JP2004263561A - Cast-in-place pile and its work execution method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a cast-in-place pile advantageous to a vertical load, a horizontal load and negative frictional force while proposing a work execution method for the cast-in-place pile having sure quality and economical efficiency. <P>SOLUTION: In the work execution method for the cast-in-place pile having a downward tapered taper section in at least a part of a shaft section for an under-reamed pile, a section from a pile shaft section to a bottom expanding section at a front tip is excavated by using a system, in which an excavation shape can be controlled so as to reach a fixed value on a monitor picture plane from the open-close status of an excavation bit for an expansible-contractible reverse excavator, and cement milk, mortar or a cement mixture is grouted from the front tip of the excavation bit to a part or the whole of the bottom expanding section through a drill pipe for the reverse excavator. In the work execution method, the excavation bit for the reverse excavator is pulled up on a ground, and a cage is built into an excavating pit and concrete is placed by using a tremie pipe, thus creating a pile body. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a cast-in-place pile capable of efficiently and economically increasing the supporting capacity of a large-diameter cast-in-place pile and an execution method thereof.

  Various types of large diameter cast-in-place piles have been proposed, including straight piles, bottom piles, head piles, tapered piles, hollow piles, and projecting piles. Also, in the construction method, the Benoto method, the reverse method, the earth drill method, the deep foundation method, and the like are selectively used depending on the construction conditions. However, for the pile shapes proposed so far, straight piles have often been used because the selection requirements are not clear and there is a problem in the construction method. Straight piles are relatively easy to construct, but are not always rational in view of the load acting on the piles and the cross-sectional shape of the piles. In addition, cast-in-place straight piles have no practical countermeasures on soft ground where negative frictional force is generated, and they have actually responded by reducing the supporting force. In addition, cast-in-place piles are generally easy to loosen because the hole is drilled in the ground and then filled with concrete. In practice, the quality is greatly influenced by the quality of the product, and it is desired to establish a reliable and efficient construction method.

  In response to such problems of straight piles, many cast-in-place cast-in-place piles have been adopted particularly in the field of construction. Expanded bottom cast-in-place piles are less susceptible to negative friction forces than straight piles, but require extra time to process slime and inspect excavated shapes. .

In addition, the inventor of the present application conducted a survey on a cast-in-place pile, an expanded bottom pile, a tapered pile, and related technical fields, and found the following patent document applicable as a background art of the present invention.
JP-A-52-14005 JP-A-59-34329 JP-A-60-23520 JP-A-4-146324 JP-A-6-108456 JP 2001-336149 A JP-A-58-222287

Large diameter cast-in-place piles have the following construction issues that need to be resolved.
That is, conventional slime treatment of cast-in-place piles lacks certainty, so there is a problem in securing quality such as supporting force, and much time is required for slime treatment. Further, in the case of the cast-in-place expanded pile, there is a specific problem that it is difficult to sufficiently perform slime treatment on the outer periphery of the expanded portion. Excavation shape inspection is performed on cast-in-place expanded piles, and this inspection requires a lot of time, and slime accumulation proceeds during that time. Even in the treatment of secondary slime performed before placing concrete, there is a problem that slime treatment of the expanded bottom portion, which greatly affects the supporting force, can hardly be performed, particularly in the outer peripheral portion of the reinforced cage.

  Also, in the construction of cast-in-place piles, stand pipes, casing pipes, outer shell steel pipes, etc. are used, but for the installation and removal of these, machines dedicated to the work, such as power jacks, vibro hammers, cranes, etc., are used. Was needed.

  Furthermore, there has been no system for efficiently and surely managing the construction of the tapered portion or the bottom portion when excavating the ground, and no system for performing an efficient excavation shape inspection.

  The present invention solves the above problems, proposes a cast-in-place pile that is advantageous against vertical loads, horizontal loads, and negative frictional forces, and proposes a method of constructing a cast-in-place pile having reliable quality and economy. It is.

The present invention employs the following means in order to solve the above problems.
In other words, the method for constructing a cast-in-place pile according to claim 1 is a method for constructing a cast-in-place pile having a tapered portion tapering downward in at least a part of the shaft portion of the expanded bottom pile. After drilling from the pile shaft to the bottom of the tip using a system that can control the drilling shape to a predetermined value on the monitoring screen based on the opening and closing status of the bit, the drill bit tip through the drill pipe of the reverse drilling machine Inject cement milk, mortar or cement mixture (hereinafter sometimes simply referred to as “cement milk” etc.) into a part or the whole of the expanded bottom from above and pull up the drill bit of the reverse excavator to the ground. After that, a pile body is constructed by laying a steel cage in the excavation hole and pouring concrete using a tremy tube.

  The method for constructing a cast-in-place pile according to claim 2 is a method for constructing a cast-in-place pile having a tapered portion tapered downward in at least a part of the shaft portion of the expanded bottom pile. After excavating the shaft part of the pile using a system that can control the excavation shape to a predetermined value on the monitoring screen from the opening and closing situation, at the time of excavation of the expanded part, part of the expanded diameter is smaller than the predetermined diameter. Once, the primary excavation is performed to approximately the final depth, and then cement milk or the like is injected from the tip of the excavation bit through the drill pipe of the reverse excavator into the enlarged bottom portion, and then the enlarged bottom portion is operated while operating the drill bit. After performing secondary excavation so as to obtain a shape and stirring and mixing the cement milk or the like and excavated soil, the excavation bit of the reverse excavator is pulled up to the ground, a reinforcing cage is set in the excavation hole, Using a Performing pouring REITs, characterized in that construct a pile body.

  The method for constructing a cast-in-place pile according to claim 3 is a method for constructing a cast-in-place pile having a tapered portion tapering downward in at least a part of a shaft portion of the expanded pile. After performing excavation from the shaft to the bottom of the final depth and slime treatment of the hole bottom using a system that can control the excavation shape to a predetermined value on the monitoring screen based on the expansion situation of the earth drill excavator Cement milk or the like is injected from the tip of the drilling bucket into part or all of the expanded bottom through the Keribar pipe, and the drilling bucket of the excavator is pulled up to the ground. It is characterized in that a pile body is created by pouring concrete using a pile.

  The method for constructing a cast-in-place pile according to claim 4 is a method for constructing a cast-in-place pile having a tapered portion tapering downward in at least a part of a shaft portion of the expanded bottom pile, wherein an expandable expandable bucket of an earth drill excavator is used. After excavating the shaft using a system that can control the excavation shape to a predetermined value on the monitoring screen from the opening and closing situation, in the excavation stage of the expanded bottom part, a part of the expanded bottom diameter is smaller than the predetermined diameter Once the primary excavation is performed to a nearly final depth with a small diameter, cement milk or the like is injected from the tip of the enlarged bucket through the kelly bar of the earth drill excavator, and then the expanded part is operated while operating the drill bit. While secondary drilling is performed so as to have a predetermined shape, the cement milk or the like and the excavated soil are stirred and mixed, and thereafter, the enlarged bit of the earth drill excavator is pulled up to the ground, and the rebar cage is built in the drill hole. Including, training It characterized in that it construct a pile body performs pouring of concrete using chromatography tube.

According to the construction method of the cast-in-place pile according to claims 1 to 4, the above-mentioned problem can be solved.
That is, in the construction method of the present invention, after excavating to the bottom of the pile, cement milk or the like is injected without raising the drill bit or the drill bucket, so that no slime is interposed at the tip of the pile, and Since the ground is not loosened, the pile support capacity corresponding to the original ground strength can be secured. In particular, since the slime treatment on the outer periphery of the reinforcing bar cage, which has conventionally been difficult, can be reliably performed, it is possible to reliably obtain the supporting force suitable for the expanded pile.
In addition, since the pile has a downward taper, the downward frictional resistance can be reduced to a fraction of that in the ground where negative frictional resistance is generated, and the maximum for positive frictional force. A friction resistance of several tens% can be expected. The taper allows the pile diameter to be substantially shaped according to the generated stress, so that the amount of concrete in the pile, the amount of excavated earth and sand, and the residual soil (industrial waste) can be reduced.
To inject cement milk, etc., because it can be continuously injected through a Keribar pipe or drill pipe without using special equipment and without pulling out a drill bit to inject cement milk, etc. Required time can be minimized.
In the drilling by the reverse excavator, the final slime treatment of the hole bottom is performed after excavation to the bottom of the pile, usually for about 20 to 30 minutes, waiting for the settling of the soil particles in the stabilizing liquid. Time can be saved.
After performing slime treatment on the bottom of the hole, the slime that settled at the bottom of the hole before raising the drill bit, setting up the reinforcing steel, and setting up the tremy pipe accumulates on the surface due to the difference in specific gravity. Can be removed by a slime treatment using a tore tube.
Also, if some slime remains or slime accumulated during the subsequent casting of concrete, the slime is pushed up to the ground while being deposited on the surface of the concrete. In particular, in the tapered pile, the diameter increases as it goes above the drilled hole, so that the slime rises smoothly and adheres little between the hole wall surface and the concrete, so that a decrease in the supporting force can be suppressed.
According to the construction method of the present invention, a cast-in-place pile excellent in quality and economy can be constructed in a short time by the above-described actions and effects.

Next, in the method for constructing a cast-in-place pile according to claim 5, an excavation shape measured from an opening / closing angle of the excavation bit by attaching a sound wave transmitter / receiver for excavation shape measurement to an excavation bit of a reverse excavator capable of expansion and contraction. Using a digging shape measurement system configured to be able to simultaneously detect the digging shape measured from the sound wave transceiver and the sonic transmitter / receiver, the shape of the cast-in-place pile is measured when the digging bit is pulled up.
In the method of constructing a cast-in-place pile according to the present invention, a drilling shape inspection measuring instrument is attached to the drilling bit portion, and the shape inspection is performed when the drilling bit is lifted to the ground. There is no need to install a shape inspection and measurement device on the ground to measure from the ground. In addition, since the transmitter / receiver is attached to the heavy excavation bit, the measurement time can be greatly reduced because it is hardly affected by the fluctuation of the stable liquid after the excavation. It is hardly received and an accurate shape inspection can be performed. Further, since the measured shape value and the measured shape value obtained from the opening / closing angle of the drill bit can be compared on the monitor screen, a more reliable measured value can be obtained.

The method of constructing a cast-in-place pile according to claim 6, wherein a spiral jig is attached to at least a part of an outer surface of a stand pipe, a casing pipe or an outer shell steel pipe, and the pipe or the steel pipe is drilled by a reverse excavator or an earth drill. It is characterized in that it penetrates using the rotational force of the drive shaft of the machine.
In this method of casting cast-in-place piles, in the conventional construction of cast-in-place piles, machines dedicated to the work, such as power jacks, vibratory hammers, and cranes, are used to install and remove stand pipes, casing pipes, or outer steel pipes. Although it was necessary, in the method for constructing a cast-in-place pile according to the present invention, a base machine used for an excavator is used to install and remove a standpipe, etc. Is obtained.

The method of constructing a cast-in-place pile according to claim 7 is a method of constructing a cast-in-place cast-in-place pile using an earth drill excavator or a reverse excavator, following the slime treatment after excavation, the hollow drive shaft of the excavator. Inject cement milk etc. into the hole bottom from the very tip through the top, then build reinforced slime on the cement milk etc., and then use a pump or air lift on the ground via a tremy pipe for concrete placement. It is characterized by being collected.
In this casting method of cast-in-place pile, by injecting cement milk etc. into the bottom of the hole immediately after excavation, slime is prevented from accumulating on the ground at the tip of the pile, and the slime treatment performed immediately before placing concrete is effective. Therefore, the pile quality can be improved, such as securing pile support capacity and preventing uneven settlement.

  In the construction method of the cast-in-place pile according to claim 7, cement milk or the like may be directly poured into the expanded bottom using a hose of a concrete pump truck instead of the tremy tube.

  The construction method of the cast-in-place pile according to the ninth aspect is characterized in that a spiral jig is attached to at least a part of the outer shell steel pipe also serving as the casing. In this casting method of cast-in-place piles, the outer shell steel pipe may be a tapered steel pipe that tapers downward.

  According to the present invention, it is possible to provide a cast-in-place pile which is advantageous against a vertical load, a horizontal load, and a negative frictional force, and to provide a cast-in-place pile having a certain quality and economy.

  Hereinafter, the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The method of constructing the cast-in-place pile of the present invention is, in principle, performed using the reverse method or the earth drill method.For example, in the final excavation stage of the Venoto method, the expanded pile is constructed using a drill bucket with an enlarged bit. It is also applicable to the case.

<About the shape of the pile>
FIG. 1 illustrates a typical shape of a tapered expanded pile to which the present invention is applied.
1 (a), 1 (b) and 1 (c) each have a straight portion at the pile head and a tapered portion at the lower portion. The pile head is a straight part where the section force of the pile increases. To counter this, the section rigidity is secured, and a stand pipe is used during construction. There is also a factor. In the future, if tapered steel pipes are commercialized, the construction of piles formed in a tapered shape from the pile heads may become popular.

In FIG. 1A, a straight portion is provided below the tapered portion, and an enlarged bottom portion is connected to the lower portion. The reason why the straight portion is provided below the tapered portion is that there is a limit to the maximum length of the tapered portion, and it is necessary to provide the straight portion also at the lower portion when the pile length is long. The practical gradient of the tapered portion is considered to be 1 to 2%, and the maximum length of the tapered portion based on this gradient is approximately 20 to 30 m depending on the pile diameter. The steeper the slope of the tapered portion, the larger the positive frictional resistance and the smaller the negative frictional resistance, but the length of the tapered portion is reduced accordingly.
It is desirable that the section where the negative frictional resistance acts on the pile due to the consolidation settlement of the soft layer be tapered as much as possible. However, when the section becomes long, it is necessary to increase the diameter of the pile head straight portion to some extent. FIG. 1C shows the shape of a pile designed as an earthquake-resistant cast-in-place pile, in which an outer shell steel pipe is provided at the top and also serves as a standpipe. Spiral wings, that is, spiral guides, can be attached to the outer shell steel pipe, and the effect is great if the ground conditions allow the screw to be screwed in with the torque of the driving shaft of the excavator.

Such a tapered expanded pile has the following advantages.
By increasing the diameter of the pile head and the pile tip, it is possible to effectively secure the horizontal support force and the vertical support force. Since economical design can be performed for the section force generated in the pile, the number of materials can be reduced. By providing the tapered part, it is larger if the part is positive frictional resistance and smaller if it is negative frictional force, so it is more applicable even when the ground is complicated, compared to straight piles The peripheral frictional resistance can be largely estimated. By using the expanded bottom pile, the ratio of the tip support force, which is more reliable than the peripheral friction force, can be increased, and the influence of negative friction resistance can be reduced. The problems in the construction of the tapered expanded pile are almost the same as those of the straight pile normally used.

<About frictional resistance acting on tapered pile>
FIG. 2 schematically shows the relationship between the frictional resistance generated on the peripheral surface of the pile and the relative displacement between the pile and the ground. It is known that the frictional resistance generated around the pile as shown in this figure increases with the relative displacement at least up to the maximum value. Further, it is said that the positive frictional resistance at the same relative displacement is larger than the negative frictional resistance. This can be proved by performing a vertical load test and a pull-out load test on the same pile with a strain gauge attached, depending on the ground conditions and the like. This is also disclosed in Tertuagi's "Soil Mechanics". As shown in the figure, the tapered pile has a higher friction resistance in the positive friction region and a smaller friction resistance in the negative friction region as compared with the straight pile. By designing the shape of the pile in consideration of this phenomenon and the sectional force of the pile, it is possible to perform an economical and highly reliable design. Further, when it is unclear whether a specific soil layer will be a positive friction resistance section or a negative friction resistance section in the future, a tapered section can be used to obtain a reasonable pile shape.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. First, a method of implementing the present invention using a reverse excavator will be described.

<1. Drilling equipment>
First, the configuration and function of a pile excavator will be described. FIG. 3 is a diagram showing a drilling situation. In FIG. 3, the drill pipe 10 extends from the ground to the inside of the drill hole 1, a drill unit 20 is connected to a lower end 10a of the drill pipe 10, and a driving device 30 is connected to an upper end 10b protruding above the ground. ing. The excavation hole 1 is provided with a stand pipe 2 at an upper end, a shaft portion 3 formed in a tapered shape below the excavation hole, and an excavated bottom portion 4 excavated further below the excavation hole 1. The stable liquid 5 is filled to prevent the collapse of the hole wall 3a.

  Here, the drill pipe 10 is formed by connecting a plurality of hollow pipes.

  As shown in FIG. 4, the excavating unit 20 has a joint flange 21a at an upper end of a hollow drive shaft 21 and an opening 21b at a lower end, and a fish tail 22a is fixed around the opening 21b. The opening 21b is used not only as a suction port for muddy water in the borehole, but also as a discharge port for cement milk or the like. A shaft bit 22b is fixed to the lower end of the hollow drive shaft 21. A hole 22c is pivotally attached to the shaft bit 22b. The hole 22c is pivotally attached to the lower crosshead 24a by a link member 23. . The lower crosshead 24 a is mounted near the lower end of the hollow drive shaft 21 so as to be able to move up and down along the hollow drive shaft 21. The lower crosshead 24a is connected to the upper crosshead 24c by a hydraulic jack 24b, and the upper crosshead 24c is fixed to the hollow drive shaft 21. Therefore, when the hydraulic jack 24b is extended, the hole-expanding bit 22c opens and expands as depicted by a solid line in FIG. 4, and conversely, when the hydraulic jack 24b is contracted, the hole-expanding bit 22c extends as depicted by a dotted line. Close and shrink. The force for pressing the excavating unit 20 against the ground is obtained by adjusting the lifting force of the crane that suspends the excavating unit 20 and applying the optimum amount of the own weight of the excavating unit 20 to the ground.

The excavating unit 20 is provided with a hole opening bit opening / closing amount detector 25, an ultrasonic shape detector 26, and a stabilizer 27 in addition to the above-described configuration. Inside the stabilizer 27, a hydraulic unit 28a and a measuring device 28b are provided. The cable 29 is extended from the measuring device 28b to the ground. The data from the measuring device 28b may be sent to the ground by radio instead of the cable 29.
The hole opening bit opening / closing amount detector 25 detects the opening / closing amount of the hole opening bit 24 by detecting the position of the lower cross head 22. The ultrasonic shape detector 26 transmits an ultrasonic wave from here to the hole wall and detects a reflected wave thereof, thereby detecting the shape of the drilling hole, and also has a transmitting / receiving function. The stabilizer 27 has a circular shape adapted to the drilling diameter, rotates together with the drill pipe 10 in the drilling hole, and guides the drilling axis so as not to shift. In this embodiment, the diameter of the stabilizer 27 is set in accordance with the minimum drilling diameter of the shaft portion. However, the diameter can be changed using a hydraulic cylinder (not shown).

The driving device 30 shown in FIG. 3 is connected to the upper end 10 b of the drill pipe 10 to provide a driving force, a rotary joint 32 to cut off rotation, and transmit the driving force to the kelly bar pipe 31. And a rotary table 33.
A swivel 34 is connected to the rotary joint 32, and a delivery hose 35 is connected to the swivel 34. The delivery hose 35 extends to a suction pump (not shown). The cutting soil cut by the shaft bit 22b and the hole-expanding bit 22c is sucked up by the suction pump together with the stabilizing liquid through the foremost opening 21b (suction port) of the hollow drive shaft 21 by the suction pump and discharged to the ground. Is done. The sediment and the stabilizing liquid are separated in a sedimentation tank (not shown) on the ground, and the stabilizing liquid is returned into the hole again.
As described above, the stable liquid in the hole carries out the cutting earth and sand to the ground while circulating between the hole and the ground. By the circulation of the stabilizing solution, mud cake as a water barrier film is generated on the hole wall. In addition to the water blocking film and the stand pipe 2, the water level in the hole maintained at a height of 2 m higher than the groundwater level exerts a hydrostatic pressure of 20 kPa on the hole wall, whereby the hole wall is maintained during excavation.
Further, the swivel 34 is provided with an injection pipe 36a for cement milk or the like together with the opening / closing valve 36b. With this, cement milk or the like is fed from the injection pipe 36a while the suction of the stable liquid is stopped, and the drill pipe 10 Through the opening 21b (discharge port) of the excavation unit 20.

  When the straight portion of the pile is excavated by the excavating unit 20 having the above-described configuration, the opening / closing angle of the hole-expanding bit 22c is adjusted so that the hydraulic pump 28a housed in the stabilizer 27 is moved from the ground to the display unit so as to have a predetermined hole diameter. Operation is performed while looking at the screen, and excavation is performed to a predetermined depth while keeping the opening and closing angle constant. The same applies to the case of excavating the tapered portion 3 and the expanded bottom portion 4. The opening and closing angle of the expanded bit 22 c is adjusted by operating the hydraulic pump 28 a on the ground so as to excavate the same shape while viewing the design shape on the screen of the display unit. I will do it. This operation can be performed automatically by configuring an electric circuit. When pulling up the excavating unit 20, the drilling bit 22c is pulled up in a state where it is maximally folded. In this embodiment, the hydraulic pump 28a serving as a power source for opening and closing the hole expanding bit 22c is housed in the stabilizer 27. However, this is a processing and curing of a hydraulic hose that occurs when the hydraulic hose is installed on the ground. This is to eliminate work and avoid problems as much as possible. A power supply and a control cable for the hydraulic pump 28a are wired to the ground along the drill pipe 10 and connected to a power supply and a controller installed on the ground via a slip ring (not shown) integrated with the rotary joint 32. Is done.

FIGS. 5A and 5B illustrate another excavating unit 40 used for a reverse excavator. In this excavating unit 40, an inner shaft 42 is slidably inserted into a pipe of an outer shaft 41. A flange joint 42a is provided at an upper end of the inner shaft 42, and a drive motor 42b and a worm gear 42c are provided below the inner joint 42. A connecting rod 43 is pivotally connected to a crosshead 42d formed near the upper end of the inner shaft 42. A hole 44 is pivotally attached to the lower end of the connecting rod 43. The hole-expanding bit 44 is formed so as to be slidable along a slide guide 45 protruding in the axial direction of the outer shaft 41 to a shaft bit 46 at the lower end. A stabilizer 47 is provided at an upper end of the outer shaft 41, and an opening 41a is provided at a lower end. The opening 41a is used as a suction port for muddy water in a drilling hole and a discharge port for cement milk and the like, and a fish tail 48 is protruded around the opening 41a. An ultrasonic shape detector 49 is provided near the lower end of the outer shaft 41.
In the excavating unit 40 having the above-described configuration, the hole-expanding bit 44 suspended from the inner shaft 42 by the connecting rod 43 slides on the inclined slide guide 45 by the drive motor 42b and the worm gear 42c, so that the hole-expanding bit 44 is Zoom in and out. FIG. 5A shows a state where the diameter of the excavation unit 40 is the smallest, and FIG. 5B shows a state where the diameter is the largest. The operation of the drilling bit 44 of the excavation unit 40 can be performed while watching the CRT screen by the above-mentioned management device on the ground, similarly.

<2. Measurement management device>
Next, a configuration of a measuring instrument for excavating a pile into a predetermined shape will be described.
FIG. 6 is a flowchart of the measurement system. A signal from each detector is sent to a computer via an A / D converter and processed, and the result is compared with a design value and displayed one by one. The excavation depth displacement meter measures the protruding length of the above-ground Keribar pipe 31 with a measurement wire and an encoder 6 as shown in FIG. In the drill pipe 10b connected to the lower part of the caber pipe 31, each hollow pipe constituting the drill pipe 10b is added according to the progress of the drilling. Change the total. The computer calculates this information and displays it on the display unit. The hole opening bit opening / closing amount displacement meter measures the opening / closing angle of the hole expanding bit 22c by measuring the expansion / contraction amount of the stabilizer 27 fixed to the hollow drive shaft 21 and the lower crosshead 24a sliding on the hollow drive shaft 21. belongs to. The drill pipe inclinometer of FIG. 6 is for measuring the verticality of the hollow drive shaft 21 of the drilling unit 20, and the data on the verticality is obtained when the hole is bent at the time of drilling or when the drilling unit 20 is pulled up. It is combined with the data of the hole wall shape measurement and used as data for detecting hole bending after excavation.
In order to confirm the shape of the drilling hole, the shape of the drilling hole is recorded when the drilling bit is pulled up by the ultrasonic shape detectors 26 attached in four directions of the drilling unit 20 as shown in FIG. The electric signal of the ultrasonic shape detector 26 is once sent to a measuring unit in the stabilizer, and then sent to the ground by cable or wireless, and finally processed together with a stroke meter or the like on a display unit via a computer. indicate. The same applies to the case where the excavating unit 40 of FIG. 5 is used.
The measurement data thus recorded are all collected in a recording unit of a computer, and are calculated, processed, and displayed on a display unit as appropriate. The crane operator or the manager operates the drill hole having a predetermined shape while transmitting the information to other workers while watching the display on the screen.

<3. Construction method>
7 and 8 are a diagram showing a construction order and a diagram showing a construction outline in the present embodiment, respectively. Among these steps, the characteristic steps in the present invention are the steps (4) and (6). The other steps are almost the same as those of the ordinary reverse type cast-in-place pile. The construction procedure of the tapered expanded pile according to the present invention will be described with reference to FIGS.
Here, the conventional reverse excavator is used from the installation of the stand pipe in the process (1) to the installation of the reverse excavator in the process (3), and from the removal of the reverse machine in the process (9) to the removal of the stand pipe in the process (14). Since the method is almost the same as the method of constructing a cast-in-place pile according to the method described in FIGS.

(4) Process Shaft excavation Excavation of the straight section where the pile diameter does not change is the same as the conventional method. With the expansion width of the hole expansion bit kept constant, a rotational force is applied to the kelly bar pipe 31 to rotate the excavation unit 20 and cut the ground. The cut earth and sand is discharged to the ground together with the stabilizing liquid from the suction port. The state of excavation can be observed on the screen of the display unit. If the inclination angle of the inclinometer attached to the excavation unit 20 is large, it is considered that the thrust on the bit is too large. . In excavation of the tapered portion, the solenoid valve of the hydraulic pump is operated while controlling the opening / closing amount of the hole expanding bit and watching the screen of the display unit so as to have a predetermined diameter. When the drilling of one hollow pipe (almost 3 m) constituting the drill pipe 10 is completed in this way, the kelly bar pipe 31 and the drill pipe 10b thereunder are cut off, and a new hollow pipe is added therebetween. At this time, the power cable and the measurement signal cable temporarily fixed to the drill pipe 10 are also extended and temporarily fixed again. In addition, the displacement meter for the excavation depth is replaced and adjusted so as to have a predetermined depth.

(5) Process of excavation of bottom portion When the excavation of the shaft of the pile reaches a predetermined depth, the excavation process of the extension portion is continued. During the excavation of the expanded bottom portion, the pipe length is selected so that the hollow pipe does not rejoin the drill pipe 10. Excavation is performed while operating the solenoid valve of the hydraulic pump so as to have a design shape on the screen of the display unit as in the case of the taper unit. Excavation is completed when the lower end of the maximum bottom reaches a predetermined depth. However, in order to almost completely remove the cutting waste accumulated at the bottom of the hole, the excavator is further rotated for about 10 to 20 minutes to perform the slime treatment. At this time, the drill bit and the shaft bit are pulled up to such a state that they do not come into contact with the ground. After confirming that the stable liquid discharged to the ground is free of debris and slime, stop the excavator completely.

(6) (7) Process Injection of cement milk etc. at the bottom of the bottom After the slime treatment in the excavation hole was performed in the previous process, preparation work was performed on the ground for injection of cement milk etc., and after the excavator stopped The cement milk or the like is quickly injected through the injection pipe 36a of the cement milk or the like branched from the swivel 34. The injection amount is set at least at the rising portion 4a of the expanded bottom portion 4 or more. At this time, the excavation unit 20 is stopped in principle.
When cement milk or the like is injected into the entire expanded bottom portion 4, it must be sufficiently considered that the reinforcing rod cage can be installed to a predetermined depth in a later process. When cement milk or the like is previously filled in the entire expanded bottom portion 4 in this way, there is a feature that the treatment of the slime on the outer periphery of the reinforcing bar cage becomes easier. In addition, when the injection amount to the tip is large or when concrete is poured, the swivel 31 can be removed and the drill pipe 10 can be directly used instead of the tremy pipe.
As shown in the step (7), a part of the side wall portion of the expanded bottom portion 4 is left, cement milk or the like is injected, and then the excavated earth and sand during the second excavation and the cement milk are stirred and mixed, and a part of the pile body of the expanded bottom portion 4 It is good. However, in this case, it may be considered that the soil layer of the expanded bottom 4 is sandy ground.

(8) Process Drilling Unit Pulling Up and Excavation Shape Inspection The drilling unit 20 is pulled up with the hole expansion bit contracted to a minimum and in a vertical position. This is to prevent the hole-expanding bit from contacting the hole wall and to prevent damage to the hole wall, and to perform accurate pile shape measurement. For this reason, when pulling up the drill pipe 10, attention should be paid to how to attach the mounting wire, and the drill pipe 10 should be pulled up slowly at a constant speed.

<About reinforcing bars>
The reinforcing bar cage 7 in the tapered portion is formed by arranging axial reinforcing bars in a tapered shape or by combining, for example, straight reinforcing bar cages in a stepwise manner.

In a second embodiment, a method of implementing the present invention using an earth drill excavator will be described. Note that the same parts as those in the first embodiment will be omitted.

<1. Drilling equipment>
FIG. 9 illustrates an earth drill excavator 50 with a widening bit, which is a conventional device, but a swivel 52 and a cement milk injection pipe 53 on the upper part of a kelly bar pipe 51 shown in this figure are equipment unique to the present invention. is there. The structure of the excavating bucket 54 with a hole expanding bit is, for example, that shown in FIG. 20 of Japanese Patent Application Laid-Open No. 58-222287. That is, by rotating the excavating bucket 54 while pushing a part of the side of the excavating bucket 54 outward by the hydraulic cylinder, a function of performing not only excavation of the bottom but also excavation of the side at the same time is provided. Therefore, in order to excavate the tapered portion of the pile, the opening and closing amount of the hole expanding bit may be selected according to the depth. From this, the function newly added in order to carry out the present invention only needs to add a device capable of discharging the cement milk from the tip of the excavation bucket 54 using the hollow portion of the keliver pipe 51.
As a configuration other than the above, a rotary drive unit 55 is provided at a lower end of the kelly bar pipe 51, and a rotary joint 56, a reel 57 for a cable hose, and a stabilizer 58 are further provided below.

<2. Measurement management device>
Since a commercially available earth drill excavator 50 as shown in FIG. 9 is equipped with a measurement management device capable of managing the drilling depth and the amount of drilling of the drilling bit at the driver's seat, this device is also used in the present invention. Construction management is possible.

<3. Construction method>
FIG. 10 and FIG. 11 are a flowchart showing the construction order in the present embodiment and a schematic diagram of the construction, respectively. Among these steps, the characteristic steps of the present invention are the step (4) of forming and excavating the tapered portion, and the step (7) of expanding the bottom slime and injecting the cement milk. The other steps are almost the same as the construction method of the cast-in-place cast-in-place pile using an ordinary earth drill excavator.
The procedure for constructing the tapered expanded pile according to the present invention will be described with reference to FIGS. 10 and 11. The numbers (1) to (14) of the steps in both FIGS. 10 and 11 denote the same steps with the same numbers. Hereinafter, description will be made focusing on the (4) process of shaping and excavating the tapered portion, which is a characteristic process of the present invention, and the slime treatment and cement milk injection operation of the (7) process.

(4) Process Taper Shaped Excavation Excavation of the tapered portion can be performed by adjusting the opening / closing amount of the drilling bit according to the pile diameter at the drilling position every time the drilling bucket 54 is carried in / out of the hole. Although good, this method is inefficient and the accuracy of the shape of the tapered portion is also poor. When the accuracy of the tapered portion is poor and the pile surface has irregularities, the frictional resistance at that portion increases. This may be preferable when a positive frictional resistance is obtained, but is not preferable when a negative frictional resistance is generated.
Therefore, as for the excavation of the tapered portion, as in the step (3) shown in FIG. 11A, a certain section is excavated with the same diameter as the straight portion. Then, after drilling 5 m, for example, the drilling bucket 54 is returned to the excavation start height in the section, and the shaping excavation is continuously performed in a tapered shape while adjusting the opening and closing amount so as to close the hole expanding bit. If the excavation is carried out continuously for a long section, mud film adhering to the hole wall in that section may be temporarily lost, which may lead to collapse of the hole wall. Must be set. A series of drilling conditions can be observed on the screen of the display unit in the driver's seat.
In the step (4), the earth drill excavator 50 shown in FIG. 9 is used. In this earth drill excavator 50, since the kelly bar pipe 51 is a multi-stage telescopic system, the kelly bar pipe 51 is connected on the way.・ Excavation of 40m or more is possible without separation.

(5) Process Excavation at the bottom When the excavation of the shaft of the pile reaches a predetermined depth, the excavation at the bottom 4 is started. Similarly to the tapered portion 3, the operator excavates while operating the solenoid valve of the hydraulic pump so as to have a design shape while looking at the screen of the display portion. Excavation is complete when the lower end of the maximum bottom reaches a predetermined depth.

(7) Process Injection of cement milk at the bottom of the bottom Even if the excavation to the specified depth is completed, cutting waste and slime settle at the bottom of the hole, and the specific gravity of the stable liquid in this part may exceed 1.2. . Since such high-density muddy water has an adverse effect on the concrete placement, the muddy water is pumped up and discharged by the excavation bucket 54. Dedicated buckets may be used for slime disposal after excavation. In any case, the state of the muddy water discharged at the final stage is confirmed, and the slime processing is terminated. Since it is not efficient to discharge high-concentration muddy water with a bucket, it is desirable to discharge the muddy water with a hollow part of the kelly bar 51 using an air lift, a suction pump, a submersible pump, or the like.
At the time of slime treatment in the previous step, preparation work for cement milk injection is performed on the ground, and at the end of slime treatment, the cement milk injection pipe 53 of the keribar pipe 51 is kept in a state where the excavation bucket 54 is almost in contact with the bottom of the hole. And immediately inject cement milk into the hole bottom. The injection amount is set to be at least equal to the expanded rising portion (see FIG. 13A). At this time, the rotation of the excavating bucket 54 is stopped in principle, and is gradually raised in accordance with the injection height of the cement milk.

(8) Process Excavation Shape Inspection The earth drill excavator 50 exemplified as described above is equipped with a device for recording the opening / closing amount of the drilling bit at the time of excavation and a depth gauge, and utilizes data at that time. It can be replaced with the shape inspection result.

Next, a third embodiment will be described. Here, the construction of stand pipes, casing pipes or outer shell steel pipes (hereinafter simply referred to as “steel pipes”) that can be used in the method of constructing cast-in-place piles, and the driving shafts of reverse drills and earth drill drills A method of implementing the method will be described.
FIG. 12 shows the configuration of the steel pipe 60, in which a spiral guide 62 is fixed near the tip of the steel pipe body 61. The spiral guide 62 functions to guide the steel pipe 60 into the ground when the steel pipe 60 is rotated while applying pressure. The spiral guide 62 is formed by attaching an iron plate or round steel to the steel pipe main body 61 by welding. A detachable cap 63 is attached to the head of the steel pipe main body 61. The cap 63 and the steel pipe main body 61 are mutually restrained by a lock pin 64 and a rotation locking jig 65. Further, a hinge joint 66 for connecting to a drive shaft 67 (a kelly bar pipe or a drill lot) of the excavator is provided on an upper lid of the cap 63. By using the hinge joint 66 in this manner, the steel pipe 60 can be connected even when the steel pipe 60 is placed horizontally, so that an efficient hanging operation becomes possible.
Next, a method of installing the steel pipe 60 will be described. If the ground is soft, it is possible to screw the steel pipe 60 directly with the torque of the drive shaft 67 of the excavator in the state shown in the figure, but if the surface ground is hard or the steel pipe 60 is long, A hole is drilled to a depth of several meters, and a steel pipe 60 is built in the hole and screwed as it is, or when the torque of the excavator is insufficient, the steel pipe 60 is sunk to a predetermined depth while also using internal excavation. When pulling out the steel pipe 60, the drive shaft of the excavator may be reversed while applying a tensile force.

Fourth Embodiment With reference to FIGS. 13A to 13D, a method for preventing slime from depositing on a pile tip at the time of cast-in-place pile construction will be described in a fourth embodiment. Slime treatment of large-diameter cast-in-place piles is usually performed twice immediately after excavation and immediately before placing concrete. However, soil particles floating in the stabilizing liquid settle to the bottom of the hole with the passage of time, and during work inside the hole after excavation, equipment and reinforced cages come into contact with the hole wall and some soil mass falls. The fact is that things cannot be avoided. For this reason, as shown in FIG. 13D, slime is collected using the tremy pipe 70 immediately before placing concrete, but slime collected around the reinforcing rod cage 71 and the hole bottom 72 on the outer periphery thereof. It is difficult to sufficiently recover 73.
The present invention proposes a method capable of performing a sufficient slime treatment also on the outer periphery of a reinforcing bar cage. Therefore, as described in the first and third embodiments, it is necessary to inject cement milk into the hole bottom using the hollow drive shaft of the excavator immediately after the primary slime treatment. The process of collecting the excavator, inspecting the excavation shape, building the reinforced cage, and installing the tremy tube requires several hours, during which time new slime is deposited at the bottom of the hole. Since the slime slowly settles in the stabilizing solution, as shown in FIG. 13 (a), by injecting the cement milk 74 into the bottom of the hole in advance, the slime 75 is converted into the cement milk by the difference in specific gravity and the surface tension. 74 is deposited on the surface. The slime 75 is sucked and collected together with the stabilizing liquid 76 and the cement milk 74 by a submersible pump or the like connected to the tremy tube 70. The slime separated from the tremee pipe 70 is also sucked into the tremee pipe 70 on the cement milk and can be collected on the ground. Therefore, after the slime is treated, the outer periphery 77 of the rebar basket 71 as shown in FIG. But you can have no slime. More preferably, as shown in FIG. 13 (c), the slime 78a remaining at the start of concrete casting starts because the tip of the tremee pipe at the start of concrete placement is located inside cement milk or the like. Rises in a state of being deposited on the surface of a cement mixture such as cement milk or concrete, so that the adverse effect of slime can be extremely reduced.
In order to avoid separation of the cement milk over time, it is possible to add an admixture such as an antiseparation agent or a fluidizing agent. It is also possible to mix fly ash and coal ash to save cement.

(a), (b), and (c) illustrate the shape of the tapered expanded pile to which the present invention is applied. It is the figure which showed the relationship between the frictional resistance of a pile peripheral surface, and the relative displacement of a pile and the ground. It is a figure which shows the drilling situation in the construction method of the cast-in-place pile of this invention. It is a figure which shows the excavation unit used for the construction method of the cast-in-place pile of this invention. (a) (b) is a figure which shows another excavation unit used for a reverse excavator. It is a flow figure of the measurement system used for the construction method of the cast-in-place pile of the present invention. It is a flowchart which shows the construction order in an Example. It is a figure showing the construction outline in an example. It is the figure which added the equipment peculiar to this invention to the conventional earth drill excavator. It is a flowchart which shows the construction order in a present Example. It is a figure showing the outline of construction in this example. Fig. 3 shows a configuration of a steel pipe. (a)-(d) is a figure explaining the slime sedimentation prevention method in a pile lower end.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Drilling hole 2 Stand pipe 3 Shaft 4 Expansion bottom 5 Stabilizing liquid 10 Drill pipe 20 Drilling unit 21 Hollow drive shaft 22b Shaft bit 22c Expansion bit 25 Expansion bit opening / closing amount detector 26 Ultrasonic shape detector 29 Cable 30 Drive device 31 Kelly bar pipe 40 Drilling unit 49 Ultrasonic shape detector 44 Drilling bit 46 Shaft bit 50 Earth drill excavator 51 Kelly bar pipe 54 Drilling bucket 55 Rotation drive unit 60 Steel pipe (stand pipe, casing pipe or outer shell steel pipe)
62 Spiral Guide

Claims (10)

  In the construction method of the cast-in-place pile having a tapered portion tapering downward at least at a part of the shaft portion of the expanded pile, the excavation shape becomes a predetermined value on the monitoring screen based on the opening / closing state of the excavation bit of the reverse excavator that can be expanded / contracted. After drilling from the pile shaft to the bottom of the tip using a controllable system, the cement milk, mortar or cement mixture is partially or entirely removed from the tip of the drill bit through the drill pipe of the reverse drilling machine. After raising the excavation bit of the reverse excavator to the ground, building a reinforcing rod cage in the excavation hole, casting concrete using tremy pipe to create a pile body Construction method of cast-in-place pile.   In the construction method of the cast-in-place pile having a tapered portion tapering downward at least at a part of the shaft portion of the expanded pile, the excavation shape becomes a predetermined value on the monitoring screen based on the opening / closing state of the excavation bit of the reverse excavator that can be expanded / contracted. After excavating the shaft part of the pile using a system that can be controlled as described above, when excavating the expanded bottom part, once a part of the expanded bottom diameter is once smaller than the predetermined diameter, after the primary excavation to almost the final depth, Inject cement milk, mortar, or cement mixture from the drill bit tip to the expanded bottom through the drill pipe of the reverse excavator, and then perform secondary drilling while operating the drill bit so that the expanded bottom has a predetermined shape. At the same time, after the cement milk, mortar or cement mixture and the excavated soil are mixed with stirring, the excavating bit of the reverse excavator is pulled up to the ground, and the rebar cage is installed in the excavation hole, Method of applying place pile, characterized in that performing the pouring of concrete using chromatography tube to construct a pile body.   In the method of constructing a cast-in-place pile having a tapered portion that tapers downward in at least a part of the shaft portion of the expanded bottom pile, the excavation shape is set to a predetermined value on the monitoring screen from the enlargement state of the excavation bucket of the expandable earth drill excavator. After drilling from the shaft to the bottom of the final depth using a controllable system and slime treatment at the bottom of the hole, a part of the bottom from the tip of the drill bucket through the keribar pipe of the earth drilling machine Or inject cement milk, mortar or cement mixture into all, pull up the drilling bucket of the excavator to the ground, then build a reinforced cage in the drilling hole, cast concrete using tremy pipe A method for constructing a cast-in-place pile, characterized by forming a pile body.   In the construction method of the cast-in-place pile having a tapered part tapering downward in at least a part of the shaft part of the expanded bottom pile, the excavation shape becomes a predetermined value on the monitoring screen based on the open / close state of the expandable expandable bucket of the earth drill excavator. After excavation of the shaft part using a system that can be controlled to be as follows, in the excavation stage of the expanded bottom part, a part of the expanded bottom diameter was once smaller than a predetermined diameter, and the first excavation was performed to approximately the final depth. After that, cement milk, mortar or cement mixture is injected from the tip of the enlarged bucket to the expanded bottom through the kelly bar of the earth drill excavator, and then the secondary drilling is performed while operating the drill bit so that the expanded bottom has a predetermined shape. While mixing and mixing the cement milk, mortar or cement mixture with the excavated soil, and then pulling up the enlarged bit of the earth drilling excavator to the ground, and introducing iron into the drill hole. Method of applying place pile, characterized in that the basket Kenkomi, perform pouring of concrete using tremie pipe to construct a pile body.   An excavator that attaches a sonic transmitter / receiver for measuring the digging shape to the digging bit of a scalable reverse excavator so that the digging shape measured from the opening / closing angle of the digging bit and the digging shape measured from the sonic transmitter / receiver can be detected simultaneously. A method for constructing a cast-in-place pile, wherein the shape of the constructed cast-in-place pile is measured when the drill bit is pulled up using a shape measuring system.   A helical jig is attached to at least a part of the outer surface of the stand pipe, the casing pipe or the outer shell steel pipe, and the pipe or the steel pipe is penetrated by using the rotational force of the drive shaft of the reverse drill or the earth drill drill. Characteristic cast-in-place pile construction method.   In the method of constructing a cast-in-place cast-in-place pile using an earth drill excavator or reverse excavator, following the slime treatment after excavation, cement milk, mortar or cement mixture from the tip of the excavator to the hole bottom through the hollow drive shaft. After that, slime deposited on cement milk, mortar or cement mixture is built into a steel cage, and then collected on the ground by a pump or air lift through a tremy pipe for placing concrete. Construction method of pile driving.   8. The method according to claim 7, wherein a cement mixture containing cement such as cement milk is directly poured into the expanded bottom using a hose of a concrete pump truck instead of the tremy tube.   A cast-in-place pile in which a spiral jig is attached to at least a part of an outer shell steel pipe also serving as a casing.   10. The cast-in-place pile according to claim 9, wherein the outer shell steel pipe is a tapered steel pipe tapering downward.

Images