JP2020193451A - Injection method - Google Patents

Abstract

To provide an injection method capable of penetrating cement-based injection liquid in suspension liquid into the ground without being filtered.SOLUTION: An injection method for improving the soft ground by injecting a cement-based injection material includes: selecting a cement-based injection material in which polycarboxylic acid-based dispersant (PC dispersant) is added as a cement-based injection material; and injecting PC dispersant solution into the ground at a step before injecting the cement-based injection material in which polycarboxylic acid-based dispersant is added. In the present invention, preferably, water is injected into the ground before injecting the cement-based injection material as well as after injecting the PC dispersant solution into the ground.SELECTED DRAWING: Figure 4

Description

The present invention relates to an injection method for improving by injecting a cement-based injection material into, for example, soft sandy ground.

In such an injection method, for example, a cement-based injection solution is used as the injection solution to be injected into soft sandy ground, and cement milk, which is a suspension in which cement particles are dispersed in water, is used.
Cement particles are used in ground improvement work where it is necessary to create a high-strength improved body and there is concern about the effects of injection near the structure, and in ground improvement work that requires a high-strength improved body in low-permeability ground. Cement-based solidifying material with a very small particle size (for example, cement-based solidifying material with a particle size of several μm to several tens of μm: For example, the trade name “Hyper NP1500” manufactured by Nippon Steel Cement Co., Ltd., or Nittetsu Cement. The product name "Nippon Steel Super Fine") manufactured by Nippon Steel Co., Ltd. may be used.
However, since the cement-based injection solution, which is such a suspension, is a suspension, the injection solution is affected by the adhesion of cement particles in the injection solution to the ground constituent particles and the accompanying clogging. There are cases where the permeability cannot be fully exerted by being filtered and blocking its own permeation pathway.

As another conventional technique, for example, there is a technique for easily and surely controlling the pulsating pressure when a pulsating component is added to the injection pressure and dynamically injected (see Patent Document 1). Further, there is a grout material dynamic injection device having a simple structure and low equipment cost (see Patent Document 2).
However, the prior art (Patent Document 1 and Patent Document 2) has a problem that a special machine is required for construction.

Japanese Unexamined Patent Publication No. 2004-197305 JP-A-2007-217997

The present invention has been proposed in view of the above-mentioned problems of the prior art, and the cement-based injection liquid as a suspension can permeate into the ground without being filtered, and can be constructed by a general-purpose machine. The purpose is to provide an injection method.

The injection method of the present invention is an injection method for improving by injecting a cement-based injection material (injection solution) into soft ground, and a cement-based injection material to which a polycarboxylic acid-based dispersant is added is selected as the cement-based injection material. It is characterized in that an aqueous solution of the polycarboxylic acid-based dispersant is injected before the cement-based injection material to which the polycarboxylic acid-based dispersant is added is injected.
In the present specification, the polycarboxylic acid may be referred to as "PC", the polycarboxylic acid-based dispersant may be referred to as "PC-based dispersant", and the polycarboxylic acid-based dispersant aqueous solution may be referred to as "PC-based dispersant aqueous solution".

In the present invention, as the cement-based solidifying material in the cement-based injection material to which the PC-based dispersant is added, for example, a commercially available product based on blast furnace slag (for example, trade name "Hyper NP1500" manufactured by Nippon Steel Cement Co., Ltd.) is used. I am using it. However, the cement-based solidifying material having a very small particle size of cement particles is not limited to the one based on the blast furnace slag, and the cement-based solidifying material based on other than the blast furnace slag can also be applied.
In the present invention, for example, soft sandy ground is exemplified, but the present invention is not limited to sandy ground, and the present invention is not limited to the present invention even if the ground particles are silt and (small amount) clay. Can be constructed.

In the present invention, it is preferable to inject water after injecting the PC-based dispersant aqueous solution and before injecting the cement-based injection material to which the PC-based dispersant has been added.
Further, in the present invention, the injection amount of the PC-based dispersant aqueous solution is such that the mass of the PC-based dispersant contained in the injected PC-based dispersant aqueous solution is the ground constituent particles in the construction region (ideally a spherical region). It is preferably 0.01% (mass%) or more of the mass of the above.
However, even if the mass of the PC-based dispersant contained in the pre-injected PC-based dispersant aqueous solution exceeds 0.5% by mass of the ground constituent particles in the construction area, the permeability does not improve and the economic efficiency is poor. .. Therefore, the injection amount of the PC-based dispersant aqueous solution is such that the mass of the PC-based dispersant contained in the injected PC-based dispersant aqueous solution is 0.5% (mass%) or less of the mass of the ground constituent particles in the construction area. Is preferable.

According to the present invention having the above-described configuration, a cement-based injection material to which a polycarboxylic acid-based dispersant (PC-based dispersant) is added is selected as the cement-based injection material, and a cement-based injection liquid as a suspension is used. A PC-based dispersant aqueous solution is injected prior to being injected into the ground.
A polycarboxylic acid (PC) -based dispersant is a polymer graft copolymer having a hydrophilic side chain in its chemical structure, and when it is adsorbed on the surface of cement particles, the side chain part expands hydrophilicly on the particle surface. When a layer of the PC-based dispersant is formed and the layers of the PC-based dispersant are overlapped with each other, a steric repulsive force is generated and the cement particles are dispersed.
Therefore, by injecting the PC-based dispersant aqueous solution into the ground to be constructed by the injection method in advance, the PC-based dispersant adheres to the surface of the ground constituent particles, and the PC-based dispersion is added to the cement-based injection material injected thereafter. Since the agent is attached to the cement particles, the cement particles are already in a state of being easily dispersed. In addition, a steric repulsive force acts between the PC-based dispersant adhering to the cement particles and the layer of the PC-based dispersant adhering to the ground constituent particles. As a result, it is presumed that the adhesion of cement particles and the clogging caused by the adhesion are eliminated, and the permeability of the injection liquid is improved.
Since the stock solution of the PC-based dispersant has a high viscosity and low permeability, the PC-based dispersant aqueous solution is injected after diluting with water when carrying out the present invention.

Here, when an injection liquid containing a cement-based solidifying material having a very small grain size of cement particles is used, the PC-based dispersant is dispersed by the PC-based dispersant in a floating state without adhering to the ground constituent particles. The concentration of the PC-based dispersant in the cement-based injection material may increase in the vicinity of the contact portion with the agent aqueous solution, which may cause material separation.
On the other hand, in the present invention, by injecting (water feeding) water after the prior injection of the PC-based dispersant aqueous solution, the PC-based dispersant in a floating state without adhering to the ground constituent particles due to the water is produced. It is removed and transferred farther than the injection method construction area. Therefore, it is presumed that the concentration of the PC-based dispersant in the cement-based injection liquid containing the cement-based solidifying material having a very small particle size of the cement particles did not increase, the material separation did not occur, and the permeability was improved. ..
In the experiment by the inventor, when a cement-based injection solution containing a cement-based solidifying material having a very small particle size of cement particles was used, water was injected (water-fed) after the prior injection of the PC-based dispersant aqueous solution. As a result, it was confirmed that the injection rate, which is a parameter expressing permeability, was improved by about 10% as compared with the case where water was not injected.

Here, in the present invention, the injection amount of the PC-based dispersant aqueous solution is such that the mass of the PC-based dispersant contained in the injected PC-based dispersant aqueous solution is 0.01 mass of the ground constituent particles in the construction area of the ground. If it is less than%, the effect cannot be fully exerted. Therefore, in the present invention, as the injection amount of the PC-based dispersant aqueous solution to be injected prior to the cement grout, the mass of the PC-based dispersant contained in the injected PC-based dispersant aqueous solution is used as the ground constituent particles in the construction area of the ground. When it is 0.01% by mass or more, the effect of improving the permeability is satisfactorily exhibited.
On the other hand, as the injection amount of the PC-based dispersant aqueous solution to be injected in advance, the mass of the PC-based dispersant contained in the injected PC-based dispersant aqueous solution is 0.5% by mass of the ground constituent particles in the construction area of the ground. Even if it exceeds, the permeability does not improve so much.

It is a flowchart which shows 1st Embodiment of this invention. It is a flowchart which shows the 2nd Embodiment of this invention. It is explanatory drawing which shows the experimental apparatus used in Experimental Example 1. FIG. It is a characteristic diagram which shows the result of Experimental Example 1. FIG. Similar to FIG. 4, it is a figure which shows the result of Experimental Example 1, and is the figure which expressed the result of each sample by a plot. It is a characteristic diagram which shows the result of Experimental Example 2. Similar to FIG. 6, it is a figure which shows the result of Experimental Example 2, and is the figure which expressed the result of each sample by a plot. It is a characteristic diagram which shows the result of Experimental Example 3. It is a characteristic diagram which shows the result of Experimental Example 4. It is explanatory drawing which shows the experimental apparatus used in Experimental Example 5. It is a characteristic diagram which shows the result of Experimental Example 5. It is a characteristic diagram which shows the result of Experimental Example 6. Similar to FIG. 12, it is a characteristic diagram showing the results of Experimental Example 6, and is a diagram in which the results of each sample are represented by plots.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The injection method according to the illustrated embodiment is preferably applied to, for example, ground improvement work on soft sandy ground. However, the ground to which the injection method according to the embodiment is applied is not limited to sandy ground, and the present invention can be applied even if the ground particles are sand, silt, or (small amount) clay.
In the illustrated embodiment and experimental example, as a cement-based solidifying material having a very small particle size of cement particles, for example, a commercially available product based on blast furnace slag (for example, trade name “Hyper NP1500” manufactured by Nippon Steel Cement Co., Ltd.). Is used. However, the cement-based solidifying material having a very small particle size of cement particles is not limited to the one based on the blast furnace slag, and the cement-based solidifying material based on other than the blast furnace slag can also be selected.

First, the first embodiment will be described with reference to FIG.
In FIG. 1 showing the work procedure, in step S1, the PC-based dispersant aqueous solution is injected into the ground. Here, since the stock solution of the PC-based dispersant has a high viscosity and low permeability, an aqueous solution of the PC-based dispersant obtained by diluting the stock solution with water is injected.
In the next step S2, a cement-based injection liquid as a suspension, for example, an injection liquid (grout) containing a cement-based solidifying material having a very small particle size of cement particles is injected into the ground.
Although not shown, at the stage of step S2, a cement-based injection material to which a PC-based dispersant was added (the amount of addition was, for example, 1.5% by mass of the cement-based solidifying material) was selected as the cement-based injection material. To.
As described above, the polycarboxylic acid (PC) -based dispersant is a polymer graft copolymer having a hydrophilic side chain in its chemical structure, and when adsorbed on the surface of cement particles, the side chain portion expands hydrophilicly. As a result, a layer of PC-based dispersant is formed on the particle surface, a steric repulsive force is generated between the overlapping layers, and the cement particles are dispersed. Therefore, when the cement-based injection material to which the PC-based dispersant is added is selected, the PC-based dispersant contained in the added PC-based dispersant adheres to the cement particles, and the cement particles are dispersed. In addition to that, the PC-based dispersant aqueous solution is injected in step S1 and the PC-based dispersant adheres to the surface of the ground constituent particles. Therefore, when the cement-based injection liquid to which the PC-based dispersant is added is injected in step S2, cement A steric repulsive force acts between the layer of the PC-based dispersant attached to the particles and the layer of the PC-based dispersant attached to the ground constituent particles. As a result, it is presumed that the adhesion of cement particles to the ground constituent particles and the blockage of the flow path due to clogging due to the adhesion were prevented, and the permeability of the cement-based injection liquid as a suspension was improved.

Next, the second embodiment will be described with reference to FIG.
In FIG. 2 showing the work procedure, in the first step S11, the PC-based dispersant aqueous solution is pre-injected into the ground as in the first embodiment, but in the second embodiment of FIG. 2, the PC-based dispersant aqueous solution is pre-injected. Water is injected into the ground in step S12 after the injection (water feeding).
After water feeding in step S12, the injection liquid is injected into the ground in step S13. Step S13 is the same step as step S2 of FIG.
In the first embodiment of FIG. 1, when a cement-based injection material containing a cement-based solidifying material having a very small particle size of cement particles is used as the cement-based injection material to which a PC-based dispersant is added, pre-injection is performed. A PC-based dispersant contained in the prepared PC-based dispersant aqueous solution, which is a cement-based solidifying material in which the PC-based dispersant in a suspended state without adhering to the ground constituent particles has a very small grain size of cement particles. Since it is contained in the cement-based injection material containing, the concentration of the PC-based dispersant in the cement-based injection may increase in the vicinity of the contact portion with the PC-based dispersant aqueous solution, which may cause material separation.
On the other hand, if water is injected (water is fed) after the prior injection of the PC-based dispersant aqueous solution (step S12 in FIG. 2), the PC-based dispersant in a floating state without adhering to the ground constituent particles It is removed by the injected water and transferred to an area separated from the construction area of the injection method. Therefore, in the construction area of the injection method, the concentration of the PC-based dispersant in the cement-based injection material containing the cement-based solidifying material having a very small particle size of the cement particles does not increase, and the material does not separate and penetrates. It is presumed that the sex has improved.

[Experimental Example 1]
In Experimental Example 1, the permeability of grout is measured using the penetration test apparatus shown in FIG.
Explaining the “penetration test using silica sand” with reference to FIG. 3, the permeation test apparatus 10 includes a permeation test cylinder 1, a support device 2, a beaker 3, and an electronic scale 4. The permeation test cylinder 1 is made of, for example, acrylic having a diameter of 55 mm and a length of 300 mm, and the internal space is filled with silica sand K. The permeation test cylinder 1 is supported at a predetermined position by the support device 2, and below the permeation test cylinder 1, a PC-based dispersant aqueous solution, water, and cement milk (which are dropped through the silica sand K filled in the test cylinder 1) ( The beaker 3 that receives the injection material) is arranged. The cement milk of Experimental Example 1 has W / C = 800%.
The beaker 3 is placed on the electronic scale 4, and the weight of the beaker 3 including the dropped water and cement milk is measured by the electronic scale, and the discharge amount of the measurement target such as the PC-based dispersant aqueous solution, water, and cement milk. , Calculate the discharge rate, etc. In FIG. 3, the electronic scale 4 is connected to the personal computer 5, and various measurement results by the electronic scale 4 are calculated and processed by the personal computer 5.

The procedure of Experimental Example 1 performed using the penetration test apparatus in FIG. 3 will be described below.
First, the permeation test cylinder 1 is filled with a predetermined amount of silica sand K (up to the middle of the permeation test cylinder 1) at a predetermined density. At that time, the silica sand K is in a dry state.
Next, water is slowly supplied to the vicinity of the upper end of the permeation test cylinder 1 (to the region above the silica sand filling region) (arrow A). The supplied water gradually permeates into the silica sand K and the water level drops, but water is constantly replenished to maintain the water level near the upper end of the permeation test cylinder 1. Then, the permeated water begins to be discharged from the lower part of the permeation test cylinder 1 (arrow B), and after the discharged amount becomes constant, water is injected for a predetermined time (for example, 5 minutes), and then the water injection is completed.
After that, when the water level drops to the upper end of the silica sand filling region in the permeation test cylinder 1, a predetermined amount of the PC-based dispersant aqueous solution is supplied as shown by arrow A.
Next, when the water level of the PC-based dispersant aqueous solution drops to the upper end of the silica sand-filled region in the permeation test cylinder 1, a predetermined amount of water is supplied (corresponding to "water feed": arrow A).

After that, when the water level of the water feed drops to the upper end of the silica sand filling region in the permeation test cylinder 1, cement milk (injection material) is supplied to the upper end of the permeation test cylinder 1 as shown by an arrow A. After the discharge of cement milk (injection material) (arrow B) is confirmed from the lower part of the permeation test cylinder 1, the liquid level of cement milk is maintained at the upper end of the permeation test cylinder 1 for a predetermined time (for example, 10 minutes), and a predetermined time is determined. After the end of the time, the supply of cement milk is terminated.
In the above-mentioned osmosis test, the water discharge rate (water discharge amount per minute) is obtained from the measurement result of the water discharge amount (drop amount) immediately before the end of water injection, for example, for 3 minutes. In addition, the cement milk discharge rate (cement milk discharge amount per minute) is calculated from the measurement result of the cement milk (injection material) discharge amount (drop amount) immediately before the end of cement milk supply, for example, for 3 minutes. To do. The measurement and calculation of the emission amount are executed by the electronic scale 4 and the personal computer 5.

In the permeation test of Experimental Example 1, the silica sand K filled in the permeation test cylinder 1 in the order of the PC-based dispersant aqueous solution, water (water supplied at the time of water feeding), and cement milk (injection material) according to the above-mentioned work procedure. When the supply of water (water feed) is omitted in the work procedure (corresponding to the first embodiment), when the supply of the PC-based dispersant aqueous solution is omitted. I went about.
In Experimental Example 1, an aqueous solution of a commercially available PC-based dispersant (trade name "ML-3000" manufactured by Nippon Steel Cement Co., Ltd.) was used as the aqueous solution of the PC-based dispersant. The mass of the PC-based dispersant in the first aqueous solution of the PC-based dispersant was 0.01% by mass, 0.09% by mass, and 0.47% by mass with respect to the mass of silica sand K used in the test. , 0.94 mass% was set.
Here, the mass of the silica sand K corresponds to the mass of the ground constituent particles in the construction area (ideally a spherical area) in the construction of the actual injection method.

In Experimental Example 1, the cement-based solidifying material in cement milk (cement-based injection material) is a cement-based solidifying material having a particle size of less than 3 μm and is manufactured by a commercially available product based on blast furnace slag (for example, Nippon Steel Cement Co., Ltd.). A commercially available PC-based dispersant (trade name "ML-3000" manufactured by Nippon Steel Cement Co., Ltd.) was added to the trade name "Hyper NP1500"). In Experimental Example 1, the amount of the PC-based dispersant added was 1.5% by mass of the cement-based solidifying material.
In FIG. 4, which shows the results of Experimental Example 1, the horizontal axis is "injection rate (discharge volume / gap volume) (%)", and the vertical axis is "discharge rate ratio (cement-based injection material / water) (%)". Is.
The "injection rate (discharge volume / gap volume) (%)" is the volume of the gap in the silica sand (that is, improvement) of the discharge volume of the cement-based injection material containing the cement-based solidifying material having a very small particle size of the cement particles. It is the ratio to the gap volume of the ground to be done), and the value increases with the passage of time of grout discharge.
On the other hand, the "discharge rate ratio (cement-based injection material / water) (%)" is the discharge rate of grout (cement milk), which is a cement-based solidifying material with a very small particle size of cement particles, divided by the water discharge rate. It is a value and is a numerical value that is an index for evaluating the permeability of a cement-based injection material containing a cement-based solidifying material having a very small grain size of cement particles. The larger the "discharge rate ratio", the better the permeability.

In FIG. 5, which shows the results of Experimental Example 1 in the same manner as in FIG. 4, the horizontal axis represents the “ratio of the prior injection PC to the test ground weight” (unit: mass%), and the vertical axis represents the “discharge rate ratio (cement-based injection)”. Material / water) (%) ”. The discharge rate ratio is a value obtained by dividing the permeation rate of the cement-based injection material containing the cement-based solidifying material by the permeation rate of water, and the particle size of the cement particles is very large as in the “discharge rate ratio” in FIG. This is a parameter that serves as an index for evaluating the permeability of a cement-based injection material containing a small cement-based solidifying material.
In FIG. 5, the relationship between the “ratio of pre-injected PC to the test ground weight (%)” and the “discharge rate ratio (cement-based injection material / water) (%)” of each sample at an injection rate of around 200% is shown in FIG. It is plotted and displayed. Here, the phrase "ratio of pre-injected PC" means the ratio of the mass of the PC-based dispersant to the test ground weight in the pre-injected PC-based dispersant aqueous solution.

The case where the PC-based dispersant aqueous solution is pre-injected is shown by the characteristic curves of 0.01%, 0.09%, 0.47%, and 0.94% in FIG. 4, and in FIG. 5, the pre-injected PC system is shown. Dispersants are shown in non-zero plots (plot on the vertical axis). When the PC-based dispersant aqueous solution is not pre-injected, the characteristic curve of "no prior injection" is shown in FIG. 4, and in FIG. 5, the mass of the PC-based dispersant in the pre-injected PC-based dispersant aqueous solution is relative to the test ground weight. It is shown in a plot with a zero ratio (plot on the vertical axis). As is clear from FIGS. 4 and 5, the discharge rate ratio and permeability are significantly improved when the PC-based dispersant aqueous solution is pre-injected as compared with the case where the PC-based dispersant aqueous solution is not pre-injected. There is.
However, as is particularly well shown in FIG. 5, when the mass of the PC-based dispersant in the prior-injected PC-based dispersant aqueous solution is less than 0.01% by mass with respect to the test ground weight, 0.1 mass is obtained. The effect of improving permeability is lower than that of% or more. On the other hand, even if the mass of the PC-based dispersant in the PC-based dispersant aqueous solution to be injected in advance exceeds 0.5% by mass with respect to the test ground weight, the effect of improving the permeability is not further improved, and the economy is improved. It turns out to be bad.
That is, if the mass of the PC-based dispersant in the PC-based dispersant aqueous solution to be injected in advance is 0.01% by mass or more of the ground constituent particles in the construction area, the permeability is improved. On the other hand, even if the mass of the PC-based dispersant in the PC-based dispersant aqueous solution to be injected in advance exceeds 0.5% by weight of the ground constituent particles, the permeability does not improve so much and the economy is poor.

In FIG. 4, when water is fed after the prior injection of the PC-based dispersant aqueous solution (characteristic curve other than “no water feeding” in FIG. 4), the injection rate is approximately 100% or more and the discharge rate ratio (penetration rate ratio) is It settled down to a certain value, and the characteristic curve became roughly parallel to the horizontal axis.
On the other hand, when water is not fed after the prior injection of the PC-based dispersant aqueous solution (characteristic curve of "no water feed" in FIG. 4), the discharge rate ratio continues to decrease as the injection rate increases (downward to the right). The discharge rate ratio did not settle to a constant value as in the case of water feeding.
When using an injection solution of a cement-based solidifying material with a very small particle size of cement particles, or when water is injected after prior injection of a PC-based dispersant aqueous solution (when water is fed), water is not injected. It is clear from FIGS. 4 and 5 that the discharge rate ratio, which is a parameter expressing permeability, is improved as compared with the case.
The effect of water feeding will be described in Experimental Example 6 with reference to FIGS. 12 and 13.

[Experimental Example 2]
In Experimental Example 2, the permeation test apparatus 10 used in Experimental Example 1 was used, and a PC-based dispersant different from the PC-based dispersant used in Experimental Example 1 (commercially available: product name “Polity” sold by Ryokukosan Co., Ltd. The permeability test was performed using XY-300M ").
In FIG. 7, which shows the results of Experimental Example 2, when an aqueous solution of the PC-based dispersant used in Experimental Example 1 (commercially available product: trade name “ML-3000” manufactured by Nippon Steel Cement Co., Ltd.) is injected, “◯” is shown. , Plot of "△" when an aqueous solution of the other type of PC-based dispersant (commercially available product: trade name "Polyty XY-300M" sold by Ryokukosan Co., Ltd.) is injected, preceded by the PC-based dispersant aqueous solution. When not injected, it is displayed as a "□" plot.
The W / C in the cement-based injection solution is 800%, and other test conditions are the same as in Experimental Example 1.
FIG. 6 showing the results of Experimental Example 2 is a graph corresponding to FIG. 4, and the horizontal axis and the vertical axis are the same as those in FIG. FIG. 7 is the same as that of FIG.
FIG. 7 shows the relationship between the “ratio of pre-injected PC to the test ground weight (%)” and the “discharge rate ratio (cement-based injection material / water) (%)” of each characteristic curve in the vicinity of the injection rate of 240% in FIG. Is plotted. A cement-based solidifying material having a particle size of less than 3 μm is used as the solidifying material.

Characteristic curves when the PC-based dispersant aqueous solution is pre-injected (characteristic curves of 0.01%, 0.09%, 0.47% in FIG. 6), plots in which the pre-injected PC-based dispersant is non-zero in FIG. (Plots other than the vertical axis in FIG. 7) are a characteristic curve in which the PC-based dispersant aqueous solution is not pre-injected (characteristic curve of “no prior injection” in FIG. 6), and a plot in which the pre-injection PC is zero in FIG. Compared with the plot on the vertical axis of), the discharge rate ratio and permeability are significantly improved.
Further, as shown in FIG. 7, the concentration (mass) of the PC-based dispersant in the PC-based dispersant aqueous solution to be injected in advance is less than 0.01% by mass (the vertical axis in FIG. 7 and the plot on the immediate right side of the vertical axis). The property is inferior to the permeability of 0.01% by mass or more (plot in the region where the value on the horizontal axis in FIG. 7 is 0.10 or more). On the other hand, even if the PC concentration (mass) to be injected in advance exceeds 0.5% by mass, the permeability is not improved, and the economic efficiency is poor because the PC is mixed in excessively.
As described above, in Experimental Example 2 shown in FIGS. 6 and 7, similarly to Experimental Example 1 in FIGS. 4 and 5, if an aqueous solution of the PC-based dispersant is pre-injected as the dispersant to be pre-injected, the PC system is used. It was confirmed that the discharge rate ratio was significantly improved and the permeability was improved as compared with the case where the aqueous solution of the dispersant was not supplied in advance.

[Experimental Example 3]
In Experimental Example 1 and Experimental Example 2, relatively fine-grained silica sand (No. 7 silica sand) was used.
On the other hand, in Experimental Example 3, "Special No. 7 silica sand" having a finer mesh than the silica sand (No. 7 silica sand) used in Experiment Examples 1 and 2 was used. Further, in Experimental Example 3, the same PC-based dispersant as in Experimental Example 1 is used, and other test conditions (including the test apparatus) are the same as in Experimental Example 1 (FIGS. 4 and 5). In Experimental Example 3, a cement-based solidifying material having a particle size of less than 3 μm is used as the solidifying material.
FIG. 8 showing the results of Experimental Example 3 is a characteristic diagram corresponding to FIG. 4, and the horizontal axis and the vertical axis are the same as those in FIG.
As is clear from FIG. 8, in Experimental Example 3, even if the injection rate increases (even if the grout discharge time elapses), the discharge rate ratio, that is, the permeability, continues to decrease and settles at a constant value. It did not (it did not become parallel to the horizontal axis). It is presumed that the reason why the permeability did not settle to a constant value was that there were many parts where the flow path of the injection material was smaller than the particle size of the cement particles, causing clogging.

However, as is clear from FIG. 8, when the PC-based dispersant aqueous solution is pre-injected, the discharge rate ratio is increased and the permeability is significantly higher than that when the PC-based dispersant aqueous solution is not pre-injected. It is improving. That is, it was found that if the PC-based dispersant aqueous solution was injected in advance, the permeability of the cement-based injection solution was improved even in the ground composed of fine-grained soil particles.
In FIG. 8, when the mass of the PC-based dispersant in the PC-based dispersant aqueous solution to be injected in advance is 0.47% by mass with respect to the test ground weight (characteristic curve of 0.47% with prior injection), the PC-based There is no significant difference in the effect of improving permeability when the mass of the PC-based dispersant in the dispersant aqueous solution is 0.94% with respect to the test ground weight (characteristic curve of 0.94% with prior injection). It was.

[Experimental Example 4]
In Experimental Examples 1 to 3, the silica sand corresponding to the ground is No. 7 silica sand, and the cement-based solidifying material is a commercially available product based on blast furnace slag and having a particle size of less than 3 μm (manufactured by Nippon Steel Cement Co., Ltd.). The product name "Hyper NP1500") is used.
On the other hand, in Experimental Example 4, as a cement-based injection material, a commercially available product (manufactured by Nippon Steel Cement Co., Ltd.) having a coarser particle size than the cement-based solidifying material used in Experimental Examples 1 to 3 and having a particle size of less than 10 μm. A cement-based injection material containing the trade name "Nippon Steel Super Fine") was used. As the particle size of the cement particles increased, in Experimental Example 4, No. 5 silica sand having a coarser particle size than the silica sand used in Experimental Examples 1 to 3 was used.
The PC-based dispersant used in Experimental Example 4 is the same as the polycarboxylic acid-based dispersant used in Experimental Example 1.
In Experimental Example 4, the ratio of the pre-injected PC-based dispersant to the test ground weight is 0.31%. The dispersant addition rate is 0.5%, and the W / C in the cement-based injection liquid is 800%.
In Experimental Example 4, the test ground length is 23 cm, which is different from the test equipment used in Experimental Examples 1 to 3.

In FIG. 9, which shows the results of Experimental Example 4, the case where the PC-based dispersant aqueous solution is pre-injected (“pre-injection”) is compared with the case where the PC-based dispersant aqueous solution is not pre-injected (characteristic curve of “no prior injection”). The discharge rate ratio in the characteristic curve of "with water feed") is significantly increased, and even if the particle size of the cement particles becomes large, the PC-based dispersant aqueous solution should be injected in advance, and then water feed should be performed. Was confirmed to be effective in improving permeability. In other words, it was confirmed that the present invention is effective even when the particle size of the cement particles is increased.

[Experimental Example 5]
In Experimental Examples 1 to 4, the cement-based injection solution, the PC-based dispersant aqueous solution, and water are naturally dropped.
On the other hand, in Experimental Example 5, the cement-based injection solution, the PC-based dispersant aqueous solution, and water are injected under pressure.
The test apparatus used in Experimental Example 5 will be described with reference to FIG.
In FIG. 10, the permeation test apparatus 20 includes a permeation test cylinder 11, a support device 12, a beaker 13, an electronic scale 14, a mixer 16, and a compressor 17. The permeation test cylinder 11 is made of acrylic having a diameter of 50 mm and a length of 1000 mm, for example, and the entire inside of the permeation test cylinder 11 is filled with silica sand K. The penetration test cylinder 11 is supported at a predetermined position by the support device 12.

The mixer 16 is connected to the compressor 17. A pipe 18 is arranged from the mixer 16 to the inflow port 11A on the lower surface of the penetration test cylinder 11, and the mixer 16 and the penetration test cylinder 11 are connected to each other.
A discharge port 11B is provided on the upper end surface of the penetration test cylinder 11, a pipe 19 is arranged from the discharge port 11B to a position above the beaker 13, and the discharge port 11B of the penetration test cylinder 11 is connected to the beaker 13 via the pipe 19. Communicating.
The beaker 13 is arranged on the electronic scale 14, and the weight of the beaker 13 including the dropped liquid (water, cement milk, etc.) is measured by the electronic scale 14.
A personal computer 15 is connected to the electronic scale 14, and the measurement results of the electronic scale 14 are calculated and processed by the personal computer 15, and the discharge amount, discharge rate, etc. of various liquids (PC-based dispersant aqueous solution, water, injection liquid) to be measured, etc. Is determined.

In the permeation test in FIG. 10, the PC-based dispersant aqueous solution, water, and injection liquid to be injected in advance are added in this order. The PC-based dispersant aqueous solution, water, and injection liquid are pressurized to 0.1 MPa by the compressor 17 and the mixer 16, and are injected into the permeation test cylinder 11 (acrylic pipe) via the pipe 18 and the inflow port 11A (arrow C). , The liquid (water, PC aqueous solution, cement milk) is permeated (flowed) from the lower side to the upper side of the permeation test cylinder 11. The permeation test cylinder 11 is filled with silica sand K, and the PC-based dispersant aqueous solution, water, and injection liquid are supplied from below the permeation test cylinder 11.
The PC-based dispersant aqueous solution, water, and injection liquid supplied into the permeation test cylinder 11 and passed through the silica sand K are sent from above the permeation test cylinder 11 to above the beaker 13 via the discharge port 11B and the pipe 19. , Dropped into the beaker 13 (arrow D).

The measurement and calculation of the discharge amount and the discharge rate of the PC-based dispersant aqueous solution, water, and injection liquid are the same as in Experimental Example 1 of FIG.
When a predetermined amount of the PC-based dispersant aqueous solution is discharged, water is pressurized and injected, and when a predetermined amount of water is discharged, the injection solution is pressure-injected.

In Experimental Example 5, No. 7 silica sand is used as the test ground as in Experimental Example 1 and Experimental Example 2, and an injection material containing a cement-based solidifying material having a very small particle size of cement particles is used. As described above, the injection pressure is 0.1 MPa, and the W / C in the cement-based injection liquid is 800%. The amount of the PC-based dispersant used in Experimental Example 5 added to the solidifying material and the mass pre-injected are the same as in Experimental Example 1.
As is clear from FIG. 11 showing the results of Experimental Example 5, even when the PC-based dispersant aqueous solution, water, and the injection solution are pressure-injected, when the PC-based dispersant aqueous solution is injected in advance, the PC-based dispersion is dispersed. It was confirmed that the discharge rate ratio was significantly improved and the permeability was significantly improved as compared with the case where the agent aqueous solution was not injected in advance.

[Experimental Example 6]
Experimental Example 6 is an experiment for confirming the relationship between the amount of water supplied and the water permeability (permeability) in "water feeding" after the prior injection of the PC-based dispersant aqueous solution. As the test ground, No. 7 silica sand is used as in Experimental Examples 1 and 2, and an injection material containing a cement-based solidifying material having a very small particle size of cement particles is used. The cement-based solidifying material, the PC-based dispersant to be added, the amount thereof added, the type of the PC-based dispersant to be pre-injected, and the mass of the PC-based dispersant in the pre-injected aqueous solution are the same as in Experimental Example 1. As the test device, the device using natural dropping (Fig. 3) is used as in Experimental Examples 1 to 4.
In addition, the amount of water supplied in "water feeding" after the PC-based dispersant aqueous solution is injected in advance is the ratio of the amount of water supplied in "water feeding" to the gap volume (of the ground to be improved) in the construction area. ) Is 0% (no water is sent), 10%, 30%, 50%, and 100%.

In FIG. 12, which shows the results of Experimental Example 6, the horizontal axis and the vertical axis are the same as those in FIG. 4 (Experimental Example 1).
FIG. 13 is the same drawing as in FIG. 5, but in FIG. 13, the horizontal axis shows the “water supply rate (water supply amount / gap volume)” (%), and the vertical axis shows the “discharge rate ratio (cement-based injection material / cement-based injection material /”. Water) (%) ". "Water supply rate (water supply amount / gap volume)" (%) is the ratio of the water supply amount (water supply amount) to the volume of the silica sand gap.
Further, FIG. 13 shows the relationship between the “water supply rate (water supply amount / gap volume)” (%) and the “discharge rate ratio (cement-based injection material / water) (%)” of each sample at the predetermined injection rate in FIG. Is a plot.

As is clear from FIGS. 12 and 13, the discharge rate ratio (parameter related to water permeability) is better at the water supply rates of 10%, 30%, 50%, and 100% than at the water supply rate of 0%. .. That is, when an injection liquid containing a cement-based solidifying material to which a PC-based dispersant is added and the particle size of cement particles is very small is used, water is injected after the prior injection of the PC aqueous solution (water feed: water feed rate). By (10%, 30%, 50%, 100%), the water permeability is significantly improved as compared with the case where water is not injected (water supply rate is 0%).
Further, the permeability changes depending on the water transfer rate (10%, 30%, 50%, 100%), and in FIG. 13, the water transfer rate of 30% has the highest discharge rate ratio and good permeability.

In FIG. 12, if water is fed after the prior injection of the PC-based dispersant aqueous solution, the discharge rate ratio indicating water permeability settles at a constant value (becomes parallel to the horizontal axis), whereas the PC-based dispersant is dispersed. When water is not fed after the prior injection of the aqueous agent solution (characteristic curve of "water supply rate 0%"), the permeability ratio continues to decrease (characteristic of downward slope).
Further, also in FIGS. 12 and 13, as in Experimental Examples 1, 2, 3 and 5, the permeability when the PC-based dispersant aqueous solution is pre-injected is compared with the case where the PC-based dispersant aqueous solution is not pre-injected. Was confirmed to be significantly improved.

It should be added that the illustrated embodiment is merely an example and is not a description intended to limit the technical scope of the present invention.

1,11 ... Penetration test cylinder 2,12 ... Support device 3,13 ... Beaker 4,14 ... Electronic scale 5,15 ... Personal computer 16 ... Mixer 17 ... Compressor 10 , 20 ... Penetration test device K ... Silica sand

Claims (3)

In the injection method to improve by injecting a cement-based injection material into soft ground, a cement-based injection material to which a polycarboxylic acid-based dispersant was added was selected as the cement-based injection material, and a cement-based injection material to which a polycarboxylic acid-based dispersant was added was selected. An injection method characterized by injecting an aqueous solution of a polycarboxylic acid-based dispersant before injecting the injection material. The injection method according to claim 1, wherein water is injected after the injection of the polycarboxylic acid-based dispersant aqueous solution and before the injection of the cement-based injection material to which the polycarboxylic acid-based dispersant is added. The injection amount of the polycarboxylic acid-based dispersant aqueous solution is such that the mass of the polycarboxylic acid-based dispersant contained in the injected polycarboxylic acid-based dispersant aqueous solution is 0.01% by mass or more of the ground constituent particles in the construction area. The injection method according to any one of claims 1 and 2.

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