JP3017181U - Mixing and stirring equipment used for ground improvement method - Google Patents

Abstract

(57) [Summary] [Structure] A pipe-shaped outer tube 1 equipped with a drill bit 9 and a stirring blade 6 near the lower end, and vertically movable inside the outer tube 1,
And a stirrer shaft composed of an inner tube 2 that is freely retractable from the bottom of the outer tube 1, and a stabilizing treatment material supply passage 10 is provided between the outer tube 1 and the inner tube 2, and the inside of the inner tube 2 is A drainage pump 5 is provided near the lower end of the inner pipe 2 for sucking the surrounding water through the drainage passage 10 and discharging the water from the upper end near the lower end of the inner pipe 2. The configuration of the provided mixing and stirring device A. [Effect] In the mixing and agitation method, the volume of the ground increases due to the addition of the stabilizing material, but by balancing the increase in the amount of water discharged, the lateral flow and displacement of the ground can be balanced. Can be prevented.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a mixing and stirring device used in a ground improvement method. More specifically, in the slurry-type or powder-type deep mixing agitation method, which is one of the most versatile and highly reliable methods among various ground improvement methods, a stabilizing agent is added and injected into the soft ground. Ground improvement work method that prevents lateral flow due to expansion of the ground volume of the construction site, thereby preventing the surrounding ground and underground buried objects and structures from being affected. The present invention relates to a mixing and stirring device used for.

[0002]

[Prior art]

 The deep-layer mixing and agitation method is to add a stabilizing agent such as cement-based solidifying material in the form of slurry or powder into soft sandy soil or cohesive soil, and mechanically mix and agitate with the original soil. CaO (quick lime, calcium oxide), SiO which are the main components of the stabilizing material in the mixing and stirring process.₂ H (silica, silicon oxide) etc. ₂ It is a method of reacting with O (water) to form various hydration products, and solidifying and hardening to form an improved body or improved portion having high strength. Therefore, it is necessary to add an appropriate amount of stabilizing material to the raw ground soil and mix and stir it in order to carry out the deep mixing and stirring method. However, injecting and adding a considerable amount of stabilizing material to the ground increases the volume of the ground, and as a result pushes the surrounding ground and underground buried objects and structures laterally. , Or the problem of displacement occurs. Therefore, recently, it is necessary to find a construction method that does not increase the volume of the ground even if ground improvement work is performed by adding a stabilizing material and mixing and stirring to form a hydrated product in the ground. Has been highlighted as an urgent issue.

As one of the methods currently taken to solve this problem, there is a soil discharging method using a screw rod (see Japanese Patent Publication No. 4-57805). This method employs a device in which a screw is provided above the stirring blade on the stirring shaft itself with the stirring blade attached to the lower end. Further, in a biaxial or multiaxial type construction machine, an apparatus in which a screw rod is provided between the stirring shafts is used. These devices discharge soil around the screw rod as the stirring shaft rotates while descending and ascending, and produce an amount of soil approximately commensurate with the volume increase of the improved part ground caused by the addition of the stabilizing agent. Used to eliminate.

[0004]

[Problems to be solved by the device]

 This method seems to be very rational at first glance, but there are some problems when it comes to actual construction. The first is that it is very difficult to accurately control the amount of soil discharged by the screw so that it is almost commensurate with the volume increase of the improved ground caused by the addition of the stabilizing material. The amount of soil that a screw rod can actually eliminate depends not only on the screw diameter, pitch, rotation speed, and other complex relationships, but also on the nature of the soil to be eliminated, and therefore the soil that can be eliminated. It is not possible to easily predict the amount of Actually, it is only after the construction is completed that the discharged soil is transported to the screw and appears on the ground, so the approximate amount of discharged soil can be estimated. It is impossible without skill.

Another reason why it is difficult to control the amount of soil to be discharged is that the amount of soil to be discharged by one mixing stirring method (one place) greatly varies depending on the amount of the stabilizer added. Is. For example, in the case of adding the case with 300kg you added 150kg stable processing member relative to the initial ground earth 1.0 m ^3, addition, soil amount of ground improvement part you increased by mixing and stirring the matter of course However, the latter is much more common. In other words, the required amount of soil removal is much higher in the latter case, and in order to respond to this, the screw used in the latter case must have a larger amount of soil removal than the screw in the former case. I won't. Similarly, when two or more constructions (two locations) are installed in the mixing and stirring method so that they overlap each other, the required amount of soil removal will inevitably change for each construction site. If a screw of appropriate work and size is not used, or if the amount of soil removed is smaller than the increase in the volume of the improved ground, the effect on the surrounding ground cannot be completely prevented. It will leave a lateral flow or transition. On the contrary, when the amount of soil discharged is larger than the amount of increase in volume, ground subsidence will occur at the improved construction site.

Secondly, as a second problem, most of the earth removing work is performed after the stabilizer is added and injected into the ground from the tip of the stirring blade attached to the lower end of the stirring shaft or a portion close to it. Therefore, the soil to be removed is not yet sufficiently mixed and stirred, but it contains some stabilizers. In other words, some of the required amount of pre-designed stabilizing agent added is directly removed from the ground without participating in the hydration reaction. As a result, the resulting improver will be less than the target strength because it will be constructed with a slightly less than the required amount of stabilized material. In order to compensate for this, it is necessary to increase the amount of stabilizing agent added in advance in anticipation of loss, which is not only technically quite difficult but also economically disadvantageous.

[0007] In addition, as a third problem, the soil that has adhered to the screw and is pulled up must be stripped off almost completely for each screw, but this work is quite troublesome. is there. Moreover, the discharged soil accumulates like piles at the position of the agitation shaft or screw, so the worker must remove it diagonally from the side. On the other hand, if the soil discharged between the screws cannot be completely stripped off and some remains, the amount of soil discharged at the next point will naturally be small. The fourth problem is the treatment of the soil removed from the screw, and this soil is naturally treated as construction soil, which requires considerable expense and labor. In addition, recently, there are various problems in terms of pollution.

In any case, although the screw excavation method which is currently considered seems to be rational at first glance, there are some problems as described above in detail. The most important problem among them is, of course, the first point, the control of the amount of soil discharged.

The present invention has been made in order to solve the above-mentioned various problems, and it is relatively easy to reduce the amount of reduction in the method of decreasing the amount of increase in the ground volume due to the addition of the stabilizing agent. The first object is to provide a mixing and stirring device that can be controlled to the above. Furthermore, the present invention provides a ground improvement device that can reduce the volume increase while leaving the injected stabilizing material as little as possible, that is, leaving it in the ground. Furthermore, it is easy to construct and considers environmental protection. It is a technical issue to provide such a mixing and stirring device.

[0010]

[Means for Solving the Problems]

 In order to solve the above problems, the mixing and stirring apparatus used in the ground improvement method of the present invention is a pipe-shaped stirring shaft equipped with an excavating bit and stirring blades near the lower end, and a stable stirrer provided inside each of the stirring shafts. It is composed of a treatment material supply passage and a drain passage, and a pump for sucking water from the lower end through the drain passage and discharging the water from the upper end. In that case, it is preferable that the agitation shaft is a double pipe consisting of an inner pipe and an outer pipe, a supply passage for the stabilizing material is provided between the inner pipe and the outer pipe, and a drain passage is provided inside the inner pipe. Yes. The drainage pump is preferably installed near the lower end of the drainage passage or near the lower end of the inner pipe. Further, it is preferable that the inner pipe is provided so as to be vertically movable with respect to the outer pipe so that the lower end thereof can project from the lower end of the stirring shaft. Further, it is preferable to provide a screen or a filter that does not allow water and soil particles and cement particles to pass under the drainage passage. Further, it is preferable to provide a flow meter for measuring the flow rate of water rising inside the drainage passage.

[0011]

[Action]

 First, the direct operation of the device of the present invention will be described. Stabilizing material for mixing and stirring flows down through the supply pipe provided inside the stirring shaft, and is added and injected into the ground through the discharge port at the lower end of the stirring blade. However, the discharge is in the process of pulling up the stirring shaft (and stirring blade), and when the stirring shaft (and stirring blade) in the first half descends, the stirring blade mainly stirs the ground around the shaft and destroys tissues such as cohesive soil. And make a mess. When the tip of the agitating blade reaches a predetermined depth and sufficient agitation is completed for the ground around the shaft at that depth, the addition of the stabilizing treatment material from the discharge port at the lower end of the agitating shaft is started. To be done. However, up to this point, the pump for drainage has not started yet.

[0012] When the stirring shaft descends to the lower end, the stabilizing treatment material starts to be discharged from the discharge port at the lower end of the stirring shaft, and the mixing and stirring by the stirring blade starts. After that, the stirring shaft is gradually raised. The pump starts operating when the stirring shaft is lifted up to a certain height B from the bottom of the hole, and the excess water filling the soil around the stirring shaft is discharged through the drain pipe. As a result, the pump rises while discharging the excess water remaining in the improved part ground after the mixing and stirring are sufficiently performed and the hydration reaction of the hardening material such as cement-based solidifying agent and water is started. I will go.

In a device using a double tube, the stirring shaft is lowered while the inner tube is housed inside the outer tube. When it reaches the bottom of the hole from between the inner pipe and the outer pipe, it mixes and stirs while raising it, but the stabilizing treatment material, which is the mixing and stirring, flows down between the inner pipe and the outer pipe, and near the lower end of the stirring shaft. It is added and injected into the ground from the discharge port. When ascending, leave only the inner pipe at the bottom of the hole and raise the outer pipe to some extent. To explain this process in a little more detail, after the stirring shaft (outer pipe) reaches the bottom of the hole, pouring of the stabilizer is started, and almost simultaneously the rise of the outer pipe starts. At this time, the inner pipe still remains at the bottom of the hole, but when the height difference between the outer pipe and the inner pipe becomes B, the drainage pump built into the inner pipe starts to operate and the stabilizing agent is injected. By this, excess water filling the ground around the agitation shaft is discharged through, for example, a screen. After the outer pipe further rises to a position where it is higher by a certain height H than the inner pipe, the inner pipe keeps the height difference H from the outer pipe, Will follow and rise. The values of H and B can be determined in advance depending on the condition of the ground and other factors.

Next, in detail, a screen with an appropriate porosity is installed around the pump, and in the case of sandy ground, as a protective facility to prevent the inflow of sand particles as needed. It may be covered with a net. By doing so, it becomes possible to more reliably exclude only excess water generated in the ground improvement section. At this time, there is a problem that water may absorb the particles of the hardening agent such as the cement-based solidifying material added and injected as the stabilizing agent all at once. In this regard, the grain system of cement particles, which is the main constituent molecule of many hardeners, ranges from 0.075 to 0.005 mm, with an average of about 0.020 mm. Since the size is equivalent to the particle size of, it is not discharged through the eyes of the screen. Rather, in the case of a viscous ground bed, the water in the improved construction site where the tissue was mechanically destroyed by the rotation of the stirring blades and the excess water injected by the addition of the slurry type stabilizer are drained, It is impossible to dehydrate the water in the surrounding cohesive soil.

When the stabilizing agent is added to the soft soil of the ground as in the conventional construction method and the mixture is treated by mixing and stirring, for example, when discharging 1.0 m ³ , the weight of the discharging soil is 2. It is 7 to 2.9 tons, and the treatment of the remaining soil is also difficult. However, when the same volume is used by the device of the present invention, 1.0 m ³ of water is about 1.0 t and is much smaller in weight when treated by drainage. Moreover, wastewater treatment is much easier than residual soil treatment. Further, in the construction method of the present invention, since the water in the soil of the ground improvement section is discharged, the water content ratio in the soil of the improvement section decreases, and the strength of the improvement pillar (body) increases accordingly. This is also one of the operational effects of the construction method using the device of the present invention.

The above operation will be described in more detail below. Generally, on soft ground, both sandy soil and cohesive soil contain a relatively large amount of water, but the existence of the water is significantly different between sandy soil and cohesive soil. In the case of sandy soil, the size of individual particles is relatively large (between 0.074 mm and 2.00 mm in particle size), and each particle exists individually, and as shown in FIG. One particle is present as a group. Such a structure is called a single grain structure. Therefore, in a sandy soil mass, the gap between particles is relatively large, and water molecules can flow through the gap relatively easily. Therefore, water permeability is good in sandy soil. On the other hand, soil called cohesive soil has small particle size (particle size is 0.074 mm to 0.005 mm for silt and 0.005 mm or less for clay), and therefore the gap between particles is smaller than sandy soil. In addition to being extremely small, unlike sandy soil, individual particles do not exist alone, but have a honeycomb structure as shown in Fig. 5b or a fluff structure shown in Fig. 5c. This is because the particles of cohesive soil are so small that the specific surface area is large, which causes an interfacial phenomenon.

Therefore, most of the water contained in the cohesive soil is chemically bonded to the cohesive soil particles forming such a chain structure by an ionic bond or a molecular bond, or a fine cohesive soil. It is physically attracted to the interstices of the particles as capillary water and has less free-moving water molecules than sandy soil. Moreover, in cohesive soil, the gaps between soil particles are much smaller than in sandy soil, so in fact the flow of water molecules is extremely small in cohesive soil, which is the reason why the permeability of cohesive soil is reduced. . In this way, it is very difficult to drain water from the cohesive land by the ordinary method.For example, even in the deep well method and the well point method, which are often used as drainage works, the amount of drainage from the cohesive land is extremely small. It is said that it is practically ineffective.

However, in the mixing stirrer in which the present invention is involved, the excavation bit (excavation blade) installed at the lower part of the stirring shaft and the structure of cohesive soil which is a structure of cohesive soil due to the rotation of the stirring blade It mechanically destroys and shreds water molecules that are chemically and physically bound to the tissue, freeing them to move freely. Therefore, it is possible to mix and stir by adding and injecting the stabilizing agent. This means that the construction method of the present invention enables drainage by a pump or the like regardless of the soil quality.

In this way, not only sandy soil but also clay soil can be drained by a pump, so that the increase in soil volume due to the addition of the stabilizing agent can be removed by drainage. It is possible to balance and eliminate the influence on the surroundings such as lateral flow and displacement. In addition, comparing the treatment with drainage and the case with soil removal, the latter requires laborious work such as peeling off the soil adhering to the screw, and treating the removed soil as residual soil. When treating with wastewater, it is possible to easily grasp the amount of wastewater with a flowmeter, so it is possible to perform drainage that almost exactly corresponds to the increase in soil volume, and there are no problems such as residual soil. There is an advantage that it does not occur.

[0020]

【Example】

 Next, the device of the present invention will be described with reference to the drawings. 1 is a front view of a main part of an embodiment of the device of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, FIG. 3 is a sectional view taken along line III-III of FIG. 1, and FIG. It is a schematic process drawing which shows one Example of the ground improvement method using the apparatus. First, an embodiment of the device of the present invention will be described with reference to FIGS. Reference numeral 1 in FIG. 1 denotes an outer tube, and as shown in FIG. 2, the inner tube 2 is housed inside the outer tube 1. The inner pipe 2 is supported so as to be movable up and down with respect to the outer pipe 1, and the lower end portion of the inner pipe 2 is capable of projecting and retracting downward from a hole 1a at the bottom of the outer pipe 1. The outer tube 1 is provided with a stirring blade 3 on the outer circumference thereof, like the conventional stirring shaft. Although the number and arrangement of the stirring blades 3 are not particularly limited, for example, as shown in FIG. 3, two blades are arranged so that they are opposed to each other at one location, and three stages are vertically arranged, and the angles about the axes are mutually. It should be installed in a shifted state. As shown in FIG. 1 and FIG. 2, a pair of two discharge holes 4 communicating the inside and outside of the outer tube 1 are provided at the same height as the agitating blades in three stages vertically.

A pump 5 is housed at the lower end inside the inner tube 2. As the pump 5, a known vertical submersible pump or the like can be used. For example, as shown in FIG. 3, openings 5b are radially formed in the portion of the pump 5 facing the water intake port, and the openings 5b do not allow dirt or cement particles to pass through, but a screen or a filter through which only water can pass. Luther 6 is attached. The drain port of the pump 5 is provided at the upper end, and the pumping pipe 7 is attached to the drain port. The pumping pipe 7 may be a tube or a hose other than a pipe. All of them are drainage passages. Reference numeral 8 in FIGS. 2 and 3 is a cabtire cord for power supply and control of the pump 5. Further, reference numeral 9 is an excavation bit (excavation blade), and a hole 9a is provided in the center of the excavation bit to allow the inner pipe 2 to be projected and retracted.

Next, with reference to FIG. 4, a procedure for carrying out the method of the present invention using the apparatus configured as described above will be described. Step I shown at the left end of FIG. 4 is a construction machine installation / preparation step in which the mixing and stirring apparatus A is installed on the ground J to be constructed. Stand vertically upright. Then, in step II, with the inner pipe 2 stored in the outer pipe 1, the excavation bit (excavation blade) 9 is rotated to dig the ground J, and the stirring shaft (outer pipe) is lowered. . At that time, since the stirring blade 3 is also rotated at the same time, the texture of the underlying soil in the cylindrical region K having the diameters at both ends of the stirring blade 3 is cut and broken into the misaligned water, and the water confined in the texture is broken. Most are released and are free to move. In this process, the stabilizing material is not yet discharged and the pump 5 is not operated.

Then, when the excavation is completed to a predetermined depth and the stirring shaft is attached to the hole bottom J1, the stabilizing treatment material is supplied through the supply passage 10 between the outer pipe 1 and the inner pipe 2, and is stabilized from the discharge hole 4. Mixing and stirring are started while injecting the treatment material (step III). The stabilizing material may be in the form of slurry or powder. Then, while continuing the mixing and stirring, only the outer tube 1 is lifted up to a certain height H while leaving the inner tube 2. The pump 5 built in the inner pipe has started to operate when the height difference between the inner pipe and the outer pipe becomes B (B <H), and therefore when the height difference becomes H, it is already normal. It is in a drainage state (process IV). Then, after the height difference becomes H, the inner pipe keeps maintaining the height difference H with the outer pipe, rises following the outer pipe, and continues the drainage work during that time. (Process V).

Although not shown, a flow meter for detecting the flow rate of the discharged water is provided in the upper end of the inner pipe or in the hose or pipe connected to the upper end of the inner pipe, and between the outer pipe 1 and the inner pipe 2. A flow meter for measuring the flow rate of the stabilizing material supplied to the supply passage 10 is provided in the upper portion of the outer pipe 1 or in the pipe connected thereto. Then, for example, the discharge flow rate of the pump 5 is controlled so that the inflow amount of the stabilizing material and the outflow amount of the discharged water are balanced. These controls are usually performed by automatic control. The inflow amount of the stabilizing material depends on the geology (cohesive soil, sandy soil, silt layer or clay layer of cohesive soil), density, amount of ground water, etc. It can be set based on the detected data. Also, the amount of discharged water with respect to the amount of stabilizing material to be supplied may be determined based on the data measured in advance as well, but as described in detail below, it hardly needs to be changed depending on the soil quality. This is also an advantage of the present invention.

Next, how the volume of the improved soil increases or changes when the cement-based solidifying material is added to the soft sandy soil and the soft cohesive soil as the hardening material in the stabilizing material In addition, when the ground improvement method with drainage treatment of the present invention is implemented, how the volume increase of the improved soil is balanced and its adverse effect can be eliminated will be explained. Two kinds of soft sandy soil and two soft clay soil samples are selected and classified as S-I, S-II and C-I, C-II respectively. The values of soil constants (water content w, void ratio e, saturation S r, unit volume weight γ, adhesive force c, internal friction angle φ) of these four types of soil samples are determined as shown in Table 1. In addition, cement-based solidifying materials are usually used as stabilizers to be added to these soils. There are two methods of addition, one is to use it in the form of powder and the other is to add it in the form of a slurry that is well mixed with water. Here, the case of adding it in the form of a slurry will be explained. The mixing ratio (weight ratio) of cementitious solidifying material and water is 1: 1. Many types of cement-based solidifying materials are sold by various manufacturers, but their functions are almost the same. The unit volume weight of the cement-based solidifying material is 3.15.

[0026]

[Table 1] [Case of sandy soil S-I] First, the case of soft sandy soil S-I will be described. As shown in Table 1, the soil particles have a specific gravity Gs of 2.67 kgf / cm ³ , a water content w of 66%, a void ratio e of 1.76, and a saturation Sr of 100%. Therefore, the composition of the initial volume Vo = 1.0 m ³ is as shown in Table 2 below.

[0027]

[Table 2]

Further, the composition of the slurry-like stabilizing treatment material obtained by mixing the cement-based solidifying material and water at a mixing ratio of 1: 1 is as shown in Table 3 below per 100 kg of the cement-based solidifying material, and the volume thereof is v _s becomes 0.132 m ³ .

[0029]

[Table 3] [Example 1] Now, when a cement-based solidifying material was added to a slurry-like stabilizing agent at 150 kg / m ^{3 in} a volume V _o = 1.00 m ^{3 of} sandy soil S-I, the stability of the stabilizing agent was improved. The volume v _s was v _s = 1.5 × 0.132 = 0.198 m ³ , and the total volume of soil immediately after addition was V ^′ = V _O + v _s = 1.00 + 0.198 = 1.198 m ^3, which was about 20. You will see a volume increase of close to%.

However, the added cementitious solidifying material immediately begins to react with the excess water in the ground to form a hydration product, and the reaction progresses at room temperature and atmospheric pressure after the hydration reaction starts. It will be about 20% of the total in one day and about 55-60% after 7 days. In the ground below the ground surface, conditions such as pressure and temperature differ depending on the depth and soil quality, but it cannot be said that it is true that the hydration reaction will proceed faster than at room temperature and atmospheric pressure. To be Therefore, the state where the hydration reaction is completed is as follows.

150 kg of the cementitious solidifying material in the stabilizing material v _s = 0.198 m ³ is about 37. It reacts with 5 kg of water (H ₂ O) to produce a hydrated product of w _s ^' = 150 + 37.5 = 187.5 kg = 0.1875 t, but the unit volume weight of the hydrated product is approximately 3.00 tf. / M ³ . Therefore, the total volume of the hydrated product is v _s ^' is v _s ^' = 0.1875 / 3.0≈0.063m ³

On the other hand, the total amount of water in V ^′ = 1.198 m ³ is 0.638 m ³ (638 kg) in v _o and 0.150 m ³ (150 kg) in v _s , of which 37.5 k The amount of g disappears due to the hydration reaction. Therefore, the residual content is as follows. Weight ^{_{w w '= 638 + 150-37.5 =}} 750.5kg volume ^{_{v w' = 0.638 + 0.150-0.0375 =}} 0.7505m 3

As a result, the composition of the improved soil at the end of the hydration reaction is as shown in Table 4 below.

[Table 4] That is, the slurry-state stabilizing material was added to V _o = 1.00 m ³ of S-I soil with v _s = 0. When only 198 m ³ (150 kg of cementitious solidifying material) was added, the volume of soil immediately after the addition increased to V ^′ = 1.198 m ³ , but it decreased slightly at the end of the hydration reaction, and V ^“ = 1.176 m ³ After that, there is no further change, so the final volume increase is 0.176 m ³ .

[Examples 2 to 4] Similarly, in V _o = 1.00 m ³ of the soft sandy soil S-I, the amount of the cementitious solidifying material was 200 kg / m ³ , 250 kg / m ³ and 300 kg / The case where a slurry-like stabilizing material is added as m ³ will be described. First, the case of adding the cement solidifying material 200 kg / m ^3, the volume of slurry stabilization process material v _s is _{v s = 2.0 × 0.132 = 0.264m} 3 , and the immediately after adding the soil of all volume will be ^{_{V '= V o + v s}} = 1.00 + 0.264 = 1.264m 3 and about 26 per cent of the volume increase. Next, looking at the state after completion of the hydration reaction, 200 kg of the cement-based solidifying material in the stabilized material reacts with about 50 kg of water (H ₂ O) (weight) w _s ^' = 200 + 50 = 250 kg = 0 make .250t ^{_{(volume) v s' = 0.25 / 3.0}} = 0.083m 3 of hydration products. As a result, the amount of water remaining in the soil is as follows. (Weight) w _w ^' = 638 + 200-50 = 788 kg (Volume) v _w ^' = 0.638 + 0.200-0.050 = 0.788 m ³

As a result, the composition of the improved soil at the end of the hydration reaction is as shown in Table 5 below.

[Table 5]

That is, the volume of soil at the end of the hydration reaction is V ^" = 1.233 m ³ , which is slightly smaller than 1.264 m ³ immediately after the addition of the stabilizing treatment material. Cement-based solidifying material 250 kg / m ³ And, when the stabilizer is added at 300 and 300 kg / m ³ , the results are as follows: In the case of the cement-based solidifying agent of 250 kg / m ³ , the volume immediately after adding the stabilizer is V ^′. = V _O + v _s ^′ = 1.00 + 2.5 × 0.132 = 1.330m ³ The volume of soil at the end of the hydration reaction is V ^″ = 0.362 + 0.104 + 0.826 = 1.292m ³ . When the cement-based solidifying material is 300 kg / m ³ , the volume of soil immediately after the addition of the stabilizing material is V ^′ = 1.00 + 3.0 × 0.132 = 1.396m ³ At the end of hydration reaction a is ^{V "= 0.362 + 0.125 + 0.863} = 1.350m 3.

[Case of Sandy Soil S-II] Next, the case of soft sandy soil S-II will be described. The initial composition of this sample 1.0 m ³ is shown in Table 6 below.

[Table 6]

[Example 5] If a slurry-like stabilizing material containing 150 kg of a cement-based solidifying material was added to 1.0 m ^{3 of} this soil, the total volume of the soil immediately after the addition was V ^" = V _o + v _s = 1. a ^{.00 + 1.5 × 0.132 = 1.198m 3} . then, after the completion of the hydration reaction, each amount of water (H ₂ O) remaining in hydration products and soil as follows Hydration product (weight) w _s ^' = 150 + 37.5 = 187.5 kg = 0.1875 t (volume) v _s ^' = 0.0875 / 3.0 = 0.063 m ³ Water (weight) w _w ' = 604 + 150-37.5 = 716.5 kg (volume) v _w '= 0.604 + 0.150-0.0375 = 0.7165 m ³ Therefore, the volume of soil is as follows: V ^" = 0.396 + 0.063 + 0 0.7165≈1.176 m ³ [Example 6] Thus, when the amount of cement-based solidifying material added is 200 kg / m ³ , the total volume of soil immediately after the addition of the stabilizing material is V ^' = 1.00 + 2.0 × 0.132 = 1.264m ^{When the} hydration reaction is completed, V ^" = 0.396 + 0.083 + 0.754 = 1.233m ^3. [Example 7] When the amount of the cement-based solidifying material is 250 kg / m ³ , the addition is made immediately after the addition. And the total volume of soil at the end of the hydration reaction is as follows: Immediately after addition V ^' = 1.00 + 2.5 × 0.132 = 1.330 m ³ At the end of the hydration reaction V ^" = 0.396 + 0 .104 + 0.792 = 1.292 m ³ [Example 8] When the amount of the cement-based solidifying material was 300 kg / m ³ , the total weight of soil immediately after addition and at the end of the hydration reaction was V ^'= 1.00 + 3.0 × .132 = 1.396m ³ hydration reaction at the end of ^{V "= 0.396 + 0.125 + 0.829} = a 1.350m ^3.

[Consideration on Sandy Soils S-I and S-II] As described above, the stabilizing agent was added to each of the two types of samples of the soft sandy soils S-I and S-II at four different addition amounts. However, we have seen changes in the volume of soil when mixed and agitated. The results are shown in Table 7 below.

[Table 7]

That is, as is known from Table 7, even if the soil properties of the initial sample soil differ in the water content ratio, the void ratio, etc., the volume change of the soil occurs when the same amount of stabilizing material is added. It turns out that the proportions of are equal. However, if the initial sample soil is unsaturated soil, the change in volume will be smaller. Next, let us consider this with respect to the sample ground of soft cohesive soil.

[Case of Cohesive Soil CI] First, the case of soft cohesive soil C-I will be described. The composition of 1.0 m ³ of this sample is shown in Table 8 below.

[Table 8]

[Example 9] When the slurry type stabilizing material was added to this soil with the amount of the cement-based solidifying material being 150 kg / m ³ , the volume of the soil immediately after the addition was V '= 1.00 + 1.5 ×. 0.132 = 1.198m ^3, and the further hydration reaction proceeds after addition, this is the volume of each substance improvements soil in the state ended is as follows. Soil 0.264m ³ Hydration product 1 / 3.0 × (150 + 37.5) = 0.0625m ³ ≒ 0.063m ³ Water 0.736 ＋ 0.150-0.0375 = 0.8485 ≒ 0.849m ³ Therefore the total volume is V ^"= 0.264 + 0.063 + 0.849 = 1.176m ³ become. [examples 10-12] Similarly 200 kg / m ³ the amount of cement solidifying material, the case of the 250 kg / m ³ and 300 kg / m ³ respectively as follows.

When the amount of the cement-solidifying material is 200 kg / m ³ , the volume V ^′ of the soil immediately after the addition is V ^′ = 1.00 + 2.0 × 0.132 = 1.264m ³ The volume V of the soil at the end of the hydration reaction ^{"the V"} a = 0.264 + 0.083 + 0.886 = 1.233m 3.

Next, when the amount of the cement-based solidifying material is set to 250 kg / m ³ , the soil volume V ^′ immediately after addition and the soil volume V ^“ at the end of the hydration reaction are as follows. V ^' = 1.00 + 2.5 × 0.132 = 1.330m ³ V ^" = 0.264 + 0.104 + 0.924 = 1.292m ^{3 When} the amount of cementitious solidifying material is 300kg / m ³ , the volume of soil V immediately after addition is V ^'And the volume of soil at the end of the hydration reaction V ^" is as follows: V ^' = 1.00 + 3.0 × 0.132 = 1.396m ³ V" = 0.264 + 0.125 + 0.961 = 1.350m ³

[Case of Cohesive Soil C-II] Next, regarding the soft cohesive soil C-II, the composition of 1.0 m ³ of this sample is as shown in Table 9 below.

[Table 9]

[0046] [Examples 13 to 16] As the amount of cement solidifying material in the soil is ^{150kg / m 3, 200kg / m} 3, 2 50kg / m 3 and 300 kg / m ³ added Stabilized material treated if each value of the volume V ^'and soil volume at the end hydration V ^"soil immediately after adding as follows. If the amount of cement solidifying material is 150 kg / m ^3. V ^' = 1.00 + 1.5 × 0.132 = 1.198m ³ V ^" = 0.320 + 0.063 + 0.793 = 1.176m ^{3 When} the amount of cementitious solidifying material is 200kg / m ³ . V ^' = 1.00 + 2.0 × 0.132 = 1.264m ³ V ^" = 0.320 + 0.083 + 0.830 = 1.233m ^{3 When} the amount of cementitious solidifying material is 250kg / m ^3. V ^' = 1.00 + 2.5 × 0.132 = 1.330m ³ V ^" = 0.320 + 0.104 + 0.868 = 1.292m ^{3 When} the amount of cementitious solidifying material is 300kg / m ³ . V ^' = 1.00 + 3.0 × 0.132 = 1.396m ³ V ^" = 0.320 + 0.125 + 0.905 = 1.350m ³

[Study on Cohesive Soil] Similar to the trials on the soft sandy soils S-I and S-II, the amount of the cementitious solidifying material in the two types of the soft cohesive soils C-I and C-II was examined. The state of the volume change when the slurry-like stabilizing treatment material was added was changed, and the results are summarized in the table shown in Table 10 below.

[Table 10]

That is, also here, as in the case of soft sandy soil, it can be seen that even if the sample soil is different, the rate of change in volume is irrelevant and changes only depending on the amount of stabilizer added. . At the same time, the rate of change in volume is exactly the same in sandy soil and cohesive soil, and this is unavoidable, and even in soft soil where sandy soil and cohesive soil are mixed, similar volume changes are observed. Indicates that Therefore, if the ground is a saturated ground, regardless of the type of ground and physical properties (viscosity, water content ratio, void ratio, unit volume weight, etc.), the amount of slurry stabilizer added will be determined. Therefore, it is possible to estimate how much the volume will change (increase), and it will be possible to easily determine the required amount of wastewater that corresponds to this.

That is, a slurry of W: C = 1: 1 is added to 1.0 m ³ of a certain saturated soil (saturation 100%) so that the amount of the cementitious solidifying agent added becomes 200 kg / m ^3. A case where a stirrer-like stabilizing material is discharged and added and mixing and stirring is performed will be described. Assuming that the diameter of the improved column is 1.000 mm and the pulling speed of the stirring shaft is 1.0 m / min, the volume of soil per depth of 1.0 m of the improved part is V = (π / 4) × 1 Since 0.0 ² ≈0.785 m ³ , the volume of soil immediately after addition increases to V ^′ = 1.264 × 0.785 = 0.992 m ³ . But as the progress of the hydration reaction and the volume decreases gradually, and finally it is not a ^{V "= 1.233 × 0.785 = 0.968m} 3. Therefore Compared with the previous volume added, only per depth ^{1.0m ΔV = V "-V = 0.968-0.785} = 0.183m 3 so that the volume is increased.

If the drainage is treated only for the increased volume, the required water distribution is 183 liters per 1.0 m in depth, and the pump lift follows the outer tube of the stirring shaft. , 1.0 m / min. Therefore, the required drainage q of the pump is also q = 183 liter / min = 0.183 m ³ / min. It is easy to control the displacement of the pump by installing a flow meter, which allows the volume increase of the improved section ground in the mixing and agitation process to be controlled with extremely high accuracy.

The above is the main effect of the device of the present invention, which is the drainage work for suppressing the lateral flow and displacement by suppressing the increase of the soil volume in the improved part in the mixing and agitating work and eliminating the influence on the surroundings. The mechanism, action, and effect of the device have been explained, but the present invention has another great effect. It is an effect that the removal of excess water from the soil in the improved part by the device of the present invention lowers the water content of the soil in the improved part, and the strength of the completed improved column becomes large.

Generally, in the mixing and stirring work, when the same amount of hardener is added to the same amount of soil, the soil having a smaller water content shows a higher strength, but the soft sand mentioned above as an example. Slurry stabilizer (W: C = 1: 1) was added to two samples of each of soil and cohesive soil by various amounts of hardened cement-based solidifying agent, and mixed and stirred. Table 11 shows the comparison of the water content ratio w (%) between the case of leaving it as it is and the case of removing the excess water filling the improved soil with the device of the present invention. become.

[Table 11]

As shown in Table 11, when the drainage work is performed by the device of the present invention, the water content of the improved soil can inevitably be greatly reduced. Therefore, the strength of the improved portion (pillar) is increased and the improvement is improved. As a result, the effect is increased.

The mechanism of drainage of excess water in the improved soil and its function and effect by the device of the present invention have been described with respect to the case of using the slurry-like stabilizing treatment material, but it is added in the form of powder. In this case, since the volume of soil increases as the stabilizer or hardening material is added to the ground, the volume corresponding to the soil volume must be reduced. It has the same effect. Therefore, the stabilizer or the hardening agent to be added is applied in the same manner whether it is in the form of slurry or powder.

[0055]

[Effect of device]

 The effects of using the device of the present invention are as follows. (1) In the mixing and agitation method, the volume of the improved soil increases when the stabilizing material or hardening material is added to the ground to form a slurry or powder. By eliminating only the amount commensurate with the increase in the flow rate, it is possible to suppress the increase in volume, prevent lateral flow and displacement, and eliminate the influence of the surroundings. (2) It is also effective in the case of adding the stabilizing material or the hardening material to the ground in the form of slurry or the powder in the mixing and stirring method. (3) Since the increased volume of soil is treated in the form of drainage instead of discharge, the work is easy and there is no need for residual soil treatment. (4) Since the increase in the volume of soil is treated in the form of drainage, it is possible to easily determine with a flowmeter whether or not an appropriate amount of drainage has been performed, and drainage control is easy. (5) The hardened material added as a stabilizing material is not discharged to the soil unlike the case of soil removal. (6) Since the water content of the soil in the improved section is lowered by the drainage in the soil in the improved section, the strength of the resulting improved body is increased.

[Brief description of drawings]

FIG. 1 is a front view of an essential part showing an embodiment of the device of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a schematic process drawing showing an embodiment of a construction method using the device of the present invention.

5a, 5b and 5c are enlarged views showing the texture structure of the ground targeted by the method of using the mixing and stirring apparatus of the present invention, and FIG. 5a shows the structure of sand and FIG. FIG. 5c shows the structure of cohesive soil.

[Explanation of symbols]

 1 Outer pipe 2 Inner pipe 3 Stirring blade 4 Discharge port 5 Pump 6 Screen 7 Pumping pipe (drain pipe) 8 Cabtyre cord 9 Excavation bit (excavation blade)

Claims (6)

[Scope of utility model registration request] 1. A pipe-shaped stirring shaft having a drilling bit and a stirring blade near the lower end, a stabilizing treatment material supply passage and a drainage passage respectively provided inside the stirring shaft, and from the lower end through the drainage passage. A mixing and stirring device consisting of a pump for sucking water and discharging it from the upper end. 2. A stirrer shaft is a double pipe consisting of an inner pipe and an outer pipe, a stabilizing treatment material supply passage is provided between the inner pipe and the outer pipe, and a drainage passage is provided inside the inner pipe. The apparatus according to item 1. 3. The device according to claim 1, wherein the drainage pump is provided near the lower end of the drainage passage. 4. The apparatus according to claim 2, wherein the drainage pump is housed near the lower end of the inner pipe. 5. The apparatus according to claim 2, wherein the inner tube is provided so as to be vertically movable with respect to the outer tube so that the lower end of the inner tube can project from the lower end of the stirring shaft. 6. The apparatus according to claim 1, wherein a screen or a filter that allows water to pass through soil particles and cement fine particles is provided below the drainage passage.