US3422629A

US3422629A - Construction support system and methods and apparatus for construction thereof

Info

Publication number: US3422629A
Application number: US665916A
Authority: US
Inventors: James P Watts
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-09-06
Filing date: 1967-09-06
Publication date: 1969-01-21
Anticipated expiration: 1986-01-21

Description

Jan. 21, 1969 J. P. WATTS 3,422,629

CONSTRUCTION SUPPORT SYSTEM AND METHODS AND APPARATUS FOR CONSTRUCTION THEREOF Filed Sept. 6, 1967 Sheet of 4 INVENTOR. JAMES I? WATTS ATTORNEYS Jan. 21, 1969 J Q TT 3,422,629

CONSTRUCTION SUPPORT S YSTEM AND METHODS AND APPARATUS FOR CONSTRUCTION THEREOF Filed Sept. 6, 1967 Sheet 2 of 4 INVENTOR.

/ 4 JAMES P. WATTS BY ATTORNEYS Jan. 21, 1969 J P WATTS 3,422,629

CONSTRUCTION SUPPORT SYSTEM AND METHODS AND APPARATUS FOR CONSTRUCTION THEREOF Sheet 3 of 4 Filed Sept. 6, 1967 INVENTOR. JAMES R WATTS ATTORNEYS Jan. 21, 1969 J. P. WATTS 3,422,629

CONSTRUCTION SUPPORT SYSTEM AND METHODS AND APPARATUS FOR CONSTRUCTION THEREOF Filed Sept. 6, 1967 I Sheet 4 of 4 j INVENTOR. 7- JAMES R WATTS AT TORN EYS United States Patent 3,422,629 CONSTRUCTION SUPPORT SYSTEM AND METHODS AND APPARATUS FOR CON- STRUCTIQN THEREOF James P. Watts, 6930 E. Pinchot, Scottsdale, Ariz. 85251 Filed Sept. 6, 1967, Ser. No. 665,916 US. Cl. 6153.52 3 Claims Int. Cl. E0211 5/34; E21!) 9/26 ABSTRACT OF THE DISCLOSURE A construction support system for buildings and the like comprises a cast-in-place concrete pile having an integral spiral annular shoulder and substantially undisturbed earth surrounding, frictionally engaging and supporting the pile. The concrete piles are constructed by boring a cylindrical hole, forming a spiral annular groove in the periphery of the hole and filling the bore hole with plastic concrete to form a cast-in-place concrete pile having surfaces which frictionally engage substantially undisturbed earth. The spiral groove in the bore hole is cut with an auger having groove cutters mounted on the periphery of the auger flight. The cutters collapse when the auger is rotated in the opposite direction for removal from the bore hole.

This invention relates to methods and apparatus for forming cast-in-place concrete piles and to building support structures incorporating such piles.

More particularly, the invention concerns methods and apparatus [for constructing cast-in-place concrete piles which have a spiral annular shoulder formed integrally with the pile and extending along at least a portion of the length thereof, and further concerns support structures incorporating such pilings.

In still another aspect, the invention relates to concrete pile-containing building support structures and to methods and apparatus useful in the construction thereof, which are especially adapted for use in soils having low bearing value and in which the pile derives significant support capacity by frictional engagement with the earth surrounding the pile.

In an even further aspect, the invention concerns castin-place concrete piles and methods and apparatus useful in constructing such piles which can be constructed at significantly reduced cost, with simplified methods and apparatus.

Whenever the bearing capacity of a plot of earth is insufficient to support the weight of a building without shifting or settling under the foundations of the buildings, it is common architectural construction practice to place piling under the foundation structure to distribute the weight of the building through a greater volume of earth. According to prior art practice, the pilings may be either the driven type, the screw-in type or, more commonly, the cast-in-place type.

Any pile derives its load capacity from two sources, namely, from the frictional force between the pile surface and the surrounding earth (frictional value) and from the compressive force between the end of the pile and the soil strata which underlies the end of the pile (bearing value). In certain instances, the bearing value of the soil is so low that it makes only an insignificant contribution to the load capacity of the pile, and, consequently, the pile derives all or substantially all of its load capacity from the frictional value of the earth. In other instances, the frictional value of the soil is comparatively low and the pile derives all or substantially all of its load capacity from the bearing value of the earth. In an ideal support system, the pile would exact the maximum 3,422,629 Patented Jan. 21, 1969 available load capacity from both the frictional value of the soil and the bearing value of the soil, however, low each might be. In this way, the load capacity of the support system would be the maximum available from the particular soil involved.

In general, particularly where a pile is intended to derive any major load bearing capacity from frictional engagement with the soil, it is desired that the pile surfaces contact only substantially undisturbed earth. In such cases, it is usually essential to use so-called cast-in-place piles which are constructed by excavating an elongate cylindrical bore hole and filling the resulting hole with plastic concrete which hardens to form the desired support system. Other methods of constructing pilings such as driving or screwing prefabricting piling into the earth will result in substantially disturbing the earth in the locus of the piling. Such disturbances are highly undesirable as they significantly affect the load bearing capacity of the pile in an often quite unpredictable manner.

Even some methods of forming so-called cast-in-place pilings suffer the disadvantages mentioned above in that the bore hole which is formed to receive the plastic concrete mixture is constructed by driving casings into the ground and pushing the earth aside to form the bore hole in a manner analogous to the driving of a solid prefabricated piling. This method also results in inducing disruptions of the normal soil structure to the point that the load capacity of the resulting support system is unpredictably affected.

In order to increase the load capacity of a pile without increasing the size of the pile, it has been proposed by several prior workers that vertical ribs or spiral shoulders or grooves be formed integrally in the pile structure to increase the area of contact between the pile and the surrounding earth, thereby increasing the total frictional force supporting the piling. The usual objective of such expedients is to produce a condition whereby failure will occur, if at all, between portions of the earth surrounding the pile rather than between the pile surface of the immediately adjacent earth. Thus, in accordance with recognized terminology, the desired condition would be soil-to-soil failure rather than a soil-to-pile failure as the soil-to-soil failure would be encountered only under a much higher load than would be necessary to produce the soil-to-pile failure.

However, the prior attempts to induce soil-to-soil failure by the addition of ribs, spiral grooves and shoulders and other protuberances to the pile structure have not proven to be generally satisfactory in that prior art methods and apparatus for producing such support systems have all resulted in substantially disturbing the earth in the vicinity of the pile, thereby lowering and rendering unpredictable the ultimate load capacity of the support system.

If one attempts to screw a spirally threaded pile into the ground in a manner analogous to inserting a wood screw into a piece of wood with a screwdriver, negative loadings, induced by the earth pulling the pile into the ground, are encountered. Over a period of time after the pile is screwed into the ground, these negative loadings will change as the stresses induced by these loadings are gradually distributed through the surrounding earth, thus lowering the final structural value of the support system. Also, if a pile or a pile casing is driven into the ground, the earth is displaced by the piling, thus disturbing the natural soil structure and unpredictably effecting the frictional force between the piling and the earth.

At the present time, the only generally satisfactory method of increasing the load capacity of a pile without markedly increasing the size of the pile is to form a socalled bell bottom in the pile structure. According to this technique, a cylindrical bore hole is excavated by an auger, the auger is removed and a bell-bottom tool is inserted in the bore hole, and lowered to the bottom of the hole. The bell-bottom tool excavates a bell-shaped recess in the bottom of the hole, thereby spreading the force of the load over a larger area of bearing surface and also increasing the surface area of the pile to increase the frictional force supporting the pile.

To date, the construction industry has had no suitable method or apparatus for forming a support structure which includes a cast-in-place concrete pile having a spiral shoulder to improve the load capacity of the pile. It would therefore be advantageous to provide a support system which includes a cast-in-place concrete pile having a spiral shoulder, which support structure would exact from the supporting soil both the maximum frictional value and bearing value of the soil to yield the maximum possible load capacity. It would also be highly advantageous to provide methods for constructing such support systems and apparatus for use in practicing such methods.

Accordingly, it is a principal object of the present invention to provide an improved building support system.

Another object of the invention is to provide an improved building support system which includes cast-inplace concrete pile having a spiral shoulder to improve the load bearing capacity of the system.

Still another object of the invention is to provide a method for constructing such improved building support systems and cast-in-place concrete piles.

Yet another object of the invention is to provide apparatus useful in the construction of concrete piles having spiral annular shoulders.

Yet another object of the invention is to provide building support systems which include a cast-in-place concrete pile having spiral shoulders, methods of constructing such systems and such piles and apparatus especially adapted for use in constructing such systems and piles and in which the resulting concrete pile surfaces contact undisturbed earth to improve both the actual load bearing capacity of the pile and the predictability of such capacity.

These and other, further and more specific objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings, in which:

FIG. 1 is a cross-sectional view showing the formation of a cylindrical bore hole in the earth;

FIG. 2 is a crosssectional view showing the formation of a spiral annular groove in the periphery of the bore hole of FIG. 1;

FIG. 3 is a cross-sectional view showing the introduction of plastic concrete into the spirall grooved bore hole of FIG. 2 to form the pile and support system according to the presently preferred embodiment of the invention chosen for purposes of illustration;

FIG. 4 is a perspective view of an anger assembly having grooved cutting teeth for forming the spiral annular groove as depicted in FIGS. 2 and 3;

FIG. 5 is an exploded perspective view of one of the grooved cutting teeth of the device of the auger assembly of FIG. 4;

FIG. 6 is a cross-sectional view of the grooved cutting tooth of FIG. 5 taken along section line 66 thereof;

FIGS. 7 and 8 are views of the groove-cutting tooth of FIGS. 5 and 6 after assembly; and

FIG. 9 depicts the grooved cutting tooth of FIGS. 5-8 affixed in operative position on the auger flight of the assembly of FIG. 4.

The above stated objects and advantages of my invention are accomplished by the provision of support structures and methods and apparatus for the construction of cast-in-place concrete piles which are included and form a part of such structures.

According to my invention, I construct a cast-in-place concrete pile having an elongate cylindrical portion and a spiral annular shoulder formed integrally with the cylindrical portion and extending along at least a portion of the length thereof, preferably along substantially the entire length thereof. My method comprises three steps: (a) forming a cylindrical bore hole in the earth having a radius and length substantially equal to the design radius and length of said cylindrical portion by excavating earth from said hole without substantially disturbing the earth beyond the periphery of said hole; (b) forming a spiral annular groove in the periphery of said bore hole having cross-sectional dimensions substantially equal to the design crosssectional dimensions of said shoulder by excavating earth from said groove without substantially disturbing the earth beyond the design cross-sectional dimensions of said shoulder; and (c) filling said bore hole and spiral groove with plastic concrete to form a cast-in-place pile having surfaces which frictionally engage substantially undisturbed earth.

The support system resulting from the practice of my method described above comprises in combination (a) a castin-place concrete pile including an elongate cylindrical portion and a spiral annular shoulder formed integrally with said cylindrical portion and extending along at least a portion of the length thereof; and (b) pile support means comprising substantially undisturbed earth surrounding, frictionally engaging and supporting said pile.

In the practice of my method, described above, I advantageously employ novel apparatus which is especially adapted for use in constructing concrete piles prepared by introducing plastic concrete into an elongate cylindrical bore hole in the earth, the bore hole having a spiral annular groove formed in the periphery of the bore hole along at least a portion of the length thereof. My novel apparatus comprises, in combination (a) an elongate rotatable central member; (b) means for positioning said rotatable central member coaxially within an elongate cylindrical bore hole in the earth; (0) reversible drive means for rotating said rotatable central member while simultaneously advancing said member coaxially into said bore hole at a predetermined rate of advance per revolution thereof in a first mode of operation, and, in a second mode of operation, for rotating said rotatable central member in the opposite direction and withdrawing said central member from said hole; and (d) collapsible groove cutter means carried by said central member and fixed in an operative position during said first mode of operation to excavate said spiral annular groove in the periphery of said bore hole without substantially disturbing the earth beyond the design cross-sectional dimensions of said groove, and movable to a collapsed position out of contact with the periphery of said bore hole during said second mode of operation.

As used herein, the terms without substantially disturbing the earth and undisturbed earth will be understood by those skilled in the art to connote operations and conditions which are encountered in typical earth excavating practice. For example, in boring and excavating the earth preparatory to fabricating cast-in-place concrete piles, piers and foundations, it is common to specify that such boring and excavating shall be accomplished without disturbing the earth at the periphery of the excavation and that earth which is disturbed shall be removed and replaced with concrete. From this it is commonly understood that the drilling or excavating contractor must exercise due care to avoid loosening or displacing the earth at the periphery of the excavation, such that the walls of the excavation are substantially smooth and continuous and the earth forming such walls is in substantially its natural undisturbed state of aggregation, compaction and placement. It will be further understood that the terms without substantially disturbing the earth and undisturbed earth are intended to define conditions which are clearly and distinctly different from those encountered when piling and other similar structures are pounded into or screwed into the earth or where the hole is formed by driving or screwing a casing or form into the earth. In such cases, the earth is substantially disturbed in the sense that its state of aggregation, compaction and placement are markedly altered from the natural condition.

It will be understood by those skilled in the art that minor or insubstantial disturbances in the state of aggregation, compaction and placement of the earth are often unavoidable in drilling and excavating operations. However, according to the teachings of the present invention, the natural states of aggregation, compaction and placement are not deliberately altered and minor disturbances which accidentally and unavoidably occur are not of sutficient magnitude to markedly alter the strength of the resulting support structures and are intended to be included within the scope and purview of the present invention.

Turning now to the drawings in which the preferred embodiments of the invention chosen for purposes of illustration are depicted, FIGS. l-3 illustrate the preferred practice of the method which I employ in constructing the support structures described above.

As shown in FIG. 1, the first step of my method is the formation of a cylindrical bore hole 1 by conventional means, in this case an earth-drilling auger comprising a central rotatable shaft 2 which carries a spiral screwflight 3 and which is provided with a pilot auger 4 and cutting teeth 5 at the lower end thereof. The auger can be driven by any suitable drilling rig (not shown) which transmits power through a shaft 6. The formation of the bore hole 1 in this manner is carried out by excavating the earth from the hole 1 by means of the screwflight 3 without substantially disturbing the earth 7 at a distance beyond the design radius and length of the bore hole greater than the design radius and length of the hole 1.

The next step in the construction of the support system is the formation of a spiral annular groove 11 in the periphery 12 of the bore hole 1. The spiral annular groove 11 is formed by excavating the earth to form the groove 11 without substantially disturbing the earth 7 beyond the design cross-sectional dimensions of the shoulder. As shown, the earth is excavated by a series of groove cutters 13 which slice through the earth, collapsing the excavated material inwardly where it is collected on the screwflight 14 of the groove cutter assembly. The groove cutter assembly will be described in greater detail in connection with the description of FIGS. 4-9. The groove cutters 13 are advanced into the bore hole at a predetermined longitudinal rate per revolution of the cutters to provide the desired pitch 15. The rate of advance into the bore hole per revolution of the cutters can be controlled by properly selecting the angle of attack of the cutter teeth and rotating the assembly to thread the hole in a manner analogous to tapping a hole in a piece of metal with a multiple-point, internalthreading tool. Alternatively, the rate of advance per revolution of the assembly can be externally controlled by suitable control of the movement of the drilling rig shaft 6 in a manner analogous to lathe cutting an internal thread with a single-point cutting tool.

The final step in constructing my support system is that of filling the bore hole and spiral groove with plastic concrete which hardens to form a cast-in-place pile having surfaces which frictionally engage and are supported by substantially undisturbed earth. This operation is shown schematically in FIG. 3 which illustrates pouring the plastic concrete 21 into a suitable cylindrical conduit 22 provided with a flared mouth 23. The concrete is poured through the conduit 22 to fill the hole from the bottom upwardly, thus insuring that both the bore hole 1 and the spiral groove 11 are complete filled to form the desired support system.

It will be noted that the spiral groove 11 shown in FIG. 3 extends substantially the entire length of the bore hole 1. However, it will be understood that the groove can extend only a portion of the length of the bore hole,

if desired. The location of the spiral groove can be selected to provide additional bearing value at selected points where the earth strata has a more dense structure. Preferably, the spiral annular groove extends substantially the entire length of the bore hole, thus adding bearing value over the entire length of the resulting pile, rather than only in those areas where the soil has a more dense structure.

According to the techniques herein described, I can provide a spiral annular shoulder which has a much lower pitch than can be obtained with a driven pile or driven pile casing. Thus, depending on the particular soil conditions encountered, I preferably employ a pitch of from about 40% to about of the design diameter of the cylindrical portion of the pile. In this way, I am able to materially reduce the size of the pile required to support a given load.

FIG. 4 illustrates in greater detail the construction of the auger assembly which I have devised for cutting the spiral groove in the periphery of the bore hole as generally illustrated in FIG. 2. The auger assembly comprises a rotatable central shaft 40 provided with a socket 41 at its upper end which is shaped to engage and be supported by the rotatable shaft of a drilling rig (not shown). The shaft 40 carries a spiral screwflight 42.

Groove cutters

43, 44 and 45 are fixed to the periphery of the screwflight 42. Beginning with the groove cutter 43, each successive cutter extends a greater radial distance from the central shaft 40 such that the groove is successively deepened as each cutter tracks the groove made by the preceding cutter. Each of the groove cutters is adapted to rotate in the direction of the arrows A around a pin 46 from an operative position (as shown) in which the cutters extend past the periphery of the screwflight 42 to cut the spiral annular groove in the periphery of the bore hole, to a collapsed position (shown by the dashed lines) in which the cutters are folded inwardly toward the central shaft 40 to avoid damaging the groove and periphery of the bore hole when the assembly is removed from the bore hole after cutting the groove. In order to distribute the torsional stresses, the cutters are mounted in an angularly spaced relation, as shown, preferably as close to the bottom of the auger assembly as possible in order to carry the annular groove as close to the bottom of the hole as possible. Of course, it will be understood that the exact vertical spacing of the cutting teeth will be dictated by the desired pitch of the spiral annular groove.

In operation, the groove-cutting assembly of FIG. 4 is used as follows. After the bore holehas been excavated as shown in FIG. 1, the excavating auger is removed from the hole and the assembly of FIG; 4 is fitted to the end of the drilling rig shaft by means of the socket 41. The groove-cutting assembly is then lowered to the entrance of the bore hole and an initial downward pressure in the direction of the arrow B is exerted to force the first cutter 43 into cutting engagement with the earth. Optionally and preferably, I also provide a fixed cutting tooth 47 located on the leading edge of the screwflight 42 to cut a shallow initial track for the first cutter 43. Rotation of the groove cutter assembly is commenced and the downward pressure is continued until the second groove cutter 44 is engaged in the earth in the groove made by the first cutter 43. At this point, the downward pressure on the auger assembly is adjusted to a value just sufficient to overcome frictional forces in the drive mechanism such that the entire auger assembly is advanced into the bore hole substantially only as a result of the groove cutters 44 and 45 tracking the intial groove cut made by the groove cutter 43. The

groove cutters

43, 44 and 45 are sized to cut a successively deeper groove in the periphery of the bore hole, each collapsing the soil material it cuts inwardly such that it is collected on the screwflight 42 for removal from the hole. By this technique, the spiral groove is formed in the bore hole without substantially disturbing the earth beyond the design crosssectional dimensions of the groove. The manner of forming the groove, as described above, by excavating the soil material cut by the

groove cutting teeth

43, 44 and 45 is clearly distinguishable from the formation of a groove by pushing the earth aside as would be the case if a threaded casing or a solid threaded pile were driven or screwed into the ground. In the latter case, the earth at the periphery of the groove would be substantially disturbed from its natural condition, but according to my methods, the earth is excavated from the groove leaving the surrounding earth in a substantially undisturbed condition.

When the auger assembly carrying the groove-cutting teeth reaches the bottom of the bore hole, the groovecutting

teeth

43, 44 and 45 are collapsed inwardly to the position shown by the dashed lines by reversing the direction of rotation of the auger assembly. The entire assembly can then be lifted from the hole without damaging the groove previously cut.

The construction of the individual groove-cutting

teeth

43, 44 and 45 of FIG. 4 is shown in greater detail in FIGS. 8. It will be understood, however, that the length L of each successive cutting tooth is greater, but the general proportions and arrangements of parts of each of the cutter tooth assemblies is the same.

Each of the groove cutter assemblies is mounted on a block 51 provided with threaded holes 52 which receive and engage bolts by which the assembly is attached to the auger flight. A swivel pin 53 which is butt-welded to the plate 51 extends through the clevis arms 54 of the cutter tooth. The cutter tooth is rotatably secured to the swivel pin 53 by means of a washer 55 and a press-fit cutter pin 56 extending through the hole 57 in the lower end of the swivel pin 53. A notched stop member 58 is welded to the plate 51 in a position to be received in the notch 59 in the upper clevis arm 54 of the tooth. The leading edges 61 of the tooth are sharpened to provide beveled cutting surfaces 62 which cause the earth to collapse inwardly as the tooth moves through the soil in the direction of the arrow C. The collapsed earth passes through the aperature 63 formed in the tooth, and falls onto the auger flight below the tooth where it is collected for removal from the hole. Upon reversal of the direction of rotation of the auger, the tooth rotates around the swivel pin 53 to a collapsed position Where it will not damage the periphery of the bore hole as the auger is removed from the hole.

FIG. 9 is a schematic illustration of the operative position of the groove-cutting

teeth

43, 44 and 45 showing the mounting of the assembly of FIGS. 7 and 8 upon the flight 42 to obtain the desired predetermined pitch of the annular groove 91. In order to obtain a pitch P, the tooth assembly 43 of FIG. 8 is mounted on the screwfiight 42 such that the vertical angle a is equal to the angle :1 which the spiral groove 91 makes with the horizontal. This can be conveniently accomplished by inserting a wedge-shaped spacer 92 between the tooth assembly 43 and the screwfiight 42. According to the presently preferred practice of my invention, the pitch P of the annular groove 91 varies from about 40% to about 120% of the diameter D of the bore hole and the depth D of the finished groove is from about 8% to about 22% of the diameter D of the bore hole.

It will be noticed that, as shown in the drawings, the cross section of the spiral annular groove is trapezoidal in order to facilitate completely filling the groove with plastic concrete, substantially avoiding the formation of voids in the resulting pile structure. However, it will be understood that the exact cross-sectional shape of the groove is not highly critical in the practice of my invention and the cross-sectional shape of the groove can be varied to suit particular soil conditions.

Various minor changes and departures in the devices and methods depicted above for purposes of illustration will readily occur to persons skilled in the art having regard for the disclosure hereof. To the extent that such modifications and variations do not depart from the spirt of the invention, they are intended to be included within the scope thereof which is not limited to the devices and methods specifically illustrated in the drawings but, rather, only by a just interpretation of the following claims.

Having fully described the invention in such manner as to enable those skilled in the art to understand and practice the same, the invention claimed is:

I claim:

1. A method of constructing a cast-in-place concrete pile having an elongate cylindrical portion, and

a spiral annular shoulder formed integrally with said cylindrical portion and extending along at least a portion of the length thereof,

said method comprising the steps of:

(a) forming a cylindrical bore hole in the earth having a radius and length substantially equal to the design radius and length of said cylindrical portion by excavating earth from said hole without substantially disturbing the earth beyond the periphery of said hole;

('b) 'forming a spiral annular groove in the periphery of said bore hole having cross-sectional dimensions substantially equal to the design cross-sectional dimensions of said shoulder by excavating earth from said groove without substantially disturbing the earth beyond the design cross-sectional dimensions of said shoulder; and

(c) filling said bore hole and spiral groove with plastic concrete to form a cast-in-place pile having surfaces which frictionally engage substantially undisturbed earth.

2. The method of claim 1 wherein the pitch of said groove is from about 40% to about of the design diameter of said cylindrical portion.

3. The method of claim 1 wherein the annular groove is formed along substantially the entire length of said bore hole.

References Cited UNITED STATES PATENTS 1,052,738 2/1913 McCormick 6153.64 1,172,065 2/1916 Sletten et al -292 2,912,228 11/1959 Kandle 175292 FOREIGN PATENTS 362,281 8/ 1938 Italy.

61,146 3/ 1912 Switzerland.

JACOB SHAPIRO, Primary Examiner.

US. Cl. X.R.