US1885470A - Dam and the method of constructing the same - Google Patents

Description

NOV. 1, 1932. NOETZLI v 1,885,470

DAM AND THE METHOD OF CONSTRUCTING THE SAME Filed Jan. 15, 1952 AWZW /4 Patented Nov. 1 1932 PATENT OFFICE FRED A. NOETZLI, 0F LOS ANGELES COUNTY, UALEFOR NIA DAM AND THE METHOD OF COIt'S'IBUC TING THE SAME Application filed January 15, 1932. Serial No. 586,?17.

This invention relates to dams of the earth or rock-fill type, and the primary object of the invention is toprovlde a dam or embankment of this type which will be safer and less subject to leakage or destruction than dams of a similar type as built heretofore.

Inthe ordinary type of dams or embankments of the earth and rock-fill type the watertightness of the fill is often increased by the provision of an upstream face slab of concrete. Past experience with structures of this kind has shown that even when built of the best materials and under the best conditions of workmanship, they are likely to settle ap proximately one foot in each 100 ft. of height. This settling is due to the weight of the ma t'erial and of the water overlying the face slab. The settling of the fill tends to shorten the face slab a corresponding amount which is likely to produce such heavy strains as to crush or buckle the slab or damage it in other Ways.

These facts were recognized in United States Patent- No. 1,602,623, issued to me under date of October 12, 1926, and in my copending application, Serial No; 541,616 filed June 2, 1931.

The present application refers to some further improvements in dams or embankments of the earth and rock-fill type.

One object of the invention is to provide a dam or embankment designed to hold water and provided with an upwardly and rearwardly sloping seal wall of improved construction. there being certain joints in the seal wall which will tend to release stresses in it which otherwise would occur when the embankment settles.

Another object of the invention is to provide a seal wall comprising a plurality ofslabs of concrete one on top of the other whereby a laminated wall is formed being considerably more. flexible than a solid wall of the same thickness, andifurther providing in such alaminated wall slip joints and anchorage permitting the length of the wall in the direction of the slope to'be shortened materially when the supporting fill settles and without producing cracks inthe wall. 0 Another object of the invention is an nnnecessarily laminated, that is, formed of a proved method of construction whereby the concrete of some or all of'the layers of the seal wall is covered as soon as practicable with a waterproofing substance after the layer has been deposited, this substance tending to preas vent rapid drying out of the concrete and forming at the same time a waterproofing membrane between the two layers. This waterproofing substance is preferably of a kind that remains plastic for a considerable length of time, such as asphaltic or bituminous products, or the like, thus permitting the layers or laminae of the seal wall to slide over each other when the fill settles.

With the foregoing and other objects in view which will be made manifest in the fol lowing detailed description and specifically pointed out in the app-ended claims, reference is had to the accompanying drawing for an illustrative embodiment of the invention, wherein:

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

Figure '2 is a typical vertical section through the dam shown in Fig. 1 and may be considered as having been taken upon the line 2-2 of Fig. 1.

Figure 3 is a partial view in section through the dam shown in Fig. 1 and may be considered as taken upon the line 3 3 of Fig. 1.

Figure 4 is an enlarged view in section of a portion of the seal wall of the improved dam. w

Figure 5 is an enlarged isometric view of a portion of the seal wall in the vicinity of a joint;

Figures 6 and 7 are enlarged views in secion of a portion of the seal wall.

Referring to the accompanying drawing wherein similar reference characters designate similar parts throughout, the reference character 10 indicates the foundation on which is" erected the earth-fill, gravel-fill, or rock-fill dam or embankment indicated at 11. 12 indicates the downstream face of the dam and 13 indicates the upstream face. The seal wall embodyinga part of the invention is generally designated by the reference char actor 14. Thisseal wall is preferably but not plurality of layers of laminae or slabs of concrete, the lowermost layer being indicated at 15, an intermediate layer being indicated at 16, and an uppermost layer being indicated at 17. These layers are divided by joints into slabs or panels, the joints being of a construction which will permit the crowding together of the various panels. I may provide substantially horizontal joints 19, partly or en tirely filled with joint fill material, vertical joints 20 and laterally inclined joints 21, the latter being preferably roughly parallel to the slope of the hillside. Experience on some dams constructed in the past has shown that a seal wall with vertical and horizontal joints is likely to develop cracks roughly parallel to the slope of the hillside. The inclined joints 21 will tend to relieve the stresses in the panels in these inclined planes so that the panels are less likely to crack. When the fill of the embankment settles, the panels of the seal wall tend to be crowded downwardly and to glide along the inclined joints 21 thus tending to be crowded together also towards the middle of the dam as indicated by the arrows in Fig. 1. This downward and lateral movement of the panels tends to compress tightly the joint fill material in the horizontal and vertical joints, thus improving the watertightness of these joints.

The settling of the fill of an ordinary em bankment has the undesirable effect of tending to tear away the seal wall from the cut-off wall along the hillside. In my improved dam I provide a cut-off wall 22 to which is firmly connected by steel reinforcement a lower slab 30 of the improved seal wall. To this lower slab 30 is connected in a suitable manner an adjoining movable portion 24 of the seal wall so as to provide a tight seal between the slab 30 and the seal wall, for in stance, by a slip-joint 25, as illustrated in Fig. 3. The length L of the slip-joint 25 and the amount of steel reinforcement R- in the slab 30 and in the adjoining portion 2 1 of the seal wall are preferably related to each other and to the pressure P upon the seal wall in such a way that the steel reinforcement R is strong enough to overcome the friction in the joint 25 due to the pressure P resulting from the pressure of the water in the reservoir or from the weight of the fill material F, or both. In asimilar manner I prefer to space the vertical joints 20 and 20a in an upper layer 17 and in a lower layer 16 of the laminated seal wall 14 at such a distance D from each other that the steel reinforcing R in the two layers is strong enough to overcome the friction over the distance D. In case the regular rein forcement of the slabs is not sufficient for this purpose I place additional steel reinforcing bars R-l in the slab bridging the joint 2061 for instance, as shown in Fig. 5.

In the horizontal joints 19 there will ordinarily be no tension stresses developed.

On the contrary, due to the crowding downwardly of the panels when the fill settles there will be compression forces exerted in the layers in the direction of the slope of the seal wall, tending to diminish the width of the joints 19. In a laminated seal wall these compression forces in the several layers are opposed by the friction bet-ween the layers. If the joints 19 in the different layers are staggered too widely, the friction between the layers may be too great so that the compression forces in the layers are unable to overcome this friction. Thus the width of the horizontal joints 19 might not be decreased materially and their usefulness would be much impaired. I prefer to stagger a horizontal joint 19 (see Fig. 7) in the lowermost layer 15 relative to the horizontal joint l9-a in the intermediate layer 16, and the horizontal joint 19-?) in the uppermost layer relative to the joint 19-a in such a way that a reasonably safe compression stress in the layers will overcome the friction force between the layers in the distance E between the joints 19 and 19-0., and between 1964 and 19-5. The following example is presented by way of an illustration. Assume a laminated seal wall comprising two layers 16 and 15 exposed to the water pressure at a depth of 200 ft. below the water level. The water presses the two layers or slabs together with a force of 200 X 62.5=12,50O pounds per square foot. Assuming a coefficient of friction of 0.5 between the slabs, the friction force for each square foot of contact between the slabs is 0.5 12,500=6,250 pounds. Assume now the slabs to be each 4 inches thick. A safe compression stress in the slabs to prevent crushing or buckling may be assumed at 500 pounds per square inch corresponding to a safe force of 4X 12 500=24:,000 pounds per foot of Width. This force of 2 1,000 pounds exerted downwardly along the slope of the slab would therefore be able to overcome the friction between the slabs in a length of Consequently, if the distance E between the joints 19 and 19 0; is greater than 3.9 ft. no sliding between the layers 16 andv 15 will occur. In this example the joints 19 and 19-a in the two layers 16 and 15, respectively, would therefore have to be staggered less than 3.9 feet in order to insure the joints 19 and 19-61 to be closed by the assumed safe compression stress in the layers of 500 pounds per square inch. In the upper portions of the dam where the water pressure is less, the joints may be staggered by a greater distance.

It is evident, therefore, that for a given thickness of the layers and for an assumed safe compression stress in the layers, further 9 feet.

for an assumedsafe value of the friction coefficient, a'definite relation must exist between the maximum permissible amount of staggering of the joints 19 and 19-a. and the pressure of the overlying water or other material. It is to be understood that safe compression stresses of the concrete of the layers and safe friction coefficients may vary with the kinds of material employed. 7

At the joints 19, 20 and 21 I prefer not to extend any reinforcing steel across the joints. A laminated seal wall is therefore relatively weakest where there is arjoint in one of the layers 15, 16or 17. I prefer to strengthen the seal wall by placing relatively short additional steel bars 26 across the plane of the joints in the layer above or below the one with the joint such as illustrated by Fig. l. While ordinarily I prefer to fill-the joints between the panels completely with a plastic joint-fill material, I may in some cases,

fill the joint space only partly, such as illusstrated at joint 19 in Fig. l. When the panels are crowded together the joint-fill mate'- rial 2? will be squeezed together and fill the reduced joint space completely. I may accomplish a similar result by using a joint filler formed by a bent sheet 28 of suitable material, such as asphalt or the like, and leaving temporarily a hollow space in the oint such as illustrated at 29 in Fig. 6.

In constructing the improved dam I prefer to place the fill material in the embankment first to a certain elevation, then prepare its upstream face in a suitable manner, for instance by placing specially graded material on the upstream face of the embankment, and then place the seal wall 1A against this up face. For depositing the concrete of the seal wall I prefer compressed air methods, for instance, a so-called cement gun, by means of which. the concrete is deposited upon the upstream face of the embankment without the use of forms on any slope that the fill material will stand. After placing a first layer 15of concrete upon the upstream side of the embankment, I place as soon as practicable a part or all of the thickness of a membrane M of waterproofing material upon the layer 15. This membrane has the double effect of protecting the concrete of the layer 15 from drying out too rapidly, and to provide a waterproofing seal between the layer 15 and the subsequent layer 16. After the layer 16 has been deposited I may place again immediately a waterproofing membrane 17 upon and so forth until the seal wall 14 is completed. Subsequently I may place additional fill material F on the upstream side of part or all of the seal wall 14. V

In constructing the joints of the seal wall I may provide relatively wide joint spaces between adjoining panels and fill these joint spaces partly with a suitable joint-fill mate rial. lVhen the fill settles and thepanelsare crowded together, the joint-fill material'27 two outer slabs 15 and '17 and one or more intermediate slabs 16 I prefer to place a larger percentage of steel reinforcementinto the intermediate slab 16' because in this slab the reinforcement is evidently best protected against corrosion. V

In constructing the dam I may build the embankment of ordinary fill material, then place argravel fill on an increasingly flatten ing slope against the upstream side of the fill material, for instance, as illustrated in Fig. 46 of Transactions, American Society of Civil Engineers, Volume 87 (1924)"page 104, and subsequently place my improved seal wall upon said gravel fill. 1

Various changes may be made in the details of construction without departing from the spirit or scope ofthe invention as defined by the appended claims.

I claim:

l. A dam of the filled type comprising a seal wall, certain portions of said seal wall being divided into panels by intersecting joints, said seal wall being connected to a cut off wall extending into the foundation upwardly along the side hills, some of said joints extending roughly parallel to the slope of the side hills and at a distance of roughly- 10 to ft. from said cut-off wall.

2. Ina filled dam a seal wall comprising panelsseparated by relatively wide intersecting joints, the alignment and width, measured downwardly along the slope, of said joints facilitating the crowding of the panels downwardly during the settling of the fill material.

3. An embankment comprising a seal wall connected to a cut-ofi' wall'extending into the foundation and along theembankment, said seal wall comprising a plurality of layers of reinforced concrete, at least one of said layers being connected to said cut-off wall, at least one other of said layers being. disconnected from said cut-ofi' wall and being capable of a dislocation relative to it.

4:. In a filled dam a sea-l wall connected with a cut-0d wall extending into the foundation material, said seal wall comprising a plurality of layers ofconcrete superimposed one upon the other, slip-joints interposed between said layers, one first layer. being connected to the cut-off wall by means of anchor bars,-at least one other layer-being ca pable of sliding in one of said slip-j oints relative to the first layer. 7

5. In a filled dama seal wall as described in claim 4, there being reinforcing steel bars in each layer of sufficient cross section and strength'to overcome-the friction force in said slip-jointin" case of a sliding movement between said layers.

' 6.;In a filleddam, an upwardly and rear wardly sloping seal wall comprising a pluels of the upper layer extending across the joint in the lower layer but terminating near the joint in the lower layer, whereby the panels of the upper layer, where they cross thejoint of the lower layer, will 'be'strengthened to compensate for the reduced section of the'seal wall where the joint in'the lower layer occurs.

7. A filled darnvcomprising'a seal wall formed of at least one upper and one=lower layer of reinforced concrete, said layers being divided by joints into panels, certain panels in the upper layer overlapping certain panels in the lower layer by a certain distance, said distance bearing a definite relation to the pressure between said layers, when the reservoir is full, and to the amount of reinforcing steel embedded in the overlapping panels in said upper layer, such as to permit sliding between the panels in the lower layer and the overlapping panels in the upper layer.

8. In a filled dam a seal wall comprising two layers of concrete, each layer being di vided into sections by substantially horizontal joints, said layers being capable of sliding one over the other, certain of said joints in the upper layer being staggered relative to the correspondlng joints 1n the lower layer, the amount of staggering bearing a definite relation to'the thickness of'the layers and to the force gether. v

9. In a filled dam a seal wall comprising a plurality of layers of concrete capable of sliding relatively to each other and being divided into sections by spaced horizontally extending joints,certain of said joints in the several layers being staggered, the amountiof staggering bearing a definite relation to the thickness of the layers and to the force pressing the layers together, and being not more than an amount enabling said sections't'o be crowdedtogether when the fill settles;

10. Themethod of constructing a laminated seal wall inconnection with an embankment,-which includes the placing of a first layer ofconcrete on the upstream side pressing the two layers toof the embankment and depositing as soon as practicable a waterproofing substance upon said layer to protect the-concrete from rapidly drying out, and subsequently placing another layer of concrete upon the first layer, said waterproofing substance facilitating a sliding movement between the laminae of the seal wall in case of settling of the embankment.

11. The method'of constructing a seal wall in a fill dam which includes the placing of a plurality of alternate layers of reinforced concrete and relatively plastic material, said material being deposited as soon as practicablc upon the surface of the preceding layer of concrete so as to prevent a rapid drying out of the concrete, and also facilitating a relative movement between said layers taking place in case of settling of the fill.

12. The method of constructing a seal wall in afill dam which include providing in said seal wall substantially horizontally extending and relatively wide joints, partly filling said joints during construction with a relatively plastic joint-filled material, thus permitting a considerable decrease of the width of the joint during the settling of the dam without the joint-filled material being squeezed out of the joint.

An embankment provided with a seal wall comprising a plurality of superposed layers, capable of iding one over the other, said layers being divided into panels by joints, ertain 'oints in an upper layer crossing cerain other joints in a lower layer at angles of less than ninety degrees.

14. The method of constructing an embankment provided with an upwardly and rearwardly extending seal 'Wall, said seal wall comprising a. plurality of layers capable of sliding one over the other, by constructing at least one of said layers of sections separated from each other by open joint spaces, then placing space coveringsover said joint spaces, and subsequently placing another layer on top of the previously constructed'layer, and on top of space coverings.

1 5. The method of constructing a filled dam provided with an upwardly and rearwardly' sloping seal wall, by building said seal wall of sections separated by joint spaces, the aggregate width of said joint spaces, measured downwardlyin the direction of the slope of the seal wall 'corresponding approximately to the linear amount of the settlement of the dam.

16. The method of constructing a dam comprising an embankment and a seal wall, by placing fill material in said embankment, subsequently placing a layer of rock fragments approximately of the size of gravel upon the upstream side of the embankment, and subsequently placing a laminated seal wall upon saidlayer of rock fragments, at least some portions of said seal wall being divided into sections by substantially horizontally extendin g and relatively wide joints permitting said sections to be crowded together approximate ly in proportion to the linear amount of the settling of the embankment.

17. The method of constructing a fill dam comprising an upwardly and rearWardly ex- FRED A. NOETZLI.

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