JPH0790271A - Soil stabilizer, paving subbase course material and paving process - Google Patents

Abstract

PURPOSE:To obtain a soil stabilizer which is useful in paving subbase course material because it sustains self-healable strain and increases the strength of the subgrade course by adding lime to an Al-Fe-Ti based oxide composition. CONSTITUTION:Lime is admixed to an Al-Fe-Ti based composition mainly containing aluminum oxide, iron oxide and titanium oxide or a mixture of aluminum oxide, iron oxide and titanium oxide to provide the stabilizer. The ratio of the oxide composition to the lime is preferably (30-70)/(70-30), and the paving subbase course material is prepared by mixing the stabilizer with natural soil or a mixture thereof with macadam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is to replace the so-called subgrade crushed stone of paved roads with a soil stabilizer containing Al-Fe-Ti oxide and lime mixed with various natural soils existing in various places as local materials. However, using the pavement base material that has been physically and chemically stabilized, it is possible to introduce the elasticity theory into the pavement structure,
It is possible to create a foundation ground that maintains and secures self-healing strains, and to increase the strength of the subgrade as the load of passing vehicles increases by Le Chatelier's law or the law of mass action. Soil stabilizers made possible,
The present invention relates to a paved roadbed material and a paving method.

[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, from the results of a large-scale AASHO road test, the equivalent conversion coefficient of each component was determined based on the strength of asphalt that was mainly used at that time, and this was determined. Pavement structure design by the T _A (thickness converted to asphalt) method, which is used to model good pavement roads, has come 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 made (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, when considering the durability of flexible pavement from the theory of elasticity, the flexible pavement structure has various types of crushed stone of plastic, ascon, etc. To prevent
The flexure of the pavement is intended to prevent the pavement from being disturbed and destroyed, such as rubbing, and to prevent fatigue weathering and weakening of the roadbed. Regarding the size of the flexure, the flexure is always self-healing regardless of the size of the traffic load, and the current state of the pavement must be maintained.

[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,
Determined to be 000 kg / cm ² , the amount of pavement surface deflection is 0.7 m, taking into account the 3.5 times safety factor similar to general structures.
The target value was m. In order to secure the deflection amount of 2.5 mm and 0.7 mm, the strength (deformation coefficient) of the subgrade soil 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 same as the safety factor of the erected structure described by the famous scholar Terzaghi. Therefore, in order to have a durable pavement structure with a safety factor of 3.5, which is similar to that of general structures, it is necessary to maintain and secure a pavement surface deflection amount of 0.3 mm. It will be. 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 a research object of rheology 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-Fe-Ti containing aluminum oxide, iron oxide and titanium oxide as main components.
-Based oxide composition or a mixture of aluminum oxide, iron oxide and titanium oxide, that is, Al-Fe-Ti-based oxide with lime added, and the required strength even when using various natural soils. This is something that can be secured.

The paved roadbed material according to the present invention is Al-F.
It is a mixture of a soil stabilizer made by adding lime to an e-Ti oxide and natural soil or natural soil containing crushed stone. It is used in place of the conventional roadbed (bitumen stabilization treatment, grain-crushed stone, crusher run). It is possible to obtain a high elastic modulus.

Further, the pavement method according to the present invention includes a soil stabilizer between the subgrade and the surface layer, in which lime is added to Al-Fe-Ti-based oxide, instead of the conventional paved roadbed, and natural soil. Alternatively, a roadbed in which natural soil containing crushed stone is mixed is laid so that the pavement is elastically flexible (self-healing) with respect to passing traffic load.

[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 include various clays, Fe, Mn,
Si oxide or hydroxide, which will change 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 (weathering) depending on the natural environment conditions as described above, but the inventor of the pavement structure used the sum of the components having low mobility, Al ₂ O, as an index of weathering. 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, and Si>Ca> K, in the final stage of weathering. Being Na, Mg> Fe, Al, Ti. Also, the concept of ionic potential helps to explain which elements appear together in weathered rocks or which elements are removed during weathering, eg some of the 4 rare occurrences. Valent elements are clustered in the ionic potential range of the hydrolyzable volume.

Therefore, considering that bauxite is chemically enriched in beryllium and titanium, which are similar to aluminum, it is considered that soils that are stable in nature, that is, bauxite, laterite, Al ₂ O ₃ , Fe ₂ O ₃ , Focusing on soil containing a large amount of Tio ₂ , the pavement based on soil, whose engineering characteristics are difficult to determine, is elastic and self-healing, similar to general structures (steel, concrete) In order to maintain and secure the strain, it was thought that utilizing the natural science was the best means, and the development of the physicochemically stabilized soil was achieved.

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 equilibrium reacts to return to the original equilibrium state under any force, and this equilibrium state 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 concentrations [] of each component is 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 depends on the colloidal silica ratio, Si
It increases in proportion to O ₂ / Fe ₂ O ₃ + Al ₂ O ₃ and also changes depending on the nature of the adsorbed cation.

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, Fe,
Al oxides and hydroxides, as well as silicate minerals, have a great influence on the physical and chemical properties of soil. This is probably because the ion-exchange groups on the surface of Fe or Al hydrated oxides, which are present in crystalline or amorphous form, exhibit a mutated charge characteristic in which the charge changes depending on the pH of the solution.

That is, these hydrated oxides act as cations or form anionic residues depending on the reaction of the dispersion medium. The hydrated oxide of this element dissociates in an acidic solution as follows. ^{_{Fe (OH) 3 → Fe 3+}} + 3OH - Al (OH) 3 → Al 3+ + 3OH -

Fe ions with low mobility remaining in the inner layer,
Al ions are responsible for the positive charge of the particles. And in alkaline solution, the hydrated oxides of Fe and Al take on the properties of acid,
Dissociate as follows. ^{_{H 3 · FeO 3 → 3H +}} + FeO 3 3- Al 3+ + 4OH - ← → [Al (OH) 4] - less movability inner layer (potential determining layer) in this case
FeO ₃ remains and the particles gain a positive charge.

Gedrowitz was arranged in a fixed order from all adsorption energies (difficulty of leaching) and coagulation ability, and this order was called a syneresis series. Ions are arranged according to this syneresis series as follows. Li ⁺ <Na ⁺ <NH ₄ ⁺ <K ⁺ <Mg ²⁺ <H ⁺ <Ca ²⁺
<Ba ²⁺ <Al ³⁺ Fe ³⁺ This also shows that the adsorption energy and solidification ability of ions increase with increasing valence, and between ions of the same valence increase with increasing atomic weight. An exception to this general rule is the H cation, which is a monovalent cation, and is said by some scholars to be even larger than the divalent Ca and Mg ions.

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 in a sol state when they are saturated with monovalent ions, and when monovalent cations are replaced with divalent or trivalent cations and the charge decreases, they transfer to gel and are extremely strong. Bind to. 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 solution, raising soil pH and altering the physiological system of soil. That is, the dissolution of carbonate in soil by the addition of lime
(CaCO ₃ ) increases and pH rises. For example, when a soil is submerged, its pH generally increases in acidic soil and decreases in alkaline soil. 4 in most soils after flooding
After about 12 weeks, the pH value is 6.5 to 7.0, which is a stable value. The increase in pH is mainly due to the increase in alkalinity due to carbonate.

The increase in alkalinity in the reduction process can be explained by the following equation. ^{_{5CH 2 O + 4NO 3 - →}} 4HCO 3 - + CO + 2N 2 +
3H ₂ O CH ₂ O ＋ 2Fe ₂ O ₃ ＋ 7CO ₂ ＋ 3H ₂ O → 4Fe ²⁺ ＋ 8HC
_{^{O 3 - 2CH 2 O + So}} 4 - → 2HCO 3 - + H 2 S (CH 2 O:
Organic acid)

Further, as the alkalinity increases, Fe (I
It is explained that the precipitation of hydroxides and carbonates of I) and Mn (II) occurs, and the pH stabilizes near neutral. For example, Fe (O
The precipitation of H) ₂ follows the following reaction scheme. Through _{^{Fe 2+ + 2HCO 3 → Fe (}} OH) 2 + 2CO 2 The reaction, some of the alkalinity liquid phase (HCO ₃ ^-)
To solid phase [OH in Fe (OH) ₂ ], pH does not increase above a certain value.

However, under the condition of heavy rain and wetness as in Japan, Ca ²⁺ is eluted and the soil is acidified again (reduction of pH), so that it cannot be expected to maintain and secure long-term strength.

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, the upper and lower end plates of the specimen were set as water-permeable plates when set in the compression chamber, and the gap between the specimens was gradually reduced to a vacuum state (600 g of 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.
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 about the practical engineering problem of soil said, "It is emphasized that basic engineering and civil engineering are mainly based on experience. However, civil engineering generally applies science. It must also be emphasized that we will not get out of a relatively poor condition until we have abundant experience.
The task of science is to reveal the relationship between phenomena and causes. In the areas of foundation and civil engineering, it is necessary to study the physical properties of different types of soil in order to establish these relationships, but it is just to study the properties of steel and concrete in structural engineering. Is similar to what you need. 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> Fe, Al, Ti in the early weathering, and Si> Ca in the final weathering. > K, Na, Mg> Fe, Al, Ti, etc. are considered to be necessary, and it is considered necessary to have a compounding material that can be applied. Therefore, in the composition of the stabilizing material (Al-Fe-Ti-based oxidation mixture) I arrived. 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-based 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 has found that not only masa soil, but also white sand and silica sand (unweathered) are treated with the stabilizer (Al-Fe-Ti-based oxidation mixture).
CBR test and uniaxial strength test, which are generally used as a standard, to confirm the increase in strength, and K (K
_{From 1} , K ₂ ) and S (swelling ratio), the stability of natural soil by the stabilized 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, a roadbed of Fe lime treated soil developed by the applicants, which has been modeled for 20 years or more (also serves as reinforcement of the roadbed)
-Theoretical analysis of the 10-year follow-up survey data of the Japan Highway Public Corporation, the vertical stress actual measurement value by the earth pressure gauge, and the pavement surface deflection actual measurement value theoretical analysis based on the characteristics of Terzaghi mentioned above The strength constants (elastic modulus, compressive strength), which cannot be measured due to the complexity that varies depending on the authority, are based on the CBR value which is the standard of the pavement structure. Compressive strength = 0.225 x CBR, elastic coefficient = 100 x CBR
It was found that the theoretical calculation with

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) rather than the value of K ₁ ,
The effect of Tio ₂ is shown. 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.

A feature of the pavement structure to which the stabilizing material is applied is that the pavement body and the ground are integrated to form a self-healing elastic body behavior, and the Burmister theoretical formula can be applied. 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 = 0 The paved road made of the pavement structure and the material behaves like a viscoelastic body. In addition, due to the theoretical analysis of the construction results, unlike conventional crushed stone roadbed, it has excellent hydraulic properties, adaptability, familiarity, etc.
It has been confirmed that the strength of soft subgrade soil is 5 times that of CBR, and that of good quality soil is 2.5 times that of CBR. Since it absorbs the load, it is considered that impact load does not need to be considered. In the following calculation, CBR was calculated at 260 (28 days immersion in water).

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] Tables 20 to 23 show examples in which the surface layer is asphalt concrete.

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]

In the above-mentioned examples, red mud, which is a residue when aluminum is produced from bauxite, is used as the Al-Fe-Ti-based oxide, but as the Al-Fe-Ti-based oxide, It is needless to say that it is not limited to this, and may be a mixture of aluminum oxide, iron oxide and titanium oxide appropriately.

It is also possible to use sewage sludge incineration ash as an Al-Fe-Ti type oxide. As shown in Table 24 below, the sewage sludge incineration ash contains all of these components in appropriate amounts. Since sewage sludge incineration ash also contains lime, when using sewage sludge incineration ash, about half of the amount of slaked lime used is sewage sludge incineration ash, the purpose of the present invention It is possible to obtain a soil stabilizer that has achieved

[0112]

[Table 24]

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

[0114]

As described above, since the soil stabilizer according to the present invention has lime added to the Al-Fe-Ti-based oxide,
By mixing this 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-Fe-
Since a soil stabilizer containing lime added to Ti-based oxide and natural soil or natural soil containing crushed stone are mixed, it can be used in place of conventional so-called roadbed crushed stone, and promotes the chemical action of treated soil. The early strength can be increased and the compaction effect can be enhanced.

Then, according to the paving method of the present invention,
Between the roadbed and the surface layer, replace Al-Fe-
Since the soil stabilizer with lime added to the Ti-based oxide and the roadbed mixed with natural soil or natural soil containing crushed stone were laid,
It is possible to prevent the softening of the subgrade soil and increase the strength of the subgrade roadbed as the load of the passing traffic vehicle increases.

[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.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

5. A paved roadbed material characterized by mixing a soil stabilizer obtained by adding lime to an Al-Fe-Ti-based oxide, and natural soil or natural soil containing crushed stone.

6. The Al-Fe-Ti-based oxide in the soil stabilizer is 5% by weight or more of aluminum oxide, 15% by weight or more of iron oxide,
The paved roadbed material according to claim 5, which contains titanium oxide in an amount of 0.5% by weight or more.

7. Al-Fe-Ti-based oxide and the ratio of the lime soil stabilizing material is 30-70: 70-30 paved roadbeds of claim 5, wherein.

8. The ratio of the soil stabilizer to the natural soil or a mixture of natural soil and crushed stone is 3 to 10:97 to 90.
The paved roadbed material described in 5 .

Between 9. subgrade and the surface, instead of the pavement subgrade conventional use, a soil stabilizer material added lime to Al-Fe-Ti-based oxides, natural soil containing natural soil or crushed stone A paving method characterized by laying mixed roadbeds.

[Claim 1 0] surface layer paving method according to claim 9, wherein the asphalt concrete.

[Claim 1 1] surface layer paving method according to claim 9, wherein the cement concrete.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is to replace the so-called subgrade crushed stone of paved roads with a soil stabilizer containing Al-Fe-Ti oxide and lime mixed with various natural soils existing in various places as local materials. However, using the pavement base material that has been physically and chemically stabilized, it is possible to introduce the elasticity theory into the pavement structure,
It is possible to create a foundation ground that maintains and secures self-healing strains, and to increase the strength of the subgrade as the load of passing vehicles increases by Le Chatelier's law or the law of mass action. Soil stabilizers made possible,
The present invention relates to a paved roadbed material and a paving method.

[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, from the results of a large-scale AASHO road test, the equivalent conversion coefficient of each component was determined based on the strength of asphalt that was mainly used at that time, and this was determined. Pavement structure design by the T _A (thickness converted to asphalt) method, which is used to model good pavement roads, has come 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 made (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, a flexible pavement
The mounting structure is the roadbed (crushed stone) and asphalt that is made by compacting a plastic body.
It is a structure consisting of con. Apply elasticity theory to this structure
The pavement is flexible due to the passage of traffic vehicles.
Prevents abrasion of the surface, and of pavement such as rutting
Prevents turbulence and destruction, or weakening due to fatigue weathering of the roadbed
It has the function of stopping, and regardless of the size of the traffic load , the deflection must always be maintained in a self-healing state .

[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,
Determined to be 000 kg / cm ² , the amount of pavement surface deflection is 0.7 m, taking into account the 3.5 times safety factor similar to general structures.
The target value was m. In order to secure the deflection amount of 2.5 mm and 0.7 mm, the strength (deformation coefficient) of the subgrade soil 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 same as the safety factor of the erected structure described by the famous scholar Terzaghi. Therefore, in order to have a durable pavement structure with a safety factor of 3.5, which is similar to that of general structures, it is necessary to maintain and secure a pavement surface deflection amount of 0.3 mm. It will be. 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 a research object of rheology 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-Fe-Ti containing aluminum oxide, iron oxide and titanium oxide as main components.
-Based oxide composition or a mixture of aluminum oxide, iron oxide and titanium oxide, that is, Al-Fe-Ti-based oxide with lime added, and the required strength even when using various natural soils. This is something that can be secured.

The paved roadbed material according to the present invention is Al-F.
It is a mixture of a soil stabilizer made by adding lime to an e-Ti oxide and natural soil or natural soil containing crushed stone. It is used in place of the conventional roadbed (bitumen stabilization treatment, grain-crushed stone, crusher run). It is possible to obtain a high elastic modulus.

Further, the pavement method according to the present invention includes a soil stabilizer between the subgrade and the surface layer, in which lime is added to Al-Fe-Ti-based oxide, instead of the conventional paved roadbed, and natural soil. Alternatively, a roadbed in which natural soil containing crushed stone is mixed is laid so that the pavement is elastically flexible (self-healing) with respect to passing traffic load.

[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 include various clays, Fe, Mn,
Si oxide or hydroxide, which will change 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 less mobile components, Al ₂ O ₃ + Fe ₂ O ₃ + Tio _2, is taken, and the mobility of elements is Si> K, Na, Mg in the early weathering stage.
>Ca> Fe, Al, Ti, Si>Ca> K, Na, Mg> at the end of weathering
Must be Fe, Al, Ti. Moreover, retaining clips Yakuritsu concept of ion potential, to explain whether appear which elements concomitantly during weathering rocks, or which elements are removed
When. For example, some tetravalent elements that are extremely rarely present are clustered within the ionic potential of the hydrolyzable volume .

[0035] therefore bauxite, considering that it is enriched in chemically beryllium and titanium similar to aluminum, the inventors of the present pavement structures, such as stable soil ie bauxite or laterite in nature Al ₂ O ₃ ,
While paying attention to soil containing a large amount of Fe ₂ O ₃ and Tio ₂ , pavement based on soil, whose engineering characteristics are difficult to judge, is elastic and self-similar to general structures (steel, concrete). maintain the distortion of 癒性, to ensure has led to the development we believe that take advantage of the natural sciences is the best means Monodea
It

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 equilibrium reacts to return to the original equilibrium state under any force, and this equilibrium state 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 concentrations [] of each component is 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.

Clay swelling is due to colloidal silicaVan
Ratio, SiO₂/ Fe₂O₃ + Al₂O₃ Increase in proportion to and also adsorption
It depends on the nature of the 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, Fe,
Al oxides and hydroxides, as well as silicate minerals, have a great influence on the physical and chemical properties of soil. This is probably because the ion-exchange groups on the surface of Fe or Al hydrated oxides, which are present in crystalline or amorphous form, exhibit a mutated charge characteristic in which the charge changes depending on the pH of the solution.

That is, these hydrated oxides act as cations or form anionic residues depending on the reaction of the dispersion medium. The hydrated oxide of this element dissociates in an acidic solution as follows. ^{_{Fe (OH) 3 → Fe 3+}} + 3OH - Al (OH) 3 → Al 3+ + 3OH -

Fe ions with low mobility remaining in the inner layer,
Al ions are responsible for the positive charge of the particles. And in alkaline solution, the hydrated oxides of Fe and Al take on the properties of acid,
Dissociate as follows. ^{_{H 3 · FeO 3 → 3H +}} + FeO 3 3- Al 3+ + 4OH - ← → [Al (OH) 4] - less movability inner layer (potential determining layer) in this case
FeO ₃ remains and the particles gain a positive charge.

Gedrowitz was arranged in a fixed order from all adsorption energies (difficulty of leaching) and coagulation ability, and this order was called a syneresis series. Ions are arranged according to this syneresis series as follows. Li ⁺ <Na ⁺ <NH ₄ ⁺ <K ⁺ <Mg ²⁺ <H ⁺ <Ca ²⁺
<Ba ²⁺ <Al ³⁺ Fe ³⁺ This also shows that the adsorption energy and solidification ability of ions increase with increasing valence, and between ions of the same valence increase with increasing atomic weight. An exception to this general rule is the H cation, which is a monovalent cation, and is said by some scholars to be even larger than the divalent Ca and Mg ions.

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 in a sol state when they are saturated with monovalent ions, and when monovalent cations are replaced with divalent or trivalent cations and the charge decreases, they transfer to gel and are extremely strong. Bind to. 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 solution, raising soil pH and altering the physiological system of soil. That is, the dissolution of carbonate in soil by the addition of lime
(CaCO ₃ ) increases and pH rises. For example, when a soil is submerged, its pH generally increases in acidic soil and decreases in alkaline soil. 4 in most soils after flooding
After about 12 weeks, the pH value is 6.5 to 7.0, which is a stable value. The increase in pH is mainly due to the increase in alkalinity due to carbonate.

The increase in alkalinity in the reduction process can be explained by the following equation. ^{_{5CH 2 O + 4NO 3 - →}} 4HCO 3 - + CO + 2N 2 +
3H ₂ O CH ₂ O ＋ 2Fe ₂ O ₃ ＋ 7CO ₂ ＋ 3H ₂ O → 4Fe ²⁺ ＋ 8HC
_{^{O 3 - 2CH 2 O + So}} 4 - → 2HCO 3 - + H 2 S (CH 2 O:
Organic acid)

Further, as the alkalinity increases, Fe (I
It is explained that the precipitation of hydroxides and carbonates of I) and Mn (II) occurs, and the pH stabilizes near neutral. For example, Fe (O
The precipitation of H) ₂ follows the following reaction scheme. Through _{^{Fe 2+ + 2HCO 3 → Fe (}} OH) 2 + 2CO 2 The reaction, some of the alkalinity liquid phase (HCO ₃ ^-)
To solid phase [OH in Fe (OH) ₂ ], pH does not increase above a certain value.

However, under the condition of heavy rain and wetness as in Japan, Ca ²⁺ is eluted and the soil is acidified again (reduction of pH), so that it cannot be expected to maintain and secure long-term strength.

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, the upper and lower end plates of the specimen were set as water-permeable plates when set in the compression chamber, and the gap between the specimens was gradually reduced to a vacuum state (600 g of 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.
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 about the practical engineering problem of soil said, "It is emphasized that basic engineering and civil engineering are mainly based on experience. However, civil engineering generally applies science. It must also be emphasized that we will not get out of a relatively poor condition until we have abundant experience.
The task of science is to reveal the relationship between phenomena and causes. In the areas of foundation and civil engineering, it is necessary to study the physical properties of different types of soil in order to establish these relationships, but it is just to study the properties of steel and concrete in structural engineering. Is similar to what you need. 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> Fe, Al, Ti in the early weathering, and Si> Ca in the final weathering. > K, Na, Mg> Fe, Al, Ti, etc. are considered to be necessary, and it is considered necessary to have a compounding material that can be applied. Therefore, in the composition of the stabilizing material (Al-Fe-Ti-based oxidation mixture) I arrived. 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-based 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 has found that not only masa soil, but also white sand and silica sand (unweathered) are treated with the stabilizer (Al-Fe-Ti-based oxidation mixture).
CBR test and uniaxial strength test, which are generally used as a standard, to confirm the increase in strength, and K (K
_{From 1} , K ₂ ) and S (swelling ratio), the stability of natural soil by the stabilized 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, a roadbed of Fe lime treated soil developed by the applicants, which has been modeled for 20 years or more (also serves as reinforcement of the roadbed)
-Theoretical analysis of the 10-year follow-up survey data of the Japan Highway Public Corporation, the vertical stress actual measurement value by the earth pressure gauge, and the pavement surface deflection amount actual measurement value, based on the characteristics of the soil or outside strength parameters (modulus, compressive strength) Therefore the complexity, etc. which changes conditions, that is unmeasurable, based on the CBR value is a measure of the pavement structure, compressive strength = 0.225 × CBR, elastic modulus = 100 x CBR
It was found that the theoretical calculation with

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) rather than the value of K ₁ ,
The effect of Tio ₂ is shown. 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.

A feature of the pavement structure to which the stabilizing material is applied is that the pavement body and the ground are integrated to form a self-healing elastic body behavior, and the Burmister theoretical formula can be applied. 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 = 0 The paved road made of the pavement structure and the material behaves like a viscoelastic body. In addition, due to the theoretical analysis of the construction results, unlike conventional crushed stone roadbed, it has excellent hydraulic properties, adaptability, familiarity, etc.
It has been confirmed that the strength of soft subgrade soil is 5 times that of CBR, and that of good quality soil is 2.5 times that of CBR. Since it absorbs the load, it is considered that impact load does not need to be considered. In the following calculation, CBR was calculated at 260 (28 days immersion in water).

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] Tables 20 to 23 show examples in which the surface layer is asphalt concrete.

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]

In the above-mentioned examples, red mud, which is a residue when aluminum is produced from bauxite, is used as the Al-Fe-Ti-based oxide, but as the Al-Fe-Ti-based oxide, It is needless to say that it 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 landslide prevention and consolidation settlement prevention.

[0112]

As described above, since the soil stabilizer according to the present invention has lime added to the Al-Fe-Ti-based oxide,
By mixing this 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-Fe-
Since a soil stabilizer containing lime added to Ti-based oxide and natural soil or natural soil containing crushed stone are mixed, it can be used in place of conventional so-called roadbed crushed stone, and promotes the chemical action of treated soil. The early strength can be increased and the compaction effect can be enhanced.

Then, according to the paving method of the present invention,
Between the roadbed and the surface layer, replace Al-Fe-
Since the soil stabilizer with lime added to the Ti-based oxide and the roadbed mixed with natural soil or natural soil containing crushed stone were laid,
It is possible to prevent the softening of the subgrade soil and increase the strength of the subgrade roadbed as the load of the passing traffic vehicle increases.

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

Claims (12)

[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".)
A soil stabilizer characterized by the addition of lime. 2. The Al-Fe-Ti-based oxide comprises aluminum oxide 5% by weight or more, iron oxide 15% by weight or more, and titanium oxide 0.
The soil stabilizer according to claim 1, which is contained in a proportion of 5% by weight or more. 3. The ratio of Al-Fe-Ti oxide and lime is 30.
The soil stabilizer according to claim 1, wherein the soil stabilizer is 70: 70-30. 4. The soil stabilizer according to claim 1, wherein red mud, which is a residue when aluminum is produced from bauxite, is used as the Al-Fe-Ti-based oxide. 5. The soil stabilizer according to claim 1, wherein sewage sludge incineration ash is used as the Al-Fe-Ti-based oxide. 6. A paved roadbed material characterized by mixing a soil stabilizer obtained by adding lime to an Al-Fe-Ti-based oxide and natural soil or natural soil containing crushed stone. 7. The Al-Fe-Ti-based oxide in the soil stabilizer is 5% by weight or more of aluminum oxide, 15% by weight or more of iron oxide,
The paved roadbed material according to claim 6, which contains titanium oxide in an amount of 0.5% by weight or more. 8. The paved roadbed material according to claim 6, wherein the ratio of the Al—Fe—Ti oxide and the lime of the soil stabilizer is 30 to 70:70 to 30. 9. The paved roadbed material according to claim 4, wherein the ratio of the soil stabilizer and the natural soil or the mixture of natural soil and crushed stone is 3 to 10:97 to 90. 10. A soil stabilizing material obtained by adding lime to an Al-Fe-Ti-based 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. 11. The pavement method according to claim 10, wherein the surface layer is asphalt concrete. 12. The paving method according to claim 10, wherein the surface layer is cement concrete.