Site Improvement Methods

Abstract

To provide a ground improvement method capable of maintaining the effect of reducing ground displacement even when the ground to be improved is made of particularly high-adhesion clayey soil. [Solution] In a ground improvement method that creates a cylindrical improvement body in the ground to be improved, the range of water content at which the soil discharge rate is appropriate is standardized based on the water content of the soil of the ground, taking into account the amount of drilling water during drilling, and the amount of drilling water can be set. The water content of the soil of the ground, taking into account the amount of drilling water during drilling, can also be normalized by the liquid limit of the soil of the ground, and the normalized water content (W / W L ) = 0.7 to 1.3, preferably normalized water content (W / W L The water content range may be based on a range of 0.8 to 1.2.

Description

[Technical field]

[0001] The present invention relates to a ground improvement method, and more specifically, to a ground improvement method for constructing a cylindrical improved body in ground to be improved. [Background technology]

[0002] Conventionally, there has been a ground improvement method (see, for example, Patent Document 1) in which a drilling blade at the end of a single-tube injection rod is used to drill a hole in the ground to a planned depth, and the outside of the stirring blade is cut and mixed with the energy of the solidification material slurry that is injected at high pressure through the injection rod into the ground, while a soil pushing-up disk installed close to the top of the solidification material slurry injection part of the injection rod pushes up the disturbed soil near the solidification material slurry injection port, forming a void below the soil pushing-up disk, and the mixed soil mixed with the solidification material slurry is absorbed into the void, creating a cylindrical improvement body in the ground to be improved, and preventing displacement and movement into the surrounding ground. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-120819 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the ground improvement method, drilling water is added when drilling holes, but if too much water is added, the soil in the drilled hole will exceed its liquid limit and turn into muddy water, reducing the effect of pushing up the disturbed soil with the soil push-up disk when constructing the improved body. Conversely, if too little water is added when drilling, the disturbance of the ground in the drilled hole will be reduced and the pull-out resistance will increase, reducing both the effect of pushing up the disturbed soil due to the increase in internal pressure in the ground caused by the increase in the volume of the ground due to the injection of solidification material slurry, and the effect of pushing up the disturbed soil with the soil push-up disk. Therefore, if water is not added appropriately when drilling, the soil removal rate will decrease and the effect of reducing ground displacement will be reduced.

[0005] With conventional ground improvement methods, especially when the ground to be improved is composed of highly cohesive clay soil, the resistance of the agitator increases when drilling and penetrating the ground to be improved. This causes the agitator to rotate insufficiently, resulting in less disturbance of the ground. Alternatively, more water than necessary may be added to reduce resistance during penetration, causing the ground to turn into muddy water, which reduces the upward thrust effect of the blade, lowers the soil removal rate, and reduces the effect of reducing ground displacement.

[0006] Therefore, an object of the present invention is to provide a ground improvement method capable of maintaining the effect of reducing ground displacement even when the ground to be improved is composed of particularly high-cohesive clay soil. [Means for solving the problem]

[0007] The present invention is a ground improvement method in which a drilling blade at the tip of a single-tube injection rod is used to drill holes in the ground to a planned depth, and the outside of the agitator blade is cut and mixed with the energy of the solidification material slurry injected into the ground through the injection rod at high pressure, while a soil push-up disk installed adjacent to the top of the solidification material slurry injection part of the injection rod is used to push up the disturbed soil near the solidification material slurry injection port upward, forming a void below the soil push-up disk, and the mixed soil mixed with the solidification material slurry is absorbed into the void, thereby creating a cylindrical improved body in the ground to be improved. In this method, drilling to the planned improvement depth is performed in multiple steps using an agitation device equipped with a soil push-up disk adjacent to the top of the agitator blade installed at the top of the drilling blade at the tip of the injection rod, and a single drilling and extraction-compatible soil removal is performed during the drilling. This is a ground improvement method in which a step length in the depth direction corresponding to the amount of water injected into the ground is appropriately set according to the soil quality, drilling is performed to the set first step depth while injecting drilling water at low pressure, and then the length corresponding to that one step depth is withdrawn and removed. Then drilling is performed to the bottom end of the next second step depth while injecting drilling water at low pressure, and then the length corresponding to that one step depth is withdrawn and removed. This is repeated for each step to drill and remove soil to the planned improvement depth, next the rod is withdrawn to the ground, and drilling is performed again to the planned improvement depth. After that, a slurry-like solidification material is withdrawn while being injected at high pressure to the side from the nozzle of the mixing blade installed near the tip of the rod that has reached the planned improvement depth, and a cylindrical improved body is created. The water content of the soil of the ground, taking into account the amount of water injected into the ground during drilling, is calculated based on the water content of the soil in the ground. The relationship between the soil removal rate and The soil discharge rate is Over 80% The range of water content The drilling water is injected in such a volume that the water amount is within the range of the This is a ground improvement method characterized by the above. The present invention also relates to a ground improvement method in which a drilling blade at the tip of a single-tube injection rod is used to drill holes in the ground to a planned depth, and the outside of the agitator blade is cut and mixed with the energy of the solidification material slurry injected into the ground through the injection rod at high pressure while a soil push-up disk provided adjacent to the upper part of the solidification material slurry injection part of the injection rod is used to push up the disturbed soil near the solidification material slurry injection port upward to form a void below the soil push-up disk, and the mixed soil mixed with the solidification material slurry is absorbed into the void to create a cylindrical improved body in the ground to be improved. In this method, drilling to the planned improvement depth is performed in a plurality of steps using an agitation device equipped with a soil push-up disk adjacent to the upper part of the agitation blade provided at the upper part of the drilling blade at the tip of the injection rod, and a step length in the depth direction equivalent to the amount of soil that can be drilled and extracted in one drilling is appropriately set according to the soil type, and the first set This is a ground improvement method in which drilling is performed while jetting drilling water at low pressure up to a step depth, then the soil is withdrawn and discharged for a length equivalent to that step depth, drilling is performed again while jetting drilling water at low pressure up to the bottom end of the next second step depth, then the soil is withdrawn and discharged for a length equivalent to that step depth, and this process is repeated for each step to drill and discharge soil up to the planned improvement depth, then the rod is temporarily withdrawn to the ground and drilled again to the planned improvement depth, after which a slurry-like solidification material is jetted at high pressure sideways from the nozzle of the agitating blade installed near the tip of the rod that has reached the planned improvement depth, and is withdrawn, thereby creating a cylindrical improved body, and the drilling water is injected with an amount of water such that the soil discharge rate obtained from the relationship between the soil moisture content of the soil of the ground, taking into account the amount of drilling water used during drilling, is within a range of moisture content such that the soil discharge rate is 90% or more. The present invention also relates to a ground improvement method in which a drilling blade at the tip of a single-tube injection rod is used to drill holes in the ground to a planned depth, and the outside of the agitator blade is cut and mixed with the energy of the solidification material slurry injected into the ground through the injection rod at high pressure, while the disturbed soil near the solidification material slurry injection port is pushed upward by a soil pushing-up disk provided adjacent to the upper part of the solidification material slurry injection part of the injection rod, forming a void below the soil pushing-up disk, and the mixed soil mixed with the solidification material slurry is absorbed into the void, thereby creating a cylindrical improved body in the ground to be improved. In this method, drilling to the planned improvement depth is performed in a plurality of steps using an agitation device equipped with a soil pushing-up disk adjacent to the upper part of the agitation blade provided at the upper part of the drilling blade at the tip of the injection rod, and the step length in the depth direction corresponding to the amount of soil that can be drilled and extracted in one drilling is appropriately set according to the soil type, and the soil is removed up to the set first step depth. This is a ground improvement method in which drilling is performed by injecting drilling water at low pressure, then withdrawing and discharging soil by the length equivalent to the depth of one step, then drilling again to the bottom end of the next second step depth while injecting drilling water at low pressure, then withdrawing and discharging soil by the length equivalent to the depth of that step, and repeating this process for each step to drill and discharge soil to the planned improvement depth, then withdrawing the rod to the ground once, and then re-drilling to the planned improvement depth, and then withdrawing slurry-like solidification material from the nozzle of the mixing blade installed near the tip of the rod that has reached the planned improvement depth while injecting it at high pressure to the side, thereby creating a cylindrical improved body. The range of moisture content at which the soil discharge rate is appropriate is standardized based on the moisture content of the soil of the ground, taking into account the amount of drilling water during drilling, and the amount of drilling water can be set. The moisture content of the ground, taking into account the amount of drilling water, is normalized by the liquid limit of the soil of the ground, and the normalized moisture content (W / W L This is a ground improvement method characterized in that the drilling water is injected in an amount such that the ratio of the water content to the total water content is 0.7 to 1.3. The present invention also relates to a ground improvement method in which a drilling blade at the tip of a single-tube injection rod is used to drill holes in the ground to a planned depth, and the outside of the agitator blade is cut and mixed with the energy of the solidification material slurry injected into the ground through the injection rod at high pressure, while the disturbed soil near the solidification material slurry injection port is pushed upward by a soil pushing-up disk provided adjacent to the upper part of the solidification material slurry injection part of the injection rod, forming a void below the soil pushing-up disk, and the mixed soil mixed with the solidification material slurry is absorbed into the void, thereby creating a cylindrical improved body in the ground to be improved. In this method, drilling to the planned improvement depth is performed in a plurality of steps using an agitation device equipped with a soil pushing-up disk adjacent to the upper part of the agitation blade provided at the upper part of the drilling blade at the tip of the injection rod, and the step length in the depth direction corresponding to the amount of soil that can be drilled and extracted in one drilling is appropriately set according to the soil type, and the soil is removed up to the set first step depth. This is a ground improvement method in which drilling is performed by injecting drilling water at low pressure, then withdrawing and discharging soil by the length equivalent to the depth of one step, then drilling again to the bottom end of the next second step depth while injecting drilling water at low pressure, then withdrawing and discharging soil by the length equivalent to the depth of that step, and repeating this process for each step to drill and discharge soil to the planned improvement depth, then withdrawing the rod to the ground once, and then re-drilling to the planned improvement depth, and then withdrawing slurry-like solidification material from the nozzle of the mixing blade installed near the tip of the rod that has reached the planned improvement depth while injecting it at high pressure to the side, thereby creating a cylindrical improved body. The range of moisture content at which the soil discharge rate is appropriate is standardized based on the moisture content of the soil of the ground, taking into account the amount of drilling water during drilling, and the amount of drilling water can be set. The moisture content of the ground, taking into account the amount of drilling water, is normalized by the liquid limit of the soil of the ground, and the normalized moisture content (W / W L This is a ground improvement method characterized in that the drilling water is injected in an amount such that the ratio of the water content to the total water content is 0.8 to 1.2.

[0008] still , Books The invention is capable of normalizing the water content of the ground, taking into account the amount of drilling water, by the liquid limit of the soil of the ground. 。 Effect of the Invention

[0009] The present invention standardizes the range of moisture content at which the soil discharge rate is appropriate based on the moisture content of the soil of the ground taking into account the amount of drilling water used during drilling, and makes it possible to set the amount of drilling water, thereby making it possible to provide a ground improvement method that can maintain the effect of reducing ground displacement even when the ground to be improved is composed mainly of high-cohesive clay soil. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an embodiment of the present invention, and is a schematic diagram showing a graph used when standardizing the range of water content in which the soil discharge rate is appropriate. [Diagram 2] FIG. 1 is a diagram showing an embodiment of the present invention, and is a schematic diagram showing the trajectory of the drilling depth position of the tip of the rod in a ground drilling method using an improved device. [Diagram 3] FIG. 1 is a diagram showing an embodiment of the present invention, and is a cross-sectional view showing an apparatus used in the construction method of the embodiment and a soil discharge situation. [Figure 4] FIG. 4 is a view taken along the line IV-IV in FIG. [Diagram 5] FIG. 1 is a diagram showing an embodiment of the present invention, and is a cross-sectional view showing an apparatus used in the method of the embodiment and an improved state. [Figure 6] 6 is a cross-sectional view taken along line VI-VI of FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In order to achieve the above object, the inventor of the present invention has intensively analyzed the construction data of each site of ground improvement works accumulated over many years, and has found that it is possible to standardize the range of the water content of the soil of the ground, taking into account the amount of water during drilling when the soil discharge rate is appropriate. The present invention is based on this finding.

[0012] An embodiment of the present invention will be described with reference to Fig. 1 to Fig. 6. First, a ground improvement device used in the ground improvement method of this embodiment will be described. The ground improvement device 1 (hereinafter abbreviated as device 1) comprises a rotating and vertical movement mechanism 2 and a single-tube injection rod 3 (hereinafter referred to as injection rod 3). The rotating and vertical movement mechanism 2 supports the injection rod 3 by a support 4 so that it can rotate and move up and down.

[0013] The upper end of the injection rod 3 is connected to a solidification material slurry pressure-transport hose 6 via a swivel 5. The lower end of the injection rod 3 is provided with an excavation fang (also called an earth auger) 7, which is a type of excavation blade constituting the agitation device, and an agitation blade 8, and the shaft and agitation blade 8 are provided with an injection nozzle 9 for the solidification material slurry S, which is a type of solidification material slurry injection part. The solidification material slurry S is, for example, a mixture of a solidification material and water.

[0014] A soil pushing-up disk 10 is provided near the top of the impeller 8 and close to the top of the injection nozzle 9 for pushing up the soil disturbed by the impeller 8 when the injection rod 3 is raised in a stepwise manner. The soil pushing-up disk 10 is provided to push up the disturbed soil near the injection port (not shown) of the injection nozzle 9, form a void below the soil pushing-up disk 10, absorb the mixed soil mixed with the solidification material slurry S into the void, and create a cylindrical improved body in the soft ground G (hereinafter abbreviated as ground G), which is the ground to be improved.

[0015] In order to maximize the efficiency of soil removal when the injection rod 3 that has penetrated into the ground is pulled up, the soil push-up disk 10 has a radius equal to or smaller than the radius of the impeller 8 by 10 cm or less, preferably 5 cm, and is tilted at an angle of 10 to 20°, preferably 15°, in a projected plan view.

[0016] The injection rod 3 rotates and penetrates into the ground G while injecting drilling water at low pressure, so that a disturbed part G1 is formed by the stirring blades 8. In this disturbed part G1, a roughly cylindrical muddy water film G2 is formed by the disturbed soil and drilling water.

[0017] Next, the ground improvement method of this embodiment will be described. (0) First, when carrying out the ground improvement method, the range of moisture content that provides an appropriate soil discharge rate is standardized. Figure 1 shows a graph for standardizing the range of moisture content that provides an appropriate soil discharge rate. The graph shows the relationship between the soil discharge rate and the moisture content that takes into account the amount of water used for drilling the soil. In this embodiment, in order to minimize the influence of the soil quality at each site, the actual moisture content W is set as the moisture content W, which is the liquid limit W. L Normalized water content (W / W L ) is used.

[0018] The soil discharge rate is calculated using the following formula:

[0019]

number

[0020] At least when the soil of ground G is clayey such as highly cohesive clay, it has been found empirically that the relationship between the soil moisture content taking into account the amount of drilling water and the soil discharge rate can be approximated to the estimated line shown in the graph, although there may be some deviation depending on the soil quality of each site. Therefore, it is possible to standardize the range of moisture content for which the soil discharge rate is appropriate from the soil moisture content of ground G taking into account the amount of drilling water during drilling.

[0021] For example, if the soil discharge rate is 80% or more, that is, the normalized water content (W / W L ) = 0.7 to 1.3, preferably, the soil removal rate is 90% or more, that is, the normalized water content (W / W L It is possible to standardize the range of water content in which the water content is 0.8 to 1.2.

[0022] (1) Next, a soil survey of ground G is carried out. In this soil survey, at least the natural water content (Wn : unit %, liquid limit (W L : Unit %. Liquid limit W L is evaluated, for example, by the Casagrande method.

[0023] And the standardized water content (W / W L ) and the liquid limit W of the soil L The soil moisture content W is calculated by adding the amount of drilling water that will result in an appropriate soil removal rate, and the soil moisture content W is compared with the natural moisture content W of the soil. n Using the standardized water content W / W L The amount of water to be added during drilling, i.e., the amount of drilling water and the drilling speed, is determined so that:

[0024] (2) After that, the actual construction is carried out. In the actual construction, first, for example, as shown in FIG. 2, the ground G is excavated to the planned depth by the excavation fangs 7 in a multiple step method. Specifically, the step length in the depth direction corresponding to the amount of soil that can be excavated and extracted in one step is appropriately set according to the soil quality of the ground G, and the ground G is excavated to the first step depth by the device 1 according to the standardized water content (W / W L ), drilling is performed at the same drilling speed while injecting drilling water at low pressure with the amount of water determined in step (1) so that the depth becomes equal to the depth of one step, and then the soil is pulled out and removed by a length equivalent to the depth of one step (hereinafter, the removed soil is referred to as removal soil G3).

[0025] Next, drilling is performed again to the bottom of the second step depth while injecting the drilling water at low pressure with the amount of water determined in step (1) at the same drilling speed, and then the soil is pulled out and removed for the length equivalent to that one step depth (second step depth). This is repeated for each step to drill the hole to the planned improvement depth.

[0026] In this embodiment, when the injection rod 3 penetrates the ground G while rotating, the stirring blades 8 are pressed against the injection rod 3 to form a disturbed portion G1 in the ground G. At this time, a gap is formed on the outer circumferential surface of the disturbed portion G1, and drilling water enters the gap, mixing the disturbed soil and the drilling water. In particular, the disturbed soil in the gap is turned into a muddy state, forming a thin, approximately cylindrical muddy water film G2. As a result, the disturbed soil located within the diameter of the soil pushing-up disk 10 is separated from the area outside the diameter, and the disturbed soil within the diameter is pushed up and removed by the rotation of the soil pushing-up disk 10.

[0027] Next, the injection rod 3 is once pulled out to the ground, and the hole is again drilled to the planned improvement depth, and the solidification material slurry S is pulled out while being sprayed sideways at high pressure from the injection nozzle 9 of the injection rod 3, forming an improved portion G4. At this time, the energy of the solidification material slurry S sprayed at high pressure into the ground G through the injection rod 3 cuts and mixes the outside of the agitator 8, while the soil pushing-up disk 10 pushes up the disturbed soil near the solidification material slurry spray nozzle, forming a void below the soil pushing-up disk 10, and the mixed soil mixed with the solidification material slurry S is absorbed into the void, creating an improved column in the ground G, completing the improvement of the ground G.

[0028] Therefore, in the ground improvement method of this embodiment, the range of the moisture content W of the ground G taking into account the amount of drilling water during drilling is standardized to provide an appropriate soil discharge rate, and the amount of drilling water can be set. This makes it possible to drill the ground G with an appropriate amount of drilling water and drilling speed, and provides a ground improvement method that can maintain the effect of reducing ground displacement even when the ground G is composed of particularly high-cohesive clay soil.

[0029] Although the present invention has been described above based on the above embodiment, the present invention is not limited to the above embodiment and can be modified as appropriate within the scope of the invention. For example, in the above embodiment, the water content is standardized from the graph and the water content is used as the standard as it is, but since there is a possibility that some deviation occurs depending on the soil quality of each site, a test construction may be performed before the actual construction, and the standardized water content may be corrected. [Explanation of symbols]

[0030] 1 Ground improvement device 2 Rotating and vertical mechanism 3 Single pipe injection rod 4 Support 5 Swivel 6 Solidification material slurry pressure delivery hose 7 Drilling fang 8 Mixing blade 9 Injection nozzle 10 Soil push-up disk G Ground G1 Disturbance section G2 Mud film G3 Earth removal G4 Improvement section S Solidification material slurry

Claims

1. A ground improvement method in which a drilling blade at the tip of a single-tube injection rod is used to drill a hole in the ground to a planned depth, and the outside of the agitator blade is cut and mixed with the energy of the solidification material slurry that is injected into the ground at high pressure through the injection rod, while a soil pushing-up disk installed close to the top of the solidification material slurry injection part of the injection rod pushes up the disturbed soil near the solidification material slurry injection port, forming a void below the soil pushing-up disk, and the mixed soil mixed with the solidification material slurry is absorbed into the void, thereby creating a cylindrical improved body in the ground to be improved. a soil improvement method in which a soil drilling device equipped with a soil pushing-up disk adjacent to the top of an agitator blade attached to the top of an excavation blade at the tip of an injection rod is used to drill holes to a depth to be improved in a plurality of steps, a step length in the depth direction corresponding to the amount of soil that can be drilled and removed in one drilling is appropriately set according to the soil quality, drilling is performed while injecting drilling water at low pressure to the set first step depth, and then the soil is withdrawn and removed by the length corresponding to that one step depth, drilling is performed again while injecting drilling water at low pressure to the bottom end of the next second step depth, and then the soil is withdrawn and removed by the length corresponding to that one step depth, and this is repeated for each step to drill and remove the soil to the planned improvement depth, next the rod is temporarily withdrawn to the ground, and drilling is performed again to the planned improvement depth, and then a slurry solidification material is withdrawn while being injected at high pressure to the side from the nozzle of the agitator blade attached near the tip of the rod that has reached the planned improvement depth, thereby creating a cylindrical improved body; A ground improvement method characterized by injecting drilling water at a volume such that the soil discharge rate is within the range of moisture content where the soil discharge rate is 80% or more, as determined from the relationship between the soil moisture content of the ground and the soil discharge rate, taking into account the volume of drilling water used during drilling.

2. A ground improvement method in which a drilling blade at the end of a single-tube injection rod is used to drill a hole in the ground to a planned depth, and the outside of the agitator blade is cut and mixed with the energy of the solidification material slurry which is injected at high pressure through the injection rod into the ground, while a soil pushing-up disk installed close to the top of the solidification material slurry injection part of the injection rod pushes up the disturbed soil near the solidification material slurry injection port, forming a void below the soil pushing-up disk, and the mixed soil mixed with the solidification material slurry is absorbed into the void, thereby creating a cylindrical improvement body in the ground to be improved; a soil improvement method in which a soil drilling device equipped with a soil pushing-up disk adjacent to the top of an agitator blade attached to the top of an excavation blade at the tip of an injection rod is used to drill holes to a depth to be improved in a plurality of steps, a step length in the depth direction corresponding to the amount of soil that can be drilled and removed in one drilling is appropriately set according to the soil quality, drilling is performed while injecting drilling water at low pressure to the set first step depth, and then the soil is withdrawn and removed by the length corresponding to that one step depth, drilling is performed again while injecting drilling water at low pressure to the bottom end of the next second step depth, and then the soil is withdrawn and removed by the length corresponding to that one step depth, and this is repeated for each step to drill and remove the soil to the planned improvement depth, next the rod is temporarily withdrawn to the ground, and drilling is performed again to the planned improvement depth, and then a slurry solidification material is withdrawn while being injected at high pressure to the side from the nozzle of the agitator blade attached near the tip of the rod that has reached the planned improvement depth, thereby creating a cylindrical improved body; A ground improvement method characterized by injecting drilling water at a volume such that the soil discharge rate is within the range of moisture content such that the soil discharge rate is 90% or more, as determined from the relationship between the moisture content of the soil of the ground, taking into account the volume of drilling water used during drilling, and the soil discharge rate.

3. 3. The ground improvement method according to claim 1, wherein the water content of the ground taking into account the amount of drilling water is normalized by the liquid limit of the soil of the ground.

4. A ground improvement method in which a drilling blade at the end of a single-tube injection rod is used to drill a hole in the ground to a planned depth, and the outside of the agitator blade is cut and mixed with the energy of the solidification material slurry which is injected into the ground through the injection rod at high pressure, while a soil pushing-up disk installed close to the top of the solidification material slurry injection part of the injection rod pushes up the disturbed soil near the solidification material slurry injection port, forming a void below the soil pushing-up disk, and the mixed soil mixed with the solidification material slurry is absorbed into the void, thereby creating a cylindrical improvement body in the ground to be improved; a soil improvement method in which a soil drilling device equipped with a soil pushing-up disk adjacent to the top of an agitator blade attached to the top of an excavation blade at the tip of an injection rod is used to drill holes to a depth to be improved in a plurality of steps, a step length in the depth direction corresponding to the amount of soil that can be drilled and removed in one drilling is appropriately set according to the soil quality, drilling is performed while injecting drilling water at low pressure to the set first step depth, and then the soil is withdrawn and removed by the length corresponding to that one step depth, drilling is performed again while injecting drilling water at low pressure to the bottom end of the next second step depth, and then the soil is withdrawn and removed by the length corresponding to that one step depth, and this is repeated for each step to drill and remove the soil to the planned improvement depth, next the rod is temporarily withdrawn to the ground, and drilling is performed again to the planned improvement depth, and then a slurry solidification material is withdrawn while being injected at high pressure to the side from the nozzle of the agitator blade attached near the tip of the rod that has reached the planned improvement depth, thereby creating a cylindrical improved body; The range of moisture content at which the soil discharge rate is appropriate is standardized based on the moisture content of the soil of the ground, taking into account the amount of drilling water used during drilling, and the amount of drilling water can be set. The water content of the ground, taking into account the amount of drilling water, is normalized by the liquid limit of the soil of the ground, Normalized water content ratio (W / W Ｌ The method for improving ground is characterized in that the drilling water is injected in an amount such that the ratio of the water content to the total water content is 0.7 to 1.

3.

5. A ground improvement method in which a drilling blade at the end of a single-tube injection rod is used to drill a hole in the ground to a planned depth, and the outside of the agitator blade is cut and mixed with the energy of the solidification material slurry which is injected into the ground through the injection rod at high pressure, while a soil pushing-up disk installed close to the top of the solidification material slurry injection part of the injection rod pushes up the disturbed soil near the solidification material slurry injection port, forming a void below the soil pushing-up disk, and the mixed soil mixed with the solidification material slurry is absorbed into the void, thereby creating a cylindrical improvement body in the ground to be improved; a soil improvement method in which a soil drilling device equipped with a soil pushing-up disk adjacent to the top of an agitator blade attached to the top of an excavation blade at the tip of an injection rod is used to drill holes to a depth to be improved in a plurality of steps, a step length in the depth direction corresponding to the amount of soil that can be drilled and removed in one drilling is appropriately set according to the soil quality, drilling is performed while injecting drilling water at low pressure to the set first step depth, and then the soil is withdrawn and removed by the length corresponding to that one step depth, drilling is performed again while injecting drilling water at low pressure to the bottom end of the next second step depth, and then the soil is withdrawn and removed by the length corresponding to that one step depth, and this is repeated for each step to drill and remove the soil to the planned improvement depth, next the rod is temporarily withdrawn to the ground, and drilling is performed again to the planned improvement depth, and then a slurry solidification material is withdrawn while being injected at high pressure to the side from the nozzle of the agitator blade attached near the tip of the rod that has reached the planned improvement depth, thereby creating a cylindrical improved body; The range of moisture content at which the soil discharge rate is appropriate is standardized based on the moisture content of the soil of the ground, taking into account the amount of drilling water used during drilling, and the amount of drilling water can be set. The water content of the ground, taking into account the amount of drilling water, is normalized by the liquid limit of the soil of the ground, Normalized water content ratio (W / W Ｌ The method for improving ground is characterized in that the amount of drilling water is injected so that the ratio of the water content to the total water content is 0.8 to 1.2.

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