JP2007126817A - Improved ground preparation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved ground preparation method without causing unequal settlement while reducing cost. <P>SOLUTION: This preparation method prepares the ground by this bubble mixed earth by manufacturing the fluid bubble mixed earth by agitating and mixing three members of present position earth, cement being a solidifying material and bubbles being a void forming material in a present position. An improved ground preparation body 38 is prepared by its bubble mixed earth so that the area of an improved earth layer 7 occupied by the bubble mixed earth overflowing from a corresponding place while including the area of its improved column body 1 becomes larger than the area of an improved column body 1 corresponding part for applying agitating mixing processing for manufacturing the bubble mixed earth. In this case, the improved ground preparation body is prepared so that a vertical cross-sectional shape of the single improved ground preparation body 38 becomes a substantially T shape. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improved ground formation method to be performed prior to the construction of a structure such as embankment or concrete on soft ground, and in particular, with a so-called lightweight mixed soil using foam beads or bubbles as a gap forming material. The present invention relates to a method for creating an improved ground.

  When constructing a concrete structure or embankment on soft ground, a floating construction method using a so-called lightweight mixed soil may be used. The concept of this method is that, for example, in the relationship between the building and the ground that supports it, if the building is placed on the trace after removing the ground with the same weight as the building, the stress does not change on the ground below it. In this sense, neither settlement nor expansion occurs, and it is called “floating foundation” (for example, “Homepage of Yoshiaki Yoshiaki”) http://homepage2.nifty.com/yosimi-y/floating.htm ).

  On the other hand, as a technique similar to the floating construction method, for example, a soft ground countermeasure construction method described in Patent Document 1 has been proposed by the present applicant. In this method, the solidified material is mixed with a so-called foamed bead, which is a small piece of foamable synthetic resin, as a void-forming material in the current position soil, and it is lightweight and strong enough to withstand the onboard load. Is a construction method that can secure ground strength while reducing the weight (increased load) corresponding to the construction of the structure on soft ground. That is, by making the mounted load (increased load) and the reduced weight of the current position soil approximately the same, even if the structure is built on soft ground, it can be considered that there was no increased load due to it. It is a soft ground countermeasure method that can create

  In addition, as a means for doing so, a lightweight material with sufficient strength to withstand the overload associated with construction of structures and embankments by stirring and mixing with the current position soil while discharging the gap forming material and the solidified material into the current position soil. In constructing the soil, construction should be made so that the reduced weight associated with the lighter soil at the current location is almost equal to the load on top of the soil. A part is covered with the increased amount of lightweight soil created by stirring and mixing while discharging void formation material and solidification material into the soil at the current position of the bottom of the embankment body, and light weight with the strength necessary for embankment body It is going to create soil.

In other words, in the former case, construction should be made so that the reduced weight associated with the lighter soil at the current position is almost equal to the loading load, and in the latter case, it is necessary to construct the embankment with a predetermined height. It is a soft ground countermeasure construction method that reduces the weight of the lower area (bottom part) of the structure and embankment in any case.
JP 2004-300915 A

  According to the former technique described in the above-mentioned Patent Document 1, since it is a technique of constructing so that the reduced weight associated with lightening of the soil and the load on the structure or embankment body becomes substantially equal, it corresponds to the reduced weight. It is necessary to replace the current position soil (raw soil) for the volume with light soil. Accordingly, there is a problem that the excavation depth (replacement depth) in the lower region of the structure or embankment increases with an increase in the upper load, leading to an increase in cost.

  In addition, according to the latter technique described in the above-mentioned Patent Document 1, since it is a technique that can cover the increased volume of the lightweight soil that created the volume of the embankment body, considering that the lightweight soil has fluidity. You will need a formwork to increase the amount of increase. Therefore, although it is an optimal technique for a low embankment with a relatively low embankment height (2-3 m) assuming that the formwork is used, a high embankment with a relatively large embankment height (4-5 m or more) ), It takes a lot of time and money to assemble the formwork, and because it is in-situ mixing, the formwork interferes with the work machine for that purpose, and the height of the embankment and the increase in the weight of the lightweight soil There was a problem such as causing uneven settlement of the embankment as the difference occurred.

  The present invention has been made paying attention to such problems, and in particular, an object of the present invention is to provide an improved ground preparation method that does not cause uneven settlement while reducing costs.

  The invention according to claim 1 is to produce a void-forming material mixed soil having fluidity by stirring and mixing the current position soil, the solidified material and the void-forming material at the current position, and mixing the void-forming material. When creating the ground with soil, the void forming material mixture overflowing from the stirring and mixing location including the area of the stirring and mixing location rather than the area of the stirring and mixing location that is subjected to the stirring and mixing treatment to produce the void forming material mixed soil The improved ground is created with the void forming material mixed soil so that the area occupied by the soil is larger.

  As the void forming material mentioned here, for example, the use of expanded beads such as expanded polystyrene as described in claim 6 or bubbles as described in claim 7 is assumed.

  In this case, as described in claims 2 and 3, a single improved ground formation formed by the void forming material mixed soil at the stirring and mixing portion and the void forming material mixed soil overflowing from the stirring and mixing portion. It is desirable that the vertical cross-sectional shape is substantially T-shaped or substantially inverted U-shaped.

  More specifically, as described in claim 4, a single improved ground formation is formed by the void forming material mixed soil at the stirring and mixing location and the void forming material mixed soil overflowing from the stirring and mixing location. And as an independent thing, it shall construct so that two or more of this improved ground formation object may be arranged in parallel.

  Or, as described in claim 5, the improved ground formation formed by the void forming material mixed soil at the stirring and mixing location and the void forming material mixed soil overflowing from the stirring and mixing location as a single one, It shall be constructed so as to connect two or more of this improved ground formation.

  In order to produce a void forming material mixed soil having fluidity by stirring and mixing the current position soil, the solidified material, and the void forming material at the current position, the work system construction machine as described in claim 8 In addition to excavation of the current position soil, the stirring and mixing process of the current position soil with the solidified material and the void forming material is performed.

  More specifically, as described in claim 9, an endless chain is wound between the driving wheel at the upper part of the frame of the stirring mixer and the driven wheel at the lower part of the frame, and the chain is moved in the vertical direction. By doing so, in addition to excavation of the current position soil, stirring and mixing processing of the current position soil and the solidifying material and the void forming material is performed.

  Therefore, in at least the invention described in claim 1, after adding the above-mentioned void forming material such as foam beads and bubbles in addition to the solidified material to the current position soil, these three are stirred and mixed at the current position. When the void forming material mixed soil having fluidity is produced, the soil in the current position is inevitably made lighter and increased. Therefore, the void formation so that the area occupied by the void-forming material mixed soil overflowing from the stirring and mixing location, including the area of the stirring and mixing location, is larger than the area of the stirring and mixing location where the stirring and mixing treatment is performed. The improved ground will be created with mixed soil. As a result, the soil volume to be agitated and mixed, and the agitated and mixed volume is reduced as compared with the conventional method, but the soil volume and the created volume are increased. In particular, when constructing an embankment body on the improved ground, a portion of the embankment volume is covered by the increased void forming material mixed soil, so the embankment volume required for the embankment body is relatively small. It will be over.

  According to the first aspect of the present invention, since the so-called lightweight soil-improved improved ground can be created with the minimum necessary amount of agitated and mixed soil, the cost can be greatly reduced as compared with the prior art. The improved ground will not cause subsidence.

  FIG. 1 shows an outline of an improved ground as a more specific embodiment of the present invention.

Here, a large number of improved pillars 1, 1... Are constructed at an equal pitch in the ground at an area ratio of 20% with respect to a ground area of width 18m, extension 90m, and area to be improved 1620m ^2. The example in the case of embankment with a height of 5 m on the pillars 1, 1. The improved column 1 is a 2 m × 2 m square prism, and its depth (height) is 10 m. The embankment body 2 has a trapezoidal cross section with a base of 22 m and an upper side of 12 m. In the drawings after FIG. 1, the dimensions of each part are displayed in mm (mm) units.

  In carrying out the construction, as shown in FIG. 2A, the formwork 3 is erected on the ground G so as to surround the area to be improved and attached to the tip of the arm 5 of the backhoe 4 that functions as a base machine. Agitating and mixing machine 6 is prepared, and the agitating and mixing machine 6 sequentially penetrates into the ground, while excavating the current position soil (raw soil), for example, cement milk as a solidifying material and bubbles as a void forming material, respectively. Each of the improved pillars 1, 1... Is constructed by discharging into the ground and stirring and mixing these three while making a so-called lightweight soil.

  Here, the mixing ratios of the solidification material and the bubbles to the current position soil are adjusted in advance so that the volume increase rate after the so-called lightweight soil is doubled.

  Although the improved pillars 1, 1... Shown in FIG. 2 are independent of each other, the weight is increased along with the lightening of the soil by mixing and stirring the current position soil, the solidified material, and the bubbles. The increased amount overflows upward, and on the ground G, an improved soil layer 7 is formed on the upper side of each of the improved pillars 1, 1. become. Needless to say, the soil quality of the improved soil layer 7 is the same as that of the improved pillars 1, 1,... Therefore, the amount of lightweight soil that has increased with the construction of the improved pillars 1, 1, and overflowed upward, that is, the volume of the improved soil layer 7 is equal to the total volume of each improved pillar 1, 1. become.

  In this way, if a large number of improved pillars 1, 1... Are constructed together with the improved soil layer 7, as shown in FIG. 2 (B), after removing the mold 3 surrounding the area to be improved, The earth for embankment is carried in with the dump truck 8 etc., raised on the improved soil layer 7, and spread with a bulldozer 9 etc., and the embankment body 2 is formed as shown in FIG.

  This is organized as follows.

・ Area to be improved 90m × 18m = 1620m ²
・ Agitation soil volume for construction of improved column 1 1620 m ² × 20% × 10 m = 3240 m ³
-Total creation volume improved as lightweight soil = Light soil volume converted into improved column 1 + Light soil volume converted into improved soil layer = 3240m ³ + 3240m ³ = 6480m ³
-Amount of soil to be carried in to form the embankment body 2 = (trapezoidal cross-sectional area of the embankment body 2-cross-sectional area of the improved soil layer 7) x length of the embankment body 2 = (85 m ² -36 m ² ) × 90m = 4410m ³
Here, for comparison, a conventional construction method in the case where the embankment body 2 having the same cross-sectional shape as in FIGS. In addition, in the drawings such as FIGS. 4 and 5, the dimensions of each part are indicated in mm (mm).

In the conventional construction method shown in FIG. 4, as a countermeasure against an increased load due to the formation of the embankment body 12, a cylindrical cement soil having a ratio of 20% to the ground area having a width of 18 m, an extension of 90 m and an area to be improved of 1620 m ^2. Piles (8m length from 2m to 10m below the ground) 11, 11 ... are constructed in the ground at an equal pitch, and 5m high embankment is applied to the cement soil piles 11, 11 ... The example in the case of constructing the body (bank body) 12 is shown. For the construction of the cement soil piles 11, 11,..., A deep stirring mixer 10 is used as shown in FIG. Further, the cement soil piles 11, 11... Constructed by the deep stirring mixer 10 have a diameter of 2.26 m so that the cross-sectional area is the same as that of the improved column 1 of FIGS. Moreover, the cross-sectional shape and cross-sectional area of the embankment body 12 are the same as what was shown in FIG.

  If the embankment body 12 is formed on the cement soil piles 11, 11... As shown in FIG. 5 (B), there is a possibility that uneven settlement will occur. Therefore, the upper surface of the cement soil piles 11, 11. A ground improvement layer 13 having a depth of 2 m was formed so as to be flush with the ground G. In addition, the same stirring mixer 14 as FIG. 2 was used for creation of this ground improvement layer 13. As shown in FIG. After that, as shown in FIG. 6, the embankment body 12 having a predetermined height was formed on the ground improvement layer 13 with a bulldozer 8 or the like.

  This is organized as follows.

・ Area to be improved 90m × 18m = 1620m ²
・ Agitation soil volume for construction of cement soil pile 11 1620 m ² × 20% × 8 m = 2589 m ³
・ Ground improved total creation volume = Improved soil volume converted to cement soil pile 11 + Improved soil volume converted to ground improved layer 13 = 2592m ³ + 3240m ³ = 5832m ³
-Amount of soil to be loaded necessary to create the embankment body 12 = trapezoidal cross-sectional area of the embankment body 12 x length of the embankment body 12 = (85 m ² × 90 m = 7650 m ³
Here, Table 1 summarizes the previous embodiment and the conventional method as a table for comparison.

  As is apparent from Table 1, according to the present embodiment, the amount of soil to be stirred and the amount of created soil as a result of work are greatly increased, while the embankment body 2 is created. As a result, the amount of soil required for this is greatly reduced, and as a result, the construction cost can be greatly reduced.

  Next, more detailed examples based on the above construction method will be described.

When constructing a structure having a weight of 5 t / m ² on soft ground with unit volume weight ρt = 1.5 t / m ³ of the current position soil, a void forming material and a solidifying material are mixed in the current position soil. A case where a lightweight soil having a unit volume weight ρt = 1.0 t / m ³ , that is, a void-forming material mixed soil, is created by stirring.

  Here, it is assumed that bubbles are used as the void forming material, and as a result, the void forming material mixed soil is the bubble mixed soil. The definition of each term is as follows.

・ Bubble mixed soil: Lightweight soil created by adding air milk (solidified material + water + bubbles) to the current soil and mixing and stirring. Use).

-Foaming material: Diluted solution of water added to foaming agent (diluted 15 times in this case)
・ Air bubbles: Foam made by adding air to foamed material diluted 15 times (in this case, 20 times foaming)
-Foam milk: a slurry-like material obtained by adding a foaming material to cement milk-Air milk: a foam-like mixed material in which compressed air is involved in the foam foam milk and unit volume weight ρt = 1.5 t / m the formulation examples in the case of ³ of the current position soil and air bubbles mixed soil of specific weight ρt = 1.0t / m ³ shown in Table 2.

  Moreover, each value obtained by the said mixing | blending example is as follows.

・ Bubble mixed soil weight: Total weight of (raw soil + solidifying material + water + bubbles) = 1.5 + 0.156 + 0.312 + 0.0316 = 2.0 t
・ Bubble mixed soil strength: uniaxial compressive strength in the room (qu28)
= 100 kN / m ² or more ・ Bubble mixed soil volume: Total volume of (raw soil + solidified material + water + bubbles) = 1.0 + 0.052 + 0.312 + 0.632 = 2.0 m ³
-Unit volume weight of bubble mixed soil: bubble mixed soil weight / bubble mixed soil volume = 2.0 t / 2.0 m ³ = 1.0 t / m ³
・ Volume increase rate of raw soil and bubble mixed soil: Bubble mixed soil / raw soil = 2/1 = 2 times Note that the flow value of the bubble mixed soil immediately after stirring and mixing is 130 mm or more as the value of the table flow value. Shall be confirmed.

  FIG. 7 shows an outline of a system for the above-mentioned bubble mixed soil treatment. In this system, a foaming material and cement milk (a slurry in which cement is dissolved in water) are mixed with a foaming material and a solidifying material in a slurry plant 15 having a mixer (not shown) as a main element, and the foaming material milk is mixed. After the production, the foamed milk is pumped to the stirring mixer 6 side by the grout pump 16 and the high-pressure hose 17. In addition, 18 is a foaming agent tank, 19 and 20 are water tanks, 21 is a solidification material (cement) silo, 22 is a motor generator, and 23 is a compressor. The agitator-mixer 6 is, for example, a backhoe 4 which is a working or excavating construction machine and is mounted at the tip of the arm 5 as a base machine (base machine), and penetrates into the ground as will be described later. Then, while excavating the current position soil, air milk is discharged from the material discharge port at the tip, and agitation and mixing with the current position soil is performed.

  8 and 9 show the details of the agitating mixer 6, and the agitating mixer 6 itself is disposed between a driving wheel 26 at the upper part of a frame 25 with a bracket 24 and an upper driven wheel 26 and a driven wheel 27 at the lower part. An endless drive chain 28 is wound and a plurality of stirring blades 29 are mounted on the outer periphery of the drive chain 28 at a predetermined pitch. A material discharge port 30 is provided at the lower end (tip) of the frame 25. Then, when the hydraulic motor 31 provided at the upper part of the frame 25 is started, each stirring blade 29 moves around together with the drive chain 28, and at the same time, it penetrates into the ground by the thrust of the backhoe 4 itself. In parallel with the excavation of the earth and sand, a stirring and mixing process with the air milk is performed.

  The bracket 24 at the upper end of the frame 25 of the stirring mixer 6 is provided with a foaming device 32, and the material discharge port 30 and the foaming device 32 described above are arranged along the frame 25 of the stirring mixer 6 itself. The foaming device 32 is connected to the grout pump 16 via the high-pressure hose 17 (see FIG. 7) described above. Then, foaming milk is promoted by introducing both the foaming material milk pumped by the grout pump 16 and the compressed air from the compressor 23 to the foaming device 32 to actively form foam-like air milk, The air milk is discharged from the material discharge port 30 at the tip. Reference numeral 34 denotes a pipe for introducing compressed air.

  As shown in FIG. 10, the foaming device 32 has a tapered housing 35 whose diameter is reduced downward as a main element, and the upper end of the housing 34 has the high-pressure hose 17 and FIGS. An introduction pipe 36 to be connected to the compressed air introduction pipe 34 is extended, and an outlet pipe 37 to be connected to the pressure feed pipe 33 in FIGS. Yes. Further, in the housing 35, a plurality of so-called punching plate perforated plates 38 in which a number of rectangular or round holes are punched and formed in a metal substrate, for example, as a foaming promoting material are stacked and arranged with a predetermined gap therebetween. Of course, a metal or resin mesh plate may be used instead of the punching plate. As described above, the foamed milk and the compressed air introduced into the foaming device 32 pass through the porous plate 38 to promote the foaming, thereby producing air milk. The so-called foam-shaped air milk is discharged from the material discharge port 30 at the tip of 6.

  Here, FIG. 11 schematically shows a process in which the foaming agent and the cement as the solidifying material are converted into air milk through foaming material milk and finally become bubble mixed soil. This process will be described in order as follows.

  (1) As shown in FIG. 7, first, a batch of water is put into the slurry plant 15 from the water tank 19 or 20, and then a batch of cement is lightened from the solidifying silo 21 to the slurry plant 15. The mixture is mixed and kneaded to produce cement milk.

  (2) A foaming material diluted 15 times in advance with the foaming agent from the foaming agent tank 18 and the water from the water tank 19 or 20 is put into the slurry plant 15 and kneaded with cement milk to produce the foaming material milk. Manufacturing.

  (3) The foamed milk is pumped by the grout pump 16 to the foaming device 32 on the stirring mixer 6 side.

  (4) In the foaming device 32, the compressed air is introduced into the foamed milk together with the foamed milk that has been fed as described above to promote the foaming, and then the material discharge port at the tip of the stirring mixer 6 is used. It is made to discharge from 30 as foam-like air milk.

  (5) In situ soil and air milk are agitated and mixed at the current position to form bubble mixed soil.

  Here, it is assumed that a 2 m × 2 m square prismatic improved pillar 1 is constructed with the above-described bubble mixed soil from the ground to a depth of 10 m as shown in FIG. The mold 3 is erected in advance so as to surround the area to be improved.

The composition of the solidified material per 1 m ³ of the raw earth for producing air milk to be the improved pillar 1 is as shown in Table 2 and is 0.156 t of solidified material (cement), 0.312 m ^{3 of} water, The foaming material is 0.0316 m ³ . Further, the unit volume weight ρt of the bubble mixed soil is 1.0 t / m ³ (provided that ± 0.1), and the uniaxial compressive strength qu of the bubble mixed soil is 50 kN / m ² (however, the on-site indoor strength ratio 1 / Field target strength when 2).

  As shown in FIGS. 12A and 12B, while the air milk is being discharged from the material discharge port 30 (FIG. 9) at the tip of the stirring mixer 6, the stirring mixer 6 is penetrated into the ground. While excavating the position soil, a stirring and mixing process with air milk is performed, and a 2 mm × 2 m square and 10 m deep prismatic improved column body 1 is constructed with the bubble mixed soil. In this case, it should be confirmed in advance that the specific gravity of the air milk is 0.5 ± 0.05. Moreover, although the treated soil immediately after the stirring and mixing treatment exhibits fluidity, it is also confirmed that the flow value of the treated soil is 130 mm or more as a table flow value.

The stirring and mixing area A at the current position is 2 m × 2 m = 4 m ² , and the stirring and mixing depth at the current position is 10 m. Therefore, the amount of the stirring and mixing soil at the current position is 4 m ² × 10 m = 40 m ³ . In this case, since the volume increase ratio of the bubble mixed soil with respect to the raw soil is twice as described above, the 40 m ³ raw soil is agitated and mixed with the air milk to increase the volume to 80 m ³ bubble mixed soil. Is done. Then, the increased amount of bubble mixed soil overflows from the area to be improved of area A, and is 4.5 m square above the improved pillar 1 and surrounded by the mold 3 as shown in FIG. The improved soil layer 7 having a depth of 1.98 m is formed in the area B of the above. In other words, if the prismatic improved column 1 and the improved soil layer 7 are not distinguished, as shown in (A) and (B) of FIG. Thus, an improved ground formation body 38 having a substantially T-shaped cross section is formed.

  When the improved soil layer 7 is formed on the improved pillar body 1 in this way, the mold 3 is disassembled and removed after a curing period of, for example, about 1 week to 4 weeks.

  That is, in Example 1, the planar shape is 2 m × 2 m square (area A) and the depth is 10 m on the improved pillar body 1 made of bubble mixed soil, and the planar shape is 4.5 m × 4.5 m square (area B). The improved soil layer 7 made of the same bubble-mixed soil having a depth of 1.98 m is formed, and the area ratio is 20.25 / 4≈5.06, which satisfies A <B. In Example 1, the area B is 5.06 times the area A. However, this value varies depending on the properties of the raw soil, the volume increase rate of the bubble mixed soil, or the mixing depth of the agitation. Therefore, it is desirable that B / A be at least 1.2 times or more.

  FIG. 14 shows a second embodiment. In the second embodiment, on the premise of the construction method of the first embodiment, a large number of improved ground formation bodies 38 that are independent from each other are arranged in parallel at a predetermined pitch with a regularity, and a large number of these improved ground formation bodies are arranged. The embankment body 12 is formed on 38, 38.

  FIG. 15 shows a third embodiment. In the third embodiment, on the premise of the construction method of the first embodiment, a large number of improved ground formation bodies 38, 38,... , 38 are connected to each other, and the embankment body 2 is formed on the many improved ground formation bodies 38, 38,.

  FIG. 16 shows a fourth embodiment. In the fourth embodiment, on the assumption of the construction method of the third embodiment shown in FIG. 15, the upper surfaces of the improved soil layers 7 in the many improved ground formation bodies 38, 38,. For example, a concrete building 39 is constructed on a large number of improved ground formation bodies 38, 38,.

  FIG. 17 shows a fifth embodiment. In the first embodiment, as shown in FIG. 13, an example is shown in which an improved ground structure 38 having a substantially T-shaped cross section is formed or constructed with the improved pillar 1 and the improved soil layer 7. Thus, in the fifth embodiment, for example, as shown in FIG. 17, a hollow prismatic improved pillar body 51 is constructed in the ground, while an improved soil layer 57 is formed in such a form that a lid is placed on the upper side. Thus, the improved ground formation body 58 having a substantially inverted U-shaped cross section as a whole is formed or constructed.

  FIG. 18 shows a sixth embodiment. In this sixth embodiment, on the premise of the construction method of the fifth embodiment, a large number of improved ground formation bodies 58, 58... Independent from each other are arranged side by side at a predetermined pitch with regularity. The embankment body 2 is formed on the ground formation bodies 58, 58.

  FIG. 19 shows a seventh embodiment. In the seventh embodiment, on the premise of the construction method of the sixth embodiment, a large number of improved ground formation bodies 58, 58... Are arranged with regularity at a predetermined pitch, and adjacent improved ground formation bodies 58 are arranged side by side. , 58 are connected to each other, and the embankment body 2 is formed on the large number of improved ground formation bodies 58, 58.

  FIG. 20 shows an eighth embodiment. In the eighth embodiment, on the premise of the construction method of the seventh embodiment shown in FIG. 19, the upper surfaces of the improved soil layers 57 in many improved ground formation bodies 58, 58. For example, a concrete building 39 is constructed on a large number of improved ground formation bodies 58, 58.

  Here, in each of the above-described embodiments, the case where air bubbles are used as a gap forming material for lightening the current position soil is described. Instead, for example, beads such as foamed polystyrene and foamed polypropylene are used. It is also possible to use so-called expanded beads, which are small pieces of expandable synthetic resin represented by

In this case, foam beads and cement as a solidifying material are mixed in advance, and this mixture is discharged into the ground from the material discharge port 30 of the agitating mixer 6 described above, and water is simultaneously discharged. Thus, a mixed lightweight soil having fluidity is created by stirring and mixing the present position soil, foam beads, solidifying material and water. In general, it was stirred and mixed to solidifying material 50kg and expanded beads 0.3～2.0M ³ to the current soil 1 m ³ per a mixed lightweight soil weight 0.6~1.5t / m ³ Is desirable. In addition, the mixing lightweight earthwork method in the present position using foam beads as a space | gap formation material is detailed in Unexamined-Japanese-Patent No. 2004-300915.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the outline of the improved ground created by the method of this invention, (A) is plane explanatory drawing under the ground, (B) is sectional explanatory drawing of the created improved ground. (A), (B) Both process explanatory drawing which shows the creation procedure of the improved ground of FIG. It is process explanatory drawing of the creation procedure following (B) of Drawing 2, (A) is a section explanatory view of the created improved ground, and (B) is a plane explanatory view under the ground of the created improved ground. It is a figure which shows an example of a conventional construction method for the comparison with creation of the improved ground in FIG. 1, (A) is the cross-sectional explanatory drawing, (B) is the plane explanatory drawing under the ground of the same figure (A). Process explanatory drawing which shows the creation procedure of the improved ground of FIG. 4 both (A) and (B). Process explanatory drawing of the creation procedure following (B) of FIG. The schematic explanatory drawing of the whole bubble mixing soil construction system for creation of the improved ground of FIG. The enlarged view which shows the detail of the stirring mixer in FIG. Side surface explanatory drawing of FIG. Explanatory sectional explanatory drawing of the foaming apparatus in FIG. Explanatory drawing which shows the process until cement which is a foaming agent and a solidification material finally turns into foam mixed soil through the state of foaming material milk and air milk. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows Example 1 of a more concrete creation method, (A) is plane explanatory drawing in the case of producing the improved ground formation body which consists of an improved pillar and an improved soil layer independently, (B) is the figure. Cross-sectional explanatory drawing of (A). (A) is plane explanatory drawing of the improved ground formation body created in FIG. 12, (B) is the cross-sectional explanatory drawing similarly. It is a figure which shows Example 2 of the more concrete creation method, (A) is plane explanatory drawing, (B) is the cross-sectional explanatory drawing. It is a figure which shows Example 3 of the more concrete creation method, (A) is plane explanatory drawing, (B) is the cross-sectional explanatory drawing. Cross-sectional explanatory drawing which shows Example 4 of a more concrete creation method. FIGS. 13A and 13B are diagrams illustrating a modified example of FIG. 13 as Example 5 of a more specific creation method, where FIG. It is a figure which shows Example 6 of the more concrete creation method, (A) is plane explanatory drawing, (B) is the cross-sectional explanatory drawing. It is a figure which shows Example 7 of the more concrete creation method, (A) is plane explanatory drawing, (B) is the cross-sectional explanatory drawing. Cross-sectional explanatory drawing which shows Example 8 of a more concrete creation method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Improved column body 2 ... Embankment body 6 ... Stir mixer 7 ... Improved soil layer 15 ... Slurry plant 25 ... Frame 26 ... Drive wheel 27 ... Drive wheel 28 ... Drive chain 29 ... Stir blade 30 ... Material discharge port 32 ... Foaming Equipment 38 ... Improved ground formation 51 ... Improved pillar 57 ... Improved soil layer 58 ... Improved ground formation

Claims (9)

While producing the void-forming material mixed soil having fluidity by stirring and mixing the current position soil and the solidified material and the void-forming material at the current position, when creating the ground with this void-forming material mixed soil,
The area occupied by the void-forming material mixed soil overflowing from the stirring and mixing portion while including the area of the stirring and mixing portion is larger than the area of the stirring and mixing portion where the stirring and mixing process is performed to produce the void-forming material mixed soil. An improved ground preparation method, characterized in that the improved ground is created with the void forming material mixed soil so as to be large.   The vertical cross-sectional shape of a single improved ground formation formed by the void forming material mixed soil at the stirring and mixing portion and the void forming material mixed soil overflowing from the stirring and mixing portion is substantially T-shaped. The improved ground building method according to claim 1, wherein the ground is formed.   The vertical cross-sectional shape of a single improved ground formation formed by the void-forming material mixed soil at the stirring and mixing location and the void-forming material mixed soil overflowing from the stirring and mixing location is substantially inverted U-shaped. 2. The improved ground preparation method according to claim 1, wherein   Two or more improved ground formations are formed as a single and independent improvement ground formation formed by the void formation material mixed soil at the stirring mixing location and the void formation material mixed soil overflowing from the stirring mixing location. The improved ground creation method according to any one of claims 1 to 3, wherein the ground is constructed in parallel.   Two or more improved ground formations are connected with a single improved ground formation formed by the void formation material mixed soil at the stirring mixing location and the void formation material mixed soil overflowing from the stirring mixing location. The improved ground formation method according to any one of claims 1 to 3, wherein the ground is formed as described above.   The improved ground building method according to any one of claims 1 to 5, wherein foam beads are used as the gap forming material.   The improved ground preparation method according to any one of claims 1 to 5, wherein bubbles are used as the gap forming material.   Stir mixing at the tip of the arm of the work system construction machine to produce a void forming material mixed soil having fluidity by stirring and mixing the current position soil, solidified material and void forming material at the current position. The improvement according to any one of claims 1 to 7, wherein the machine is penetrated into the ground, and in addition to excavation of the current position soil, a stirring and mixing process of the current position soil, the solidified material and the void forming material is performed. Ground preparation method.   An agitator / mixer wraps an endless chain between the drive wheel at the top of the frame and the driven wheel at the bottom of the frame, and moves the chain around in the vertical direction to excavate the current position soil as well as the current position soil. The improved ground preparation method according to claim 8, wherein a stirring and mixing process is performed with the solidified material and the void forming material.

Images