Frost-inhibiting roadbed material and frost-inhibiting roadbed formation method

Abstract

To provide a road-bed material capable of more surely controlling generation of frost heave.SOLUTION: This frost heave control road-bed material contains water granulated slag with a 0.15 mm sieve passage rate of 3.8% or less, silicon dioxide, aluminum oxide, calcium oxide, and magnesium oxide, and when solidified by spreading and sprinkling water, the freezing expansion rate is suppressed to 0.5% or less. Here, it is also preferable that the water granulated slag have a coarse particle ratio of 3.1 or more, and that the water granulated slag have a fine particle content of 2.9% or less. Furthermore, as a preferred embodiment, the water granulated slag has a 0.15 mm sieve passage rate of 3.0% or less, and the freeze expansion rate is preferably suppressed to less than 0.3% when it is spread and sprinkled with water to solidify. In this preferred embodiment, it is also preferable that the water granulated slag has a coarse particle ratio of 3.2 or more, and that the water granulated slag has a fine particle content of 2.3% or less.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a technique for forming roadbeds such as those for railways and roads, and for producing roadbed materials used for forming roadbeds.

Background Art

[0002] Roadbeds for railways and roads are important structures for realizing safe and comfortable transportation and movement. In fact, construction work is being carried out nationwide to newly construct various roadbeds using roadbed materials or to perform maintenance and improvement of existing roadbeds.

[0003] For example, specifically, maintenance and improvement work on railway roadbeds includes measures against mud gushing from the roadbed, measures against settlement of rail joints, measures against settlement of embankments at connection parts of structures such as behind bridge abutments, measures against settlement due to backfilling of buried objects under the track such as cross pipelines, and further measures against settlement of the roadbed and measures for strengthening the roadbed under the crossing board, etc., and are widely carried out for these purposes.

[0004] As a suitable roadbed material used for such maintenance, improvement, and new construction of roadbeds, Patent Document 1 (Patent No. 3826899) related to a patent in which the applicant of the present application is the patentee discloses a high-void roadbed material mainly composed of granulated slag, having little sulfur content, high water permeability, and capable of spreading or replacing a high-strength roadbed simply and in a short time even in relatively difficult working locations. In fact, this high-void roadbed material is a roadbed material with high long-term strength corresponding to the design standards for railway structures, etc. (see Non-Patent Document 1) revised in 2000 (Heisei 12).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] When forming a roadbed using such roadbed materials, usually, the roadbed materials are spread evenly to a predetermined height, and then water is sprayed thereon to solidify the roadbed materials. Here, in winter, especially in winter in cold regions, the freezing of moisture inside the formed ground causes expansion and uplift, that is, the occurrence of the so-called frost heaving phenomenon is a major problem.

[0008] Actually, due to the occurrence of the frost heaving phenomenon, the upper surface of the roadbed may become higher than the design value, or may become uneven or wavy. Furthermore, the position of the structure on the roadbed may deviate from the design. In extreme cases, there is also concern that it may affect the operation and running of railway vehicles and automobiles. However, conventionally, it has been recognized that there is a considerable variation in the degree of the occurring frost heaving phenomenon. For example, even when improving the roadbed materials, no measures have been found to reliably suppress the occurring freezing expansion without significant variation.

[0009] Therefore, an object of the present invention is to provide a roadbed material and a roadbed formation method capable of more reliably suppressing the occurrence of frost heaving.

Means for Solving the Problems

[0010] According to the present invention, there is provided a frost heaving suppression roadbed material containing crushed slag with a sieve passing rate of 0.15 millimeters (mm) of 3.8 percent (%) or less, and silicon dioxide, aluminum oxide, calcium oxide, and magnesium oxide, and having a freezing expansion rate suppressed to 0.5% or less when spread evenly, sprayed with water, and solidified.

[0011] In the frost heave suppression roadbed material according to the present invention, it is also preferable that the coarse grain ratio of the above-mentioned granulated slag is 3.1 or more. Further, it is also preferable that the content rate of the fine fraction of the above-mentioned granulated slag is 2.9% or less.

[0012] Furthermore, as a preferred embodiment of the frost heave suppression roadbed material according to the present invention, the above-mentioned granulated slag has a passing rate through a 0.15 mm sieve of 3.0% or less, and it is also preferable that the frost heave rate when spreading and watering and solidifying is suppressed to less than 0.3%.

[0013] Also in this preferred embodiment, it is also preferable that the coarse grain ratio of the above-mentioned granulated slag is 3.2 or more. Further, it is also preferable that the content rate of the fine fraction of the above-mentioned granulated slag is 2.3% or less.

[0014] Furthermore, in this preferred embodiment, when frozen after spreading and watering and solidifying, the frost heave rate at the time of normalization, where the temperature of the lower end surface on the ground side is 10 degrees (°C) lower than the temperature of the upper end surface on the outside air side, is suppressed to less than 0.1%. Also, the above-mentioned watering after spreading is preferably such that the water content ratio of the frost heave suppression roadbed material is in the range of 9.7% or more and 16.1% or less.

[0015] Furthermore, the frost heave suppression roadbed material according to the present invention further contains cement, the above-mentioned cement is contained only in an amount of 4.0% by weight or more and 36% by weight or less as a weight ratio to the granulated slag, it is also preferable that the above-mentioned silicon dioxide, aluminum oxide, calcium oxide, and magnesium oxide are each contained only in an amount of 0.10% by weight or more and 1.0% by weight or less, 0.05% by weight or more and 0.50% by weight or less, 0.08% by weight or more and 0.80% by weight or less, and 0.01% by weight or more and 0.12% by weight or less as a weight ratio to the granulated slag.

[0016] According to the present invention, also, for granulated slag with a sieve passing rate of 0.15 mm of 3.8% or less, cement is added and mixed in an amount of 4.0% by weight or more and 36% by weight or less, and further, silicon dioxide, aluminum oxide, calcium oxide, and magnesium oxide are each added and mixed in an amount of 0.10% by weight or more and 1.0% by weight or less, 0.05% by weight or more and 0.50% by weight or less, 0.08% by weight or more and 0.80% by weight or less, and 0.01% by weight or more and 0.12% by weight or less, respectively, to produce a subgrade material. The first step is The subgrade material is spread evenly to a predetermined height, and the spread subgrade material is watered to solidify the subgrade material, and a second step of forming a subgrade with the frost heaving suppressed to a frost heave rate of 0.5% or less A method for forming a frost heave suppressing subgrade is provided.

[0017] As a preferred embodiment of the method for forming a frost heave suppressing subgrade according to the present invention, in the above first step, granulated slag with a sieve passing rate of 0.15 mm of 3.0% or less is used, and in the above second step, it is also preferable to form a subgrade with the frost heaving suppressed to a frost heave rate of less than 0.3%.

Effects of the Invention

[0018] According to the subgrade material and the subgrade forming method of the present invention, it is possible to more reliably suppress the occurrence of frost heaving.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.

[0021] [Freezing Expansion Rate of Frost Heave Suppression Roadbed Material, etc.] The roadbed material according to the present invention (hereinafter also referred to as the frost heave suppression roadbed material) is a material for forming roadbeds for railways, roads, etc., and is a roadbed material that is very suitable for maintaining, improving, or newly constructing roadbeds in winter, especially in cold regions such as Hokkaido.

[0022] Conventionally, at the site of roadbed formation work in such cold regions in winter, the so-called frost heave phenomenon, in which expansion and uplift occur due to the freezing of moisture inside the formed ground, has been a major problem. In fact, when converted from the displacement and deformation of the roadbed surface and the displacement of the superstructure on the roadbed, cases where frost heave occurs with a freezing expansion rate ξ exceeding 1% have also been confirmed.

[0023] Also, even when using the same roadbed material, the degree of frost heave varied greatly depending on the site. One cause of this variation is thought to be that the amount of watering during roadbed formation work differed somewhat depending on the site conditions, and the water content ratio W of the roadbed material was not constant.

[0024] Here, based on the empirical knowledge at the construction site, considering the allowable range of displacement and deformation on the roadbed surface and the allowable range of displacement at the position of the structure on the roadbed, it has been found that it is important to ensure that the freezing expansion rate ξ is exactly 0.5% or less without variation, and more preferably (to more surely eliminate the adverse effects of freezing) less than 0.3%.

[0025] Under such circumstances, specifically, this anti-freezing roadbed material (A) crushed slag with a sieve passing rate P_0.15 of 0.15 millimeters (mm) being 3.8% or less, and (B) silicon dioxide (SiO2), aluminum oxide (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO), and contains (C) the freezing expansion rate ξ when leveled and watered and solidified is suppressed to 0.5% or less and is characterized by this. Incidentally, when forming a roadbed using this anti-freezing roadbed material, as will be described later, this anti-freezing roadbed material is leveled to a predetermined height, and then water is sprinkled thereon to solidify the anti-freezing roadbed material.

[0026] Here, the sieve passing rate P_0.15 of 0.15 mm in the above (A) can be the result of a sieving test carried out in accordance with JIS (Japanese Industrial Standard) A1102 "Sieving Test Method for Aggregates". Also, the freezing expansion rate ξ in the above (C), although it will be described in detail as an example later, can be the result of a freezing property test carried out in accordance with JGS 0172 - 2020 "Test Method for Soil Freezing Property for Freezing Property Judgment", which is a standard of the Public Interest Corporation Ground Engineering Society.

[0027] Thus, according to the anti-freezing roadbed material of the present invention, as will be described later with reference to FIGS. 1 and 2, by suppressing the "sieve passing rate P_0.15 of 0.15 mm" of the crushed slag to 3.8% or less, the proportion of fine particles that promote freezing is reduced, and the occurrence of the freezing phenomenon can be more surely suppressed. Specifically, the freezing expansion rate ξ can be suppressed to 0.5% or less.

[0028] In addition, in the frost heaving suppression roadbed material of the present invention, the coarse grain ratio G of granulated slag may be 3.1 or more. That is, as will be described in detail later, it is also possible to define the characteristics of the granulated slag according to the present invention by the coarse grain ratio G. Here, this coarse grain ratio G can be the result of a sieving test conducted in accordance with JIS (Japanese Industrial Standards) A1102 "Sieving Test Method for Aggregates".

[0029] Furthermore, in the frost heaving suppression roadbed material of the present invention, the fine particle content rate F of granulated slag is preferably 2.9% or less. That is, as will be described in detail later, it is also possible to define the characteristics of the granulated slag according to the present invention by the fine particle content rate F. Incidentally, the fine particle content rate F is a characteristic that can be measured based on JIS (Japanese Industrial Standards) A1223:2020. However, generally, the value of the fine particle content rate F in granulated slag is small, and it is difficult to derive a highly accurate absolute value, and its measurement method is also very labor-intensive and costly.

[0030] As yet another more preferable embodiment, as will be described in detail later, (A’) granulated slag with a passing rate P_0.15 of 0.15 mm sieve of 3.0% or less, and (B) silicon dioxide (SiO2), aluminum oxide (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO), and including (C’) having a freezing expansion rate ξ of less than 0.3% when leveled and watered and solidified. is also preferable. Here, in this embodiment, the coarse grain ratio G of granulated slag is preferably 3.2 or more, and the fine particle content rate F of granulated slag is preferably 2.3% or less.

[0031] In this way, by further reducing the proportion of fine particles that promote frost heaving of the roadbed, it is possible to more reliably suppress the occurrence of frost heaving. Specifically, the freezing expansion rate ξ can be suppressed to less than 0.3%.

[0032] Incidentally, as a preferred embodiment of the composition, the present frost heave suppressing roadbed material that exhibits the high frost heave suppressing performance as described above further contains cement, (D) The cement is contained in an amount of 4.0 to 36% by weight based on the weight of the granulated slag, (E) Silicon dioxide (SiO2), aluminum oxide (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO) are each contained in an amount of 0.10 to 1.0% by weight, 0.05 to 0.50% by weight, 0.08 to 0.80% by weight, and 0.01 to 0.12% by weight, respectively, based on the weight of the granulated slag is also preferable. Note that "x to y% by weight" represents "not less than x% by weight and not more than y% by weight".

[0033] Here, in the above configuration (D), if the cement content is less than 4% by weight, the solidification strength is insufficient. On the other hand, if it exceeds 36% by weight, the voids decrease, the water permeability decreases, and the cost increases. Also, in the above configuration (E), if the silicon dioxide (SiO2) content is less than 0.10% by weight, the rapid growth of calcium silicate cannot be expected. On the other hand, if it exceeds 1.0% by weight, the voids decrease, the water permeability decreases, and the cost increases.

[0034] Furthermore, in the above configuration (E), if the aluminum oxide (Al2O3) content is less than 0.05% by weight, the flash setting property cannot be exhibited. Also, even if it exceeds 0.50% by weight, the flash setting performance deteriorates and the cost increases. Further, if the calcium oxide (CaO) content is less than 0.08% by weight, the strength decreases. On the other hand, even if it exceeds 0.8% by weight, a higher strength cannot be obtained and the cost increases. Furthermore, if the magnesium oxide (MgO) content is less than 0.01% by weight, the quick hardening property cannot be obtained. On the other hand, even if it exceeds 0.12% by weight, a higher quick hardening property cannot be obtained and the cost increases.

[0035] Incidentally, the meaning of the composition ranges of the above configurations (D) and (E) as described above was discovered by experiments conducted by the inventors of the present application. It has been confirmed by experiments that the anti-freezing roadbed material that satisfies the above configurations (D) and (E) becomes an excellent roadbed material that combines high water permeability (high porosity) and high anti-freezing performance.

[0036] Incidentally, as a typical example, the water permeability coefficient of this anti-freezing roadbed material is 5.3×10 -2 cm / sec during construction. Thus, according to this anti-freezing roadbed material, by exhibiting a high water permeability comparable to that of sand and gravel, the penetration of water into the roadbed material can be promoted, and the manifestation of the supporting force can be accelerated. Incidentally, it has also been confirmed that the water permeability coefficient is reduced to 6.2×10 -3 cm / sec as a typical example six months after construction.

[0037] Moreover, for the anti-freezing roadbed material test piece with the following composition (mixing ratio) that satisfies the conditions of the above configurations (D) and (E): · Dry crushed slag (P_0.15 = 3.0%) 1240.0 kg / m 3 · Portland cement 150.0 kg / m 3 (12.1 wt%) · Silicon dioxide (SiO2) 4.4 kg / m 3 (0.35 wt%) · Aluminum oxide (Al2O3) 1.7 kg / m 3 (0.14 wt%) · Calcium oxide (CaO) 3.2 kg / m 3 (0.26 wt%) · Magnesium oxide (MgO) 0.7 kg / m 3 (0.06 wt%) (· Water 180 liters) In this case, when the uniaxial compressive strength σ 14 , the long-term uniaxial compressive strength σ 180 , and the deformation coefficient E 50 were measured, they were 1.2 MN / m 2 or more, 2.0 MN / m 2 or more, and 300 MN / m 2That is, it has been confirmed that the present frost heave suppressing roadbed material having the above configurations (D) and (E) achieves the strength and deformation coefficient in accordance with "Railway Structures Design Standards and Commentary - Earth Structures (SI Unit Edition)" (issued in 2000 (Heisei 12), Railway Technical Research Institute, Incorporated Administrative Agency).

[0038] In addition, as the present frost heave suppressing roadbed material that exhibits the high frost heave suppressing performance as described above, in addition to cement, it further contains fly ash. (D’) Cement and fly ash are each contained in an amount of 2.0 to 18% by weight and 2.0 to 18% by weight, respectively, based on the weight ratio to granulated blast furnace slag. (E’) Silicon dioxide (SiO2), aluminum oxide (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO) are each contained in an amount of 0.05 to 1.0% by weight, 0.02 to 0.50% by weight, 0.04 to 0.80% by weight, and 0.01 to 0.12% by weight, respectively, based on the weight ratio to granulated blast furnace slag. This is also preferable.

[0039] Here, regarding the frost heave suppressing roadbed material having the above configurations (D’) and (E’), it has been confirmed by experiments that it achieves the strength and deformation coefficient in accordance with "Railway Structures Design Standards and Commentary - Earth Structures (SI Unit Edition)" (issued in 2000 (Heisei 12), Railway Technical Research Institute, Incorporated Administrative Agency), and also exhibits high water permeability (high porosity).

[0040] Furthermore, as the present frost heave suppressing roadbed material that exhibits the high frost heave suppressing performance as described above, it is also possible to adopt one that contains neither cement nor fly ash. Specifically, (D’’) It contains neither cement nor fly ash. (E’’) Silicon dioxide (SiO2), aluminum oxide (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO) are each contained in an amount of 1.5 to 13% by weight, 0.50 to 4.5% by weight, 1.0 to 8.0% by weight, and 0.15 to 1.5% by weight, respectively, based on the weight ratio to granulated blast furnace slag. This is also preferable.

[0041] Here, even for the frost heave suppression roadbed material provided with the above-described configurations (D'') and (E''), it has been experimentally confirmed that the strength and deformation coefficient compliant with the "SI Unit Edition - Design Standards and Commentary for Railway Structures, etc. - Earth Structures" (published in 2000 (2000 in the Heisei era), Railway Technical Research Institute, Incorporated Administrative Agency) are achieved, and also it exhibits high water permeability (high void ratio).

[0042] Hereinafter, the characteristics of each component in the present frost heave suppression roadbed material described above will be explained.

[0043] First, granulated slag can be made into hydraulic granulated blast furnace slag obtained by subjecting blast furnace slag aggregate to an aging treatment that oxidizes sulfur in the slag with water and air to chemically stabilize it. Such blast furnace (granulated) slag has both long-term hydraulicity and potential hydraulicity in which the supporting force can increase over time.

[0044] Also, as the cement, mainly Portland cement, blast furnace cement, early-strength Portland cement, etc. can be adopted, and other special cements may be used as necessary.

[0045] Fly ash can be mainly composed of pulverized coal burned in a pulverized coal burner, and can be mixed with clinker ash as necessary. Such fly ash has water solubility, and it is expected to maintain and increase strength over a long period with appropriate addition of water.

[0046] The present frost heave suppression roadbed material obtained by mixing such cement (or fly ash) at the above mixing ratio causes the potential hydraulicity of granulated slag to be expressed in a very good state. Here, this potential hydraulicity is strongly exerted, for example, by forming a strong alkaline atmosphere in the roadbed by blending an appropriate amount of calcium oxide (CaO) as described above.

[0047] In addition, granulated blast furnace slag is basically obtained by rapidly cooling blast furnace slag with a large amount of water or air, and thus exhibits a glassy granular form. In this glassy granular structure, the state at high temperature where molecules were moving around is directly quenched and brought to room temperature, so it is in a very unstable state and rich in chemical reactivity. Granulated blast furnace slag can, therefore, be hardened by adding water in the presence of alkaline substances.

[0048] More specifically, the hardening of granulated blast furnace slag is achieved by cutting the tetrahedral network of silicon tetraoxide (SiO4) that forms the glassy granular structure. Once this network is cut, alkaline substances such as calcium oxide (CaO) and magnesium oxide (MgO) elute from the granulated blast furnace slag, and the atmosphere is kept alkaline. As a result, the cutting of this network is maintained and promoted, the dissolution of the glassy material into water progresses, and a hardening phenomenon similar to that of cement occurs due to the eluted calcium oxide (CaO), silicon dioxide (SiO2), aluminum oxide (Al2O3), etc.

[0049] [Relationship between fine particle content and freeze expansion rate] Figure 1 is a graph showing the relationship between the fine particle content F and the freeze expansion rate ξ in soil containing fine particles.

[0050] Figure 1 shows the results of measuring the freeze expansion rate ξ for a number of soils containing fine particles with various values of the fine particle content F. Here, the soil containing fine particles is a material whose characteristics related to its particle size are relatively easy to adjust and is often used to estimate the characteristics related to the particle size in roadbed materials containing granulated blast furnace slag. In addition, the fine particle content F was measured based on JIS A1223:2020, while the freeze expansion rate ξ was measured by conducting a frost susceptibility test in accordance with JGS 0172 - 2020.

[0051] As shown in Fig. 1, the freezing expansion ratio ξ and the variation in its value tend to decrease as the fine particle content F decreases. This result explains the tendency for the degree of frost heaving to vary significantly depending on the site even when using the same roadbed material. It also suggests that by further suppressing the fine particle content F of the granulated slag contained in the roadbed material, it is possible to suppress frost heaving including its variation.

[0052] Here, the maximum value of the freezing expansion ratio ξ (hereinafter abbreviated as the upper limit freezing expansion ratio ξ U in the samples with each fine particle content F) is obtained by performing fitting processing of an approximate curve on the measurement results in Fig. 1, and the following equation (1) ξ U =0.10×F 1.5 is found to be calculated.

[0053] Note that the value of the upper limit freezing expansion ratio ξ U by the above equation (1) generally agrees with the measurement results (Examples) of the freezing expansion ratio ξ in the frost heaving suppression roadbed material according to the present invention, which will be described in detail later with reference to Figs. 4 to 7. Specifically, in this example, as will be described in detail later, the freezing expansion ratio ξ at the end of freezing in this frost heaving suppression roadbed material with a fine particle content F of 2.3% has been obtained in the range of 0.04 to 0.22%, although slightly varying. On the other hand, according to the above equation (1), the upper limit freezing expansion ratio ξ U is about 0.3 (=0.10×2.3 1.5 ), which generally agrees with the results of the above example.

[0054] According to the above equation (1), it is understood that in order to achieve the above-mentioned goal of "reliably suppressing the freezing expansion ratio ξ to 0.5% or less without variation", it is necessary to suppress the fine particle content F to 2.9% or less.

[0055] However, as described above, generally, the content ratio F of fine particles in granulated slag is small, and it is difficult to derive an accurate absolute value. Moreover, its measurement method is also very labor-intensive and costly. Therefore, hereinafter, the relationship between this content ratio F of fine particles and the passing rate P_0.15 through a 0.15 mm sieve, which can be measured with relatively high accuracy, will be obtained, and it will be explained that the freezing expansion rate ξ can be reliably suppressed by defining and controlling the passing rate P_0.15 through a 0.15 mm sieve.

[0056] [Relationship between content ratio of fine particles and passing rate through 0.15 mm sieve] Figure 2 is a graph for explaining the relationship between the content ratio F of fine particles and the passing rate P_0.15 through a 0.15 mm sieve in granulated slag.

[0057] Specifically, here, based on the results of the sieving test conducted in accordance with JIS A1102 on the roadbed material containing granulated slag, the passing rate through a sieve with an aperture of 0.075 mm was estimated, and this value was regarded as corresponding to the content ratio F of fine particles, and the relationship between the content ratio F of fine particles and the passing rate P_0.15 through a 0.15 mm sieve was determined.

[0058] Incidentally, as a basis for regarding the passing rate through a sieve with an aperture of 0.075 mm as corresponding to the content ratio F of fine particles, for example, the measurement method of the content ratio of fine particles described in Japanese Patent Application Laid-Open No. 2012-220229 can be cited. This patent document discloses a measurement method using the measurement formula: Fc(%) = (Ms - Mss) / Ms × 100 (where Ms is the soil particle mass of the generated soil, and Mss is the soil particle mass of the coarse-grained soil obtained from the generated soil) as a method for easily measuring the content ratio Fc of fine particles in the generated soil at the site. In view of this proposed measurement method, it is understood that the content ratio of fine particles (defined as the particle fraction with a particle size less than 0.075 mm) can be generally grasped as the mass ratio of the particle fraction passing through a 0.075 mm sieve, that is, the passing rate through a 0.075 mm sieve.

[0059] Figure 2(A) shows the relationship between the sieve aperture and the sieve passing rate P in three types of granulated slag with different sieve passing rates. Here, the sieve passing rates of 0.15 mm, 0.3 mm, and 0.6 mm in each granulated slag are the results of a sieving test conducted in accordance with JIS A1102. Also, the vertical axis of the graph in Figure 2(A) is a logarithmic axis.

[0060] According to the graph in Figure 2(A), in each granulated slag, the logarithm of the sieve passing rate P is a linear function of the sieve aperture. Therefore, from each approximate straight line (y = 3.90e 4.10x , y = 1.59e 4.64x , y = 0.41e 6.36x ), the sieve passing rates (5.3%, 2.3%, 0.66%) of the sieve with an aperture of 0.075 mm in each granulated slag are determined. Hereinafter, the sieve passing rate of the determined sieve with an aperture of 0.075 mm will be regarded as the fine particle content rate F and explained.

[0061] Figure 2(B) shows the relationship between the fine particle content rate F determined as described above and the 0.15 mm sieve passing rate P_0.15 in these granulated slags. According to the graph in Figure 2(B), in the granulated slag, the 0.15 mm sieve passing rate P_0.15 is proportional to the fine particle content rate F (with the approximate formula: y = 1.32x). Therefore, it is understood that the fine particle content rate F of the granulated slag can be read in place of the 0.15 mm sieve passing rate P_0.15. For example, the 0.15 mm sieve passing rate P_0.15 in the granulated slag with the above-mentioned fine particle content rate F of 2.9% can be set to 3.8 (= 1.32 × 2.9)%.

[0062] Thus, in order to achieve the above-mentioned goal of "reliably suppressing the freeze expansion rate ξ to 0.5% or less without variation", it is concluded that instead of suppressing the fine particle content rate F to 2.9% or less, the 0.15 mm sieve passing rate P_0.15 may be set to 3.8% or less.

[0063] Incidentally, in known roadbed materials used at sites where frost heaving phenomena with a frost expansion rate ξ exceeding 1% have been confirmed, the 0.15 mm sieve passing rate P_0.15 exceeds 5%, for example, it was 7.0%. In this case, the fine particle content rate F is about 5.3 (= 7 / 1.32)%, and the upper limit frost expansion rate ξu shown in Fig. 1 is about 1.2%. The frost expansion rate ξ does not necessarily become the target 0.5% or less, and shows a variation exceeding 1%. This result generally agrees with the fact that cases where frost heaving phenomena with a frost expansion rate ξ exceeding 1% have been confirmed.

[0064] [Relationship between 0.15 mm sieve passing rate and coarse particle rate] Fig. 3 is a graph showing the relationship between the 0.15 mm sieve passing rate P_0.15 and the coarse particle rate G in granulated slag.

[0065] Fig. 3 shows the relationship between the 0.15 mm sieve passing rate P_0.15 and the coarse particle rate G in three types of granulated slag showing different 0.15 mm sieve passing rates P_0.15. Here, the 0.15 mm sieve passing rate P_0.15 and the coarse particle rate G in each granulated slag are the results of a sieving test carried out in accordance with JIS A1102.

[0066] According to the graph of Fig. 3, in these granulated slags, the coarse particle rate G behaves as a monotonically decreasing function of the 0.15 mm sieve passing rate P_0.15, and is a value calculated from the 0.15 mm sieve passing rate P_0.15 using the approximate curve (y = -0.014x 2 - 0.045x + 3.46) shown in the figure. That is, it is understood that the (fine particle content rate F and) 0.15 mm sieve passing rate P_0.15 of granulated slag can be read in terms of the coarse particle rate G. For example, the coarse particle rate G in the granulated slag with a 0.15 mm sieve passing rate P_0.15 of 3.8% described above can be 3.1 (= -0.014 × 3.8 2 - 0.045 × 3.8 + 3.46).

[0067] Therefore, in order to achieve the above-mentioned goal of "reliably suppressing the freezing expansion rate ξ to 0.5% or less without variation", instead of suppressing the 0.15 mm sieve passing rate P_0.15 to 3.8% or less (the fine particle content rate F to 2.9% or less), it is concluded that the coarse particle rate G should be 3.1 or more.

[0068] [Example: Frost heaving test results] Figures 4, 5, and 6 are graphs for explaining examples in which the freezing expansion rate ξ was measured in the frost heaving suppression roadbed material according to the present invention. Here, the graphs of Figures 4, 5, and 6 are graphs showing the time changes of the frost heaving amount and the water absorption / drainage amount when the water content W of the sample (frost heaving suppression roadbed material) is 9.7%, 12.9%, and 16.1%, respectively. Further, Figure 7 is a table summarizing the measurement conditions and measurement results of this example.

[0069] In this example, the following composition (mix ratio) of the present frost heaving suppression roadbed material, which has already been explained to satisfy the predetermined standards in terms of strength and deformation coefficient: · Dry crushed slag 1240.0 kg / m 3 · Portland cement 150.0 kg / m 3 (12.1 wt%) · Silicon dioxide (SiO2) 4.4 kg / m 3 (0.35 wt%) · Aluminum oxide (Al2O3) 1.7 kg / m 3 (0.14 wt%) · Calcium oxide (CaO) 3.2 kg / m 3 (0.26 wt%) · Magnesium oxide (MgO) 0.7 kg / m 3 (0.06 wt%) Three specimens were prepared using the above materials, and a frost heaving test was conducted in accordance with JGS 0172-2020 "Test method for frost heaving of soil for frost heaving determination".

[0070] Here, the 0.15 mm sieve passing rate P_0.15 and the coarse grain ratio G in the above dry-crushed slag were 3.0 and 3.2, respectively, as a result of measurement. The values of both of these (P_0.15 and G) are in agreement with the corresponding relationship between the two shown in the graph of Fig. 3. Furthermore, it is understood from the graph shown in Fig. 2(B) (showing the relationship between F and P_0.15) that the fine grain content ratio F in this dry-crushed slag is 2.3%.

[0071] Also, with respect to the above-described three specimens, water was added to the above-described frost-suppressing roadbed material in a dry state with the above-described mixing ratio so that the water content ratios W were 9.7%, 12.9%, and 16.1%, respectively, and after stirring and mixing, they were filled into molds having a diameter of 100 mm and a height of 50 mm, and then compacted (consolidated) in one layer with a predetermined weight (two drops from a height of 30 cm using a 2.5 kg rammer), and air curing was carried out for 14 days.

[0072] Here, the water content ratio W = 12.9% is a standard value in actual construction, while the water content ratios W = 9.7% and 16.1% are 75% and 125% of this standard value (12.9%), respectively. Thus, this example also serves to confirm whether or not there is variation in the frost heave rate ξ due to differences in the water content ratio (the amount of water sprayed during construction).

[0073] Also, the density ρ of the soil particles in these three specimens (water content ratios W = 9.7%, 12.9%, 16.1%) s was 2.76 g / cm 3 、2.74 g / cm 3 and 2.74 g / cm 3 respectively, and was generally constant, but the dry density ρ d after 14 days of air curing was 1.69 g / cm 3 、1.67 g / cm 3 and 1.73 g / cm 3As a result, it can be seen that the specimen (water content ratio W = 16.1%) had better compaction of the material due to the highest water content during production, which promoted the solidification reaction, resulting in fewer voids than other specimens. In fact, it has been confirmed that the water flow rate during the saturation process and the void ratio and saturation degree after saturation of this specimen (water content ratio W = 16.1%) are smaller values.

[0074] Specifically, in the frost susceptibility test of this example, for the specimen set in the frost susceptibility test apparatus, 10 kN / m 2 was applied as the axial load stress (vertical restraint stress), and after sufficiently increasing the saturation degree of the specimen by water flow saturation while maintaining the stress application state, the frost heave amount ΔH and the water absorption and drainage amount ΔV were measured. In addition, a thermal shock was applied to the specimen to form ice nuclei. After confirming the ice crystals, the temperature of the cooling plate was once again returned to around 0°C, and then the temperature was lowered again at a temperature drop rate of -0.10°C / h by the upper main cooling plate to freeze the specimen.

[0075] Here, the completion of freezing of the specimen was confirmed by the convergence of the drainage amount (stabilization of the water absorption and drainage amount ΔV). After that, the temperature of the upper main cooling plate was set and controlled at -10°C, and the temperature of the lower cooling plate was set and controlled at 0°C to establish a reference state (hereinafter also abbreviated as the normalization time) in which the secondary expansion amount (frost heave amount) appears. This secondary expansion amount (frost heave amount) is a quantity measured for the purpose of normalizing (stabilizing) the influence of the impermeable phase change existing in the frozen soil on the frost heave amount by aligning the temperatures as described above (generally, the temperature of the upper main cooling plate at the end of freezing varies depending on the specimen). The upper surface of the specimen in contact with the upper main cooling plate corresponds to the upper end surface of the roadbed on the outside air side during construction, while the lower surface of the specimen in contact with the lower cooling plate corresponds to the lower end surface of the roadbed on the ground side during construction.

[0076] After that, the temperatures of the upper and lower cooling plates were set and controlled at 10°C to start thawing the specimen, and the frost heave amount ΔH and the water absorption and drainage amount ΔV during the thawing process were measured.

[0077] According to the graphs in FIGS. 4, 5, and 6 and the table in FIG. 7, the frost heave amount ΔH at the end of freezing (position "A" in each graph of FIGS. 4 to 6) for these three specimens (water content ratios W = 9.7%, 12.9%, and 16.1%) f is 0.04 mm, 0.12 mm, and 0.02 mm respectively. As a result, the frost heave expansion rate ξ' (= ΔH f / H0 × 100) at the end of freezing is <At the end of freezing> For the specimen (water content ratio W = 9.7%), ξ' = 0.07 (= 0.04 / 55.5 × 100) % For the specimen (water content ratio W = 12.9%), ξ' = 0.22 (= 0.12 / 54.5 × 100) % For the specimen (water content ratio W = 16.1%), ξ' = 0.04 (= 0.02 / 51.0 × 100) % is the case.

[0078] Also, the frost heave amount ΔH at the time of normalization (when the secondary expansion amount appears, the temperature of the main cooling plate: -10 °C, positions "B" to "C" in each graph of FIGS. 4 to 6) s is 0.00 mm, 0.01 mm, and 0.00 mm respectively, and almost no frost heave is observed. As a result, the frost heave expansion rate ξ s (= ΔH s / H0 × 100) at the time of normalization is <At the time of normalization> For the specimen (water content ratio W = 9.7%), ξ s = 0.00 (= 0.00 / 55.5 × 100) % For the specimen (water content ratio W = 12.9%), ξ s = 0.02 (= 0.01 / 54.5 × 100) % For the specimen (water content ratio W = 16.1%), ξ s = 0.00 (= 0.00 / 51.0 × 100) % It is understood that almost no frost heave occurs in any of the specimens.

[0079] Here, the specimen (water content ratio W = 12.9%) has slightly larger frost heave expansion rates ξ' and ξ compared to the others sAlthough it is shown, it is considered to be due to differences in the freezing rate U caused by the physical state inside the specimen expressed depending on the water content ratio during production. Incidentally, the freezing rates U of these three specimens (water content ratios W = 9.7%, 12.9%, and 16.1%) were 1.64 mm / hour, 1.96 mm / hour, and 0.62 mm / hour, respectively.

[0080] Furthermore, the thaw settlement amount ΔH at the completion of thaw settlement, which is the time point when sufficient time has elapsed from the start of thawing (position "C" in each graph of FIGS. 4 to 6) for these three specimens (water content ratios W = 9.7%, 12.9%, 16.1%) t was 0.01 mm, -0.02 mm, and 0.05 mm, respectively, and no significant shrinkage (settlement) was observed.

[0081] Regarding the drainage phenomenon during such a thawing process, the drainage volumes (-ΔV) of these three specimens (water content ratios W = 9.7%, 12.9%, 16.1%) continued to increase over a long period from the start of thawing (position "C"). In particular, the drainage volumes (-ΔV) of the two specimens (water content ratios W = 9.7%, 12.9%) did not show a converging (stabilizing) behavior until the end, as shown in FIGS. 4 and 5, respectively. However, this is considered to be not the result of a large change in the specimen itself during the thawing process, but rather the result of the water content absorbed by the specimen during the saturation process of the specimen being discharged as it thaws. In fact, the thaw settlement rate ξ t (= ΔH t / H0 × 100) was -0.04 to 0.10%, and the change in the specimen due to thawing was extremely small.

[0082] As described above, according to this embodiment, the present frost prevention roadbed material has high water permeability in the freezing and thawing process as described above, so although it shows a large change in the water absorption and drainage volume ΔV, its frost heave amount ΔH and freezing expansion rate ξ are hardly affected by the production conditions with different water contents (water content ratios) and are extremely small values.

[0083] Specifically, in this frost heave suppression roadbed material where the passing rate P_0.15 through a 0.15 mm sieve is 3.0% (or less) or the coarse grain rate G is 3.2 (or more), as the degree of watering after spreading the frost heave suppression roadbed material during actual construction, even if the water content ratio of the frost heave suppression roadbed material varies within the range of 9.7 to 16.1%, the frost heave expansion rate ξ is (a) At the end of freezing, it is suppressed to less than 0.3% (in this example, ξ' = 0.04 to 0.22%), (b) At the time of normalization where the temperature of the lower end surface on the ground side is 10 °C lower than the temperature of the upper end surface on the outside air side, it is suppressed to less than 0.1% (in this example, ξ s = 0.00 to 0.02%) It is understood that.

[0084] [Frost Heave Suppression Roadbed Formation Method] Hereinafter, an outline of two embodiments of the frost heave suppression roadbed formation method according to the present invention will be described. <First Embodiment> (Step 1) To the crushed slag with a passing rate P_0.15 through a 0.15 mm sieve of 3.8% or less, cement is added and mixed at 4.0% by weight or more and 36% by weight or less. Further, silicon dioxide (SiO2), aluminum oxide (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO) are added and mixed at 0.10% by weight or more and 1.0% by weight or less, 0.05% by weight or more and 0.50% by weight or less, 0.08% by weight or more and 0.80% by weight or less, and 0.01% by weight or more and 0.12% by weight or less, respectively, to produce the frost heave suppression roadbed material according to the present invention. (Step 2) The produced frost heave suppression roadbed material is spread evenly to a predetermined height, and an appropriate amount of water is sprinkled on the spread frost heave suppression roadbed material to solidify this roadbed material. If necessary, the upper part of this roadbed material is lightly rolled to form a roadbed in which the frost heave is suppressed to 0.5% or less in terms of the frost heave expansion rate ξ.

[0085] <Second Embodiment> (Step 1) For the crushed slag with a 0.15 mm sieve passing rate P_0.15 of 3.0% or less, add cement in an amount of 4.0% by weight or more and 36% by weight or less and mix. Further, add silicon dioxide (SiO2), aluminum oxide (Al2O3), calcium oxide (CaO), and magnesium oxide (MgO) in amounts of 0.10% by weight or more and 1.0% by weight or less, 0.05% by weight or more and 0.50% by weight or less, 0.08% by weight or more and 0.80% by weight or less, and 0.01% by weight or more and 0.12% by weight or less, respectively, and mix to produce the frost heave suppression roadbed material according to the present invention. (Step 2) Spread the produced frost heave suppression roadbed material to a predetermined height, sprinkle an appropriate amount of water on the spread frost heave suppression roadbed material to solidify this roadbed material, and if necessary, lightly roll the upper part of this roadbed material to form a roadbed in which frost heave is suppressed to less than 0.3% in terms of the frost heave expansion rate ξ.

[0086] Thus, according to the above-described embodiments, by performing simple and short-time operations such as spreading the produced frost heave suppression roadbed material, sprinkling water to solidify it, and lightly rolling it, a roadbed with extremely low frost heave expansion rate ξ, high strength, and high water permeability can be formed. Therefore, for example, even in winter in cold regions, a suitable roadbed with suppressed frost heave can be formed. Also, it is easily possible to remove the already spread roadbed portion, spread this frost heave suppression roadbed material to a defined height thereon, and replace the roadbed in the same manner as above.

[0087] As described in detail above, according to the high-void roadbed material and semi-rigid roadbed construction method of the present invention, by suppressing the 0.15 mm sieve passing rate P_0.15 of the crushed slag to at least 3.8% or less, the proportion of fine particles that promote frost heave is reduced, and the occurrence of the frost heave phenomenon can be more reliably suppressed. Specifically, the frost heave expansion rate ξ can be suppressed to at least 0.5% or less.

[0088] In addition, by forming a roadbed with suppressed frost heaving as described above, for example, in a railway roadbed, it is possible to improve the riding comfort and reduce maintenance work, in a road roadbed, it is possible to improve the running performance and reduce maintenance work, and further in the roadbeds of sidewalks, parks and sports facilities, it is also possible to realize improvements in walkability and athletic performance.

[0089] It should be noted that all of the above-described embodiments are merely illustrative of the present invention and not restrictive. The present invention can be implemented in various other modified and changed forms. Therefore, the scope of the present invention is defined only by the scope of the claims and its equivalent scope.

Claims

1. A frost heave suppression roadbed material comprising granulated slag with a passing rate through a 0.15 millimeter (mm) sieve of 3.8 percent (%) or less, silicon dioxide, aluminum oxide, calcium oxide, and magnesium oxide, and having a frost heave expansion rate suppressed to 0.5% or less when spread evenly and watered to solidify.

2. The frost heave suppression roadbed material according to Claim 1, wherein the coarse grain ratio of the granulated slag is 3.1 or more.

3. The frost heave suppression roadbed material according to Claim 1 or 2, wherein the content rate of fine particles in the granulated slag is 2.9% or less.

4. The granulated slag has a passing rate through a 0.15 mm sieve of 3.0% or less, and the frost heave expansion rate is suppressed to less than 0.3% when spread evenly and watered to solidify. The frost heave suppression roadbed material according to any one of Claims 1 to 3.

5. The frost heave suppression roadbed material according to Claim 4, wherein the coarse grain ratio of the granulated slag is 3.2 or more.

6. The frost heave suppression roadbed material according to Claim 4 or 5, wherein the content rate of fine particles in the granulated slag is 2.3% or less.

7. The frost heave suppression roadbed material according to any one of Claims 4 to 6, wherein the frost heave expansion rate at the time of standardization, when frozen after being spread evenly and watered to solidify, is suppressed to less than 0.1%, with the temperature of the lower end face on the ground side being 10 degrees (°C) lower than the temperature of the upper end face on the outside air side.

8. The watering after spreading evenly is such that the water content ratio of the frost heave suppression roadbed material is in the range of 9.7% or more and 16.1% or less. The frost heave suppression roadbed material according to any one of Claims 4 to 7.

9. The frost heave suppression roadbed material further contains cement, The cement is contained only in an amount of 4.0% by weight or more and 36% by weight or less as a weight ratio to the granulated slag, The silicon dioxide, aluminum oxide, calcium oxide, and magnesium oxide are each contained only in an amount of 0.10% by weight or more and 1.0% by weight or less, 0.05% by weight or more and 0.50% by weight or less, 0.08% by weight or more and 0.80% by weight or less, and 0.01% by weight or more and 0.12% by weight or less as a weight ratio to the granulated slag. The frost heave suppression roadbed material according to any one of Claims 1 to 8.

10. For granulated slag with a passing rate of 0.15 mm sieve being 3.8% or less, cement is added and mixed at 4.0 wt% or more and 36 wt% or less. Further, silicon dioxide, aluminum oxide, calcium oxide, and magnesium oxide are each added and mixed at 0.10 wt% or more and 1.0 wt% or less, 0.05 wt% or more and 0.50 wt% or less, 0.08 wt% or more and 0.80 wt% or less, and 0.01 wt% or more and 0.12 wt% or less, respectively, to produce a roadbed material. The first step is as follows: The roadbed material is spread evenly to a predetermined height, water is sprayed on the spread roadbed material to solidify the roadbed material, and the second step is to form a roadbed with its frost heaving suppressed to a frost heave expansion rate of 0.5% or less. A method for forming a frost heave suppressing roadbed, characterized by comprising the above steps.

11. In the first step, granulated slag with a passing rate of 0.15 mm sieve being 3.0% or less is used. In the second step, a roadbed is formed with its frost heaving suppressed to a frost heave expansion rate of less than 0.3%. The method for forming a frost heave suppressing roadbed according to claim 10, characterized by the above steps.

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