JP4797147B2 - Column replacement construction method and column replacement - Google Patents

Description

  The present invention relates to a column replacement construction method and a replacement column as a foundation method for civil engineering and building structures.

As a basic construction method for civil engineering and building structures, a deep mixing method, a fluidized earth method, a PIP pile method, an RG pile method, and the like have been proposed.
The deep mixing treatment method is a method of constructing a cylindrical ground improvement body in the ground by inserting an excavation stirring mixing device into the ground and mixing with the original ground at the same time while filling the solidified material (for example, patent There are a method of filling the solidified material when the excavating and stirring mixing device is dug into the ground, and a method of filling the solidified material when it is pulled upward. Moreover, there are a method of using the solidified material in a slurry form by stirring and mixing with water, and a method of using the solidified material in powder form.
The fluidized earth method is to improve the ground by mixing the earth and sand excavated with a continuous spiral auger with solidified material with a ground mixer to make soil cement, and then returning the soil cement to the place where it was excavated again. (For example, see Patent Documents 2 and 3).
In the PIP pile method, a driving device is attached to the head of a hollow shaft of an auger with continuous flights, the entire device is suspended on a fence, excavated to a predetermined depth while rotating in the ground, a predetermined depth Is reached, a mortar pile is formed by gradually pulling up the mortar from the shaft tip, and immediately after the auger is pulled up, a reinforcing bar or a shaped steel is built into the mortar pile (for example, Patent Document 4 and Non-patent document 1).
In the RG pile method, the earth auger with a hollow shaft rotates to excavate the earth and sand up to a predetermined depth, and then the auger is pulled up and mortar is injected from the outlet of the hollow shaft auger head. A cast-in-place pile is created in the ground (see, for example, Non-Patent Document 1).
JP 2003-247228 A (Claim 3, 0002) JP-A-8-260450 (Claim 1) Japanese Patent No. 3280710 (Claim 1) Japanese Patent No. 3306460 (0002) Underground continuous wall construction method design and construction handbook Japan Construction Mechanization Association published by Gihodo Publishing Co., Ltd. (pages 427-430)

The above-mentioned deep mixing treatment method has the following problems.
(1) Because it is a construction method to build a ground improvement body in the ground by mixing and stirring with the original ground at the same time while filling the solidified material, the soil structure and physical properties of the ground to be improved are not constant. The quality of the improved soil has the disadvantage that the uniaxial compressive strength varies greatly. Therefore, the target strength to be improved has to be made larger than the design strength by an amount corresponding to the variation, and the amount of solidifying material added increases, which is uneconomical.
(2) In the deep mixing treatment method, in the viscous ground with high adhesive strength, mixing failure occurs due to the occurrence of the co-rotation phenomenon, and the target quality may not be ensured.
(3) In soil layers that contain a large amount of organic matter such as organic soil and peat, and volcanic ash-like clay soils such as loam and red and black black, the solidified material may be hardened, resulting in target quality. It was often impossible to secure.
(4) The ground containing a large amount of organic matter is uneconomical because it requires a large amount of solidifying material.
(5) If the ground is composed of multiple soil layers, the amount of solidification material added to the soil layer with the lowest strength is discharged to the entire depth range. The amount of solidifying material had to be added, which was uneconomical. In addition, the amount of construction generated soil (residual soil) increased, and the load on the environment was large.
(6) Even if agitation and mixing are performed reliably, the strength of soil cement depends on the soil to be improved. Therefore, if an unexpected soil appears, the improved strength will not reach the target value. There was a risk of poor construction.
(7) In the deep mixed processing method used for building foundations, the improved strength is about 1 to 3 N / mm ² , and due to this, a wider area is improved by supporting the same load compared to the wrinkle concrete There was a need to do. Along with this, not only the amount of soil to be improved required for ground improvement increases, but also the footing volume of the foundation increases, so the construction cost has increased.

The fluidized earth method also has the following problems.
(1) Since the local soil and solidification material are mixed with a ground mixer, the locally generated soil is used. Therefore, the quality after improvement varies from one soil to another due to the physical properties of the soil. There is a disadvantage that it is large. In addition, since locally generated sediment is used, especially when the local sediment is organic soil, a large amount of cement is required to obtain a desired uniaxial compressive strength, which may be uneconomical.
(2) Since the excavated sediment is discharged to the ground and mixed with the solidified material by a ground mixer to form a slurry-like cement milk and returned to the original position again, the number of construction steps increases and the cost is high.
(3) Although it is temporary, since the earth and sand of the place which should be improved is excavated and removed, the stress balance by the previous loading load collapses and the supporting ground loosens. For this reason, the supporting force of the excavation bottom ground is reduced.
(4) If the bottom surface from which the earth and sand have been removed is not carefully treated, the problem of initial settlement similar to the tip slime of cast-in-place piles will occur.

Furthermore, the PIP pile method and the RG pile method have the following problems.
(1) It is necessary to control the moisture content of the fine aggregate used for mortar production, resulting in variations in quality.
(2) Since the mortar contains fine aggregates, the mortar has to use a highly fluid material having a flow value of 18 to 20 seconds, and not only does it easily cause breathing, but also excavated earth and sand, etc. Falls into the mortar, and earth and sand are mixed in the mortar in a lump.
(3) In the case of sandy or sandy silt layers, hole wall collapse may occur due to spring water or groundwater pressure, so it is necessary to use bentonite mud or a mixture of this with a small amount of cement during excavation. There is. In addition, bentonite becomes sludge designated as industrial waste, and enormous costs are incurred for subsequent treatment.
(4) As a result, a slime layer is formed between the bottom surface of the mortar column and the supporting ground, so that a slime treatment step is required.
(5) Further, in the PIP pile method and the RG pile method, since the reinforcing bar is inserted after filling the mortar, the mortar is injected to the depth below the bottom surface of the foundation slab, and as a result, the head shaping at the time of root cutting becomes difficult.
An object of the present invention is to solve such a problem, and to provide a method for constructing a stable quality column regardless of the properties of the target ground, and to provide a stable quality column. It is.

The present invention has such a problem has been solved cent proposed replacement construction method of the column of the invention, continuously or intermittently spiral blades have a drilling unit to tip over the auger shaft full length Existence of the auger while rotating forward , and after reaching the replacement bottom position of the column, the auger consists of a mixture of at least hydraulic powder , pozzolanic powder and water, and when kneaded Or by pulling up the auger forward or substantially non-rotatingly while discharging the filler with a consistency of 150 to 400 mm as a table flow value from the tip of the auger during construction. The column is replaced with a filler.
In this invention, the forward rotation of the screw auger refers to a rotation in which excavated soil in the ground is discharged to the ground side by the screw auger. In addition, the expression “substantially no rotation” is an expression including a state in which the rotation is not rotated or a state in which the rotation is normal or reverse at a very low speed that can be regarded as not substantially rotating.

According to the replacement construction method of this column, since the raw ground and the filler are not mixed with stirring, a solidified body (column) having almost the same quality as that kneaded with a ground mixer can be obtained, and the deep mixing process The variation in quality can be made very small compared to the column by the construction method, the strength of the solidified body (column) can be set arbitrarily, and it can be easily realized, and within the specified replacement range It is possible to leave the soil in the non-replacement range above it without removing it. In particular, the filler has a table flow value of 150 to 400 mm at the time of kneading or construction. When the filler is less than 150 mm, it takes too much time during construction or construction is impossible. This is because if it exceeds 1, the possibility that a large amount of earth and sand will be mixed into the uncured solid body after replacement becomes high. If the filler has a table flow value in the above range, it will ensure fluidity filling in the excavation hole, prevent the wall from collapsing, and the sediment above the replacement range will fall into the replaced filler. Can be prevented. In addition, in order to make the above phenomenon extremely small and to make a high-quality column, it is more preferable that the consistency of the filler is 150 mm to 330 mm in terms of a table flow value. Further, even if the mixture used as the filler is a mixture obtained by adding additives and additives in addition to the powder having hydraulic properties and the powder having pozzolanic properties, the filler is filled if it is within the above-mentioned consistency range. Can be used as a material. By adding additives, etc., it becomes possible to adjust the filler composition to express any strength, for example, cheap fly ash or blast furnace slag powder is used as an admixture in the filler By doing so, the cost of the filler can be reduced. Examples of the hydraulic powder include so-called cements such as Portland cement (ordinary, early strength, moderate heat), blast furnace cement, fly ash cement, cement-based solidified material, and the like.

  Further, as a screw auger usable in the column replacement construction method of the present invention, an auger in which the spiral blade is a continuous spiral screw, an auger in which the spiral blade is an intermittent spiral screw, and an auger having a length corresponding to at least the column construction length. The auger and spiral wing covered by a cylindrical casing are composed of a plurality of intermittent spiral screws, and at least a part directly related to column construction of the intermittent spiral screws has a cylindrical ring fixed on the outer periphery. Auger, etc.

According to the auger in which the spiral blade is a continuous spiral screw, the replacement work can be easily performed by using a general-purpose spiral screw auger.
According to the auger where the spiral wing is an intermittent spiral screw, in a collapsible ground such as sandy ground or gravelly ground, if excavating with a continuous spiral screw, there is a possibility that the excavated soil may be discharged more than necessary. By using an intermittent spiral screw auger, the amount of soil discharged can be reduced and the disturbance of the surrounding ground can be reduced. As a result, the disturbance and looseness of the supporting ground can be reduced. Further, the outer diameter of the intermittent spiral screw does not need to be the same as the diameter of the excavating blade, and if the diameter is reduced, the amount of soil removal can be further reduced.

In addition, according to the auger covered with a cylindrical casing with a length corresponding to at least the length of the column construction, the surrounding ground is loosened to prevent the earth and sand around the drilling hole from being drawn excessively by the spiral screw. Without replacement, the replacement with the original ground becomes more reliable. At the same time, the supporting ground is not loosened, and the supporting force of the replaced column is not reduced. The cylindrical casing may be mounted coaxially with the screw auger and relatively forward and backward rotatable.
Further, according to the auger in which the spiral blade is composed of a plurality of intermittent spiral screws and a cylindrical ring is fixed to the outer periphery of at least a portion directly related to the column construction of the intermittent spiral screws, a simple device can be used. As with the case of using a casing, it can be replaced with a reliable original ground. Also, the auger removal work of the auger pulled up to the ground can be performed more easily than when the casing is used.

Further, examples of the excavating part at the tip of the screw auger include an excavating blade provided at the tip of the screw auger and an excavating claw provided at the tip of the spiral blade located at the tip of the screw auger. The excavation claw of the excavation blade and the excavation claw at the tip of the spiral blade exhibit power in excavation (particularly, hard ground), but this may be a flat claw.
Excavation efficiency is improved by the presence of the excavation part. Also, when the filler replacement upper end is shaped with the spiral blade tip provided with the drilling claw or the drilling blade provided with the drilling claw, the upper end is shaped according to the shape of the claw, so when the filler is consolidated Unevenness can be made. Therefore, it is necessary to reshape the upper end surface of the replacement column in a subsequent process. By using a flat nail, it can be finished in a flat shape in the replacement step, so that reshaping work is unnecessary.

The substitution column of the present invention, organic and spiral blade drilling portion is continuously or intermittently be present over the auger shaft full length to the tip, and excavation while forward rotation the auger, the substitution bottom position of the column After reaching the filling material, the filling material is composed of a mixture of at least hydraulic powder , pozzolanic powder and water, and the consistency of the filling material during kneading or construction is 150 to 400 mm as a table flow value. It is constructed by pulling up the auger forward or substantially without rotation while discharging the material from the tip of the auger.
Further, when the replacement upper end position of the column is deeper than the ground surface (that is, in the case of a replacement column that is built by leaving an empty digging portion on the ground surface side), the replacement column of the present invention is normally rotated or substantially non-rotated. When the top end of the auger reaches the planned replacement upper end position of the auger, the discharge of the filler from the discharge port of the auger is stopped, and further, the auger is pulled back to the ground while rotating backward or forward. It is built by raising.

Since there is no process in which the original ground and the filler are agitated and mixed, this replacement column has almost the same quality as that kneaded by an above-ground mixer, and there is little variation in quality.
Even when earth and sand are left above the replacement range, since the table flow value of the filler is small, the earth and sand does not fall into the filler and become a high quality replacement column.
This replacement column is a column made from a powder having hydraulic properties and a powder having pozzolanic properties, and in addition to the powder having hydraulic properties and the powder having pozzolanic properties , additives and additives are added. It may be a column made of the added mixture, and if it can be used as a filler within the above-mentioned consistency range, the strength of the filler can be adjusted to any desired strength by adding additives. Can be easily provided, and for example, by using inexpensive fly ash or blast furnace slag powder as an admixture, the cost can be reduced.

In addition, the expression of reverse rotation or forward rotation is an expression including the case of substantially no rotation.
Also, if the screw auger is pulled forward while discharging the filler, the earth and sand on the spiral blades of the auger will not fall easily, so the replacement of the filler with the in-situ soil will be performed more reliably. Cheap. This is particularly effective when the original soil is sandy ground with low adhesive strength.
On the other hand, in the case where the original soil is a ground where there is no risk of falling like viscous clay with high adhesive strength, it is possible to build a replacement column that contains virtually no soil mass even if it is pulled up without rotation. Become. However, even if the original soil is a viscous soil, it is preferable to pull up the auger by forward rotation because it can cope with the appearance of an unexpected formation.
If the ground around the replacement column is solid, the discharge pressure can be used as an auxiliary means for pulling up the screw auger.
Furthermore, when an empty digging portion is provided, if the screw auger is pulled up while being reversely rotated, the excavated soil can be left in the empty digging portion, but if there is no need to leave the excavated soil in the empty digging portion, Thus, when the excavated soil adheres to the auger and does not fall even if it rotates backward, the auger may be pulled up in a substantially non-rotating state or in a normal rotation. At this time, if the auger is pulled up without rotation, it cannot be said that there is no possibility of negative pressure being generated at the tip of the auger. However, when it is rotated, negative pressure is less likely to be generated than when it is not rotated.

According to the column replacement construction method and the column replacement of the present invention, the following effects can be obtained.
(1) Since the raw ground and the filler are not stirred and mixed, a solidified body (column) in almost the same state (quality) as when kneaded with an above-ground mixer can be obtained (claim 1).
(2) For the same reason, the quality variation can be made very small as compared with the column by the deep mixing method (claim 1).
(3) By setting the consistency of the filler at the time of kneading or construction to 150 to 400 mm, preferably 150 to 330 mm as a table flow value, the upper earth and sand were replaced during the construction of the replacement column. It can prevent falling in a filler (Claim 1). Accordingly, it is possible to build a column having almost the same quality as the state of being kneaded by a ground mixer, and it is possible to build a replacement column having a small variation in uniaxial compression strength.
(4) By setting the consistency of the filler at the time of kneading or construction to 150 to 400 mm, preferably 150 to 330 mm as a table flow value, the upper earth and sand were replaced during the construction of the replacement column. Since it can prevent falling in a filling material, it becomes possible to replace the inside of a predetermined replacement range and leave the soil of the non-replacement range above it as it is without discharging. In other words, it is possible to have an empty moat above the replacement column.

(5) Further, the replacement column of the present invention is of high quality because the original ground and the filler are not agitated and mixed, but are replaced with the same state as when kneaded with an above-ground mixer. Variation is small (claim 2).
(6) Since it is a replacement column obtained by setting the consistency of the filler at the time of kneading or construction to 150 to 400 mm, preferably 150 to 330 mm as a table flow value, uncured solidified replaced with the filler The body (column) is of high quality in which earth and sand are not mixed (claim 2).
Since the replacement column of the present invention can be of high quality, a column with a smaller area is sufficient to support the same load compared to a conventional ground improvement column. Therefore, the footing volume of the foundation is also reduced, and it is possible not only to reduce the amount of concrete in the footing but also to reduce the amount of construction generated soil due to the footing construction, and the construction cost can be greatly reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a front explanatory view showing the first embodiment of the present invention in the order of construction steps (a), (b), (c) and (d).
First, as shown in FIG. 1 (a), the screw auger 6 is set at the pile center position of the ground G, and the screw auger 6 is dug while rotating forward, and dug to the replacement bottom position of the column. When the excavation resistance is large and it is difficult to excavate, excavation may be performed while discharging air or a small amount of water using auxiliary means. Since the screw auger 6 at this time is rotating forward, the excavated soil of the ground G is excavated by the screw auger 6 while being discharged to the ground.
FIG. 1B shows a state in which the screw auger 6 has dug up and has reached a column replacement bottom position (hereinafter referred to as a predetermined depth).
When the screw auger 6 reaches the predetermined depth of the column, the excavation is stopped, and then the screw auger 6 is rotated forward while discharging the filler from the discharge port 11 of the auger tip 7a as shown in FIG. 1 (c). Pull up. In this case, it may be pulled up with substantially no rotation instead of forward rotation.
If the filling material is discharged into the space formed below the tip portion 7a of the screw auger 6 and is pulled up while filling with a balance between the lifting speed and the discharge amount so that no cavity is generated, the replacement column is placed below the screw auger 6 14 is formed.

In addition, if the screw auger 6 is pulled up by rotating forward as shown in FIG. 1 (c) while discharging the filler, the earth and sand on the spiral wing of the auger will not easily fall. Replacement with the original soil is easier to be performed. This is particularly effective when the original soil is sandy ground with low adhesive strength. On the other hand, in the case where the in-situ soil is a ground where there is no risk of falling, such as a viscous soil with a large adhesive force, it is possible to construct a replacement column that contains substantially no soil mass even if it is pulled up without rotation. . However, even if the original soil is a viscous soil, it is preferable to pull up the auger by forward rotation because it can cope with the appearance of an unexpected formation.
If the ground around the replacement column is solid, the discharge pressure can be used as an auxiliary means for pulling up the screw auger. That is, the pulling force can be obtained by receiving the discharge pressure on the lower surface of the excavation part 9.
Next, when the lifting of the screw auger 6 reaches the planned replacement upper end position of the column as shown in FIG. 1D, in the example shown in FIG. 1, the screw auger 6 is driven and the filler is discharged. To stop. As a result, the replacement column 14 having a predetermined length is constructed.
In FIG. 1D, the replacement column 14 is built up to the ground surface. However, the discharge of the filler may be stopped at an arbitrary position so that the filler does not exist in the upper part.

  The screw auger 6 shown in FIG. 1 is the continuous screw auger 6 shown in a front view in FIG. The screw auger 6 is a screw auger 6 in which a spiral blade 8 is continuously provided on an auger shaft 7, and an excavation part 9 and a discharge port 11 are provided at a tip 7 a. In this figure, the tip portion of the spiral blade located at the tip of the screw auger 6 corresponds to the excavation portion 9, and a plurality of excavation claws 10 project from the tip portion. It can be said that the excavation claw provided at the tip of the auger shaft 7 is also a part of the excavation part 9. Further, the discharge port 11 may be opened downward at the distal end portion 7 a of the auger shaft 7 or may be opened laterally at the distal peripheral surface portion of the auger shaft 7. Since the continuous screw auger 6 has the spiral blades 8 continuous, the ability to discharge excavated soil during excavation is enhanced. Moreover, earth and sand removal from the continuous screw auger on the ground can be easily performed by a normal method (for example, a method using a backhoe or the like).

  FIG. 3 is a construction schematic diagram illustrating the plant equipment and the like when the replacement column shown in FIG. 1 is built. That is, in the construction of the replacement column of the present invention, construction is performed using the construction machine 1 and the plant equipment 20 as shown in FIG. The construction machine 1 is provided with a leader 3 standing up and down, and an auger motor 4 provided with a swivel is slidably provided on the leader 3. Although FIG. 3 shows the construction machine 1 having the crawler type carriage unit 2, the construction machine 1 may be a carriage type having wheels or a mounting type without a carriage part. The auger motor 4 moves forward and backward with the feeding device 5 connected thereto. Examples of the feeding device 5 include a winch that can be lifted and retracted, but this may be other means. For example, a field chain or a hydraulic cylinder that is driven and transmitted via a sprocket from a drive motor can be exemplified. Although not shown, the construction machine 1 may be a crane-type construction machine and the reader 3 may be suspended.

The auger motor 4 incorporates a drive mechanism that drives the screw auger 6 connected to the auger motor 4 to rotate forward and backward. Therefore, the screw auger 6 connected to the auger motor 4 is given a digging force and a pulling force by the feeding device 5, and a forward and reverse rotational force is given by the drive mechanism of the auger motor 4. Therefore, the screw auger 6 connected to the auger motor 4 can be digged while being rotated forward, pulled up while being rotated forward, digged while being rotated in reverse, or pulled up while being reversed. In addition, it can be pulled up substantially without rotation, and can be stopped at any position when excavating and pulling up.
Note that the excavation speed and the pulling speed can be kept constant by the construction management device having the constant speed control device. Further, the discharge amount can be kept constant by the flow meter 26. Therefore, it is possible to replace the raw ground soil with a filler while balancing the lifting speed and the discharge amount so that no hollow portion is generated.

  On the other hand, the plant equipment 20 includes a mixer 21, a silo 22, a water tank 23, a pump 24, and the like as shown in FIG. 3, and the filler is stirred together with water by the mixer 21 (FIG. 3 shows a grout mixer). A slurry or mortar mixed by mixing is supplied through a grout hose 25 with a pump 24 (a tube pump is shown in FIG. 3). A flow meter 26 is disposed in the vicinity of the discharge port of the pump or in the middle of the grout hose 25. A flow meter 26 disposed in the vicinity of the discharge port of the pump or in the middle of the grout hose 25 knows the supply amount of the filler, and manages the supply amount of the filler so as to match the gap amount generated by pulling up the auger.

Further, in the plant equipment 20 shown in FIG. 4, a pan-type forced kneading mixer 21 (not shown) can be used instead of the pan-type forced kneading mixer. A snake type pump (screw pump) 24 is shown instead of the tube pump. The snake type pump (screw pump) 24 has a mechanism in which a fixed volume is pushed out without pulsation by rotation of a single screw rotor having a half pitch of the stator through a stator having two inner screws. It is.
Plunger type pumps can also be used as long as they have the ability as a pump. However, if the pump 24 is a snake type pump (screw pump) as shown in FIG. 4, the consistency of the filling material during kneading or construction. It is particularly preferable since the filler can be supplied to the auger tip and discharged from the auger tip even if it is low (hard) (for example, 150 to 260 mm in table flow value). . Thus, even those having low consistency can be kneaded by using the pan type forced kneading mixer shown in FIG. 4 or a biaxial forced stirring mixer (not shown).

On the other hand, the screw auger 6 has a structure in which a spiral auger shaft 7 is provided on a hollow auger shaft 7, and has an excavation part 9 and a discharge port 11 at an auger tip part 7a. The hollow portion of the auger shaft 7 or the pipe provided in the central portion serves as a filler passage. The filler is made in the plant facility 20, is pumped through the grout hose 25, passes through the hollow portion (passage) of the auger shaft 7 through the swivel of the auger motor 4, and is discharged from the discharge port 11 at the tip.
In addition, although the discharge port 11 can be provided in the lower end surface thru | or lower end part side surface of the auger shaft 7, it is more preferable from the point of replaceability of a front-end | tip part to provide in the lower end surface.

A continuous screw auger 6 in which spiral blades 8 are continuous as a screw auger is shown as a representative example as shown in FIGS. However, there are various types of screw augers 6 and there is no particular limitation as long as they can be implemented.
That is, it goes without saying that the screw auger 6 shown in FIG. 2 can be replaced with another screw auger such as shown in FIGS. Although the construction machine 1 is omitted in the embodiment, the screw auger 6 is connected to the construction machine 1 and constructed as in the embodiment shown in FIGS. 3 and 4.
The filler used is composed of a mixture of at least hydraulic powder, pozzolanic powder and water, and the consistency of the filler during kneading or construction is 150 to 150 in terms of table flow value. The filler is 400 mm.

Next, screw augers other than the continuous screw auger described with reference to FIG. 2 will be described with reference to the drawings.
FIG. 5 is a front view of an intermittent screw auger, which shows a screw auger 6 in which a spiral blade 8 of a single blade 8a is intermittently provided on an auger shaft 7. In this figure, the screw portion at the lower end is excavated. It can be said that it is a wing | blade, The excavation part 9 and the discharge outlet 11 are provided in the front-end | tip 7a. In this figure, the tip portion of the spiral blade located at the tip of the screw auger 6 corresponds to the excavation portion 9, and a plurality of excavation claws 10 project from the tip portion. A claw provided at the tip of the rod part is also a part of the excavation part 9. This is the same in the following figures.

FIG. 6 is a front view of another intermittent screw auger, which is a screw auger 6 in which a spiral blade 8 of two blades 8b and 8b is intermittently provided on an auger shaft 7. It can be said that the screw part is an excavation blade, and the excavation part 9 and the discharge port 11 are provided at the tip 7a. Also in this figure, the tip of the screw auger 6 corresponds to the excavation part 9. The intermittent screw auger 6 shown in FIG. 5 and FIG. 6 can reduce the amount of excavated soil during excavation, and can reduce the disturbance of the surrounding ground. Therefore, the supporting ground can be made less disturbed.
The screw auger shown in FIGS. 5 and 6 or a screw auger described later can be easily removed from the screw auger on the ground by an ordinary method (for example, a method using a backhoe or the like).

FIG. 7 is a front view (a) and a cross-sectional view (b) of the casing auger, in which the screw auger 6 is inserted coaxially into the cylindrical casing 12 so as to be relatively rotatable forward and backward. . According to this casing auger, since the casing 12 is provided, the excavation soil of the original ground is surely discharged, and mixing of the ground soil from the surrounding ground to the filler is prevented. As a result, replacement with the original ground becomes more reliable, and a higher quality replacement column can be built. As shown in the figure, an excavation claw 12 a may be provided at the tip of the casing 12. If the excavation claw 12a is provided at the tip of the casing 12, the excavation efficiency is improved and the power is exerted even on hard ground. The cylindrical casing 12 may rotate synchronously with the screw auger 6 or may not rotate synchronously. Further, the screw auger 6 and the casing 12 may rotate independently of each other, and the casing 12 may not rotate.
In addition, for the earth and sand dropping on the ground in the casing 12, a method is used in which a plurality of openings are provided on the side surface and the soil is discharged on the ground. However, there is a problem that the soil removal property is lowered in the viscous ground compared with the sandy ground.

FIG. 8 is a front view (a) of an intermittent screw auger with a ring and a side view (b) showing the ring portion in cross section. A cylindrical ring 13 is provided on the outer periphery of a spiral blade 8 provided intermittently (intermittently). It is fixed. The ring 13 does not need to be fixed to the outer periphery of all the spiral blades 8 provided intermittently, and may be fixed to the outer periphery of the spiral blade 8 at least in a portion directly related to column construction. In this intermittent screw auger with a ring, since the cylindrical ring 13 is fixed at the outer periphery of the spiral blade 8 at least in the part directly related to the column construction, the amount of excavated soil is reduced and the disturbance of the surrounding ground is reduced. In addition, since the mixing of the ground soil from the surrounding ground to the filler is suppressed, the replacement with the original ground is ensured, and a high-quality replacement column can be built. Moreover, the auger removal work of the auger pulled up to the ground is also easier than when the casing 12 shown in FIG. 7 is used. In addition, the earth and sand confined in the ring part can be easily discharged at the time of the next column construction. Further, the spiral ring 13 in the cylindrical ring 13 does not need to be a single blade, and may be a plurality of blades. However, by using a plurality of spiral blades as shown in FIG. 6, the height of the cylindrical ring 13 can be increased. Can be small.
The cylindrical ring 13 at the lowermost end is preferably provided with an excavation claw 13a on the periphery of the lower end. If the excavation claw 13a is provided at least at the lower end portion of the ring 13 at the lowermost end portion, excavation efficiency is improved and power is exerted even on hard ground. Further, an excavation claw 13a may be provided on the upper edge of the uppermost cylindrical ring 13 to reduce the resistance during pulling. FIG. 8 shows a case where a flat claw 10a is provided at the lower end of the spiral blade 8 at the lowermost end. In FIG. 8, the lower end position of the flat claw 10a is located above the lower end of the excavation claw 13a of the ring, but each position may be reversed.

  FIG. 9 is a front view (a) and a side view (b) showing the upper small-diameter screw auger, and shows the screw auger 6 in which the upper part of the spiral blade 8 has a small diameter. That is, the lower portion of the spiral blade 8 has a large diameter R1, and the upper portion has a small diameter R2. According to the upper small-diameter screw auger 6, the amount of excavated soil can be reduced while being a continuous spiral blade. Moreover, sediment removal on the ground is easy as in the case of a continuous screw.

  Moreover, as the excavation part 9 provided in the front-end | tip part 7a of the screw auger 6, the structure which provides the excavation nail | claw 10 in the front-end | tip of the spiral blade 8 located in the screw auger front end as shown in FIG. 10 can be illustrated. As an excavation part having a structure in which the excavation claw 10 is protruded from the tip of the screw auger as illustrated in FIG. 2, or as an excavation part having an excavation claw 10 at the end of the spiral blade 8 as shown in FIG. When the filling material replacement upper end portion is shaped with the excavation claw 10, the upper end portion is shaped according to the shape of the claw, so that irregularities are formed when the filling material is consolidated. Therefore, it is necessary to reshape the upper end surface of the replacement column in a later process. As a result, the excavation claw 10 is preferably a flat claw 10a as shown in FIGS. 8B and 9B, which can be finished in a flat shape, so that reshaping work is not necessary.

As described above, the filler is a mixture of at least a hydraulic powder, a pozzolanic powder and water, and the consistency of the filler at the time of kneading or construction is 150 to 150 in terms of table flow value. The filler is 400 mm.
The HamaTakashizai is a mixture of powder having a powder and pozzolanic with hydraulic, it may be those which contain other admixtures or admixtures, with stuffing material containing no sediment and aggregate It is desirable to be. Aggregate means fine aggregate or progenitor aggregate in concrete, and powders such as blast furnace slag and fly ash are not aggregates. The use of fillers including earth and sand and aggregates causes the disadvantages described with respect to the prior art. As a particularly preferable filler, it is composed of a mixture of hydraulic powder, pozzolanic powder and water as main components, and the consistency of the filler during kneading or construction is 150 to 400 mm as a table flow value. Certain fillers can be exemplified as being economical and preferable in terms of substitution.
According to this particularly preferred filler, it is possible to reduce the cost of the filler by using inexpensive fly ash or blast furnace slag powder as the filler, and by adjusting the composition of the filler, It becomes possible to develop strength.
In addition, you may add a thickener (for example, basic magnesium carbonate, bentonite, methylcellulose, carboxymethylcellulose, etc.), a water reducing agent, a fluidizing agent, etc. to a filler.

  In addition, by setting the consistency of the filler at the time of kneading or construction to a table flow value of 150 to 400 mm, preferably 150 to 330 mm, it is possible to ensure fluid fillability in the drilling hole and to collapse the hole wall Furthermore, it is possible to prevent the earth and sand above the replacement range from being replaced and falling into the filler. The consistency of the filler at the time of kneading or construction is set to 150 mm to 400 mm in the table flow value. If it is less than 150 mm, it takes too much time during construction or construction becomes impossible, and if it exceeds 400 mm, it is replaced. This is because there is a high possibility that a large amount of earth and sand is mixed in the filler (solidified body).

If the consistency (degree of softness, viscosity) at the time of kneading or construction of this filler is set to 150 mm to 400 mm, preferably 150 to 330 mm, as a table flow value, uncured solidified replaced with filler It is possible to prevent the sediment above the replacement range from falling into the body (column). If the thickness is less than 150 mm, the viscosity is too high to be supplied by a pump, so that the construction is impossible at the present time. If the thickness exceeds 400 mm, the viscosity is too low to prevent sedimentation.
Here, the table flow value is a value measured by measuring the flow value in the physical test method for cement shown in JIS R 5201.
However, in JIS, the diameter of the flow table is 300 mm. In the present invention, a flow value was measured by fixing a plate having a diameter of 500 mm on a table having a diameter of 300 mm.

According to the present invention, the screw auger 6 having the excavation part 9 at the tip is dug forward and reaches the replacement bottom position of the column. Then, at least the hydraulic powder and the pozzolanic powder While discharging a filler from the tip 7a of the screw auger 6 that is made of a mixture with water and has a consistency at the time of kneading or construction of 150 to 400 mm as a table flow value, it rotates forward or substantially When the screw auger 6 is pulled up by rotation and the replacement upper end position of the column is reached, the raising of the auger 6 and the discharge of the filler are stopped, and then the screw auger 6 is pulled up to build the replacement column. it can. Note that it is preferable to temporarily stop the pulling of the screw auger when the discharge of the filler is stopped from the viewpoint of forming the head of the replacement column.

FIG. 11 is a front explanatory view showing the second embodiment of the present invention in the order of construction steps (a), (b), (c), (d), and (e).
First, as shown in FIG. 11 (a), the screw auger 6 is set at the pile center position of the ground G, and the screw auger 6 is dug to a predetermined depth of the column while rotating forward. When the screw auger 6 reaches a predetermined depth as shown in FIG. 11 (b), the excavation is stopped, and the filler is discharged from the discharge port 11 of the tip 7a of the screw auger 6 as shown in FIG. 11 (c). Pull the screw auger 6 forward. In this case, it may be pulled up with substantially no rotation instead of forward rotation. Note that it is preferable to set the discharge amount of the filler at this time to an amount (corresponding to the amount) corresponding to the pulling amount of the screw auger 6, since the lower portion of the auger 6 can be replaced without a gap when the auger 6 is pulled up.
When the screw auger 6 is pulled up in the forward direction, as shown in FIG. 11 (d), the screw auger 6 is lifted and the filler is discharged when reaching the upper position where replacement is planned, in this example, the position where the empty digging portion 15 is left. Then, the screw auger 6 is pulled up while rotating in the reverse direction. In this case, it is possible to pull up with substantially no rotation even if it is pulled up with forward rotation. Since the excavated soil is not discharged by the reverse rotation of the screw auger 6, in this second embodiment, as shown in FIG. 11 (e), a replacement column 14 having a predetermined length with a hollow portion 15 left on the ground side is built. Is done.
In this way, when providing an empty digging portion, if the screw auger is pulled up while being reversely rotated, the excavated soil can be left in the empty digging portion, but it is not necessary to leave the excavated soil in the empty digging portion, or the viscosity If the excavated soil adheres to the auger and does not fall even if it rotates reversely like soil, the auger may be pulled up in a substantially non-rotating state or in a normal rotation. At this time, if the auger is pulled up without rotation, it cannot be said that there is no possibility of negative pressure being generated at the tip of the auger. However, when it is rotated, negative pressure is less likely to be generated than when it is not rotated.

Next, examples and comparative examples are shown. In Example 1 and Comparative Example, materials used and test methods are as follows. W represents water, C represents ordinary Portland cement, and basic magnesium carbonate (hereinafter referred to as MC) was used as the thickener.
Materials used (1) Ordinary Portland cement (2) Basic magnesium carbonate (MC)
Test method (1) Uniaxial compression test method: JIS A 1216
(2) Flow value: JIS R 5201
(3) Specimen preparation method: JGS 0821

The construction method of the second embodiment shown in FIG. 11 using the construction machine, that is, the screw auger 6 having the excavation part 9 at the tip is rotated forward with the construction machine, and the column is After reaching the replacement bottom position, the screw auger 6 is pulled up in a forward rotation while discharging the filler not including earth and sand or aggregate from the auger tip, and when the planned replacement bottom position upper end position of the column is reached, In the construction method for constructing a replacement column in which the empty digging portion 15 is left on the ground side by pulling up the auger 6 and discharging the filler, and then pulling up the screw auger 6 while rotating in reverse, Table 1 and Table 2 A replacement column was constructed according to the construction specifications and construction conditions shown in.
Replacement columns Nos. 2 to 5 are Example 1.

Comparative example

  Replacement columns No. 1 and No. 6 constructed in the same manner as in Example 1 are comparative examples.

In this Example 1 and Comparative Example,
(1) The buried land was a loose ground mainly composed of sandy soil. The groundwater level was not present in the buried layer.
(2) Five substitution columns (No. 1, 2, 3, 5, 6) with W / C = 30 to 60% and MC / C = 0.0% as the mixing conditions and W / C as the mixing conditions A total of 6 pieces were constructed with 1 piece (No. 4) at 40% and MC / C = 0.5%. No. 1 and No. 6 are comparative examples.
(3) In all cases, the diameter of the replacement column was 0.7 m, an air digging portion of 1.0 m from the ground surface was present, and the length of the replacement column was 2.0 m.
(4) In the same test No., the consistency of the filling material at the time of construction and the consistency of the filling material collected from the plant show values within a range that can be regarded as almost the same, and compare Table 1 with Table 3 described later. Then, the consistency of the filler during construction when construction was possible was 212 to 430 mm in flow value, and became larger as W / C became smaller.
What is shown as a flow value in Table 3 to be described later is a table flow value obtained by measuring the flow value in the cement physical test method shown in JIS R 5201 for the filler collected from the plant at the time of construction. In the measurement of the table flow value according to JIS R 5201, the measurement range of the flow tester is up to 300 mm. Therefore, in the measurement of the flow value of 300 mm or more, a large-diameter table plate is joined to the flow table of the flow tester. Was measured.

(5) The 28-day strength of the fillers that can be constructed is 21.3 to 37.6 N for specimens (indicated as plant cores in Table 3) prepared by filling fillers collected from the plant into paper molds. / Mm ² . It was 12.1-9.0 N / mm < ² > in the extraction core (it describes with extraction core in Table 3) extract | collected using the core machine after hardening of a substitution column.
(6) Since the filler with W / C = 30% and MC / C = 0.0% for No. 6 had high viscosity and was difficult to pump stably, a replacement column should be built. I couldn't. The consistency (viscosity) under these compounding conditions was 135 mm as a table flow value (shown as a flow value in the table).
(7) The construction machine was an 80-ton class crawler type three-point support pile driver.
(8) As shown in Table 2, tube pumps are used for replacement columns No. 1 and 2, and snakes are used for replacement columns No. 3, 4, 5, and 6 as pumps for supplying filler. A type pump was used.
(9) As shown in Table 2, as the mixer, a grout mixer was used in the replacement columns No. 1 and 2, and a biaxial forced kneading mixer was used in the replacement columns No. 3, 4, 5, and 6.

  Moreover, the construction test results of Example 1 and the comparative example are as shown in Table 3.

According to this test result, a lot of soil blocks are mixed in the cross section of the replacement column having a table flow value of 430 mm for the No. 1 filling material as a comparative example, and the strength of the sampling core specimen with a material age of 28 days is also high. It was 12.1 N / mm ² , which was the smallest strength as compared with column Nos. ² to 5 as examples. The intensity of the extraction core specimen of comparative examples No.1 is, 8.5 N / mm ² in wood age 7 days a 12.1 N / mm ² in wood age 28 days, the plant core specimen of wood 12.7 N / mm ² decrees 7 days strength, compared to 21.3N / mm ² of wood age 28 days strength, about 67 percent Material age 7 days, be approximately between 57% and less strength wood age 28 days It was. By the way, many soil blocks were mixed in the extracted core specimen, and no soil blocks were mixed in the plant core specimen.
In the comparative example of No. 6 in which the table flow value of the filler is 135 mm, the viscosity is too high to be fed by a pump, and the table flow values of the column Nos. 2 to 5 in the example are 212 to 316 mm. This indicates that the amount of dirt mixed in is small and the strength is high. Further, in the column Nos. 2 to 5 of the examples, even if the plant core specimen and the extracted core specimen are compared, there is no difference in strength and the columns have almost the same quality, and the effect of the present invention is high. Understandable.

Next, as Example 2, ordinary Portland cement (denoted as C in the following formulation), fly ash type II (denoted as F in the following formulation example) and water (denoted as W in the following formulation example) and Was used, and the blending conditions of the filler were as follows.
W / (C + F) = 40% F / C = 4.0
Construction was performed based on the construction method shown in FIG. 11 using the filler thus obtained. The column diameter was 700 mm, the digging length was 1.0 m, and the replacement column length was 2.0 m.
The consistency when the filler was kneaded (that is, the consistency of the filler during construction) was 212 mm in terms of table flow.
In addition, the number of rotations at the time of construction, construction speed, discharge amount, replacement volume, etc. were constructed under the same conditions as in test column 4 in Table 2.
Although the replacement column was dug out after the construction, the amount of mixed soil was small, and the uniaxial compressive strength after 28 days was 8.6 N / mm ² , which was an excellent replacement column.

  The above-described embodiments and examples do not limit the present invention, and various modifications are allowed without departing from the spirit of the present invention.

It is front explanatory drawing which shows 1st Embodiment of this invention in construction process order (a) (b) (c) (d). It is a front view of a continuous screw auger. It is the construction schematic diagram which illustrated also the plant equipment at the time of substitution column construction. It is the construction schematic diagram which illustrated the plant equipment etc. different from FIG. 3 at the time of replacement column construction. It is a front view of an intermittent screw auger. It is a front view of another intermittent screw auger. It is the front view (a) and sectional drawing (b) of a casing auger. It is the front view (a) of the intermittent screw auger with a ring, and the side view (b) which shows a ring part in a cross section. It is the front view (a) and side view (b) of an upper small diameter screw auger. It is a front view which illustrates the structure of the excavation part of a screw auger (a) (b). It is front explanatory drawing which shows 2nd Embodiment of this invention in construction process order (a) (b) (c) (d) (e).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Construction machine 3 Leader 4 Auger motor 5 Feeding device 6 Screw auger 7 Auger shaft 7a Auger tip (tip)
DESCRIPTION OF SYMBOLS 8 Spiral wing 8a Spiral wing of 1 blade 8b Spiral wing of 2 blade 9 Excavation part 10 Excavation claw 10a Flat claw 11 Discharge port 12 Casing 12a Excavation claw 13 Ring 14 Column 15 Empty excavation part 20 Plant equipment 21 Mixer 22 Silo 23 Aquarium 24 Pump 25 Grout Hose 26 Flowmeter

Claims (2)

Tip Yes spiraling vanes drilling portion is continuously or intermittently be present over the auger shaft entire length, and excavation while forward rotation the auger, after reaching the substitution bottom position of the column, at least a hydraulic A filler consisting of a powder, a pozzolanic powder and water, and having a table flow value of 150 to 400 mm as the filler consistency during kneading or construction is discharged from the auger tip. On the other hand, a column replacement construction method characterized in that the column soil is replaced with a filling material by pulling up the auger forward rotation or substantially non-rotation. Tip Yes spiraling vanes drilling portion is continuously or intermittently be present over the auger shaft entire length, and excavation while forward rotation the auger, after reaching the substitution bottom position of the column, at least a hydraulic A filler consisting of a powder, a pozzolanic powder and water, and having a table flow value of 150 to 400 mm as the filler consistency during kneading or construction is discharged from the auger tip. However, the replacement column is constructed by pulling up the auger forwardly or substantially without rotation.

Images