Improved ground construction method

Abstract

To provide an improved ground construction method that enables efficient construction of improved ground without requiring large-scale and deep excavation over a wide area or a large temporary soil storage yard, when constructing a foundation ground for a sabo dam on soil and sand that do not easily consolidate.SOLUTION: An improved ground construction method comprises steps of: setting sections in ground G containing highly viscous cohesive soil, lumpy hard cohesive soil, weathered rock converted into sediment or heavily weathered rock, volcanic ash soil, or organic soil; excavating the set sections to form foundation holes M; pouring soil S, crushed stone B containing at least one of crushed stone, gravel, pebbles, sandy gravel, riverbed sand and gravel, sandy gravel soil, and gravelly soil, and cement milk C into the foundation holes M, and stirring and kneading them to produce muddy improved soil 20A; and forming a solidified body 20 by solidifying a muddy improved soil aggregate 20B obtained by accumulating a predetermined amount of the muddy improved soil 20A, thereby forming a block-shaped improved ground 10A.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] This invention relates to a method for constructing improved ground for soil and sand that is difficult to solidify, such as highly viscous clay, lumpy or consolidated hard clay, weathered rock that has turned into soil or heavily weathered rock, volcanic ash soil, and organic soil. [Background technology]

[0002] As is well known, when the foundation ground for a heavy structure such as a sabo dam is weak, ground improvement work is carried out to build the foundation. In this process, a device with a mixing mechanism is generally inserted into the ground, and cement milk is discharged or sprayed, and the improved ground is built while being mixed by the mixing mechanism.

[0003] In addition, sabo dams are heavy structures, and the foundation ground is subject to a load of approximately 100 to 600 kN / m 2 Many sabo dams have been constructed to date, but new sabo dams are often planned on soft ground, rather than in suitable locations where bedrock is exposed in the foundation ground. Furthermore, because sabo dams are heavy structures, the ground is not necessarily soft, and even hard ground may be subject to ground improvement if it is relatively soft.

[0004] For example, the ground on which a sabo dam is planned is often formed by the movement of soil and sand, and depending on the deposition conditions, particularly soft soil and sand may be deposited. Furthermore, in volcanic regions, when sabo dams are planned on ground originating from volcanic ashfall, depending on the composition of the volcanic ash, the target soil may contain compositional factors such as clay or solidification inhibitors (for example, humic acid contained in organic matter or allophane contained in volcanic ash), making it extremely difficult to ensure the specified quality of the improved soil produced using cement or cement-based solidification materials. Furthermore, construction sites for sabo dams may contain rocks with extremely low strength, such as heavily weathered mudstone, making them unsuitable as foundation ground for sabo dams. Clay soil formed before the Pleistocene may also form hard ground. In these cases, the ground is hard and remains lumpy even after excavation, meaning it may not be possible to mix it with a mixing mechanism designed for soft ground, and it may not be possible to create a homogeneous, improved ground.

[0005] In such cases, if you try to solidify the soil with cement or cement-based solidification materials to achieve the required strength, you will have to add a large amount of cement or cement-based solidification materials, or use a special cement, and you may have no choice but to choose a construction method in which all of the soil and sand generated on site is replaced with concrete or replacement materials.

[0006] In such cases, adding large amounts of cement or selecting special materials is not only uneconomical, but if a replacement method is selected, large-scale excavation may be required for replacement (see, for example, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] https: / / hobbystyle-kadoya.jp / blog-7 / Summary of the Invention [Problem to be solved by the invention]

[0008] However, when large-scale excavation is carried out to construct the foundation ground for a dam, a large amount of local soil and sand is generated, requiring a large storage area for the excavated soil.Furthermore, since excavation equipment such as construction machinery must be placed inside the excavated hole, safety measures are required to prevent the excavated hole from collapsing, etc., which is largely irrational.

[0009] The present invention was devised based on this technical background, and aims to provide an improved ground construction method that enables efficient construction of improved ground when constructing the foundation ground for an erosion control dam on soil and sand that does not easily consolidate or hard ground, without requiring extensive, deep excavation or a large soil and sand temporary storage yard. [Means for solving the problem]

[0010] The present invention provides A method for improving ground in ground containing highly cohesive clay, lumpy or consolidated hard clay, weathered rock that has turned into sediment or heavily weathered rock, volcanic ash soil, or organic soil, Excavate the designated area to form a foundation hole. Put earth and sand into the foundation hole. and poured it on top of the backfilled soil. Modification materials including crushed stone, gravel, gravel, sand, riverbed gravel, sandy gravel, gravelly soil, gravelly soil, etc. After laying the modified material, Cement milk or cement and water are added, Soil and sand, modifying material, cement milk or cement and water The mixture is stirred and kneaded to break up the soil lumps and produce improved muddy soil, which is then solidified to form a solidified body, thereby forming improved ground in the form of blocks. It is characterized by the fact that or The muddy improved soil is generated and accumulated in multiple layers to form a mass of muddy improved soil, which then solidifies. It is characterized by the fact that or When forming the foundation hole, the exposed rock or consolidated soil is excavated while being scraped into small pieces. It is characterized by the fact that or When setting up the plots for forming the block-shaped improved ground, According to the depth of the foundation hole, the excavation equipment and mixing means installed outside the foundation hole are set to a range that allows the soil and sand, modifier, cement milk or cement and water in the foundation hole to be mixed from outside the foundation hole, and the peripheral shape of the compartment is set. It is characterized by the fact that or When the improved ground has multiple block-shaped improved ground, Form the next block-shaped improved ground in the area separated from the unsolidified block-shaped improved ground. It is characterized by: [Effects of the Invention]

[0011] The improved ground construction method of the present invention makes it possible to build a foundation ground of a predetermined quality without using large amounts of cement or expensive materials, even with soil and sand that is difficult to solidify, such as highly viscous clay, lumpy hard clay, weathered rock that has turned into sand or heavily weathered rock, volcanic ash soil, and organic soil. Furthermore, by using multiple block-shaped ground improvement works, construction can be carried out without large-scale excavation. Also, Replace All death This reduces the amount of soil and sand that needs to be disposed of. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view illustrating a schematic configuration of a foundation ground for a sabo dam according to an embodiment of the present invention. [Figure 2] FIG. 2 is a front view taken along arrow II in FIG. 1, illustrating the schematic configuration of the foundation ground for a sabo dam according to one embodiment. [Figure 3] This is a conceptual diagram illustrating the general configuration of the improved foundation ground that constitutes the foundation ground for a sabo dam in one embodiment, where (A) is a plan view and (B) is a view taken along the arrows IIIB-IIIB in (A). [Figure 4] This is a diagram explaining the effect of one embodiment of the improved ground construction method, and shows the relationship between the unit cement content in soil and the axial compressive strength at 28 days for each cement-based solidification material. [Figure 5] FIG. 1 is a diagram illustrating the effect of an improved ground construction method according to one embodiment, and shows the relationship between the amount of crushed stone and the axial compressive strength at 28 days. [Figure 6] This is a diagram explaining the effect of one embodiment of the improved ground construction method, and shows the relationship between unit cement content and 28-day axial compressive strength for each amount of crushed stone. [Figure 7] FIG. 1 is a conceptual diagram illustrating the outline of block-shaped improved ground construction using an improved ground construction method according to one embodiment. [Figure 8]FIG. 1 is a conceptual diagram illustrating the construction of multiple blocks of improved ground using an improved ground construction method according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a description will be given of a sabo dam foundation ground and an improved foundation ground according to one embodiment of the present invention with reference to Figs. 1 to 6. Fig. 1 is a plan view illustrating the schematic configuration of a sabo dam foundation ground according to one embodiment of the present invention, and Fig. 2 is a front view shown in arrow II in Fig. 1 illustrating the schematic configuration of the sabo dam foundation ground. Fig. 3 is a conceptual diagram illustrating the schematic configuration of improved foundation ground constituting a sabo dam foundation ground according to one embodiment, with Fig. 3(A) being a plan view and Fig. 3(B) being a view shown in arrow IIIB-IIIB in Fig. 3(A). Figs. 4 to 6 are diagrams illustrating the effects of an improved ground construction method according to one embodiment. In the figure, reference numeral 100 denotes the foundation ground of the sabo dam (improved foundation ground), reference numerals 10, 11, 12, 13, and 14 denote improved foundation ground, and reference numerals 10A, 10B, 10C, 10D, 10E, and 10F denote block-shaped improved ground.

[0014] The improved ground construction method according to one embodiment is a technique for ensuring the strength required for a sabo dam by replacing part or all of the soil and sand generated on-site with modified materials such as crushed stone or high-quality soil.

[0015] The sabo dam foundation ground 100 contains, for example, lumpy clay soil (50% or more of fine particles less than 75 μm), and in addition to being solidified, has high viscosity, and lumps of soil tend to remain when mixed, and the target strength of the mixture (for example, 3000 kN / m 2 ) is difficult to achieve. Specifically, it is constructed on ground consisting of lumpy clay soil with a fine particle content of 90% or more. In addition to ground consisting of lumpy clay soil, the system may also be constructed on soil containing volcanic ash soil that contains solidification inhibitors (for example, humic acid contained in organic matter or allophane contained in volcanic ash), making the improved soil produced using cement or cement-based solidification materials extremely difficult to solidify and making it difficult to ensure the specified quality.

[0016] Furthermore, as shown in Figure 1, the erosion control dam foundation ground 100 comprises five improved foundation grounds 10, 11, 12, 13, and 14 arranged in a substantially straight line in the width direction of the erosion control dam (not shown), and the improved foundation grounds 10, 11, 12, 13, and 14 each comprise a plurality of block-shaped improved grounds that correspond to the sections (designated sections) shown by dashed lines in Figure 1 when viewed in plan. The number and arrangement of the block-shaped improved ground constituting the improved foundation ground 10, 11, 12, 13, 14 may be set arbitrarily, and for example, the improved foundation ground may be composed of one block-shaped improved ground.

[0017] Furthermore, as shown in Figures 1 and 2, the sabo dam foundation ground 100 has, for example, improved foundation ground 10 placed in the center, and improved foundation grounds 11 and 12 placed in this order to the left of improved foundation ground 10 as you face the figures, and improved foundation grounds 13 and 14 placed in this order to the right of improved foundation ground 10. As shown in FIG. 2, the improved foundation grounds 10, 11, 12, 13, and 14 are formed at different heights (altitudes), and the upper surface (improved ground surface) of each of the improved foundation grounds 10, 11, 12, 13, and 14 is formed approximately horizontally.

[0018] For example, as shown in FIG. 3(A), the improved foundation ground 10 includes six (plural) sections (set sections) and corresponding block-shaped improved ground 10A, 10B, 10C, 10D, 10E, and 10F. In addition, each of the block-shaped improved grounds 10A, 10B, 10C, 10D, 10E, and 10F has a rectangular shape with one side measuring 1.0 to 5.0 m (1.0 m or more, 5.0 m or less), and is formed complementarily to adjacent block-shaped improved grounds.

[0019] As shown in Figure 3(B), the block-shaped improved ground 10 is made up of a solidified body 20 formed by pouring soil and sand, crushed stone (modifier), and cement milk (or cement milk and water) into a foundation hole M formed by excavating a set section, stirring and mixing them in the foundation hole M to produce a muddy improved soil aggregate. When forming the muddy improved soil aggregate, the soil and sand, modifier, and cement milk (or cement milk and water) may be poured, stirred, and mixed in predetermined amounts into multiple layers. In addition, when the improved muddy soil is stirred and mixed, the soil clods contained in the soil and sand are crushed by crushed stone, and the content of soil clods larger than 50 mm is low (for example, the rate of soil clods passing through a 50 mm sieve is 70% or more, more preferably 80% or more).

[0020] The mixing ratio of the soil and sand, modifier, and cement milk (or cement milk and water) for producing the improved muddy soil may be set arbitrarily within a range that ensures the target strength. As the soil and sand, for example, locally generated soil and sand, transported soil and sand (for example, purchased soil and sand), and soil and sand that is a mixture of locally generated soil and transported soil and sand may be arbitrarily applied. The modifier may be one or more of crushed stone, gravel, or high-quality soil (gravelly soil consisting of gravel and sand). Gravelly soil is riverbed gravel collected from riverbeds or gravel or sand collected by excavating natural ground.

[0021] Crushed stone is preferably crushed stone for roads (e.g., C-40) as specified in the JIS standard, and gravel or sand with a fine particle content of less than 15% is suitable for gravelly soil. Gravel with a particle size of 5 mm to 5 cm, which is classified as coarse aggregate for ready-mixed concrete, is suitable. Note that gravel that does not fall under the above particle size category is also acceptable as long as the gravel content consisting of coarse aggregate with a particle size of 2 mm or more is greater than the sand content consisting of particles with a particle size of 0.075 to 2 mm.

[0022] Gravelly soil refers to soil and sand that contains more gravel, consisting of coarse aggregate with a particle size of 2 mm or more, than sand, consisting of particles with a particle size of 0.075 to 2 mm. Because it is easy to handle and compact, it can also be called high-quality soil. This gravelly soil can also be used as an improvement material. This gravelly soil is sediment deposited due to mountain collapses, riverbank erosion, debris flows, etc. that have occurred on-site or in the river basin, and it is preferable to use soil that contains more gravel than sand, has a fine particle content of 15% or less, and has been treated to reduce the maximum particle size to 80 mm or less. Furthermore, among gravelly soils, sediment deposited by flowing down local streams or nearby rivers can be called riverbed gravel or riverbed sediments, and these sediments are characterized by the fact that the fine particles have been washed away, giving them a rounded appearance. For riverbed gravel and riverbed sediments, it is preferable to use ones that contain more gravel than sand, with a fine particle content of 15% or less and have been treated to have a maximum particle size of 80 mm or less. The cement milk or the cement milk and water may be used arbitrarily. Steelmaking slag or the like may be added as a modifier.

[0023] The effects of the improved ground construction method according to one embodiment will be described below with reference to FIGS. Figures 4 to 6 illustrate the effects of one embodiment of the improved ground construction method. Figure 4 shows the relationship between unit cement content and 28-day axial compressive strength for soil and sand (0% crushed stone content) for each cement-based solidification material. Figure 5 shows the relationship between crushed stone content and 28-day axial compressive strength. Figure 6 shows the relationship between unit cement content and 28-day axial compressive strength for each crushed stone content. In Figures 5 and 6, the soil and sand (0% crushed stone content) and crushed stone content of 10% and 20% are values obtained using a cement-based solidification material for special soil, and crushed stone content of 30% and 40% are values obtained using a cement-based solidification material for organic soil. The crushed stone content (%) indicates a ratio based on the absolute volume obtained by dividing the weight of crushed stone by its density.

[0024] (1) Unit cement content (kg / m 3 ) and 28-day axial compressive strength (N / m 2) was confirmed using soil and sand (0% crushed stone) for cement-based solidification materials for special soil and organic soil. As a result, as shown in Figure 4, for both cement-based solidification materials for special soil and organic soil, the axial compressive strength at 28 days increases almost linearly as the unit cement content increases, and the axial compressive strength at 28 days increases at a unit cement content of 350 (kg / m 3 ) and the unit cement amount is 250 (kg / m 3 ) the cement-based solidification material for special soil was approximately 1.37 times higher, and the cement-based solidification material for organic soil was approximately 1.59 times higher.

[0025] (2) Next, the unit cement amount is 250 (kg / m 3 ) and axial compressive strength (N / m 2 ) as shown in Figure 5, when the crushed stone amount (%) increases, the axial compressive strength (N / m 2 ) was confirmed to increase. According to Figure 5, the axial compressive strength at 28 days was 1.14 times higher at 10% crushed stone, 1.23 times higher at 20% crushed stone, 2.35 times higher at 30% crushed stone, and 2.83 times higher at 40% crushed stone compared to soil and sand. It was confirmed that an effect was observed even with a crushed stone amount of 10%, but that the effect increased as the amount of crushed stone increased.

[0026] (3) For crushed stone content of 0%, 30%, and 40%, the unit cement content is 200 to 350 (kg / m 3 When we investigated the change in axial compressive strength at 28 days in the concrete, we confirmed that the axial compressive strength at 28 days increased almost linearly with the amount of crushed stone, as shown in Figure 6. On the other hand, the gradient is larger with 40% crushed stone compared to 30% crushed stone, especially with a unit cement content of 200-350 (kg / m 3 ) the difference is large, which is presumably because the increased amount of crushed stone causes the soil clods to become more fragmented, resulting in the production of homogeneous improved soil.

[0027] Next, a method for constructing an improved foundation ground according to one embodiment will be described with reference to Figs. Fig. 7 is a conceptual diagram outlining the construction of block-shaped improved ground by an improved ground construction method according to one embodiment, and Fig. 8 is a conceptual diagram outlining the construction of multiple block-shaped improved ground. In the diagram, symbol M indicates a foundation hole, symbol B indicates a modifying material, symbol G indicates the ground (at the site where the sabo dam is to be constructed), symbol C indicates cement milk, symbol S indicates soil and sand, symbol M indicates a foundation hole, and symbol T indicates a backhoe.

[0028] First, with reference to FIG. 7, an improved foundation ground construction method for forming block-shaped improved ground in a set section will be described. (1) Formation of foundation holes First, a section is set up in the lumpy clay soil G where block-shaped improved ground will be formed. When setting up the plots for the block-shaped improved ground, a peripheral shape is set up that allows equipment such as a backhoe T used for excavation and mixing to be installed outside the foundation hole M, taking into account the depth of the foundation hole M that will form the block-shaped improved ground. If the plot is rectangular, for example, it is set up to have plan dimensions of approximately 1.0 to 5.0 m square. Next, as shown in Figure 7(A), the set area is excavated with a backhoe T to a predetermined depth to form a foundation hole M. Any lumps of soil, rocks, or consolidated soil and sand that are exposed during the excavation are scraped off and broken into small pieces as much as possible. Specifically, the block sections (areas) that are divided into sections on the construction site plane are excavated to a specified depth. Here, exposed rock refers to soft rock that can be scraped away with a backhoe (for example, sedimentary rocks such as mudstone, sandstone, tuff, and conglomerate that have been heavily weathered or weathered and are classified as Class D in the rock classification system, and granite), and consolidated sediment refers to, for example, hard clayey soil with an N value of 10 or more that was formed before the Pleistocene epoch, or heavily weathered or weathered mudstone.

[0029] (2) Putting soil, crushed stone, and cement milk into the foundation hole Next, as shown in Figure 7(B), a backhoe T or a backhoe T equipped with a mixing bucket is used to load predetermined amounts of weighed soil S, crushed stone (modifier) B, and cement milk C in that order. That is, soil is loaded first, followed by crushed stone (modifier) B and cement milk C, in that order. The amounts of soil S, crushed stone (modifier) B, and cement milk C to be added are set based on the amount of crushed stone or high-quality soil determined in advance through a mixing test. The thickness of the earth and sand to be added may be set arbitrarily, but the earth and sand S, crushed stone (modifier) B, and cement milk C are added to a thickness of, for example, about 1.0 m to 1.5 m. The method for measuring crushed stone (modified material) B or good quality soil at the site is to measure the mass of soil S to be put into the bucket in advance, and then convert the volume to be put in from the density of the soil, making it possible to set the specified ratio based on the number of buckets. The cement milk may be supplied by a grout pump from a nearby slurry plant. When adding cement and water, bags of cement may be transported to the site by a backhoe T and pumped up from a nearby water tank. Also, when using soil and sand generated on-site, if the soil and sand contains obstacles such as organic matter (trees, etc.) or boulders, these will be removed.

[0030] (3) Generate muddy improved soil in the foundation hole Next, as shown in Figure 7(C), the added soil S, crushed stone (modifier) B, and cement milk C (or cement and water) are stirred and mixed in the foundation hole M using a backhoe T equipped with a mixing bucket, and the crushed stone (modifier) B is used to crush and fragment the soil clods contained in the soil, producing a homogeneous muddy improved soil 20A with few soil clods larger than 50 mm. The layer of muddy improved soil produced in one go is preferably in the range of 0.5 to 1.5 m.

[0031] (4) Formation of aggregates of improved muddy soil The above steps (2) and (3) are repeated to form an aggregate 20B of improved muddy soil in the foundation hole M, as shown in FIG. 7(D).

[0032] (5) Formation of block-shaped improved ground Next, as shown in FIG. 7(E), the muddy improved soil aggregate 20B is solidified to form a solidified body 20, thereby forming improved ground 10A.

[0033] Next, an outline of the improved ground construction method for constructing a foundation for a sabo dam with multiple block-shaped improved ground will be described with reference to Figure 8. Figure 8 shows an example of constructing a block-shaped improved ground 10B adjacent to the block-shaped improved ground 10A shown in Figure 3(A). When constructing the block-shaped foundation ground in the next section, it is possible to form undisturbed improved ground by avoiding the blocks adjacent to the blocks before solidification. In FIG. 8, for the sake of convenience, a case will be described in which a block-shaped foundation ground 10A is assumed to have solidified and a block-shaped foundation ground 10B is constructed in an adjacent section.

[0034] (1) First, as shown in FIG. 8(A), a section of the block-shaped improved ground 10B is excavated with a backhoe T to form a foundation hole M. When forming a foundation hole M adjacent to an already constructed block-shaped improved ground 10A, the finished state of the block-shaped improved ground 10A is checked. Fig. 8(A) shows the case where an adjacent block-shaped improved ground 10B is constructed following a block-shaped improved ground 10A, but the block-shaped improved ground constructed following the block-shaped improved ground 10A may be set arbitrarily, and any of the block-shaped improved grounds 10C to 10F shown in Fig. 3(A) may be constructed. For example, when constructing block-shaped improved ground 10C to 10E that is not in contact with the block-shaped foundation ground 10A, it is possible to excavate the foundation hole M even before the block-shaped improved ground 10A has solidified. It may be optional whether or not the newly constructed block-shaped improved ground is adjacent to the existing block-shaped improved ground. In addition, when forming a foundation hole M adjacent to an existing block-shaped foundation ground, the condition of the existing block-shaped foundation ground 10 is checked.

[0035] (2) Next, as shown in Figure 8(B), soil S, crushed stone (modifier) B, and cement milk C are poured into the foundation hole M.

[0036] (3) Next, as shown in Figure 8(C), a backhoe T equipped with a mixing bucket is used to stir and mix the soil in the foundation hole M, and crushed stone (modifying material) B is used to break down and fragment the soil lumps contained in the soil, producing a homogeneous mud-like improved soil 20A with few soil lumps larger than 50 mm.

[0037] (4) Next, as shown in Figure 8(D), the production of muddy improved soil 20A is repeated using the steps (2) and (3) above to form a muddy improved soil aggregate 20B for creating block-shaped improved ground.

[0038] (5) Next, the muddy improved soil aggregate 20B is solidified to form improved soil (solidified body) 20, thereby constructing block-shaped improved ground 10B as shown in FIG. 8(E). The above items (2) to (5) are the same as those explained in FIG. 7, so the explanation will be omitted.

[0039] According to one embodiment of the erosion control dam foundation ground 100, block-shaped improved ground 10A, 10B, and erosion control dam foundation ground construction method, improved foundation ground with a predetermined strength can be efficiently constructed on ground G containing clod clay soil without using large amounts of cement or expensive materials. Furthermore, since no large-scale excavation is required, a large excavated soil storage area is not required, and the amount of waste soil to be disposed of can be reduced. In addition, since there is no need to place construction machinery or personnel inside the excavation hole, there is little possibility of safety problems occurring. Furthermore, since foundation holes M are formed for each set section and block-shaped improved ground 10A...10F is constructed, it is possible to excavate to the minimum depth required.

[0040] In addition, since the local soil can be visually inspected during the process of excavating the foundation hole M and discharging the soil, it is easy to remove obstacles such as organic matter (e.g., trees) contained in the soil, and by replacing some or all of the poor soil, removing solidification inhibitors, and replacing them with modifying materials, it is possible to form improved ground of the desired quality. As a result, it is possible to efficiently obtain a predetermined strength even with soil and sand in the ground that is difficult to solidify.

[0041] Furthermore, even if the excavated soil contains clumps of clay, when the soil, modifier, cement milk or cement and water are mixed, the clumps of clay are crushed with the modifier to produce a homogeneous, muddy improved soil, making it possible to produce improved soil with properties that make it easy to solidify the soil generated on-site. Furthermore, if lumps of soil, rocks, or consolidated soil and sand are discovered during the creation of the foundation hole, they can be cut into small pieces as needed while excavating, which will increase the amount of crushed stone obtained on-site and reduce the amount of surplus soil to be disposed of.

[0042] The present invention is not limited to the above-described embodiment, and various modifications can be made thereto. For example, in the above embodiment, the case where the sabo dam foundation ground 100 is constructed on a ground of lumpy clay soil with a fine particle content of 90% has been described, but it may also be applied to a ground of lumpy clay soil with a fine particle content of 50% or more. In addition, instead of lumpy clayey soil, the present invention may be applied to soil such as volcanic ash soil, which contains solidification inhibitors (for example, humic acid contained in organic matter or allophane contained in volcanic ash) and therefore makes it difficult for improved soil produced with cement or cement-based solidification materials to solidify, as well as soil where it is difficult to ensure the specified quality due to soil and sand generated on-site. It may also be applied to hard ground consisting of lumpy hard clay soil, weathered rock that has turned into sand, or heavily weathered rock, which cannot be worked on using general soft ground countermeasure methods. Furthermore, when applying this method to soil containing solidification inhibitors, it is preferable to replace some or all of the on-site soil excavated when digging the foundation hole with good quality soil.

[0043] Furthermore, in the above embodiment, the case where the erosion control dam foundation ground 100 comprises five (plural) improved foundation grounds 10-14 has been described, but the number of improved foundation grounds constituting the erosion control dam foundation ground 100 may be set arbitrarily, and for example, the erosion control dam foundation ground may be constituted by one improved foundation ground.

[0044] In the above embodiment, the improved foundation ground 10 is constructed from block-shaped improved ground 10A...10F formed into six (multiple) rectangular sections in a plan view. However, the shape of the improved foundation ground can be set arbitrarily. For example, the improved foundation ground may be constructed from a single block-shaped improved ground, or may be configured to include sections set in any shape, not limited to a rectangular shape in a plan view, such as a triangle, trapezoid, or trapezoid. Furthermore, the dimensions of one side of the block-shaped improved ground and the depth of the foundation hole M may be set to the same or different dimensions arbitrarily.

[0045] Furthermore, in the above embodiment, the case where crushed stone is used as the modifier is described, but the modifier is not limited to crushed stone and can be set arbitrarily, and it is sufficient if it contains any of high-quality soil selected from crushed stone, gravel, sand, gravel, riverbed gravel, sandy gravel soil, gravelly soil, etc., and it may also contain steelmaking slag, etc. as part of the modifier. In addition, in the above embodiment, a case has been described in which soil and sand, a modifying material, and cement milk are stirred to produce muddy improved soil, but cement and water may be used instead of cement milk.

[0046] Furthermore, when constructing an improved foundation ground using multiple block-shaped improved ground (solidified bodies), it is not necessary to set the same mixing ratio of soil, modifier, cement milk, or cement and water for all block-shaped improved ground (solidified bodies); any mixing ratio (composition) can be used for each block-shaped improved ground (solidified body).

[0047] In the above embodiment, the block-shaped improved ground is formed from improved soil produced by mixing, for example, soil and sand, crushed stone (modifier), and cement milk. However, in addition to or instead of crushed stone, the improved ground may contain at least one of high-quality soil and sand such as gravel, pebbles, sandy gravel, riverbed gravel, sandy gravel soil, and gravelly soil, or these may be mixed with modifiers such as steelmaking slag. Also, cement and water may be used instead of cement milk. In addition, with regard to soil and sand, in addition to or instead of the locally generated soil and sand excavated from the foundation hole M, soil and sand from other areas than the planned site for construction of improved ground (for example, purchased soil and sand), or soil and sand from locally generated soil from which organic matter such as trees and boulders have been removed, may be used.

[0048] In addition, in the above embodiment, the excavation of the foundation hole and the generation of the muddy improved soil are described using a backhoe T, but the backhoe T is only one example of an excavation means, and the foundation hole M may be excavated by other excavation means, or the muddy improved soil 20A may be generated by other mixing means, etc.

[0049] Furthermore, in the above embodiment, for example, a case where one side of the foundation hole M is 1.0 to 5.0 m has been described, but the size of the block-shaped improved ground and the depth of the foundation hole M may be set arbitrarily, and the planar peripheral shape (e.g., triangular, rectangular, trapezoidal, polygonal, etc.) and dimensions of the block-shaped improved ground (foundation hole M) may be set within a range that allows excavation from outside the foundation hole M and mixing of soil, modifier, and cement milk depending on the excavation equipment and mixing / stirring means installed in the ground G.

[0050] In addition, in the above embodiment, the case where adjacent block-shaped foundation ground 10B is formed following block-shaped foundation ground 10A has been described, but non-adjacent block-shaped foundation grounds 10C, 10D, and 10E may also be formed following block-shaped foundation ground 10A, in which case block-shaped foundation grounds 10C, 10D, and 10E can be constructed from the edges around the excavation hole without waiting for block-shaped foundation ground 10A to solidify. [Explanation of symbols]

[0051] G Ground B Crushed stone (modifier) C Cement milk S. Soil M Foundation hole T Backhoe 100 Erosion control dam foundation ground (improved foundation ground) 10, 11, 12, 13, 14 Improved foundation ground 10A, 10B, 10C, 10D, 10E, 10F Block-shaped improved ground 20 Improved soil (solidified body) 20A Muddy improved soil 20B (mud-like improved soil) aggregate

Claims

1. A method for improving ground in ground containing highly viscous clay, lumpy or consolidated hard clay, weathered rock that has turned into sediment or heavily weathered rock, volcanic ash soil, or organic soil, Excavate the designated area to form a foundation hole. The soil and sand, and a modifying material containing any of high-quality soil such as crushed stone, gravel, pebbles, sand gravel, riverbed sand gravel, sandy gravel soil, and gravelly soil, and cement milk or cement and water are poured into the foundation hole, and these are stirred and kneaded to generate muddy improved soil while breaking up the soil lumps, and the muddy improved soil is solidified to form a solidified body, thereby forming a block-shaped improved ground. A method for constructing improved ground.

2. When generating muddy improved soil in the foundation hole, soil and sand are poured in, and a modifier is laid on the backfilled soil and sand, and then cement milk or cement and water are added, and the soil and sand, the modifier, and the cement milk or cement and water are stirred and kneaded.

2. The method for constructing improved ground according to claim 1.

3. The muddy improved soil is generated and accumulated in multiple layers to form a mass of muddy improved soil, which then solidifies.

3. A method for constructing improved ground according to claim 1 or 2.

4. When forming the foundation hole, the exposed rock or consolidated soil is excavated while being scraped into small pieces.

2. The method for constructing improved ground according to claim 1.

5. When setting up the plots for forming the block-shaped improved ground, In relation to the depth of the foundation hole that will form the block-shaped improved ground, the equipment used for excavation and mixing will be installed outside the foundation hole to set up a peripheral area where construction can be carried out.

3. A method for constructing improved ground according to claim 1 or 2.

6. When the improved ground has multiple block-shaped improved ground, Form the next block-shaped improved ground in the area separated from the unsolidified block-shaped improved ground.

3. A method for constructing improved ground according to claim 1 or 2.

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