JPH0726553A - Cement mixing construction method for treating deep layer - Google Patents

Abstract

PURPOSE:To increase the tensile strength of improved subsoil and prevent the occurrence of a crack and a break due to a vibration including an earthquake by filling weak subsoil with a hydraulic material for the solidification thereof. CONSTITUTION:A treatment device 1 is constituted of an auger 2 having an agitation blade 3 and an intrusion mechanism 4 for pushing the auger 2 into subsoil T. The mechanism 4 is fitted with a polyvinyl alcohol solution introduction tube and connected to the discharge outlet 5 and the nozzle 6 of the blade 3. Then, after the mechanism 4 is made to intrude into the subsoil T up to T1 depth, cement or the like is supplied, and the earth, the cement and polyvinyl alcohol are agitated and mixed with the blade 3. As a result, the mixture quickly coagulates due to alkali and turns into a fibrous linear solid. Subsequently, the blade 3 is pulled out, and weak subsoil over the range of a deep layer to an upper layer is improved for stabilization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called deep-mixing processing method in which a hydraulic material such as cement is poured into a soft ground and stirred to solidify the ground. The present invention relates to a cement mixing deep treatment method for further improving the solidified foundation ground by further uniformly and randomly blending a fibrous or fibrillar filamentous substance made of polyvinyl alcohol in a mixture with a substance.

[0002]

2. Description of the Related Art Conventionally, for the purpose of improving soft ground due to coasts, swamps, landfills, etc., it has been hardened and solidified by a hydration reaction between hydraulic substances such as lime and cement and pore water in the soil. There is known a cement mixing deep treatment method in which the ground is improved into a pile shape or a board shape, and this is used as a foundation ground. This method is not only for general ground improvement, but also as a method for solidifying quay foundations and protection wall foundations, as a method for solidifying the foundations of roads and tanks, as a method for restraining the sides of piles, and also for simple earth retaining walls and earth structures It is also used as a construction method for building things. Especially in soil improvement, it has been adopted on a large scale compared to conventional chemical soil improvement methods such as consolidation and chemical injection, and the effect is improved by performing it together with conventional soil improvement methods. It is also used if you do.

[0003]

However, the conventional cement mixing deep layer treatment method has the following problems. That is, although the mixture produced by the conventional cement mixing deep treatment method can increase the compressive strength,
Low tensile strength and low strain at compression failure. For this reason, it is feared that the improved ground formed by this cement mixing deep treatment method may easily crack when subjected to a large force such as an earthquake, or may break at a low strain level. There was a problem. Therefore, as an improved method for overcoming these problems, a method of mixing synthetic fibers in cement slurry (milk), introducing this into the ground and stirring and mixing with soil, or using geotextile as a reinforcing material, A method of introducing the soil into the ground has been proposed. However, in the former method of mixing fibers, it is difficult to mix the soil and the fibers uniformly because the fibers are entangled at the time of stirring and mixing in the ground, and moreover, the cement containing such fibers is mixed. Since the diameter of the introduction pipe is small when the slurry is introduced into the ground through the introduction pipe of about 2 inches, the problem that the introduction pipe is clogged cannot be solved and cannot be practically used. Also,
In the latter geotextile construction method, it is also difficult to insert a fabric body formed of fibers into the ground, and none of these methods has been a fundamental solution to the above problem.

The present invention has been made in view of the above problems, and enhances the tensile strength of the improved ground formed by the cement-mixing deep treatment method in which a hydraulic substance is injected into the ground to solidify the ground. The purpose of the present invention is to provide a cement mixing deep treatment method capable of increasing the strain at the time of compressive fracture and preventing the occurrence of cracks at the time of an earthquake and the fracture at a low strain level.

[0005]

[Means for Solving the Problems] That is, in the cement mixing deep treatment method of the present invention, a hydraulic material such as cement is injected after the stirring blade is penetrated to a predetermined depth position in the ground, and the soil and the water are mixed with the stirring blade. It is a deep-layer mixing treatment method in which the stirring blade is pulled out while stirring and mixing with a hard substance to solidify the ground, and a nozzle for discharging or ejecting a solution is provided at the stirring position of the stirring blade, and the stirring blade is stirred. In the mixture of the soil and the hydraulic substance being developed, from the nozzle, the polyvinyl alcohol aqueous solution added with a substance that solidifies or solidifies polyvinyl alcohol in an alkaline environment is discharged or jetted, and the soil and the hydraulic substance. To form a solidified or solidified fibrous or fibrillar filamentous substance composed of polyvinyl alcohol in a mixture of It was the solution. By adopting this construction method, the solidified or solidified fibrous or fibrillar filaments made of polyvinyl alcohol can be mixed uniformly in the mixture of soil and cement, and as a result, the above-mentioned conventional It is possible to remarkably improve the difficulty of the technique and reduce the crack generation and the breakage at a low strain level of the improved ground at the time of an earthquake.

[0006]

According to the cement mixing deep treatment method of the present invention,
While the soil and cement are being stirred by operating the stirring blade, a polyvinyl alcohol aqueous solution containing a substance that solidifies or solidifies polyvinyl alcohol is discharged or jetted from the nozzle. When the polyvinyl alcohol aqueous solution is discharged from the nozzle and comes into contact with the mixture of soil and cement, the alkali rapidly solidifies to form fibrous or fibrillar filaments. Since this linear material is mixed into the stirred mixture of soil and cement according to the pulling out of the stirring blade, it is possible to uniformly disperse and mix the linear objects of polyvinyl alcohol in the stirred mixture of soil and cement. It can be done.

The core point of the present invention in the above-mentioned construction method is that fibrous or fibrillar filaments are consequently present in a state of being uniformly dispersed in a mixture of soil and a hydraulic substance such as cement. To do so, do not use fibrous or fibril-like filaments from the beginning, but use a polymeric substance that can be made into fibrous or fibril-like later, and stir the solution-like substance with a stirring blade. From the position, it is directly mixed into the mixture of soil and cement that is being stirred and mixed by the stirring blade, and the fibrous or fibril-like filaments are rapidly mixed in the alkaline environment consisting of the mixture of soil and cement after mixing. This is the point of solidifying or solidifying an object. More specifically, as a polymer substance that can be mixed into a mixture of soil and a hydraulic substance such as cement to form fibrous or fibrillar filaments, the alkalinity of the mixture of soil and cement is used to The point is to utilize that the alcohol solidifies or solidifies in the alkaline environment when boric acid, sodium alginate or the like is present therein. That is, the "substance that coagulates polyvinyl alcohol" is boric acid, sodium alginate, or the like.

Further, as described above, it is practically difficult to feed the fibers into the soil, especially deep soil, and to disperse the fibers uniformly in the soil without being entangled. INDUSTRIAL APPLICABILITY The present invention does not send a filamentous product into the soil from the beginning, but sends in a polymer substance that can be made into a filamentous product later, and rapidly forms a filamentous product by contact with soil. . That is, not only the solidification by cement of the soft ground to be treated, in order to improve the small point of the tensile strength which is not improved even in that case, the small point of the strain at the time of compressive fracture, in the soft ground to be treated, As a result, it was discovered based on the view that the filamentous material should be uniformly dispersed and present. Surprisingly, even with filamentous filaments solidified or solidified in soil, the above improvement results are large. Of.

However, the polymeric substance that can be practically adopted with such an idea is a substance capable of retaining the strength in an alkaline environment, and in actual construction, for example,
Adding a special melt heating introducing means for maintaining the introduction route until introducing the substance into the soil at a high temperature is not immediately applicable, and it is not possible to use a special method for such an apparatus. It is required that it can be used at room temperature without using improving means. From these points, the present invention uses polyvinyl alcohol as a polymer substance, and achieves the purpose by using it well.

The polyvinyl alcohol used must be a saponified product having a degree of polymerization of 500 or more. If the degree of polymerization is lower than this, even if it can be made into a linear object, its mechanical strength is insufficient and the purpose cannot be achieved. At present, when the degree of polymerization is high, it is necessary to make the concentration low in order to obtain fluidity at room temperature, but in that case, it tends to be difficult to coagulate and solidify. Therefore, the upper limit of the degree of polymerization is 20,000,
The saponification degree of polyvinyl alcohol is preferably as high as possible, and is preferably 98% or more.

Such polyvinyl alcohol is dissolved in water so that its concentration becomes 3 to 15% to obtain an aqueous solution. If the concentration is too high, the viscosity of the aqueous solution will increase, and as a result, a heating device and a heat retaining means for heating the solution to reduce its viscosity will be required as described above. This is not preferable because it requires significant improvement of the device. Therefore, the concentration of the aqueous solution of polyvinyl alcohol is 15% so that it can be used at room temperature without making such a significant improvement.
It is preferably 10% or less. However, even if the concentration is too low, a good linear product cannot be produced and the strength also becomes low. Therefore, it is preferably 3% or more.

[0012] Polyvinyl alcohol of the polyvinyl alcohol aqueous solution as described above is added to a mixture of soil and cement,
That is, in order to promptly solidify or solidify in an alkaline environment, it is important to add a hardening aid such as boric acid or sodium alginate to the aqueous solution. Polyvinyl alcohol, even by itself, causes gelation and solidifies in an alkaline environment, but since the solidification rate is slow,
The curing aid is added to accelerate this.
The amount of addition is 0.4 to polyvinyl alcohol.
It may be about 5.0%, and if it is lower than that, the promoting effect is thin, and if it is too high, the solution becomes unstable. When boric acid is added, it is considered that gelation occurs due to crosslinking of the added boric acid and polyvinyl alcohol in an alkaline environment, and solidification of polyvinyl alcohol occurs. In the specification, it does not matter in what process polyvinyl alcohol becomes a filamentous product as a result, that is, whether it is solidification or solidification. Therefore, in the present specification, it is described as "solidification or solidification". . Many soils, including Japan, are acidic. Further, since the soil has a high neutralizing ability, the alkali of the cement slurry alone may not be enough to coagulate the polyvinyl alcohol depending on the type of the soil. In such a case, it is necessary to add alkali such as caustic soda to the cement slurry in advance to enhance the alkalinity.

The aqueous solution of polyvinyl alcohol has a pH
In order to keep 1 to 7 acidic or neutral, it is preferable to add an acid such as acetic acid or nitric acid to the aqueous solution. Furthermore, the preferable pH is 3 to 5 in view of the corrosiveness of the material and the stability of the polyvinyl alcohol solution.

The polyvinyl alcohol aqueous solution prepared as described above is, of course, also introduced from the ground so as not to cause solidification or solidification until it is discharged or jetted into the soil to be treated and added. It should not come into contact with the cement slurry and be fed via separate introduction paths to both feed points in the vicinity of the stirring blade.

An example of the present invention will be described in more detail below with reference to FIGS. 1 and 2. In the figure, reference numeral 1 is a cement mixing deep-layer treatment device. As shown in FIG. 1 and FIG. 2, the cement mixing deep-layer treatment apparatus 1 includes an auger 2 vertically pushed into a ground T to be treated, and a stirring blade attached to an upper portion of the auger 2 and protruding horizontally. 3 and an insertion mechanism 4 for pushing the auger 2 below the ground T from the ground. Inside the insertion mechanism 4, a cement slurry introduction pipe (not shown) from the ground,
An inlet pipe (not shown) for the polyvinyl alcohol aqueous solution is provided, and each of the plurality of discharge ports 5 provided in the stirring blade 3 is provided.
It is connected to the nozzle 6 (see FIG. 2).

As shown in FIG. 2, a discharge port 5 for discharging cement slurry and a nozzle 6 for discharging or spraying an aqueous polyvinyl alcohol solution are attached to the side surface of the central portion of each stirring blade 3. The discharge port 5 and the nozzle 6 are configured to discharge cement slurry and polyvinyl alcohol aqueous solution in a substantially horizontal direction, respectively. The discharge port 5 and the nozzle 6 are also attached to the upper end of the auger 2. Further, the insertion mechanism 4 has a built-in pressure feeding mechanism (not shown) that pressure feeds cement slurry and polyvinyl alcohol aqueous solution supplied from the ground to the respective discharge ports 5 and nozzles 6 with a predetermined pressure. The discharge port 5 is composed of an opening having a diameter of about several millimeters, and is formed so as to constantly and stably discharge the cement slurry pumped by the pumping mechanism by a predetermined amount. The nozzle 6 is composed of a large number of holes each having a hole diameter of several millimeters, and is also formed so as to always stably discharge a predetermined amount of polyvinyl alcohol.

With the above-mentioned structure, the cement mixing deep-layer treatment apparatus 1 is configured so that the cement slurry has an appropriate concentration within the above concentration range (3 to
The polyvinyl alcohol aqueous solution of 15%) is pressure-fed to each ejection port 5 and nozzle 6 by a pressure-feeding mechanism (not shown), and is ejected or ejected from these ejection port 5 and nozzle 6 in the horizontal direction. The discharge pressure of the nozzle 6 is maintained at 10 kg / cm ² or more in order to prevent the cement slurry from flowing back into the nozzle 6.

Using the cement-mixing deep layer treating apparatus 1 as described above, the main treating method for forming the improved ground T1 on the ground T is performed as follows. First, the cement mixing deep treatment apparatus 1 is inserted into the ground T by the insertion mechanism 4 with the tip of the auger 2 facing downward, and the ground T is excavated as in the normal deep mixing treatment. At the time of insertion, the auger 2 and the stirring blades 3 are operated so that the ground T is stirred and the insertion mechanism 4 is inserted.
Push it down with. When the insertion mechanism 4 reaches the desired depth of the ground T, the pumping mechanism (not shown) is operated while pulling up the cement mixing deep layer treatment device 1
The cement slurry and the polyvinyl alcohol aqueous solution supplied from the ground are pressure-fed to the ejection port 5 and the nozzle 6, and ejected or ejected from the ejection port 5 and the nozzle 6. There is also a method of mixing cement slurry when excavating and stirring the ground T downward with the insertion mechanism 4 and discharging polyvinyl alcohol when pulling up.

The discharged or jetted cement slurry and the polyvinyl alcohol aqueous solution are mixed with soil and cement by stirring, rapidly solidify or solidify due to the alkalinity of the cement, and the fibrous or fibril-like wire is arranged in the order of being discharged or jetted. Form a strip.

Therefore, in the cement mixing deep treatment method of the present invention, the cement slurry and the polyvinyl alcohol aqueous solution are discharged or jetted from the discharge port 5 and the nozzle 6 while stirring the ground T while the auger 2 and the stirring blade 3 are rotated. Therefore, the discharged or jetted cement slurry and the polyvinyl alcohol aqueous solution are solidified substantially in the order in which they are discharged or jetted, so that the auger 2 and the stirring blade 3 are mixed with the soil and the cement without being entangled with each other, and the fibrous or It is possible to construct a good improved ground T1 in which fibril-like filaments are formed, and the filaments are present in a state of being uniformly dispersed without uneven distribution of the polyvinyl alcohol filaments.

[0021]

EXAMPLES The construction method of the present invention will be described below with reference to specific model examples, but the present invention is not limited to these model examples. Example 1 As the cement, ordinary Portland cement was used, and W / C was set to 0.6. The nozzle for ejecting or ejecting the polyvinyl alcohol aqueous solution is 0.5 m.
The diameter was m. Polyvinyl alcohol was a completely saponified product having a degree of polymerization of 1700, and a 10% aqueous solution thereof was used. Further, as the curing aid to be added to this polyvinyl alcohol aqueous solution, 2.8% of boric acid to polyvinyl alcohol is used, and acetic acid of 0.35% is added as an acidity adjusting agent to add the pH of the aqueous solution. Was adjusted to 3. Cement slurry was ejected or jetted into the agitated soil at a rate of 170 liters / m ³ and the polyvinyl alcohol aqueous solution at a rate of 30 liters / m ³ to obtain a mixed soil.

As Comparative Example 1, an experiment was conducted in which the same conditions as in Example 1 above were adopted, but the only difference was that the cement slurry was not discharged and mixed.

Further, as Comparative Example 2, an experiment was conducted in which the same conditions as those in Example 1 were adopted, except that the polyvinyl alcohol aqueous solution was not added and mixed.

As a result, in Comparative Example 1, only the fibers were mixed, and the soil strength could not be increased. Comparative Example 2 is an example corresponding to the conventional method in which only cement slurry is mixed as described in the section of the prior art, but even in this example, it will be destroyed if a person rides on it. On the other hand, in Example 1, it is not broken even if a person rides on it, the compression strength is improved during the uniaxial compression test, and the horizontal protrusion (distortion at the time of compression failure) is large, and the energy absorption effect is large. is expected.

[0025]

According to the method of the present invention, the improved ground constructed by the so-called deep layer mixing treatment method in which a hydraulic substance is injected into the soft ground to solidify the ground further enhances the tensile strength, and at the time of compressive failure. It is possible to obtain a more stable and improved ground that can prevent cracks and damages due to vibrations such as earthquakes by increasing the strain on the ground, and can also be easily applied to the conventional technology of the past. In addition, it is possible to provide a practical method excellent in its improving effect and easiness of implementation.

[Brief description of drawings]

FIG. 1 is a front view showing a main part of an example of an apparatus for carrying out a construction method of the present invention.

FIG. 2 is an enlarged view of a lower portion of the device.

[Explanation of symbols]

 3 Stirring blade 5 Discharge port 6 Nozzle T Ground

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshio Watanabe 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Sumio Horiuchi 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Shoichi Nishiyama 130 Kamiwatsu Oto, Saijo City, Ehime Prefecture Tetsufu Dormitory (72) Inventor Masaki Okazaki 1-1239 Umeda, Kita-ku, Osaka City, Osaka Kuraray Co., Ltd. (72) Inventor Tsutomu Ebe 3-8-2 Nihonbashi, Chuo-ku, Tokyo Kuraray Co., Ltd. Tokyo office

Claims (1)

[Claims] 1. A ground material is obtained by injecting a hydraulic substance such as cement after penetrating the stirring blade to a predetermined depth position in the ground, and pulling out the stirring blade while stirring and mixing the soil and the hydraulic material with the stirring blade. Is a deep mixing treatment method for solidifying, a nozzle for discharging or ejecting a solution is provided at a stirring position of a stirring blade, and the nozzle is provided in a mixture of soil being stirred by the stirring blade and the hydraulic material. From the above, a polyvinyl alcohol aqueous solution added with a substance that solidifies or solidifies polyvinyl alcohol in an alkaline environment is discharged or jetted, and a solidified or solidified fibrous or fibril consisting of polyvinyl alcohol is added to the mixture of the soil and the hydraulic substance. Cement mixing deep layer treatment method characterized by forming a linear filamentous object.