JPH03446B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for improving soil water permeability. More specifically, by using an inorganic solidifying agent and a neutral or basic cationic asphalt emulsion in combination, impervious or poorly permeable soil is solidified into aggregates, which is then crushed by a machine or the like. This invention relates to a soil improvement method for regenerating soil with good water permeability by granulating it. <Prior Art> As soil conditioners for improving soil drainage and preventing softening due to precipitation, etc., there have been conventionally used anionic emulsions, acidic cationic emulsions, and the like. However, anionic emulsions have a negatively charged soil particle surface and therefore have a low affinity with soil particles and a weak binding force. Furthermore, acidic cationic emulsions have the property of weakening the action of alkaline solidifying agents such as lime. For this reason, both of these emulsions have restrictions on the type of soil that can be treated, and their effects are particularly insufficient on clay soils, so the best solution is to replace them with sandy soils that have good water permeability. The current situation is that there is. As a result, work efficiency was poor and soil improvement costs were high. <Problems to be solved by the invention> Types of water that permeates into the soil include free water (gravity water) flowing through the gaps between soil particles, capillary water caused by adhesion and surface tension in small gaps in the soil, and adsorbed water, which increases the stickiness of soil by ionically bonding with soil particles. In order to obtain soil with good permeability, it is necessary to control this water chemically or soil mechanics. In view of the above-mentioned circumstances, the present invention has been developed by using an inorganic solidifying agent and a neutral or basic cationic asphalt emulsion to improve water-impermeable or poorly permeable soil in a short time. The purpose of the present invention is to provide a method for improving the soil quality by mechanically crushing the solidified soil to a certain particle size after solidifying the soil to improve water permeability. <Means for solving the problem> By mechanically crushing the soil that has solidified into aggregates by using an inorganic solidifying agent such as lime or cement together with a neutral or basic cationic asphalt emulsion. , by increasing the compositional pores of the soil to promote the flow of free water, which is the most important factor governing water permeability, and by increasing the hydrophobicity of soil particles with the emulsion, capillary water and adsorbed water are reduced. As a standard method, the inorganic solidifying agent used is a mixture of 1 part lime and 1 to 2 parts fly ash. Slaked lime (Ca(OH) ² ) is often used as lime, but quicklime (CaO) is used when the treated soil has a high moisture content, such as clay soil. Also, some of the lime may be replaced with cement. Fly ash acts as an adjuvant for lime and has the property of combining with slaked lime or quicklime to form a stable insoluble substance, and is used in thermal power generation using materials such as dust obtained during combustion of pulverized coal. By mixing these lime and flyash with an inorganic solidifying agent, it is possible to form a permanent soil solidified product. When compacting soil, a neutral or basic cationic asphalt emulsion is used in addition to the inorganic compacting agent. Generally commercially available acidic cationic emulsions have their pH adjusted by adding hydrochloric acid, acetic acid, etc. to the emulsion, so when mixed with basic lime or cement, their neutralizing effect will reduce the emulsion. The charge balance suddenly collapses and the emulsion grains are destroyed, making it impossible to mix uniformly. For this reason, a neutral or basic cationic asphalt emulsion is used, which has good affinity with basic inorganic substances such as lime and cement, and can be mixed with soils having a large plasticity index. However, if too much emulsion is added, the liquefaction of the soil will increase and its stability will be reduced, so only the necessary amount should be added. Particularly for clayey soils with high water content, the addition of emulsions creates a lubricating effect between soil particles, resulting in instability and a tendency to cause plastic flow. Therefore, the standard addition amount is several percent or less. Next, the soil that has been solidified by the above method is compacted and cured so that the unconfined compressive strength is approximately 6 kg/cm2 or ^more , and then the coarse particles (φ5 mm or more) are ) is crushed to approximately 50% or more and the maximum particle size is approximately 50mm or less, and then rolled again to finish. In order to crush particles to a predetermined particle size in a short time, it is necessary to select a crushing mixer with good crushing performance, and generally a pulvertizer or deep stabilizer for roadbed mixing is used. <Action> Ca ions contained in lime, etc. have the ability to absorb H,
It has the function of replacing Na, K ions, etc. and increasing the interparticle adsorption force, and it also has the function of replacing Na, K ions, etc. with complex compounds (CaSi ₂ O ₃ /
It has the effect of forming Al ₂ O ₃ nH ₂ O) and solidifying the soil. In addition, fly ash has the function of reinforcing the action of lime and the like as an auxiliary agent. These actions make it possible to create stronger soil aggregates. Neutral or basic cationic asphalt emulsions have good affinity with basic inorganic substances such as lime and cement, so they can be mixed even with soils with a high plasticity index, and can be mixed with soils as specified in JISK-2207. It can also meet the specifications of emulsion MK-3.
Therefore, the asphalt emulsion has a small particle size and works well with clay soil having a large liquidity limit, and can form a composite with soil particles, thereby imparting a certain chemical structure to the soil. That is, the asphalt molecules in the asphalt emulsion have the function of making the soil particles surface chemically hydrophobic by forming a film around the soil particles. These characteristics of asphalt particles compensate for the shortcomings of conventional inorganic solidifying agents, which were thought to be susceptible to fine particles due to freezing and thawing, and provide long-term retention of good water permeability to treated soil. can do. As mentioned above, soil that has been chemically agglomerated and made hydrophobic by using an inorganic solidifying agent and a neutral or basic asphalt emulsion is processed by a crushing mixer. Furthermore, it is mechanically crushed to increase its coarse particle ratio. As a result of these, soil having permeability that is chemically and soil-mechanically stable can be obtained. <Examples> Examples of the present invention will be described below. Example 1 For CH soil (impermeable soil) according to the unified classification method, slaked lime, fly ash, and asphalt emulsion shown in Table 3 were mixed at the proportions shown in Table 1, and treated and solidified to a depth of 40 cm. administer. First, predetermined amounts of slaked lime and Aria Ash are sprinkled on the CH soil and mixed, and then asphalt emulsion is mixed. Komatsu road-type crushing mixer is used for mixing.
Using GS-360 Road Stabilizer (manufactured by Komatsu Ltd.), a soil solidified body having an unconfined compressive strength of 7.5 Kg/cm ² (curing time: 5 days) was obtained. Next, by running the crushing mixer once at a speed of 3 m/min, the soil solidification is crushed and granulated, with a coarse particle size ratio of 60
%, and a crushed body with a maximum particle size of 40 mm was obtained. This was compressed several times with a tire roller (load of 10 tons or more) to compact it a little, and then sand was sprinkled at a rate of 0.006 m ³ /m ² to finish it. The water permeability effect test of Example 1 was conducted based on the variable water level test method according to JIS A1218, and the results are shown in Table 4. Example 2

[Table] For CL soil (poorly permeable soil) according to the unified classification method, asphalt emulsion containing slaked lime, cement, and fly ash shown in Table 4 was mixed in the proportions shown in Table 2, and treated at a depth of 40 cm. Apply solidification. First, a predetermined proportion of the inorganic substance is sprinkled and mixed on the CL soil at once, and then the asphalt emulsion is mixed. During compaction, the mixed soil is spread out to dry out some of the moisture so that the optimum moisture content is achieved. For mixing, a Sakai type regenerating roadbed machine PM170 (manufactured by Sakai Seisakusho Co., Ltd.) was used to obtain a solidified soil having an unconfined compressive strength of 10 Kg/cm ² (curing time: 3 days). For crushing, the roadbed machine was run twice at a speed of 3 m/min to obtain a crushed body with a coarse grain size ratio of 52% and a maximum grain ratio of 50 mm. This was compressed several times with a tire roller (load of 10 tons or more), and then finished by scattering decorative sand at a rate of 0.010 m ³ /m ² .

【table】

[Table] The water permeability effect test of Example 2 was carried out in Example 1 above.
The results are shown in Table 4. Through the above two rows of Examples, it was confirmed that impermeable or poorly permeable soils could be improved to soils with approximately 100 times higher water permeability, and that these soils could be utilized as permeable soils. <Effects of the invention> Easily permeates impermeable or poorly permeable soil.

【table】

[Table] Can be used to improve water-based soil, and is effective in improving the permeability of athletic grounds, clay courts, structure foundations, subgrade soil, etc., and is also effective when using buried permeable pipes. . It is more economical than the conventional excavated soil replacement method and can shorten the construction period. It can also be applied to prevent freezing in cold regions and as a method for improving agricultural soil, and its uses are diverse.

Claims (1)

[Claims] 1. Mixing an inorganic solidifying agent and a neutral or basic cationic asphalt emulsion into impermeable or poorly permeable soil, solidifying the soil into aggregates, and then crushing and granulating the solidified soil. A soil water permeability improvement method characterized by improving the water permeability of soil.