JP2009046611A - Injection material for ground stabilization - Google Patents

Abstract

The present invention provides an injection material that stably and steadily strengthens unstable ground in tunnel excavation work, etc., and ensures strength that can be excavated within 24 hours after injection.
[Solution]
(A) an aqueous suspension of cement having a brain value of 8000 to 10000 cm ² / g,
(B) an aqueous solution of sodium silicate consisting of SiO ₂ and Na ₂ O and having a SiO ₂ / Na ₂ O (molar ratio) of 2.15 to 2.70, and (C) calcium chloride,
An injecting material for stabilizing a ground, wherein the weight of cement is 225 to 250 kg, the weight of SiO ₂ derived from a sodium silicate component is 100 to 120 kg, and the weight of calcium chloride is 1 to 15 kg per 1000 L of the injecting material.
[Selection figure] None

Description

  The present invention relates to an injection material for stabilizing a ground.

  Conventionally, as a method for improving the stability of unstable ground for tunnel excavation and the like, a method by injecting organic or inorganic grout has been performed. However, these methods do not always give satisfactory results. For example, an organic injection material can be expected to stabilize the ground. However, since polyols and polyisocyanates as raw materials are expensive and flammable, improvements are required in terms of economy and safety. On the other hand, as for the inorganic injection material, for example, cement generally used for suspension type injection material has a large particle size, so that the permeability to the ground is poor and it is difficult to obtain a uniform solidified body. Moreover, in the solution type which has sodium silicate as a main component, there is no problem in permeability, but the solidified body strength is low and the stabilization of the ground is insufficient.

  Therefore, as an injection material that has improved these disadvantages, a method of improving the permeability to the ground by making the suspended particles into ultrafine particles has been proposed (for example, see Patent Documents 1 to 5). However, in these methods, it is necessary to increase the blending amount of cement and sodium silicate in order to obtain a consolidated strength necessary for excavation, and there is room for improvement in terms of economy. In addition, an injection material in which the sand gel strength of the solution type injection material is greatly improved has been proposed (for example, see Patent Document 6). However, elution of the organic compound used in the curing agent may occur. As a method for improving these problems, there has been proposed an injecting material that uses ultrafine cement and has a short cementation time and gives a sufficient solidified strength (for example, see Patent Document 7). . However, there is room for improvement in that a consolidated body having a uniaxial compressive strength of 2.0 MPa or more is economically obtained.

JP 2004-285133 A JP 2001-49256 A Japanese Patent Laid-Open No. 10-245556 JP 7-229137 A JP 2003-63853 A Japanese Patent Laid-Open No. 2002-180046 JP 2006-249336 A

  The present invention compensates for the problems in the prior art described above. In order to strengthen and stabilize the unstable ground in tunnel excavation work economically and at an early stage, the consolidated body having sufficient uniaxial compressive strength is promptly used. An object of the present invention is to provide an injecting material that is applied to the above-mentioned injecting material with a reduced amount of cement.

The present invention
(A) an aqueous suspension of cement having a brain value of 8000 to 10000 cm ² / g,
(B) an aqueous solution of sodium silicate consisting of SiO ₂ and Na ₂ O and having a SiO ₂ / Na ₂ O (molar ratio) of 2.15 to 2.70, and (C) calcium chloride,
Per injection material 1000L, the weight of the cement 225～250Kg, the weight of SiO ₂ derived from sodium silicate component 100～120Kg, relates stabilizing grout of ground weight of calcium chloride is 1～15Kg.

  In the injecting material for stabilization of the ground of the present invention, since the ultrafine particle cement is used, the injecting material penetrates into fine cracks and voids, and a high stabilizing effect is obtained. Moreover, it is possible to make the gelation time of the injection material into a specific range by adding sodium silicate having a specific composition to the ultrafine cement at a specific ratio and further adding calcium chloride at a specific ratio. Therefore, it is possible to easily perform limited injection to a necessary place even in the ground with running water. Moreover, since it has strength development in a short time after injection, it is excellent in workability. Furthermore, since the amount of cement can be reduced in the injection material, it is excellent in economic efficiency.

  Therefore, by using the injecting material of the present invention, it is possible to provide a ground strength and strengthening method which is required for tunnel construction and has high strength and safety and which is economically excellent.

The injection material for stabilizing the ground for tunnel excavation according to the present invention includes a cement water suspension (A), a sodium silicate aqueous solution (B) composed of SiO ₂ and Na ₂ O, and calcium chloride (C). .

  The cement of the aqueous suspension (A) of the cement is not particularly limited, and a conventionally known cement can be used. For example, Portland cement such as ordinary Portland cement, early-strength cement, intermediate heat cement, Type A, B Seeds, class C blast furnace cement, class A, class B, class C fly ash cement, silica cement and the like.

The cement is preferably pulverized by a jet mill or the like and used as an ultrafine cement having a large brane value. Here, the Blaine value means the particle surface area per gram. Blaine value of cement is 8000~10000cm ² / g, preferably from 8500~9500cm ² / g. If the brane value is less than 8000 cm ² / g, the permeability to the ground will decrease, making it difficult to obtain a sufficient stabilizing effect. On the other hand, when the brain value exceeds 10,000 cm ² / g, the fluidity of the aqueous suspension decreases.

  The proportion of the cement and water in the cement water suspension (A) is preferably 100 to 300 parts by weight, more preferably 125 to 250 parts by weight, per 100 parts by weight of cement. If the amount is less than 100 parts by weight, the viscosity of the cement aqueous suspension (A) increases, so that the injection workability tends to decrease. If the amount exceeds 300 parts by weight, the amount of solids in the injection material decreases and solidifies. Body strength tends to decrease.

  In the cement of the cement aqueous suspension (A), additives can be appropriately blended within a range not impairing the effects of the present invention. As such additives, in order to adjust calcium elution, calcium elution amount adjusting agent such as bicarbonate, carbonate, phosphate containing condensed phosphate system, in order to adjust gelation time, Reactants such as esters, aldehydes, amides, alcohols, acids, lime, gypsum, cement, gelation accelerators such as acidic silicic acid aqueous solutions, and pozzolans such as fly ash, sinter, diatomaceous earth, and white clay And so on.

SiO ₂ / Na ₂ O (mole ratio) in aqueous solution of sodium silicate of SiO ₂ and Na ₂ O of sodium silicate solution (B) is from 2.15 to 2.70, preferably 2.15 to 2 .25. When SiO ₂ / Na ₂ O (molar ratio) is less than 2.15, the sodium concentration in the sodium silicate aqueous solution is increased, and the gelation time is delayed. On the other hand, if it exceeds 2.70, the gelation time is accelerated, and since the effect of promoting the hardening reaction of the cement is small due to the low sodium concentration in the aqueous sodium silicate solution, sufficient solidified strength can be obtained. The problem of not.

  The concentration of the sodium silicate aqueous solution (B) is preferably 10 to 40% by weight, and more preferably 15 to 30% by weight. If the concentration of the sodium silicate aqueous solution (B) is less than 10% by weight, a curing reaction with sodium silicate can hardly be expected, and the gelation time tends to be long. If the concentration is higher than 40% by weight, the sodium silicate aqueous solution Since the viscosity of (B) increases, the injection workability tends to decrease.

  In addition, a water-soluble aluminum compound or a water-soluble polyvalent metal compound other than calcium chloride (C) is added to the sodium silicate aqueous solution as long as the effect of the present invention is not impaired as a curing agent in the sodium silicate aqueous solution (B). May be. Examples of the water-soluble aluminum compound include alkali metal aluminates, aluminum sulfate, alums, aluminum chloride, and aluminum nitrate. Moreover, magnesium chloride, iron chloride, etc. can be added as water-soluble polyvalent metal compounds other than calcium chloride (C).

  When these curing agents are blended in the sodium silicate aqueous solution (B), the concentration of the curing agent in the sodium silicate aqueous solution (B) is preferably 1 to 10% by weight, more preferably 1 to 5% by weight. . If the concentration of the curing agent is less than 1% by weight, the effect of adjusting the curing of the aqueous sodium silicate solution by the curing agent tends to be difficult to obtain. If the concentration exceeds 10% by weight, the liquid stability of the aqueous sodium silicate solution by the curing agent Tends to be reduced, and gelation tends to occur before mixing with the aqueous cement suspension (A).

Calcium chloride (C) is known as a curing agent for sodium silicate, and by adding an appropriate amount of calcium chloride (C), chloride ions and calcium ions are dissolved in the sodium silicate aqueous solution (B). Sodium ions are extracted from the SiO ₂ / Na ₂ O component, and the liquid stability of the sodium silicate aqueous solution (B) decreases, thereby promoting the hardening of the mixture of the injection material and at the same time calcium ions are suspended in the cement water. The effect of promoting the cement hydration reaction in the liquid (A) is also obtained.

  Calcium chloride (C) is not particularly limited, and general-purpose calcium chloride can be used. Examples thereof include granular calcium chloride sprayed for preventing freezing of road surfaces in cold regions.

  Although it does not specifically limit as a compounding method of calcium chloride (C), For example, the method of mix | blending as calcium chloride aqueous solution can be used. In addition, from the viewpoint of injection workability and gelation time stability, when preparing a cement suspension (A), a predetermined amount of calcium chloride (C) is blended together with the cement and mixed and dissolved before use. Is preferred. Then, it is preferable to mix what was mixed and dissolved as (A) liquid, and to mix sodium silicate aqueous solution (B) as (B) liquid.

  When the cement water suspension (A), the sodium silicate aqueous solution (B), and the calcium chloride (C) are mixed to obtain the injection material of the present invention, the weight of the cement per 1000 L of the injection material is 225 to 250 kg. Yes, preferably 230-250 kg. When the amount of cement is less than 225 kg, the solid content in the injection material is reduced, so that a sufficient solidified strength cannot be obtained. Moreover, when 250 kg is exceeded, the viscosity of an injection agent will become high and injection workability will fall.

When mixing an aqueous suspension of cement (A), a sodium silicate aqueous solution (B), and calcium chloride (C) to obtain an injection material of the present invention, SiO ₂ derived from sodium silicate components per 1000 L of the injection material The weight of is from 100 to 120 kg, preferably from 105 to 115 kg. Is less than the weight of SiO ₂ is 100 kg, since the gelling performance of sodium silicate decreases gel time is delayed. Moreover, when 120 kg is exceeded, the viscosity of sodium silicate aqueous solution will become high, and injection | pouring workability | operativity will fall.

  When mixing an aqueous suspension of cement (A), an aqueous sodium silicate solution (B), and calcium chloride (C) to obtain the injection material of the present invention, the weight of calcium chloride (C) per 1000 L of the injection material is: 1 to 15 kg, preferably 5 to 15 kg. If the weight of calcium chloride (C) is less than 1 kg, the gelation effect of the sodium silicate aqueous solution (B) by calcium chloride (C) is difficult to obtain, and the gelation time is delayed. On the other hand, if the amount exceeds 15 kg, the gelation time becomes too early, and the injection workability tends to be lowered.

  By taking the above configuration, the gelation time of the injection material obtained by mixing the cement aqueous suspension (A), the sodium silicate aqueous solution (B) and the calcium chloride (C) is 30 seconds to 1 minute 30. Can be seconds. When injecting the injection material into fine cracks or voids in the ground, if the gelation time is less than 30 seconds, the injection material gels before infiltrating the fine cracks or voids, and a sufficient stabilizing effect is obtained. If it is longer than 1 minute and 30 seconds, the injected material tends to flow out in the presence of running water, and limited injection tends to be difficult. However, the present invention can solve such a problem. The gelation time was determined by previously mixing the liquids (A) and (B) previously adjusted to 20 ° C. with stirring for 20 seconds, and then using two polycups to move the injecting material. Time until sex disappears. The gelation time can have an error of about ± 5 seconds for both the upper limit value and the lower limit value.

  Uniaxial compressive strength of an injection material obtained by mixing an aqueous suspension of cement (A), an aqueous solution of sodium silicate (B) and calcium chloride (C) (“Uniaxial compression test method of soil” in JIS A 1216 (1998) In order to ensure sufficient safety, workability, and excavation work the next day, the uniaxial compressive strength after 24 hours is 2.0 MPa or more, preferably 2.3 MPa. That's it. The uniaxial compressive strength after 24 hours is not particularly limited, but is usually about 4.0 MPa. The uniaxial compressive strength can allow an error of about ± 0.2 MPa for both the upper limit value and the lower limit value.

  The injection material of the present invention is a special injection material, for example, an injection-type fore-polling method or an injection-type long tip receiving method that is performed for the purpose of preventing collapse of the top of the face and prevention of expansion of looseness during tunnel excavation. In (AGF method), it is injected and consolidated into soft or unstable ground, rock mass or crush zone with many voids and cracks. In the present invention, the ground is a general term for the earth and sand around the tunnel and includes rocks, cracks, etc., the rock is the ground mainly composed of rock, and the crush zone is weathered and deposited of earth and sand. This is a collapsible stratum that is likely to collapse due to tunnel excavation.

  As the ground stability strengthening method using the injection material of the present invention, a known method can be adopted. For example, a step of drilling a plurality of holes in the ground at a predetermined interval, a hollow bolt in the hole Preferably, a method including the step (a) of inserting the material and the step (b) of injecting and solidifying the ground stabilization injection material of the present invention into the ground through the opening of the bolt is preferably used.

  When injecting the injection material into the ground, for example, calcium chloride (C) is previously blended into the cement water suspension (A), and then, for example, the cement water suspension (A) and sodium silicate are mixed. A comparative compounding pump that can control the injection amount, pressure, and compounding ratio of the aqueous solution (B) is used. In this case, the cement aqueous suspension (A) and the sodium silicate aqueous solution (B) are put in separate tanks, and a plurality of holes provided at predetermined locations such as the ground (for example, at intervals of about 0.5 to 3 m). Through the perforated rock bolt or injection rod with a static mixer or check valve fixed in advance, and the components in the tank are injected at an injection pressure of 0.05 to 5 MPa. Through a static mixer, a predetermined amount of cement water suspension (A) and sodium silicate aqueous solution (B) are uniformly mixed, injected into a predetermined unstable ground, and hardened to be consolidated and stabilized.

  For example, when injecting into the top of the tunnel, drilling is performed with a leg auger of, for example, 42 mmφ bit at an interval of, for example, about 2 m, and the depth is 2 m and the drilling angle is 10-30. A hollow carbon steel pipe lock bolt with a 3 m hole with a static mixer and a check valve is inserted into the injection hole, and the mouth of the lock bolt is inserted into the injection material. In order to prevent backflow, it is preferable to seal with a waste cloth and foamed hard urethane resin, and to inject the chemical solution by the above method. The injection operation is terminated when the injection pressure suddenly increases or when the injection pressure is further increased by about 50% from the predetermined injection amount. Generally, it is preferable to inject 50 to 500 kg of the injection material per injection hole.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

  As cement, cement 1 having a brane value as shown in Table 1 (trade name: Denka Colloidal Super, manufactured by Denki Kagaku Kogyo Co., Ltd.), cement 2 (product name: ordinary Portland cement, Taiheiyo Cement Co., Ltd.), Cement 3 (trade name: Fine Hard, manufactured by Mitsubishi Materials Corporation) was used.

  Moreover, as sodium silicate, the sodium silicate 1-4 which has a composition as shown in Table 2 (all are the Fuji Chemical Co., Ltd. product) was used.

  Further, calcium chloride dihydrate was used as calcium chloride.

Examples 1-6 and Comparative Examples 1-6
According to Table 3, the weight of cement per 1000 L of the injection material, the weight of SiO ₂ derived from the sodium silicate component, and the weight of calcium chloride were changed, and the aqueous suspension of the cement previously mixed with calcium chloride (A) (A) liquid, sodium silicate aqueous solution (B) as (B) liquid, (A) liquid and (B) liquid were mixed to obtain an injection material.

  The gelation time of the obtained injection material and the consolidated strength after 24 hours were measured by the following method. The results are shown in Table 3.

(A) Gelation time The liquid (A) and the liquid (B), which were adjusted to 20 ° C. in advance, were mixed well by stirring for 20 seconds with a spatula, and then the injection material was moved using two polycups. The time until disappearance was measured.

(B) Consolidation strength The casting material was poured into a 5φ × 10 cm mold, hermetically cured at 20 ° C. for 24 hours, and measured according to “Soil uniaxial compression test method” in JIS A 1216 (1998).

According to Table 3, it can be seen that the ground stabilization injecting material of the present invention gels in a short time by adding calcium chloride, and has a very strong solidified body strength after 24 hours. In Examples 1 and 3, the consolidated strength is particularly excellent. It can be seen that the injection materials in Examples 2, 4, 5 and 6 have excellent consolidated strength even with a reduced amount of cement. On the other hand, the injection material in Comparative Example 1 has a small cement brane value, so that it can be seen that sufficient consolidated strength cannot be obtained. It can also be seen that the injection materials of Comparative Examples 2 to 6 do not satisfy the composition of the present invention, so that a sufficient consolidated strength cannot be obtained. In Comparative Example 4 where the SiO ₂ / Na ₂ O (molar ratio) in the liquid (B) is low, the gelation time of the injection material is remarkably slow, which makes it difficult to inject the injection material in the presence of running water. In Comparative Examples 2 and 4, since calcium chloride is not blended, the gelation time is further delayed. Furthermore, in Comparative Example 5, since the amount of calcium chloride is small, not only a sufficient consolidated strength can be obtained, but also the gelation time is delayed. In Comparative Example 6, the amount of calcium chloride is large. In addition to not being able to obtain a sufficient solidified strength, the gelation time is no longer required, and no appropriate gelation time is obtained in any of the comparative examples.

Claims (1)

(A) an aqueous suspension of cement having a brain value of 8000 to 10000 cm ² / g,
(B) an aqueous solution of sodium silicate consisting of SiO ₂ and Na ₂ O and having a SiO ₂ / Na ₂ O (molar ratio) of 2.15 to 2.70, and (C) calcium chloride,
An injecting material for stabilizing a ground, wherein the weight of cement is 225 to 250 kg, the weight of SiO ₂ derived from a sodium silicate component is 100 to 120 kg, and the weight of calcium chloride is 1 to 15 kg per 1000 L of the injecting material.