JPH0826315B2 - Soil stabilization material, paving roadbed material and paving method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention replaces so-called roadbed crushed stones on paved roads with a soil stabilizer obtained by mixing Al-Fe-Ti-based oxides and lime into various natural soils existing in various places as local materials. However, using a physicochemically stabilized pavement base material, it is possible to introduce an elasticity theory into the pavement structure, and to make it a basic ground that maintains and secures self-healing strain. The present invention relates to a soil stabilization material, a pavement base material, and a pavement method capable of increasing the strength of a roadbed subbase according to an increase in the load of a passing traffic vehicle by Le Chatelier's law or the law of mass action.

[0002]

2. Description of the Related Art Conventionally, general pavement roads in Japan have been designed and constructed according to the pavement guidelines established by the country. As for the pavement structure by the CBR method shown in the pavement summary, the pavement thickness (H) was statistically determined by the construction results by the CBR which mainly indicates the strength of the subgrade soil based on the strength of the crushed stone used. However, it was sufficient as the transportation capacity at the time when the CBR method was developed. However, due to the weight increase and increase of vehicles accompanying the development of society, the improvement of the pavement structure was inevitably required.

Therefore, in order to supplement the pavement structure by the CBR method, based on the results of large-scale AASHO road tests, the equivalent conversion coefficient of each constituent member was determined based on the strength of asphalt that was mainly used at that time, and this was determined. used _(thickness in terms of the asphalt) T _a as measured modeling Yoki paved road pavement structure design according to method it came to be performed. However, in order to prevent the fatigue and rutting of the structural members caused by the increasing traffic volume, the research and development of the structural design based on the elasticity theory are now under way.

In addition, when constructing a road for exclusive use of automobiles, the Highway Public Corporation conducts a thorough survey of local location conditions, weather, terrain, etc.
Along with the study, conducted the field test, financially independent by the collection of tolls, maintenance due to this, taking into account the service or the like into savings and user of the repair costs, the location of our country the United States of modeled T _A method The pavement procedure shows the structural design to meet environmental conditions. According to the paving procedure, the paved road is a structure based on the ground, and in order to prevent the roadbed soil from being disturbed by the road design and service, or to make the soil of our country where there is much rain durable, Was divided into two layers, a road body and a roadbed, and a pavement made of crushed stone and asphalt was provided on it. The reason for dividing into two layers, the subgrade and the subgrade, is that the soil deformation coefficient (strength) is CBR × 100 in the United States based on the soil test results in Japan, but in Japan, it is the conventional subgrade soil. Then CBR × 20, good soil CBR × 40,
It is likely that it will be much weaker than other countries due to rainfall.

The inventor of the present application, as a method for constructing a paved road in a soft roadbed, is composed of a mixture of natural soil, converter slag, fine powder of iron oxide and slaked lime. Was invented (see Japanese Patent Publication No. 52-7256). Similarly, to reinforce a soft subgrade, a layer of a mixture of iron oxide fine powder, slaked lime and natural soil is formed on the subgrade, and a layer of base course material made of crushed stone is formed on it. A simple construction method of paved roads was invented (see Japanese Patent Publication No. 54-25738).

[0006]

By the way, the flexible pavement structure is a structure composed of roadbed (crushed stone) and ascon which are made by compacting a plastic body. In order to apply the elasticity theory to this structure, the pavement can be prevented from being worn by the passing traffic vehicle due to its flexibility, and the pavement can be disturbed and destroyed like rutting, or weakened by fatigue weathering of the roadbed. It has a function to prevent it, and regardless of the size of the traffic load, the deflection must always be maintained as self-healing.

[0007] That is, it is necessary to compact the pavement on the basis of the subgrade soil to the extent that the pavement maintains the elastic flexure. However, the bearing capacity ratio of subgrade soil in Japan is worse than that in the United States, and compaction at the time of construction is difficult. Therefore, it is necessary to have a structure having durability because the accumulation due to the wheel load of the automobile produces a rolling compaction effect.

By the way, the design method shown in the pavement guideline of the Highway Public Corporation is CBR = 8-10%, that is, E = 800-1,
The amount of pavement surface deflection was set to be 000 kg / cm ^2, and the target value was 0.7 mm in consideration of a safety factor of 3.5 times similar to that of a general structure. This 2.5m
In order to secure the deflection amount of m and 0.7 mm, the strength of the subgrade soil (deformation coefficient) as shown in Table 1 below is required.

[0009]

[Table 1]

[0010] The Japan Highway Public Corporation confirmed by a follow-up survey for 10 years after construction that the pavement surface deflection amount of 0.5 to 0.8 mm, which substantially satisfies the design target value of 0.7 mm, is maintained. . However, ten more years later, fatigue of the components, rutting, etc. occurred, and countermeasures had to be taken. It is natural to consider the social situation and economic development from the time when the CBR law was enacted to the present age, but in order to maintain durable pavement that meets the demand of society, the target value at the time of design was set to 0. It is probable that the amount of deflection of 0.7 mm was insufficient and the safety factor of 3.5 was not secured.

This 0.7 mm is said to be the amount of deflection within the elastic behavior limit of 10 ^-3 (1 m when the pavement is 1 m.
Although it satisfies m) for the time being, it only has a safety factor of about 1.6 times. This is the famous scholar Terzagh
It is the same as the safety factor of the construction structure mentioned by i. Therefore,
In order to have a durable pavement structure with a safety factor of 3.5 times similar to general structures, it is necessary to maintain and secure a pavement surface deflection amount of 0.3 mm. Become. In order to maintain this pavement surface deflection amount of 0.3 mm, the strength shown in Table 2 below is required for each traffic segment.

[0012]

[Table 2]

By the way, what is important in pavement structure design is that, unlike steel and concrete, the soil that forms the basis of the pavement changes in various ways depending on the environment and geographical conditions, and also because of the physicochemical properties of the soil particles. Due to its complexity, it is difficult to determine its strength.

Since the soil contains a large gap, it is deformed by its own weight and external force. Distortion is mentioned as a quantity describing this deformation. Soil is a plastic body, and its deformation due to pressure depends on the presence or absence of restraint force. Elastic strain is compression that does not change the structural framework of soil and recovers to its original shape when pressure is released, but plastic strain is irreversible deformation and does not recover when pressure is released. Also, the quality and amount of physical deformation of subsoil under superstructure loading is not only a function of applied load, but also of soil properties and time.
Soil is subject to rheological research as well as plastics. Deformation behaviors of soils include volume changes that expel pore air and pore water, shear shapes that cause displacement phenomena of soil particles and structural units, and this phenomenon includes measurable or impossible pore ejection and slip surface development. Is accompanied by.

Stress is generated inside the object that receives an external force so as to satisfy the equilibrium condition. That is, when an external force acts, a component perpendicular to an arbitrary cross section (vertical component) and an in-plane component (shear stress) occur. If this shear stress becomes large, it will be destroyed. Therefore, the stability of the ground is determined by the balance between the external force and the shear resistance force (shear strength).

In cohesive soils, this shear resistance is affected by the physicochemical properties of the soil particles. This is because the cohesive force and the shearing resistance force generated by the interaction of the soil particles consisting of the solid phase, the solution phase, and the gas phase, and the size of the ground contact area between the particles acting on both of them are the factors.

By the way, in the theory of pavement structure design, the pavement is considered as a board structure. However, the pavement is a compacted plastic board, unlike the cement concrete board, and has a limited diagonal line. The unevenness of the wheel load applied to, and the load is likely to be partially concentrated on the pavement surface, or because the soft subgrade soil has the property of flowing and deforming due to loading, stress caused by loading is reduced, It seems that it is almost impossible to reduce the size evenly to the extent that it does not affect the subgrade soil for a long time.

Therefore, it is necessary to research and develop a pavement structure designing method and its members that can be consumed (absorbed) by shear resistance (shear strength) instead of dispersing the stress generated by the applied load. Became.

That is, in order to prevent rutting, it is considered that not only the thickness of the pavement constituent member should be increased or decreased, but also the quality (deformation coefficient) of the constituent member as a cause should be improved or strengthened.

Therefore, the applicant of the present invention applies the theory of elasticity to the above pavement structure design method, and adds a soil stabilizer obtained by mixing iron oxide and lime to crushed stone or natural soil as a member applicable to the pavement structure design method. As a material, a material having a high elastic coefficient obtained by physicochemical action so that it can be used in place of a conventional roadbed was developed and applied for a patent (JP-A-04-3).
15601 publication).

It has been confirmed that the paved roadbed material for which the above-mentioned patent application has been made is very useful because its effect is confirmed. On the other hand, the above application presupposes the use of high quality masa soil as the natural soil, and also mixes the natural soil with crushed stone.

However, since it is premised that the local color is used in road pavement, it is not always possible to use high quality masa soil. Shirasu and silica sand may have to be used in some areas. By the way, in the above-mentioned patent application, sufficient strength cannot be secured when shirasu or silica sand is used as described later. If natural soil can be used without being limited to Masa soil, it will be very economical and efficient.

In addition, it has become difficult to obtain high-quality crushed stone in recent years, and in some cases it is necessary to use waste asphalt material or the like as a substitute for crushed stone. Therefore, if the roadbed can be formed without necessarily using the crushed stone, it is not necessary to secure good quality crushed stone, and the preparation work for the paved roadbed material can be simplified. That is, even if there is no crushed stone, it is only necessary to ensure strength that is not inferior to that obtained by mixing crushed stone.

[0024]

In order to solve the above problems, the paved roadbed material according to the present invention is made of Al-F containing aluminum oxide, iron oxide and titanium oxide as main components.
An e-Ti-based oxide composition or a mixture of aluminum oxide, iron oxide and titanium oxide, that is, Al-Fe-Ti-based oxide is added with lime to obtain an Al-Fe-Ti-based oxide.
Residue produced when aluminum is produced from bauxite
The red mud is used to ensure the required strength even when various types of natural soil are used.

The pavement base material according to the present invention is made of Al.
A soil stabilizer obtained by adding lime to a -Fe-Ti-based oxide;
It is a mixture of natural soil or natural soil containing crushed stone, which can be used in place of conventional roadbeds (bitumen stabilization treatment, crushed grain crushed stone, crusher run), and has a high elastic modulus.

Further, in the paving method according to the present invention, Al-Fe is used between the roadbed and the surface layer instead of the conventionally used paving roadbed.
-Laying a roadbed in which a soil stabilizer containing lime added to Ti-based oxide and natural soil or natural soil containing crushed stone are laid, whereby the pavement flexes elastically (self Healing).

[0027]

As described above, in order to prevent rutting caused by fatigue of the pavement structure, the external force (ground pressure) is not dispersed by each constituent member, but the shear resistance force (adhesive force, internal friction angle). Therefore, a pavement structure design method that can be consumed (absorbed) and its material (soil stabilization material) are required.

By the way, the properties of soil are as follows: solid phase, solution phase,
It is affected by the size of the ground contact area of soil particles consisting of gas phase, or the physical and chemical substances of soil particles.

The solid phase is composed of an inorganic component and an organic component. Inorganic components are primary particles in which rocks have become finer and secondary minerals in which primary minerals have been weathered. Secondary minerals are various clays, Fe, M
It is an oxide or hydroxide of n and Si, and changes further if the conditions under which the soil is placed change. Secondary minerals are also highly reactive due to their small particle size and large specific surface area.
It also has a charge and holds exchangeable ions. The organic component is a complex polymer mixture having a dissociative group and is involved in ion exchange and complex formation with an inorganic component.

The solution phase is an aqueous solution containing various inorganic and organic solutes, but since it is in contact with the solid phase having a large surface area, it forms a thin water film and clings to the surface of the solid phase.

The gas phase has a CO ₂ partial pressure higher than that in the atmosphere (0.03%) due to the respiration of plant roots and microorganisms, and reaches 1 to 5% in rhizosphere soil. When the exchange of soil air with the atmosphere is interrupted due to waterlogging or craft formation, oxygen is consumed by respiration, and the soil gradually changes to a reducing state. Therefore, it can be said that the soil in the field is in a dynamic state that is constantly changing.

That is, the soil is a place of chemical change, and ion exchange and adsorption between soil particles or their interaction are important factors when the soil is treated as the ground or a structure, and the soil (soil). Determine overall physical and chemical properties.

Further, the redox potential of soil is temporarily determined by oxygen and carbon dioxide dissolved in soil water and soil organic matter. Therefore, gaseous oxygen and CO in soil air
It depends on the partial pressure of _{2 and} on the pH of the soil solution.

The nature of the soil (soil) changes (weathers) depending on the natural environment conditions as described above. As an index of weathering, the sum of components having low mobility, Al ₂ O ₃ + Fe ₂ O ₃
+ Tio ₂ , the element mobility is Si> K, Na, Mg>Ca> Fe, Al, Ti in the early stage of weathering.
At the end of weathering, Si>Ca> K, Na, Mg>
Must be Fe, Al, Ti. Also, the concept of ionic potential should help explain which elements appear together in weathered rock or which elements are removed. For example, some tetravalent elements that are extremely rarely present are clustered within the ionic potential of the hydrolyzable volume.

Therefore, in consideration of the fact that bauxite is chemically enriched in beryllium and titanium, which are similar to aluminum, the inventor of the present pavement structure found that the soil which is stable in nature, that is, bauxite and laterite such as Al ₂
Focusing on the soil containing a large amount of O ₃ , Fe ₂ O ₃ , and Tio ₂ , the soil-based pavement, whose engineering characteristics are difficult to judge, is made of elastic material like general structures (steel, concrete). The development of the natural science was considered to be the best way to maintain and secure a dynamic and self-healing strain.

The Al-Fe-Ti-Ca oxide of the pavement material is a material that can make a pavement into a structure comparable to a general structure by the following chemical reaction rules or chemical reactions. .

A general law of chemical reactions in weathering under natural environment is Le Chatelier's law. It means that the system in the equilibrium reacts to return to the original equilibrium state under any force, and this equilibrium bear exists due to the reversibility of the reaction.

Chemical reaction aA + bB + ... cC + dD
When + ... reaches the chemical equilibrium, the ratio [C] ^c [D] ^d / [A] ^a [B] ^b = K of the concentration [] of each component becomes a constant only by temperature and pressure. This is called the law of mass action or the law of chemical equilibrium, and K is called the equilibrium constant. The above equation is often used for chemical equilibrium in a solution, and in that case, the constant is particularly referred to as a concentration equilibrium constant K _C.

The swelling of clay increases in proportion to the colloidal silica van ratio, SiO ₂ / Fe ₂ O ₃ + Al ₂ O ₃ , and also changes depending on the nature of the adsorbed cations.

The properties of the substances in the colloidal state are: ◎ a large effective surface (interface), ◎ ability to fix and hold solids, gas bodies, salts and ions,
◎ Having a contact action, that is, having an action of accelerating or inhibiting a chemical reaction, ◎ Finer particles have a faster dissolution rate.

Elements as constituents of natural soil are present in the form of silicate minerals, oxides, and hydrated oxides, and change variously depending on external conditions such as site environmental conditions. Also, F
The oxides and hydroxides of e and Al have a great influence on the physical and chemical properties of soil together with silicate minerals. It is considered that this is because the ion-exchange groups present on the surface of the Fe or Al hydrated oxide existing in the crystalline or amorphous state show a mutation charge characteristic in which the charge changes depending on the pH of the solution.

That is, these hydrated oxides are
Acts as a cation or anionic residue depending on the reaction
Or configure. The hydrated oxide of this element is in an acidic solution
And dissociate as follows. Fe (OH)_Three → Fe³⁺+ 3OH⁻  Al (OH)_Three → Al³⁺+ 3OH⁻

Fe Io, which has little mobility and remains in the inner layer,
The Al and Al ions are responsible for the positive charge of the particles. And
In the alkaline solution, the hydrated oxides of Fe and Al are
Take quality and dissociate as follows. H_Three・ FeO_Three → 3H⁺+ FeO_Three ^3-  Al³⁺+ 4OH⁻ ← → [Al (OH)_Four]⁻  In this case, the inner layer (potential determining layer) is less mobile
FeO_ThreeRemain and the particles gain a positive charge.

Gedroitz is all the adsorption energy
(Difficulty of leaching) and coagulation ability
The order is called syneresis series. According to this syneresis series,
When turned on, the result is as follows. Li⁺<Na⁺<NH_Four ⁺<K⁺<Mg²⁺<H⁺<C
a²⁺<Ba²⁺<Al³⁺Fe³⁺  This is also because the adsorption energy and coagulation ability of ions
The atomic weight between ions of the same valence
It shows that it increases with the increase of. This general
The exception to the law is the H ion, which is a monovalent cation
Depending on some, even larger than divalent Ca and Mg ions
It is said to be good.

The transition of the colloid from the sol state to the gel state is called coagulation, and the transition from the gel to the sol is called peptization. In general, colloids are mainly sol-shaped bears when they are saturated with monovalent ions, and when monovalent cations are replaced by divalent or trivalent cations and the charge decreases, they transfer to gel and become extremely Bond tightly. A thick sol of clay such as iron hydroxide or aluminum hydroxide becomes a liquid when shaken and becomes a gel again when left standing. The phenomenon of reversible conversion of sol and gel due to such mechanical causes is called thixotropy. Probably due to the network being destroyed and then rebuilt.

Ca ^{2+ in} lime replaces H ^{+ in} soil solutions, raising soil pH and altering the physiological system of soil. That is, the addition of lime increases the amount of the soil-dissolving carbonate (CaCO ₃ ) in the soil and raises the pH. For example, when a soil is flooded, its pH generally increases in acid soil and decreases in alkaline soil. In most soils, the pH value is 6.5 to 12 weeks after flooding.
It takes a stable value of 7.0. The increase in pH is mainly due to the increase in alkalinity due to carbonate.

The increase in alkalinity in the reduction process is
It can be explained by the formula. 5CH₂O + 4NO_Three ⁻ → 4HCO_Three ⁻+ CO + 2N₂+ 3H₂O CH₂O + 2Fe₂O_Three+ 7CO₂+ 3H₂O → 4Fe²⁺+ 8HCO_Three ⁻  2CH₂O + So_Four ⁻ → 2HCO_Three ⁻+ H₂S (CH₂O: organic acid)

Further, due to the increase in alkalinity, Fe
(II), Mn (II) hydroxide, carbonate precipitate
However, it is explained that the pH stabilizes near neutral.
It For example, Fe (OH)₂The precipitation of
U Fe²⁺+ 2HCO_Three → Fe (OH)₂+ 2CO₂  Through this reaction, part of the alkalinity is in the liquid phase (HCO_Three
⁻) To solid phase [Fe (OH)₂OH] inside
Therefore, the pH does not increase above a certain value.

However, under the conditions of wet and humid conditions as in Japan, Ca ²⁺ is eluted and the soil is acidified again (pH
However, it is unlikely that long-term strength will be maintained and secured.

The solubility of many substances is significantly affected by pH. The formation of laterite and bauxite is an example. That is, under natural conditions, aluminum has low mobility and remains in most soils. Iron also remains in the solid phase in most soils as well. Ferrous iron migrates easily, but is easily oxidized by ferric iron to form an oxide having low solubility.

[0051]

[Examples] In order to find the optimum mixing ratio of the treatment materials (iron oxide and lime) and natural soil (masa soil) originally developed by the inventor, the CBR test and the uniaxial compression test are not sufficient based on past construction results. It seems that the optimum mixing ratio of natural soil and stabilizing materials (iron oxide and lime) was obtained from the test results of the triaxial test to clarify the shear force. The triaxial test was conducted as follows.

JISA1210, a mixture of natural soil or a mixture of natural soil in a dry weight composition with a maximum particle size of 2 mm.
For the mold specified in paragraph 3, perform 1 layer 25 times 3 layer compaction,
Universal trimmer for triaxial test specimen (φ
25 mm, height 87.5 mm) is trimmed, and a triaxial test is performed while paying attention to prevent changes in the water content of the specimen. For the triaxial test after saturation with water, when setting in the compression chamber, set the upper and lower end plates of the specimen as water-permeable plates, and gradually reduce the gap between the specimens to a vacuum bear (600 mercury column).
mm) and the test piece was saturated with deaerated water, and then a triaxial test was performed. For the test materials after 3 days, 7 days, and 14 days after compaction, the specimen was coated with paraffin immediately after compaction to prevent changes in water content.

From Table 4 and the triaxial test results shown in FIG. 1 and FIG. 2, about 7% (weight ratio) of the stabilized material is mixed with the masa soil, and 35% of iron oxide is contained in the stabilized material. It was confirmed that the optimum blending ratio was ˜65%.

[0054]

[Table 4]

After 14 days of compaction by the compounding of the stabilizing agent, the strength after saturation increased 2.7 times as compared with that before saturation, and it can be said that this is a stabilizing agent adapted to the natural environment conditions of Japan.

In general, the strength changes depending on the size of the restraining force of the soil, and acid soil such as Japan is greatly weakened after being soaked in water. Also, weakly alkaline masa soil becomes slightly stronger immediately after saturation, but it has the property of weakening over a long period of time. Since this is not known in the short-term water immersion test (uniaxial compression test) in the test room, it is necessary to repeat the test over a long period of time.

Soil is a complex mixture or complex in which a solid phase, a liquid phase and a gas phase coexist. The percentage depends on the type of soil,
Or depending on the condition of the soil,
For example, in heavy clay soil, solid phase: liquid phase: gas phase = 45: 45:
10 is said to be 20:40:40 in volcanic ash soil.

The solid phase is composed of inorganic components (primary minerals, secondary minerals) and organic components produced by mechanically crushing rock and chemically decomposing it. Since the liquid phase is an aqueous solution containing various inorganic and organic solutes and is in contact with the solid phase having a large surface area, it forms a thin water film and clings to the surface of the solid phase. Also, the gas phase is higher than in the atmosphere due to the respiration of plant roots and microorganisms.
It is O ₂ partial pressure. Field soils are in a dynamic state that is constantly changing due to the interaction of physical external conditions and chemical phases.

By the way, Terzaghi mentioned above regarding practical engineering problems of soil emphasizes that "foundation and civil engineering are mainly based on experience. However, civil engineering is generally applied by applying science. It must also be emphasized that a relatively poor bear does not escape until a wealth of experience has accumulated.The task of science is to clarify the relationship between phenomena and causes. In the field of civil engineering,
To establish these relationships, it is necessary to study the physical properties of different types of soil, just as it is necessary to study the properties of steel and concrete in structural engineering. It is a thing. Given the strength and elastic modulus of a given steel or concrete, it is sufficient for many practical purposes. On the other hand, practical problems with soil require consideration of changes in soil properties. Main among these are permeability, compressibility, resistance to running water and shear, and stress-deformation relationships. As an example, in soft ground, the compression of clay proceeds slowly due to the increase in load. A small portion of this delay is due to the gradual adjustment of the particle position as the pressure increases. However, the delay of clay is largely due to the very low permeability of clay. As a result, it takes a long time to drain the excess water. "It has said.

Therefore, from the beginning of the development of the stabilizing material, the present inventor prevented the expansion, contraction, and weakening due to the addition of water in order to stabilize the soil in Japan, which has a lot of rain, and utilized the ground contact pressure due to the load of the service wheel. Aiming at producing a reverse weathering effect, we have mainly used a mixture of Masa soil and stabilizers (iron oxide, lime).

However, as described above, it is not possible to consider only a specific soil (masa soil) and volcanic ash soil is also taken into consideration, and the "law of mass action" which is the law of chemical reaction and the chemical characteristics of soil. The theory of "Kei Tetsuban ratio" which shows the value,
As an indicator of basalt weathering, the sum of components with low mobility,
Al ₂ O ₃ + Fe ₂ O ₃ + TiO ₂ is taken, and the mobility of elements is Si> K, Na, Mg> Ca in the early weathering.
> Fe, Al, Ti, Si> C at the end of weathering
It is considered necessary to have a compounding material that includes and applies a> K, Na, Mg> Fe, Al, Ti.
The stabilization treatment material (Al-Fe-Ti-based oxidation mixture) was compounded. Since the strength of natural soil changes depending on the content of secondary minerals and organic components, the ratio of each component in the stabilized material must be determined by the soil quality at the site. The blending ratio was obtained based on the triaxial test results in Table 4 above using a stabilizing material (iron oxide, lime) having a construction record of 20 years or more under natural location environmental conditions.

As the Al-Fe-Ti type oxide, the mixture shown in Table 3 was used. This mixture uses red mud, which is the residue when aluminum is produced from bauxite.

[0063]

[Table 3]

Table 5 shows the compounding ratio of the conventional example and the example of the present invention.
Shown in As a conventional example, a comparative example was a mixture of iron oxide fine powder with lime, which has been confirmed by the present applicant for many years, and the effect thereof, and one containing only slaked lime. In addition, as examples, three types having different compounding ratios were prepared, and each sample was designated as No. 1, No. 2, No. It was set to 3.

[0065]

[Table 5]

The inventor mixes not only masa soil, but also white sand or silica sand (unweathered) with the stabilizing material (Al-Fe-Ti-based oxide mixture), and the CBR test and uniaxial strength, which are general guidelines, are conducted. While conducting a test to confirm the increase in strength,
From K (K ₁ , K ₂ ) and S (swelling ratio), the stability of natural soil by the stabilizing material was confirmed.

Tables 6 to 10 show the properties and compositions of the masa soil, silica sand and shirasu used.

Table 6 shows the physical properties of Masa soil.

[0069]

[Table 6]

Table 7 shows the chemical composition of Masa soil as a percentage.

[0071]

[Table 7]

Table 8 shows the specific gravity and particle size composition of shirasu.

[0073]

[Table 8]

Table 9 shows the chemical composition of Shirasu as a percentage.

[0075]

[Table 9]

Table 10 shows the chemical composition and particle size distribution of silica stone powder.

[0077]

[Table 10]

Table 11 shows the calculated K ₁ value, K ₂ value and S value in order to show the stability of the treated soil according to the law of chemical reaction.

[0079]

[Table 11]

Further, theoretical analysis of Fe lime-treated soil roadbed (also serving as roadbed reinforcement) developed by the applicants, which has been modeled for more than 20 years --- 10 years follow-up survey data by Japan Highway Public Corporation, earth pressure gauge As a result of theoretical analysis of the measured values of vertical stress and measured values of pavement surface deflection, the strength constants that cannot be measured due to the soil characteristics or the complexity that changes depending on external conditions, as described in Terzaghi, Elastic modulus, compressive strength) is based on the CBR value which is the standard of pavement structure, compressive strength = 0.225 × CBR, elastic coefficient = 10
It was found that theoretical calculation with 0 × CBR is possible.

Next, Tables 12 to 17 show the results of the laboratory tests using the above samples.

Table 12 shows the CBR test results of the stabilized soil using Masa soil as the soil.

[0083]

[Table 12]

Table 13 shows the results of the uniaxial compression test of the stabilized soil using Masa soil as the soil.

[0085]

[Table 13]

Table 14 shows the CBR test results of the stabilized soil containing Shirasu as the soil.

[0087]

[Table 14]

Table 15 shows the results of the uniaxial compression test of the stabilized soil using Shirasu as the soil.

[0089]

[Table 15]

Table 16 shows C of the stabilized soil using silica sand as the soil.
It shows the BR test results.

[0091]

[Table 16]

Table 17 shows a table comparing the results of the respective strong tests.

[0093]

[Table 17]

The following can be seen from the above test results. The values of K ₁ and K ₂ are characteristic values peculiar to soil determined by the chemical composition of soil. (Table-O, Table-P) Both the CBR value and the uniaxial compressibility increase in proportion to the value of K ₂ (Tio ₂ content rate) rather than the value of K ₁ , indicating the effect of Tio ₂ . The strength obtained by the uniaxial compression test can be applied to cement concrete, and the CBR test in which the lateral flow is taken into consideration is appropriate for the soil in which the soil particles are adjusted by the pressure to have the strength.

The feature of the pavement structure to which the stabilizing material is applied is that the pavement and the ground are integrated to form a self-healing elastic body behavior, which makes it possible to apply the Burmister theoretical formula. It becomes possible to calculate the distribution of underground stress by using the stabilized subgrade soil instead of the complicated subgrade. By utilizing viscoelasticity, it is possible to make a structural design that can make a paved road into a permanent structure similar to a bridge in accordance with Article 35 of the Road Structure Ordinance.

Using the above indoor test values, “Road Structure Ordinance No. 3
The design of the pavement structure based on "5 Articles" is as follows. 1. Condition Car load 20ton car (wheel load P = 8to
n) Grounding radius a = P + 12 = 20 cm Grounding pressure (circular load distribution) q = 6.366 kg / cm
²  Elastic modulus E = 100 x CBR vertical (compressive) stress qu = 0.225 x CBR impact load = O The paved road made of the pavement structure and material has a viscoelastic behavior.
do. In addition, due to the theoretical analysis of construction results, conventional crushed stone
Unlike roadbed, it has excellent hydraulic properties, adaptability, and familiarity.
5 times as much as CBR for soft roadbed soil and CBR for good quality soil
It has been confirmed that the strength is 2.5 times stronger, and it absorbs the load.
It is considered that it is not necessary to consider impact load because it will be accommodated
You In the calculation below, CBR is 260 (28 days
Water immersion).

2. Pavement structure design example [Pavement example 1] First, Tables 18 and 19 show examples where the surface layer is cement concrete.

Table 18 shows the equivalent conversion value of the roadbed thickness based on the concrete pavement schedule in 1984.

[0099]

[Table 18]

Table 19 confirms the safety according to Article 35 of the Road Structure Ordinance.

[0101]

[Table 19]

[Pavement example 2] Next, an example in which the surface layer is asphalt concrete is shown in Table 2
0 to Table 23.

Table 20 shows calculated values when the stabilized soil of the present invention is used, based on the pavement structure based on the asphalt pavement summary in 1988.

[0104]

[Table 20]

Table 21 shows the safety confirmed by Article 35 of the Road Structure Ordinance.

[0106]

[Table 21]

Table 22 shows an example of pavement structure design in which the surface layer is considered to be a wear layer and a cushion, and the roadbed thickness is determined so as to secure a deflection amount of 0.3 mm on the roadbed surface.

[Table 22]

Similar to Table 22, Table 23 also shows an example of pavement structure design in which the surface layer is considered to be a wear layer and a cushion, and the roadbed thickness is determined so as to secure a deflection amount of 0.3 mm on the roadbed surface. Is.

[0109]

[Table 23]

[0110] Although the above examples showed that using a soil stabilization material using red mud which is a residue when produced aluminum from bauxite as Al-Fe-Ti-based oxides, according to the present invention For paving roadbed materials and paving methods
As a matter of course, the Al-Fe-Ti-based oxide is not limited to this, and may be a mixture of aluminum oxide, iron oxide and titanium oxide appropriately.

The soil stabilizer of the present invention can be used not only for pavement structures but also for comprehensive ground improvement such as prevention of landslides and consolidation settlement.

[0112]

As described above, the soil stabilizer according to the present invention is obtained by adding lime to an Al-Fe-Ti-based oxide to obtain Al-Fe-Ti-based oxide from bauxite.
Uses red mud, which is the residue when aluminum is manufactured
Therefore, the Al-Fe-Ti-based oxide is contained in a well-balanced manner.
Nationwide because it is cheap and easy to transport what you have
It can be obtained, and by mixing it with various types of natural soil, a roadbed material having sufficient strength can be obtained.

The paved roadbed material according to the present invention is Al-
Since the soil stabilizer obtained by adding lime to the Fe-Ti-based oxide and the natural soil or the natural soil containing crushed stone are mixed, it can be used in place of the conventional so-called roadbed crushed stone. It can be promoted to increase early strength and enhance the compaction effect.

Then, according to the paving method of the present invention,
Between the roadbed and the surface layer, replace the conventional paved roadbed with Al-
Since a roadbed was prepared by mixing soil stabilizers made by adding lime to Fe-Ti-based oxides and natural soil or natural soil containing crushed stone, the roadbed soil was prevented from weakening and the load on transit vehicles was increased. As a result, the strength of the roadbed can be increased.

[Brief description of drawings]

FIG. 1 is a graph showing an optimum blending ratio obtained from the triaxial test results in Table 4.

FIG. 2 is a graph showing an optimum blending ratio obtained from the triaxial test results in Table 4.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // C09K 103: 00

Claims (8)

[Claims] 1. An Al-Fe-Ti-based oxide composition containing aluminum oxide, iron oxide and titanium oxide as main components, or a mixture of aluminum oxide, iron oxide and titanium oxide (hereinafter, the composition or mixture is referred to as "Al- "Fe-Ti-based oxide") is added with lime, and Al-Fe-Ti-based acid is added.
When producing aluminum from bauxite as a compound
A soil stabilization material characterized by using red mud, which is the residue of . 2. A paved roadbed material characterized by mixing a soil stabilizer obtained by adding lime to an Al—Fe—Ti oxide and natural soil or natural soil containing crushed stone. 3. The Al-Fe-Ti-based oxide in the soil stabilizer is contained in a proportion of 5% by weight or more of aluminum oxide, 15% by weight or more of iron oxide, and 0.5% by weight or more of titanium oxide. The paved roadbed material according to Item 2 . 4. The ratio of the Al—Fe—Ti oxide and the lime of the soil stabilizer is 30 to 70:70 to 30.
The paved roadbed material described in 2 . 5. The ratio of the soil stabilizer to the natural soil or the mixture of natural soil and crushed stone is 3 to 10:97 to 90.
The paved roadbed material described in 2 . 6. A soil stabilizer obtained by adding lime to an Al—Fe—Ti oxide and a natural soil or a natural soil containing crushed stone, in place of a conventionally used paved roadbed, between the roadbed and the surface layer. A paving method characterized by laying mixed roadbeds. 7. The paving method according to claim 6 , wherein the surface layer is asphalt concrete. 8. The paving method according to claim 6 , wherein the surface layer is cement concrete.