JPH02157301A - Stabilization for permeable surface layer for road bed - Google Patents

Abstract

PURPOSE:To maintain required strength and to have a good permeability by adding and mixing a solidifying agent to the existing soil of a bed, presetting and curing for a required time until it reaches to a specific uniaxial compression strength, rolling pressing and tamping. CONSTITUTION:According to the soil quality of viscous soil, Kanto loam layer, the suitable amount of cement type solidifying agent and the like is added and mixed to the existing soil of a bed. According to the hydration of the solidifying agent, soil particles are agglomerated. After the agglomeration is preset and cured for a required time until the uniaxial compression strength reaches to higher than 5kgf/cm<2>, rolling press and tamping are carried out by the use of a tire roller, macadam roller and the like. Required strength is thus generally maintained, and also permeability is improved through the gap of the formed agglomeration to enhance permeable coefficient.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is an improved construction method for the purpose of forming an improved ground having water permeability in a roadbed or roadbed surface stabilization method.

[Conventional technology]

In recent years, with the expansion of urban areas, factories, houses, parks, roads, etc. have been constructed on soft ground such as fields and wetlands that were previously unused. When constructing the above-mentioned facilities on soft ground, conventionally, a replacement method has been mainly used in which the soft ground is removed from the necessary parts of the facility and high-quality ground is replaced. However, recently, due to the lack of high-quality soil resources and the difficulty in securing a dumping site for the removed soft soil, cement, lime, or similar materials (hereinafter referred to as solidification materials) have been added and mixed. Increasingly, a so-called soft soil stabilization method is used, which improves the soft soil itself to desired properties.

When soft soil is stabilized using a solidification agent, the strength of the stabilized improved soil increases significantly as the amount of solidification added increases, making it possible to achieve an appropriate improvement depth even on soft soil that is difficult to walk on. By applying the amount of hardening agent added, it becomes possible for heavy vehicles to pass through. Furthermore, since the improvement is chemical using a solidification agent, soil that has been improved to a certain degree is difficult to soften again even in the presence of moisture.

These effects are due to the hydration of the solidifying agent: (1) the water content in the soil decreases, and (2) the pores in the soil are filled with the resulting hydrate.

(3) Reaction between soil particles and solidification material hydrate This is thought to be due to the following.

Therefore, improved soil has a denser structure overall than unimproved soil, and the hydraulic conductivity of improved soil tends to be lower than that of unimproved soil. are often used as water-stop walls.

Table 1 shows the relationship between soil quality and hydraulic conductivity, and Table 2 shows an example of the solidification addition rate, unconfined compressive strength, and hydraulic conductivity of sandy soil and clayey soil.

From Table 2, it can be seen that even sandy soil becomes substantially impermeable when the solidification agent addition rate is 3%.

Table 2 Relationship between solidifying agent addition rate, unconfined compressive strength, and hydraulic permeability coefficient (solidifying agent - cement-based solidifying agent) On the other hand, with the expansion of urban areas, the number of buildings increases and the rate of road paving increases. Because artificial objects cover the ground surface, precipitation such as rain and snow is treated as surface drainage and does not penetrate into the ground.

This surface water concentrates on roads and low-lying areas, causing urban flood damage. In addition, the supply of moisture underground has decreased, resulting in major impacts on the ecosystem, such as depletion of groundwater and poor plant growth. As a means to reduce these negative effects, permeable pavement has recently been adopted mainly in urban areas. Permeable pavement is a pavement made by using open-grained asphalt concrete to form a road surface with many voids, and the roadbed or subgrade using granulated crushed stone or crusher run to allow rainwater to quickly permeate beneath the road surface. Since no water stagnates on road surfaces, it prevents water splashing and hydroplaning, and is said to be effective in preserving urban vegetation such as street trees and park green areas.

[Problem to be solved by the invention] However, when the current soil is stabilized, rainwater that permeates from the pavement surface stays in the upper part of the stabilized layer, which has a low permeability coefficient, and water does not dissipate into the ground. Therefore, the water permeability function will be halved.

When the above-mentioned roadbed or roadbed stabilization method using a solidifying agent is applied to permeable pavement, the present invention provides a method that ensures necessary strength and forms a water-permeable roadbed or subgrade stabilization layer. The objective is to provide a construction method that meets this objective.

[Means for Solving the Problems J] The present invention involves adding and mixing a solidifying agent to the existing soil of the roadbed or roadbed, pre-curing for a certain period of time, and then rolling and compacting the soil. The soil particles are aggregated by hydration of the solidification agent, and after the aggregates have a certain strength, they are rolled and compacted.The constant strength is uniaxial compressive strength of 5 kg f
/ cr rr1'' or more. This ensures the necessary strength as a whole, while improving water permeability due to the voids in the generated aggregates.

Here, pre-curing refers to curing in air at room temperature and normal pressure without compaction for a certain period of time after mixing the solidifying material. Machines used for compaction and compaction include tire rollers, macadam rollers, etc. , machines and instruments similar to these can be used.

[Example] Next, a specific example of the treatment method of the present invention will be shown.

Table 3 shows the relationship between the curing time (preparation time), hydraulic conductivity, and CBR value after mixing cement-based solidifying material and compacting clay soil collected in Adachi Ward, Tokyo. In the same table, 0 hours of pre-preparation time indicates within 30 minutes immediately after mixing with solidification.Table 4 shows the relationship between age and unconfined compressive strength of specimens molded immediately after mixing with assimilation. .

Table 5 shows the relationship between the preheating time, permeability coefficient, and CBR value of Kanto loam collected in Omiya City, Saitama Prefecture, and Table 6 shows the relationship between the age and uniaxial compressive strength of the specimen molded immediately after assimilation mixing. This shows the relationship. The compaction method for producing the CBR specimens shown in Tables 3 and 5 is to compact the three layers by dropping each layer 67 times from a height of 45 cm using a 4.5 kg rammer. This is a method in which the specimen is molded using

The compaction energy (Ec) in this case is 1 from the following formula:
8.4x l O'm-kgf/rn'.

Table Preliminary Relationship between time and hydraulic conductivity (cohesive soil) Where: WR: Weight of rammer < kg) H: Falling height of rammer (m) Number of tamping times per N8 knee layer NL: Number of tamping cycles V: Tightening Volume of compacted specimen (rrr) Relationship between surface material age and unconfined compressive strength (cohesive soil) Relationship between surface preparation time and permeability coefficient (Kanto loam) Material age and unconfined compressive strength (Kanto loam) [Invention Effect J As shown in Tables 3 and 5, both clay soil and Kanto loam,
With a certain amount of pre-curing, the hydraulic conductivity increases significantly. In the case of clayey soil, the amount of solidification agent added is 50kg/rn'
In this case, the hydraulic conductivity is 10-5 cm/s after 24 hours of pre-curing.
Made to order, water permeability is possible. Addition amount IQQkg
/rrl', the pre-curing time was 6 hours and to-5
The hydraulic conductivity is on the order of cm/s.

Regarding the CBR value, it shows a tendency to decrease with pre-curing time, but the addition amount is 50 kg/rr? In the case of , the CBR value is 21.7% after 24 hours of pre-curing at which the hydraulic conductivity becomes 10-'' cm/s, and when the addition amount is 100 kg/rrr', the pre-curing at which the hydraulic conductivity becomes 10-5 cm/s. C in 6 hours
The BR value is 43.8%, which means it has sufficient supporting capacity.

In the case of Kanto loam as well, the hydraulic conductivity becomes on the order of lO''''50 m/S when the addition amount is 150 kg/rn' and the pre-curing time is 24 hours, and the CBR value is 2.0.4%. Similarly, if the addition amount is 200 kg/go, the pre-curing time is 6.
time, the CBR value is 52.3%.

As shown in Tables 4 and 6 for both clayey soil and Kanto loam,
From the relationship between material age and unconfined compressive strength, the unconfined compressive strength is 5 kg.
After pre-curing until the time when f/crn” or more is reached,
It can be seen that by compaction, the hydraulic conductivity becomes lo-5 cm/s. This phenomenon is caused by the fact that when the soil that has become aggregates after assimilation and mixing has a strength of about 5 kgf/crn', compaction is performed while maintaining the same village shape to some extent even by rolling compaction. It is thought that water permeates through the gaps.

Claims (1)

[Claims] 1 In the roadbed or roadbed stabilization method, the surface soil of the roadbed or roadbed is mixed with a solidification material, and the unconfined compressive strength is 5k.
A method for stabilizing the permeable surface layer of a roadbed or roadbed, which is characterized by performing pre-curing until gf/cm^2 or more, and then compacting it by compaction.