natural causes, nevertheless this natural action may be expedited. For example, as a help in preventing temperature stresses, We may, if desired, embed in the sections 5 and I2 pipes I3 having their ends projecting into the space I3, and these ends may conveniently be placed in line with each other. While the concrete` of the sections` 5 Vand I2 is setting, brine or other cooling fluid may be forced through the pipes I9 to aid in quickly decreasing the temperature of these sections, and, if desired, may be sprayed over the concrete to cool it, by means of any suitable spraying system. Then before the section I4 is poured, the ends of the pipes may be con.- nected by a coupling 20, such that they form a rigid reinforcement between the sections 5 and l2. These cooling pipes may, after the concrete has attained its shrinkage, be used as a grouting system for the purpose of tightening the joints of the dam. If desired, the pipes I9 may be joined by a connection I9 extending around the joint, so that the piping need not extend into the space lIhe several sections of a dam, described herein, may be cooled with great efficiency either by an exterior spraying system or the use of other adequate methods. For example, a cooling spray may be applied, from a suitable piping system or other means, to the masonry sections 5 and I2, Fig. 3, which are disposed in an up-stream and down-stream direction with respect to 'each other and separated by a short space I3. After the sections 5 and I2 have been cooled in this manner, the space I3 is filled with concrete and either spray or cooling uid from a cooling system is applied. This process minimizes thevinitial temperature rise of the concrete in the space I3 as well as in the adjacent masonry section and causes thereby the stresses across the joints to be in compression under temperatures that would ordinarily cause the joints to be under tensional stresses.

In Fig. 5 is shown a modication of the invention in which, instead of having a continuous section I4 as previously described,v there is provided a joint 2i following an approximate surface of minimum shear, and in this case we pro-v vide plugs 22 of concrete which is poured after the concrete in adjacent sections 23 and 24 on opposite sides of the joint 2|. These plugs may conveniently be placed between alternate construction joints, for example one plug here being shown between the construction joints 9 and I0 and another between the construction joints II and`I2. The plugs may be connected with adjacent sections'by steel I8 as'before and be providedwith steps arranged vertically and horl- Zontally and which have been indicated at 25 and 26, respectively. Under some circumstances, it may be sufficient to place plugs as indicated at 22', without any connecting joint, but at staggered points in a buttress.

In Fig. 6 is shown a section of a dam 21 of the gravity type which may likewise be constructed in the manner described above. This darn is of any suitable cross-section which will resist over-v turning and sliding by means of its weight, and is provided with the usualhorizontally extending construction joints as indicated. In pouring the concrete or other masonry of which the dam is made, a method similar to that described above may be followed, which will result in a dam having a plurality of sections 2S, 29, and 30 spaced apart in an up-stream and downstream direction and separated by relatively narrow intermediate sections 3i and 32, these latter sections 3l and 32 being poured after the masonry in sections 28, 29, and 30 has had a chance to cool and contract. A further detailed description of this figure is not deemed necessary.

In Fig. 7 we have shown several partial joints 33 which may be constructed in any one of the ways illustrated in Figs. 8 to 12, inclusive. In each instance the concrete is left continuous eX- cept for a plane or surface of diminished Seotion, whereby when temperature or shrinkage stresses occur the concrete may crack at that plane or surface and thereby in efect form a joint there. This may be achieved in any one of numerous ways.

For example, strips of metal 34 may be used, either alone, as in Fig. 8, or with an intermediate piece of board 35, as in Fig. 9. In Fig. 10 a similar result is achieved by the use of two boards 36, while in Figs. 11 and 12 are shown two sheet metal pieces 31 having heads which may be nailed to the forms used in building the buttress. In Fig. 12 the arrangement is supplemented by a board 35, which may be used with any of the other embodiments where it is not shown.

In Fig. 13 is shown a detail of a joint in which the steel from two sections 5 and l2 extends into the section I3 and is there hooked over bars 38 over which in turn extend short hook bars 39, so as to form a exible joint which will permit the relatively slight motion between the sections which may result from temperature or shrinkage or other stresses, without disconnecting the steel.

While we have shown the invention as embodied in certain specic forms and as constructed in certain specic ways, these are to be taken as illustrative and not limiting, as we do not intend to limit ourselves except by the appended claims.

We claim:

l. The method of building a masonry dam which comprises building at a relatively high temperature sections of said dam extending lengthwise of the dam but spaced apart at a relatively small distance in an up-stream and down-stream direction, cooling the masonry of said sections, and then filling the spaces between said sections with masonry at a relatively low temperature.

2. The method of building a masonry dam which comprises building sections thereof extending lengthwise of the dam but spaced apart a relatively small distance in an up-stream and down-stream direction, with pipes in said sections, circulating a cooling fluid through said pipes, and lling said space with masonry.

3. The method of building a masonry dam which comprises building sections thereof extending lengthwise of the dam but spaced apart a relatively small distance in an up-stream and down-stream direction, with pipes in said sections having ends projecting into said space, circulating a cooling fluid through said pipes, and filling said space with masonry at a relatively low temperature.

4. The method of building a masonry dam which comprises building sections thereof extending lengthwise of the dam but spaced apart a relatively small distance in an up-stream and down-stream direction, with pipes in said sections having ends projecting into said space, ciroulating a cooling fluid through said pipes, coupling together the ends of said pipes extending from opposite directions, and lling said space with masonry surrounding and embedding said coupled pipes.

5. 'Ihe method of building a masonry dam which comprises building sections thereof eX- tending lengthwise of the dam but separated by spaces which are relatively narrow in an upstream and down-stream direction and which are disposed approximately along a line of minimum shear, shrinking said sections, and then lling the space between said sections with masonry.

SPENCER W. STEWART. CALVIN V. DAVIS.

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