JP2006150341A - Method for improving/solidifying soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for improving/solidifying soil, which is effective when taking measures to deal with soil contamination, soft ground and elution of a toxic substance from concrete. <P>SOLUTION: A liquid hardening agent is prepared by blending sodium salt based on sodium carbonate and sodium chloride, ammonium salt based on ammonium chloride principal component and a cobalt compound in a liquid of ≥70 wt% so that the chlorine ion content and the sodium ion content are respectively 1-10 wt%, the cobalt content is 0.01-0.1 wt%, the evaporation residue is 10-20 wt% and the calcium ion content is ≤0.1 wt%. A soil solidifying material is obtained by mixing the prepared liquid hardening agent in cement. Soil is improved/solidified by forcibly sending the obtained soil solidifying material into soil and agitating them. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a soil improvement solidification method that can be used for improvement of soft ground and prevention of leaching of harmful substances from contaminated soil.

  Industrial waste and general waste, etc., and incineration ash and fly ash incinerated with this waste include arsenic (As), cadmium (Cd), chromium (Cr) such as hexavalent chromium, copper (Cu) In addition, heavy metals such as nickel (Ni), lead (Pb), mercury (Hg), and a very toxic hormone-inhibiting chemical represented by polychlorinated benzo-para-dioxin are contained. For this reason, at present, as a waste countermeasure, the above-mentioned waste and the like are mixed with cement and solidified and disposed of in landfills.

  In recent years, it has been recognized that soil is contaminated with toxic substances such as heavy metals and hormone-inhibiting chemicals, which has become a social problem. For this reason, as a countermeasure against soil contamination, contaminated soil is solidified with cement or the like to contain harmful substances, thereby preventing elution and diffusion of harmful substances.

Furthermore, recently, it has been recognized that cement itself contains heavy metals such as hexavalent chromium and lead due to its raw materials. This not only means that cement cannot be used for the above-mentioned waste countermeasures and soil pollution countermeasures, but also is made of concrete made by mixing aggregates such as gravel, which are widely used at construction sites, and cement. If toxic substances such as hexavalent chromium are eluted from the buildings and foundations, it means that the environment will be seriously damaged, and early concrete measures are desired.
Also, in the ground mixed treatment method where cement-based improvement material is injected into soft ground or loose sand layer and agitated with a stirring blade to make an improved body, harmful substances such as hexavalent chromium contained in the cement itself are eluted. There is a concern that there is a risk, and some countermeasures are needed.

  With respect to such problems, Patent Document 1 proposes a waste treatment material obtained by adding a reducing metal such as iron or aluminum to cements. This waste treatment material can stabilize harmful metals in the cement solidified body by reducing harmful metal ions contained in the fly ash or cement itself with a reducing metal.

JP-A-7-185499 JP 2002-241166 A Japanese Patent No. 3005617 JP 2004-209372 A JP 2004-105900 A Japanese Patent Laid-Open No. 10-272435 JP 63-284310 A Japanese Patent Publication No. 6-99042

  An object of the present invention is to provide a soil improvement and solidification method effective for waste countermeasures, soft ground countermeasures, soil contamination countermeasures, and concrete countermeasures.

  The invention according to claim 1 of the present invention is a soil improvement solidification method comprising: a sodium salt containing sodium carbonate and sodium chloride as main components; an ammonium salt containing ammonium chloride as a main component; and a cobalt compound. Blended in a liquid of more than wt%, adjusting the chloride ion content and sodium ion content to 1-10 wt% respectively, and adjusting the cobalt content to 0.01-0.1 wt% and evaporating A liquid hardening agent in which the residue is set in the range of 10 to 20% by weight and the calcium ion content is set in the range of 0.1% by weight or less is mixed with cement to make a soil-solidifying material. The solidifying material is pumped to the soil and stirred to improve and solidify the soil.

  According to the soil improvement solidification method of the present invention, a liquid hardening agent exhibiting alkalinity, cement and water are mixed to produce a soil solidification material, and the soil solidification material is pumped into the soil and stirred to improve the solidification. In this case, the soil solidified with sodium carbonate and sodium chloride as sodium salts contained in the liquid curing agent is kept alkaline, thereby maintaining the mechanical strength of the soil, and Sodium and sodium chloride accelerates the hydration reaction between cement and water, and the hydrate can reliably prevent the elution and diffusion of heavy metals such as hexavalent chromium and hormone-inhibiting chemicals. effective.

  Moreover, according to the soil improvement solidification method of the present invention, by setting the evaporation residue of the liquid curing agent in the range of 10 to 20% by weight, the liquid curing agent can contain 70% by weight or more of liquid, When mixing solid hardener, cement, and water to produce a solidified material, the amount of water added can be reduced, the strength of the improved solidified soil can be increased, and the efficiency of the mixing work can be increased. There is an effect that can be achieved.

  Furthermore, according to the soil improvement solidification method of the present invention, the mechanical strength of the improved solidified soil is increased by adjusting the liquid hardener cobalt to 0.01 to 0.1% by weight, and heavy metals and There is an effect that toxic substances can be retained and elution can be prevented.

  Moreover, according to the soil improvement solidification method of this invention, by setting the calcium ion of a liquid hardening | curing agent to the range of 0.1 weight% or less, it is by the calcium carbonate produced | generated by reaction with sodium carbonate as a sodium salt. There is an effect that the adverse effect on the properties of the improved solidified soil can be minimized.

Embodiment 1 FIG.
The liquid hardening agent used for the soil improvement solidification method according to Embodiment 1 of the present invention is a sodium salt mainly composed of sodium carbonate and sodium chloride, an ammonium salt mainly composed of ammonium chloride, and a cobalt compound. Blended in a liquid of more than wt%, adjusting the chloride ion content and sodium ion content to 1-10 wt% respectively, and adjusting the cobalt content to 0.01-0.1 wt% and evaporating The residue is set in the range of 10 to 20% by weight, and the calcium ion content is set in the range of 0.1% by weight or less.

  The liquid contained in the liquid curing agent is usually water. For example, any liquid such as tap water, pure water, distilled water, spring water, or well water can be used as long as it maintains the alkalinity of the liquid curing agent. It can be used. The reason why the liquid content in the liquid curing agent is set to 70% by weight is that when it is less than 70% by weight, the fluidity of the liquid curing agent is reduced, and the addition of the liquid curing agent to cement and water described below. This is because there are inconveniences that sometimes reduce work efficiency.

  The main components of the sodium salt contained in this liquid curing agent are sodium carbonate and sodium chloride. Sodium carbonate is produced by mixing a liquid hardener with cement to produce a soil-solidifying material. When the soil-solidifying material described below is used to improve and solidify soil, the alkalinity of the improved and solidified soil is promoted by neutralization. Sodium chloride is a component added mainly for the purpose of preventing a decrease in mechanical strength. Sodium chloride is used to produce a soil-solidifying material by mixing a liquid hardener with cement. In addition to sodium carbonate, it is a component added for the purpose of promoting cement hydration. Therefore, by promoting cement hydration, it is possible to reliably prevent toxic substances such as heavy metals such as hexavalent chromium and hormone-inhibiting chemical substances from being eluted and diffused from the improved solidified soil described later.

  The reason for adjusting the chloride ion content to 1 to 10% by weight is that, if it is less than 1% by weight, the effect of adding chloride ions supplied by sodium chloride or the like is not exhibited in the improved solidified soil described below. This is because when the amount exceeds 10% by weight, chloride ions become excessive, and the effect of addition to the improved solidified soil described below reaches its peak. Therefore, the content of chlorine ions is based on the assumption that the liquid hardener is added to the improved solidified soil described below, and the addition effect of the liquid hardener in the improved solidified soil is taken into account. For example, when the addition rate of the liquid curing agent in the improved solidified soil described later is relatively high, the chloride ion content in the liquid curing agent is set to the lower limit side of the above range. On the contrary, when the addition rate of the liquid curing agent in the improved solidified soil described later is relatively low, it is desirable to set the chloride ion content in the liquid curing agent to the upper limit side of the above range.

  The reason why the content of sodium ions is adjusted to 1 to 10% by weight is that in the case of less than 1% by weight, the effect of adding sodium ions supplied by sodium chloride, sodium carbonate, etc. is improved in the solidified soil described later. This is because when the amount exceeds 10% by weight, chlorine ions become excessive and the effect of addition to the improved solidified soil described below reaches its peak. Therefore, this sodium ion content was improved and solidified on the assumption that the liquid curing agent was added to the improved solidified soil described later, as in the case of the chlorine ion content. Desirably, it is determined appropriately in consideration of the effect of addition of the liquid hardener in the soil. For example, when the content of the liquid hardener in the improved solidified soil described later is relatively high, sodium ions in the liquid hardener If the addition rate of the liquid curing agent in the improved solidified soil described below is relatively low, the content of sodium ions in the liquid curing agent is within the above range. It is desirable to set to the upper limit side.

  This liquid curing agent was mixed with a liquid curing agent, cement and water to produce a soil-solidifying material, and was improved and solidified in the same manner as sodium carbonate when the soil-solidifying material described below was used to improve and solidify the soil. An ammonium salt added for the purpose of promoting the alkalinity of the soil and preventing a decrease in mechanical strength due to neutralization is included. The content of this ammonium salt is preferably 2% by weight or less. The ammonium salt is preferably ammonium chloride, for example.

  The reason why the evaporation residue of the liquid curing agent is set in the range of 10 to 20% by weight is to ensure the total content rate in which the effect of adding the chlorine ions and sodium ions can be expected when the amount is less than 10% by weight. On the other hand, if it exceeds 20% by weight, not only the effect of adding the above-mentioned chlorine ions and sodium ions will reach its peak, but also the fluidity of the liquid curing agent cannot be ensured sufficiently. is there.

  The reason for adjusting the cobalt content of this liquid curing agent to 0.01 to 0.1% by weight is to increase the mechanical strength of the improved solidified soil by containing a cobalt compound that forms a complex. This is because harmful substances can be retained and elution can be prevented.

  The reason why the content of calcium ions in the liquid curing agent is set to a range of 0.1% by weight or less is that, when calcium ions are included, calcium carbonate produced by the reaction with sodium carbonate as the sodium salt. This is because the calcium carbonate adversely affects the properties of the improved solidified soil described later, and as a result, elution and diffusion of the harmful substances cannot be effectively prevented. Therefore, calcium ions must be 0.1 wt% or less in the liquid curing agent.

  Such a liquid curing agent, for example, as a component of the soil improvement and solidification method described later, mixed with other components to improve and solidify, waste measures, soil contamination measures, soft ground measures and concrete measures There are uses.

  As described above, according to the first embodiment, a liquid hardener exhibiting alkalinity, cement and water are mixed to produce a soil solidifying material, and when this soil solidifying material is used for improved solidification of soil, The soil solidified by sodium carbonate as a sodium salt can be maintained alkaline, thereby maintaining the mechanical strength of the solidified soil, and the water of cement and water can be maintained by the sodium carbonate and sodium chloride. It has the effect of promoting the sum reaction and reliably preventing the elution and diffusion of heavy metals such as hexavalent chromium and harmful substances such as hormone-inhibiting chemicals.

  Further, according to the first embodiment, by setting the evaporation residue of the liquid curing agent in the range of 10 to 20% by weight, the liquid curing agent can contain 70% by weight or more of liquid, and the liquid curing agent When mixing soil, cement, and water to produce a soil solidification material, the amount of water added can be reduced, the strength of the improved solidified soil can be increased, and the efficiency of the mixing operation can be improved. There is an effect that can be.

  Furthermore, according to this Embodiment 1, the liquid hardening | curing agent cobalt was adjusted to 0.01 to 0.1 weight%, the mechanical strength of the improved solidified soil was raised, and heavy metals and harmful substances were It is possible to hold and prevent elution.

  Moreover, according to this Embodiment 1, the solidification by the calcium carbonate produced | generated by reaction with sodium carbonate as a sodium salt by setting the calcium ion of a liquid hardening | curing agent to the range of 0.1 weight% or less is carried out. This has the effect of minimizing adverse effects on the properties of the soil.

Embodiment 2. FIG.
In the soil improvement solidification method according to Embodiment 2 of the present invention, the liquid hardening agent, cement and water shown in Embodiment 1 are mixed to produce a soil solidification material, and this soil solidification material is pumped to the soil. It is a method of improving and solidifying soil by stirring.

  For example, wastewater treatment sludge, human waste, manure, organic waste such as food residue, construction waste, bottom sediment in rivers and lakes, inorganic waste such as asphalt and concrete, incineration ash generated from incinerators, flying Soil such as soil that needs to be improved, such as contaminated soil or soft soil contaminated with harmful substances by reclaiming incinerated ash such as ash and its melt.

  As the cement, for example, as described in JP-A-2002-241166, various portland cements such as ordinary portland cement and early-strength portland cement, blast furnace cement, cement-based solidified material, and other cements have similar functions. Examples thereof include a curing material such as a bonding material.

  For example, the cement is in the form of a cement slurry to which water is added, or the cement itself is used, and water is appropriately added at the time of mixing, or the moisture content of the raw material is low even when using cement slurry. It is used in various usage forms such as replenishing water according to the usage.

  As described above, the cement is highly likely to contain a slight amount of harmful substances such as heavy metals such as hexavalent chromium and hormone-inhibiting chemical substances. For this reason, when soil is improved and solidified, the mixing ratio of the cement and the liquid curing agent is appropriately determined based on various factors such as the type of soil and the content of the harmful substances.

  As described above, according to the second embodiment, the liquid hardener shown in the first embodiment, cement and water are mixed to produce a soil-solidifying material, and the soil-solidifying material is pumped to the soil. By improving and solidifying the soil by stirring, it is possible to reliably prevent elution and diffusion of heavy metals such as hexavalent chromium and toxic substances such as hormone-inhibiting chemicals contained in the soil and cement. .

  Further, according to the second embodiment, by setting the evaporation residue of the liquid curing agent in the range of 10 to 20% by weight, the liquid curing agent can contain 70% by weight or more of liquid, and the liquid curing agent When mixing soil, cement, and water to produce a soil solidification material, the amount of water added can be reduced, the strength of the improved solidified soil can be increased, and the efficiency of the mixing operation can be improved. There is an effect that can be.

  Furthermore, according to the second embodiment, by adjusting the cobalt of the liquid curing agent to 0.01 to 0.1% by weight, the mechanical strength of the improved solidified soil is increased, and heavy metals and harmful substances are prevented. There is an effect of preventing elution.

  Further, according to the second embodiment, the above-described improvement by the calcium carbonate produced by the reaction with sodium carbonate as a sodium salt is achieved by setting the calcium ion of the liquid curing agent to a range of 0.1 wt% or less. There is an effect that the adverse effect on the properties of the solidified soil can be minimized.

Hereinafter, the application of the present invention will be specifically described with reference to examples.
Example 1.
FIG. 1 is a flowchart showing a process of improving and solidifying contaminated soil or soft ground using the liquid curing agent of the present invention (Embodiment 1). As shown in FIG. 1, the ground improvement device 10 includes an excavation agitator 12 including a rotatable agitation shaft 11, and a supply pump 13 that supplies a mixture from a mixer 5 provided separately from the excavation agitator 12. It is roughly composed of. Inside the agitation shaft 11 of the excavator agitator 12 is formed a communication port (not shown) for supplying the soil solidifying material 16 mixed with the liquid hardener, cement and water from the supply pump 13 to the tip side. A stirring blade 11 a is disposed at the lower end of the stirring shaft 11. It should be noted that both the stirring shaft 11 and the stirring blade 11a may be appropriately selected as single or plural according to the situation or the like.

  Next, a soil improvement and solidification method for contaminated soil and soft ground will be described. First, the ground improvement device 10 is installed on the site 14 including contaminated soil and soft ground. Next, cement 2, liquid curing agent 3 and water 8 are blended in a predetermined ratio and mixed in mixer 5 to produce and prepare soil solidifying material 16. Next, the plurality of stirring shafts 11 (two in FIG. 1) of the excavating stirrer 12 are respectively lowered to the site 14 while being rotated, and the soil at the site 14 is stirred by the stirring blades 11 a and stirred by the supply pump 13. The soil-solidifying material 16 is injected from the vicinity of the tip of the stirring shaft 11 through a communication port (not shown) of the shaft 11 to form a mixing stirring portion 15. And in the mixing stirring part 15 in which the soil solidification material 16 was inject | poured, contaminated soil or a soft ground and the soil solidification material 16 are fully mixed with the stirring blade 11a. Next, when the mixing and stirring unit 15 is dug to the predetermined depth by the stirring shaft 11, the excavating stirrer 12 is pulled out from the mixing and stirring unit 15 while the stirring shaft 11 is rotated forward or reverse. Also in that case, the contaminated soil or soft ground and the soil solidifying material 16 are sufficiently mixed by the stirring blade 11a, and the contaminated soil or soft ground is firmly solidified by the hydration reaction of the cement 2 over time.

  In this case, the liquid hardener 3 in the soil solidifying material 16 reliably prevents the elution and diffusion of harmful substances contained in the soil and cement, so that the impact on the environment of consolidated contaminated soil or soft ground can be reduced. Can be minimized.

The liquid curing agent 3 is one of the best modes, and its properties are as follows. The color tone of the liquid curing agent 3 is reddish purple, has a pH of 10.4, and exhibits an ammonia odor. The evaporation residue (measured at 105 ° C. for 24 hours) is 16.1%, and the density is 1. 143 g / cm ³ , viscosity is 4.2 m · Pas, ignition residue (measured at 600 ° C. for 30 minutes) is 98.0% by weight, chlorine ion content is 4.6% by weight, The amount of sodium ions was 4.8% by weight, the amount of cobalt was 0.04% by weight, and the amount of calcium ions was 0.1% by weight or less, which was about a trace.

Moreover, the said liquid hardening | curing agent 3 is one of the best forms, The property is as follows. The color tone of the liquid curing agent 3 is reddish purple, has a pH of 10.0 and an ammonia odor, the evaporation residue (measured at 105 ° C. for 24 hours) is 16.7%, and the density is 1. 149 g / cm ³ , viscosity is 4.4 m · Pas, ignition residue (measured at 600 ° C. for 30 minutes) is 97.1 wt%, chloride ion content is 4.1 wt%, The amount of sodium ions was 4.4% by weight, cobalt was 0.06% by weight, and the amount of calcium ions was 0.1% by weight or less.

Next, an experiment for confirming the elution of harmful substances in the improved solidified soil 7 was performed.
Elution experiment Using 1m ³ of lake bottom mud as contaminated soil, 120 to 180kg of cement 2 and 1 to 15L of liquid curing agent 3, adding water depending on the water content in the lake bottom mud. Thus, improved solidified soil 7 was produced. At this time, an elution experiment was performed in which the content of harmful substances in the lake bottom mud was quantified and the amount of toxic substances eluted from the improved solidified soil 7 was quantified. The contents of harmful substances such as lead, arsenic, total mercury and cadmium contained in the lake bottom mud and the amount of elution from the improved solidified soil were quantitatively analyzed. The results are shown in Table 1.

  As is apparent from Table 1, in the lake bottom mud elution experiment, the harmful substances (lead, arsenic, total mercury and cadmium) contained in the lake bottom mud are 0.1 mg / L or less or less than the limit of quantification, It was confirmed that there was substantially no elution from the improved solidified soil. In Table 1, “-” means that it was contained but quantitative analysis was not performed.

It is a flowchart which shows the process of improving and solidifying a contaminated soil and soft ground as an Example of the soil improvement and solidification method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Contaminated soil, soft ground 2 Cement 3 Liquid hardening agent 5 Mixer 7 Improved solidified soil 8 Water 10 Ground improvement device 11 Stirring shaft 11a Stirring blade 12 Excavation stirrer 13 Supply pump 14 On-site 15 Mixing stirrer 16 Soil solidifying material

Claims (1)

  A sodium salt containing sodium carbonate and sodium chloride as a main component, an ammonium salt containing ammonium chloride as a main component, and a cobalt compound are blended in a liquid of 70% by weight or more to increase the content of chloride ions and sodium ions. Each is adjusted to 1 to 10% by weight, the cobalt content is adjusted to 0.01 to 0.1% by weight, the evaporation residue is set to a range of 10 to 20% by weight, and calcium ions are contained. A liquid hardener with a rate set to a range of 0.1% by weight or less is mixed with cement to make a soil solidified material, and this soil solidified material is pumped into the soil and stirred to improve and solidify the soil. And soil improvement solidification method.

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