Pile head treating tool for cast-in-place and pile head treating method

Abstract: A pile head dresser for cast-in-place concrete piles has an inner cylinder 2 arranged for allowing a tremie pipe 16 to move in and out, and surrounded at a distance by an outer cylinder 3, and a top plate 1 and a bottom plate 6 joining the two cylinders 2 and 3 at top and bottom respectively to form a double cylinder structure A, the bottom plate 6 having a plurality of reinforcement bar apertures 8 provided therein at equal intervals of a distance, and the top and bottom plates 1, 6 having exhaust apertures 5 and 9 respectively provided therein for passing a mixture of air and slurry.

Description: FIELD OF THE INVENTION The present invention relates to a pile head dresser which is mounted to the head of a steel cage of a cast-in-place concrete pile installed in the ground for making a foundation of civil engineering work, to a method of dressing the head of such a concrete pile, and to improvement in placement of such a pile. BACKGROUND ART In common construction work, a variety of methods are used for driving and installing foundation piles. Among of them is a popular cast-in-place pile installation method. The cast-in-place concrete pile installation method comprises drilling a round hole to a bearing base layer in the ground by an earth drilling technique, installing in the drilled round hole a steel cage consisting of a framework assembly of reinforcement bars, and filling the hole with a batch of concrete which is supplied through a tremie pipe having been inserted from above into the steel cage and turns to a reinforced concrete pile when solidified. In general, the batch of concrete is abundant thus having an extension of about 1 meter high above the steel cage of the concrete pile. The concrete pile with the extension is covered with refilling soil for curing. After the curing of the concrete is completed, the soil is removed and the concrete extension is chipped off to expose the reinforcement bars at top of the steel cage. Foundation of a building structure is then built on the concrete piles. The chipping of the concrete extensions however creates unwanted sounds, vibrations and dust and is regarded as a public nuisance source. Also, it may injure the reinforcement bars and cause labor accident and industrial illness. The concrete extensions claim a considerable amount of concrete and their chipping procedure will increase the overall construction cost and time. A method of eliminating the chipping procedure is disclosed in Japanese Patent Application 61-186616 (1986) where the concrete extensions are removed while their concrete supplied through a tremie pipe remains in a viscous fluid form before solidified by vacuum suction with a suction hose coupled to a heavy-duty vacuum pump. The method is only feasible with the use of a casing provision installed in the drilled hole and not satisfactorily applicable to any different case where the drilled hole may easily be collapsed. According to the method, the reinforcement bars are exposed and directly assaulted by refilling soil when the concrete extensions have been removed. Also, the removal of the concrete extensions requires a large machinery which may easily injure the top of the exposed reinforcement bars. As the injured reinforcement bars have to be amended with extra care and cost, the method will be rather impractical. To prevent such damage to the exposed reinforcement bars during the chipping or removal of concrete extensions, a reinforcement bar cap structure has been introduced as depicted in Japanese Patent Application 58-153816 (1983). The cap has a through hole provided in the center thereof for accepting and detachably coupling a tremie pipe. The cap comprises a closed double-wall structure of a doughnut shape having two separate rooms or spaces about the center hole which are defined by two, top and bottom, annular plates one of which provided with apertures. In use, joint bolts are inserted through the apertures of the bottom plate of the cap and threaded into sleeve joints of which rear ends are mounted to the uppermost ends of reinforcement bars of a steel cage so that the cap structure and the steel cage are tightly joined to each other. This is followed by introduction of a flow of concrete through a tremie pipe. The flow of concrete into the steel cage is continued until the cap structure on the top of the steel cage is filled up. For curing the concrete in the steel cage, the steel cage and the cap are covered with refilling soil. When the concrete has been cured, the refilling soil is removed to expose the cap. The concrete in the cap structure is chipped off and retaining screws are removed for unlocking the cap. After the joint bolts are separated from their respective sleeve joints, the cap structure is removed. Anchor bars are then threaded into the sleeve joints so that they extend upright from the reinforcement bars. With the use of such a cap structure, the extensions of concrete piles are decreased in size but still require a chipping process for removal. The cap structure is not simple as includes two parts which are joined to each other using side plates in an extra step of procedure. The anchor bars are threaded into their respective sleeve joints in order to increase a total length of the reinforcement bars. This is a delicate means because it is hardly verified in mechanical strength as depending much on experimental skills. If worse, the means may create critical accidents. It is said that the means is still under way to clear all the technical drawbacks. Some modifications of such a cap structure or a pile head dresser (the former being used hereinafter) for use in installing bearing piles have been developed, including one which is invented by us as disclosed in Japanese Patent Application 1-322020 (1989), on which the preamble of appended claim 1 is based. The cap structure invented previously by us, unlike the conventional cap of a doughnut shape having two separate spaces and disclosed in the prescribed application 58-153816, comprises an inner cylinder (tremie pipe introducing tube) arranged open at upper and lower ends for freely accepting a tremie pipe, and an outer cylinder (cap upper) disposed outwardly of the inner cylinder for coupling top and bottom plates, thus forming a simple double-cylinder structure. Also, the bottom plate has a plurality of reinforcement bar apertures provided in an outward region thereof (cutting projected face dish) (the terms in parenthesis represent counterparts in the previous Application). Our previous cap structure of a cylindrical shape has a size substantially equal to the concrete extension and greater in depth than the conventional cap (structure) shown in the Application 58-153816. In use, the cap structure is fitted onto the reinforcement bars so that its top plate comes in direct contact with the top of the reinforcement bars. Then, a tremie pipe is inserted into the inner cylinder for placement of concrete without making a concrete extension. For curing the concrete, the cap structure is covered with refilling soil. After the curing is completed, the refilling soil is removed to expose the cap structure. As the chipping work is not needed, the reinforcement bars are exposed without troubles when the cap structure has carefully been dismounted. It is only requested to remove a remaining of concrete slime from the bottom of the inner cylinder by an applicable means while care being taken not to injure the reinforcement bars. After other unwanted deposition and slurry are removed, the concrete placement is finished. It is well known that a conventional method of concrete placement comprises the steps, shown in Fig.19(A) to 19(G), of placing a surface protective casing 78 and a steel cage 7C in a drilled hole 7A, removing a sediment of slime 70 from the bottom by means of an air lift or suction pump, and filling the drilled hole with a batch of concrete 7F supplied through a tremie pipe 7E. Also, an extension of concrete 7G is added to the pile concrete 7F for a predetermined height during the filling step. The concrete extension 7G contains impurities of slime and laitance and has to be chipped off after solidified. The step of removing the slime sediment from the bottom is necessary for avoiding declination of the quality of a finished concrete pile caused by residual slime. It may be executed by suction with a known air lift or suction pump. Simultaneously, it is needed to replace the slime sediment with a fresh supply of water for preventing lowering of a water level which may cause collapse of the inner wall. This will disturb the efficiency in carrying out the step. Technically, the removal of the entire slime sediment is very difficult and the concrete extension 7G is provided for compensation. Our previous cap structure disclosed in the Application 1-322020 is designed for protecting the head of a pile as well as eliminating forming and chipping of the concrete extension which are essential in the prior art. Accordingly, as the chipping process is eliminated, no environmental harassment will occur. Also, the overall procedure will be decreased and the consumption of concrete will be minimized, increasing the cost performance. It is still troublesome to remove the remaining of concrete slime from the inner cylinder when the concrete has been placed, covered, and solidified. Although the removal of the remaining concrete slime is carried out by as a simple manner as drilling the concrete along a cut line, splitting it with the use of wedge laggings or expanders, and lifting up the split concrete slime with ropes, it may preferably be omitted. The bottom of the previous cap structure is flat and will be likely to accumulate and hold sediments of concrete slime or impurities. It is also essential to allow a liquid stabilizer used for preventing collapse of the inner wall and a water inflow welling up to pass smoothly through the cap structure and between the cap structure and the casing without exerting as a smaller pressure as possible on the cap structure. It is thus an object of the present invention to solve the foregoing problems attributed to the previous cap structure of a closed form having only reinforcement bar apertures. It is another object of the present invention to provide an improved concrete placement method which excludes the procedure of removing sediments of concrete slime and allows a minimum of slime to enter the concrete. DISCLOSURE OF THE INVENTION For achievement of the object of the present invention, the followings are invented. As defined in claim 1, a pile head dresser for cast-in-place concrete piles according to the present invention comprises an inner cylinder 2 arranged for allowing a tremie pipe 16 to move in and out, and surrounded at a distance by an outer cylinder 3, and a top plate 1 and a bottom plate 6 joining the two cylinders 2 and 3 at top and bottom respectively to form a double cylinder structure A, the bottom plate 6 having a plurality of reinforcement bar apertures 8 provided therein at equal intervals of a distance, and the top and bottom plates 1, 6 having exhaust apertures 5 and 9 respectively provided therein for passing a mixture of air and slurry. As depicted in claim 2, a pile head dresser for cast-in-place concrete piles according to the present invention has a construction identical to that of claim 1 and is arranged in which while the inner cylinder 2 and the outer cylinder 3 are equal in the length to each other, the top and bottom plates 1, 6 extend horizontally between the two cylinders 2 and 3. As defined in claim 3, a pile head dresser for cast-in-place concrete piles according to the present invention is characterized by a cap structure A of a double cylinder construction which comprises a top plate 1 of an outer cylinder 3 having a plurality of exhaust apertures 5 provided in an outward edge region thereof for passing a mixture of air and slurry and also an upper tremie opening 4 provided in a center thereof for allowing a tremie pipe 16 to move in and out for supplying a batch of concrete for placement, and an inner cylinder 2 having both ends thereof opened and arranged shorter 2% to 3% than the outer cylinder 3. In particular, the outer cylinder is coupled to a bottom plate 6 which has a plurality of reinforcement bar apertures 8 provided in an outward edge or flat region 6a thereof at equal intervals of a distance and a plurality of slits 9 provided at equal intervals of a distance and extending radially from a lower tremie opening 7 formed in a center of the bottom plate 6 to the flat region 6a thus to define a group of slit tabs 9a. The slit tabs 9a are folded upward to tilt and their distal ends are welded to the lowermost ends of the inner cylinder 2. As defined in claim 4, pile head dressers for cast-in-place concrete piles have substantially the same constructions as of claims 1, 2, and 3 respectively and are arranged in which the top plate 1 and/or bottom plate 6 is made of a mesh or perforated metal sheet. As defined in claim 5, pile head dressers for cast-in-place concrete piles have substantially the same constructions as of claims 1 to 4 respectively and are arranged in which the cap structure A is mounted on and fixedly tied to the steel cage 14 by at least a pair of detachable chains, wires, or cables 2 and 3 before both are installed in the drilled hole 17. As defined in claim 6, pile head dressing methods for cast-in-place concrete piles according to the present invention employ the pile head dressers of claims 1 to 5 respectively and comprise joining the cap structure A to the steel cage 14 by stud welding, installing both in the drilled hole 17, inserting the tremie pipe 16 through the inner cylinder 2 of the cap structure A into the drilled hole 17, pouring a batch of concrete continuously into the same until the level of the concrete rises from the bottom of the drilled hole 17 to the top of the inner cylinder 2, and removing sediments of concrete slime from the inner cylinder 2 without delay by a rotating action of the digger bucket 18 mounted to a kelley bar 19. BRIEF DESCRIPTION OF DRAWINGS Fig.1 is a perspective view of a cap structure; Fig.2 is a partially cut-off perspective view of the cap structure; Fig.3 is a plan view of a bottom plate of an outer cylinder of the cap structure before it being bent; Fig.4 is a partially cut-off longitudinal cross sectional view of the cap structure; Fig.5 is an explanatory view showing the cap structure in use; Fig.6 is another explanatory view showing the cap structure in use; Fig.7 is an explanatory view showing removal of concrete from the cap structure; Fig.8 is a partially cut-off perspective view of another embodiment of the cap structure denoted by A; Fig.9 is a partially cut-off perspective view of a further embodiment of the cap structure A; Fig.10 is a partially cut-off perspective view of a still further embodiment of the cap structure A; Fig.11 is a partially cut-off perspective view showing a still further embodiment of the cap structure A in use; Fig.12 is a perspective view showing a still further embodiment of the cap structure A in use; Fig.13 is a perspective view showing a still further embodiment of the cap structure A in use; Fig.12 is a perspective view showing a still further embodiment of the cap structure A in use; Fig.13 is a cross sectional view showing a procedure of carrying out the drilling steps of a cast-in-place concrete pile placing method of the present invention; Fig.14 is a cross sectional view showing a procedure from the installation of a steel cage to the final step of the method; Fig.15 is a perspective view of a bag enclosure used in the method; Fig.16 is a perspective view showing steps of the installation of a steel cage in the method; Fig.17 is an enlarged cross sectional view showing steps of the installation of a steel cage in the method; Fig.18 is a perspective view of a bag structure of another embodiment of the method; and Fig.19 is a cross sectional view showing a conventional cast-in-place concrete pile placing method. BEST MODE FOR CARRYING OUT THE INVENTION Fig.1 is a perspective view of a cap structure A according to the present invention, Fig2 is a partially cut-off perspective view of the same; Fig.3 is a plan view of a bottom plate 6 of an outer cylinder 3 of the cap structure A, Fig.4 is a partially cut-off longitudinal cross sectional view of the cap structure A, Figs.5 and 6 are explanatory views showing the cap structure A in use, Fig.7 is an explanatory view showing removal of a remaining of slime containing concrete from an inner cylinder 2 of the cap structure A, Fig.8 is a partially cut-off perspective view of another embodiment of the cap structure A according to the present invention, Fig.9 is a partially cut-off perspective view of a further embodiment of the cap structure A, Fig.10 is a partially cut-off perspective view of a still further embodiment of the cap structure A, and Fig.11 is a partially cut-off perspective view showing a still further embodiment of the cap structure A in use. As shown in Figs.1 to 7, the outer cylinder 3 also has a top plate 1 mounted to the upper end thereof to define at center a round, upper tremie opening 4 into which a tremie pipe 16 is inserted to supply a flow of concrete for placement. The inner cylinder 2 which is slightly shorter in length than the outer cylinder 3 and opened at both, upper and lower, ends extends downwardly from the top plate 1 vertically of the upper tremie opening 4, thus forming a bottom-open double cylinder structure of the cap structure A. The top plate 1 of the outer cylinder 3 has a plurality of exhaust apertures 5 provided in an outward region thereof. The bottom plate 6 of the outer cylinder 3 has a lower tremie opening 7 provided in the center thereof similar in the size to the upper tremie opening 4. The bottom plate 6 has a series of reinforcement bar apertures 8 provided in an outward region thereof at substantially equal intervals for accepting pile reinforcement bars 11 of a steel cage 14. In addition, the bottom plate 6 has slits 9 provided therein at equal intervals of a distance between the reinforcement bar apertures 8 and extending radially from the lower tremie opening 7 to a flat region 6a of the bottom plate 6. Particularly, slit tabs 9a of the bottom plate 6 defined between the slits 9 are bent upwardly and welded at their distal end to the lowermost end of the inner cylinder 2, thus completing the structure of the cap structure A. As the result, a bottom space 10 of an inverted pan shape is created in the bottom of the cap structure A as defined by the slit tabs 9a of the bottom plate 6. This arrangement allows a mixture of air and slurry to escape smoothly through the slits 9 of the bottom plate 6 and the exhaust apertures 5 of the top plate 1 between the inner and outer cylinders 2, 3 during pouring of the concrete. Accordingly, as the pressure from below is remarkably reduced, the major problem of accumulating impurities of sediment including slime and laitance on the bottom plate will be minimized. The cap structure A is fitted onto the upper end of the steel cage 14 which is then installed in a drilled hole 17. The drilled hole 17 is filled with a batch of concrete which is supplied through the tremie pipe 16 and distributed continuously from the bottom of the drilled hole 17 to produce a steel-bar reinforced concrete pile. Through a series of experiments, we found that a remaining of concrete slime held substantially in the inner cylinder 2 can readily be removed immediately after the concrete placement by a modification of the common digging method, i.e. rotating a kelly bar 19 equipped with a digger bucket 18 or slime bucket. The cap structure A is then protected with an applicable lid and covered up with refilling soil by a known manner after removal of a casing 13. When the concrete has been cured, the cap structure A is uncovered by removing the refilling soil and separated from the steel cage 14 by means of a gas burner or a mechanical device such as a power shovel. According to the embodiment of the present invention, the chipping procedure is not used and its inducing technical problems are eliminated thus allowing the reinforcement bars 11 to remain intact and offering an economical advantage. As shown in Figs.1 to 3, the cap structure A includes the top plate 1 of an annular shape having at center the upper tremie opening 4, the inner cylinder 2 joined to the inner edge of the top plate 1, the outer cylinder 3 joined to the outer edge of the top plate 1, and the bottom plate 6 of an annular shape having at center the lower tremie opening 7. The bottom plate 6 is joined at its inner edge to the lowermost end of the inner cylinder 2 and at its outer edge to the lowermost end of the outer cylinder 3. Accordingly, the cap structure A has a double-cylinder construction. The inner cylinder 2 is arranged shorter by 2% to 3% than the outer cylinder 3. The difference may be determined by considering a diameter difference between the upper and lower tremie openings 4, 7. In addition, the distance between the two adjacent slits 9 may also be decided depending on the conditions of application. The size of the cap structure A may be determined by the dimensions of the steel cage 14 and the diameter and number of the reinforcement bars 11 which correspond to the size of the drilled hole 7 (See Fig.6). Preferably, a head extension 14a (a base of foundation of a building structure) of the steel cage 14 in the drilled hole 17 is equal to 40 or more times the diameter of the reinforcement bar 11. As the extension 14a represents the concrete extension of the prior art, it is based for determining the height of the cap structure A. The material of the cap structure A is preferably a soft steel sheet of 1.6 mm to 3.2 mm thick which has a favorable strength required for protection during the refilling and the re-digging and is easy to be handled for removal. It is understood that the material is not limited to the soft steel sheets but may be selected from synthetic resins or other metals. The cap structure A is fabricated in the following manner, As shown in Fig.2, the round top plate 1 and bottom plate 6 of the same diameter are shaped. The upper tremie opening 4 is provided in the center of the top plate 1 for accepting a common tremie pipe 16 (Fig.6) for supplying a flow of concrete. Also, a plurality of the exhaust apertures 5 are provided in the outward edge region of the top plate 1. The diameter and number of the exhaust apertures 5 may be determined depending on the size of the top plate 1. Preferably, the diameter is 10 mm to 20 mm and the number is 4 to 8. The bottom plate 6 has the flat regions 6a arranged at equal intervals of a distance (e.g. 90 mm) along the outward edge thereof and also has the equally spaced reinforcement bar apertures 8 therein so that each reinforcement aperture 8 is between the two adjacent flat regions 6a for accepting the reinforcement bar 11 of a steel cage 14, as best shown in Fig.3. The diameter of the reinforcement bar aperture 8 is as marginally large as about 1.3 to 1.5 times the diameter of the reinforcement bar 11. The lower tremie opening 7 is provided in the center of the bottom plate 6 and smaller by 2 % to 5 % in the diameter than the upper tremie opening 4. The slit tabs 9a of the bottom plate 6 which are defined by the radially extending slits 9 arranged at substantially equal intervals of the distance are bent to tilt at an angleh, namely 25 to 35 degrees, to the horizontal so that the diameter determined by the distal ends of the slit tabs 9a is substantially identical to that of the upper tremie opening 4. The distal ends of the slits tabs 9a of the bottom plate 6 are welded to the lowermost end of the inner cylinder 2, thus forming an inverted pan shape of space under the cap structure A communicated through the slits 9 as shown in Fig.4. As the cap structure A has a double-cylinder installation with the inverted pan shaped space at bottom, its slits 9 and the gap at each aperture 8 between the reinforcement bar 8 and the bottom plate 6 allow a mixture of air and slurry to run upward between the inner cylinder 2 and the outer cylinder 3 and escape through the exhaust apertures 5 of the top plate 1. More specifically, this arrangement is tended to attenuate the upward pressure created by the mixture of air and slurry swelling in the drilled hole 17. In addition, the inverted pan shaped space allows a sediment of slime to be rarely deposited on the bottom of the cap structure A. For assembly of the components of the cap structure A, the inner cylinder 2 is lowered through the upper tremie opening 4 of the top plate 1 and welded to the top plate 1. Then, the bottom plate 6 is joined to the lowermost end of the inner cylinder 2 thus defining the lower tremie opening 7. Finally, the outer cylinder 3 is welded to the top plate 1 and the bottom plate 6. In the embodiment, the welding is carried out by a stud welding method which may create as a more number of gaps as possible in the cap structure A and allow ease of disassembling. The cap structure A is fitted to the steel cage 14 so that the reinforcement bars 11 of the steep cage 14 extend through the reinforcement bar apertures 8 of the bottom plate 6 and come into direct contact with the lower side of the top plate 6 of the cap structure A (Fig.5). As a given number of traverse bars 15 have been stud welded to the vertical reinforcement bars 11 forming the steel cage 14, their uppermost is joined at some points by the same stud welding to the bottom plate 6 of the cap structure A. After the steel cage 14 is crowned with the cap structure A, it is installed in the drilled hole 17 as shown in Fig.6. As a secondary slime removal process has been executed if desired, the tremie pipe 16 is inserted through the inner cylinder 2 into the drilled hole 17 and starts pouring a batch of concrete at the bottom. The placement of concrete is finished when the batch of concrete reaches and exceeds the top plate 1 in the inner cylinder 2 of the cap structure A. After the placement of the concrete, the slime or digger bucket 18, depending on the condition of a site, mounted on the kelly bar 19 is introduced and rotated to remove a sediment of concrete slime from the inner cylinder 2 of the cap structure A. This is followed by removing the protective casing 13 from the drilled hole 17, locating a lid on the cap structure A, and covering them thoroughly with refilling soil for curing the concrete for a while. When the concrete has been cured, the refilling soil is removed again to expose the cap structure A. The removal of the cap structure A from the steel cage 14 comprises dismounting the top plate 1 and withdrawing the outer cylinder 3 and the inner cylinder 2 with the use of an applicable machine such as a power shovel. As the stud welding allows ease of the removal action, the bottom plate 6 is also ripped off by separating along some of the slits 9 with a gas burner. As the cap structure A is assembled by the stud welding method, its assembling time will be minimized and its removal will be eased. This provides the economical advantage. As the cap structure A has been removed, the extensions of the reinforcement bars 11 are exposed successfully. The procedure of concrete pile placement is hence completed after residual concrete slime and laitance are washed out using a jet of high pressured water. Fig.8 illustrates another embodiment of the cap structure A in which a top plate 1 is made of a perforated metal sheet having a multiplicity of apertures 5a therein for allowing a mixture of air and slurry to pass smoothly between an inner cylinder 2 and an outer cylinder 3. A bottom plate 6 similar to that of the previous embodiment has reinforcement bar apertures 8 and slits 9. The inner cylinder 2 may be arranged smaller in the length than or equal to the outer cylinder 3. When the inner cylinder 2 and the outer cylinder 3 are identical in the length to each other, the bottom plate 6 extends horizontally at the bottom between the inner cylinder 2 and the outer cylinder 3. The use of the cap structure A of this embodiment is identical to the previous one and will be explained in no more details. The top plate 1 is not limited to the perforated metal sheet but may be a mesh sheet or a like material which can pass the mixture of air and slurry while having a predetermined mechanical strength and satisfying safety and cost requirements. Fig.9 shows a further embodiment of the cap structure A in which a top plate 1 has a plurality of slits 9a therein for allowing a mixture of air and slurry to pass smoothly between an inner cylinder 2 and an outer cylinder 3. Other components and their arrangement are identical to those of the previous embodiment and will be no more explained. Fig.10 illustrates a still further embodiment of the cap structure A in which a top plate 1 has a plurality of exhaust apertures 5 therein and a bottom plate 6 has a more number of apertures 5c therein which serve as the reinforcement apertures 8 and the slits 9. Other components and their arrangement are identical to those of the previous embodiment and will be no more explained. In each of the above embodiments, the inner cylinder 2 may be arranged equal in the length to or shorter than the outer cylinder 3. While the reinforcement bar apertures 8 in the bottom plate 6 are obligatory, the other apertures and slits in the top plate 1 and the bottom plate 5 are illustrative and may be modified in shape, size, and number depending on the condition of a site. Fig.11 shows a still further embodiment of the cap structure A in which retaining members 20 are mounted to a lower region of the side surface of the outer cylinder 3. In this embodiment, the retaining members 20 are bolts 20a screwed into threaded apertures in the outer cylinder 3. Each of the bolts 20a is fastened to one end of a tie material 21 such as a steel wire or string. When the cap structure A is fitted on the steel cage 14, the other ends of the tie materials 21 are tightened to one of the traverse reinforcement bars 15 to secure the cap structure A. This allows the cap structure A to stay in its position while being retained by the tie material 21 even if it is exerted by an upward stress due to the escape of the mixture of air and slurry, a majority of which is relieved by the function of the apertures and slits, during the placement of concrete. Fig.12 is a view showing a further embodiment in which the retaining members 20 are replaced with a set of chains 23, e.g. a pair 23a and 23b, for fastening the cap structure A to the steel cage 14. The change 23a is looped with its end hooks 24a and 24b tightened to each other so that it extends downwardly along the side surface of the outer cylinder 3 to one of the traverse reinforcement bars 15 of the steel cage 14 and upwardly therefrom along the side surface of the inner cylinder 2. The other chain 23b is also looped in the same manner at the opposite location to the chain 23a. The chains 23 may be substituted with cables, heavy wires, and other materials which are rigid enough to fasten the cap structure A to the reinforcement bar 15 of the steel cage 14. Accordingly, the cap structure A is held in its position while being tightened to the steel cage 14 by the chains 23a and 23b even when it is exerted by an upward stress due to the escape of the mixture of air and slurry during the placement of concrete, although a majority of the stress is relieved by the prescribed function of the apertures and slits. The cap structure A of this embodiment is easily released from the protective casing 13 after the placement of concrete as compared with the preceding one of which bolts 20a (Fig.11) may obstruct the removal from the casing 13. A further embodiment of the present invention will now be described in the form of a method of cast-in-place concrete pile placement. The method of the present invention comprises installing a steel cage 2A in a drilled hole 1A as holding it with an enclosure 3A, and filling the enclosure 3A with a batch of concrete 4A to form a concrete pile. As shown in Fig.16, the steel cage 2A is made of an assembly of vertical reinforcement bars 21A and hoop ties 22A and can be installed in the drilled hole 1A using a crane or hoist. The steel cage 2A is sized to have a clearance from the inner wall of the drilled hole 1A where spacers 23A are disposed for developing an overcoating. The enclosure 3A is made of a sheet tube having an open top and a closed bottom, as best shown in Fig.15(A). A tube 31A of the enclosure 3A has a deep slit 32A therein extending vertically close to the closed bottom 33A so that it can be opened along the slit 32A. The slit 32A is closed with a fastener 34A which comprises a row of teeth 35A and a slider 36A. The slider 36A is provided with a grip 36a of a hook shape. The enclosure 3A is made of a heavy-duty sheet of a fabric or rubber material reinforced with a nylon or synthetic resin meshing (not shown). The inner diameter of the tube 31A of the enclosure 3A is larger than the diameter r of the steel cage 2A between the opposite spacers 23A, as shown in Fig.16(C). The outer diameter of the tube 31A is then smaller than the diameter R of the drilled hole 1A. The procedure of carrying out the method with the enclosure 3A will be explained. (1) Drilling of hole The procedure starts with locating and drilling a pilot hole by means of a digger or auger bucket 5A, as shown in Figs.13(A) and 13(B). A protective casing 6A is fitted in the pilot hole as shown in Fig.13(C) and the action of the auger bucket 5A is continued until it moves in the support base ground B as shown in Fig.13(D). (2) Setting of enclosure 3A After the drilled hole is completed, the enclosure 3A in its rolled form 31a is placed with its bottom 33A seated across the opening of the drilled hole 1A, as shown in Figs.15(A) and 16(A). At the time, the tube 31A of the enclosure 3A is rolled and remains open with the slider 36A located at the lowermost of the fastener 34A. The grip 36a of the slider 36A of the fastener 34A is then hooked to the protective casing 6A in the drilled hole 1A. (3) Installation of steel cage 2A The steel cage 2A is lowered into the drilled hole 1A as shown in Fig.14(A). More particularly, the steel cage 2A is slung by a crane (not shown) and lifted down into the drilled hole 1A, as best shown in Figs.14(B) and 16(A). As the steel cage 2A is lifted down, its lower end presses and drives the bottom 33A of the enclosure 3A to the bottom of the drilled hole 1A, as shown in Fig.16(B). Simultaneously, the tube 31A of the enclosure 3A in the rolled form 31a is rolled off and stretched throughout the drilled hole 1A. The releasing of the rolled form 31a may be assisted manually by a worker. While its slider 36A is hooked up, the fastener 34A is being closed with the steel cage 2A being lowered and thus, the slit 32A of the tube 31A of the enclosure 3A is shut up. Meanwhile, a water inflow W moves into the enclosure 3A through its slit 32A. When the steel cage 2A has been installed, the enclosure 3A is filled with the water inflow W as shown in Fig.14(C). (4) Placement of concrete A batch of concrete 4A is poured into the drilled hole 1A from a tremie pipe 7A, as shown in Fig.2(D). The tremie pipe 7A is lifted up as the level of the concrete 4A rises, as shown in Figs.14(E) and 14(F). During the concrete placement, the enclosure 3A acts as a concrete form to retain the concrete 4A and separate the steel cage 4A from the inner wall and bottom of the drilled hole 1A. Accordingly, sediments of slime on the bottom of the drilled hole 1A will be prevented from mixing with the concrete 4A of which quality thus remains not degraded. No slime or laitance appears in the top skim of the concrete 4A and an extra of concrete is not needed. In other words, the chipping process is never implemented when the concrete 4A has been solidified. The protective casing 6A is removed after the placement of the concrete 4A is completed, as shown in Fig.14(F). The tube 31A of the enclosure 3A may be joined with another tube structure 3B if two or more of the steel cages 2A are used as shown in Fig.15(B). The tube structure 3B is made of the same material as of the enclosure 3A and has a vertically extending slit therein from top to bottom for opening. A fastener 34B is mounted along the slit for closing the tube 3B. As the two steel cages 2A have been joined to each other, the tube 3B is also joined by a fastener 34C to the tube 31A of the enclosure 3A so that the two tubes can be stretched throughout the drilled hole 1A. The fastener 34C has a pair of teeth 35C, one mounted to the uppermost of the tube 31A of the enclosure 3A and the other mounted to the lowermost of the tube structure 3B. Also, shown are a slider 36B of the fastener 34B and a slider 36C of the slider 34C. The joining of the tube 3A to the other 3B is not limited to the fastener 34C but may be implemented using a fast-bonding or instant adhesive. As shown in Fig.15(B), the tube 3B may be joined to another 3B by the fastener 34C or adhesive. For placement of a counter-tapered concrete pile, the enclosure 3A may be used of a corresponding shape shown in Fig.18. In that case, the bottom of the enclosure 3A is folded as located across the opening of a drilled hole 1A. CAPABILITY OF EXPLOITATION IN INDUSTRY The present invention is used as for a pile head dresser which is mounted to the head of a steel cage of a cast-in-place concrete pile installed in the ground for making a foundation of civil engineering work, as for a method of dressing the head of such a concrete pile. DESCRIPTION OF THE REFERENCE NUMBERS A CAP STRUCTURE 1 TOP PLATE 2 INNER CYLINDER 3 OUTER CYLINDER 4 UPPER TREMIE OPENING 5 EXAUST APERTURES 6 BOTTOM PLATE 6a FLAT REGION 7 UPPER TREMIE OPENING 8 REINFORCEMENT BAR APERTURES 9 SLIT 9a SLIT TABS 10 BOTTOM SPACE 11 REINFORCEMENT BARS 12 PAN END 13 CASING 14 STEEL CAGE 15 TRAVERSE BARS 16 TREMIE PIPE 17 DRILLED HOLE 18 BUCKET 19 KELLY BAR 23 WIRE 23a CHAIN 23b CHAIN 1A DRILLED HOLE 2A STEEL CAGE 3A ENCLOSURE 31A TUBE 32A SLIT 33A BOTTOM 34A FASTENER

Claims: A pile head dresser for cast-in-place concrete piles comprising an inner cylinder(2)arranged for allowing a tremie pipe (16) to move in and out, and surrounded at a distance by an outer cylinder(3), and a top plate (1) and a bottom plate (6) joining the two cylinders (2, 3) at top and bottom respectively to form a double cylinder structure (A), the bottom plate(6)having a plurality of reinforcement bar apertures (8) provided therein at equal intervals of a distance, characterized by the top and bottom plates 1, 6 having exhaust apertures (5, 9) respectively provided therein for passing a mixture of air and slurry. A pile head dresser for cast-in-place concrete piles of claim 1, characterized in that while the inner cylinder (2) and the outer cylinder (3) are equal in the length to each other, the top and bottom plates (1, 6) extend horizontally between the two cylinders (2, 3). A pile head dresser for cast-in-place concrete piles characterized by a cap structure (A) of a double cylinder construction which comprises a top plate (1) of an outer cylinder (3) having a plurality of exhaust apertures (5) provided in an outward edge region thereof for passing a mixture of air and slurry and also an upper tremie opening (4) provided in a center thereof for allowing a tremie pipe (16) to move in and out for supplying a batch of concrete for placement, and an inner cylinder (2) having both ends thereof opened and arranged shorter 2% to 3% than the outer cylinder (3), wherein the outer cylinder (3) is coupled to a bottom plate (6) which has a plurality of reinforcement bar apertures (8) provided in an outward edge or flat region (6a) thereof at equal intervals of a distance and a plurality of slits (9) provided at equal intervals of a distance and extending radially from a lower tremie opening (7) formed in a center of the bottom plate (6) to the flat region (6a) thus to define a group of slit tabs (9a), and the slit tabs (9a) are folded upward to tilt and their distal ends are welded to the lowermost ends of the inner cylinder (2). A pile head dressers for cast-in-place concrete piles of claims 1, 2, and 3, characterized in that the top plate (1) and/or bottom plate (6) is made of a mesh or perforated metal sheet. A pile head dressing methods using a pile head dressers for cast-in-place concrete piles of claim 1, 2, 3, or 4, characterized in that the cap structure (A) is mounted on and fixedly tied to the steel cage (14) by at least a pair of detachable chains, wires, or cables before both are installed in the drilled hole (17). A pile head dressing methods using a pile head dressers for cast-in-place concrete piles of claim 1, 2, 3, or 4, characterized in comprising joining the cap structure (A) to a steel cage (14) by stud welding, installing both in a drilled hole (17), inserting the tremie pipe (16) through the inner cylinder (2) of the cap structure (A) into the drilled hole (17), pouring a batch of concrete continuously into the same until the level of the concrete rises from the bottom of the drilled hole (17) to the top of the inner cylinder (2), and removing sediments of concrete slime from the inner cylinder (2) without delay by a rotating action of a digger bucket (18) mounted to a kelley bar (19).

Inventors: OKAWA SHOGEN, OKAWA, SHOGEN
Applicants: OKAWA SHOGEN, OKAWA, SHOGEN
Application year: 1995
Main classification: E02D5
IPC codes: E02D5