Abstract:
A stirring apparatus for solidifying earthen foundations. The apparatus comprises a tubular earth auger stirring rod driven by an earth auger drive shaft. A mixture of earth and hardening agents is shaped into a rectangular cross-sectional mass by an open-ended, four-sided rectangular casing. A plurality of resulting substantially hexahedral-shaped hardened masses comprise the foundation for a building structure.

Description:
This is a continuation of application Ser. No. 07/860,435, filed Mar. 30, 1992, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The field of this invention is the art of solidifying earth prior to the erection of a structure thereon. 
     2. Description of Related Art 
     It is known to adapt an earth auger to stir or to churn in place, rather than to excavate, a cylindrical column of earth. While the earth is being stirred in place, an earth solidifying agent, such as soil cement or cement milk, is mixed with the earth during the stirring process. The mixture of solidifying agent and earth hardens into a cylindrical shaft suitable to serve, together with a multiplicity of similar such cylindrical shafts, as a foundation for a building structure. 
     Since the cross section of each foundation shaft is circular and most building structures are basically rectangular, the total cross-sectional area of subjacent foundation shafts within the confines of a rectangular building structure base will be less than the cross-sectional area of the base. It has been noted that, on an average, the total cross-sectional area of cylindrical foundation shafts is approximately eighty percent of the cross-sectional area of the building structure base. As a consequence, twenty percent of the building structure is not directly supported by, or in load-bearing contact with, the foundation shafts. To compensate for this foundation bearing support differential, some builders have resorted to sinking additional foundation shafts to extend over an area wider than the building structure to be supported. This is an inefficient method of preparing a foundation. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, upper and lower stirring blades extend laterally from the outer surface of a stirring rod connected to the lower end of an excavating drive shaft. The blades are axially spaced from each other on the stirring rod and are adapted to stir and mix a hardening agent into soil loosened by the stirring blades. An open-ended, four-sided casing of rectangular cross section is secured to sleeve means exterior of, and concentric with, the stirring rod. The sleeve means is positioned between the upper and lower stirring blades and is relatively rotatable with respect to the stirring rod. The soil and hardening agent are stirred and mixed by the lower and upper stirring blades, and the mixture is shaped into a right-angle hexahedral-like form by the casing when the stirring rod is entering the earth, as well as when it is being withdrawn. In this manner, a hardened body of rectangular cross section is prepared. The ratio of the total cross-sectional area of the hardened bodies to the area of the base of the building is improved, as is the strength of the building support. As a result, neither excessively numerous hardened columns of soil nor hardened columns of soil having excessively large diameters are necessary, and the cost of the foundation work is reduced. 
     While the stirring rod is penetrating the earth, the hardening agent is introduced into the casing by the lower stirring blade. During withdrawal of the stirring rod, the hardening agent is introduced by the upper blade, so timed that the mixture is sufficiently hardened that the outer boundary of the mixture is defined by the movement of the casing through the plasticized mixture. As a result, the outer surface of the mixture is substantially hexahedral in configuration, wherein the casing acts as a sliding form such as is used for reinforced concrete construction. 
     As aforesaid, the stirring apparatus comprises the stirring rod connected to the lower end of an excavating drive shaft, upper and lower stirring blades laterally extending from the stirring rod, and an open-ended, four-sided rectangular casing interposed between the upper and lower stirring blades. The stirring rod is provided with an upper discharge hole adjacent the upper stirring blade and a lower discharge hole adjacent the lower stirring blade to discharge the hardening agent, which is fed through a hollow cavity in the stirring rod. 
     When the excavating drive shaft is rotating the stirring rod, the hardening agent is discharged mainly from the lower discharge hole. The hardening agent is first stirred and mixed into the loosened soil by the lower stirring blade that is positioned at the lower discharge hole. The mixture is shaped into a box-like form by the casing, which moves in the same direction, up or down, as the stirring rod. When the stirring rod is moving downwardly, this shaped mixture is again mixed by the upper stirring blade, which is located above the casing, and which moves downwardly with the progress of the stirring rod. Conversely, when the stirring rod is withdrawn, the hardening agent is discharged mainly from the upper discharge hole. The agent is mixed into the loosened soil by the upper stirring blade located at that position. The mixture is again shaped into a box-like form by the casing, which is located below that position and moved upward with the progress of the withdrawal. The mixture is further mixed by the underlying lower stirring blade, functioning the same as does the upper stirring blade when the stirring rod is moving downwardly. 
     Since the mixture of the loosened soil and the hardening agent is shaped into a box-like form by the casing, some of the mixture stirred within the casing tends to adhere to the inner wall of the casing, thereby spoiling the symmetry of the flat surface which the casing is intended to form. This problem is eliminated by forming an intermediate discharge hole in the outer surface of the stirring rod located between the upper and lower discharge holes, wherein it can discharge the hardening agent against the inner wall of the casing. The intermediate hole is in communication with the inside of the stirring rod, like the upper and lower discharge holes. The discharge from the intermediate hole scrapes off the mixture of the soil and agent adhering to the inner wall of the casing when the stirring apparatus moves both downward and upward. This reduces the amount of lost mixture, improves the efficiency of the mixing, and provides a better configuration of the hardened earthen shaft. 
     An intermediate stirring blade extending laterally adjacent the intermediate discharge hole can be secured to the stirring rod to direct the hardening agent discharged from the intermediate discharge hole to the inner wall of the casing, so that the adhering mixture is scraped off with greater efficiency. This intermediate stirring blade also assists the stirring by the upper and lower stirring blades. 
     When an intermediate stirring blade and an intermediate hole are used in a preferred embodiment of the invention, an upper hole is not necessary since the intermediate hole performs the same function as the upper hole. Consequently, the upper discharge hole can be omitted. 
     One of the side walls of the casing is detachably connected either to the body of the casing or to the stirring rod and can be separated from the other three side walls of the casing. By placing the open side of the casing adjacent an already formed first hardened earthen shaft, a second earthen shaft in formation can be bonded to the first already-formed shaft, so that interlocking between adjacent hardened earthen bodies is achieved. 
     After the stirring rod reaches a desired depth, the position at which the hardening agent is discharged is changed. When the stirring rod is moving downwardly into the earth, the hardening agent is discharged from the lower discharge hole. However, when the stirring rod starts to be withdrawn, means are provided to close the lower discharge hole and to open the upper discharge hole. Concurrently, the casing again shapes the mixture into a rectangular cross section, and then the rod is withdrawn. The mixture is allowed to harden into a substantially hexahedral column of hardened earth. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide stirring apparatus for forming and solidifying earthen shafts whose cross-sectional shapes are adapted to support rectangular building structures efficiently. 
     It is another object of the invention to provide a process for forming and solidifying earthen shafts using the inventive apparatus. 
     It is among other objects and features of the invention to provide apparatus for forming and hardening substantially hexahedral columns of earth suitable to provide supporting foundations for building structures. 
     The foregoing and other features of the invention will become apparent from the following description of preferred embodiments of the invention, with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a preferred embodiment of a stirring apparatus in which the apparatus has a single stirring rod; 
     FIG. 2 is a plan view of the stirring apparatus shown in FIG. 1; 
     FIG. 3 is an elevational view of a modification of the stirring apparatus shown in FIGS. 1 and 2, wherein the apparatus is provided with two juxtaposed stirring rods; 
     FIG. 4 is a plan view of the stirring apparatus shown in FIG. 3; 
     FIG. 5 is an elevational view similar to FIG. 3, but in which each stirring rod is provided with an intermediate discharge port and an intermediate stirring blade extending laterally from the stirring rod adjacent the intermediate discharge port; 
     FIG. 6 is a plan view of the stirring apparatus shown in FIG. 5; 
     FIG. 7 is an elevational view similar to FIG. 5, but in which no upper discharge ports are provided; 
     FIG. 8 is a plan view of the casing of the stirring apparatus shown in FIGS. 1 and 2, and in which the casing is detachably connected to the stirring rod; 
     FIG. 9 is a plan view of the casing of the stirring apparatus shown in FIGS. 3 and 4, in which the casing is detachably connected to the stirring rods; and 
     FIG. 10 is a perspective view of completed hardened hexahedral columns of earth which are bonded together by means of a modified casing in accordance with a preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring to FIGS. 1 and 2, there is shown a stirring apparatus according to the invention. This apparatus is generally indicated by A and comprises an earth auger stirring rod 1 provided with a six-sided driving end 1d for connection with the lower drive end of an auger drive shaft (not shown); an upper stirring blade 2; a lower stirring blade 3; and an open-ended casing 4 comprising four vertical rectangular sides 4a-d, FIG. 2. The stirring blades 2 and 3 project laterally from the stirring rod 1. The upper blade 2 is spaced from the lower blade axially of the stirring rod 1. The stirring rod 1 is tubular with an inner passageway 1c. Holes 1a and 1b connect passageway 1c with the outer surface of the stirring rod 1 adjacent stirring blades 2 and 3, respectively. A fluid hardening agent is passed through passageway 1c and holes 1a and 1b for discharge into the earth being loosened by the stirring blades 2 and 3. The casing 4 is vertically positioned between the upper blade 2 and the lower blade 3 and spaced from the stirring rod 1 as shown in FIG. 2, such that the casing 4 is isolated from the rotation of the stirring rod 1. An excavating bit 1e is connected to the lower end of the stirring rod 1 to initially penetrate and to loosen the earth prior to penetration and stirring by stirring blades 2 and 3. 
     An upper housing 5 and a lower housing 6, to which the upper stirring blade 2 and the lower stirring blade 3, respectively, are secured, are telescopically mounted around the outer surface of the stirring rod 1. The upper housing 5 and the lower housing 6 are provided with an upper discharge hole 5a and a lower discharge hole 6b, respectively, at positions corresponding to the upper discharge hole 1a and the lower discharge hole 1b, respectively, of stirring rod 1. The discharge hole 5a is alignable with discharge hole 1a and discharge hole 6b is alignable with discharge hole 1b. In the illustrated embodiment, these discharge holes 1a, 1b, 5a, and 6b extend normal to the axis of the stirring rod 1 to discharge the fluid hardening agent into the earth previously loosened and stirred by stirring blades 2 and 3. 
     The upper stirring blade 2 and the lower stirring blade 3 extend laterally adjacent the upper discharge hole 5a and the lower discharge hole 6b, respectively, formed in the upper housing 5 and the lower housing 6, respectively. Consequently, the stirring blades 2 and 3 also act to disperse the hardening agent discharged into the loosened earth. 
     In order to perform the stirring efficiently, the stirring apparatus A discharges the hardening agent primarily from the lower discharge hole 1b while the stirring rod 1 is being driven into the earth and primarily from the upper discharge hole 1a when the stirring rod 1 is being withdrawn from the earth. The hardening agent discharged from the lower discharge hole 1b is stirred with the lower stirring blade 3 until the stirring rod 1 reaches a predetermined depth in the earth, and then by the upper stirring blade 2 while the stirring rod 1 is being withdrawn. The hardening agent is discharged from the upper discharge hole 1a when the stirring rod 1 is being withdrawn and is stirred with the upper blade 2 to be followed by stirring by the lower blade 3 after the discharging of the hardening agent. In this way, the hardening agent is efficiently mixed into the loosened and stirred earth both during the advancing and withdrawing of stirring rod 1 and blades 2 and 3. 
     In the illustrated embodiment, the housings 5 and 6 are slidably fitted on stirring rod 1 so that holes 1a and 1b are alternately opened and closed by housings 5 and 6. Thus, as shown in FIG. 1, as the stirring rod 1 penetrates the earth, the friction of the earth against housings 5 and 6 causes them to shift vertically up on stirring rod 1, causing hole 6b to align with hole 1b and hole 5a to shift out of alignment with hole 1a. In this first mode, hardening agent is blocked from passing through holes 1a and 5a and is permitted to pass through holes 1b and 6b. When the stirring rod 1 is withdrawn, housings 5 and 6 are shifted downwardly due to friction with the loosened earth, whereupon the relationship of holes 1a and 5a, and 1b and 6b reverse. Hole 5a is shifted into alignment with hole 1a and hole 6b is shifted out of alignment with hole 1b. Thus, hole 1a is opened and hole 1b is closed to flow of the hardening agent. 
     The upper housing 5 and the lower housing 6 are connected together by sleeve 14, as shown in FIG. 1. A tongue-like detent 7 protrudes from the outer surface of the stirring rod 1 and a groove 8 in housing 6 receives detent 7 which permits sliding movement therebetween because it is longer than the detent 7. Since housings 5 and 6 are rigidly connected together, the detent 7 and the groove 8 enable the upper housing 5 and the lower housing 6 to shift vertically in unison a predetermined controlled distance on the body of the stirring rod 1. The difference in length between the groove 8 and the detent 7 provides the stroke of the movement of the housings 5 and 6 relative to the stirring rod 1. 
     FIG. 1 indicates the positions of the upper housing 5 and the lower housing 6 when the stirring rod 1 is being driven into the earth. In this condition, the housings 5 and 6 shift upwardly relative to the stirring rod 1 by the resistance of the loosened earth. The lower end of the groove 8 engages the lower end of the detent 7, which causes both housings 5 and 6 to shift upwardly in unison on stirring rod 1, the distance defined by the differential between the length of the detent 7 and the groove 8. The lower discharge hole 6b in the lower housing 6 registers with the lower discharge hole 1b in the stirring rod 1 as shown, and the upper discharge hole 5a is shifted beyond alignment with upper discharge hole 1a. Since the upper discharge hole 1a is closed by the upper housing 5, the hardening agent can be discharged only through the lower discharge holes 1b and 6b. 
     Conversely, when the stirring rod 1 is being withdrawn, the upper housing 5 and the lower housing 6 shift downwardly relative to the stirring rod 1. The upper discharge hole 5a registers with the upper discharge hole 1a and the lower housing 6 closes the lower discharge hole 1b. The hardening agent is therefore discharged only from the upper discharge holes 1a and 5a. 
     As shown in FIGS. 1 and 2, bearing 9 slip-fits over stirring rod 1 to isolate the casing 4 from rotation of the stirring rod 1. The casing 4 is welded or bolted to horizontal brace members 10 extending laterally from the bearing 9. The resistance of loosened earth prevents the casing 4 from turning with the stirring rod 1. 
     As shown, the casing 4 is large enough to permit satisfactory molding of the mixture of the loosened earth and the hardening agent during movement of the stirring rod 1. The lower end of the casing 4 is saw-toothed, as shown in FIG. 1 at 4e, to reduce the resistance of the loosened earth when the stirring rod 1 is urged downward. When the stirring rod 1 engages the earth, the knife edge 4e of the casing 4 cuts the mixture of the loosened earth and the hardening agent along the outer surface of the casing. At the same time, the mixture is forced into the casing 4 by the knife edge 4e and is formed by the casing into a substantially hexahedral shape. When the stirring rod 1 is withdrawn, the mixture is once again stirred and reshaped into a substantially hexahedral mass by the casing 4. 
     Referring next to FIGS. 3 and 4, there is shown a twin-auger stirring apparatus B in which stirring rods 1L and 1R are juxtaposed. This apparatus B is similar to the single-auger type stirring apparatus A described previously except that the casing 4A has an elongated longitudinal axis and a foreshortened tranverse axis. 
     Referring to FIGS. 5, 6 and 7, there is shown a stirring apparatus C which is similar to the apparatuses A and B except that a vertically elongated intermediate discharge hole 1d is formed in each stirring rod 1 between the upper discharge hole 1a and the lower discharge hole 1b. The hardening agent is discharged from this intermediate hole 1d through intermediate hole 5d of upper housing 5 toward the inner wall of the casing 4B to prevent or reduce adhesion of the loosened earth or the mixture to the inner wall of the casing 4B, thereby enhancing the efficiency of the mixing of the earth and hardening agent. The hardening agent is discharged from intermediate holes 1d and 5d during both downward and upward movement of the stirring rod 1. 
     The discharge from the intermediate holes 1d peels the loosened earth and/or the mixture from the inner wall of the casing 4B. This peeling operation is most efficiently performed while the stirring rods are being withdrawn, i.e., during upward movement. As aforesaid, in the structure shown in FIG. 5, the upper housing 5 is formed with intermediate discharge holes 5d which register with the intermediate discharge holes 1d when the stirring rods 1 are being withdrawn. In this way, the hardening agent is discharged from these intermediate holes as well as from the upper discharge holes 1a and 5a. However, either or both of the intermediate discharge holes 1d and 5d in the stirring rods 1 can axially take the form of vertically elongated slots wherein the hardening agent can then be discharged from the intermediate holes 1d and 5d whether the stirring rods 1 are moving upward or downward. 
     In the illustrated embodiments, intermediate stirring blades 11 are adjacent to, and extend laterally from, the intermediate discharge holes 1d and 5d to guide the hardening agent discharged from the intermediate discharge holes 1d and 5d to the inner wall of the casing 4B. The intermediate blades 11 also serve to assist the stirring of the lower stirring blades 3 when the stirring rods 1 are being lowered and to assist the stirring of the upper stirring blades 2 when the stirring rods 1 are being elevated. 
     Since the intermediate stirring blades 11 stir the mixture simultaneously with the hardening discharge from the intermediate discharge holes 1d and 5d, the intermediate discharge holes 1d and 5d perform the function of the upper discharge holes 1a and 5a. Consequently, in the embodiment of FIG. 7, the upper discharge holes 1a and 5a may be eliminated. 
     In the embodiment shown in FIG. 8, side 4e can be detached from sides 4f, g and h of a pair of casings to form the expanded casing 4D of FIG. 9. In another embodiment of the invention, side 4e of FIG. 8 is detached from sides 4f, g and h so that casing 4E can be used in the lapping process shown in FIG. 10. Therein shown is semi-hardened earthen shaft S-L to which a second hardened earthen shaft S-R is to be lapped and bonded. The procedure is substantially the same as the procedure described with respect to FIGS. 1 and 2 except that the three-sided casing is positioned with the open side adjacent the vertical face F to overlap vertical face F by the lateral distance K. After earthen shaft S-R has been completed, the common portions of shafts S-R and S-L, indicated at K, are then permitted to harden together, whereby shaft S-R is permanently bonded to shaft S-L. This procedure, of course, can then be repeated with earthen shaft S-R being the semi-hardened shaft to which a third earthen shaft can be lapped and bonded in the same manner that earthen shaft S-R was previously bonded to earthen shaft S-L. 
     The two earthen shafts S-L and S-R can also be formed simultaneously with the apparatus shown in FIGS. 3 through 7, 9 and 10, as previously described. By removing one side 4g of FIG. 9, the lapping process can be practiced by forming rectangular shafts rather than the substantially square shafts of FIG. 10, as formed by the apparatus of FIG. 8. 
     The specification and drawings disclose preferred embodiments of the invention. However, various features, details and elements may be changed or eliminated without departing from the invention as defined in the accompanying claims.