JP2012149503A - Soil improvement method and management method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new soil improvement method and a management method for the same capable of constructing an excellent deep layer mixing pile and a columnar continuous wall by breaking up a cut soil mass and homogeneously mixing the same with a solidification agent even for high-plasticity clay having a large plasticity index Ip as well as a large liquid limit W.SOLUTION: A soil improvement method includes a drilling process which: digs up a drilled soil mass with drilling blades; and cuts as well as breaks up the drilled soil mass by rotation of agitation blades, using a soil improvement machine having the drilling blades as well as the agitating blades. In the drilling process, the agitation blades are rotated at a velocity equal to or larger than an average peripheral velocity necessary for cutting a soil mass in accordance with shear strength of a soil property of the drilled soil mass. The soil improvement method also includes a solidification treatment process which mixes the drilled soil mass and a solidification agent.

Description

  The present invention relates to a ground improvement method and a management method thereof, and more specifically, using a ground improvement machine having a drilling blade and a stirring blade, a specific excavation, a drilling process under stirring conditions, a drilling clot, and a specific solidification It is related with the ground improvement construction method including the solidification process process which mixes a material on specific conditions, and its management method.

  The ground improvement works include CDM (Cement Deep Mixing Method) method, DJM (Dry Jet Mixing) method represented by deep mixing treatment method and SMW (Soil Mixing Wall) represented by soil cement underground continuous wall method. In these methods, construction is carried out with a ground improvement machine in which excavation blades, stirring blades, and fixed blades are attached to the tip of the rod attached to the ground improvement machine.

  That is, rotate the rod attached to the ground improvement machine, scrape the soil with the excavating blade attached to the tip of the rod, crush the excavated clot with the stirring blade fixed to the rod, mix with the solidification material while subdividing, solidify It is a construction method that creates columnar solidified bodies and continuous walls in the ground.

  FIG. 1 illustrates the tip portion of the ground improvement machine. FIG. 1 shows a single-axis type ground improvement machine, but there is a multi-axis type ground improvement machine.

  Usually, cement or lime is used as the solidifying material, and these solidifying materials may be used in the form of a slurry or as powder. Further, the mixing of the excavated soil block and the solidified material is not limited to the mixing at the time of excavation, the mixing at the time of lifting the rod, or the combination of these.

  In the above construction method, as an index indicating the degree of mixing of excavated soil mass and solidifying material, the number of blade cutting times (the stirring blades constituting the stirring blades when descending and rising the 1.0 m section in the soil to which the solidifying material was added) The concept of “total number of blade rotations” is introduced, and the number of blade cutting times is set to 350 times / m as a reference value.

  Furthermore, as a mechanical device, in order to prevent the stirring blade and the excavated soil mass from rotating and moving in the same direction, and to improve mixing, a fixed blade is attached to the outer ring (boss) that rotates freely with respect to the rod. There has been proposed a fixed wing in which this is cut into the soil to prevent rotation (see, for example, Patent Document 1).

  In any of these methods, the object is to subdivide the excavated soil mass and uniformly mix this with the solidified material to create a homogeneous solidified body.

  However, the soil quality to be improved varies. For example, even if the low-plastic soil has a high compressive strength, if mixed with a slurry-like solidified material, the clumps will loosen apart and tend to be subdivided, so mixing with the solidified material is comparative even if the peripheral speed of the stirring blade is low. It is easy to specify the degree of mixing by the number of blade cutting.

  In contrast, high-plastic clay is difficult to break apart even when mixed with a slurry-like solidifying material, and when mixed with a stirring blade, it adheres to the stirring blade and reattaches the subdivided soil, and rotates together with the stirring blade. However, even if the number of blade cuts is increased, there is a problem that the degree of mixing is not improved only by co-rotation.

Note that the high plasticity clay here, and large plasticity index Ip soil, in liquid limit W _L is large clay, in FIG. 2 is a plastic diagram according engineered classified, partitioned by line A and line B and a clay that is classified to a portion (CH) and, the water content ratio of the natural state in particular is smaller than liquid limit W _L, sensitive ratio like 2 following overconsolidated clay corresponds.

Japanese Patent No. 3621971

The present invention is, from the background as described above, even at high plasticity clays greater plasticity index Ip and liquid limit W _L is the cutting clods is subdivided, in the uniform mixing of the solidifying material, good deep mixing It is an object to provide a new ground improvement method and its management method capable of creating treated piles and columnar continuous walls.

  The present invention is characterized by the following in order to solve the above problems.

  The first is a ground improvement method including a drilling process in which a ground improvement machine having a drilling blade and a stirring blade is used to cut and subdivide the excavated soil mass excavated by the drilling blade with a rotating stirring blade. Corresponding to the shear strength of the soil, it includes a drilling step of rotating the stirring blade at an average peripheral speed or higher required for cutting the soil block, and a solidification process step of mixing the drilled soil block and the solidified material.

  Secondly, in the ground improvement method according to the first aspect of the present invention, after the excavation step including the excavation mixing step of forming the bubble mixed soil by adding bubbles or bubbles and water to the excavated soil mass, the solidified material is applied to the bubble mixed soil. It includes a solidification process step of adding and mixing to create a solidified material mixed soil.

  Third, in the ground improvement method of the first invention, after the excavation step including the excavation mixing step of forming the bubble mixed soil by simultaneously adding bubbles and solidified material or air bubbles and water and solidified material to the excavated soil mass, It includes a solidification process step in which a solidifying material is added to and mixed with the bubble mixed soil to form a solidified mixed soil.

  Fourth, in the ground improvement method of the first invention, after the excavation step including the excavation mixing step of forming the bubble mixed soil by simultaneously adding bubbles and solidified material or bubbles and water and solidified material to the excavated soil mass, It includes a solidification process step of adding a foam breaker and creating a solidified material mixed soil while breaking the foam.

  Fifth, in the ground improvement method of the second or third invention, a solidifying material added with a foam-breaking agent is added to the bubble mixed soil, and the solidified mixed soil is created while breaking the bubbles. Including processing steps.

Sixth, in the ground improvement method according to the second to fifth inventions, the properties of the bubble-mixed soil are such that the unit volume weight is 10.3 kN / m ³ or more and the table flow value (TF value) is 110 mm or more. Including a drilling process to adjust to

Seventh, in the ground improvement method according to the second to sixth inventions, the properties of the solidified mixed soil include a unit volume weight of 10.3 kN / m ³ or more and a vane shear strength of 8.0 kN / m ² or less. The excavation process and the solidification process are adjusted to be

Eighth, in the ground improvement method according to the second to sixth inventions, the properties of the solidified mixed soil are such that the unit volume weight is 10.3 kN / m ³ or more and the table flow value (TF value) is 110 mm or more. The excavation process and the solidification process are adjusted as described above.

  Ninth, in the ground improvement methods of the second to eighth inventions, the method includes an excavation and mixing step in which bubbles are added from the excavation blades to create an air-mixed soil.

  Tenth, in the ground improvement methods of the first to eighth inventions, the solidifying material is added from the excavation blade or the stirring blade, and includes a solidification treatment step.

  Eleventh, in the ground improvement method according to the first to tenth aspects of the present invention, as the solidification material, solidification treatment is performed using slurry-type solidification material milk to which a water amount of 45% or more of the minimum water solidification material ratio that can be pumped is added. Process.

  12thly, in the ground improvement construction method of the said 1st-10th invention, the solidification processing process is included using a powdery solidification material as a solidification material.

  Thirteenthly, in the ground improvement method of the second to twelfth inventions, bubbles having a median bubble diameter of 100 to 400 μm are used.

  Fourteenth, in the ground improvement method of the second to thirteenth inventions, at least a necessary amount of water that does not eliminate bubbles is added.

  Fifteenth, in the ground improvement methods of the first to fourteenth inventions, at least one of cements, limes and gypsum is used as the solidifying material.

  Sixteenth, in the ground improvement method according to any one of the first to fifteenth inventions, the shape of the rod holding the excavation blade and the stirring blade is rectangular, and the bubbles are increased by the compressed air and the foam breaker when the rod rotates. Including a solidification process step for creating a gap for allowing the air to escape to the ground.

  Seventeenth, in the ground improvement method according to the first to sixteenth aspects of the present invention, a casing is erected on the ground in response to an increase or decrease in the mixed soil produced in the excavation process or the solidification process.

  Eighteenth, in the ground improvement method according to the first to seventeenth aspects of the present invention, a fixed wing having a shape for guiding the excavated mass to the outer periphery is used for the ground improvement machine.

  Nineteenth, in the ground improvement method according to the first to eighteenth aspects of the invention, a stirring blade that rotates reversely to the excavation blade is used for the ground improvement machine.

  20thly, in the ground improvement method according to the first to 19th aspects of the present invention, the stirring blades of the ground improvement machine are attached in multiple stages so that they rotate in reverse.

21stly, in the management method of the ground improvement construction method, a part of the bubble mixed soil is sampled, the unit volume weight of the collected bubble mixed soil is 10.3 kN / m ³ or more, and the table flow value (TF value) is 110 mm or more. Manage.

Twenty-second, in the management method of the ground improvement method, a part of the solidified material mixed soil is sampled, the unit volume weight of the collected solidified material mixed soil is 10.3 kN / m ³ or more, and the table flow (TF value) is 110 mm. 23. In the management method of the ground improvement method, a part of the solidified material mixed soil is sampled, the unit volume weight of the collected solidified material mixed soil is 10.3 kN / m ³ or more, and the vane shear strength Manages 8.0 kN / m ² or less.

24thly, in the management method of a ground improvement construction method, the vane shear strength of solidification material mixing soil is managed below 8.0 kN / m < ² > by measuring the torque value of a stirrer.

According to the ground improvement method of the present invention, using a ground improvement machine having excavation blades and agitation blades, the agitation is performed at an average peripheral speed or higher required for cutting the mass, corresponding to the shear strength of the soil of the excavation mass. While rotating the wing, bubbles were added from the excavating wing to form a bubble mixed soil, and the excavation and mixing step for adjusting the properties of the bubble mixed soil and the solidification treatment step for mixing the bubble mixed soil and the solidified material were created. since the properties of the solidified material mixed soil was adjusted ground improvement method, even at high plasticity clay plasticity index Ip and liquid limit W _L is large, the cutting clods is subdivided, in the uniform mixing of the solidifying material Therefore, it can be a new ground improvement method capable of creating a good deep mixed processing pile or a columnar continuous wall.

  Furthermore, by specifying the bubble conditions to be added, the solidifying material conditions, the conditions of the excavating blade and the stirring blade, the effect of the present invention can be made more reliable.

It is the schematic which illustrated the construction machine front-end | tip part. It is a plastic figure by the engineering classification method of soil. It is the figure which showed the required average peripheral speed by soil quality in relation to the shear strength. It is the figure which showed the relationship between the rotational torque of a rod, and excavation depth. It is the figure which illustrated the relationship between uniaxial compressive strength and wet density. It is the figure which showed the relationship between bubble addition amount and vane shear strength. It is the figure which showed the relationship between bubble addition amount and TF value. It is the schematic which showed the process of the ground improvement construction method. It is the schematic which showed the example of the construction machine front-end | tip part (excavation blade) which has a bubble discharge port and a solidification material discharge port. It is the schematic which showed the example of the earth lump induction | guidance | derivation fixed wing | blade. It is the schematic which showed another example of the earth lump induction | guidance | derivation fixed wing | blade. It is the schematic which showed the example of the reverse stirring blade.

Regarding the ground improvement method of the present invention, first, the excavation process for subdividing the soil mass will be described in detail.
<Drilling process>
In the excavation process of the present invention, a ground improvement machine having excavation blades and agitation blades is used to cut and subdivide the excavated soil mass dug up by the excavation blades with rotating agitation blades. Then, the agitating blade is rotated at a speed equal to or higher than the average peripheral speed required for cutting the clot according to the shear strength of the soil of the excavated clot.

  The average peripheral speed required for cutting the clot can be obtained by applying to each condition of the stirring blade and the excavated clot described in detail below.

The excavated block is assumed to be spherical with a radius R (m), and the wet density is assumed to be ρ (kg / m ³ ). The stirring blade is caused to collide with the stationary mass at a peripheral speed V (m / s), and the force is set to F (N / m ² ). Cut the center of the soil mass with F. Let the shearing force of the soil block be τ (N / m ² ).
The mass m of the soil mass can be expressed by the formula (1).

  The collision force F and the shearing force τ can be expressed by equation (2).

  Equation (3) is obtained from the relationship between the momentum of the clot and the impulse.

  If the time for the circumferential speed V stirring blade to cut the clod is t (s), the equation (4) is obtained.

  Equation (5) is obtained from equations (2), (3), and (4).

  From these, in order to cut the clod, it can be achieved by colliding with the excavated clod at a peripheral speed equal to or higher than the peripheral speed V.

For example, as a general high plastic clay, an overconsolidated clay having a sensitivity ratio of 2 or less and a natural moisture content of a liquid limit or less is considered, and its wet density is 1600 kg / m ³ and a stirring blade having a radius of 0.6 m is used. When the relationship between the shear strength τ and the average peripheral speed is calculated using the equation (5), it can be represented by the graph shown in FIG.

As shown in the graph of FIG. 3, when the shear strength is 20000 N / m ² , the peripheral speed required for cutting is 4.3 m / s, and when the shear strength is 5000 N / m ² , 2.2 m / s. It becomes. The rotation speeds at this time are 138 rpm and 69 rpm, respectively. Since the rotation speed currently implemented is 20-40 rpm, it turns out that rotation speed is insufficient with respect to the cutting | disconnection of the block of high plastic clay.

  Since the peripheral speed of the stirring blade is proportional to the distance from the center, the average peripheral speed described here is assumed to be at the position of r / 2 (r is the radius of the stirring blade) of the stirring blade.

  Prior to the improvement, the soil layer to be improved shall be subjected to geological surveys, natural moisture content, liquid limit, shear strength, etc. shall be measured, and these values shall be used to determine the required average peripheral speed of the impeller. Can do.

  As is clear from the above, in the excavation process of the ground improvement method of the present invention, it corresponds to the peripheral speed of a certain value or more according to the soil quality, that is, the shear strength of the clot derived from the equation (5). The impeller impinges on the excavated soil block at a peripheral speed equal to or higher than the average peripheral speed value, and is cut and subdivided. Thereby, homogeneous mixing property with a solidification material can be improved.

  However, even when the above conditions are applied, when the high plastic clay is crushed and subdivided, it reattaches to the drilling blade and the stirring blade due to its viscosity, and tends to form a dumpling. When rotating at a high speed with the adhering to the surface, the rotational torque increases, so it is necessary to prevent the reattachment.

  Therefore, in order to prevent re-adhesion and reduce the rotational torque of the rod, by mixing air bubbles in the excavated soil and improving the fluidity, a ground improvement body with high workability can be obtained.

The construction method of the ground improvement method of the present invention will be described below, and preferable conditions for the ground improvement method using air bubbles are defined from the results of the test.
<Ground improvement method>
Examples of the ground improvement method of the present invention include the ground improvement method 1 and the ground improvement method 2 shown below.
(Ground improvement method 1)
The ground improvement construction method 1 adds the bubbles or bubbles and water while moving the excavation blade and the stirring blade downward, and forms the bubble excavation soil in which the excavated soil mass and the bubbles are mixed to the deepest part, and then the excavation blade and the stirring blade. This is a construction method for improving the ground by forming a solidified material mixed soil by adding a solidified material to the bubble mixed soil while pulling up the wing.

In this case, a foam breaker may be added to the solidified material at the time of pulling and the solidification treatment may be performed while breaking the foam.
(Ground improvement method 2)
Ground improvement construction method 2 is the method of deepening the bubble mixed soil in which excavated soil mass, bubbles and solidified material are mixed while adding excavation blade and agitating blade downward while excavating and mixing blades and adding bubbles and solidified material or bubbles, water and solidified material simultaneously. This is a construction method for improving the ground by forming a solidified material mixed soil by adding a solidified material to the bubble mixed soil while pulling up the excavating blade and the stirring blade upward.

  In this case, the solidification material may be added to the solidified material at the time of pulling up, and the solidification process may be performed while foaming. Alternatively, only the foam-breaking agent may be added without adding the solidification material, and the solidification process may be performed while foaming. May be.

  Further, in any of the ground improvement methods 1 and 2 above, in order to improve the mixing property by the excavation blade and the stirring blade, the excavation blade in which the bubble or the solidified material is located at the bottom when excavating to move downward It is effective to add from the stirring blade located at the top when pulling up.

In addition, the unit volume weight of the foam mixed soil, the solidified material mixed soil, and the foam solidified material mixed soil formed in each process step is 10.3 kN / m ³ or more in terms of the stability of the hole wall. It is necessary to adjust the amount of bubbles, the amount of water, and the amount of solidified material added so that the unit volume weight becomes 10.3 kN / m ³ or more.
<Field test>
A preferable property of the bubble mixed soil obtained by adding and mixing bubbles to the excavated soil block was confirmed by an on-site test shown below.

  In the field test, a uniaxial type with a 50cm radius stirring blade was used as a ground improvement machine, and the Kanto Loam layer was excavated to a depth of 6m while discharging bubbles from the tip of the stirrer shown in Fig. 1. Created soil. The bubble addition rate was changed in the range of 0 to 1.2%. Table 1 shows the field test conditions, and FIG. 4 shows the relationship between the rotational torque of the rod and the excavation depth. The bubble addition rate can be calculated by the following formula (6).

  From FIG. 4, it can be seen that when the bubble addition rate is in the range of 0 to 1.2%, the torque decreases as the bubble addition rate increases. No. 1 bubble addition rate of 1.2% and No. 1 When no additive of 6 is compared, the torque is found to be about ½. From these facts, it can be seen that by adding bubbles, the rotational torque is clearly reduced even in the ground improvement.

  Next, in the above-mentioned field test, excavation was performed while adding bubbles, and after creating the bubble mixed soil, the cement milk to which the foam breaker was added was kneaded with the bubble mixed soil while raising the stirring blade, and the solidification treatment was performed. went.

  In the excavation and mixing process of the ground improvement method of the present invention, bubbles are used. Therefore, in order to increase the strength of the solidified body and reduce the amount of waste mud, the bubbles are broken in the solidification process and guided to the ground. Need to foam.

  For this purpose, a foam breaker is added to the solidified milk or powdered solidified material used in the solidification treatment step and mixed with the bubble mixed soil or the bubble solidified material mixed soil. The effect of the surfactant is reduced, bubbles of several hundred microns come into contact with each other, and the bubbles merge to increase the particle size.

  By kneading, the bubbles gradually coalesce, the particle size gradually increases, and the buoyancy also increases, so that they reach the ground through the bubble mixed soil. That is, the bubbles in the bubble mixed soil can be removed.

Blast furnace cement type B is used as the solidification material, and the water-cement ratio (W / C) is changed to 45 to 100%, and cement foam milk is added to the cement milk to add mixed foam soil and cement milk. Were mixed and stirred to cause foam breakage, and the bubble defoaming condition was observed. The amount of cement added was 150 kg / m ^{3 for} each test improvement column.

  According to the observation of the defoaming situation, the test column No. In Nos. 1 and 2, it was observed that bubbles with a bubble diameter of about 5 to 10 cm rose in the bubble mixed soil and defoamed on the ground surface. 3-No. No defoaming phenomenon was observed in the test column 5.

FIG. 5 shows the results of the wet density and uniaxial compressive strength tests performed on the sampled samples in the field test. According to FIG. 5, although the amount of cement added to each improved column was the same as 150 kg / m ³ , both the wet density and the uniaxial compressive strength were tested. 1, 2 and no. There is a big difference between 3, 4, and 5. Test column No. Nos. 1 and 2 have a wet density of about 1.50 g / cm ³ , but no. 3, 4, and 5 are distributed in the range of 1.37 to 1.41 g / cm ³ , and this difference is considered to be a difference in the degree of defoaming.

No. Although the uniaxial compressive strength of 1 and 2 is 345 to 380 kN / m ² , 3-No. No. 5 is significantly different from 15 to 155 kN / m ² . 3-No. Since the bubbles were not defoamed from the ground improvement pillar of No. 5, the bubbles became weak points, and due to the lack of fluidity of the bubble-mixed soil, the kneading with the cement milk was insufficient, and the strength was not expressed. It seems that it has become smaller.

  As an index indicating fluidity, the TF value defined in JIS R 5201 can be mentioned. The TF values of 1 and 2 were 110 mm or more, whereas 3-No. 5 was about 100 mm. From this, it is estimated that 110 mm is the defoaming and kneading limit value.

  From these results, in the ground improvement method of the present invention, it is preferable to set the TF value of the bubble mixed soil to 110 mm or more in order to develop strength.

  Further, in another on-site test, preferable properties of the solidified material mixed soil to which the solidified material was added were clarified by measuring the vane shear strength (Geotechnical Society Standard JGS1411-2003) and the TF value.

  FIG. 6 is a result of measuring the vane shear strength of the mixed soil in which the required ground improvement strength was obtained in the field test, and FIG. 7 shows the relationship between the vane shear and the TF value of the same mixed soil. .

As the properties of the solidified material mixed soil in which the required ground improvement is obtained, the vane shear strength is about 8.0 kN / m ² or less in FIG. 6, and the TF value is 110 mm or more in FIG.

From these results, in the ground improvement construction method of the present invention, the vane shear strength of the solidified material mixed soil to which the solidified material is added is 8.0 kN / m ² or less, or the TF value is 110 mm or more, in order to develop strength. It is preferable that

The bubbles used in these field tests were bubbles with a foaming agent foamed 25 times, a unit volume weight of 0.392 kN / m ³ , and a median bubble particle size of 100 to 400 μm. Laboratory tests have confirmed that similar properties can be obtained even at a magnification of 30 times.

  The bubbles used in the excavation process for ground improvement according to the present invention are preferably those having a firing ratio of 20 to 30 times and a median bubble diameter of 100 to 400 μm.

  When excavating, subdividing, and mixing by adding bubbles, the moisture in the bubbles is adsorbed by the dry soil particles and bubbles are broken. Therefore, when making an improvement on an unsaturated soil layer, it is necessary to add water with cement milk or water so that bubbles do not break. The amount of water added by cement milk or water so as not to cause foam breakage is the amount of water at which the water content ratio after the addition becomes equal to or greater than the surface water content ratio.

  As the solidifying material used in the ground improvement method of the present invention, generally known soil solidifying materials can be used, and examples thereof include cements, limes, and gypsum solidifying materials. Among these, those containing Portland cement as a main material can be suitably used as a cement solidifying material.

  This Portland cement is supposed to chemically react with 25% of the cement weight of water in the setting reaction until complete hydration, and 15% of the cement weight is bound as gel water. It is generally known that the addition causes a decrease in strength.

  Since the amount of water contained in the soil to be improved is usually 40% or more, when using the solidified milk as a solidified material, it is desirable to have a minimum water content ratio that can be applied. Considering pumping as a rational pumping method based on the current technology, the minimum water-solidifying material ratio (W / C) that can be pumped is about 45%. It is preferable to set it to 45%.

  Furthermore, by using the minimum water-solidifying material ratio, the amount of mud required for industrial waste treatment is minimized, which is economically advantageous.

  As described above, in consideration of the compressive strength when the cell-mixed soil or cell-solidifying material mixed soil is solidified, the water-solidifying material ratio is preferably as small as possible within the range where construction is possible. Therefore, a powdery solidifying material having a water solidifying material ratio of 0 can also be used.

  In this case, there is no particular limitation on the method for stably and stably sending the powder solidified material into the bubble mixed soil or the bubble solidified material mixed soil, but in the ground improvement method of the present invention, A method of sending the powdered solidified material to the excavation blade or the stirring blade by pneumatic feeding can be suitably employed.

  In addition, when the powdered solidified material is sent out by pneumatic feeding or the like as described above, the fluidity of the mixed solid material or the mixed solid material mixed with bubbles may be changed, so that the construction can be performed. If it is a range, it is not necessary to limit TF value, vane shear strength, and unit volume weight.

  When bubbles are broken using a foam breaker, the bubbles repeatedly coalesce and increase in diameter and rise, but in order to promote this rise more efficiently, it is preferable to configure the passage of bubbles. .

  Therefore, by making the shape of the rod of the ground improvement machine rectangular, a void is created between the rod and the mixed soil by the rotation of the rod, and this void is configured as a passage for bubbles to facilitate defoaming. Can do.

  Furthermore, when the powdered solidified material is pneumatically fed to the stirring blade, the air that is pumped has a great influence on the surrounding ground such as leakage and eruption from the surrounding ground, and is effective for exhaust.

  FIG. 8 shows a process schematic diagram of the ground improvement method of the present invention. First, when bubbles are added to the excavated soil (FIG. 8A), and further solidified material is added, a volume of waste mud soil corresponding to the volume of the bubbles and the solidified material is discharged to the ground (FIG. 8B). Next, since the volume is reduced in the step of defoaming the bubbles, the waste mud soil is pulled back into the hole (FIG. 8C). This drainage and pullback are performed smoothly, and so that the drainage mud does not flow around the excavation site, and after the solidification process (FIG. 8 (D)), the improved body is positioned at the same level as the ground surface. It is preferable to use the casing shown in FIG.

  As the ground improvement machine having the excavation blade and the stirring blade used in the ground improvement method of the present invention, the conventional type shown in FIG. 1 may be used, or the structure as shown in FIG. It may be.

  In the method of the present invention, since the peripheral speed of the stirring blade is the maximum at the outermost edge, the closer to the outer edge is more efficient for cutting and subdividing the clot. Therefore, it is desirable for mixing to forcibly move and cut a large mass of soil in the direction of the outer edge.

  In order to promote this effect, the shape of the fixed wing is such that the area decreases from the center toward the outer diameter as shown in FIGS. It is considered to guide to the part. By using the fixed wing having such a shape, the earth lump is cut in the radial direction, and good stirring and mixing are performed.

  Furthermore, since the collision speed between the stirring blade and the earth lump is reduced when the earth lump rotates in the same direction as the stirring blade, a fixed blade is provided to suppress this phenomenon. In order to increase, the actual impingement speed of the stirring blade and the clot increases and the relative peripheral speed V increases by rotating the stirring blade counterclockwise with the excavation blade. By using a stirring blade that reversely rotates using a reverse gear attached to the fixed blade shown in FIG. 12, a faster collision speed with the soil mass is obtained, and good stirring and mixing are performed.

  Further, by changing the gear ratio, the peripheral speed of the stirring blade can be increased, and further excellent stirring and mixing can be achieved.

  At present, there is a construction machine in which a plurality of stirring blades are arranged. However, as the blades rotate in the same direction and the earth lump moves upward, the phenomenon of moving in the same direction as the stirring blades tends to be accelerated.

  Therefore, as shown in FIG. 12, by alternately arranging the reversing blades, the rotation direction of the clot is turned, the collision speed is increased with respect to the upper stirring blade, and the above-mentioned drawback is compensated, and further crushing is performed. The stirring efficiency can be increased.

  The ground improvement method of the invention is an excavation process in which the peripheral speed of the stirring blade is rotated at a high speed and the clot is cut and subdivided by the rotational energy of the stirring blade in order to subdivide even in the high plastic clay. And a solidification process step of mixing the mixed state of the solidified material homogeneously.

By making the soil mass and the solidified material into a homogeneous mixture, it is possible to obtain a solidified body having a uniform strength and a continuous strength. As a result, the amount of solidified material added is reduced and the amount of mud is also reduced. be able to. Further, the excavation speed is increased and the construction cycle is shortened. Furthermore, by obtaining a homogeneous solidified body, it is not necessary to carry out an excessive design, and the construction cost can be reduced.
<Management method>
In this ground improvement method, it is very important to perform construction management so that an improved body of required quality can be obtained during construction.

From the above field experiment, it is confirmed that if the unit volume weight of the air-mixed soil is 10.3 kN / m ³ or more and the table flow value (TF value) is 110 mm or more, a ground improvement body of the required quality can be obtained. Therefore, as one of the management methods in this ground improvement method, part of the bubble mixed soil was sampled from the ground during construction, and the unit volume weight of the sampled bubble mixed soil was 10.3 kN / m ³ or more, table flow It is mentioned that the value (TF value) is managed to be 110 mm or more.

Further, according to the above-mentioned field experiment, the unit volume weight of the solidified material mixed soil is 10.3 kN / m ³ or more, the table flow value (TF value) is 110 mm or more, or the unit volume weight is 10.3 kN / m ³ or more. If the shear strength is 8.0 kN / m ² or less, it has been confirmed that a ground improvement body of the required quality can be obtained. As one of the management methods in this ground improvement construction method, a part of the solidified material mixed soil Is collected from the ground, the unit volume weight collected is 10.3 kN / m ³ or more, the table flow value (TF value) is 110 mm or more, or the unit volume weight is 10.3 kN / m ³ or more, vane shear strength Is controlled to 8.0 kN / m ² or less.

  The vane shear strength can be obtained from the sample taken from the ground by the vane shear test, but it can also be obtained from the measured torque of the stirrer without taking it from the ground. One of the management methods of the panel improvement method is to manage the torque value of the agitator.

Claims (24)

  A soil improvement method that includes a drilling process that uses a ground improvement machine having a drilling blade and a stirring blade to cut and subdivide the excavated soil mass excavated by the drilling blade with a rotating stirring blade. The ground improvement construction method characterized by including the excavation process which rotates a stirring blade more than the average peripheral speed required for the cutting | disconnection of a clot, and the solidification process process which mixes a excavation clot and a solidification material corresponding to this.   Solidification process of adding solidified material to the air-blended soil and creating solidified material-mixed soil after the excavation step, including the excavated and mixed step of adding air bubbles or air bubbles and water to the excavated soil mass. The ground improvement construction method of Claim 1 characterized by the above-mentioned.   After the excavation process, including the excavation and mixing process, in which air bubbles and solidification material or air bubbles and water and solidification material are added simultaneously to the excavated soil mass, the solidification material is added to and mixed with the air bubble mixed soil. The ground improvement construction method according to claim 1, further comprising a solidification treatment step for creating soil.   After the excavation process including the excavation and mixing process in which bubbles and solidified material or air bubbles and water and solidified material are added simultaneously to the excavated soil mass, the foam breaker is added and the solidified material mixed soil while foaming. The ground improvement construction method according to claim 1, further comprising a solidification treatment step of forming a slag.   The ground improvement of Claim 2 or 3 including the solidification process process which adds the solidification material which added the foam breaker to the bubble mixing soil, and produces | generates solidification material mixed soil, foaming a bubble. Construction method. The property of the bubble mixed soil includes an excavation step of adjusting so that the unit volume weight is 10.3 kN / m ³ or more and the table flow value (TF value) is 110 mm or more. The ground improvement construction method according to any one of the above. The property of the solidified material mixed soil includes an excavation step and a solidification treatment step in which the unit volume weight is adjusted to be 10.3 kN / m ³ or more and the vane shear strength is 8.0 kN / m ² or less. The ground improvement construction method according to any one of claims 2 to 6. The property of the solidified material mixed soil includes an excavation step and a solidification treatment step in which the unit volume weight is adjusted to be 10.3 kN / m ³ or more and the table flow value (TF value) is 110 mm or more. Item 7. The ground improvement method according to any one of Items 2 to 6.   The ground improvement construction method according to any one of claims 2 to 8, further comprising an excavation and mixing step of adding air bubbles from the excavation blades to create air bubble mixed soil.   The ground improvement method according to any one of claims 1 to 8, wherein the solidifying material is added from an excavation blade or a stirring blade, and includes a solidification treatment step.   The solidification process is included using the solidified material milk of the slurry form which added the water quantity used as 45% or more of the minimum water solidified material ratio which can be pumped as a solidified material, The solidification process process is included. The ground improvement method described in 1.   The ground improvement construction method according to any one of claims 1 to 10, further comprising a solidification treatment step using a powdery solidification material as the solidification material.   The ground improvement method according to any one of claims 2 to 12, wherein bubbles having a median bubble diameter of 100 to 400 µm are used.   The ground improvement construction method according to any one of claims 2 to 13, wherein at least a necessary amount of water that does not eliminate bubbles is added.   The ground improvement construction method according to any one of claims 1 to 14, wherein at least one of cements, limes, and gypsums is used as the solidifying material.   The shape of the rod holding the excavation blade and the stirring blade is rectangular, and includes a solidification process step for creating a gap for allowing air bubbles enlarged by the compressed air and the foam breaker to escape to the ground when the rod rotates. The ground improvement construction method according to any one of claims 1 to 15.   The ground improvement construction method according to any one of claims 1 to 16, wherein a casing is erected on the ground for construction of the mixed soil produced in the excavation process or the solidification process.   The ground improvement method according to any one of claims 1 to 17, wherein a fixed wing having a shape that guides an excavated mass to an outer peripheral portion is used for the ground improvement machine.   The ground improvement construction method according to any one of claims 1 to 18, wherein the ground improvement machine uses a stirring blade that rotates reversely to the excavation blade.   The ground improvement method according to any one of claims 1 to 19, wherein the agitating blades of the ground improvement machine are attached in multiple stages so that they rotate in reverse with each other. A part of the bubble mixed soil is sampled, and the unit volume weight of the collected bubble mixed soil is controlled to be 10.3 kN / m ³ or more and the table flow value (TF value) is 110 mm or more. Management method. A part of solidified material mixed soil is sampled, and the ground volume improvement method is characterized in that the unit volume weight of the collected solidified material mixed soil is controlled to be 10.3 kN / m ³ or more and the table flow (TF value) is 110 mm or more. Management method. A part of the solidified material mixed soil is sampled, and the unit volume weight of the collected solidified material mixed soil is controlled to be 10.3 kN / m ³ or more and the vane shear strength is controlled to 8.0 kN / m ² or less. Management method of ground improvement method. A management method of the ground improvement method, wherein the vane shear strength of the solidified material mixed soil is controlled to 8.0 kN / m ² or less by measuring the torque value of the agitator.

Images