KR102105058B1 - Two-component thixotropic grout composition for backfilling having superior water resistance, and process of backfilling by using the same - Google Patents

Abstract

The present invention relates to a two-component backfilling grout composition consisting of: an A solution containing water, cement, an anti-separation agent, and a retarder; and a B solution containing water, a curing agent, and a stabilizer, and to a plastic grout backfilling injection method (AW-TG method) with excellent water resistance. The composition of the present invention does not be diluted or lost by groundwater in the operation of filling voids or cavities generated between underground structures such as underground tunnels and the ground, and long-term durability can be maintained without perfect filling and volume reduction by maintaining plasticity for a certain period of time.

Description

Two-component thixotropic grout composition for backfilling having superior water resistance, and process of backfilling by using the same}

The present invention relates to a two-part type backfill grout composition having improved water resistance and a plastic grout backfill injection method comprising the same.

Voids or cavities (cavities) generated during the construction of underground structures, such as underground tunnels, can cause ground subsidence or damage to the structure and ground deformation. Therefore, these cavities (recesses) must be quickly and reliably filled with backfilling materials. The properties required for these backfilling materials are: ① excellent in filling properties without dilution or loss by groundwater at the time of injection, and ② good flowability to corners. It must be tightly filled, ③ there should be little material separation, ④ the strength should be uniformly expressed above the strength of the ground, ⑤ there should be no volume reduction after hardening, and also the volume of the grout component is melted by groundwater to reduce the volume. There should be no phenomenon.

Among these, a great difficulty in the construction process of many sites when injecting the backfill material is that there is a large amount of groundwater or a flow of groundwater due to high water pressure. The existing widely adopted and under construction LW method has a problem that the gelation time is slow, and if it encounters groundwater at the moment of injection, it will not harden and will not be hardened and will not exert a backfill effect or will be lost by the flow of groundwater. have. Therefore, limited injection is impossible, and after gelation, the plasticization state is short, so the flow stops immediately and the phenomenon of crushing occurs due to external force, and a new gap or void remains, which prevents the groundwater flow from being completely blocked.

In addition, early strength is required to stabilize the underground structure, and in the case where there is a risk of drying due to exposure to outside air, especially in the backfilling of existing structures, there should be no decrease in strength even if the moisture in the grout decreases. Particularly important is filling property, and fluidity and penetration loss to the outside of the cavity are closely related to filling properties. Since these are contrary properties, how to satisfy these conditions, that is, liquidity is good, but that there is no one round out of the cavity and that it can be fully filled is also the ultimate goal in the field of co-filling.

In general, the LW type backfill material, which has been widely used, has been constructed in a two-liquid form consisting of a first liquid containing water, cement, and a stabilizer and a second liquid containing a curing agent in order to shorten and control the curing time. As the first solution, it mainly consists of cement as a strength developing agent, and consists of a swelling material bentonite and a stabilizer to improve fluidity to prevent bleeding and material separation of cement, and is a general silicate as a curing accelerator in the second solution. No. 3 has been used. The chemical formula of sodium silicate used at this time is Na ₂ OSiO ₂ , and the molar ratio of Na ₂ O and SiO ₂ is 1: 3, and exhibits a strong alkalinity of pH 12 or higher.

In order to solve various problems in the existing LW backfilling method, a plastic grouting method has been developed and the number of construction sites has been recently adopted. In general, the plastic backfill material has an advantage in that the gelation time is fast between 2-6 seconds, and thus, after gelation, the phenomenon of dilution or loss even after encountering groundwater can be greatly reduced.

In addition, while the holding time of the plastic state is about 30 seconds to 1 minute in the case of the conventional LW, the plastic grouting material is very long in the order of 5-30 minutes, so it has the advantage of filling the empty cavity (cavity) to the depth of the corner. .

However, in the related art, a problem in which the grout composition is diluted or loosened by contact with strong flowing groundwater is not complete, and thus a product having better water resistance is required. Also, most silicate grout is used as a curing agent or curing accelerator. The phenomenon that the sodium silicate component dissolves into the groundwater, that is, the volume decreases over time due to the dissolution of the alkali component, there is a need for improvement.

1. Republic of Korea Registered Patent No. 10-1359036 2. Korean Registered Patent No. 10-1224848 3. Korean Registered Patent No. 10-1820919

J. Korea Academia-Industrial Cooperation Society, V. 12, no. 9 p. 4223-4238, 2011, "Evaluation of plasticity grout's compounding properties and applicability in the field", Hakmoon Kim

Accordingly, the present invention is to solve the problems of the conventional grout injection material, including the problem of diluting or loosening the grout material in contact with a strongly flowing groundwater and the problem of a decrease in volume due to the leaching of alkali in the groundwater.

According to one aspect of the invention, (a) water 30-80% by weight, cement 20-70% by weight A liquid, and (b) water 19-59% by weight, curing agent 40-80% by weight, anionic polymer stabilizer Disclosed is a two-component backfill grout composition comprising 0.1-1.2% by weight of B solution in a volume ratio of 3-10: 1. At this time, based on 100 parts by weight of the A solution, 1-6 parts by weight of the material separation preventing agent and / or 0.1-0.6 parts by weight of the retarder may be included in the A solution as needed.

According to another aspect of the present invention, a plastic grout backfill injection method using the two-component backfill grout composition is disclosed.

The grout composition according to the present invention is not only improved in water resistance due to improved properties of dilution or loosening in contact with groundwater, but also exhibits an improved effect in long-term durability due to little change in volume over time.

1 is a graph showing the process of gelation and intensity expression of plastic grout.
2 is a photograph showing the properties of a plastic grout.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

One aspect of the present invention is (a) 30-80% by weight of water, 20-70% by weight of cement A, and (b) 19-59% by weight of water, 40-80% by weight of curing agent, anionic polymer stabilizer 0.1- It relates to a two-component backfill grout composition containing a B ratio containing 1.2% by weight in a volume ratio of 3-10: 1. At this time, based on 100 parts by weight of the A solution, 1-6 parts by weight of the material separation preventing agent and / or 0.1-0.6 parts by weight of the retarder may be included in the A solution as needed.

At this time, in the B solution, the curing agent solution and the anionic polymer stabilizer may be separately used as a dissolved solution. That is, the aqueous solution in which the curing agent is dissolved and the aqueous solution in which the anionic polymer stabilizer is separately dissolved may be separately mixed and used in the A solution.

Water used in the present invention is preferably fresh water, and when the content of water in Liquid A exceeds 80% by weight (based on the total weight of Liquid A) or 930 kg (based on the preparation of 1 m ^{3 of} composition), the total solid content is There is a disadvantage that the function as a grout is low due to too little strength after curing, and the concentration of the total solution is less than 30% by weight (based on the total weight of A solution) or 400 kg (based on 1 m ^{3 of} composition) There may be a problem that it is too high for pressure feeding and difficult to mix with B liquid. The preferred water content for Liquid A is 40-75% by weight.

According to one embodiment, the cement is Portland cement, or Portland cement is a functional cement in which one or more additives selected from slag powder, fly ash, and calcium compounds are mixed.

The cement content in Liquid A should be 20-70% by weight. More preferably, it is 25-60 weight%. If the content of cement is less than 20% by weight, the strength is weak and the function as a grout material is not exerted. If it exceeds 70% by weight, the fluidity of the A liquid is weak, which may cause a problem of difficult long-distance pressure feeding.

In the present invention, the material separation preventing agent means a material used to stably maintain the plastic state in the process of performing the plastic grout method in the art, and the action of preventing the material separation of cement and the plastic state paste (paste ) It acts to give cohesion.

In the present invention, the term "plasticity" or "plastic state" means an intermediate state between a liquid and a solid which, if left still, has no self-flowability but has fluidity when pressed.

Examples of the material separation preventing agent usable in the present invention may be a swellable clay mineral, especially bentonite.

The content of the material separation inhibitor may be 1-6 parts by weight based on 100 parts by weight of the A solution, and preferably 1-3 parts by weight. If the content of the material separation inhibitor is less than 1 part by weight (based on 100 parts by weight of A solution) or 10 kg (based on the production of 1 m ^{3 of the} composition), material separation may occur and there may be shortcomings in which the plastic state retention time is shortened. , If it exceeds 5 parts by weight (based on 100 parts by weight of A solution) or 60 kg (based on 1 m ^{3 of the} composition), the viscosity is too high, and there may be a problem that long-distance pressure is difficult.

Bentonite, one of the material separation inhibitors usable in the present invention, preferably has a swelling degree of 10 or more, more preferably a swelling degree of 20 or more, and even more preferably a swelling degree of 30-40. When the swelling degree of bentonite is less than 10, a material separation phenomenon may occur and there may be a disadvantage in that the holding time of the plastic state is shortened.

The retarder in the present invention can be used to prevent the phenomenon of clogging the pressure-feeding pipe by the self-hardening action of cement, during the pressure-feeding process for storage or handling after the preparation of A liquid. In the present invention, a retarder may be used a cement retarder commonly used in the art. When using a retarder, it is preferable to use 0.1-0.6 parts by weight based on 100 parts by weight of the A solution. If it is less than 0.1 part by weight, it is difficult to express the function of the retarder, and if it exceeds 0.6 parts by weight, there may be a problem that the strength is weakened for 1 hour.

In the present invention, the term "curing agent" refers to a material used to express the strength of the mixed solution as a liquid or gel in the process of performing the grout method in the art.

According to one embodiment, the curing agent may be at least one selected from sodium silicate or potassium silicate. In the present invention, the curing agent of Liquid B serves to rapidly cure Liquid A.

The content of the curing agent is 40-80% by weight based on the total weight of the B solution, and if it exceeds 80% by weight, the gelation time becomes slow and the plasticity is shortened. If it is less than 40% by weight, the strength is low and the backfilling performance is low. Falling problems can occur.

Sodium silicate or sodium silicate, one of the curing agents usable in the present invention, includes sodium silicate 1, 2 and 3 according to the KS standard (KS M 1415). In addition, in the curing agent usable in the present invention, a special sodium silicate solution, which is partially neutralized by diluting commonly used sodium silicate No. 3 with water, or by adding an acidic solution such as strong acid such as sulfuric acid or weak acid in the production process of sodium silicate, is partially neutralized. All inclusive. Furthermore, the special soda silicate solution curing agent usable in the present invention includes a curing agent according to Korean Patent Registration No. 10-1224848, as well as a curing agent prepared by mixing an acidic solution during a soda silicate manufacturing process, which is not a construction site.

On the other hand, one of the biggest features of the present invention is to prepare a liquid B further comprising an anionic polymer stabilizer. Through this, not only can the plastic backfill performance with excellent water resistance, which is also an object of the present invention be imparted, but also the volume change over time can be blocked or minimized to improve long-term durability.

In the present invention, the anionic polymer also includes an amphoteric polymer containing anionic.

In order to dissolve the anionic polymer stabilizer, it is necessary to control the water content to be 19-59 wt% in the B solution, and if the water content exceeds 59 wt%, the strength is weakened, and if it is less than 19 wt%, the fluidity of the B solution This may cause problems with long distance feeding.

In the present invention, it is preferable to use an anionic polymer material, and if a cationic polymer material or a nonionic polymer material is used, water resistance is not improved and long-term durability (volume change stability) is not improved. When using a polymer material, it was confirmed that at least one property of water resistance and long-term durability (volume change stability) was improved.

In the present invention, the anionic polymer stabilizer is particularly preferable to use a copolymer of acrylate and acrylamide, among other things, not only to improve water resistance, but at the same time, to minimize the volume reduction over time to improve long-term durability. This is because it can be improved with. In contrast, when (i) an anionic polymer material of a different type from the copolymer of acrylate and acrylamide, such as a polyacrylic acid or polyacrylate-based polymer, or (ii) using only polyacrylamide, Or (ii) it was confirmed that even if a blend of polyacrylate and polyacrylamide is used or a mixture thereof is used, it is difficult to simultaneously improve the water resistance or long-term durability desired in the present invention.

Examples of the copolymer of acrylate and acrylamide that can be used in the present invention include, but are not limited to, 2-propenate sodium 2-propeneamide polymer.

In the present invention, use in the form of an emulsion containing the above components may be preferable in that it can improve workability by increasing solubility.

The content of the anionic polymer stabilizer may be 0.1-1.2% by weight based on the total weight of the B solution, preferably 0.3-1.1% by weight. If it exceeds 1.2% by weight, the viscosity may be too high, and long-distance pressure feeding may be difficult. If it is less than 0.1% by weight, water resistance may be weakened, which may dilute the groundwater, and stability of volume change may be deteriorated.

According to another embodiment, the composition comprises A and B liquids in a volume ratio of 3-10: 1, more preferably in a volume ratio of 4-9: 1, and most preferably in a volume ratio of 4-7 do. If the volume ratio of Liquid A and Liquid B is less than 3: 1, the concentration of Liquid B may be too high, which may cause a longer gelation time. If the volume ratio exceeds 10: 1, the initial strength is too low to be washed out by groundwater pressure. There are disadvantages.

According to another embodiment, the composition has a gelation time of less than 20 seconds, more preferably 1-10 seconds, and most preferably 3-10 seconds. When A and B are mixed and the gelation time is slower than 20 seconds, the grout material is injected into the liquid instead of the plastic state when the grout is injected into the underground cavity through which the groundwater flows, so it may be easily lost and there is a problem that the cavity is not filled.

According to another embodiment, the composition has a plastic holding time of 5-30 minutes, more preferably 5-25 minutes. If the calcined state is shorter than 5 minutes, the holding time of the calcined state is short, and the backfill material hardens without flowing anymore until it fills the deep pores of the ground, so there is a disadvantage that the pores remain, and the calcined state becomes longer than 30 minutes. When the gel strength is too weak, there is a problem that limited injection is difficult and material loss is increased.

According to another embodiment, the composition has an hour strength of 0.2-3 kg / cm ² , more preferably 0.3-2 kg / cm ² . If the initial strength of 1 hour strength is less than 0.2 kg / cm ² , the plasticity is broken by the high water pressure ground water and washed in the ground water, so it is difficult to block the flow of ground water.If it exceeds 3 kg / cm ² There is a disadvantage in that it is difficult to completely fill the empty voids in the basement because the holding time of the plasticized state is shortened.

According to another embodiment, the composition has a 28-day strength of 15-50 kg / cm ² , more preferably 17-40 kg / cm ² . When the 28-day strength of the grout material is less than 15 kg / cm ² , the strength to protect the underground structure from external pressure is weak, and when it exceeds 50 kg / cm ² , the strength is too high, which causes difficulties in the rebuilding process of the underground structure. There is a problem.

According to another embodiment, (i) the material separation inhibitor is bentonite, (ii) the bentonite has a swelling degree of 10 or more, (iii) the curing agent is sodium silicate, and (iv) the anionic polymer stabilizer Sodium 2-propenate 2-propeneamide polymer, (v) the liquid A contains 40-75% by weight of water, 25-60% by weight of cement, (vi) bentonite material based on 100 parts by weight of the liquid A The separation preventing agent 1-3 parts by weight is included in the liquid A, (vii) the liquid B contains 19-59% by weight of water, 40-80% by weight of the curing agent, and 0.3-1.1% by weight of the anionic polymer stabilizer, (viii ) The volume ratio of the A solution and the B solution is 4-9: 1.

At this time, the plastic grout composition for backfilling had a gelation time of 1-10 seconds, a plastic holding time of 5-25 minutes, an hour strength of 0.3-2 kg / cm ² , and a 28-day strength of 17-40 kg / cm ² . You can be satisfied at the same time.

As a result of carrying out numerous experiments through various types of materials and various composition changes, not only the physical properties of the above composition but also excellent water resistance and time are achieved only when the conditions (i) to (viii) are all satisfied as above. The volume reduction phenomenon did not occur at all to the extent that a slight increase in volume was observed over the past, but the above conditions (i) to (viii) were used, such as using other substances of similar function or using a composition outside the above range. When any one of the above is not satisfied, it was confirmed that the physical properties and water resistance of the above composition and the volume change stability as described above cannot be simultaneously achieved.

Another aspect of the present invention is (A) preparing a liquid A by adding cement to water, (B) adding a curing agent and anionic polymer stabilizer to water and mixing to prepare a liquid B, (C) above It relates to a plastic grout injection method excellent in water resistance comprising the step of mixing the A solution and the B solution at a volume ratio of 3-10: 1, mixing at the end of the injection port and injecting it into the void or cavity.

Since the method of the present invention uses a two-liquid backfill grout composition according to various embodiments of the present invention, descriptions common to the two are omitted to avoid excessive complexity of the present specification.

Hereinafter, the present invention will be described in more detail through examples and the like, but the scope and content of the present invention may be reduced or limited by the examples below. In addition, if it is based on the disclosure of the present invention including the following examples, it is obvious that a person skilled in the art can easily carry out the present invention in which experimental results are not specifically presented, and patents to which such modifications and corrections are attached Naturally, it is within the scope of the claims.

In addition, the experimental results presented below are only representative of experimental results of the examples and comparative examples, and the effects of the various embodiments of the present invention, which are not explicitly presented below, will be described in detail in the corresponding parts.

Example

Example 1: Preparation of a two-component grout composition for a plastic grout method (AW-TG method) having excellent water resistance (for low strength)

According to the low-strength composition shown in Table 1, a grouting material was added to bentonite having a swelling degree of 30 or more in water per 1 m ^3, stirred and aged for 3 minutes or more, and then added functional cement to prepare Liquid A. Liquid B was prepared in the same manner as the composition shown in Table 1 below. Sodium 2-propenate 2-propeneamide polymer was used in the form of an emulsion. The prepared A solution and B solution were mixed at a ratio of 6: 1 by volume ratio, and experiments were conducted according to test items to measure properties.

Example  2: Plastic grout construction method with excellent water resistance ( AW -TG method) 2 component type  Preparation of grout composition (for high strength)

A and B liquids were prepared in the same manner as in Example 1 above, except that the compositions listed in Table 1 above were of a high strength composition rather than a low strength composition, and mixed in a ratio of 4: 1 by volume ratio. .

Example 3: Preparation of a two-component grout composition for a plastic grout method (AW-TG method)

Example 1 and above, except that instead of using a 2-propene acid sodium 2-propeneamide polymer as a stabilizer in the low-strength composition ratio of Example 1, using another anionic polymer polyacrylate Liquids A and B were prepared in the same manner and experiments were conducted.

Example 4: Preparation of a two-component grout composition for a plastic grout method (AW-TG method)

Liquid A and Liquid B were prepared in the same manner as in Example 1, except that 2 kg (0.2 wt%) was used instead of 5 kg (0.5 wt%) of the anionic polymer in Example 1 above. Was conducted.

Example 5: Preparation of two-component grout composition for plastic grout method (AW-TG method)

Liquid A and Liquid B were prepared in the same manner as in Example 1, except that in the Example 1, 230 kg (25.1 wt%) was used instead of 300 kg (30.5 wt%) of the plastic cement. It was carried out.

Example 6: Preparation of a two-component grout composition for a plastic grout method (AW-TG method)

Except for using 45 kg (4.92 parts by weight compared to 100 parts by weight of A solution) instead of using 15 kg (1.64 parts by weight of 100 parts by weight of A solution) special bentonite in the composition ratio for low strength of Example 1 above, Liquid A and Liquid B were prepared in the same manner as in Example 1, and experiments were conducted.

Example 7: Preparation of a two-component grout composition for a plastic grout method (AW-TG method)

The experiments were conducted in the same manner as in Example 1, except that the A and B liquids prepared in Example 1 were mixed at 8: 1 rather than at a volume ratio of 6: 1.

Comparative Example 1: Preparation of a two-component grout composition for the existing LW method

A solution was prepared according to the composition shown in Table 1, and then a sample was prepared by mixing the measured amount of B solution with the total amount of A solution.

Comparative Example 2: Preparation of a two-component grout composition for the existing plastic grout method (TG method)

A liquid was prepared according to the composition shown in Table 1, and then the weighed B liquid was mixed to make a sample to perform a comparative test.

Test Examples 1, 2, 3, 4 and Comparative Test Examples 1, 2

Using the two-component composition prepared in Examples 1, 2, 3, 4 and Comparative Examples 1 and 2, respectively, the physical properties below were measured.

(1) Measurement of gelation time

Put 350 g of the A solution in a vertically long plastic bag, fold the plastic bag around the height of the A solution, and then add the B solution according to the ratio so that the A solution and the B solution are separated, and tighten the plastic bag opening. At the same time as the gel time starts, release the hand held between Liquid A and Liquid B, hold the plastic bag vertically and shake it up and down, while Liquid A and Liquid B meet and react, and no longer fluidity is felt. It was decided.

(2) Holding time

After measuring the gel time, after 5 minutes, the bottom edge of the plastic bag was cut to a diameter of about 2 cm, and it was confirmed that the material discharged when the plastic bag was squeezed with both hands was released into a plastic state without breaking and crumbs.

(3) Measurement of one-axis compressive strength

To measure the compressive strength, specimens were made with a cubic mold having a width of 50 mm ㅧ 50 mm and measured according to the compressive strength test method of KS L 5105 hydraulic cement mortar.

(4) Water resistance experiment

As a method of confirming whether it is non-separated in water, when the A and B liquids are mixed in a designed ratio in a transparent glass beaker containing fresh water and the sample is added before or after the gel is formed, the backfill material is diluted in water or It was tested whether it becomes loose and becomes cloudy.

(5) Volume change evaluation

Volumetric deformation through curing in water and in air was measured. The volumetric deformation amount was measured by observing the change in volume of the specimen over time by measuring the change in diameter and height of the specimen while drying in air for 7 days after fabrication of the specimen.

As shown in Table 2 above, in the case of Examples 1 and 2, it can be seen that the water resistance was significantly improved before gelation compared to Examples 3 and 4 and Comparative Examples 1 and 2, and after gelation, there was no loosening in a perfect state. It can be seen that it is maintained.

In the volume change, as shown in Table 3 below, in the case of Examples 1 and 2, the volume reduction phenomenon did not occur at all so that the volume change was observed to be increased very slightly, and the comparison was also made in Examples 3 to 7. It was confirmed that the volume reduction was significantly reduced compared to Examples 1 and 2.

Claims (12)

As a grout composition for a two-pack type backfill comprising the following solution A and the following solution B in a volume ratio of 4-9: 1:
(a) Liquid A containing 40-75% by weight of water and 25-60% by weight of cement,
(b) Liquid B containing 19-59% by weight of water, 40-80% by weight of curing agent, and 0.3-1.1% by weight of anionic polymer stabilizer;
The cement is Portland cement, or Portland cement is a functional cement in which one or more additives selected from slag powder, fly ash, and calcium compounds are mixed,
The curing agent is sodium silicate,
The anionic polymer stabilizer is 2-propene sodium 2-propeneamide polymer,
1-3 parts by weight of the material separation inhibitor based on 100 parts by weight of the A solution is included in the A solution,
The material separation inhibitor is a two-component backfill grout composition, characterized in that the swelling degree is 10 or more bentonite. delete The grout composition for a two-pack backfill according to claim 1, wherein 0.1-0.6 parts by weight of the retarder is contained in the A solution based on 100 parts by weight of the A solution. delete delete The method of claim 1, wherein the two-component grout composition for backfilling has a gelation time of 1-10 seconds, a plasticity retention time of 5-25 minutes, an hour strength of 0.3-2 kg / cm ^2, and a strength of 28 days. The grout composition for a two-pack backfill, characterized in that 17-40 kg / cm ² . As a plastic grout backfill injection method comprising the steps (A) to (C):
(A) After adding a material separation inhibitor to water and stirring, adding cement to prepare Liquid A,
(B) preparing a liquid B by adding a curing agent and an anionic polymer stabilizer to water and mixing,
(C) a step of feeding the grout composition for a two-pack type backfill containing the solution A and the solution B in a volume ratio of 4-9: 1, mixing at the end of the inlet and injecting it into the void or cavity;
The liquid A contains 40-75% by weight of the water and 25-60% by weight of the cement,
The liquid B contains 19-59% by weight of the water, 40-80% by weight of the curing agent, and 0.3-1.1% by weight of the anionic polymer stabilizer,
The cement is Portland cement, or Portland cement is a functional cement in which one or more additives selected from slag powder, fly ash, and calcium compounds are mixed,
The curing agent is sodium silicate,
The anionic polymer stabilizer is 2-propene sodium 2-propeneamide polymer,
1-3 parts by weight of the material separation inhibitor based on 100 parts by weight of the A solution is included in the A solution,
The material separation inhibitor is a plastic grout backfill injection method, characterized in that the swelling degree is 10 or more bentonite. delete The plastic grout backfill injection method according to claim 7, wherein 0.1-0.6 parts by weight of the retarder is included in the A solution based on 100 parts by weight of the A solution. delete delete The method of claim 7, wherein the two-component grout composition for backfilling has a gelation time of 1-10 seconds, a plasticity retention time of 5-25 minutes, an hour strength of 0.3-2 kg / cm ^2, and a strength of 28 days. The plastic grout backfill injection method, characterized in that 17-40 kg / cm ² .

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