Improved ground construction method

Abstract

To provide an improved ground construction method capable of constructing an improved ground efficiently without requiring extensive and deep excavation or a large temporary soil storage yard when constructing a foundation for an erosion control dam on soil that does not easily harden. [Solution] The present invention is an improved ground construction method characterized by setting a section in ground G containing highly viscous clayey soil, lumpy hard clayey soil, weathered rock that has turned into sand or heavily weathered rock, volcanic ash soil, and organic soil, excavating the set section to form a foundation work hole M, pouring, stirring, and kneading soil S, crushed stone B containing at least any of crushed stone, gravel, gravel, sand gravel, riverbed sand gravel, sand gravel soil, and gravel soil, and cement milk C into the foundation work hole M to generate muddy improved soil 20A, and forming a solidified body 20 by solidifying an aggregate 20B of the muddy improved soil by accumulating a predetermined amount of the muddy improved soil 20A, thereby forming a block-shaped improved ground 10A.

Description

[Technical field]

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

[0002] As is well known, when the foundation of a heavy structure such as a sabo dam is weak, ground improvement work is carried out to build the foundation. In general, a device with a mixing mechanism is 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 resistance 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 at the base. Furthermore, because sabo dams are heavy structures, the ground is not necessarily soft; 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, there may be cases where particularly soft soil and sand have accumulated. Furthermore, in volcanic regions, when sabo dams are planned on ground originating from volcanic ashfall, depending on the components 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 and allophane contained in volcanic ash), making it extremely difficult to ensure the specified quality when the improved soil is produced using cement or cement-based solidification materials. Furthermore, in some cases, the construction site for a sabo dam contains ground that is extremely weak in terms of rock properties, such as strongly weathered mudstone, making it unsuitable as the foundation for a sabo dam. In addition, clayey soil formed before the Pleistocene Epoch may form a hard foundation. In this case, the ground is hard and becomes lumpy even when excavated, so it may not be possible to mix it with a mixing mechanism designed for soft ground, and it may not be possible to build a homogeneous improved ground.

[0005] In such cases, if one tries to achieve a certain level of strength by solidifying the soil with cement or cement-based solidification materials, it becomes necessary to add large amounts of cement or cement-based solidification materials or to use special cement. In addition, it may be necessary 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, not only is it uneconomical to add large amounts of cement or select special materials, 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 for a dam, a large amount of local soil is generated, requiring a large storage area for the excavated soil. In addition, the need to place excavation equipment such as construction machinery in the excavated hole necessitates safety measures against the collapse of the excavated hole, which is largely irrational.

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

[0010] The present invention relates to A method for improving ground containing any of highly viscous clay soil, lumpy or consolidated hard clay soil, weathered rock that has turned into sand or highly weathered rock, volcanic ash soil, and organic soil, comprising: Excavate the designated area to form a foundation hole, Put soil and sand into the foundation hole. and poured it on top of the backfilled soil. Modification materials that include crushed stone, gravel, gravel, sand, riverbed gravel, sandy gravel, gravelly soil, gravelly soil, etc. After laying the modifier, Cement milk or cement and water are added, Soil, modifier, cement milk or cement and water The mixture is stirred and kneaded to break up the soil lumps and generate improved soil in a muddy state, which is then solidified to form a solidified body, thereby forming improved ground in a block form. It is characterized by: or The muddy improved soil is generated in multiple layers and accumulated to form a muddy improved soil aggregate that is then solidified. It is characterized by: or When forming the foundation hole, the exposed rock or consolidated soil is excavated while being scraped into small pieces. It is characterized by: or When setting up the plots for forming the block-shaped improved ground, According to the depth of the foundation hole, the excavation device and the mixing means installed outside the foundation hole are set to a range where the soil and sand, the modifier, and the cement milk or the cement and water in the foundation hole can be mixed from outside the foundation hole, and the peripheral shape of the section is set. It is characterized by: 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: Effect of the Invention

[0011] According to the method for constructing improved ground of the present invention, it is possible to construct a foundation ground of a predetermined quality without using a large amount of cement or expensive materials, even with soil that is difficult to harden, such as highly viscous clay soil, lumpy hard clay soil, weathered rock that has turned into sand or highly weathered rock, volcanic ash soil, organic soil, etc. Also, by constructing multiple block-shaped soil improvement works, construction can be carried out without large-scale excavation. Also, Replace All death This reduces the amount of soil to be disposed of. [Brief description 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. [Diagram 2] FIG. 2 is a front view taken along the arrow II in FIG. 1 , illustrating a schematic configuration of a foundation ground for a sabo dam according to one embodiment. [Diagram 3] FIG. 1 is a conceptual diagram illustrating the general configuration of the improved foundation ground that constitutes the foundation ground of a sand-control 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] FIG. 1 is a diagram for explaining the effect of an improved ground construction method according to one embodiment, and shows the relationship between the unit cement content in soil and the 28-day axial compressive strength for each cement-based solidification material. [Diagram 5] FIG. 1 is a diagram for explaining the effect of an improved ground construction method according to one embodiment, and is a diagram showing the relationship between the amount of crushed stone and the axial compressive strength at 28 days. [Figure 6] FIG. 1 is a diagram for explaining the effect of an improved ground construction method according to one embodiment, 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 for explaining 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 outline of construction of multiple block-shaped improved ground using an improved ground construction method according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the foundation ground for an erosion-control dam and the improved foundation ground according to one embodiment of the present invention will be described with reference to Fig. 1 to Fig. 6. Fig. 1 is a plan view for explaining the schematic configuration of the foundation ground for an erosion-control dam according to one embodiment of the present invention, and Fig. 2 is a front view shown in arrow II in Fig. 1 for explaining the schematic configuration of the foundation ground for an erosion-control dam. Fig. 3 is a conceptual diagram for explaining the schematic configuration of the improved foundation ground constituting the foundation ground for an erosion-control dam 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 views for explaining the effect of the improved ground construction method according to one embodiment. In the figure, reference numeral 100 denotes the foundation ground of a 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 generated on-site with a modifying material such as crushed stone or good quality soil.

[0015] The foundation ground 100 for the erosion control dam contains, for example, lumpy clayey soil (50% or more fine particles less than 75 μm), which is solidified and has high viscosity. Therefore, 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 made of clod-like clay soil with fine particles of 90% or more. In addition to ground consisting of lumpy clay soil, the system may also be constructed on ground that contains volcanic ash soil and contains solidification inhibitors (for example, humic acid contained in organic matter and allophane contained in volcanic ash) that make the improved soil produced with cement or cement-based solidification materials extremely difficult to solidify and make it difficult to ensure the specified quality.

[0016] 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 each of the improved foundation grounds 10, 11, 12, 13, and 14 comprises a plurality of block-shaped improved grounds which correspond, when viewed in a plan view, to the sections (designated sections) shown by dashed lines in Figure 1. The number and arrangement of the block-shaped improved ground constituting the improved foundation grounds 10, 11, 12, 13, and 14 may be set arbitrarily, and for example, the improved foundation ground may be composed of a single block-shaped improved ground.

[0017] Furthermore, as shown in Figures 1 and 2, the foundation ground 100 of the erosion-control dam has, for example, an improved foundation ground 10 located in the center, and improved foundation grounds 11 and 12 located, in that order, to the left of the improved foundation ground 10 as one faces the figures, and improved foundation grounds 13 and 14 located, in that order, on the right side. 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, the improved foundation ground 10 includes block-shaped improved ground 10A, 10B, 10C, 10D, 10E, and 10F corresponding to six (plural) sections (designated sections), as shown in FIG. 3(A). In addition, each of the block-shaped improved grounds 10A, 10B, 10C, 10D, 10E, and 10F has one side of a rectangle set to 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 Fig. 3(B), the block-shaped improved ground 10 is composed of a solidified body 20 formed by pouring soil, 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 muddy improved soil. When forming the muddy improved soil, the soil, 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 muddy improved 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 passage rate of soil clods through a 50 mm sieve is 70% or more, and more preferably 80% or more).

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

[0021] Crushed stone is preferably crushed run (e.g. C-40) as specified by the JIS standard for road crushed stone, gravel or sand with a fine particle content of less than 15% is suitable for gravelly soil, and gravel with a particle size of 5mm to 5cm, which is classified as coarse aggregate for ready-mix concrete, is suitable. Note that gravel that does not fall under the above particle sizes may be used as long as it contains more gravel consisting of coarse aggregate with a particle size of 2mm or more than the sand consisting of a particle size of 0.075 to 2mm.

[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, and can be called good quality soil because it is easy to handle and compact. Gravelly soil can also be used as a modifier. This gravelly soil is sediment deposited due to mountain collapse, riverbank erosion, debris flow, etc. that occurred at the site or in the watershed, and it is preferable to use soil that has a higher gravel content 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. Among gravelly soils, sediment that has accumulated after flowing down a local stream or a nearby river can be called riverbed gravel or riverbed sediment, and is characterized by its rounded shape due to the fine particles being washed away. For riverbed gravel and riverbed sediments, it is preferable to use ones that have a higher gravel content than sand, with a fine particle content of 15% or less and have been treated to reduce the maximum particle size to 80 mm or less. In addition, the cement milk or the cement milk and water may be used as desired. In addition, steel slag or the like may be added as a modifier.

[0023] Hereinafter, the effects of the improved ground construction method according to one embodiment will be described with reference to Figs. 4 to 6 are diagrams for explaining the effect of the improved ground construction method according to one embodiment, in which Fig. 4 shows the relationship between the unit cement amount and the axial compressive strength at 28 days for each cement-based solidification material in soil (0% crushed stone amount), Fig. 5 shows the relationship between the crushed stone amount and the axial compressive strength at 28 days, and Fig. 6 shows the relationship between the unit cement amount and the axial compressive strength at 28 days for each crushed stone amount. In Figs. 5 and 6, the soil (0% crushed stone amount), the crushed stone amount of 10% and 20% are values ​​using a cement-based solidification material for special soil, and the crushed stone amount of 30% and 40% are values ​​using a cement-based solidification material for organic soil. The crushed stone amount (%) indicates a ratio based on the absolute volume obtained by dividing the weight of crushed stone by the density.

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

[0025] (2) Next, the unit cement amount is 250 (kg / m 3 ) and 28-day axial compressive strength (N / m 2 ), as shown in Figure 5, the axial compressive strength at 28 days (N / m 2 ) was confirmed to increase. According to Figure 5, the axial compressive strength at 28 days was 1.14 times that of soil and sand when the amount of crushed stone was 10%, 1.23 times when the amount of crushed stone was 20%, 2.35 times when the amount of crushed stone was 30%, and 2.83 times when the amount of crushed stone was 40%. 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) In addition, for the crushed stone amount of 0%, 30%, and 40%, the unit cement amount is 200 to 350 (kg / m 3 When we investigated the change in axial compressive strength at 28 days in the concrete, it was 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 slope is larger with 40% crushed stone compared to 30% crushed stone, especially with a unit cement content of 200-350 (kg / m 3 ) is thought to be because the increase in the amount of crushed stone leads to the fragmentation of the soil masses, 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 for explaining the outline of construction of a block-shaped improved ground by the improved ground construction method according to one embodiment, and Fig. 8 is a conceptual diagram for explaining the outline of construction of a plurality of block-shaped improved ground. In the figures, the symbol M indicates a foundation hole, the symbol B indicates a modifier, the symbol G indicates the ground (of the site where the sabo dam is to be constructed), the symbol C indicates cement milk, the symbol S indicates soil, the symbol M indicates a foundation hole, and the 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 for forming a block-shaped improved ground is set in the lumpy clay soil G. When setting up the plot of block-shaped improved ground, a plot with a peripheral shape is set up that allows equipment such as a backhoe T used for excavation and mixing to be placed outside the foundation hole M in relation to the depth of the foundation hole M that will form the block-shaped improved ground. For example, if the plot is rectangular, it is set to a planar dimension of approximately 1.0 to 5.0 m square. Next, as shown in FIG. 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 cut into small pieces as much as possible. Specifically, the block sections (areas) that are divided on the construction site plane are excavated to a specified depth. Here, exposed rock refers to soft rock that can be cut up with a backhoe (for example, sedimentary rocks such as mudstone, sandstone, tuff, and conglomerate that have been strongly weathered or classified as Class D in the rock classification system, and granite), and consolidated soil refers to, for example, hard clayey soil with an N value of 10 or more that was formed before the Pleistocene Epoch, and strongly weathered or weathered mudstone.

[0029] (2) Pouring soil, crushed stone, and cement milk into the foundation hole Next, as shown in Fig. 7(B), a backhoe T or a backhoe T equipped with a mixing bucket is used to pour the measured amounts of soil S, crushed stone (modifier) ​​B, and cement milk C in that order. That is, soil is poured first, and then crushed stone (modifier) ​​B and cement milk C are poured on top of it 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 good quality soil determined in advance through a mixing test. The thickness of the soil and sand to be added may be set arbitrarily, but the soil 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 (improved 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 the volume to be put in can be converted from the density of the soil, making it possible to obtain 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. In addition, when using soil generated on-site, if the soil 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 Fig. 7(C), the input soil S, crushed stone (modifier) ​​B, and cement milk C (or cement and water) are stirred and mixed in the foundation hole M by a backhoe T equipped with a mixing bucket, and the crushed stone (modifier) ​​B crushes and fragments the soil clods contained in the soil, producing homogeneous muddy improved soil 20A with few soil clods of 50 mm or more. 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 muddy soil The above steps (2) and (3) are repeated to form a muddy improved soil aggregate 20B 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 mass 20B is solidified to form a solidified body 20, thereby forming the improved ground 10A.

[0033] Next, an outline of an improved ground construction method for constructing a foundation for a sabo dam with multiple block-shaped improved ground will be described with reference to Fig. 8. Fig. 8 shows an example of constructing an adjacent block-shaped improved ground 10B following the block-shaped improved ground 10A shown in Fig. 3(A). When constructing the block-shaped foundation ground in the next section, construction is performed while avoiding adjacent blocks of the blocks before solidification, making it possible to form improved ground without disturbance. In FIG. 8, for convenience of explanation, a case will be explained 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 condition of the block-shaped improved ground 10A is checked. Fig. 8(A) shows the case where a block-shaped improved ground 10B adjacent to the block-shaped improved ground 10A is constructed, 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 grounds 10C to 10E that are 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 solidifies. It may be decided at will 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 FIG. 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 up and fragment the soil clods contained in the soil, producing a homogeneous muddy improved soil 20A containing few clods larger than 50 mm.

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

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

[0039] According to one embodiment of the foundation ground 100 for an erosion-control dam, the block-shaped improved ground 10A, 10B, and the method for constructing the foundation ground for an erosion-control dam, an improved foundation ground with a predetermined strength can be efficiently constructed on ground G having a soil quality including clod clay soil, without using a large amount of cement or expensive materials. In addition, since no large-scale excavation is required, no large excavated soil storage area is 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, the possibility of safety problems occurring is low. Also, 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 required depth.

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

[0041] Furthermore, even if the excavated soil contains lumps of clayey soil, when the soil, modifier, cement milk or cement and water are mixed, the lumps of clayey soil are crushed with the modifier to produce a homogeneous mud-like improved soil, so that the soil generated on-site can be made into improved soil with properties that make it easy to solidify. In addition, if soil lumps, rocks, or consolidated soil and sand are found during the formation of the foundation hole, they will be cut into small pieces as necessary 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. For example, in the above embodiment, the case where the sabo dam foundation ground 100 is constructed on a lumpy clay ground with 90% fine particles has been described, but the present invention may be applied to a lumpy clay ground with 50% or more fine particles. In addition, instead of lumpy clayey ground, the present invention may be applied to ground such as volcanic ash soil, which contains solidification-inhibiting substances (for example, humic acid contained in organic matter or allophane contained in volcanic ash) and therefore is difficult to solidify improved soil produced with cement or cement-based solidification materials, as well as soil where it is difficult to ensure the specified quality due to soil and sand generated on-site. The present invention 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 is impossible to work on using typical soft ground countermeasure methods. In addition, 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 or sand.

[0043] In addition, in the above embodiment, a case has been described in which the erosion-control dam foundation ground 100 comprises five (multiple) improved foundation grounds 10-14, 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, for example, the case where the improved foundation ground 10 is constructed from block-shaped improved ground 10A...10F formed into six (multiple) rectangular sections in a plan view has been described, but the shape of the improved foundation ground can be set arbitrarily. For example, the improved foundation ground may be constituted by one block-shaped improved ground, or may be constituted by including sections set in any shape, such as a triangle, a trapezoid, a trapezoid, etc., without being limited to a rectangle in a plan view. In addition, the dimensions of one side of the block-shaped improved ground and the depth of the foundation hole M may be set arbitrarily to be the same or different dimensions.

[0045] In addition, in the above embodiment, the case where crushed stone is used as the modifier is described, however, the modifier is not limited to crushed stone and can be set arbitrarily, and it is sufficient that the modifier contains any selected from among good quality soil such as crushed stone, gravel, sand gravel, riverbed gravel, sand gravel soil, gravelly soil, etc., and steel slag, etc. may be contained as part of the modifier. In addition, in the above embodiment, a case has been described in which soil and sand, a modifier, and cement milk are mixed together 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 mixing ratio of soil, modifier, cement milk, or cement and water for all of the block-shaped improved ground (solidified bodies) to the same ratio; any mixing ratio (composition) may be used for each block-shaped improved ground (solidified body).

[0047] In the above embodiment, the block-shaped improved ground is formed of improved soil produced by mixing, for example, soil and sand, crushed stone (modifier), and cement milk, but in addition to or instead of crushed stone, at least one of high-quality soil and sand such as gravel, pebbles, sandy gravel, riverbed gravel, sandy gravel soil, and gravelly soil may be included, or a modifier such as steel slag may be mixed with these. Also, cement and water may be used instead of cement milk. In addition, with regard to the soil, in addition to or instead of the locally generated soil excavated from the foundation hole M, soil from a site other than the planned site for construction of the improved ground (e.g. purchased soil) or 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 case where the backhoe T is used to excavate the foundation work hole and generate the muddy improved soil is described, but the backhoe T is only one example of an excavation means, and the foundation work hole M may be excavated by other excavation means, or the muddy improved soil 20A may be generated by other mixing means, etc.

[0049] In addition, in the above embodiment, for example, a case where one side of the foundation work 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 work 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 work hole M) may be set to a range within which excavation and mixing of soil, modifier, and cement milk are possible from outside the foundation work hole M depending on the excavation equipment and mixing / stirring means installed in the ground G.

[0050] In addition, in the above embodiment, a case has been described in which adjacent block-shaped foundation ground 10B is formed following block-shaped foundation ground 10A, 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 Sand-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 containing any of highly viscous clay soil, lumpy or consolidated hard clay soil, weathered rock that has turned into sand or highly weathered rock, volcanic ash soil, and organic soil, comprising: Excavate the designated area to form a foundation hole, Soil is poured into the foundation hole, and a modifier containing any of good quality soil such as crushed stone, gravel, gravel, sand gravel, riverbed gravel, sandy gravel soil, gravelly soil, etc. is laid on the backfilled soil, and after the modifier has been laid, cement milk or cement and water are poured in, and the soil, modifier, and cement milk or cement and water 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. The muddy improved soil is generated in multiple layers and accumulated to form a muddy improved soil aggregate that is then solidified.

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

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

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

4. When setting up the plots for forming the block-shaped improved ground, According to the depth of the foundation hole, the excavation device and the mixing means installed outside the foundation hole are set to a range where the soil and sand, the modifier, and the cement milk or the cement and water in the foundation hole can be mixed from the outside of the foundation hole, and the peripheral shape of the section is set.

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

5. 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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