JP2008031713A - Replacing construction method of column - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a replacing construction method of a column for preventing the initial settlement of a replacing column replaced with a filler being 150 to 400 mm in a table flow value in consistency. <P>SOLUTION: Boring is advanced while normally rotating a screw auger having an excavation part on the tip, and after reaching a replacing bottom position of the column, the filler without including sediment and an aggregate and being 150 to 400 mm in the table flow value in the consistency of the filler in kneading-up or construction is delivered from a screw auger tip, while rotating the screw auger for at least about 10 seconds and for about 3 minutes at most, without moving the auger in the vertical direction at the position, and afterwards, the column whose ground earth is replaced with the filler is formed by pulling up the screw auger by normally rotating or reversely rotating, while delivering the filler from the screw auger tip. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a column replacement construction method 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 (for example, see Non-Patent Document 1).
JP 2003-247228 A (Claim 3, paragraph number 0002) JP-A-8-260450 (Claim 1) Japanese Patent No. 3280710 (Claim 1) Japanese Patent No. 3306460 (paragraph number 0002) Underground Continuous Wall Construction Method Design / Construction Handbook Japan Construction Mechanization Association Issued 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 with the original ground while filling the solidified material at the same time, it is improved due to the fact that the soil physical properties of the ground to be improved are not constant The soil quality 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 occurred due to the co-rotation phenomenon, and the target quality was often not secured.
(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, it will fill the entire depth range with the amount of solidification material required for the soil layer with the lowest strength development. 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 mixing treatment method, it is necessary to improve a larger area to support the same load due to the low expression strength even if a large amount of solidified material such as humus or organic soil is added. there were. 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 earth and sand are mixed with the ground mixer, the locally generated earth and sand are used. Therefore, the quality after the improvement varies greatly due to the soil physical properties and soil quality variations. There is a drawback. Moreover, since the local earth and sand and the solidified material are mixed, a large amount of cement is required to obtain the required uniaxial compressive strength, which may be uneconomical.
(2) Since the excavated soil is discharged to the ground, mixed with the solidified material by a ground mixer to form a slurry-like fluidized soil, and returned to its original position, the number of construction steps increases and costs are reduced. high.
(3) Although it is temporary, since the earth and sand at the location to be improved are excavated and removed, the stress balance due to the overload until then is lost and the supporting ground is loosened. 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 initial settlement problem similar to the tip slime of cast-in-place piles occurs when a vertical load from the structure is applied.

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 the flow of the mortar. Due to its high nature, excavated earth and sand fall into the mortar, and the earth and sand are mixed into the mortar.
(3) In sandy and gravelly soil layers, hole wall collapse due to spring water and groundwater pressure is likely to occur. Therefore, it is necessary to use bentonite mud or a mixture of a small amount of cement for excavation. is there. In addition, since bentonite becomes sludge, enormous costs are incurred for subsequent processing.
(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.

  In order to solve such problems and to provide a method for constructing a stable quality column without depending on the properties of the target ground, the present applicant digs up while rotating a screw auger having a drilling portion at the tip in the forward direction. After reaching the replacement bottom position of the column, a filler having a table flow value of 150 to 400 mm, which does not contain earth and sand or aggregate, and has a consistency of the filler during kneading or construction, is replaced with the replacement bottom of the column. While discharging from the tip of the screw auger from the position, pull up the auger by forward rotation, and when it reaches the planned replacement upper end position of the column, stop discharging the filler, and then pull up while rotating the auger in the reverse direction Thus, Japanese Patent Application No. 2005-109463 has previously filed a column replacement construction method characterized in that the ground soil is replaced with a filler.

  However, when a high support force is desired for the replaced column, depending on the building conditions, there may be a risk that the initial settlement of the column will be large. May become excessive. That is, when the vertical load of the structure is applied to the replacement column, there is a risk that the initial subsidence increases and the subsidence amount exceeds the allowable value.

  The present invention has been proposed to solve such problems, and its purpose is to prevent the initial subsidence of a replacement column that is replaced with a filler whose consistency is 150 to 400 mm as a table flow value. It is to provide a replacement construction method.

  One column replacement construction method according to the present invention is that a screw auger having a drilling portion at the tip is dug forward and reaches the replacement bottom position of the column, and then at least the auger is not moved up and down at that position. Rotate the screw auger for about 10 seconds, at most about 3 minutes, and do not contain earth and sand or aggregate, and the filling material consistency at the time of kneading or construction is 150 to 400 mm in table flow value While discharging from the tip of the screw auger, and then pulling up the screw auger while rotating forward or reverse while discharging the filler from the tip of the screw auger, the ground soil was replaced with the filler. It is characterized by being a column.

  According to another column replacement construction method of the present invention, a screw auger having an excavating portion at the tip is forwardly rotated, and the diameter of the replacement column to be constructed is at least about 10 cm above the planned replacement bottom position of the column. After reaching the upper position, discharge the filler from the tip of the screw auger, which does not contain earth and sand or aggregate, and the consistency of the filler during kneading or construction is 150 to 400 mm in table flow value. While digging forward and reaching the replacement bottom position of the column, do not move the screw auger up and down at that position for at least 10 seconds, not more than 3 minutes, and do not contain earth and sand or aggregate A filler with a consistency of 150 to 400 mm in the table flow value when the filler is raised or constructed is Discharge from the tip of the screw auger while rolling, and then pull up the screw auger while rotating forward or reverse while discharging the filler from the tip of the screw auger, so that the ground soil is replaced with the filler. It is characterized by having a column.

  In the above two column replacement construction method, when the filler is discharged from the tip of the screw auger without moving the screw auger in the vertical direction after reaching the replacement bottom position of the column, the screw It is particularly preferable that the auger be carried out while repeating forward and reverse rotations.

In these inventions, the forward rotation of the screw auger refers to the direction in which the screw auger rotates in the direction in which the ground excavated soil is discharged to the ground side by the screw auger during excavation. Further, in the present invention, the direction in which the screw auger rotates in the same direction as that during excavation at the time of pulling up is referred to as the forward rotation direction of the screw auger.
In addition, the expression “forward rotation” or “reverse rotation” includes an expression that includes substantially no rotation, and the expression “substantially no rotation” can be regarded as not being rotated or substantially not rotating. It is also an expression including the state of forward rotation or reverse rotation at a very low speed.

  For example, the auger is not moved up and down at the position reaching the replacement bottom position of the column of the present invention, and does not contain earth or sand and aggregate, and the consistency of the filler during kneading or construction is 150 in table flow value. Without performing the step of discharging the filler of ~ 400 mm from the tip of the screw auger while rotating the screw auger, the screw auger having the excavating part at the tip is rotated forward to the replacement bottom position of the column. Extruding, discharging filler from the tip of the screw auger that does not contain earth and sand or aggregate, and the consistency of the filler during kneading or construction is 150 to 400 mm in the table flow value, and then the filler By pulling out the screw auger from the tip of the screw auger while rotating the screw auger forward or backward. When the tip of the column replaced with filler is built in a good support ground with an N value of 30 or more (N value of 20 or more depending on conditions such as load), the figure is shown for rotating excavation claws during excavation. As shown in FIG. 6 (b), the crack 4 is generated in the original ground G below the planned replacement bottom of the column, and the original ground G below the planned replacement bottom of the column is disturbed and loosened. The present inventors have found that the initial subsidence amount of the replaced column may be increased when a vertical load from the structure is applied.

  Therefore, the auger is not moved in the vertical direction at the position reaching the replacement bottom position of the column, does not include earth and sand and aggregate, and the consistency of the filler during kneading or construction is 150 to 400 mm in table flow value. When the step of discharging the filler from the tip of the screw auger while rotating the screw auger is performed, the filler is filled in the crack 4 as shown in FIG. It was found that the amount of initial settlement when the load was applied decreased.

  Note that if the discharge time of the filler at the planned replacement bottom position of the column is shortened, there is a risk that the effect of preventing the initial settlement will be reduced. The amount increases, the filler is mixed with the earth and sand discharged when the screw auger is pulled up, the amount increases, and the amount of the earth and sand not mixed with the filler is reduced accordingly. Therefore, the discharged earth and sand becomes an industrial waste mixed with a filler, and the disposal cost is expensive, which is not preferable. Therefore, the discharge time of the filler at the planned replacement bottom position of the column is preferably at least about 10 seconds, at most about 3 minutes, and discharged from the tip of the screw auger while rotating the screw auger in the forward and reverse directions. As a result, a replacement column having a small initial settlement can be obtained.

  Also, depending on the shape of the screw auger, after reaching a position at least about 10 cm above the planned replacement bottom position of the column, and at most about the diameter of the replacement column to be built, it does not contain earth and sand or aggregate and is kneaded. In some cases, it is necessary to add a step of excavating the filler with a consistency of 150 to 400 mm in terms of table flow value during construction while discharging it from the tip of the screw auger.

In this case as well, if the filler discharge start position above the planned replacement bottom position of the column is made lower, the effect of adding this step is less, and from the higher position above the planned replacement bottom position of the column, from the tip of the screw auger When excavating while discharging the filler, the amount of filler discharged increases, the filler is mixed with the earth and sand discharged when the screw auger is pulled up, the amount increases, and the amount of filler discharged is that much. Less soil is mixed.
Therefore, the discharged earth and sand becomes an industrial waste mixed with a filler, and the disposal cost is expensive, which is not preferable. Therefore, if it is necessary to add this step, after reaching the position at least about 10 cm above the planned replacement bottom position of the column and at most about the diameter of the replacement column to be built, the filler material is inserted from the tip of the screw auger. It is preferable to dig while discharging. Accordingly, the amount of the filler mixed with the earth and sand discharged when the screw auger is pulled up can be reduced, and a replacement column with less initial settlement when a vertical load from the structure is applied can be obtained.

  After reaching the replacement bottom position of the column, when the filler is discharged from the tip of the screw auger without moving the screw auger up and down at that position, the screw auger is repeatedly rotated in the forward and reverse directions. However, if implemented, the best initial settlement prevention effect can be obtained.

  Moreover, an excavation part points out either of the following parts. If you have a drilling claw that protrudes from the tip of the screw auger shaft in addition to the drilling blade that has a drilling claw attached to the tip of the spiral auger located at the tip of the screw auger, If the excavating blade and the excavating claw protruding from the screw auger shaft tip are excavation parts, and there is no excavating claw protruding from the screw auger shaft tip, the spiral blade located at the screw auger tip A drilling wing having a drilling claw at the tip is a drilling part.

  According to the replacement construction method of this replacement column, since the raw ground and the filler are not stirred and mixed, it is possible to obtain a cured body (column) having almost the same quality as the state of kneading with the ground mixer, Compared to the column by the deep mixing method, the variation in quality can be made extremely small, and the strength of the hardened body (column) can be set arbitrarily by adjusting the composition of the filler to achieve it. In addition, it is possible to replace the soil within the predetermined replacement range and leave the sediment in the non-replacement range above it without leaving the soil.

Further, when supplying the filler to the screw auger, a snake pump (screw pump) can be used in addition to the squeeze pump and the plunger pump.
When the filler is supplied to the auger by a snake pump (screw type pump) and the filler is discharged from the tip of the auger, the consistency of the filler during kneading or construction is low. However, it is particularly preferable because it can be constructed.

The filler may be cement alone, or may contain other admixtures or admixtures, and the filler is not particularly limited, but should be a filler that does not contain earth or sand. .
In the present invention, the aggregate means fine aggregate or coarse aggregate called concrete, and powders such as blast furnace slag and fly ash are not aggregates. When a filler containing earth and sand or aggregate is used, the disadvantages described above occur.

Further, the filler needs to be a filler having a table flow value of 150 to 400 mm in the consistency of the filler during kneading or construction.
In addition, 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, it is possible to ensure fluidity filling in the drilling hole, and It is possible to prevent collapse and further prevent the earth and sand above the replacement range from being replaced and falling into the filler.
If the consistency of the filler during kneading or construction is set to 150 mm to 400 mm in the table flow value, if it is less than 150 mm, the resistance (frictional force) in the pipe will increase and it will take too much time during construction. (Discharge) becomes impossible, and when it exceeds 400 mm, there is a high possibility that a large amount of earth and sand is mixed in the solidified body.
In addition, as described above, when a filler is supplied to the tip of the auger by a snake type pump (screw type pump) and the filler is discharged from the tip of the auger, filling at the time of kneading or construction is performed. Even if the consistency of the material is 150 to 260 mm in terms of a table flow value, it can be applied particularly preferably.

  The table flow value is a table flow measured by fixing a plate having a diameter of 500 mm on a flow table having a diameter of 300 mm, instead of the diameter of 300 mm of the flow table defined in the physical test method for cement according to JIS R 5201. Value.

Such a filler can reduce the cost of the filler by using inexpensive fly ash or blast furnace slag powder as the filler, and can adjust the blending ratio of the filler to give any strength. It becomes possible to express.
The mixing ratio of fly ash or blast furnace slag powder is 3 to 20 parts by weight of fly ash or blast furnace slag powder with respect to 1 part by weight of cement. It can be used as a filler. Generally, in this case, the water content is 30 to 50% based on the total weight of cement and fly ash or blast furnace slag powder. Blast furnace slag powder is preferably used to increase the compressive strength of the replaced column.

  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. An auger covered with a cylindrical casing, an auger covered with a cylindrical casing, an auger with an edge plate on the screw edge of a continuous spiral screw, and a spiral wing are composed of a plurality of intermittent spiral screws, In addition, an auger having a cylindrical ring fixed on the outer periphery can be cited as at least a portion directly related to column construction in the intermittent spiral screw. Of course, an auger in which two spiral blades are provided at the same height with a phase difference of 180 degrees may be used.

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 gravel ground, if excavated with a continuous spiral screw, there is a possibility of discharging the excavated soil more than necessary, By using an intermittent spiral screw auger, the amount of soil discharged can be reduced and loosening due to disturbance of the surrounding ground can be reduced. As a result, the looseness of the supporting ground can be reduced. Further, the outer diameter of the intermittent spiral screw may be the same as the diameter of the excavating blade, but if the outer diameter of the intermittent spiral screw is smaller than the diameter of the excavating blade, the amount of soil removal can be further reduced.

  Further, according to the auger covered with a cylindrical casing having a length corresponding to at least the length of the column construction, the sandy soil layer is used to prevent the earth and sand around the drilling hole from being excessively drawn by the spiral screw. In a gravelly soil layer or the like, even if the ground is prone to collapse due to spring water or groundwater pressure, the replacement with the original ground is more reliable without loosening the surrounding ground. At the same time, the support ground is not loosened, and the initial subsidence amount of the replacement column does not increase when a vertical load is applied from the structure. The cylindrical casing is mounted coaxially with the screw auger so as to be able to rotate forward and backward relatively, or the casing is rotatably mounted independently, or fixed so that the casing does not rotate. May be.

Furthermore, according to the auger in which the spiral wing is composed of a plurality of intermittent spiral screws and a cylindrical ring is fixed to the outer periphery of at least a portion of the intermittent spiral screws directly related to column construction, the hole wall collapses. There is an action to prevent, and the replacement with the original ground can be performed as in the case of using the casing with a simple device. Also, the auger removal work of the auger pulled up to the ground can be performed more easily than when the casing is used.
In the case of a screw auger with an edge plate attached to the spiral screw, the possibility that the excavated soil that is being discharged along the screw portion spills out from the screw end portion is further reduced.

Examples of the excavating portion at the tip of the screw auger include an excavating claw provided at the tip of the screw auger shaft and an excavating claw provided at the tip of the spiral blade. The excavating claw of the excavating blade and the excavating claw at the tip of the auger shaft exhibit power in excavation (especially hard ground), but the excavating claw provided at the tip of the spiral wing may be a flat nail depending on the ground conditions. Good.
Excavation efficiency is improved by the presence of the excavation part. Further, when the filler replacement upper end portion is shaped with the excavating blade provided with the excavating claw after completion of the replacement column construction, the upper end surface is shaped according to the shape of the claw, so that irregularities are formed when the filler is consolidated. 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.

  In addition, while discharging the filler from the tip of the auger, the auger is pulled up by forward rotation or reverse rotation (eg, forward rotation depending on the ground condition), and when reaching the planned replacement upper end position of the column, the discharge of the filler is stopped. Then, by pulling up the auger while rotating it forward or backward, even when the replacement column has earth and sand above the column, if the table flow value of the filler is 150 to 400 mm, the replacement range The upper left earth and sand are not dropped and mixed in the filler. Therefore, it is a good quality replacement column that does not contain soil. In addition, if the table flow value of the filler is 150 to 330 mm, even if the ground conditions are more likely to collapse, even if there is soil to be left above the column, a good quality replacement column that does not mix dirt, etc. It can be.

According to the column replacement construction method of the present invention and the replacement column constructed by this method, the following effects can be obtained.
(1) Regardless of the soil quality and ground variation, replacement at the tip of the column can be performed reliably, making it possible to build a column with almost the same quality as when kneading with a ground mixer, and with uniaxial compression strength. It is possible to build replacement columns with small variations.
(2) According to the column replacement construction method of the present invention, and compared with mortar having high fluidity used in the conventional construction method, the filler used in the present invention can have extremely low fluidity. Therefore, it is possible to prevent the earth and sand above the replacement range from being replaced and falling into the filler. As a result, it is possible to build a column with almost the same quality as when kneaded with an above-ground mixer, and it is possible to build a replacement column with a small variation in uniaxial compression strength.

(3) Also in this invention, the filler used in this invention can be extremely low in fluidity compared to the high fluidity mortar used in the conventional construction method. Even if earth and sand are left behind, it can be prevented from falling into the filler. As a result, it is possible to replace the inside of the predetermined replacement range and leave the sediment in the non-replacement range above it as it is without discharging.
(4) For the same reason as in (2), quality variation can be greatly reduced as compared with the column by the deep mixing processing method.
(5) For the same reason, it is possible to easily set the strength of the solidified body (column) and realize it.
(6) By adjusting the composition of the filler, it becomes possible to develop an arbitrary strength.
(7) When inexpensive fly ash or blast furnace slag powder is used as a filler in the filler, the cost of the filler can be reduced.

  (8) Excavation efficiency is improved by the presence of the excavation part. Also, when the filler replacement upper end is shaped with the excavation claw at the tip of the auger shaft and / or the excavation blade with the excavation claw protruding, 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.

(9) Since the replacement column obtained by the present invention can be of high quality, a column with a small area is sufficient to support the same load as in the conventional ground improvement column. Therefore, the footing volume of the foundation of the structure is also reduced, and not only the concrete amount of the footing can be reduced, but also the construction generated soil accompanying the footing construction can be reduced, and the construction cost can be greatly reduced.
(10) The replacement column obtained by the present invention has excellent performance as described above, and can be a column with a small initial subsidence when a vertical load from the structure acts on the replacement column.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings using an example in which a continuous screw auger having continuous spiral blades is used as the screw auger. The outer diameter of the used screw auger is 600 mm.

First, as shown in FIG. 1 (a), the screw auger 1 is set at the center position of the replacement column to be built, and then, as shown in FIG. Dig up to. As shown in FIG. 1 (c), when the screw auger 1 reaches a predetermined depth, at that position, as shown in FIG. 1 (d), the screw auger 1 is not moved up and down for at least about 10 seconds and at most 3 minutes. The tip of the screw auger 1 is rotated while the screw auger 1 is rotated while the filler agglomerate does not contain earth and sand or aggregate and the consistency of the filler at the time of kneading or construction is 150 to 400 mm as a table flow value. Discharge from. Then, as shown in FIG.1 (e), the screw auger 1 is pulled up by forward rotation, discharging a filler.
It is possible to pull up the screw auger 1 with substantially no rotation or reverse rotation, but the probability that the excavated soil does not fall into the filler when the screw auger 1 is pulled forward or substantially without rotation. Is more preferable because it becomes higher.
When the column replacement planned upper end position L2 is reached as shown in FIG. 1 (f), the discharge of the filler is stopped, and then the screw auger 1 is pulled up while being reversely rotated as shown in FIG. 1 (g). Thus, the column 2 in which the ground soil is replaced with the filler is used. In addition, in the example of FIG. 1, the hollow portion 3 in which no filler exists is present on the ground side. In addition, it is possible to stop the discharge of the filler and then rotate the screw auger 1 in the forward direction instead of the reverse rotation when pulling up the screw auger 1. It is preferable because excavated soil can be left behind.

  Further, as shown in FIG. 2, the screw auger 1 having an excavating part at the tip is moved forward, and the position is at least about 10 cm above the planned replacement bottom position L1 of the column and at most about the diameter of the replacement column to be built at most. When the filler agglomerate does not contain earth and sand and aggregates and the consistency of the filler during kneading or construction is 150 to 400 mm as a table flow value, the filler is discharged while being discharged from the tip of the screw auger 1. It is also possible to carry out in a deformed form dug by rotation. That is, as shown in FIG. 2A, the screw auger 1 is set at the center position of the replacement column to be built, and then the screw auger 1 is dug while rotating forward as shown in FIG. 2B. As shown in FIG. 2 (c), after reaching the position about 10 cm above the planned replacement bottom position L1 of the column, or about the diameter of the replacement column to be built at most, and when it does not contain earth or sand and aggregate and is kneaded Or the filler whose consistency at the time of construction is 150-400 mm in a table flow value is dug in the forward rotation while being discharged from the tip of the screw auger 1. When the screw auger 1 reaches a predetermined depth, as shown in FIG. 2 (d), the screw auger 1 is not moved in the vertical direction as shown in FIG. And discharging from the tip of the screw auger. Then, as shown in FIG.2 (e), the screw auger 1 is pulled up by forward rotation, discharging the said filler. When reaching the column replacement planned upper end position L2 as shown in FIG. 2 (f), the discharge of the filler is stopped, and then the screw auger 1 is pulled up while being reversely rotated as shown in FIG. 2 (g). Thus, the column 2 in which the ground soil is replaced with the filler is used.

  In addition, after reaching the replacement bottom position L1 of the column, when the filler is discharged from the tip of the screw auger 1 without moving the screw auger 1 up and down at that position, the screw auger 1 is moved in the forward and reverse directions. More preferably, the rotation is repeated.

The loam ground continued to GL-5.15m shown in FIG. 3 by the above process, and the test was performed on the ground where a gravel layer having an N value of 50 or more appears.
The filler used should only have a strength equal to or greater than the ground strength of the ground. Usually, fly ash is used as the main raw material and cement is used, but steel pipes and reinforcing steel rods are used in the replacement column. When a core material such as the above is inserted to obtain a composite structure or a high strength, a material obtained by mixing cement with blast furnace slag as a main raw material is used.
This time, in order to carry out the vertical loading test of the replacement column, we used blast furnace slag mixed with cement as the main raw material. This is to prevent the replacement column from being destroyed before the supporting ground is destroyed when the vertical loading test is performed. Specific implementation formulations are shown in Table 1.

Table 2 shows the table flow value (expressed as TF value in the table) and uniaxial compressive strength of this formulation.

  The construction equipment is a 80-ton class three-point support pile driver as a base machine, the mixer is a biaxial forced kneading mixer for concrete, the pump is a screw pump, and the spiral auger has an outer diameter of 600 mm as described above. It was used.

In Example 1, the construction shown in FIG. 3 was performed on the ground shown in FIG. 3, and specific construction processes are shown below together with the excavation speed and the discharge amount. The tip position of the replacement column to be built (hereinafter referred to as a predetermined depth) is GL-5.2 m.
While rotating the spiral auger forward, it digs up to a predetermined depth of GL-5.2m at a speed of 2.0m per minute, and discharges the filler at a discharge rate of 100 liters per minute without moving the spiral auger up and down at that position. While rotating forward for 1 minute, the filler is discharged at a discharge rate of 100 liters per minute while the spiral auger is rotated forward and pulled up at a speed of 0.35 m / min. The material discharge was stopped and the spiral auger was pulled up to the ground while rotating in reverse.

  The relationship between this depth and construction time is shown in FIG. The relationship between the replacement column and the depth is shown on the left side of FIG.

  Moreover, in Example 2, although the construction shown in FIG. 2 was performed on the ground shown in FIG. 3, a specific construction process is shown below together with the excavation speed and the discharge amount. The tip position of the replacement column to be built (hereinafter referred to as a predetermined depth) is GL-5.2 m.

  While the spiral auger is rotating forward, it digs at a speed of 2.0 m per minute and reaches a position about 30 cm above the predetermined depth GL-5.2 m, and then discharges the filler at a predetermined discharge rate of 100 liters per minute. Digging to a depth of GL-5.2m, rotating the filler at a rate of 100 liters per minute without moving the spiral auger up and down at that position, rotating forward for 1 minute, then filling the filler at 100 liters per minute While discharging at a discharge rate, the spiral auger is rotated at a speed of 0.35 m per minute while rotating forward, and when the GL-1 m position is reached, the discharge of the filler is stopped and the spiral auger is rotated upward and pulled up to the ground. It was. The relationship between this depth and construction time is shown in FIG.

  For comparison, as shown in FIG. 4 (c), while rotating the spiral auger forward, it digs up to a predetermined depth, rotates forward at that position for 1 minute without discharging the filler, and then spiral auger. While discharging the filler from the tip of the container at a discharge rate of 100 liters per minute, the spiral auger is rotated at a speed of 0.35 m per minute while rotating forward, and when the GL-1 m position is reached, the discharge of the filler is stopped. A construction method in which a spiral auger is lifted to the ground while rotating in reverse.

The vertical loading test was performed on each replacement column after the age of the filler in the replacement column built according to Examples 1 and 2 and the comparative example became two weeks or longer.
The results of these loading tests are shown in Table 3 and FIG. 5 as the relationship between the amount of settlement at the tip of the replacement column and the load loaded on the head of the replacement column. FIG. 5 is a graph showing the data in Table 3.

As shown in Table 3 and FIG. 5, in the replacement column of Example 1, as shown in FIG. 5A, the initial subsidence amount is 0.5 mm with a replacement column head load of 300 kN. As shown in FIG. 5B, the displacement column has an initial subsidence amount of 0.2 mm at a displacement column head load of 300 kN, while the displacement column of the comparative example has a displacement column as shown in FIG. Furthermore, the displacement column head load is 4.3 mm at a load of 300 kN, and the amount of initial settlement is reduced in the present invention. In comparison between Example 1 and Example 2, it seems that Example 2 shows a tendency for the amount of settlement to be slightly smaller than Example 1, but there is no significant difference. The ultimate load is a load when the column tip sinking amount reaches 60 mm because the column tip sinking amount is defined as 10% of the column diameter. Therefore, the ultimate load was 2900 kN in Example 1, 2930 kN in Example 2, and 2830 kN in Comparative Example, and no significant difference was observed among the three.
In addition, the amount of initial ground subsidence in the comparative example is large as shown in FIG. 6 (b) due to the auger digging, and the crack 4 is generated in the original ground G deeper than the predetermined ground, and the tip portion ground is According to the present invention, as shown in FIG. 6 (a), the crack 4 can be filled with a filler in any case, so that the loosening of the tip ground is eliminated and the filler is strengthened. Therefore, it is estimated that the above results were obtained.

In addition, the construction of the example and the comparative example is performed under the same conditions as above, and after 5 days from the construction, the surrounding column is excavated and the replacement column is lifted, the tip shape is observed and the tip is cut and the sectional shape is taken. Was observed.
In both the replacement column of the two examples and the replacement column of the comparative example, almost no earth and sand were mixed in at the lower end of the replacement column, and the replacement column was composed only of the filler, and the quality is also shown in Table 2. The desired strength was exhibited.

It is front explanatory drawing which shows an example of the construction process of this invention in process order (a) (b) (c) (d) (e) (f) (g). It is front explanatory drawing which shows another example of the construction process of this invention in process order (a) (b) (c) (d) (e) (f) (g). It is explanatory drawing which shows a construction ground. It is explanatory drawing which shows the example of a construction process with a time-axis and a depth axis. It is a graph which shows the relationship between a loading load and a sinking amount. It is cross-sectional explanatory drawing (a) (b) which shows a state beyond a predetermined depth.

Explanation of symbols

1 Screw auger 2 Replacement column 3 Empty hole 4 Crack L1 Scheduled replacement bottom position L2 Scheduled replacement top position

Claims (3)

  After the screw auger with the excavating part at the tip is rotated forward and reaches the replacement bottom position of the column, the auger is not moved up and down at that position for at least about 10 seconds, at most about 3 minutes. Discharge from the tip of the screw auger while rotating the screw auger, the filler not containing the aggregate and the consistency of the filler at the time of kneading or construction is 150 to 400 mm in a table flow value, A column replacement construction method characterized in that a ground soil is replaced with a filler by discharging the filler from the tip end of the screw auger and pulling up the screw auger while rotating forward or backward. .   After the screw auger with the excavation part at the tip is rotated forward, the excavation is carried out, reaching at least 10 cm above the planned replacement bottom position of the column, and at most about the diameter of the replacement column to be built, Exclude the filler with a table flow value of 150 to 400 mm, which is not included and kneaded or constructed at the time of construction, by excavating it from the tip of the screw auger with a forward rotation, and at the replacement bottom position of the column After reaching the position, the screw auger is not moved up and down at that position for at least about 10 seconds, at most about 3 minutes. A filler with a flow value of 150 to 400 mm is discharged from the tip of the screw auger while rotating the screw auger. Then, by discharging the filler from the tip end of the screw auger and pulling up the screw auger while rotating forward or reverse, the column soil is replaced with the filler. Replacement building method. After reaching the replacement bottom position of the column, when the filler is discharged from the tip of the screw auger without moving the screw auger up and down at that position, the screw auger is repeatedly rotated in the forward and reverse directions. The column replacement construction method according to claim 1, wherein the column is replaced.

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