US3442089A - Method for casting concrete foundation - Google Patents

Description

May 6, 1969 A. A. SOLLAY 3,442,089

` METHOD FOR CASTING CONCRETE FOUNDATION Filed Jan. 25, 1967 NM V NM .ggf

ATTORNEYS 3,442,089 METHOD FOR CASTING CONCRETE FOUNDATION i Alva A. Sollay, P.O. Box 5731, Drew Station, Lake Charles, La. 70601 Filed Jan. 25, 1967, Ser. No. 611,681 Int. Cl. E02d 5/34; E04b 1/16 U.S. Cl. 61-53.64 9 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a concrete foundation for buildings, bridges and other structures, which comprises a cast in situ, at least mostly subterranean, annular concrete pillar having a removable central core of sand or similarly substantially non-cohesive material supported upon an axially short cast-in-situ concrete plug. The invention also relates to a method for forming the foundation which comprises digging, drilling or otherwise forming a shaft in the earth, placing a smaller O.D. tubular casing in the shaft, filling the shaft/casing annulus with concrete, pouring an axially short plug of concrete into the casing throughbore; depositing sand or a similarly noncohesive, non-cementitous coring, filler material into the casing throughbore above the plug to substantially lill the throughbore; longitudinally removing the casing; allowing the concrete to harden and preferably removing the coring. This abstract, because of its brief and introductory nature, should not be construed as being all inclusive or as in any way limiting the scope of the claims appended to this specication or the range of applicability of the principles described herein. This abstract is chiefly intended as an aid to persons scanning this document for the rst time in quickly ascertaining whether the disclosure on this document may warrant their further study.

BACKGROUND OF THE INVENTION Concrete foundations of the general type over which the present invention is an improvement are those used to support buildings, bridges, and such structures. Customarily, such prior art foundations have been formed in place by boring, drilling or otherwise forming a vertical shaft in the earth and filling the shaft with concrete. After the concrete has hardened, the intended structure can be supported thereon. The inventor herein has found that the concrete along the longitudinal centerline of such prior art foundations, at least over most of the depth of such foundations can be eliminated without a corresponding sacrifice in strength when the considerations related hereinafter are described.

OB] ECTS OF THE INVENTION It is an object of the invention to provide an improved foundation for buildings, bridges and the like which is easy to emplace and which is conservative of expensive materials.

Another object of the invention is the provision of a method for casting annular, mostly subterranean, concrete foundations in situ which provides necessary forms for the concrete but allows for their removal while the concrete is still unhardened.

A further object of the invention is the provision of an annular mostly subterranean cast-in-place concrete foundation having a concrete plug blocking the lower end of the bore of the annular concrete member and a core of sand or like -material supported upon the plug at least until the concrete of the annular member has hardened.

DEFINITIONS As used herein the term concrete is intended to encompass the material brought into being when portland 3,442,089 Patented May 6, 1969 ICC cement, water and sand plus gravel, crushed stone or other aggregates are mixed together; the term is also intended to encompass such materials wherein portland cement is replaced in whole or in part by other cements known in the construction industry to be useful for such replacement. An exemplary enumeration of cements can be found under the heading Cement, Types of Cement, on pages 690-697 of Kirk-Othmer, Encyclopedia of Chemical Technology, vol. 4, 2nd Ed.,I Interscience Publishers, Division of John Wiley and Sons, Inc., New York 1964).

SUMMARY OF THE INVENTION The present invention has both method and article aspects.

The method of the present invention includes:

(a) Making a shaft in the earth;

(b) Inserting a tubular casing in the shaft so as to extend throughout substantially the full depth of the shaft said casing having an external diameter that is smaller than the diameter of said shaft, thereby defining a shaft/ casing annulus exteriorly of the casing;

(c) Filling plastic unhardened concrete into the annulus;

(d) Depositing an axially short plug of plastic unhardened concrete in the casing interiorly thereof at the lower end thereof;

(e) Filling the casing interiorly thereof above said plug with a substantially non-cohesive, granular material substantially to the height of concrete in said annulus.

The foundation according to this invention comprises hole means defining a shaft in the earth, said shaft hav ing a peripheral sidewall; a monolithic annulus of concrete cast in place in the shaft, having a longitudinal central bore, and having the external peripheral surface thereof in engagement with said shaft peripheral sidewall, said bore -being large relative to the thickness of said annulus of concrete, the upper end of said annulus of concrete being located to receive and support a structure.

These and other aspects of the present invention will become more clearly apparent, as will the principles and scope of applicability of the invention, during the course of the following detailed discussion which is keyed from time to time to the preferred embodiments of the invention that are shown in the attached drawing.

In the drawing:

FIGURE 1 is a vertical sectional view of part of the earth near the surface showing in longitudinal section a shaft in the earth, a tubular casing in the shaft and concrete being poured about the shaft/casing annulus;

FIGURE 2 is a sectional view similar to FIGURE 1 showing a succeeding stage wherein a plug of concrete has been poured in the casing and a core of dirt has been used to fill the casing, above the plug;

FIGURE 3 is a sectional view showing a further stage wherein the casing has been longitudinally upwardly withdrawn from the shaft;

FIGURE 4 is a sectional view which shows a completed foundation according to the present invention, wherein the dirt core has been removed subsequent to hardening of the concrete and a structure is supported upon the foundation; and

FIGURE 5 is a sectional view similar to FIGURE 1 of an early stage in the formation of La foundation according to a second embodiment of the invention wherein the subterranean formation is unstable.

When soil conditions are such that a shaft can be made in the earth without substantial seepage into, caving-in or leakage from it, the steps now to be discussed in regard to FIGURES 1-4 are advantageously useful. Referring to FIGURE 1, as a first step, a hole or shaft 10 is sunk, drilled, dug or otherwise formed in the earth typically being about forty feet deep and of about five feet in diameter. Next a tubular casing 12, typically of steel, having an O.D. of less than the diameter of the shaft, typically of about four feet O.D., is lowered into the shaft so as to bottom longitudinally centrally therein and extend to the mouth 14 of the shaft 10.

Then plastic, unhardened concrete 15 is pumped into the annulus 16 between the casing exterior 18 and the shaft peripheral sidewall 20 to fill the annulus. If desired, an intermediate tubular Ibody of reinforcing wires can be disposed in the annulus 16 prior to pouring of the concrete 15. An axially short plug or point 22 of plastic, unhardened concrete (FIGURE 2) is preferably pumped at about this same time into the bore 24 of the casing 12, landing at the bottom thereof. The concrete 1S, 22 is advantageously ready-mixed and poured directly from a conventional mixer-transporter truck T from adjacent the shaft mouth 14. In this example, the plug 22 is typically about 3 4 feet thick. The remainder of the casing bore 24 is filled with sand, loam, clay, dirt or similarly non-cohesive granular material 26.

Preferably, before the concrete 15, 22 has hardened, the casing 12 is longitudinally withdrawn (FIGURE 3) from the shaft 10, whereupon the bodies of plastic concrete 15 and 22 merge into one monolithic body. The sand or similar material 26 prevents implosion of the plastic concrete as the casing 12 is withdrawn and thereafter prevents inward collapse of the plastic concrete, giving the latter opportunity to harden.

For certain applications, the sand or similar material 26 can be left in place after the concrete 15, 22 has hardened and a structure such as a house, bridge abutment, bridge, pier, office, apartment or factory building slab supported thereon. Of course in most of the instances just mentioned several foundation elements laterally spaced from one another would need be employed to support one structure. In most instances, the sand or similar material 26 can be removed from interiorly of the cement annulus, once the cement has hardened (FIGURE 4).

This aspect of the invention may be more readily cornprehended upon reference to the following example.

Example I Three approximately forty foot deep, five foot wide shafts were sunk in the earth near Lake Charles, Louisiana. Concrete of the following composition was prepared:

The first shaft was peripherally cased and filled with the concrete which was allowed to harden. The second and third foundations were completed according to the invention as just described above, the difference between them being that sand 26 was left in the second foundation and removed from the third subsequent to the hardening of the concrete thereof. The concrete weighed about 140 pounds per cubic foot and the sand weighed about 100 pounds per cubic foot, so the second and third foundations weighed substantially less than the first.

It was found that a safe design load on the shafts is SOO-750 pounds per square foot of contact surface about the circumference of the respective shaft. With the foundations of the invention, the difference of the weight of the concrete put into the shaft and the soil taken out was computed and this extra weight added to the column load. Thus the sand filled core was found to be able to carry more column load than the solid concrete shaft and the hollow core shaft was found to 4be able to carry even more column load.

Referring now to FIGURE 5, in instances where leakage of water into the shaft 10, evident looseness of the soil peripherally of the shaft 10 or porosity of the shaft sidewall make the soil about the shaft periphery unstable, the shaft sidewall can advantageously be treated by owing water, or bentonite mud, lime, hydraulic cement or other stabilizing slurries thereagainst and allowing the excess to drain to the bottom of the shaft. A tubular casing 28 having an O.D. only slightly less than the diameter of the shaft 10 is lowered into the shaft 10.

A casing 12 is then emplaced as described with respect to FIGURES l-4 and the foundation of FIGURE 5 completed as described with respect to FIGURES l-4, the concrete 15 filling the annulus between the casings 12 and 28. The incoming concrete displaces the excess treating fluid up and out of the shaft. Preferably the casing 28 is withdrawn at about the same time the casing 12 is withdrawn. As shown in FIGURE 5, either or both the exterior of the casing 12 or interior of the casing 28 is provided with at least one nearly coextensive longitudinally extending pipe 30. In emplacing the concrete 15, the plastic, unhardened concrete is pumped from the surface down the pipe or pipes 30 and out the outlet 32 thereof near the bottom 34 of the shaft 10.

It should now be apparent that the invention described herein fulfills all of the objects set forth at the beginning of this specification and that the description herein clearly relates the principles of the invention. Because the ernbodiments shown and described can be considerably modified without departing from these principles, the present invention should be understood as encompassing all such modifications as are within the spirit and scope of the following claims.

What is claimed is:

1. A method for constructing a foundation comprising:

(a) making a shaft in the earth;

(b) inserting a tubular casing in the shaft, so as to extend throughout susbtantially the full depth of the shaft, said casing having an external diameter that is smaller than the diameter of said shaft, thereby defining a shaft/ casing annulus exteriorly of the casing;

(c) filling plastic,

annulus;

(d) depositing an axially short plug or plastic unhardened concrete in the casing interiorly thereof at the lower end thereof;

(e) filling the casing interiorly thereof above said plug with a substantially non-cohesive, granular material substantially to the height of concrete in said annulus.

2. The method of claim 1 comprising as further steps:

(f) longitudinally withdrawing the casing from the shaft before the concrete has hardened;

(g) allowing the concrete to harden.

3. The method of claim 2 comprising as a further step:

(h) removing the substantially non-cohesive, granular material from within the annulus of concrete.

4. The method of claim 3 comprising as a further step disposing and supporting a structure on the upper end of said annulus of concrete.

5. The method of claim 2 further comprising, prior to step (c): inserting a second tubular casing in the shaft, coaxially with the first-mentioned tubular casing, said second tubular casing having an external diameter that is only slightly smaller than the diameter of said shaft, thereby defining the radially outer extent of said shaft casing annulus.

6. The method of claim 5 further comprising, approximately concurrently with step (f): longitudinally withdrawing the second tubular casing from the shaft before the concrete has hardened.

7. The method of claim 6 further comprising: prior to step (b) directing a flow of lighter-than-unhardenedconcrete soil stabilizing fluid against the peripheral sidewalls of said shaft and approximately concurrently with step (c) displacing excess of said uid from said shaft/ unhardened concrete into the casing annulus with the concrete lled into said shaft/ casing annulus.

8. The method of claim 7 wherein the soil stabilizing fluid is one chosen from the group consisting of water, bentonite mud slurry, lime slurry and hydraulic cement slurry.

9. The method of claim 5 further comprising: fastening a generally longitudinally extending pipe on at least one of the exterior of said rst-mentioned tubular casing and the interior of the second tubular casing oriented so that when said casings are bottomed in said shaft, said pipe has an outlet to said shaft/casing annulus near the bottom of said shaft/casing annulus and an inlet near the upper end of said shaft/casing annulus; and wherein 6 References Cited UNITED STATES PATENTS S/1901 Mouche] 61-56 1/1930 Newton 61-53.66 3/1930 Smith 61-53.64 5/1933 Newman 61-53.64 4/ 1936 Christie 61-56 FOREIGN PATENTS 2/ 1908 Germany.

JACOB SHAPIRO, Primary Examiner.

U.S. Cl. X.R.

step (c) comprises pumping concrete down said pipe and 15 61-50; 264-31 out the outlet thereof.

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