JPH0665902A - Road pavement method and pavement structure - Google Patents

Abstract

(57) [Abstract] [Purpose] Instead of so-called crushed roadbed stones on paved roads, a paved roadbed material that has been physically and chemically stabilized is used to prevent softening of subgrade soil and the amount of surface deflection (subsidence). Was designed to have a thickness of 0.3 mm or less, which is said to have elastic body behavior, and the asphalt intermediate layer was unnecessary. [Composition] Between the subgrade and cement concrete or compacted concrete that becomes the surface layer, replace the conventional paved roadbed,
Laying roadbed mixed with crushed stone, natural soil and soil stabilizer,
The thickness of the roadbed was designed so that the maximum strain of the pavement surface was 0.3 mm or less by setting the strength of the roadbed material to 150% for 4 days immersion CBR and 260% for 28 days immersion CBR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is to add natural soil to crushed stones instead of crushed stones or soil cement for paved roads whose surface layer is cement concrete or compacted concrete. The soil material stabilizer is added and the physicochemically stabilized pavement base material is used to prevent the softening of the roadbed soil and the strength of the roadbed material to be kept in the water for 4 days.
The present invention relates to a pavement method capable of increasing the strength of a roadbed and a roadbed according to an increase in the load of a passing traffic vehicle such that the R150% and the 28-day immersion CBR are 260% or more, and further, the asphalt intermediate layer is unnecessary.

Further, in a cement concrete pavement structure adopting such a pavement construction method, the thickness of the roadbed is adjusted so that the amount of surface deflection (subsidence amount) is 0.3 mm or less, which is said to have elastic body behavior. The present invention relates to a pavement structure designed to be designed.

[0003]

2. Description of the Related Art Conventionally, the design and construction of paved roads in Japan have been adapted to the American geology by the CBR method (developed about 60 years ago and largely revised 40 years later based on the results of AASHO road tests). The design and construction procedures determined by the results of the above are carried out by the asphalt pavement outline and cement concrete pavement outline established so as to conform to the environmental conditions of Japan.

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 research, a field test was conducted to consider the maximum profit of 10 ton wheel load (2
Roadbeds and pavements for 5 ton vehicles are being constructed using physical (geotechnical) methods.

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 pavement pavement structure has a tendency to prevent road surface wear due to traffic loads due to various crushed stones of plastic and ascon. To prevent
It is intended to prevent the pavement from being disturbed and destroyed by rubbing the pavement, and to prevent fatigue and weakening of the roadbed. Moreover, the size of the paw paw 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 elastic bending. 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.

[0008] By the way, according to a follow-up survey by the Highway Public Corporation, a road body of 100 cm (which is sufficiently compacted with a good soil of CBR 2.5% or more) is provided at the lower part thereof in order to sufficiently compact the roadbed soil. , A road with a subgrade, a subgrade, and a surface layer of the strength necessary for the service traffic load on the upper part
The age has been reduced to 0.5 ~ since the time of construction.
It became 0.8 mm, and after that, it became large again with a minimum of 0.5 mm as a boundary, causing ruts and being destroyed. This is different from the case of the general structure, which is obtained from the result of the CBR method and the AASHO road test.
This is because the structure of 5 mm is too large for the current traffic volume and traffic load, and leads to fatigue and breakage of the pavement.

In order to prevent the destruction due to this fatigue, the pavement of the bend has an elastic behavior, that is, 1.0 mm (1 mm, which is a minute strain of 10 ^-3 , which is said to have self-healing property).
In order to secure 0.7mm as the stable strain value of the subgrade soil, in the case of the erected structure of soil, the safety factor 1.6 times that Tertuagy says is 0.7mm. The theoretical calculation of is as follows. L traffic (P = 2t) ・ ・ ・ 970kg / cm ² = CB
R10% A traffic (P = 3t) ・ ・ ・ 1370kg / cm ² = CB
R14% B traffic (P = 5t) ・ ・ ・ 2000kg / cm ² = CB
R20% C traffic (P = 8t) ・ ・ ・ 2730kg / cm ² = CB
R28% D traffic (P = 12t) ・ ・ ・ 3430kg / cm ² = CB
R35%

The stable strain (subsidence amount) at which the pavement (surface layer, base layer and roadbed) is within the elastic behavior limit is 0.3 m when the safety factor is 3.5 times as in the case of general structures.
It must be m or less. That is, if the subsidence amount of the pavement surface is set to 0.3 mm or less, the pavement body as a whole has a structure that maintains self-healing strain without residual strain.

By the way, as mentioned above, the pavement component is
We expect roller compaction based on the subgrade and compaction effect due to running load. However, the crushed stone roadbed has large voids and is easily penetrated by water, so that the water content ratio is increased, and conversely, the running load causes fatigue to cause rutting due to plastic deformation. This indicates that the pavement member needs to be improved.

In particular, when the surface layer is cement concrete pavement, the running load and the self-weight of the surface layer are not negligible, and strengthening the roadbed becomes a more important issue than when the surface layer is asphalt concrete. Since the asphalt concrete acts as an elastic body, the asphalt concrete portion can also be considered as an elastic body when the entire pavement body has a twisted road structure.
However, since cement concrete is a rigid body, cement concrete cannot be treated the same as asphalt concrete when considering the amount of deflection. Therefore, it is necessary to secure the required amount of deflection according to the strength of the roadbed.

Therefore, in order to prevent the fatigue damage of the pavement, the crushed stone used for the pavement becomes a roadbed material having a great strength (elastic coefficient) with a twisting property, and the maximum road surface strain of the pavement is the elasticity considering the safety factor. 0.3m which is the physical behavior limit
It is necessary to reinforce the subbase so that it is less than m. In addition to reinforcing the roadbed to be strong, it is possible to use roadbed material that is adaptable, self-healing, hydraulic, etc. that can prevent the softening of the roadbed soil and that is well compatible with the roadbed soil. Will be needed.

By the way, when soil cement is used as a roadbed material, it cannot be used depending on the soil quality, and the strength changes depending on the mixing ratio, the water content ratio, the compaction degree, and the setting time of the cement paste. ,
It is difficult to ensure uniformity. In addition, it is unfamiliar because it has different properties from the roadbed. Although the strength can be increased by increasing the amount of cement, the strain at the time of fracture becomes small and the resistance to adapt to the bending stress due to the abrupt change of the load cannot be obtained.

Therefore, the present applicant invented a paving roadbed material in which crushed stone, natural soil and a soil stabilizer were mixed and applied for a patent (see Japanese Patent Application No. 3-106559), but this paving roadbed material has an asphalt surface layer. It was found that the surface layer is effective for rigid pavement such as cement concrete and compacted concrete as well as concrete. Since the concrete slab has rigidity and resists bending stress due to wheel load, the concrete thickness is determined so that the resistance force is within the allowable stress, and the roadbed is reinforced to correspond to this thickness. Therefore, the strength of the subgrade soil should be maintained.

That is, the thickness of cement concrete required for wheel load is determined by the pavement guideline. In addition, the CBR value of the roadbed is inevitably determined by the ground where pavement work is performed. Therefore, it suffices to maintain the required strength of the roadbed material that connects the surface layer to the roadbed.

When the surface layer is made of cement concrete, "joint" is necessary because the cement concrete expands and contracts due to the temperature difference between day and night. However, rainwater enters from the joints and weakens the roadbed and roadbed. Therefore, when crushed stone is used for the roadbed, it is stated in the paving outline that an asphalt intermediate layer should be provided to prevent softening.

However, the paved roadbed material mixed with the soil stabilizer of the above patent application is not weakened by water, and the softening of the roadbed soil is prevented, so that the asphalt intermediate layer is not required. Therefore, if such a paved roadbed material is used, it is possible to easily perform road paving work in which the surface layer is cement concrete paving.

That is, in the pavement with cement concrete as the surface layer, unlike the material dynamics by compaction of a plastic body such as crushed stone, the cement concrete board and the ground are integrated to support the load. However, the expansion coefficient is different between cement concrete board and roadbed, and they behave differently depending on the temperature change, the own weight of the cement concrete board is added to the roadbed together with the wheel load, or it is provided to prevent the expansion and contraction of the cement concrete board. There is a problem that water enters from the joint and promotes fatigue of the roadbed, and it is necessary to reinforce the roadbed that can cope with these problems.

[0020]

Therefore, a method for paving a road according to the present invention is to provide a crushed stone, natural soil and Laying a roadbed mixed with a soil stabilizer so that the strength of the roadbed is 150% CBR for 4 days and 260% CBR for 28 days, which makes the pavement elastic to the passing traffic load. It is designed to be tawami (self-healing).

The road pavement structure according to the present invention is
The maximum strain of the pavement surface is 0. by laying a roadbed in which crushed stone, natural soil and a soil stabilizer are mixed in place of the conventional paved roadbed between the subgrade and the cement concrete or compacted concrete to be the surface layer. The thickness of the roadbed is designed to be 3 mm or less so that the pavement body has a structure that maintains the amount of deflection within the elastic behavior limit.

[0022]

[Function] It is well known that soil is stabilized by adding lime to acid soil. However, addition of lime alone causes the lime to flow out from the soil because Japan is wet and wet, and the soil of acid soil repeats weakening again.

Therefore, when iron oxide fine powder is added to this, the acid soil and humus that cannot be hardened by lime are hardened, and the chemical action of lime on clay and humus is promoted. Then, it prevents the action of leaching of lime by substitution with other exchangeable ions, thereby imparting durability to stable soil.

This means that Japanese soil has been used in Japan for a long time, but it uses red soil (laterized soil) containing a large amount of iron oxide, and the soil lime method is It has also been proved by its recent successful use in Soviet laterite soil and road and airfield construction in the United States and Southeast Asia.

The soil stabilizer used in the present invention acts as described above, and is a mixture of iron oxide fine powder of 1/1000 mm or less and quick lime, slaked lime and limestone powder. In the following description, this soil stabilizer may be referred to as "Fe lime". Also,
The roadbed treated with the soil stabilizer of the present invention may be referred to as "stabilized roadbed" or "Fe-treated roadbed".

Since the reaction rates of quick lime, slaked lime, and limestone powder are slow in this order, the effect can be maintained for a long time by properly mixing these. The mixing ratio of quicklime powder: slaked lime: limestone powder is 1: 2: 1 by weight.
Based on the soil test results, 4 days immersion CBR1
To secure 50% and 28 days immersion CBR 260%,
The mixing ratio is determined by the quality of the soil and crushed stone at that time.

When water is added to quicklime, heat of 250 ° C. or higher is generated, but in the case of the limestone powder used, the heat is about 150 ° C, and there is no danger in the case of a small amount. The use of quicklime raises the reaction temperature, so that the chemical reaction can be promoted and the CBR value can be increased. Therefore, quick lime is used to keep the treated soil warm when it is cold and to prevent the effect from flowing out when there is a lot of rain.

When the propagation distribution of stress in the crushed stone layer of the roadbed is analyzed, the load pressure on the road surface acts on the crushed stone particles in a horizontal stress, a shear stress and a vertical stress. And the crushed stone grains are
Correspondence depends on the adhesive force and friction angle of each particle.

A crushed stone layer containing soil mixed with physicochemically stabilized crushed stone and crushed stone has a large resistance stress, adhesive force, internal friction angle, etc., and is subjected to pressure from rolling compaction and carbon dioxide contained in subgrade soil. Gas and the like effectively promote the chemical reaction.
That is, the weather and ground environment conditions can be effectively utilized. Therefore, the durability increases with the use of the road, and the amount of deflection decreases accordingly, which prevents the fatigue of the pavement.

When a soil stabilizer is mixed with a mixture of crushed stone and natural soil and subjected to a chemical treatment, a chemical reaction is promoted when subjected to a physical action such as an increase in load or a temperature change, and CBR. The value will increase. That is, the chemical action is accelerated by the physical action of compaction caused by the passage of vehicles on the road, rather than the action of water cement that hardens by itself like soil cement, and the CBR value increases over time. Will rise.

When a crushed stone bed layer mixed with soil that has been physically and chemically treated with a soil stabilizer is applied to a subgrade with a CBR of 3% or more, which is not subject to the replacement method in the design method based on the pavement outline, it occurs in the subgrade. The generated carbon dioxide gas rises along with water due to the capillarity of the upper treatment layer, and this carbonated water promotes the chemical reaction of the treated roadbed, increases its strength, and stabilizes the subgrade soil.

If crushed stone and natural soil were not mixed, but only crushed stone and soil stabilizer were mixed, the crushed stone and crusher run alone would cause unevenness and the load would not act evenly on the roadbed, and even if compacted. The voids are large, water can easily enter, the organic substances contained in the roadbed are corroded, and carbon dioxide gas generated therewith causes both the roadbed and the roadbed to be weathered and weakened.

If the crushed stone and the natural soil are not mixed but only the natural soil and the soil stabilizer are mixed, the CBR is 100% at maximum.
Not only that, but it is impossible for the pavement to have an elastic behavior of the pavement, that is, a minute strain of 0.3 mm or less, which is said to be self-healing.

The mixing ratio of crushed stone and soil must be adjusted by the particle size of crushed stone or soil so that the aggregate mesh of crushed stone is used as a skeleton and the gap is filled with sufficiently compacted soil. However, in practice, due to the material separation at the time of laying and spreading, the lack of load bearing capacity of the roadbed that is the rolling compaction base, sufficient roller compaction is not possible, and the void volume of the crushed stone to be filled, It has a fate that the amounts of soil to be filled do not match.

If there are too many crushed stones, the compaction load will be insufficiently compacted for the soil filled in the gaps due to the compaction load being supported by the aggregate meshing, water will easily penetrate, and the water content ratio of the soil will increase.
It is extremely dangerous because it acts like a lubricating oil and loses its strength against the skeleton formed by the interlocking of aggregates of crushed stone.

When the amount of soil is too large, crushed stones are scattered in the soil and the aggregate mesh is lost.
Strength is reduced to the same as soil shear. However, in this state, the soil compaction is accelerated by the concentrated load of crushed stone.

Therefore, the ideal amount of soil should be slightly larger than the void volume of compacted crushed stone,
Approximate mixing ratio is volume ratio, crushed stone: soil 30: 70-5
The range is 0:50. It is desirable to use crushed stones according to JIS and natural soils with a solid skeleton.

Any method can be used for manufacturing road roadbed materials by mixing crushed stone, natural soil, and a soil stabilizer, as long as they can be mixed, but the water content is such that compaction is possible. Good. That is, it is sufficient that the water content of the soil does not hinder the substitution of cations.

By the way, the concrete slab has rigidity,
The concrete thickness is determined by the pavement rope so that the bending stress due to wheel load is resisted and the resisting force is within the allowable stress. On the other hand, the strength of the subgrade soil is also determined by the ground at the pavement construction site. Therefore, by reinforcing the roadbed, the strength of the pavement is made to correspond to the thickness of the concrete, and the strength of the roadbed soil is maintained.

If the surface layer is cement concrete pavement, it will only wear about 0.5 mm in 3 years, and it will take about 30 years to wear 5 mm. Therefore, by applying cement concrete, which is an elastic body, to the surface layer, the roadbed is a roadbed mixed with crushed stone, natural soil and a soil stabilizer, resulting in a more durable pavement,
Maintenance and repair costs can be greatly reduced.

[0041]

EXAMPLE FIG. 1 is a sectional view of an example of a pavement structure according to the present invention according to each roadbed CBR value in each road section. Further, FIG. 2 shows a design cross-sectional view shown in the 1984 cement concrete pavement summary using the conventional crushed stone roadbed corresponding to the above embodiment.

Tables 1 and 2 show the results of checking the amount of deflection on the road surface of the pavement structure road shown in FIG. Table 1 shows the case where the surface layer is compacted concrete, and Table 2 shows the case where the surface layer is cement concrete.

The stabilized base course materials used in the calculations in Tables 1 and 2 were 60 parts of natural soil and 40 parts of crushed stone, and 4 parts of slaked lime.
And 1 part of iron oxide fine powder are mixed.

[0044]

[Table 1]

[0045]

[Table 2]

On the other hand, Tables 3 and 4 show the results of calculating the amount of deflection on the road surface of the pavement structure shown in FIG. Table 3 shows the case where the surface layer is compacted concrete, and Table 4 shows the case where the surface layer is cement concrete.

[0047]

[Table 3]

[0048]

[Table 4]

As is clear from the above examples, in the case of the pavement structure of the present invention, when the surface layer is cement concrete, the amount of deflection of the pavement surface is 0.3 mm or less. When the surface layer is compacted concrete,
Since it is assumed that the road will be opened within a short period of time after paving, the elastic modulus of the Fe lime treatment layer is calculated as water immersion for 4 days, so the amount of deflection exceeds 0.3 mm in Table 1, but This decreases with the passage of days.

On the other hand, in the case of the conventional pavement structure, the amount of deflection on the pavement surface is 0.
It turns out that it becomes larger than 3 mm.

As the lime used in the present invention, quick lime powder, slaked lime, limestone powder, etc. may be used so that the required strength can be maintained and secured depending on the weathering condition of the soil and crushed stone to be used.

As the crushed stone, not only good quality crushed stone but also weathered crushed stone of waste material can be reused.
This is because by carrying out the treatment as in the present invention, the hardening of the weathered clay content is strengthened by the pressure, heat and the period of applying it.

[0053]

As described above, according to the pavement method for a road according to the present invention, crushed stone is used between the subgrade and the cement concrete or compacted concrete that becomes the surface layer instead of the conventionally used paved roadbed. Laying roadbed mixed with natural soil and soil stabilizer, the strength of the roadbed is 4 days water immersion CBR150%, 28
The CBR should be 260% or more in the daily immersion, so that the pavement can be elastically bent (self-healing) against the passing traffic load, and sufficient strength can be secured without disturbing the roadbed. The surface layer can be concrete pavement that is resistant to abrasion.

According to the pavement structure for a road according to the present invention, crushed stone, natural soil, and a soil stabilizer are provided between the subgrade and the cement concrete or compacted concrete to be the surface layer in place of the conventional paved roadbed. Laying mixed roadbed,
The thickness of the roadbed was designed so that the maximum strain on the pavement surface would be 0.3 mm or less, and the pavement structure was designed to maintain the amount of deflection within the elastic behavior limit, so there is no residual strain. It becomes possible to maintain the deflection against the applied load.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment according to each roadbed CBR value in each road section of a pavement structure according to the present invention.

FIG. 2 is a design cross-sectional view shown in a 1984 cement concrete pavement summary using a conventional crushed stone roadbed.

Claims (5)

[Claims] 1. A subgrade, in which crushed stone, natural soil and a soil stabilizer are mixed, is laid between the subgrade and cement concrete or compacted concrete as the surface layer, in place of the conventional paved subgrade, and the strength of the subgrade material is increased. The pavement method for roads is characterized in that the CBR is 150% for 4 days and the CBR is 260% for 28 days. 2. The pavement method for a road according to claim 1, wherein the soil stabilizer is a mixture of iron oxide fine powder of 1/1000 mm or less, and quick lime, slaked lime and limestone powder. 3. A pavement is prepared by laying a roadbed containing crushed stone, natural soil and a soil stabilizer in place of the conventional paved roadbed between the roadbed and the surface concrete or compacted concrete. A road pavement structure characterized in that the thickness of the roadbed is designed so that the maximum strain is 0.3 mm or less. 4. A subgrade, in which crushed stone, natural soil, and a soil stabilizer are mixed, is laid between the subgrade and cement concrete or compacted concrete to be the surface layer, instead of the conventional paved subgrade, and the subgrade material is strong. The thickness of the roadbed was designed so that the maximum strain of the pavement surface would be 0.3 mm or less, with 150% CBR for 4 days and 260% CBR for 28 days. Pavement structure. 5. The road pavement structure according to claim 3 or 4, wherein the soil stabilizer is a mixture of iron oxide fine powder of 1/1000 mm or less and quick lime, slaked lime and limestone powder.