JP6412691B2 - Soil improvement material for improving soil quality of sedimentary soil containing salt and moisture, and soil improvement method - Google Patents

Description

  The present invention relates to a soil quality improving material for improving the soil quality of sedimentary soil containing salt and moisture, and a soil quality improving method.

  When a tsunami occurs, sediments mixed with seawater are deposited on the coast and become tsunami deposits. This tsunami deposit is in the form of a clay containing salt and moisture, and it often contains garbage. Because it contains clay, it is difficult to recycle tsunami deposits because they ooze out due to water leaching and cannot be compacted even if they try to recycle them into embankment materials. Met. In particular, the tsunami deposit soil adhering to the garbage is difficult to separate from the garbage, making recycling more difficult.

  Regarding the recycling of tsunami-deposited soil, quick lime and cement can be mixed to reduce moisture in the soil, increasing the strength of the soil, and mixing gravel and sand can change the soil particle size and compact the soil. It was generally done to make it possible. However, when quicklime and cement are mixed, the soil becomes alkaline and may promote the elution of specific harmful substances. In particular, in the case of soil with a high water content, the mixing amount of quick lime or the like must be increased, which may increase the alkalinity and further promote the elution. In addition, since quicklime and cement are powders, they may be scattered during work, and a temporary storage period for dehydration and solidification reactions is required. On the other hand, in the method of mixing gravel and sand, there is a concern that the required amount of gravel and sand increases and a dedicated soil improvement machine is required.

  Here, Patent Document 1 describes a technique for manufacturing an amount of earthwork material such as embankment material by mixing PS ash (paper sludge incineration ash) and various chemicals into the bottom sediment which is the bottom sediment. Has been. Patent Document 2 describes a technique for suppressing the growth of weeds by laying a granulated solid body containing PS ash on the soil surface or in the soil.

JP2013-127030A JP 2012-17323 A

  In the technique of Patent Document 1, since PS ash is mixed, the strength of the soil can be increased by absorbing moisture into the PS ash. However, since it is a powder, there is a risk of scattering during work. Moreover, although the technique of patent document 2 is a granulated solidified body of PS ash, the problem of scattering is less likely to occur, but it is a weed growth suppressing material, so it is motivated to be used for soil quality improvement of sedimentary soil. I can't.

  Furthermore, the tsunami deposit soil has the property that when the salt content is washed away and the salt concentration is lowered, the soil particles are dispersed. For this reason, even if quick lime, PS ash, etc. are mixed and used for embankment, the salt concentration of embankment falls with rainwater etc., and there exists a possibility that soil particles may flow out as muddy water. The outflow of the soil particles is not particularly considered in the above-described general technique and the technology described in each patent document.

  The present invention has been made in view of such circumstances. The purpose of the present invention is to improve the soil quality of sedimentary soil containing salinity and moisture, while suppressing the scattering of the soil quality improving material during work and increasing the strength. It is to make it appear early and to suppress the outflow of soil particles.

In order to achieve the above-mentioned object, the present invention provides a soil conditioner for improving the soil quality of sedimentary soil containing salt and moisture, wherein a water-soluble component serving as a source of calcium ions and sulfate ions has a water absorption property. The porous granular material is a porous particle obtained by firing PS ash granulated material or diatomaceous earth .

Further, the present invention provides a soil improvement method of improving the soil of sediment containing salt and water, holding the water-soluble component as a source of calcium ions and sulfate ions in a porous granular material having a water absorption is made by said porous granulate, PS Haizotsubu thereof, or a soil improvement agent is porous particles obtained by firing diatomaceous earth, characterized by mixing the sediment.

  According to these inventions, since the porous granular material has water absorption, moisture contained in the sedimentary soil is quickly absorbed. And it becomes easy to produce the passage of water around a porous granular material, and the drainage property in the soil after improvement becomes favorable. By these, intensity | strength can be expressed early. Moreover, since it is a granular body, it becomes difficult to disperse | distribute during work rather than powder, and workability | operativity improves. In addition, since the salt content (sodium ion) retained in the soil (montmorillonite) is replaced with calcium ions derived from water-soluble components, the swelling of the soil can be suppressed. Furthermore, since the sulfate ion concentration in the moisture of the sedimentary soil is increased, the replacement of sodium ions with calcium ions can be promoted. By these, the outflow of soil particles can be suppressed.

In the above-described soil improving material, the porous granular material is preferably a PS ash granulated product obtained by granulating PS ash by adding and mixing a solidifying material and water . With this configuration, PS ash can be effectively used.

In the soil improvement method described above, the mixing amount of the soil improvement material to the sedimentary soil is such that the concentration of sulfate ion in the liquid when 124 parts by weight of pure water with a weight ratio of 5 is added to the dry mixed soil with a weight ratio of 1 is 124 mg / It is preferable to set it to be L or more and the calcium ion concentration to be 52 mg / L or more . Moreover, it is preferable to mix the soil quality improving material with aeration with respect to the deposited soil.

  According to the present invention, when improving the soil quality of sedimentary soil containing salt and moisture, it is possible to suppress scattering of the soil quality improving material during work, to express the strength early, and to suppress the outflow of soil particles. Can do.

It is a figure explaining the particle size distribution of the soil improvement material of an Example and a comparative example, the sample soil used for the portable cone penetration test, and the density of soil particles. It is the perspective view and sectional drawing of a banking. It is a figure explaining the property analysis result of each sample (test soil, mixed soil) immediately after raising and after 6 months. It is a figure explaining the result of the portable cone penetration test with respect to the embankment (each test section) after six months progress. It is a figure explaining the analysis result of the initial property of the sample soil used for the sieving test. It is a figure which illustrates the procedure of a screening test typically. It is a figure which shows the result of a screening test in a table format. It is a flowchart explaining the procedure of a suspension dispersion | distribution test. It is a figure which shows the result of the property test with respect to the test soil C in a tabular form. It is a figure which shows the result of the property test with respect to the test soil D in a tabular form. It is a photograph explaining the plugged cylinder after standing still. It is a figure which illustrates typically an operation of sulfate ion and calcium ion. It is a photograph explaining the suspension dispersion test of PS ash material improvement district and gypsum improvement district.

  Hereinafter, embodiments of the present invention will be described. First, the soil improvement material will be described. As shown in FIG. 1A, in this embodiment, two types of soil improvement materials were tested. One is quick lime (CaO) and the other is PS ash material.

  Quicklime was selected because it is a soil quality improving material of a comparative example and is widely used as a soil quality improving material for soil containing moisture. Quicklime is soluble in water and chemically reacts with water to produce calcium hydroxide. For this reason, if it uses for soil quality improvement, the soil after improvement will shake largely to alkalinity.

  In addition, it was confirmed by a preliminary test that the soil quality could be improved by adding quick lime in an amount that would be 1.2 to 5% by weight of the target soil if the water content was 20 to 50%. And when using quicklime, it is necessary to adjust the addition amount according to the moisture content of the soil used as improvement object.

  The PS ash material is an embodiment of the present invention, and is constituted by a porous granular material having water absorption. This PS ash material is obtained by adding and mixing a solidifying material and water to PS ash and granulating the particle size to be about 1 mm to 5 cm. For this reason, when PS ash material is mixed with sedimentary soil, the passage of water tends to occur around the PS ash material, and drainage in the improved soil is improved. Moreover, since it is a granular material, it is hard to disperse during work rather than powder.

  As will be described later, the PS ash material contains a water-soluble component that serves as a supply source of calcium ions and sulfate ions. Examples of such PS ash materials include Nippon Paper Industries' trade name “Weed Tome-kun” (registered trademark, the same shall apply hereinafter) and Yoshu Kogyo's trade name “Ash Stone”.

  In this embodiment, three tests including a portable cone penetration test, a sieving test, and a suspension dispersion test were performed in order to evaluate these soil improvement materials.

  The portable cone penetration test measures the cone penetration resistance of the embankment and was conducted for the purpose of confirming the strength of the improved sedimentary soil with the soil conditioner. The sieving test was performed by adding and mixing a soil conditioner to the test soil and performing sieving, and was conducted for the purpose of confirming the handling properties of the improved sedimentary soil. The suspension dispersion test was to disperse the improved soil added and mixed with the soil quality improver in water and observe it statically, and was conducted for the purpose of confirming the retention force of the soil particles in the improved sedimentary soil. Hereinafter, each test will be described in detail.

  First, the portable cone penetration test will be described. In the portable cone penetration test, a soil mixture was first prepared by mixing soil conditioner with the test soil. Next, the test soil and mixed soil were raised to form a fill. After 6 months, cone penetration resistance was measured for the embankment.

  FIG. 1B is a diagram showing the particle size distribution of the test soil in a tabular form. In this test, sedimentary soil was sampled from paddy fields that were subjected to tsunami and used as test soil. This sample soil was clayey sand and was difficult to handle. Specifically, the viscous soil (fine particles having a particle size of less than 0.075 mm) accounted for 48.4%, which was less than 50%. The sand content (particle size: 0.075 mm or more and less than 2 mm) was 47.8%, and gravel content (particle size: 2 mm or more and less than 75 mm) was 3.8%.

  In this portable corn penetration test, the above-mentioned “weed and mekkun” was used as a PS ash material. And by the preliminary test, if it was the target soil of normal water content ratio, it was confirmed that the soil quality can be improved by adding PS ash material in an amount of 15% by weight of the target soil.

Regarding the test case, in this test, a case using the test soil as it was, a case of a comparative example in which quick lime was mixed as a soil improvement material, and a case of an example in which PS ash material was mixed as a soil improvement material were set. Quick lime was mixed in an amount of 20 kg per 1 m ^{3 of the} test soil. In addition, since the density of the soil particle of a test soil is 2.693 g / cm < ³ >, the weight ratio of quicklime and a test soil is 2693: 20 = 1: 0.00743. The PS ash material was mixed in an amount of 200 kg per 1 m ^{3 of the} test soil. In this case, the weight ratio of the PS ash material to the test soil is 2893: 200 = 1: 0.0743.

  The soil improvement material was mixed with the test soil using a backhoe. Specifically, soil improvement material was spread on the surface of the test soil using buckets on the test soil spread on the ground. Then, the soil sample was scooped up with a soil conditioner with a bucket and dropped from a high place. The soil improvement material was mixed with the test soil by repeatedly scooping and dropping the test soil and the soil improvement material.

  At the time of mixing the soil improvement material with the test soil, the PS ash material tended to loosen the test soil earlier than quick lime. That is, in the PS ash material, a decrease in the moisture content of the test soil was confirmed immediately after mixing. On the other hand, in quicklime, it has confirmed that time until a moisture content fall was confirmed became longer than the case where PS ash material was used. This is probably because PS ash material is physically dehydrated by absorbing water, whereas quick lime is dehydrated by chemically reacting with water.

  In addition, calcium ions dissolve into the test soil due to the water-soluble components contained in the PS ash material, but aeration and mixing are performed by repeating the above-mentioned scooping and dropping, and the calcium ions are carbonated. Promoted. Thereby, the bad influence to the vegetation resulting from the excessive fall of pH can be suppressed. Furthermore, since the surface of the soil dries, the properties of the mixed soil can be brought into a dry state like sand. On the other hand, even when quicklime was mixed in the same manner, it did not become such a dry state.

  After preparation of the mixed soil, as shown in FIG. 2A, the mixed soil was raised in the shape of a vertically long quadrangular pyramid to form the embankment 1. The height 1 of the embankment 1 is about 1 m, and the length L is about 7 m at the bottom. And the left side in FIG. 2A is the quick lime improvement district 2 raised by the mixed soil by quick lime, and the right side is the PS ash material improvement zone 3 raised by the mixed soil by the PS ash material. Furthermore, the central part is the unmodified zone 4 that was raised with the test soil. For this reason, the center portion corresponds to a case using the test soil as it is, the left portion corresponds to a case where quick lime is mixed, and the right portion corresponds to a case where PS ash material is mixed. In addition, the length of the right side part and the left side part was about 3 m, and the length of the center part was about 1 m.

  Properties were analyzed for each of the mixed soil immediately after raising (immediately after compaction) and the mixed soil after 6 months. Hereinafter, the result of property analysis will be described.

  FIG. 3 (a) shows the analysis result of the mixed soil immediately after swelling, and FIG. 3 (b) shows the analysis result of the mixed soil after 6 months. In these figures, the unmodified soil corresponds to a test case using the test soil as it is, and means a test soil in which the soil quality improving material is not mixed. The quick lime improved soil corresponds to a test case of a comparative example in which quick lime is mixed, and the PS ash material improved soil corresponds to a test case of an example in which PS ash material is mixed.

  The corn index was measured by compacting the disturbed soil for the mixed soil immediately after swelling. At that time, the number of compactions was 25. Regarding the mixed soil after 6 months, the surface soil 5 shown in FIG.

  First, with reference to Fig.3 (a), the property of each test case immediately after raising is demonstrated. Immediately after swelling, the samples in each test case were in a plastic state. That is, the moisture content of the unmodified soil was 35.3%, the moisture content of the quicklime improved soil was 37.4%, and the moisture content of the PS ash material modified soil was 40.8%. All samples had a water content lower than the liquid limit and higher than the plastic limit.

  Here, when the unmodified soil and the PS ash material modified soil were compared, regarding the liquid limit, the unmodified soil was 44.6%, whereas the PS ash material modified soil was 57.7%. . From this, it can be said that the PS ash material improved soil can maintain the plastic state even if the moisture content is about 13% higher than that of the unmodified soil. Regarding the plastic limit, the unmodified soil was 25.3%, while the PS ash material modified soil was 32.4%. When the difference between the liquid limit and the plastic limit was calculated, the unmodified soil was 19.3%, while the PS ash material modified soil was 25.3%. From this, it can be said that the PS ash material improved soil has a wider water content ratio that can maintain the plastic state than the unmodified soil.

  Similarly, when quicklime improved soil and PS ash material improved soil were compared, quicklime improved soil was 49.0% with respect to the liquid limit. That is, it can be said that PS ash material improved soil can maintain a plastic state even if the moisture content is about 9% higher than quick lime improved soil. Moreover, quick-lime improved soil was 28.5% regarding the plastic limit, and the difference between the liquid limit and the plastic limit was 20.5%. Since the PS ash material improved soil was 25.3%, it can be said that the PS ash material improved soil has a wider moisture content range than the quick lime improved soil to maintain the plastic state.

Regarding the cone index, the unmodified soil was 155 kN / m ² and the quicklime improved soil was 185 kN / m ² , while the PS ash material modified soil was 565 kN / m ² . From this result, it was confirmed that the PS ash material improved soil can obtain high strength immediately after being laid. Moreover, regarding pH, unmodified soil showed weak alkalinity from pH 6-7 to weak acidity, quick lime improved soil showed strong alkalinity at pH 12, and PS ash material improved soil showed weak alkalinity at pH 8-9. Regarding electrical conductivity, unmodified soil was 70 mS / m, quicklime improved soil was 90 mS / m, and PS ash material improved soil was 80 mS / m.

Next, with reference to FIG. 3B, the properties of each sample after 6 months have been described. There was no significant difference between the samples with respect to the density after 6 months. That is, regarding the wet density, the unmodified soil was 1.691 g / cm ³ , the quicklime improved soil was 1.608 g / cm ³ , and the PS ash material modified soil was 1.597 g / cm ³ . Regarding the dry density, the unmodified soil was 1.285 g / cm ³ , the quicklime improved soil was 1.230 g / cm ³ , and the PS ash material modified soil was 1.212 g / cm ³ .

  In addition, regarding the water content ratio and pH, there was no significant difference between the samples. That is, regarding the moisture content, unmodified soil was 31.6%, quicklime improved soil was 30.7%, and PS ash material improved soil was 31.8%. Regarding the pH, the unmodified soil had a pH of 7.7, the quicklime improved soil had a pH of 8.3, the PS ash material improved soil had a pH of 7.8, and the quicklime improved soil had a slightly higher pH than the other samples.

  On the other hand, regarding electrical conductivity, a significant difference was observed between the samples. That is, regarding electrical conductivity, unmodified soil was 17 mS / m, quicklime improved soil was 31 mS / m, and PS ash material improved soil was 51 mS / m. Here, the electrical conductivity is proportional to the amount of ions contained in the soil, and since the surface of the soil particles is negatively charged, the low electrical conductivity means that the soil particles flowed out due to rainwater etc. it is conceivable that.

  When the electrical conductivity was compared between each sample immediately after the swelling and each sample after 6 months, the unmodified soil decreased most significantly from 70 mS / m to 17 mS / m, and the quicklime improved soil was 90 mS / m. It is greatly reduced from m to 31 mS / m. On the other hand, PS ash material improved soil has the smallest decrease from 80 mS / m to 51 mS / m. From this, it can be said that PS ash material improved soil has stronger retention of soil particles than quick lime improved soil and unmodified soil.

  Next, the result of the portable cone penetration test for the embankment will be described. This test was performed on the embankment after the elapse of 6 months as described above in accordance with the Geotechnical Society Standard JGS1431.

  FIG. 4 is a graph showing the cone penetration resistance of each test zone (unmodified zone 4, quicklime improved zone 2, PS ash material improved zone 3) for each depth. In the same figure, the symbol x indicates the cone penetration resistance of the unmodified zone 4, the symbol □ indicates the cone penetration resistance of the quicklime improved zone 2, and the symbol O indicates the cone penetration resistance of the PS ash material improved zone 3. As shown in the figure, the maximum penetration depth of PS ash material improvement zone 3 was 0.35 m, while unimproved zone 4 and quicklime improvement zone 2 could penetrate up to 0.95 m.

  From this result, it was confirmed that the PS ash material improvement zone 3 is a bank with higher strength than the other test zones 2 and 4. This is presumably because when PS ash material is used as the soil improvement material, moisture is quickly absorbed from the soil sampled by the clay soil (deposited soil collected from paddy fields).

  That is, it is difficult to compact with viscous soil sand containing excessive moisture, and the strength of the embankment cannot be increased. Moreover, when quick lime is used as a soil improvement material, since it is a chemical reaction, it takes time for dehydration, and it is considered that excessive moisture is contained at the time of compaction. On the other hand, PS ash material physically absorbs excess moisture into the porous granular material, so it is considered that the moisture of the viscous soil sand at the time of compaction can be adjusted to an amount suitable for compaction. As a result, it is understood that the strength of the embankment could be increased.

  Moreover, since PS ash material is a porous granule, a clearance gap is formed between granules and it can make drainage favorable. Thereby, it is thought that excessive moisture does not stay in the embankment and suppresses the softening of the embankment.

  Next, the screening test will be described. As described above, in this sieving test, an improved soil was obtained by adding and mixing a soil condition improver to the soil mixed with debris. After that, screening was performed for each of the improved soil and the unmodified soil.

  Fig.5 (a) is a figure explaining the analysis result of the initial property of the sample soil used for the screening test. In this test, two types of test soils A and B were used. These test soils A and B were sandy soils (fine-grained soils) that had been temporarily placed by peeling off the topsoil of the farmland, and had a high water content.

The test soil A had a density of 2.546 g / cm ³ , a natural water content ratio of 46.3%, and a loss on ignition of 9.4. Regarding the particle size distribution, the gravel content was 1.2%, the sand content was 53.1%, the silt content was 29.1%, and the clay content was 16.6%. The maximum dry density was 1.347 g / cm ³ and the optimum water content ratio was 30.3%. On the other hand, the sample soil B had a density of 2.631 g / cm ³ , a natural water content ratio of 38.1%, and a loss on ignition of 7.9. Regarding the particle size distribution, the gravel content was 0.6%, the sand content was 70.8%, the silt content was 16.4%, and the clay content was 12.2%. The maximum dry density was 1.586 g / cm ³ and the optimum water content ratio was 20.4%.

Quick lime and PS ash material were mixed with each of the test soils A and B. As shown in FIG. 5 (b), with respect to quick lime, 1.25% (21 kg / m ³ ) by weight for the test soil A, and 4.75% by weight for the test soil B. (81 kg / m ³ ) was added. Regarding the pH after mixing, the test soil A had a pH of 11.5, and the test soil B had a pH of 12.5. Further, with respect to the PS ash material, 15% (255 kg / m ³ ) was added by weight to each of the test soils A and B. The pH after mixing was pH 9.1 for test soil A and pH 10.6 for test soil B.

Further, as shown in FIG. 5 (c), regarding the cone index of the compacted soil (25 times of compaction), in the test soil A, the unmodified soil is 123 kN / m ² , and the quick lime modified soil is 191 kN / m ^2. The PS ash material improved soil was 290 kN / m ² . Further, the test試土B, Unfinished soil 40 kN / ^{m 2,} quicklime modified soil is 157kN ^/ m 2, PS ash materials modified soil was 173kN / ^{m 2.}

  From these results, it was confirmed that the PS ash material improved soil has higher strength than the quick lime improved soil and can suppress the increase in pH. In addition, it is thought that the reason is the same as the reason demonstrated in the portable cone penetration test.

  As shown in FIG. 6, in this screening test, quick lime (comparative example) and PS ash material (examples) were added and mixed as soil conditioners to each sample soil A and B mixed with debris. The soil quality was improved. After that, each improved soil and unmodified soil was screened using a sieve and a reciprocating shaker. Two types of sieves, 19 mm and 9.5 mm, were used.

  As shown in FIG. 7, regarding the sieve transmittance of the test soil A, the unmodified soil was 62% at 19 mm and 11% at 9.5 mm. And the quick lime improved soil was 88% at 19 mm and 47% at 9.5 mm, and the PS ash material improved soil was 84% at 19 mm and 46% at 9.5 mm. On the other hand, regarding the sieve permeability of the test soil B, unmodified soil is 22% at 19 mm, 5% at 9.5 mm, quicklime improved soil is 35% at 19 mm, and 8% at 9.5 mm. Material improvement soil was 63% at 19 mm and 15% at 9.5 mm.

  From these results, it was confirmed that when PS ash material was used as the soil improvement material, classification efficiency equal to or higher than that when quick lime was used was obtained. The reason why this difference has occurred is that PS ash material is physically dehydrated, whereas quick lime is dehydrated by a chemical reaction.

  Next, the suspension dispersion test will be described. As described above, the suspension dispersion test is to disperse the improved soil added and mixed with the soil conditioner in water and to observe the soil, and to confirm the retention of soil particles in the improved sedimentary soil. It was.

  As shown in FIG. 8, in this test, preparation of test soil (S1), treated soil sorting (S2), pure water addition (S3), horizontal shaking (S4), standing (S5), agglomeration / Precipitation was confirmed (S6) and water was removed (S7).

In the preparation of the test soil (S1), a soil improvement material was appropriately mixed with the collected soil to prepare an initial soil. Then, the shore bank embankment was made by raising the initial soil. Then, the initial soil was used as test soil C, and the surface soil collected from the bank bank after about 4 and a half months from the preparation was used as test soil D. These test soils C and D are three types: unmodified soil, quicklime improved soil mixed with quick lime at a rate of 20 kg / m ³ , and PS ash material improved soil mixed with PS ash material at a rate of 200 kg / m ^3. It is made up of. And about each test soil C and D, the wet density, the dry density, and the water content ratio were measured after extraction.

  In treated soil sorting (S2), each test soil C, D in a specified amount (20g equivalent to dry soil) is dispensed into a 200mL plugged cylinder, and in pure water addition (S3), pure water is added to a scale of 200mL. did. In horizontal shaking (S4), the plugged cylinder was shaken for 1 hour, and the test soil was dispersed in pure water. In the standing (S5), it was allowed to stand for 24 hours, and in the confirmation of aggregation / precipitation (S6), the settling volume (sludge reading) was confirmed. In the upper water removal (S7), the specified amount (50 mL, 100 mL) of the upper water was collected, and component analysis, electrical conductivity, pH and the like were measured.

  FIG. 9 shows the result of the property test of the test soil C, and FIG. 10 shows the result of the property test of the test soil D. FIG. 11 is a photograph explaining the state of the plugged cylinder after standing. For convenience, the test result in the unmodified soil is referred to as an unmodified zone, the test result in the quick lime improved soil is referred to as a quick lime improved zone, and the test result in the PS ash material improved soil is referred to as a PS ash material improved zone. Moreover, the ion concentration described in each figure is a value at the time of adding the pure water of 5 weight ratio with respect to the dry mixed soil of 1 weight ratio.

  Regarding the wet density and the dry density, there was no significant difference between the test sections. On the other hand, regarding the water content ratio, it was confirmed that the water retention capacity of the PS ash material improvement district was higher than that of the unimproved district and the quick lime improvement district.

That is, as shown in FIG. 9, with respect to the test soil C, the wet density of the unmodified zone is 1.640 to 1.734 g / cm ³ , and the wet density of the quicklime improved zone is 1.751 to 1.772 g / cm ³ . ³ , the wet density of the PS ash material improvement zone was 1.680 to 1.837 g / cm ³ . The dry density of the unmodified zone is 1.225 to 1.264 g / cm ³ , the dry density of the quicklime improved zone is 1.282 to 1.298 g / cm ³ , and the dry density of the PS ash material improved zone is 1.214. It was ˜1.388 g / cm ³ . In addition, the moisture content of the unmodified zone is 33.9 to 38.9%, the moisture content of the quicklime improved zone is 36.3 to 36.6%, and the moisture content of the PS ash material improved zone is 32.4 to 40.0. %Met.

On the other hand, as shown in FIG. 10, for the test soil D, the wet density of the unmodified zone is 1.673 to 1.722 g / cm ³ , and the wet density of the quicklime improved zone is 1.622 to 1.757 g / cm ³ . ³ , the wet density of the PS ash material improvement zone was 1.503 to 1.682 g / cm ³ . The dry density of the unmodified zone is 1.297 to 1.317 g / cm ³ , the dry density of the quicklime improved zone is 1.238 to 1.348 g / cm ³ , and the dry density of the PS ash material improved zone is 1.133. ˜1.244 g / cm ³ . In addition, the moisture content of the unmodified zone is 28.5 to 32.8%, the moisture content of the quicklime improved zone is 29.2 to 31.0%, and the moisture content of the PS ash material improved zone is 32.7 to 36.0. %Met.

  Regarding the dispersed state of the test soil C, as shown in FIG. 11A, the soil particles (sludge) were dispersed in the unmodified zone and the quicklime improved zone of the test soil C as a whole. On the other hand, in the PS ash material improvement district, the soil particles were in a state of sedimenting at the bottom of the cylinder. A similar dispersion state was confirmed for the test soil D. That is, as shown in FIG. 11 (b), the soil particles were dispersed as a whole in the unmodified zone and the quicklime improved zone, and the soil particles were precipitated at the bottom of the cylinder in the PS ash material improved zone.

  Thus, since the big difference was confirmed in the dispersion state of the soil particle between the unimproved area and the quick lime improved area and the PS ash material improved area, the components contained in the aqueous solution were compared. Referring to FIGS. 9 and 10, it was confirmed that the content of water-soluble calcium ions and sulfate ions was particularly higher in the PS ash material improved area than in the unimproved area and the quick lime improved area.

  For example, the water-soluble calcium ion of the test soil C was 220 mg / L in the PS ash material improved area, but 4.0 mg / L in the unimproved area and 73 mg / L in the quicklime improved area. The sulfate ion of the test soil C was 440 mg / L in the PS ash material improved district, but was 21 mg / L in the unmodified district and 26 mg / L in the quicklime improved district. Similarly, the water-soluble calcium ion of the test soil D was 120 mg / L in the PS ash material improved district, but was 5.2 mg / L in the unmodified district and 44 mg / L in the quicklime improved district. The sulfate ion of the test soil D was 270 mg / L in the PS ash material improved district, but was 20 mg / L in the unmodified district and 21 mg / L in the quicklime improved district.

  In addition, it was confirmed that the PS ash material improved district was higher in electrical conductivity than the unimproved district and the quicklime improved district. Regarding the electric conductivity of the test soil C, it was 56 mS / m in the PS ash material improved district, but was 11 mS / m in the unmodified district and 32 mS / m in the quicklime improved district. Similarly, regarding the electric conductivity of the test soil D, it was 56 mS / m in the PS ash material improved district, but 10 mS / m in the unmodified district and 38 mS / m in the quicklime improved district.

  From the above results, it was considered that water-soluble calcium ions and sulfate ions contributed to the dispersion suppression (acceleration of aggregation) of the soil particles. For example, as shown in FIG. 12A, montmorillonite M, which is a main component of clay, has a multilayer structure. And as shown in FIG.12 (b), in the sodium type thing, a sodium ion and a water molecule have entered between layers. It is thought that when many water molecules enter between the layers, the space between the layers opens, and the soil particles swell and flow out from the embankment surface layer. Here, as shown in FIG. 12C, when water-soluble calcium ions are present, sodium ions are replaced with calcium ions to form calcium-type montmorillonite. The calcium type has a smaller amount of water molecules held between the layers than the sodium type. Thereby, swelling of soil particles is suppressed and the outflow amount from the embankment surface layer is also reduced.

  In order to confirm this, a suspension dispersion test was performed on PS ash material improved soil mixed with PS ash material and gypsum improved soil mixed with dihydrate gypsum. The reason for selecting dihydrate gypsum is that it contains water-soluble calcium ions and sulfate ions. In this test, the mixing ratio of PS ash material and dihydrate gypsum to the sedimentary soil is 0.2 g / kg, 0.5 g / kg, 1 g / kg, 2 g / kg, 5 g / kg, 10 g / kg, 20 g / kg. kg.

  As shown in FIG. 13 (a), in the PS ash material modified section using the PS ash material modified soil, sedimentation of soil particles at the bottom of the cylinder was confirmed in a test case with a mixing ratio of 20 g / kg. On the other hand, as shown in FIG. 13 (b), in the gypsum improved section with gypsum improved soil, sedimentation of soil particles at the bottom of the cylinder was confirmed in a test case with a mixing ratio of 2 g / kg. Similarly, precipitation was confirmed even in a test case where the mixing ratio was 5 to 20 g / kg. That is, it is understood that the PS ash material carries a component equivalent to dihydrate gypsum (a water-soluble component serving as a supply source of calcium ions and sulfate ions), and the amount supported is 0.1% by weight of dihydrate gypsum. It is understood.

  Here, the sulfate ion concentration in the test case of 2 g / kg dihydrate gypsum is 124 mg / L, and the water-soluble calcium ion concentration is 52 mg / L. The sulfate ion concentration in the test case of dihydrate gypsum 20 g / kg is 1240 mg / L, and the water-soluble calcium ion concentration is 520 mg / L. Then, considering the results of FIG. 13 (b) and FIGS. 9 and 10, it is understood that sedimentation of soil particles occurs even when dihydrate gypsum is mixed with sedimentary soil at a rate higher than 20 g / kg. Therefore, it is understood that sedimentation of soil particles occurs when sulfate ions are present at a concentration of 124 mg / L or more and a water-soluble calcium ion concentration of 52 mg / L or more.

  Summarizing the experiments described above, the following can be said.

  First, by using PS ash material as a soil improvement material, it is possible to reduce the amount of moisture in the sedimentary soil earlier and to increase the compaction strength compared to the case of using quick lime, which is a general soil improvement material. be able to. And if PS ash material is used, sedimentary soil can be loosened rapidly and a handling property can be improved. This is because quick lime is dehydrated by a chemical reaction, whereas PS ash material physically adsorbs and retains moisture inside the porous granular material. Moreover, since the particle size of PS ash material is about 1 mm-5 cm, it is hard to be scattered rather than powder and workability | operativity can be improved.

  Furthermore, since PS ash materials contain water-soluble components that serve as a source of sulfate ions and water-soluble calcium ions, sodium ions can be efficiently replaced with calcium ions, and the outflow of soil particles due to rain water or the like, that is, embankment The generation of turbid water from can be suppressed.

  The above description of the embodiment is for facilitating the understanding of the present invention, and does not limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof. For example, you may comprise as follows.

  In the above-described embodiment, the PS ash material is exemplified as the soil improvement material, but the present invention is not limited to this. That is, it is understood that the same effect as the PS ash material can be obtained if a water-soluble component serving as a supply source of calcium ions and sulfate ions is held in a porous granular material having water absorption. For example, porous particles obtained by firing diatomaceous earth (trade name “Isolite” [registered trademark]) may have gypsum held as a water-soluble component serving as a source of calcium ions and sulfate ions. Good.

DESCRIPTION OF SYMBOLS 1 ... Filling, 2 ... Quick lime improvement zone, 3 ... PS ash material improvement zone, 4 ... Non-improvement zone, 5 ... Surface soil of embankment, H ... Height of embankment, L ... Length of embankment, M ... Montmorillonite

Claims (5)

A soil improvement material that improves the soil quality of sedimentary soil containing salt and moisture,
Water-soluble component as a source of calcium ions and sulfate ions, becomes held in the porous granules having a water absorption, the porous granules are obtained by sintering PS Haizotsubu thereof, or diatomaceous earth A soil improvement material characterized by being porous particles . The soil improvement agent according to claim 1, wherein the porous granular material is a PS ash granulated product obtained by adding and mixing a solidifying material and water to PS ash . A soil improvement method for improving the soil quality of sedimentary soil containing salt and moisture,
Water-soluble component as a source of calcium ions and sulfate ions is held in the porous granules having a water absorption, the porous granules are obtained by sintering PS Haizotsubu thereof, or diatomaceous earth A soil improvement method comprising mixing a soil improvement material which is a porous particle into the sedimentary soil.   The mixing amount of the soil improvement material to the sedimentary soil is such that the concentration of sulfate ion in the liquid is 124 mg / L or more when pure water having a weight ratio of 5 is added to dry mixed soil having a weight ratio of 1, and calcium. The soil quality improving method according to claim 3, wherein the ion concentration is determined to be 52 mg / L or more.   The soil quality improving method according to claim 3 or 4, wherein the soil quality improving material is mixed with the sedimentary soil while being aerated.