US1860590A - Method of constructing dams - Google Patents

Description

y F. A. NOETZLI 1,860,590

METHOD OF CONSTRUCTING DAMS Filed Sept. 7, 1929 INVENTOR vide a method whereby dams of the gravity each two adjacent columns.

Patented May 31,1932

, FRED A. NOETZLI, orLos ANGELES, CALIFORNIA r METHOD'OF comm-norms DAMS L Application filed September This invention relates to improvements in dams and the method of constructing the same; I

In large concrete structures many stresses are set up n the structure for various reaalong the concrete-structure, cracks develop which are irregular and weaken the strucme; This'feature has been recognized in my co-pend1ng applications, Serial No.

220,197,-filed Septemberl'T, 1927, and Serial No. 319,205, filed November 14, 1928, over fwhi'ch the construction disclosed in this application maybe considered as an improvement by the reductionor elimination of dangerous stresses through improved cons'truction methodsand otherwise as described hereafter.

An object of the invention is to provide a dam and a. method of fconstruction for without weakening the dam. Another object of the invention is to provide a method of gravity type dam construction whereby the effect of shrinkage ofthe concrete is'rendered less harmful'by con structing certain portionsof the dam in the shape or forwardly inclined columns and leaving joints of weakened bond between Another-object'of the invention is to protype maybe built safely and economically first to an initial height, and subsequently raisedto a greater height, and "providing a joint between thefold and the later construction in'a' certain chosen direction, whereby the strength of the'struc'ture isnot impaired appreciably.

Other objects of the invention are to provide novel and advantageous joint construc- 7, 1929. Serial No. 390,870.

ence is had tothe accompanying drawings for an illustrative embodiment ofthe invention, wherein:

Figure 1 is a schematic elevation of the dam embodying the invention.

Figure 2 is a vertical section throughthe dam shown in Figure land maybe considered as having been taken upon the line 22 of Figure 1.

Figure 3 is a vertical section along the line 33 through the dam shown in Figure 1. y

Figure 4 is a vertical section along the line- 4 4 through the dam shown in Figure 1.

Figure 5 is a partial horizontal section. along the line 55 through the dam shown in Figure 1.

Referring to the accompanying drawings wherein similar'reference characters desig-' nate similar parts throughout, the dam shown in Figure 1 consists of a wall 1 of concrete designed to withstand water pressureby vir tue of its weight, usually calleda gravity type dam. The wall may be straight or curved in plan.

Figure 2 illustrates how such gravity type dam appears in section with the-rear side of the wall sloping upwardly and forwardly from the base upwards so-that the bottom of the wall is much thicker than the top. i

The wall 1 is divided by vertical. radial transverse joints 2 into a number of vertical units or slices 3, usuallyfromAO to: 60 ft. thick measured along the axis of the dam.

Past experience in concrete dam constructions has shown the necessity of providing suchtransverse contraction joints 2 in order to prevent vertical cracks in the dam due to the shrinkage of the concrete. This shrinkm age, of course, affects the concrete in a similar manner in an upstream and downstream direction. In fact, there is evidence in several existing gravltyvdams that lrregular cracks have occurred across the vertical slices 3 of V dams From a point where'thethick-F ness of the damnear the base exceeds ma terially the value of 50 ft, I provide one or more longitudinal joints 4 in the vertical slices 3, such as shown in Figures 3, 4, and 5.

These joints extend upwardly and forward- -T00 1 from the base of the dam to points near t e forward face of the dam. They are arranged at suitable intervals such as to provide means for the concrete to shrink without producing cracks.

The transverse joints 2 and the longitudinal joints 4 may be established in any suitable manner so that there will be weakend bonds arranged along predetermined planes thus tending to form portions or columns 5. The

longitudinal joints 4 extend substantially parallel to the direction of the first principal stresses when the dam is fully loaded; In these planes the shear is zero. For safety a ainst undue relative movements between adjacent columns ,5 there are provided key and groove connections in the joints at which will permit of small movements, for instance, d! to, Shrinkage of the concreate, but will prevent large movements which might endanger the safety of the dam. v

In order to accomplish some of the objects of my invention, I pour in the dam series of blocks of concrete in a vertical slice 3, designated in Figure 3by the reference characters 6, 7, and 8. Block 6 extends between two transverse joints 2 from the upstream face oftho dam, part way towards the downstream hoe. Block 7 extends from block 6 an additinnal distance downstream. Block 8 extends from block 7 to the downstream face. while I have shown in Figure 3 three blocks, 6 7, and 8, it should be understood that instead of three blocks, only two, or, in case ofverythick dams, 4 or more series of blocks may be. built in the manner described. The

important condition is that the rear face of block 6 and the. front face of block 7, also. the rear face of block 7 and the front face of block .8, are, substantially parallel to the direction of certain principal stresses in the dam when loaded to they crest.

It has been shown by theoretical deductions that in the. body of agravity dam under full load there exist two so-called principal 811N805," the direction of the first of which is assymptotic to the direction of the downltmm face of'the dam and normal to the upstreamlines. The second principal stresses not perpendicularly to the direction of the first principal stresses. In the directions of the. two principal stresses the shear is zero. An. inclined joint parallel to the direction of the first principal stress in a gravity dam does theroforefnot change to any material extent the atressdistribution in the dam as a hole. v I

In, constructing the improved dam, I may pour, for instance, block 6 first and give its domistmam face a slope substantially paral- 191" to. the direction of the first principal moment that locality in the dam. Then I establish an area of weakened bond, for in stance, by painting the downstream face with a suitable substance, like oil, asphalt, etc. so

as to decrease bondin of the concrete to the face. Then I pour lock 7 and treat its downstream face similarly as described for block 6. Then I pour block 8 against the downstream-face of block 7.

I may provide key and groove connections between the blocks 6 and 7 also between blocks 7 and 8, or I may staer the blocks as indicated in Figure 3 where y some kind of key and groove connections are producedbetween subsequent layers of concrete.

I may provide drain holes or other suitable means for disposing of water which mi ht tend to accumulate in the areas of contact tween the blocks 6 and 7, and 7 and 8, respectively. I v I In order to provide a proper transmiuion of stresses in the dam, I pour the blocks on slopes increasing upwardl in a downstream direction, as shown in igure 3. In this manner the daily-construction joints, which are planes of weakness, are more nearly pol.- pen lcular to the direction of the first incipal stresses in the dam under full 10 In constructing the improved dam, I may poura series of blocks 6 one on to of the other ahead of the blocks 7 and 8, an in such a manner that the downstream faces of the blocks Glare. substantially parallelto the. direction of the first principal stresses in the dam. Subsequently, I pour a series of blocks 7 against the downstream face of the blocks 6, and again make the downstream faces of the blocks, 7 extend substantially parallel to the direction of the first principal stresses at those points.

I may also choose to pour a series of blocks 8 first, then a series of locks 6, and wedge, a series of blocks 7 between the blocks 6 and 8. S ch a ser sof b o ks 8 or b k 7 tively, may be considered as forming upward- .ly and forwardly inclined columns 5, the upstream and downstream faces of' whi are substantially parallel to the direction 0 the principal stresses in the monolithic dam under full load.

When it is desired to build the improved gravity dam first to. an initial height and ralse it subse uently to its ultimate height, I build first tie upstream portion 9 of the dam as shown in Fig. 4, with a slopeof the downstream face of this ortionthat is substantially parallel to the irection of thefimt principal stressesv in the ultimate dam.

When the dam is to beraised I build an inclined column 5, similarly as, shown in 4, against the upstream ortion f thedam. I may provide key and groove connections between the upstream portion-9 and the downstream column 5, or extend reinforcing bars 10 across thearea of contact between upstream portion 9 and. downstream-column 5,

as indicated, in Fig. 4. p

In order to. prevent water underpressum entering the joints 4, that is the areasof con- .vide shafts 13 extending substantially along the joints 4. Through these shafts 13 the drainage'channels 11 may be inspected from time to time, and cleaned, if necessary.

I claim:

1. The method of constructing a concrete dam by first building a certain up-stream portion of the dam to an elevation lower than the final height of the dam, then building a down-stream portion against the downstream face of said -up-stream portion, the area of contact between said up-stream and said down-stream portion being substantially parallel to the direction of certain first principal stresses when the dam is fully loaded, and further constructing drainage channels along at least some of said key anc groove connections;

2. The method of constructing a concrete dam as described by claim No. 1, and further providing reinforcing bars extending across the area of contact between the upstream and the downstream portion of the dam.

3. The method of constructing a concrete dam as described by claim No. 1 and further providing means for facilitating the inspection and cleaning of said drainage channels.

4. The method of constructing a concrete dam, said method consisting of pouring certain portions of the dam as a first series of blocks of concrete, said blocks being arranged one on top of the other and extending part way between the upstream and downstream faces of the dam, one upper block being staggered relative to the next block below, there being constructed an adjoining second series of blocks by pouring concrete against one of the faces of the aforesaid first series of blocks, there being areas of weakened bond between the two adjoining series of blocks, said areas extending longitudinally substantially along lines of zero shear in the dam when fully loaded.

5. The method of constructing a concrete dam, said method comprising the pouring of a plurality of blocks of concrete one on top of the other, said blocks extending part way between upstream and downstream face of the dam, the front and rear faces of said blocks extending substantially parallel to certain first principal stresses in the fully loaded dam, the tops and bottoms of at least some of said blocksslopingupwardly in a downstream direction.

6. The method of constructing a concrete dam designed to resist water pressure by virtue of its weight, said method consisting of pouring transversely spaced columns each extending upwardly and part way between the upstream and the downstream face of the dam, the top of at least some of said columns sloping upwardly in a downstream direction allowing the columns to set and shrink, then providing the upstream face of certain of said columns and the downstream face of certain other of said columns with a substance tending to prevent bonding of the concrete, and then pouring the intervening columns, at least certain portions of said faces extending substantially parallel to the direction of zero shear stresses in the fully loaded dam.

7. The method: of constructing a concrete dam designed to resist water pressure by virtue of its weight, said method comprising the pouring of a first series of blocks of concrete one on top of the other and extending part way between the upstream and the downstream face of the dam, the tops and bottoms of at least some of said blocks sloping upwardly in a downstream direction, permitting said first series of blocks to set and shrink, and subsequently pouring a second series of transversely disposed blocks against said first series and establishing an area of weakened bond between said two series of blocks, at least certain portions of said area extending substantially parallel to lines of zero shear stresses in the fully loaded dam.

8. The method of constructing a concrete dam comprising aunit defined by transverse contraction joints, said unit being divided by at least one longitudinal contraction joint into portions,-said method consisting of alternately raising said portions by the pouring of layers of concrete, establishing a longitudinal contractionjoint between two adjoining portions and providing means in said joint for improving monolithic action of said unit, the top of at least some of said layers sloping upwardly in a down-stream direction;

9. The methodof constructing a concrete dam comprising units defined by transverse contraction joints, said units being divided bylongitudinal contraction joints into portions, said method consisting of pouring blocks of concrete in transversely spaced portions, permitting said blocks to set and shrink, then pouring blocks of concrete in the intervening portion after the initial shrinkage of the first portions has taken place, the top of at least some of said blocks sloping upwardly in a down-stream direction.

FRED A. NOETZLI.

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