JPS629154B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of stabilizing ground by improved silicate grafting. Conventionally, chemical injection methods (grouting methods) have been known in which various chemical solutions are injected into the ground and hardened in the ground in order to strengthen soft ground or stop water flowing from springs. The so-called silicate-based graft, which is a chemical solution consisting of an aqueous solution as the main ingredient and a curing agent mixed therein, has been widely put into practical use because it is inexpensive and less dangerous than other chemical grouts. ing. Recent trends in chemical injection methods include research to develop grouts with even better performance, and at the same time, more reliable and safer construction methods are being developed. For example, the conventional construction method is to inject grout with a gel time of several minutes to several tens of minutes into the ground, allowing the grout to fully penetrate into the gaps between soil particles and then hardening, which is the so-called penetration injection method. However, if grout with a gel time of several minutes or more is injected into the ground, depending on the ground, the grout may leak into the ground outside the construction site before it hardens, making the construction process uncertain. There is a risk that grout may flow into groundwater or well water and cause pollution problems, so in order to prevent such problems, grout is poured into the ground and hardened within a short period of a few seconds to more than 10 seconds. A construction method called the instant connection method was developed. According to this instant setting method, there is no risk that the grout injected into the ground will flow into the ground other than the construction site or mix with well water, groundwater, etc.; Since it is injected into the ground, the grout does not penetrate sufficiently into the gaps between soil particles, resulting in a much worse mixing condition of the grout and soil than in the case of the infiltration injection method. Therefore, when the ground is stabilized by the instant setting method, the strength of the treated soil is low, and there is a risk that the ground will collapse when the soil is excavated. Also,
When conventional silicate-based grout is applied to the instant setting method, the initial strength of the hardened product is low, so if the grout is injected into the ground with heavy flowing water, the hardened product may flow out. The present invention is a method for stabilizing the ground using a silicate-based grout that does not exhibit the above-mentioned drawbacks even when applied to the instant bonding method. In the instant setting method, grout consisting of a mixture of (a) lime, (b) dihydrate gypsum, and alpha hemihydrate is injected into the ground and hardens within a few seconds to tens of seconds to stabilize the ground. At least one selected from the group consisting of gypsum, β-hemihydrate gypsum, and type anhydrite
A hardening agent made by mixing seed gypsum in a ratio of (a) and (b) = 1:3 to 3:1 (weight ratio) is mixed with sodium silicate: purity 1
A method for stabilizing the ground characterized by using 0.7 to 3.6 parts by weight per part by weight. The main ingredient is aqueous sodium silicate solution, and the hardening agents are lime, dihydrate gypsum, α-hemihydrate gypsum, β-hemihydrate gypsum,
Grouts containing type anhydrous gypsum are conventionally known, but among these grouts, when grouts containing lime, dihydrate gypsum, etc. as hardeners are applied to the instant setting method, the strength of the treated soil is low and The ground easily collapses due to excavation, and even if we try to apply grout using hardeners such as α-hemihydrate gypsum, β-hemihydrate gypsum, and type anhydrite to the instant setting method, the viscosity of the grout is too high and it is difficult to inject into the ground. Have difficulty. However, according to the research of the present inventors, lime and at least one type of gypsum selected from the group consisting of dihydrate gypsum, α-hemihydrate gypsum, β-hemihydrate gypsum, and type anhydrite are mixed in a ratio of 1:3 to 1:3 by weight. A grout made by combining a 3:1 mixture with a sodium silicate aqueous solution has a low viscosity and is easy to inject into the ground, and when this grout is used to stabilize the ground using the instant setting method, the treated soil It was discovered that the strength of the ground is high, and that the instantaneous bonding method can stabilize the ground more favorably than conventional methods. The present invention was completed based on this knowledge, and according to the present invention, the soil strength after stabilization treatment is sufficiently high, so there is no fear that the ground will collapse during excavation after treatment, and the grout used in the present invention is Since the initial strength of the hardened product is high, the hardened product will not be washed away even when the grout is injected into the ground where there is heavy running water. To explain the grout used in the present invention,
As the sodium silicate, sodium silicate with a molar ratio of SiO ₂ /Na ₂ O of 2 to 4, which is conventionally used in silicate grouts, can be used, but usually JIS, K
-1408, No. 1 to No. 3 sodium silicate, particularly No. 3 sodium silicate, is preferably used. These sodium silicates are generally in the form of an aqueous solution, but at the time of construction, they are further diluted with water to form an aqueous solution with an appropriate concentration suitable for ground stabilization. For example, JIS No. 3 silicic acid is used as a source of sodium silicate in the usual construction method, in which equal volumes of a sodium silicate aqueous solution (liquid A) and a slurry made by dissolving a hardening agent in water (liquid B) are mixed and injected into the ground. When soda is used, 40 to 180 parts by volume of the sodium silicate is diluted with water to make 200 parts by volume and used as liquid A. The higher the concentration of sodium silicate in Solution A, the greater the strength of the treated soil. In the present invention, lime (hereinafter referred to as component (a)), dihydrate gypsum, α-hemihydrate gypsum,
A mixture of at least one type of gypsum (hereinafter referred to as component (b)) selected from the group consisting of β-hemihydrate gypsum and type anhydrite in a weight ratio of 1:3 to 3:1 (hereinafter referred to as the present invention). curing agent). Figure 1 shows a mixture of liquid A consisting of a mixture of 100 ml of JIS No. 3 sodium silicate and 100 ml of water, and liquid B (200 ml) consisting of an equal volume of slurry of the curing agent of the present invention, and after the mixture has hardened. This is a diagram showing the relationship between the strength of the cured product measured after 60 minutes and the curing agent composition. The horizontal axis of the diagram shows the mixing ratio (weight) of components (a) and (b), and the vertical axis shows the curing Indicates the unconfined compressive strength of an object. Curve 1 represents the case where 120g of a mixture of slaked lime and dihydrate gypsum is contained in liquid B, curve 2 represents the case where 120g of a mixture of slaked lime and α-hemihydrate gypsum is contained in liquid B, and curve 3 represents the case where 120g of a mixture of slaked lime and α-hemihydrate gypsum is contained in liquid B. Each case is shown in which 100g of a mixture of slaked lime and type anhydrite is contained in liquid B. As is clear from Figure 1, when the sodium silicate aqueous solution is cured using each component (a) and (b) alone, the strength of the curing agent is small, but when both components (a) and (b) are used in combination, the strength of the curing agent is low. When the sodium silicate aqueous solution is cured, the strength of the cured product increases, and the mixing ratio of (a) and (b) is 1:3 to 3:1.
In this case, the strength of the cured product is the highest. Examples of the component (a) used in the present invention include slaked lime and quicklime, which can also be used in combination. Any type of gypsum dihydrate, gypsum α hemihydrate, and gypsum β hemihydrate used as component (b) in the present invention can be used, but it is usually used during the production of phosphoric acid, hydrofluoric acid, ammonium sulfate, etc. or during salt production. and titanium smelting,
Chemical gypsum, which is produced as a by-product during flue gas desulfurization, is preferably used. The type anhydrite used as component (b) in the present invention is obtained by firing gypsum dihydrate or gypsum hemihydrate at a temperature of 400°C or higher, and is usually used during wet phosphoric acid production or during flue gas desulfurization. A material obtained by firing gypsum dihydrate, gypsum hemihydrate, etc., which are sometimes by-products, is preferred because it is cheap and easily available, but imported natural anhydrite, etc., for example, can also be used. The amount of the curing agent used in the present invention is varied depending on the gel time of the grout; more is used when the gel time is to be shortened, and less is used when the gel time is to be lengthened. For example, when the ground is stabilized with a grout (400) made of a mixture of JIS No. 3 sodium silicate 100% and water 100% A liquid (200) and an equal volume of the hardener slurry of the present invention (B liquid, 200). In this case, 40 to 180 kg of the curing agent of the present invention is contained in liquid B. This allows the grout to harden in the ground in a few seconds to more than ten seconds. Since JIS No. 3 Sodium Silicate 100 usually contains 50 to 56 kg of sodium silicate in terms of pure content, the curing agent of the present invention is added per 1 part by weight of sodium silicate in pure terms.
By using it in a proportion of 0.7 to 3.6 parts by weight, the curing time of the grout can be adjusted from several seconds to more than ten seconds. To explain the soil injection method for grout in implementing the present invention, first, before construction, a sodium silicate aqueous solution (A
Liquid) and the curing agent slurry of the present invention (Liquid B) are prepared in respective dedicated tanks, and then, during construction, the two are mixed and injected into the ground. When stabilizing the ground using the instant bonding method, various methods have been proposed for injecting grout into the ground. The commonly used method is to pour liquid A and liquid separately into the pipe, mix the two liquids in a mixer at the tip, and then immediately inject them into the ground. It is preferable to adopt such a method in the present invention as well. The present invention will be explained below using examples. Example 100 ml of water was added to 100 ml of JIS No. 3 sodium silicate to dissolve it, and this was used as liquid A. On the other hand, 200 ml of curing agent slurries of the present invention having various concentrations as shown in Table 1 were prepared and used as liquid B. The results of measuring the gel time and unconfined compressive strength of the cured product (homogel) when both liquids A and B were mixed and cured at a temperature of 5°C, and when the mixture A and B were mixed with the same weight of standard sand. Table 1 shows the results of measuring the unconfined compressive strength of the sand gel obtained by curing. For comparison, a liquid B consisting of a slurry of both components a and b constituting the curing agent of the present invention was prepared, and a mixture of equal volumes of this and the liquid A was subjected to the same test as above. The first
Also listed in the table. 【table】

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the uniaxial compressive strength of the cured product obtained by curing the grout used in the present invention and the curing agent composition, and the horizontal axis of the figure is the curing agent composition [(a) Weight mixing ratio of component and component (b)]
, the vertical axis indicates the uniaxial compressive strength of the cured product. Moreover, the symbols in the figure are as follows.

【table】

Claims (1)

[Scope of Claims] 1. An instant setting method in which a grout made of a mixture of a sodium silicate aqueous solution as a main ingredient and a hardening agent is injected into the ground and hardened within a few seconds to more than ten seconds to stabilize the ground, (a) lime and (b) at least one type of gypsum selected from the group consisting of dihydrate gypsum, alpha hemihydrate gypsum, beta hemihydrate gypsum, and type anhydrite (a):(b)=1:3~ A method for stabilizing the ground, characterized in that a hardening agent mixed at a ratio of 3:1 (weight ratio) is used in an amount of 0.7 to 3.6 parts by weight per 1 part by weight of sodium silicate. 2. The stabilization method according to claim 1, wherein the lime is slaked lime and/or quicklime.