A method for constructing cast-in-place piles, a temporary load support device used in the said construction method, and an excavator for cast-in-place piles.

Abstract

To provide a method for constructing cast-in-place piles that can improve safety during construction. [Solution] A method for constructing cast-in-place piles, which includes an installation step of installing reinforcing cages into a pile hole 4 while connecting them, wherein the installation step includes a connecting step of connecting an upper reinforcing cage 30A suspended by a crane and a lower reinforcing cage 30B that has been previously suspended into the pile hole 4 and is suspended in the pile hole 4 with a predetermined amount protruding from the pile hole 4, and the connecting step includes a step of connecting the lower part of the upper reinforcing cage 30A and the upper part of the lower reinforcing cage 30B with a connector, while the upper reinforcing cage 30A is temporarily supported by a temporary load support device 10 that temporarily supports a load suspended by a crane.

Description

Technical Field

[0001] The present invention relates to a method for constructing a driven pile, a temporary load receiving device used in the construction method, and an excavator for driven piles, and particularly relates to a method for constructing a driven pile capable of enhancing work safety during construction, a temporary load receiving device used in the construction method, and an excavator for driven piles.

Background Art

[0002] At a construction site of a structure, in order to enhance the seismic strength of the structure, etc., a construction method of driving piles into the ground to form a pile foundation for supporting the structure is generally adopted. One of the construction methods of the pile foundation is a construction method using driven piles. A driven pile is, for example, formed by building a reinforcing cage assembled in a cylindrical shape into an excavated pile hole, and after building it in, placing fresh concrete into the pile hole and solidifying it. Depending on differences such as a method of excavating the ground, several construction methods such as an all-casing method, an earth drill method, and a reverse method are known for the construction method using driven piles.

[0003] The general construction process of a driven pile by the all-casing method is as follows (for example, refer to Patent Document 1 below). (1) Install an excavator. (2) Repeatedly perform the pressing-in of a casing (also referred to as a casing tube) by the excavator, the excavation inside the casing using a hammer grab, etc., and the connection of the casing until a predetermined depth (support layer) is excavated to form a pile hole. (3) Build a reinforcing cage into the pile hole while connecting it. (4) Build a tremie pipe into the pile hole and place fresh concrete. (5) Perform backfilling work.

[0004] The construction process of a driven pile as described above includes a process of performing work while suspending the lifting of a casing, a reinforcing cage, etc. using a crane. For example, in the construction process where reinforcing cages are installed in pile holes while being connected, the lower reinforcing cage is lifted into the pile hole by a crane, and the upper part of the lower reinforcing cage is temporarily supported in the casing opening using a jig for lifting the reinforcing bars, with the upper part of the lower reinforcing cage protruding from the pile hole (the opening of the casing). Next, the upper reinforcing cage is lifted by a crane and moved directly above the lower reinforcing cage, and the upper reinforcing cage lifted by the crane and the lower reinforcing cage temporarily supported in the pile hole are connected, and the connected reinforcing cages are lifted into the pile hole. This process is repeated.

[0005] Regarding the above construction process, Patent Document 1 below describes an example of work in which a worker connects the main reinforcement bars of the lower reinforcing cage and the upper reinforcing cage using a mechanical joint. Furthermore, Patent Document 2 below describes an example of work in which a worker connects the main reinforcement bars of the lower reinforcing cage and the upper reinforcing cage using metal fittings such as U-bolts.

[0006] Furthermore, in the process of pouring ready-mix concrete after the construction process described above, it is common practice to place the reinforcing cage in a self-supporting position in the pile hole, and then repeatedly remove a portion of the casing by pulling it out of the pile hole and detaching it in accordance with the amount of ready-mix concrete being poured, and then lowering the detached casing to a temporary storage area using a crane.

[0007] However, in recent years, the reinforcement cages used to construct cast-in-place piles have undergone significant changes in their reinforcement, particularly in the diameter and number of reinforcements at the pile head, which is subjected to horizontal forces during earthquakes, in order to withstand massive earthquakes. The excessive load at the pile head is now supported by the same main reinforcement at the base as before, i.e., a reinforcement cage consisting of smaller diameter and fewer main reinforcements compared to the reinforcement cage at the pile head. Thus, recent reinforcement cages have changed significantly from previous reinforcement cages in terms of their reinforcement, the structure of the pile itself, and the length of the pile.

[0008] Therefore, in the concrete pouring process described above, if the reinforcing cage is left to stand on its own in the pile hole, as was done in the past, there is a risk of buckling occurring in the reinforcing cage due to the weight of the reinforcing bars and the settlement of the concrete. Measures to prevent such buckling are therefore necessary. As one such measure, in the concrete pouring process described above, instead of leaving the reinforcing cage to stand on its own in the pile hole, the concrete is poured while the cage is suspended by a crane or similar device.

[0009] [Problems the invention aims to solve] In the process of erecting the above-mentioned reinforcing cages while connecting them, the upper reinforcing cage is suspended by a crane, meaning it is in an unstable state where it is prone to swaying. Furthermore, workers must connect the upper and lower reinforcing cages using mechanical joints or metal fittings directly beneath the suspended upper reinforcing cage, which presents a challenge in ensuring sufficient worker safety.

[0010] Furthermore, in the process of pouring the ready-mix concrete, for example, when pouring the concrete while the reinforcing cage is suspended using the main hook of the crane, the detached casing cannot be removed while the reinforcing cage is still suspended by the main hook. Therefore, when performing the casing removal work described above, it was necessary to re-suspend the reinforcing cage in order to temporarily free the main hook.

[0011] In other words, after pulling out and separating one casing to be removed, the separated casing was lifted using the crane's auxiliary hook, and the reinforcing cage, which was suspended by the main hook directly below the lifted casing, was then re-suspended using a jig for reinforcing bars at the opening of the casing located on the excavator's work platform, thus temporarily freeing the main hook. Therefore, even in the process of pouring the concrete, the reinforcing cage replacement work was carried out directly below the casing that had been lifted using the aforementioned sub-hooks, that is, directly below the suspended load, which presented a problem in that the safety of the work was not adequately ensured. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2022-242178 [Patent Document 2] Japanese Patent Publication No. 2014-173418 [Overview of the project] Means for solving the problem and their effects

[0013] The present invention has been made in view of the above problems, and aims to provide a method for constructing cast-in-place piles that can improve safety during construction, a temporary load support device used in the construction method, and an excavator for cast-in-place piles.

[0014] To achieve the above objective, the construction method (1) for cast-in-place piles according to the present invention is: A method for constructing cast-in-place piles, which includes an installation process in which reinforcing cages are connected and then erected into the pile holes, The aforementioned construction process, The process includes a connecting step of connecting an upper reinforcing cage suspended by a crane with a lower reinforcing cage that has been previously suspended in the pile hole and is suspended in the pile hole with a predetermined amount protruding from the pile hole, The coupling process is, The present invention is characterized by including a step of connecting the lower part of the upper reinforcing cage and the upper part of the lower reinforcing cage with a connector, while the upper reinforcing cage is temporarily supported by a temporary load support device that temporarily supports the load suspended by the crane.

[0015] According to the above-described method for constructing cast-in-place piles (1), in the connection step, with the upper reinforcing cage temporarily supported by the temporary load support device, it becomes possible to connect the lower part of the upper reinforcing cage and the upper part of the lower reinforcing cage with the connector. In other words, since the upper reinforcing cage suspended by the crane is temporarily supported in a stable state by the temporary load support device, it is possible to prevent accidents such as the upper reinforcing cage swinging or falling during the connection process. Therefore, it becomes possible to carry out the construction while ensuring the safety of the workers performing the connection work of the reinforcing cage, thereby improving work safety during construction.

[0016] Furthermore, the method for constructing cast-in-place piles according to the present invention (2) is the same as the method for constructing cast-in-place piles (1) described above, The aforementioned reinforcing cage is composed of a plurality of main reinforcing bars, a plurality of hoop reinforcing bars arranged intersecting these main reinforcing bars, and a plurality of reinforcing rings arranged intersecting the plurality of main reinforcing bars. In the aforementioned coupling process, The upper reinforcing cage is temporarily supported by receiving the lowest reinforcing ring constituting the upper reinforcing cage with the temporary support portion of the temporary load support device.

[0017] According to the above-described construction method (2) for cast-in-place piles, the upper reinforcing cage is temporarily supported by receiving the lowermost reinforcing ring with the temporary support portion of the temporary load support device. Therefore, the temporary load support device does not interfere with the work of connecting the lower part of the upper reinforcing cage and the upper part of the lower reinforcing cage, allowing the connection process to be carried out smoothly and improving work efficiency during construction.

[0018] Furthermore, the method for constructing cast-in-place piles according to the present invention (3) is characterized in that, in the method for constructing cast-in-place piles (2) above, the temporary support portion is positioned below the lowest reinforcing ring so as to support the lowest reinforcing ring at at least four locations.

[0019] According to the above-described construction method (3) for cast-in-place piles, the temporary support section is positioned below the lowest reinforcing ring so as to support the lowest reinforcing ring at at least four locations, thereby allowing the upper reinforcing cage to be temporarily supported in a more stable state.

[0020] Moreover, the method for constructing a cast-in-place pile according to the present invention (4) is any one of the methods for constructing a cast-in-place pile (1) to (3) above, after the connection step of connecting the upper reinforcing cage and the lower reinforcing cage in the connection step, the method includes a step of releasing the temporary support state of the upper reinforcing cage by the suspension load temporary support device, and then suspending the upper reinforcing cage and the lower reinforcing cage suspended by the crane into the pile hole.

[0021] According to the method for constructing a cast-in-place pile (4) above, after connecting the upper reinforcing cage and the lower reinforcing cage, the method includes releasing the temporary support state of the upper reinforcing cage by the suspension load temporary support device, and then suspending the upper reinforcing cage and the lower reinforcing cage suspended by the crane into the pile hole. Therefore, it is possible to more safely suspend the connected reinforcing cage into the pile hole.

[0022] Moreover, the method for constructing a cast-in-place pile according to the present invention (5) is any one of the methods for constructing a cast-in-place pile (1) to (4) above, the pile hole is formed by pressing a casing into the ground and excavating the inside of the casing while adding extensions, after the placement step, the method includes a placing step of placing fresh concrete into the pile hole with the reinforcing cage suspended in the pile hole, the placing step includes after placing the fresh concrete to a predetermined height, repeating a casing removal step of pulling out and separating one casing with the reinforcing cage suspended by the crane and then removing it, the casing removal step includes a step of suspending and supporting the separated casing by the crane, a temporary support step of temporarily supporting the casing suspended and supported by the crane with the suspension load temporary support device, after the temporary support step, the method includes a first suspension replacement step of suspending and replacing the reinforcing cage suspended by the crane with the upper opening of the casing embedded in the ground.

[0023] According to the above-described method for constructing cast-in-place piles (5), in the casing removal step of the driving step, the steps of lifting and supporting the detached casing with the crane, temporarily supporting the casing lifted and supported by the crane with the temporary load support device, and a first suspension step after the temporary support step, in which the reinforcing cage lifted by the crane is suspended and then re-suspended to the upper opening of the casing embedded in the ground. Therefore, the first suspension replacement process, that is, the suspension replacement work of the reinforcing cage, can be performed after the casing, which has been suspended and supported by the crane, has been temporarily supported by the temporary load support device. Therefore, it is possible to prevent accidents such as the casing being suspended and supported by the crane falling, ensuring the safety of the workers performing the replacement of the reinforcing cage, and thereby improving safety during construction. Furthermore, the reinforcing cage may be suspended by, for example, the first hoisting means of the crane, and the detached casing may be suspended by the second hoisting means of the crane.

[0024] Furthermore, the method for constructing cast-in-place piles according to the present invention (6) is as described in the above method for constructing cast-in-place piles (5), The aforementioned concrete casting process, The process includes installing a tremie pipe in the pile hole, suspending the tremie pipe from the upper opening of the casing embedded in the ground, and then pouring the ready-mix concrete into the tremie pipe. The casing removal process described above is After pouring the ready-mix concrete to a predetermined height, the tremie pipe is suspended and supported by the crane. The method further includes a second suspension step, in which, after the temporary support step, the tremie pipe, which is suspended and supported by the crane, is suspended to the upper opening of the casing embedded in the ground.

[0025] According to the above-described method for constructing cast-in-place piles (6), the second suspension step, i.e., the suspension of the tremie pipe, can be performed after the casing, which has been suspended and supported by the crane, has been temporarily supported by the temporary load support device. Therefore, it is possible to prevent accidents such as the casing being suspended and supported by the crane falling, ensuring the safety of the workers performing the tremie pipe replacement work, and thereby improving safety during construction. The tremie pipe may be suspended, for example, by the third hoisting means of the crane, or by the first hoisting means.

[0026] Furthermore, the method for constructing cast-in-place piles according to the present invention (7) is performed in the above-mentioned method for constructing cast-in-place piles (5) or (6), The aforementioned concrete casting process, After the casing removal step, a return step is performed to return the temporary load support device to its predetermined position. The invention is characterized by including a third suspension step of changing the suspension of the reinforcing cage to a state in which it is suspended by the crane.

[0027] According to the above-described method for constructing cast-in-place piles (7), the driving step includes the returning step and the third lifting step after the casing removal step. Therefore, in the third lifting step, the temporary load support device does not interfere with the lifting work of the reinforcing cage, allowing the next concrete pouring work and the subsequent casing removal step to be carried out smoothly, thereby improving work efficiency during construction.

[0028] Furthermore, the method for constructing cast-in-place piles according to the present invention (8) is as described in the above method for constructing cast-in-place piles (6), The aforementioned concrete casting process, The method is characterized by including a tremie pipe removal step, either before or after the casing removal step, in which the tremie pipe, which is suspended from the upper opening of the casing buried in the ground, is suspended by the crane, the tremie pipe is lifted up, a portion of it is cut off, and then it is removed.

[0029] According to the above-described method for constructing cast-in-place piles (8), the tremie pipe removal process is performed either before or after the casing removal process. Therefore, in the tremie pipe removal process, the temporary load support device does not interfere with the tremie pipe removal work, and the work of lifting the tremie pipe, detaching a portion of it, and then removing it can be carried out safely and smoothly.

[0030] Furthermore, the temporary load support device (1) according to the present invention is a temporary load support device used in any of the above-mentioned construction methods (1) to (4) for cast-in-place piles, A temporary support section for temporarily supporting the upper reinforcing cage suspended by the crane above the pile hole, It is characterized by having a support mechanism that supports the temporary support portion.

[0031] According to the above-described temporary load support device (1), the temporary support portion allows the upper reinforcing cage suspended by the crane to be temporarily supported above the pile hole, thereby ensuring safety during the connection process of the reinforcing cage. Furthermore, it is possible to provide a device that can enhance work safety with a small number of components, such as the temporary support portion and the support mechanism.

[0032] Furthermore, the temporary load support device (2) according to the present invention is provided in the temporary load support device (1) described above, The support mechanism is configured to include a moving mechanism for moving the temporary support portion in a predetermined direction, and a base to which the moving mechanism is attached. The temporary support section is composed of one or more gantry-type frames and temporary support jigs arranged on the gantry-type frames. The spacing between the legs of the aforementioned gate-type frame is greater than the diameter of the pile hole. The aforementioned moving mechanism is characterized in that it includes a guide that movably supports the legs of the gantry-type frame.

[0033] According to the above-described temporary load support device (2), the connection work of the reinforcing cage can be performed while the upper reinforcing cage is temporarily supported by the temporary support jig installed on the gate-type frame, that is, while securing working space. Furthermore, since the temporary support can be moved in a predetermined direction by the moving mechanism, the temporary support can be moved out of the way of the pile hole during processes that do not utilize it, so that the temporary support does not interfere with construction work. In other words, during processes other than the connecting process, the gantry frame can be moved out of the way of the pile hole, so that the gantry frame does not interfere with construction work.

[0034] Furthermore, the temporary load support device (3) according to the present invention is, in the temporary load support device (2) described above, The aforementioned temporary support jig A locking part that engages with the reinforcing ring of the upper reinforcing cage, The device is characterized by comprising a housing that allows the locking portion to be retracted and retracted.

[0035] According to the above-described temporary load support device (3), since the temporary support jig is equipped with a locking part that can be moved in and out of the storage part, the temporary support work of the upper reinforcing cage can be efficiently performed by moving the locking part in and out.

[0036] Furthermore, the temporary load support device (4) according to the present invention is configured in the temporary load support device (2) or (3) described above. The aforementioned gantry-type frame is characterized by having legs that are extendable and retractable.

[0037] According to the above-described temporary load support device (4), since the legs of the gantry frame are configured to be extendable and retractable, the height position for temporarily supporting the upper reinforcing cage can be adjusted according to the specifications of the reinforcing cage, thereby ensuring an appropriate working space.

[0038] Furthermore, the temporary load support device (5) according to the present invention is characterized in that, in any of the temporary load support devices (1) to (4) described above, the temporary support portion is equipped with a guard to prevent the collapse of the upper reinforcing cage that is temporarily supported.

[0039] According to the above-described temporary load support device (5), since the guard is provided on the temporary support portion, it is possible to prevent the collapse of the temporarily supported upper reinforcing cage, thereby further enhancing work safety.

[0040] Furthermore, the temporary load support device (6) according to the present invention is a temporary load support device used in any of the above-mentioned construction methods (5) to (8) for cast-in-place piles, A temporary support section for temporarily supporting the upper reinforcing cage suspended by the crane and the detached casing above the excavator for cast-in-place piles, It is characterized by having a support mechanism that supports the temporary support portion.

[0041] According to the above-described temporary load support device (6), the temporary support section allows the upper reinforcing cage suspended by the crane to be temporarily supported above the excavator, thereby ensuring safety during the connection process of the reinforcing cage. Furthermore, the temporary support section allows the detached and lifted casing to be temporarily supported above the excavator, thereby ensuring safety during the casing removal process. Furthermore, it is possible to provide a device that can enhance work safety with a small number of components, such as the temporary support portion and the support mechanism.

[0042] Furthermore, the temporary load support device (7) according to the present invention is, in the temporary load support device (6) described above, The support mechanism is configured to include a moving mechanism for moving the temporary support portion in a predetermined direction, and a base to which the moving mechanism is attached. The base or the moving mechanism is configured to be attachable to the excavator.

[0043] According to the above-described temporary load support device (7), the temporary support portion can be moved in a predetermined direction by the moving mechanism, so that the temporary support portion can be retracted so as not to obstruct construction work in processes other than the connection process and the casing removal process that do not utilize the temporary support portion. Furthermore, since the base portion or the moving mechanism can be attached to the excavator, a compact configuration can be achieved. In addition, it can be configured to be integrated with the excavator, and installation can be performed in an integrated state with the excavator, thus preventing the installation work from becoming complicated.

[0044] Furthermore, the temporary load support device (8) according to the present invention is, in the temporary load support device (7) described above, The temporary support section is composed of one or more gantry-type frames and temporary support jigs arranged on the gantry-type frames. The distance between the legs of the gantry frame is greater than the diameter of the casing. The aforementioned moving mechanism is configured to include a guide that movably supports the legs of the gantry frame, The guide portion is characterized by being longer than the diameter of the casing.

[0045] According to the above-described temporary load support device (8), the connection work of the reinforcing cage can be performed with the upper reinforcing cage placed on the temporary support jig installed on the gate-type frame, that is, while securing working space. Furthermore, the detached casing can be placed on the gantry frame or the temporary support jig, that is, while ensuring sufficient working space, to perform the reinforcing cage and tremie pipe replacement work (the first replacement step and the second replacement step). Furthermore, since the moving mechanism includes the guide portion, and the guide portion is longer than the diameter of the casing, it is possible to move the gantry frame to the outside of the pile hole during processes other than the connection process and the casing removal process, so that the gantry frame does not get in the way of construction work.

[0046] Furthermore, the temporary load support device (9) according to the present invention is, in the temporary load support device (8) described above, The aforementioned temporary support jig A locking portion that can be locked to at least the reinforcing ring of the upper reinforcing cage, The device is characterized by comprising a housing that allows the locking portion to be retracted and retracted.

[0047] According to the above-described temporary load support device (9), since the temporary support jig is equipped with a locking part that can be moved in and out of the housing, the temporary support work of at least the upper reinforcing cage can be efficiently performed by moving the locking part in and out. In addition, the detached casing may be temporarily supported with the locking part when it is extended out of the housing, and this method of use makes it possible to efficiently perform the temporary support work of the detached casing as well.

[0048] Furthermore, the excavator for cast-in-place piles according to the present invention is characterized by being equipped with any of the above-mentioned temporary load support devices (6) to (9). The above-mentioned excavator for cast-in-place piles can be made to function as an excavator that achieves the effects of the above-mentioned temporary load support devices (6) to (9), thereby improving work safety during the construction of cast-in-place piles. [Brief explanation of the drawing]

[0049] [Figure 1] This figure illustrates the construction method of a cast-in-place pile according to Embodiment (1), where (a) is a side view showing the state before the upper reinforcing cage is temporarily supported by the temporary load support device, and (b) is a side view showing the state after the upper reinforcing cage has been temporarily supported by the temporary load support device. [Figure 2] This figure shows the main components of a temporary load support device used in the construction method of cast-in-place piles according to Embodiment (1), where (a) is a plan view and (b) is a front view. [Figure 3] This figure shows the main components of an excavator equipped with a temporary load support device used in the construction method of cast-in-place piles according to Embodiment (2), where (a) is a plan view and (b) is a side view. [Figure 4]This diagram illustrates the construction method for cast-in-place piles according to Embodiment (2), where (a) shows the state after the first concrete has been poured to a predetermined height, and (b) shows the state after one casing has been removed. [Figure 5] This diagram illustrates the construction method of cast-in-place piles according to embodiment (2), where (a) shows the detached casing temporarily supported by a temporary load support device, and (b) shows the state after the reinforcing cage has been replaced. [Figure 6] This diagram illustrates the construction method for cast-in-place piles according to embodiment (2), where (a) shows the state in which the detached casing is being removed, and (b) shows the state in which a part of the tremie pipe is being detached and removed. [Figure 7] This diagram illustrates the construction method for cast-in-place piles according to Embodiment (2), and shows the state after the second concrete pit has been poured to a predetermined height. [Modes for carrying out the invention]

[0050] The following describes, with reference to the drawings, a method for constructing cast-in-place piles according to the present invention, a temporary load support device used in the construction method, and an excavator for cast-in-place piles. The embodiments described below are preferred examples of the present invention and therefore have various technically preferable limitations. However, the scope of the present invention is not limited to these forms unless otherwise specified in the following description.

[0051] Figure 1 is a diagram illustrating the construction method of a cast-in-place pile according to Embodiment (1), and in particular, it illustrates the connection process included in the reinforcement cage erection process. In this embodiment, the case in which the earth drill method is applied to the construction method of the cast-in-place pile will be described.

[0052] Figure 1(a) shows the state before the upper reinforcing cage 30A is temporarily supported by the temporary load support device 10 during the connection process, and (b) shows the state after the upper reinforcing cage 30A has been temporarily supported by the temporary load support device 10 during the connection process. Figure 2 shows the main components of the temporary load support device 10 used in the construction method of cast-in-place piles according to embodiment (1), where (a) is a plan view and (b) is a front view.

[0053] Before describing the construction method for cast-in-place piles according to Embodiment (1), the configuration of the temporary load support device 10 used in the construction method for cast-in-place piles will be described based on Figure 2. The temporary load support device 10 comprises a temporary support section 11 for temporarily supporting the upper reinforcing cage 30A, which is suspended by a crane (not shown), above the pile hole 4 during the reinforcing cage connection process; a moving mechanism 13 for moving the temporary support section 11 in a predetermined direction, in this case, horizontally; and a base 15 to which the moving mechanism 13 is attached. The device is arranged on the ground so as to surround the pile hole 4. The support mechanism 21, which supports the temporary support section 11, includes the moving mechanism 13 and the base 15.

[0054] The temporary support section 11 consists of a pair of gantry frames 12 and temporary support jigs 18 installed on each gantry frame 12. Each gantry frame 12 has a base portion 12a and legs 12b attached to both ends of the base portion 12a. Two temporary support jigs 18 are attached to the base portion 12a of each gantry frame 12, so that a total of four temporary support jigs 18 are installed in a manner that allows them to be positioned opposite each other on diagonal lines that divide the pile hole 4 into four equal parts. The shape of the base portion 12a is not limited to the rectangular shape shown in Figure 2, and may have a shape in which the side facing the pile hole 4 is cut out in an arc shape. The spacing between the legs 12b of the gantry frame 12 is approximately twice the diameter of the pile holes 4, and the frame straddles the pile holes 4. Furthermore, the legs 12b of the gantry frame 12 are equipped with a lifting mechanism (not shown), such as a hydraulic jack, allowing them to extend and retract vertically. The height of the gantry frame 12 can be adjusted to a height that allows workers to connect the reinforcing cages beneath it.

[0055] The temporary support jig 18 includes a locking portion 18a that engages with the lowest reinforcing ring 33 of the upper reinforcing cage 30A, and a housing portion 18b in which the locking portion 18a is housed so that it can be moved in and out, with the housing portion 18b fixed on the base portion 12a. The temporary support jig 18 also includes a sliding mechanism (not shown), such as a hydraulic slider, for moving the locking portion 18a in and out of the housing portion 18b. The locking portion 18a is made of a member with a shape and material that can be inserted between adjacent main reinforcing bars 31 of the reinforcing cage 30A and can support the upper reinforcing cage 30A. In addition to being fixed on the base 12a, the mounting configuration of the housing section 18b may also be, for example, fitted into the base 12a, formed on the base 12a, or integrated with the base 12a so that the upper surface of the base 12a becomes flat.

[0056] The moving mechanism 13 includes two rail sections 14 that movably support the legs 12b of the gantry frame 12. The two rail sections 14 are an example of guide sections and are arranged parallel to each other on both sides of the pile hole 4 with a predetermined distance between them and have a predetermined length. The predetermined length is at least longer than the diameter of the pile hole 4 and is set to a length such that the gantry frame 12 does not interfere with construction work when the pair of gantry frames 12 are retracted from the pile hole 4.

[0057] Furthermore, the legs 12b of the gantry frame 12 are equipped with wheels (not shown) at their lower ends, and these wheels are mounted on the rail section 14. The wheels also have a stopper function that holds their rotation. Therefore, it is possible for an operator to manually move the gantry frame 12 along the rail section 14, or to hold it in any position to fix the gantry frame 12 in place. In another configuration example, the rail section 14 may be composed of a hydraulic slide rail or an electric slide rail, etc. Furthermore, the base portion 12a of the gantry frame 12 also functions as an evacuation shelter to ensure the safety of workers when moving and transporting suspended loads such as reinforcing cages and casings above the pile holes 4. Preferably, the size (area) of the base portion 12a is large enough to allow at least multiple workers to take refuge beneath it. By adopting this structure, when moving the suspended load above the pile hole 4, the worker can be kept safely under the base portion 12a of the gantry frame 12, allowing for a smooth transition to the next task after the load has been moved, thereby increasing work efficiency.

[0058] The base 15 comprises two side plates 16 attached to both ends of two parallel rail sections 14, and support sections 17 that support each rail section 14. The side plates 16 also function as wheel stops for the gate-type frame 12.

[0059] Furthermore, a guard 19 is attached to the base portion 12a of the gate-shaped frame 12 that constitutes the temporary support section 11 to prevent the upper reinforcing cage 30A, which is temporarily supported, from collapsing. The guard 19 comprises two support columns 19a erected on the base portion 12a, and an arc-shaped guard portion 19b attached to the upper part of these support columns 19a. The guard portion 19b has an arc shape that is larger than the pile hole 4.

[0060] Next, referring to Figure 1, we will explain the connection process in the construction of the reinforcing cage. First, we will explain the process leading up to the state shown in Figure 1(a). First, an earth drill excavator equipped with a crane function (not shown) and a temporary load support device 10 are installed horizontally on the ground. At this time, the center of the temporary load support device 10 is aligned with the pile center. Next, the Kelly bar (not shown) of the earth drill excavator is aligned with the pile center, and a drilling bucket (not shown) is attached to the tip of the Kelly bar, and drilling is performed to the installation depth of the surface casing 20B. Next, the surface casing 20B is installed in the excavated hole. After the surface casing 20B is installed, drilling is performed to a predetermined depth while injecting stabilizing fluid to form the pile hole 4, and then pile bottom treatment is performed.

[0061] Next, the process moves to the installation process shown in Figure 1, in which the reinforcing cages are connected and installed in the pile hole 4. The installation process involves inserting the reinforcing cages, suspended by the crane of the earth drill excavator, vertically into the center of the pile hole 4. The installation process includes a connection process in which the upper reinforcing cage 30A, suspended by the crane, is connected to the lower reinforcing cage 30B, which has been pre-installed in the pile hole 4 and is suspended from the pile hole 4, i.e., the surface casing 20B, with the cage protruding a predetermined amount from the surface casing 20B.

[0062] The upper reinforcing cage 30A is constructed in a substantially cylindrical shape and includes a plurality of main reinforcing bars (vertical bars) 31, a plurality of hoop reinforcing bars (horizontal bars) 32 that intersect with these main reinforcing bars 31, and a plurality of reinforcing rings 33 that intersect with these main reinforcing bars 31. The intersections of these main reinforcing bars 31 and reinforcing rings 33 are fixed by various reinforcing bar fixing fittings, wire ties, etc. (not shown), and the intersections of the main reinforcing bars 31 and hoop reinforcing bars 32 are fixed by wire ties, fittings, etc. (not shown). The upper reinforcing cage 30A consists of a single cage before connection. The size of the reinforcing cage 30A varies from construction site to construction site, with a diameter of approximately 0.6m to 3m, and the length of a single reinforcing cage 30A can reach approximately 12m to 14m. The main reinforcement bars 31 may be arranged individually, or two bars may be bundled together horizontally or vertically. The upper reinforcing cage 30A may be constructed with larger diameter and more main reinforcement bars 31 than the lower reinforcing cage 30B.

[0063] The lower reinforcing cage 30B shows the reinforcing cage suspended in the pile hole 4. Similar to the upper reinforcing cage 30A, it is composed of multiple main reinforcements 31, multiple hoop reinforcements (horizontal reinforcements) 32, and multiple reinforcing rings 33, and is constructed in a roughly cylindrical shape. Depending on the stage of the connection process, the lower reinforcing cage 30B may consist of one cage or two or more connected cages. Note that the lower reinforcing cage 30B may also include reinforcing cages that do not have multiple reinforcing rings 33. The lower reinforcing cage 30B is suspended from the pile hole 4, with its uppermost reinforcing ring 33 temporarily supported by a jig (not shown) for suspension bars attached to the opening of the surface casing 20B.

[0064] In the connection process, first, the lower reinforcing cage 30B is lifted into the pile hole 4 using a crane, and the portion above the uppermost reinforcing ring 33 is held in a position where it protrudes from the pile hole 4, i.e., from the surface casing 20B. Then, a jig for lifting reinforcement (not shown) is attached to the opening of the surface casing 20B, and the uppermost reinforcing ring 33 is locked to the jig for lifting reinforcement, so that the lower reinforcing cage 30B is suspended in the pile hole 4 as shown in Figure 1(a).

[0065] Next, the temporary load support device 10 is set up. First, the pair of gantry frames 12, which had been retracted at both ends of the rail section 14, are moved towards the center, near the lower reinforcing cage 30B. Next, the locking portion 18a of the temporary support jig 18 provided on the base portion 12a of the gantry frame 12 is extended horizontally from the housing portion 18b toward the pile center. The length of the extension is such that the locking portion 18a can be locked to the lowest reinforcing ring 33 of the upper reinforcing cage 30A.

[0066] After setting up the temporary load support device 10, as shown in Figure 1(a), the upper reinforcing cage 30A, which is suspended by the crane of an earth drill excavator (not shown), is moved directly above the lower reinforcing cage 30B, and then the upper reinforcing cage 30A is lowered. Subsequently, as shown in Figure 1(b), the lowermost reinforcing ring 33 of the upper reinforcing cage 30A is received by the locking part 18a of the temporary support jig 18, thereby temporarily supporting the upper reinforcing cage 30A with the temporary load support device 10. Note that even in this temporary support state, the upper reinforcing cage 30A remains suspended by the crane.

[0067] Subsequently, the worker connects the lower part of the upper reinforcing cage 30A, which is temporarily supported by the temporary load support device 10, below the gate-type frame 12, that is, the main reinforcing bars 31 below the lowest reinforcing ring 33, with the upper part of the lower reinforcing cage 30B, which is protruding above the surface casing 20B, that is, the main reinforcing bars 31 above the uppermost reinforcing ring 33, using a connector (not shown). In cases where the main reinforcement bars are overlapped horizontally, as shown in Figure 1(b), fixing hardware such as U-bolts can be used. In cases where the main reinforcement bars are overlapped vertically, connectors such as mechanical joints can be used. The type of connector used is appropriately selected according to the connection method.

[0068] After completing the connection work between the upper reinforcing cage 30A and the lower reinforcing cage 30B, which are suspended by the crane, the connected reinforcing cage 30 is lifted slightly by the crane to release the temporary support state at the temporary load support device 10, and the locking portion 18a of the temporary support jig 18 is housed in the housing portion 18b. Next, the connected reinforcing cages 30C, suspended by a crane, are lowered into the pile holes 4. If there are more reinforcing cages to be connected, the connection process is repeated as described above, with the reinforcing cages 30C suspended in the pile holes 4. On the other hand, if there are no more reinforcing cages to be connected, the reinforcing cages 30C are lowered to a predetermined depth in the pile holes 4, completing the installation process and proceeding to the next concrete pouring process.

[0069] According to the construction method for cast-in-place piles in the above embodiment (1), in the reinforcing cage connection process, with the lowermost reinforcing ring 33 of the upper reinforcing cage 30A temporarily supported by the temporary support jig 18 provided on the gate-shaped frame 12 of the suspended load temporary support device 10, it becomes possible to connect the main reinforcement bars 31 below the lowermost reinforcing ring 33 of the upper reinforcing cage 30A and the main reinforcement bars 31 above the uppermost reinforcing ring 33 of the lower reinforcing cage 30B, which is temporarily supported in the pile hole 4, using a connector. In other words, the temporary load support device 10 provides stable temporary support to the upper reinforcing cage 30A suspended by the crane, thus preventing accidents such as the upper reinforcing cage 30A swinging or falling during the connection process. Furthermore, the temporary support portion 11 of the temporary load support device 10 allows the upper reinforcing cage 30A to be temporarily supported without hindering the connection work. Therefore, it becomes possible to carry out the construction while ensuring the safety of the workers performing the reinforcing cage connection work, thereby improving safety and work efficiency during construction.

[0070] Furthermore, according to the above-described method for constructing cast-in-place piles, the temporary support jig 18 is positioned so that it can support the lowest reinforcing ring 33 of the upper reinforcing cage 30A at four locations (on diagonal lines dividing the reinforcing ring 33 into four equal parts), thereby allowing the upper reinforcing cage 30A to be temporarily supported in a stable state.

[0071] Furthermore, according to the above-described method for constructing cast-in-place piles, after connecting the upper reinforcing cage 30A and the lower reinforcing cage 30B, the temporary support of the upper reinforcing cage 30A by the temporary load support device 10 is released, and then the connected reinforcing cage 30C, which is suspended by a crane, is lowered into the pile hole 4. This makes it possible to lower the connected reinforcing cage 30C into the pile hole 4 more safely.

[0072] Furthermore, according to the temporary load support device 10 used in the construction method of cast-in-place piles according to the above embodiment (1), the temporary support section 11, which is equipped with a gate-type frame 12 and a temporary support jig 18, can stably temporarily support the upper reinforcing cage 30A suspended by a crane above the pile hole 4. Therefore, safety during the reinforcing cage connection process can be ensured, and the reinforcing cage connection work can be performed efficiently while securing working space. Furthermore, since the gantry frame 12 can be moved horizontally by the moving mechanism 13, the temporary support section 11 can be retracted during processes that do not utilize it, so that the temporary support section 11 does not interfere with construction work.

[0073] Furthermore, according to the above-described temporary load support device 10, the temporary support jig 18 is equipped with a locking portion 18a that can be moved in and out of the storage portion 18b, so that the temporary support work of the upper reinforcing cage 30A can be efficiently performed by moving the locking portion 18a in and out. Furthermore, with the above-described temporary load support device 10, since the legs 12b of the gantry frame 12 are configured to be extendable and retractable, the height position for temporarily supporting the upper reinforcing cage 30A can be adjusted according to the specifications of the reinforcing cage, thereby ensuring an appropriate working space. Furthermore, with the above-described temporary load support device 10, since the guard 19 is provided on the gantry frame 12, it is possible to prevent the collapse of the upper reinforcing cage 30A that is temporarily supported, thereby further enhancing work safety. Note that the device may also be configured without the guard 19, or the guard 19 may be configured to be detachable from the gantry frame 12. Furthermore, the above-mentioned temporary load support device 10 allows the base portion a of the gantry frame 12 to function as an evacuation shelter for workers. When moving the suspended load above the pile hole 4, workers can be safely positioned under the base portion 12a of the gantry frame 12, allowing for a smooth transition to the next task after the load has been moved, thereby increasing work efficiency.

[0074] In the above-mentioned temporary load support device 10, the locking portion 18a constituting the temporary support jig 18 is configured to be able to be moved in and out of the storage portion 18b. However, in another configuration example, the locking portion 18a may be fixed in place. In that case, instead of moving the locking portion 18a in and out, the gantry frame 12 can be moved. In another configuration example, each rail section 14 may be divided in the middle along its longitudinal direction, and the left and right temporary support sections 11 may be separable. This configuration facilitates the transportation of the device. Furthermore, in the above-described temporary load support device 10, the support mechanism 21 includes a moving mechanism 13 and a base 15, and supports the gantry frame 12 so that it can move horizontally. However, in another configuration example, the support mechanism 21 may be configured as a mechanism that supports the gantry frame 12 in a fixed state.

[0075] Figure 3 is a diagram illustrating an excavator equipped with a temporary load support device used in the construction method of cast-in-place piles according to embodiment (2), where (a) is a plan view and (b) is a side view. The temporary load support device 10 used in the construction method of cast-in-place piles according to the above embodiment (1) was a device compatible with the earth drill method. On the other hand, the temporary load support device 10A used in the construction method of cast-in-place piles according to embodiment (2) is a device compatible with the all-casing method and is attached to the excavator 1 for the all-casing method. In Figure 3, components having the same function as the temporary load support device 10 shown in Figure 2 are denoted by the same reference numerals, and their descriptions are omitted.

[0076] The excavator 1, for example, is equipped with the function of a full-circumference rotating excavator, and is capable of cutting and pressing in the casing 20 while rotating it all around, or vertically pulling out the casing 20. As described in the background technology section, the all-casing method includes an excavation process, an erection process, and a casting process.

[0077] The temporary load support device 10A comprises a temporary support section 11, a moving mechanism 13 for moving the temporary support section 11 in a predetermined direction, in this case, horizontally, and a base 15 to which the moving mechanism 13 is attached. The base 15 or the moving mechanism 13 is configured to be attachable to the excavator 1. The moving mechanism 13 and the base 15 together constitute a support mechanism 21 that supports the temporary support section 11.

[0078] The temporary support section 11 is a structural component used to temporarily support the upper reinforcing cage, which is suspended by a crane (not shown), above the excavator 1 during the reinforcing cage connection process performed in the construction process, or to temporarily support the detached casing 20A (see Figure 5) above the excavator 1 during the casing removal method performed in the concrete pouring process. The temporary support section 11 consists of a pair of gantry frames 12 and temporary support jigs 18 arranged on each gantry frame 12. The detailed configuration of the temporary support section 11 is the same as that of the temporary support section 11 of the suspended load temporary support device 10 described above, so its explanation is omitted here. Although the temporary load support device 10A shown in Figure 3 does not have the guard 19 provided on the temporary load support device 10 described above, the temporary load support device 10A may also be equipped with the guard 19.

[0079] The moving mechanism 13 is composed of two rail sections 14 that movably support the legs 12b of the gantry frame 12. These rail sections 14 are attached to the excavator 1 in a manner that is longer than the width of the work platform 2 of the excavator 1 and is positioned outside the work platform 2. The rail sections 14 are an example of guide sections. The detailed configuration of the moving mechanism 13 is the same as that of the moving mechanism 13 of the temporary load support device 10 described above, so its explanation is omitted here.

[0080] The base 15 comprises two side plates 16 attached to both ends of two parallel rail sections 14, and a support section 17 that supports the two rail sections 14. The configuration for attaching the base 15 or the moving mechanism 13 to the excavator 1 is not particularly limited, as long as the mounting structure has sufficient strength to temporarily support the upper reinforcing cage suspended by the crane or the detached casing 20A. For example, the support portion 17 of the base 15 or the rail portion 14 of the moving mechanism 13 can be attached to the work platform 2 or main body 3 of the excavator 1 using fasteners such as bolts, connecting plates, support plates placed on the work platform 2, or other fixing devices. A counterweight 3a for reaction force can be attached to the main body 3 of the excavator 1 as needed.

[0081] Next, a method for constructing cast-in-place piles according to embodiment (2) will be described. In the construction method for cast-in-place piles according to embodiment (2), the steps that utilize the temporary load support device 10A equipped on the excavator 1 are the reinforcing cage connection step included in the erection step and the casing removal step included in the pouring step.

[0082] The reinforcing cage connection process included in the erection process in Embodiment (2) differs from Embodiment (1) only in that a temporary load support device 10A is attached to the excavator 1 and the upper opening 20a of the casing 20 (see Figure 4) is located above the work platform 2 of the excavator 1. Therefore, the reinforcing cage connection process included in the erection process in Embodiment (2) can be performed using the temporary load support device 10A in basically the same procedure as the reinforcing cage connection process included in the erection process in Embodiment (1) described above, so its explanation is omitted here.

[0083] Next, the casing removal process included in the casting process in Embodiment (2) will be explained based on Figures 4 to 7. As mentioned above, in Embodiment (2), the all-casing method is applied to the construction method of the cast-in-place piles.

[0084] Figure 4(a) shows the state after the first concrete (first layer) has been poured to the predetermined height (pouring length), and Figure 4(b) shows the state after one casing 20 has been removed. Figure 5(a) shows the detached casing 20A being supported by the temporary support section 11 of the temporary load support device 10A, and Figure 5(b) shows the state after the re-suspending of the reinforcing cage 30. Figure 6(a) shows the state after the detached casing 20A has been removed, and Figure 6(b) shows the state after a portion of the tremie pipe 40 has been detached and removed. Figure 7 shows the state after the second (second layer) of ready-mix concrete has been poured to the specified height.

[0085] First, we will explain the process leading up to the state shown in Figure 4(a). First, the excavator 1 for cast-in-place piles is installed in the ground. Specifically, the excavator 1 is lifted by a crane, such as a crawler crane (not shown), and installed on a pre-installed platform on the ground, with the pile center aligned. The excavator 1 is equipped with a temporary load support device 10A.

[0086] Next, the process moves to the excavation stage. The excavation stage involves pressing the casing 20 into the ground and excavating inside the casing 20 while adding extensions to form a pile hole 4 of a predetermined depth. Specifically, first, a casing 20 (first casing) is set in the excavator 1, and the casing 20 is rotated and cut into the ground. Then, a hammer grab is attached to the crane and the inside of the casing 20 is excavated. Once the first casing 20 is pressed into the ground to the predetermined depth and the internal excavation is complete, the hammer grab is temporarily lifted, and the extension casing 20 is lifted by the crane and connected to the first casing 20. This process is repeated to excavate to the predetermined depth and form the pile hole 4, after which pile bottom treatment is performed. Depending on the site conditions, a drilling bucket may be used instead of a hammer grab.

[0087] Next, the process moves to the installation stage, in which the reinforcing cages are connected and erected in the pile holes 4. The installation stage involves lifting the reinforcing cages 30 with a crane and inserting the reinforcing cages 30 into the inside of the casing 20, aligning them with the axis of the casing 20 inside the pile hole 4. This connection stage is basically performed using the temporary load support device 10A, following the same procedure as the connection stage in embodiment (1) explained using Figure 1, so its explanation is omitted here.

[0088] The reinforced concrete cage 30 shown in Figure 4 is constructed by connecting multiple reinforced concrete cages. The upper (pile head) reinforced concrete cage is larger in diameter and made up of more main reinforcement bars than the lower reinforced concrete cage. Although the illustrated reinforced concrete cage 30 consists of three connected reinforced concrete cages, the number of connected cages is designed appropriately according to the pile length, pile diameter, etc.

[0089] A crane (not shown) is used to erect the steel cage 30. It is preferable that this crane be equipped with at least two hooks, for example, a main hook 6 attached to the wire of a first (main) winch as a first hoisting means, and a sub-hook 7 attached to the wire of a second (auxiliary) winch as a second hoisting means. It is even more preferable to use a device that, in addition to the main hook 6 and sub-hook 7, is equipped with a grandchild hook 8 attached to the wire of a third winch as a third hoisting means.

[0090] In the construction process of the reinforcing cage 30, the reinforcing cage 30 is suspended by a suspension device 6a, which includes, for example, a traverser 6b suspended from a main hook 6, and a suspension reinforcing bar 6c suspended from the traverser 6b. As a method for attaching the suspension bars 6c to the reinforcing cage 30, for example, a hook member or shackle (not shown) fixed to the lower end of the suspension bar 6c can be used to secure it to the reinforcing ring 33 of the reinforcing cage 30. In Figure 4, an example of the reinforcing cage 30 being suspended at two points is shown, but depending on the size of the reinforcing cage 30, it may be suspended at four points. In this case, an annular ring member may be used instead of the traverser 6b.

[0091] Furthermore, the reinforcing cage 30 is not supported in a freestanding state within the pile hole 4, but is held in a suspended state within the pile hole 4 (not in contact with the bottom of the pile). For example, as shown in Figure 4(a), the reinforcing cage 30 may be held in a suspended state by a crane, or it may be held in a suspended state by a lifting jig 25 (Figure 5(b)) installed at the upper opening 20a of the casing 20.

[0092] Next, the process proceeds to pouring concrete 5 into the pile hole 4 while the reinforcing cage 30 is suspended in the pile hole 4. First, as shown in Figure 4(a), the tremie pipe 40 is erected in the center of the reinforcing cage 30, the hopper section 41 is attached to the upper end of the tremie pipe 40, and the tremie pipe 40 is supported by the reinforcing bars 26 placed in the upper opening 20a of the casing 20. A crane is used to erect the tremie pipe 40.

[0093] Next, the pouring of ready-mix concrete 5 is started. That is, the ready-mix concrete 5 is poured into the tremie pipe 40, and while checking the amount of concrete poured, the concrete 5 is poured from the bottom of the pile up to a predetermined height, until the first layer of ready-mix concrete 5 is poured up to a predetermined height (for example, the height of one casing), as shown in Figure 4(a).

[0094] Next, we will explain the casing removal process that takes place during the concrete pouring process. As shown in Figure 4(a), after pouring the ready-mix concrete 5 to a predetermined height, as shown in Figure 4(b), the tremie pipe 40 is suspended and supported by a lifting device 8a attached to the crane's secondary hook 8, and the reinforcing cage 30 is suspended and supported by a lifting device 6a attached to the crane's main hook 6. In addition, before pulling out the casing 20, a lifting device 7a attached to the crane's secondary hook 7 is attached to the casing 20 that is protruding onto the work platform 2. Alternatively, instead of suspending the tremie pipe 40 with the lifting device 8a attached to the crane's secondary hook 8, the lifting device 8a may be attached to the traverser 6b in advance, and the tremie pipe 40 may be suspended and supported by the lifting device 8a attached to the traverser 6b.

[0095] Next, the excavator 1 begins the process of pulling out one section of casing 20. The excavator 1 is equipped with a function to pull out casing 20 vertically while holding it in place. When the connecting section 20b of casing 20 reaches the workbench 2, the pulling operation is stopped, the metal fittings of the connecting section 20b of casing 20 are removed, and then the detached casing 20A is lifted by a crane.

[0096] Subsequently, as shown in Figure 5(a), when the lower end of the detached casing 20A is above the temporary support jig 18 of the temporary load support device 10A, the lifting of the detached casing 20A is stopped. Next, the process proceeds to a temporary support step in which the temporary support section 11 of the temporary load support device 10A is placed beneath the casing 20A, which has been lifted and supported by a crane. Specifically, as shown in Figure 4(b), the gantry frames 12 of the temporary load support devices 10A, located on both sides of the work platform 2 of the excavator 1, are moved to a location close to the casing 20A that has been lifted and supported by a crane, as shown in Figure 5(a). Then, the locking portion 18a of the temporary support jig 18 is extended from the housing portion 18b, and the detached casing 20A is placed on top of the locking portion 18a to create a temporary support state.

[0097] In another configuration, the locking portion 18a may be housed in the housing portion 18b, and the detached casing 20A may be placed on top of the housing portion 18b to create a temporary support. In yet another configuration, if the temporary support jig 18 is fitted into the base portion 12a of the gantry frame 12, the detached casing 20A may be placed on top of the base portion 12a of the gantry frame 12 to create a temporary support.

[0098] Subsequently, the process proceeds to the replacement of the reinforcing cage 30 (first replacement process) and the replacement of the tremie pipe 40 (second replacement process), as shown in Figure 5(b). In the process of replacing the reinforcing cage 30, the reinforcing cage 30, which is suspended by the crane's main hook 6 as shown in Figure 5(a), is replaced by being suspended from the upper opening 20a of the casing 20 (on the work platform 2) which is embedded in the ground. For example, as shown in Figure 5(b), a lifting jig 25 for the reinforcing bars 6c is attached to the upper opening 20a of the casing 20. The reinforcing bars 6c that are suspending the reinforcing cage 30 are then fixed to the lifting jig 25, and the reinforcing cage 30 is suspended and supported in the pile hole 4 by the lifting jig 25 and the reinforcing bars 6c. Next, the crane's main hook 6 and traverser 6b that were suspending the reinforcing cage 30 are pulled up.

[0099] Furthermore, in the process of replacing the tremie pipe 40, the tremie pipe 40, which is suspended by the crane's secondary hook 8 as shown in Figure 5(a), is replaced by being suspended from the upper opening 20a of the casing 20 (on the work platform 2) which is embedded in the ground. For example, as shown in Figure 5(b), two reinforcing bars 26 are placed in the upper opening 20a of the casing 20, and the flange at the upper end of the tremie pipe 40 is placed between the two reinforcing bars 26 to suspend and support the tremie pipe 40 in the pile hole 4, and the crane's secondary hook 8 and lifting device 8a that were suspending the tremie pipe 40 are then pulled up.

[0100] In the process of replacing the reinforcing cage 30 (first replacement process) and the process of replacing the tremie pipe 40 (second replacement process), the detached casing 20A is temporarily supported by being placed on a temporary support jig 18 provided on the gantry frame 12 of the temporary load support device 10A, so that the replacement work can be carried out while ensuring worker safety.

[0101] After completing the re-suspending process for the steel cage 30 (first re-suspending process) and the re-suspending process for the tremie pipe 40 (second re-suspending process), the detached casing 20A is removed, as shown in Figure 6(a). Specifically, the casing 20A, which is temporarily supported on a temporary support jig 18 provided on the gantry frame 12 of the temporary load support device 10A, is lifted by the crane, the crane is rotated to lower the casing 20A to a designated temporary storage area, the crane's lifting device 7a is removed from the casing 20A, and the lifting device 7a is lifted together with the sub-hook 7 to return the crane to its designated position. After the casing removal process is completed, as shown in Figure 6(a), the gantry frame 12 of the temporary load support device 10A is moved along the rail section 14 to both sides of the work table 2, and the gantry frame 12 is returned to its predetermined position, i.e., the return process is performed. In parallel, the locking portion 18a of the temporary support jig 18 may be housed in the housing portion 18b.

[0102] After that, the process moves on to removing the tremie tube. As shown in Figure 6(b), in the tremie pipe removal process, the tremie pipe 40, which is suspended from the upper opening 20a of the casing 20 (on the work platform 2) embedded in the ground, is re-suspended by the crane's secondary hook 8. Then, the tremie pipe 40 is lifted by the crane and the lifting is stopped when the connecting part of the tremie pipe 40 is positioned above the upper opening 20a of the casing 20. The amount of lifting of the tremie pipe 40 is within a range that allows the lower end of the tremie pipe 40 in the pile hole 4 to remain inserted into the ready-mix concrete 5 by 2m or more.

[0103] Subsequently, two reinforcing bars 26 are placed in the upper opening 20a of the casing 20, and the flange portion of the connecting part of the tremie pipe 40 is placed between the two reinforcing bars 26, thereby suspending and supporting the tremie pipe 40 in the pile hole 4. After that, the fittings of the connecting part of the tremie pipe 40 are removed and detached, the tremie pipe 40A suspended from the crane's secondary hook 8 is lifted, the crane is rotated to lower the tremie pipe 40A to a designated temporary storage area, the crane's lifting device 8a is removed from the tremie pipe 40A, and the lifting device 8a is lifted together with the secondary hook 8 to return the crane to its designated position. Alternatively, the detached tremie pipe 40 may be lifted using the secondary hook 7 or the primary hook 6 instead of the crane's secondary hook 8.

[0104] After the tremie pipe removal process is completed, the reinforcing cage 30, which was suspended by lifting bars 6c and lifting jigs 25 from the upper opening 20a of the casing 20 (on the work platform 2) embedded in the ground as shown in Figure 6(b), is replaced with a new suspension operation (third suspension replacement process) as shown in Figure 7, where it is suspended by the crane's main hook 6 and lifting device 6a. After that, the process of pouring the second (second stage) concrete 5 begins. That is, the concrete 5 is poured into the tremie pipe 40, and the concrete 5 is poured up to the predetermined height while checking the amount of concrete poured.

[0105] Subsequently, the casing removal process described in Figures 4(b) to 6(b) is repeated, and ready-mix concrete 5 is poured up to the pile head, completing the pouring process. After that, backfilling is carried out, and the construction of the next cast-in-place pile is started.

[0106] According to the construction method for cast-in-place piles in the above embodiment (2), in the process of connecting the reinforcing cages in the all-casing method, with the lowermost reinforcing ring 33 of the upper reinforcing cage temporarily supported by the temporary support jig 18 provided on the gate-shaped frame 12 of the suspended load temporary support device 10A, it becomes possible to connect the main reinforcement bars 31 below the lowermost reinforcing ring 33 of the upper reinforcing cage and the main reinforcement bars 31 above the uppermost reinforcing ring 33 of the lower reinforcing cage, which is temporarily supported in the pile hole 4, using a connector. In other words, the temporary load support device 10A provides stable temporary support to the upper reinforcing cage suspended by the crane, thus preventing accidents such as the upper reinforcing cage swinging or falling during the connection process. Furthermore, the temporary load support device 10A allows the upper reinforcing cage to be temporarily supported in a way that does not hinder the connection work. Therefore, it becomes possible to carry out construction while ensuring the safety of workers performing the reinforced steel cage connection work, thereby improving safety and work efficiency during construction.

[0107] Furthermore, according to the construction method for cast-in-place piles in the above embodiment (2), in the casing removal process of the driving process in the all-casing method, the following steps are performed: a step of lifting and supporting the detached casing 20A with the crane's sub-hook 7; a temporary support step of placing the temporary support portion 11 of the suspended load temporary support device 10A (i.e., the locking portion 18a of the temporary support jig 18) below the casing 20A that has been lifted and supported with the sub-hook 7; and a first suspension step of transferring the reinforcing cage 30, which is suspended by the crane's main hook 6, to the upper opening 20a of the casing 20 embedded in the ground after the temporary support portion 11 has been placed in the temporary support step. Therefore, the first lifting process, i.e., the lifting operation of the reinforcing cage, can be performed after the casing 20A, which has been lifted and supported by the crane's sub-hook 7, has been temporarily supported by the locking portion 18a of the temporary support jig 18 of the temporary load support device 10A. Therefore, it is possible to prevent accidents such as the casing 20A being lifted and supported by the sub-hook 7 falling, ensuring the safety of the workers performing the rebar cage replacement work, and thereby improving work safety during construction.

[0108] Furthermore, according to the above-described method for constructing cast-in-place piles, the casing 20A, which has been lifted and supported by the crane's sub-hook 7, can be temporarily supported by the locking portion 18a of the temporary support jig 18 of the temporary load support device 10A before the second lifting process, i.e., the lifting of the tremie pipe 40, can be performed. Therefore, it is possible to prevent accidents such as the casing 20A being lifted and supported by the sub-hook 7 falling, ensuring the safety of the workers performing the tremie pipe replacement work, and thereby improving safety during construction.

[0109] Furthermore, according to the above-described method for constructing cast-in-place piles, the pouring process includes a return process and a third lifting process after the casing removal process. Therefore, in the third lifting process, the temporary support portion 11 of the temporary load support device 10A does not interfere with the lifting work of the reinforcing cage 30, and the subsequent pouring of ready-mix concrete 5 and the subsequent casing removal process can be carried out smoothly.

[0110] Furthermore, according to the above-described construction method for cast-in-place piles, the tremie pipe removal process is performed either before or after the casing removal process, so the work of lifting the tremie pipe 40 and detaching and removing a portion of the tremie pipe 40A can be carried out safely and smoothly.

[0111] Furthermore, according to the temporary load support device 10A used in the construction method of cast-in-place piles according to embodiment (2), the temporary support section 11, which includes a gate-type frame 12 and a temporary support jig 18, allows the upper reinforcing cage suspended by the crane to be stably temporarily supported above the pile hole 4 during the reinforcing cage connection process. Therefore, safety during the reinforcing cage connection process can be ensured, and the reinforcing cage connection work can be performed while securing working space. Furthermore, with the above-mentioned temporary load support device 10A, the detached casing 20A can be temporarily supported by the temporary support section 11, which is equipped with a gantry frame 12 and a temporary support jig 18, thereby ensuring safety during the casing removal process. Furthermore, since the temporary support section 11 can be moved horizontally by the moving mechanism 13, the temporary support section 11 can be prevented from interfering with construction work in processes other than the reinforcing cage connection process and the casing removal process, when the temporary support section 11 is not used. Furthermore, since the temporary load support device 10A can be attached to the excavator 1, it is possible to provide a device that enhances work safety with a small number of components, such as the temporary support section 11, the moving mechanism 13, and the base 15, that is, with a compact and low-cost configuration.

[0112] Furthermore, in the temporary load support device 10A, the temporary support section 11 is composed of two gantry frames 12, and the distance between the legs 12b of these gantry frames 12 is greater than the vertical width of the work platform 2 of the excavator 1. Therefore, the lifting and replacement work (first lifting and second lifting processes) of the reinforcing cage 30 and tremie pipe 40 can be performed with the detached casing 20A placed on the gantry frames 12, that is, while ensuring a safe working space. Note that the structure of the gantry frames 12 is not limited to the illustrated form and can be changed to various forms. Furthermore, the moving mechanism 13 is configured to include a rail section 14 as a guide section, and the rail section 14 is configured to be attached to the excavator 1 while being longer than the width of the workbench 2 and positioned outside the workbench 2. Therefore, in processes other than the casing removal process, the gantry frame 12 can be moved to the outside of the workbench 2, so that the gantry frame 12 does not interfere with the construction work.

[0113] Furthermore, since the excavator 1 for cast-in-place piles according to this embodiment is equipped with a temporary load support device 10A, it can function as an excavator that takes advantage of the effects of the temporary load support device 10A, thereby improving work safety during the construction of cast-in-place piles.

[0114] In the above embodiment (2), the all-casing method was applied as an example of a method for constructing cast-in-place piles. However, the present invention can also be applied to other methods for constructing cast-in-place piles that include the step of pressing the casing into the ground and then pulling it out.

[0115] Furthermore, although the temporary load support device 10A according to the above embodiment (2) is configured so that the base 15 or the moving mechanism 13 can be attached to the excavator 1, the configuration of the temporary load support device according to the present invention is not limited thereto. In another embodiment of the temporary load support device, the base 15 may be positioned on the ground around the outer perimeter of the excavator 1. For example, the base 15 may be composed of a foundation including multiple support columns and may not be attached to the excavator 1. In this case, for example, the temporary load support device would be installed on the ground after the excavator 1 has been installed on the ground. Yet another embodiment of the temporary load support device may be configured to be positioned on the work platform 2 of the excavator 1.

[0116] Furthermore, in the temporary load support device 10A according to the above embodiment (2), the spacing between the legs 12b of the gantry frame 12 constituting the temporary support section 11 is greater than the width (length) of the work platform 2 of the excavator 1, and the rail section 14 is arranged on the outside of the work platform 2. However, the configuration of the temporary load support device according to the present invention is not limited to this. For example, if the excavator 1 is large and the work platform 2 has a large surface area, the spacing between the legs 12b of the gantry frame 12 may be smaller than the width (length) of the work platform 2 and larger than the diameter of the casing 20, and the rail section 14 may be attached to the upper surface of the work platform 2.

[0117] Furthermore, in the temporary load support device 10A according to the above embodiment (2), the moving mechanism 13 is equipped with a rail section 14 as a guide section, and is configured to move the gantry frame 12 linearly in the horizontal direction along the rail section 14 (in a parallel movement format). However, the configuration of the moving mechanism of the temporary load support device according to the present invention is not limited to this. In another embodiment of the temporary load support device, for example, one leg of each of the two gantry frames constituting the temporary support section is rotatably supported (pivoted) on a base provided at a certain interval (for example, an interval about the same as the diameter of the casing) on ​​one side of the work platform 2 of the excavator 1, and the base is configured to rotate horizontally around one of these legs. Then, as shown in the plan view of Figure 5(b), after rotating the bases of the two gantry frames to a position where they are parallel, the other leg of the two gantry frames may be attached to a base provided on the other side of the work platform 2 of the excavator 1 (the side opposite to the side facing the one side) (rotation movement type). Furthermore, in the above-described temporary load support device 10A, the support mechanism 21 includes a moving mechanism 13 and a base 15, and supports the gantry frame 12 so that it can move horizontally. However, in another configuration example, the support mechanism 21 may be configured as a mechanism that supports the gantry frame 12 in a fixed state. [Explanation of Symbols]

[0118] 1. Excavator 2 Workbenches 3. Main body 3a Counterweight 4 Pile hole 5. Ready-mix concrete 6. Main hook (first winding mechanism) 6a Lifting device 6b Traverser 6c suspension bars 7. Small hook (second retraction method) 7a Lifting device 8. Sun Hook (Method 3, Part 1) 8a Lifting device 10, 10A Suspended load temporary support device 11 Temporary support section 12 Gantry frame 12a Base 12b Legs 13 Moving mechanism 14. Rail section (guide section) 15 base 16 Side plate 17 Support part 18 Temporary support jig 18a Locking part 18b Storage area 19 Guard 19a Post 19b Guard section 20, 20A casing 20B Surface casing 20a Top opening 20b Connection part 21 Support mechanism 25 Lifting fixtures 26. Kanzashi muscle 30 Reinforced Iron Cage 30A Upper reinforcing cage 30B Lower reinforcing cage 30C Reinforced Steel Cage 31 Main reinforcement 32 Hoop Muscles 33 Reinforcement ring 40, 40A tremie tube 41 Hopper section

Claims

1. A method for constructing cast-in-place piles, which includes an installation process in which reinforcing cages are connected and then erected into the pile holes, The aforementioned construction process, The process includes a connecting step of connecting an upper reinforcing cage suspended by a crane with a lower reinforcing cage that has been previously suspended in the pile hole and is suspended in the pile hole with a predetermined amount protruding from the pile hole, The coupling process is, A method for constructing cast-in-place piles, characterized by including the step of connecting the lower part of the upper reinforcing cage and the upper part of the lower reinforcing cage with a connecting device, while the upper reinforcing cage is temporarily supported by a temporary load support device for temporarily supporting a load suspended by the crane.

2. The aforementioned reinforcing cage is composed of a plurality of main reinforcing bars, a plurality of hoop reinforcing bars arranged intersecting these main reinforcing bars, and a plurality of reinforcing rings arranged intersecting the plurality of main reinforcing bars. In the aforementioned coupling process, The method for constructing a cast-in-place pile according to claim 1, characterized in that the upper reinforcing cage is temporarily supported by receiving the lowest reinforcing ring constituting the upper reinforcing cage with the temporary support portion of the temporary load support device.

3. The method for constructing a cast-in-place pile according to claim 2, characterized in that the temporary support portion is positioned below the lowest reinforcing ring so as to support the lowest reinforcing ring at at least four locations.

4. The aforementioned construction process, A method for constructing a cast-in-place pile according to any one of claims 1 to 3, characterized in that, after connecting the upper reinforcing cage and the lower reinforcing cage in the connection step, the temporary support of the upper reinforcing cage by the temporary load support device is released, and then the upper reinforcing cage and the lower reinforcing cage suspended by the crane are lowered into the pile hole.

5. The aforementioned pile hole is formed by pressing a casing into the ground and excavating inside the casing while adding extensions. After the aforementioned construction process, the process includes pouring concrete into the pile hole while the reinforcing cage is suspended in the pile hole, The concrete casting process is, The process includes repeatedly performing the casing removal step, in which, after pouring the ready-mix concrete to a predetermined height, the reinforcing cage is suspended by the crane, and one casing is pulled out and separated, and then removed. The casing removal process described above is The process of lifting and supporting the detached casing with the crane, A temporary support step in which the casing, which has been suspended and supported by the crane, is temporarily supported by the temporary load support device, The method for constructing a cast-in-place pile according to claim 1, further comprising a first suspension step of, after the temporary support step, suspending the reinforcing cage, which is suspended by the crane, to the upper opening of the casing embedded in the ground.

6. The aforementioned concrete casting process, The process includes installing a tremie pipe in the pile hole, suspending the tremie pipe from the upper opening of the casing embedded in the ground, and then pouring the ready-mix concrete into the tremie pipe. The casing removal process described above is After pouring the ready-mix concrete to a predetermined height, the tremie pipe is suspended and supported by the crane. The method for constructing a cast-in-place pile according to claim 5, further comprising a second suspension step of suspending the tremie pipe, which is suspended and supported by the crane, to the upper opening of the casing embedded in the ground, after the temporary support step.

7. The aforementioned concrete casting process, After the casing removal step, a return step is performed to return the temporary load support device to its predetermined position. A method for constructing cast-in-place piles according to claim 5 or 6, characterized by including a third suspension step of changing the suspension of the reinforcing cage to a state in which it is suspended by the crane.

8. The aforementioned concrete casting process, The method for constructing a cast-in-place pile according to claim 6, characterized in that, before or after the casing removal step, the tremie pipe suspended from the upper opening of the casing embedded in the ground is suspended by the crane, the tremie pipe is pulled up and a portion of it is cut off and then removed.

9. A temporary load support device for use in the construction method of cast-in-place piles according to claim 1, A temporary support section for temporarily supporting the upper reinforcing cage suspended by the crane above the pile hole, A temporary load support device characterized by comprising a support mechanism that supports the temporary support portion.

10. The support mechanism is configured to include a moving mechanism for moving the temporary support portion in a predetermined direction, and a base to which the moving mechanism is attached. The temporary support section is composed of one or more gantry-type frames and temporary support jigs arranged on the gantry-type frames. The spacing between the legs of the aforementioned gate-type frame is greater than the diameter of the pile hole. The temporary load support device according to claim 9, characterized in that the moving mechanism includes a guide that movably supports the legs of the gantry frame.

11. The aforementioned temporary support jig A locking part that engages with the reinforcing ring of the upper reinforcing cage, The temporary load support device according to claim 10, further comprising a housing section in which the locking section is retractably housed.

12. The temporary load support device according to claim 10 or 11, characterized in that the legs of the gantry frame are configured to be extendable and retractable.

13. The temporary support device for suspended loads according to any one of claims 9 to 11, characterized in that the temporary support portion is provided with a guard for preventing the collapse of the upper reinforcing cage that is temporarily supported.

14. A temporary load support device used in the construction method of cast-in-place piles according to claim 5, A temporary support section for temporarily supporting the upper reinforcing cage suspended by the crane and the detached casing above the excavator for cast-in-place piles, A temporary load support device characterized by comprising a support mechanism that supports the temporary support portion.

15. The support mechanism is configured to include a moving mechanism for moving the temporary support portion in a predetermined direction, and a base to which the moving mechanism is attached. The temporary load support device according to claim 14, characterized in that the base or the moving mechanism is configured to be attachable to the excavator.

16. The temporary support section is composed of one or more gantry-type frames and temporary support jigs arranged on the gantry-type frames. The distance between the legs of the gantry frame is greater than the diameter of the casing. The aforementioned moving mechanism is configured to include a guide that movably supports the legs of the gantry frame, The temporary load support device according to claim 15, characterized in that the guide portion is longer than the diameter of the casing.

17. The aforementioned temporary support jig A locking portion that can be locked to at least the reinforcing ring of the upper reinforcing cage, The temporary load support device according to claim 16, further comprising a housing section in which the locking section is retractably housed.

18. An excavator for cast-in-place piles, characterized by being equipped with a temporary load support device as described in any one of claims 14 to 17.

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