Ground compaction method

Abstract

To provide a ground compaction method which reduces a load on a pump that pumps a fluid solidification material, is not restricted by restriction of a limit injection pressure in terms of an improvement diameter that can be created depending on a soil quality, a stress state or the like of a target ground, is free of the risk of ground uplift in low soil covering areas, and has a wide range of fluid solidification materials that can be used.SOLUTION: A ground compaction method includes the steps of: forming a cylindrical loosened space in a ground G by rotating a diameter expansion jig 2 provided at a lower end of a boring rod 1 via the boring rod 1; discharging a fluid solidification material pumped via the boring rod 1 from a lower end opening of the boring rod 1 into the cylindrical loosened space formed in the ground G to pressurize and fill the space; and pulling up the boring rod 1 and performing steps (2) and (3) to form a cylindrical ground improvement area R within a specified depth range of the ground G.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a ground compaction method in which a fluid solidification material is injected into and filled into the ground to compact the surrounding ground. [Background technology]

[0002] 2. Description of the Related Art Conventionally, for the purpose of improving the ground, many ground improvement methods have been proposed and put to practical use, in which a fluid solidification material such as cement slurry is injected into the ground and filled in the ground (see, for example, Patent Documents 1 and 2).

[0003] In the conventional ground improvement method, a fluidized solidification material such as cement slurry is injected into the ground through a nozzle provided on a boring rod or a diameter expanding jig attached to the boring rod. This inevitably places a heavy load on the pump that pumps the cement slurry and other fluid solidification materials. In addition, the improvement diameter that can be created may be restricted by the maximum injection pressure depending on the soil quality and stress state of the target ground. There is also a risk of ground upheaval in areas with low soil cover. Furthermore, there are problems in that the fluid solidification materials that can be used are limited to cement slurry and the like, which are less likely to cause blockages.

[0004] Furthermore, in conventional ground improvement methods, cement slurry, which is commonly used as a fluid solidification material, has the problem of emitting a large amount of CO2 during production, which places a heavy burden on the environment. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-137722 A [Patent Document 2] Japanese Patent Application Publication No. 62-148715 Summary of the Invention [Problem to be solved by the invention]

[0006] In consideration of the problems associated with conventional ground improvement methods, the first object of the present invention is to provide a ground compaction method which imposes a small load on the pump that pressurizes the fluid solidification material, which is not restricted by the maximum injection pressure in terms of the improvement diameter that can be achieved depending on the soil quality and stress state of the target ground, which is free of the risk of ground upheaval in low soil covering areas, and which has a wide range of fluid solidification materials to choose from.

[0007] A second object of the present invention is to provide a ground compaction method capable of suppressing CO2 emissions. [Means for solving the problem]

[0008] In order to achieve the first object, the present invention provides a ground compaction method for compacting the surrounding ground by injecting and filling a fluidized solidification material into the ground, (1) The process of drilling a hole to a specified depth using a boring rod made of a tubular member. (2) A process of forming a cylindrical loose space in the ground by rotating an expansion jig attached to the lower end of the boring rod through the boring rod. (3) The process of pumping and discharging fluid solidification material through a boring rod from the lower opening of the boring rod into a cylindrical loosened space formed in the ground, thereby filling it. (4) A process of forming a cylindrical ground improvement section within a specified depth range of the ground by pulling up the boring rod and performing steps (2) and (3). (5) The process of raising the boring rod to the surface. The present invention is characterized by comprising:

[0009] In this case, in step (4), the boring rod is pulled up and steps (2) and (3) are repeated a predetermined number of times to form a cylindrical ground improvement section within a predetermined depth range of the ground.

[0010] In addition, in the step (4), by simultaneously performing the steps (2) and (3) and pulling up the boring rod, a cylindrical ground improvement section can be formed within a specified depth range of the ground.

[0011] Furthermore, in the step (3), the fluid solidification material can be injected and filled in an amount in the range of -10% to +1000% of the volume of the cylindrical loosened space formed in the ground in the step (2).

[0012] In addition, the diameter expanding wing of the diameter expanding jig can be fixedly installed on the lower end of the boring rod.

[0013] In addition, the diameter expanding wing of the diameter expanding jig can be movably installed at the lower end of the boring rod between a protruding state and a retracted state.

[0014] In addition, the inside diameter of the lower end opening of the boring rod from which the fluid solidification material is discharged can be set to be equal to or larger than the inside diameter of the boring rod.

[0015] In order to achieve the second object, the present invention provides a method for consolidating ground, comprising the steps of: 3 It is characterized by its low CO2 emissions per unit of -350 to 100 kg. Effect of the Invention

[0016] According to the ground compaction method of the present invention, the load on the pump that pressurizes the fluid solidification material is small, the improvement diameter that can be created is not restricted by the limit of the maximum injection pressure depending on the soil quality and stress state of the target ground, there is no risk of ground upheaval in low soil covering areas, and a ground compaction method can be provided that has a wide selection of fluid solidification materials that can be used.

[0017] In addition, according to the ground compaction method of the present invention, the fluidized solidification material is 3The CO2 emissions per unit are -350~100 kg, which means that CO2 emissions can be reduced compared to fluid solidification materials that use cement, thereby contributing to reducing the environmental burden. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a process explanatory diagram showing one embodiment of the ground compaction method of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] This is a photograph showing the completed state (ground improvement area) of the demonstration test (sandy soil). [Diagram 5] This is a photograph showing the completed state (ground improvement area) of the demonstration test (clay soil). [Figure 6] FIG. 1 is an explanatory diagram of a diameter expansion jig used in a demonstration test. [Figure 7] FIG. 2 is an explanatory diagram showing the installation positions of earth pressure gauges in a demonstration test. [Figure 8] FIG. 2 is an explanatory diagram showing the installation positions of earth pressure gauges in a demonstration test. [Figure 9] 1 is a graph showing earth pressure measurement results in a demonstration test. [Figure 10] 1 is a graph showing earth pressure measurement results in a demonstration test. [Figure 11] This is a photograph showing the completed state of the demonstration test (ground improvement section). [Figure 12] This is a photograph showing the completed state of the demonstration test (ground improvement section). [Figure 13] This is a photograph showing the completed state of the demonstration test (ground improvement section). [Figure 14] This is a photograph showing the completed state of the demonstration test (ground improvement section). [Figure 15] FIG. 1 is an explanatory diagram showing the locations where cores were taken from the completed form of the demonstration test. [Figure 16] FIG. 1 is an explanatory diagram showing the locations where cores were taken from the completed form of the demonstration test. [Figure 17]The results of the core analysis are shown in Fig. 1. (a) is a graph showing the moisture content-dry density distribution, and (b) is a graph showing the dry density-uniaxial compressive strength distribution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the ground compaction method of the present invention will be described with reference to the drawings.

[0020] The ground compaction method of the present invention is a method for compacting the surrounding ground by injecting and filling a fluidized solidification material into the ground G as shown in FIG. (1) The process of drilling a hole to a specified depth using a boring rod 1 made of a tubular material (Figure 1 (1)). (2) A process of forming a cylindrical loose space in the ground G by rotating the expanding jig 2 attached to the lower end of the boring rod 1 through the boring rod 1 (Figure 1 (2)). (3) The process of pumping and discharging the fluid solidification material via the boring rod 1 from the lower end opening of the boring rod 1 into the cylindrical loosened space formed in the ground G and filling it (Figure 1 (3)). (4) A process of forming a cylindrical ground improvement section R within a specified depth range of the ground G by pulling up the boring rod 1 and performing steps (2) and (3) (Figure 1 (4)). (5) The process of pulling the boring rod 1 up to the ground surface (Figure 1 (5)). It includes.

[0021] In this case, in the example shown in Figure 1, in step (4), the boring rod 1 is pulled up and steps (2) and (3) are repeated a predetermined number of times to form a cylindrical ground improvement section R within a predetermined depth range of the ground G. The amount by which the boring rod 1 is pulled up in one go can be made to be approximately the same as the height of the cylindrical loosened space in the ground G formed by the expansion jig 2 by rotating the boring rod 1 (example shown in Figure 1), or it can be made smaller so that the cylindrical loosened space formed first and the cylindrical loosened space formed next overlap, or it can be made larger so that the cylindrical loosened space formed first and the cylindrical loosened space formed next are formed with a gap between them, thereby making it possible to adjust the degree of loosening of the ground G and the uniformity of the cylindrical ground improvement section R.

[0022] Here, in order to reduce the load when drilling holes using the boring rod 1 in step (1) and to prevent soil and sand from flowing in through the lower end opening of the boring rod 1, water pumped through the boring rod 1 is discharged from the lower end opening of the boring rod 1 while drilling the holes. In addition, in order to prevent soil and sand from flowing in through the lower end opening of the boring rod 1, if necessary, a check valve such as a non-return valve (not shown) can be provided in the vicinity of the lower end opening of the boring rod 1, specifically, in the vicinity of the lower end opening of the expansion jig 2 provided at the lower end of the boring rod 1.

[0023] Furthermore, the amount of fluid solidification material pressed and filled in step (3) above can be set appropriately depending on the properties of the surrounding ground, the required ground compaction strength, the properties of the fluid solidification material to be pressed and filled, etc., but it is preferable that the amount be in the range of -10% to +1000%, preferably -10% to +500%, and more preferably -10% to +300%, of the volume of the cylindrical loosened space formed in the ground in step (2) above, specifically, the volume of the cylindrical space directly loosened by the main body part and expansion blades of the expansion jig 2.

[0024] In addition, in step (4), the boring rod 1 is pulled up while steps (2) and (3) are performed simultaneously. Specifically, by performing steps (2) and (3) while pulling up the boring rod 1 at a constant speed, a cylindrical ground improvement section R can be formed within a predetermined depth range of the ground G. This makes it possible to form a uniform cylindrical ground improvement section R within a specified depth range of the ground G.

[0025] The expansion wing of the expansion jig 2 can be fixedly installed at the lower end of the boring rod 1, but it is preferable that it be movable between an extended state and a retracted state so that the boring rod 1 can smoothly drill a hole in step (1) and pull the boring rod 1 up to the ground surface in step (5).

[0026] The mechanism for moving the expansion wing 22 of the expansion jig 2 between the protruding state and the stored state can be performed by an appropriate driving mechanism, but in this case, it is necessary to secure space in the boring rod 1 to install the driving mechanism, which results in the problem that the boring rod 1 becomes larger and the structure of the boring rod 1 becomes complex.

[0027] To address this problem, a mechanism is adopted in which the expansion wing 22 is switched between an extended state and a retracted state by the reaction force applied from the surrounding ground G depending on the direction of rotation of the boring rod 1, without using a drive mechanism. This makes it possible to solve the problem that the boring rod 1 becomes large and the structure of the boring rod 1 becomes complicated.

[0028] A specific example of an expansion jig 2 that employs this mechanism is the patent application of the present applicant (Patent Application No. 2023-17130). As shown in Figures 2 and 3, this expansion jig 2 is integrally attached to the tip of the boring rod 1, and the expansion wing 22 can be displaced between an extended state and a stored state via an axis 23, and in the stored state, the claw portion 22a provided at the tip of the expansion wing 22 protrudes from the outer periphery of the expansion jig 2. When drilling a hole with the boring rod 1 in step (1) and pulling the boring rod 1 up to the ground surface in step (5), the boring rod 1 is rotated counterclockwise so that the expansion blade 22 is in a stored state, thereby reducing the load when drilling a hole with the boring rod 1 and pulling it up. On the other hand, when forming a cylindrical loose space in the ground G in steps (2) and (4), the boring rod 1 is rotated clockwise so that the expansion blade 22 is in a protruding state, and the ground G is stirred by the expansion blade 22 to form a cylindrical loose space in the ground G. When pulling up the boring rod 1 in step (4), the boring rod 1 may be rotated counterclockwise so that the expansion wing 22 is in the stored state, or the boring rod 1 may be rotated clockwise so that the expansion wing 22 is left in the protruding state.

[0029] When an expansion jig 2 is attached to the tip of the boring rod 1, as in this example, the lower end opening of the boring rod 1 from which the fluid solidification material is ejected, the inner diameter of the lower end opening 21a of the flow path 21 of the expansion jig 2 is made to be equal to or larger than the inner diameter of the flow path 11 of the boring rod 1 (in this example, the same diameter). This reduces the load on the pump that pumps the fluidized solidification material, makes it difficult for the flow paths 11 and 21 to be blocked, and widens the range of fluidized solidification materials that can be used.

[0030] Here, the inner diameter of the flow passage 11 of the boring rod 1 (the inner diameter of the lower end opening 21a of the flow passage 21 of the diameter expansion jig 2) can be arbitrarily determined depending on the properties of the ground G and the shape of the ground improvement portion R to be formed in the ground G. It can be set to anywhere between 100 and 300 mm. The outer diameters of the diameter expansion jig 2 and the diameter expansion blade 22 in the protruding state can be set to about 150 to 400 mm and about 300 to 800 mm, respectively.

[0031] The fluidized solidification material used in the ground compaction method can be a fluidized solidification material using cement such as cement slurry, but it is necessary to use a thickness of 1 m 3 This fluidized solidification material is suitable for use as it reduces CO2 emissions per unit of time, at -350 to 100 kg, and therefore contributes to reducing the environmental load, compared to fluidized solidification materials that use cement.

[0032] First, the material of the fluidized solidification material used in the ground compaction method will be described. Table 1 shows the materials of the fluid solidification material (hereinafter in this specification, the materials may be referred to by the symbols in Table 1).

[0033] [Table 1]

[0034] [aggregate] The aggregate that serves as the base material for the fluid solidification material can be made from unused resources such as crushed stone powder and crushed stone screenings, as well as by-products such as crushed concrete sludge aggregate and fine blast furnace slag aggregate. As it does not use natural resources, it contributes to sustainability.

[0035] [Slag powder] The ground granulated blast furnace slag used was a gypsum-added product (premixed with anhydrite and gypsum). Ground granulated blast furnace slag has a specific surface area of ​​3500 to 5000 cm 2 / g is economical and easy to procure, but is not limited thereto, and a specific surface area of ​​5000 to 12000 cm 2 / g has the same or better reactivity with sodium silicate, so the use of this material can provide the same or better performance.

[0036] [Inactive filler] As a filler, precipitated calcium carbonate is mixed in to replace part of the aggregate or solidifying agent. Precipitated calcium carbonate is a material used for carbon dioxide capture and utilization (CCU). It is a material that fixes CO2 derived from exhaust gas into a calcium source derived from a by-product. The CCU material is used as a ground injection material to achieve carbon dioxide capture, utilization and storage (CCUS). Since CO2 is mineralized in the form of calcium carbonate and then stored underground as part of ground improvement work, it is expected to be easier and cheaper to store than carbon dioxide capture and storage (CCS), which injects CO2 into a reservoir deep underground. Another advantage is that there is no risk of the injected CO2 leaking out of the reservoir due to external forces such as earthquakes. In addition to calcium wastewater, the calcium source for light calcium carbonate can also be, for example, a by-product from acetylene gas production, a by-product from steelmaking, ready-mixed concrete sludge, waste concrete, returned concrete, incineration ash, coal ash, waste gypsum, waste seawater discharged from a magnesium hydroxide production process, or the like. The purity of the precipitated calcium carbonate used in the property test is 98%, and 431 kg-CO2 / t of CO2 is fixed. If the CO2 emissions during production (50 kg-CO2 / t) are subtracted from this value, the net CO2 emission intensity is -431+50=-381 kg-CO2 / t.

[0037] [Sodium silicate (alkaline stimulant)] The reaction between sodium silicate (Na2O·nSiO2), which is added as an alkaline stimulant, and the gypsum contained in the ground granulated blast furnace slag is as follows. Na2O·nSiO2+CaSO4→ CaO·nSiO2+2Na2SO4 Here, the amount of gelled matter produced is affected by the amount of gypsum and the Na2O concentration, while the strength of the gelled matter is affected by the amount of SiO2. Increasing the amount of SiO2 to increase the strength of the gelled matter improves the resistance to material separation, but reduces pumpability during ground improvement work. On the other hand, the hardening reaction occurs when the metal ions contained in the ground granulated blast furnace slag dissolve in an alkaline solution (Na2O) and polymerization proceeds. However, even if the amount of SiO2 is appropriate, if the amount of Na2O is insufficient, the dissolution of the metal ions will not proceed, and the material will not harden at room temperatures of around 15 to 20°C. Therefore, preliminary tests were conducted by varying the molar ratio (SiO2 / Na2O) of sodium silicate (Na2O·nSiO2) from 2 to 3.1 and the sodium oxide (Na2O) concentration from 9.2 to 14.5%. As a result, it was confirmed that within the above ranges, bleeding was suppressed, pot life was secured, and strength was developed at room temperature, but sodium silicate with SiO2 / Na2O (molar ratio) = 2.0 and Na2O concentration of 14.1 to 14.5% was used in the main tests because it allows the amount of additive to be reduced and is more economical.

[0038] [Admixture] Preliminary tests were conducted using several types of admixtures, and it was found that two types of admixtures, the main component of which is a surfactant, were highly effective in reducing the amount of dewatering under pressure when added in small amounts, and so were used.

[0039] Next, Table 2 shows the composition of the fluid solidification material. In Table 2, the admixtures were added in proportion to the water.

[0040] [Table 2]

[0041] Next, a demonstration test performed on the ground compaction method of the present invention will be described. [Demonstration Test 1] A demonstration test was carried out on the simulated ground using the diameter expansion jig 2 shown in Figs. 2 and 3 as follows. The outer diameter of the diameter expanding wing 22 of the diameter expanding jig 2 is 216 mm in the stored state and 400 mm in the extended state. The simulated ground was sandy soil with an N value of about 5 and clayey soil with an N value of about 4. The simulated ground was drilled to GL-1.2m by rotating the boring rod 1 counterclockwise, and the ground was stirred by rotating the boring rod 1 clockwise with the expansion blade 22 of the expansion jig 2 in the protruding state, and a cylindrical loose space was formed in the ground by the expansion jig 2. Cement slurry was then ejected and filled into this space as a fluid solidification material from the lower end opening 21a of the flow path 21 of the expansion jig 2 which was attached integrally to the tip of the boring rod 1. The cement slurry had a W / C ratio of 42.3% (ordinary Portland cement), and an admixture for anchor grout was added to adjust the P flow value to 10 to 15 seconds. The cement slurry was discharged and filled at a relatively low injection pressure of about 0.2 MPa or less. The amount of cement slurry discharged was set to an amount equivalent to the volume of the cylindrical loosened space formed in the ground by the expansion jig 2 (about 100%). The boring rod 1 was pulled up (pulling distance per time: about 25 to 50 cm), the ground was stirred with the diameter expansion jig 2, and the cement slurry was discharged and filled as a fluid solidification material, which were repeated multiple times (step-up process). In the sandy soil test, the boring rod 1 was pulled up to the ground surface by the step-up process, and it was visually confirmed that the expansion wing 22 was in a protruding state (deployed state). In the test of clayey soil, when the boring rod 1 was raised to GL-0.2 m by the step-up process, the boring rod 1 was rotated left to store the expansion wing 22 of the expansion jig 2, and then the boring rod 1 was raised to the ground surface.

[0042] After the cement slurry solidified, excavation was carried out for the sandy soil and the clayey soil, respectively. The shape was confirmed. Figures 4 and 5 show the finished state of the clayey and sandy soils (ground improvement area). As shown in Figures 4 and 5, in both cases, it was confirmed that a cylindrical ground improvement section with a diameter of 400 mm was formed within the depth range where a cylindrical loosened space was formed in the ground by the diameter expansion jig 2. In addition, as shown in Figure 5, it was confirmed that outside the cylindrical ground improvement section with a diameter of 400 mm, there was a layer with a thickness of about 10 to 30 mm of a mixture of sand and cement slurry formed by part of the cement slurry permeating into the sand.

[0043] [Demonstration Test 2] A 1 / 4-scale demonstration test was conducted on a simulated ground using the expansion jig shown in Figure 6 (a rod with four expansion wings fixed radially to the lower end as an expansion jig) (hereinafter referred to as the ``rod with wings'' or ``with expansion'') and, as a comparison example, a boring rod alone (without the expansion wings as an expansion jig) (hereinafter referred to as the ``rod without wings'' or ``without expansion''). Test conditions Simulated ground: sand Diameter of the rotation path of the tip of the expanding blade: 10 cm (φ100 mm) Expected improvement diameter: 70cm / 4=17.5cm (φ175mm) Improved length per piece: 100cm (6.25cm / st x 16st = 100cm) Filling volume per unit: 1.5L / st x 16st = 24L (approximately 310% of the diameter of the rotation path at the tip of the expansion impeller x the volume of the improved length, approximately 100% of the assumed improved diameter x the volume of the improved length) Rotation speed: 44 rpm Fluid solidification material: Example 3 in Table 2 Discharge rate of fluidized solidification material: 7L / min, 14L / min as shown in Table 3

[0044] [Table 3]

[0045] Testing Procedure (1) Install rods with and without wings (2) Sand filling and water tightening (up to 1 / 2 of the total height) (3) Installation of an earth pressure gauge (Figure 7 (discharge rate of fluidized solidification material: 7 L / min), Figure 8 (discharge rate of fluidized solidification material: 14 L / min)) (4) Sand pouring and water tightening (up to the top of the formwork) (5) Embankment (6) Simulated soil pressure test *Earth pressure and ground surface displacement measurement (7) After 2 weeks, excavation is completed and the finished product is checked. (8) Core Examination Improvement procedure (1) Rod rotation (2) Pump operation begins, and injection of fluidized solidification material begins (3) 1.5L / st injection (4) Step-up 6.25cm / st (5) (3) and (4) Repeat (6) 16 steps (24L) completed (7) Pump stops, rod stops rotating (8) Raising the rod ·Excavation and as-built confirmation procedures (1) Removal of embankments (2) Pile head exposure (3) Excavation (up to 0.5m deep) (4) Collecting the earth pressure gauge (5) Excavation (up to 1m deep) - Results of simulated ground pressure test The test results are shown in FIG. 9 and Table 4, and FIG. 10 and Table 5.

[0046] [Table 4]

[0047] [Table 5]

[0048] - Consideration of earth pressure test results (1) (Figure 9 and Table 4) (1) The maximum value of horizontal earth pressure with widening is relatively larger than that without widening. (2) There is a positive correlation between the maximum horizontal earth pressure and the horizontal movement of the earth pressure gauge. (3) The greater the maximum horizontal earth pressure, the greater the residual value. (4) By combining forced widening and pressure filling, greater horizontal pressure can be applied. -Consideration of test results on ground surface displacement (1) (1) The vertical displacement of the ground surface after injection was +3 mm with diameter expansion and +5 mm without diameter expansion, which was smaller with diameter expansion. (2) By using forced widening and pressurized filling in combination, the compaction energy is distributed more horizontally. This contributes to suppressing ground surface displacement. - Consideration of earth pressure test results (2) (Figure 10 and Table 5) (1) With widening, the flowable material is pressed in concentrically, so the earth pressure increases in both V5 and V10. The vertical earth pressure (H5) is smaller than without widening, and is suppressed by using widening in combination. (2) In the case without widening, the flowable material was pressed in the direction of the V10 earth pressure gauge, resulting in larger maximum V10 earth pressure values ​​and movement amounts. -Consideration of test results on ground surface displacement (2) (1) The vertical displacement of the ground surface after injection was +3 mm with diameter expansion and +5 mm without diameter expansion, which was smaller with diameter expansion. (2) By combining forced widening and pressure filling, more compaction energy is applied in the horizontal direction, which helps to suppress ground surface displacement.

[0049] 11 to 14 show the completed state (ground improvement section) under each test condition. As shown in Figures 11 and 13, it was confirmed that with diameter expansion, a cylindrical ground improvement area of ​​φ130 to φ275 mm (+170% to +760%) (expected improvement diameter: φ175 mm) was formed in the depth range where a cylindrical loosened space of φ100 mm was formed in the ground. On the other hand, as shown in Figures 12 and 14, it was confirmed that without diameter expansion, the shape of the ground improvement area formed in the ground was distorted.

[0050] Core test results The results of various tests conducted on the cores taken from the finished shapes shown in Figures 11 and 13, obtained by test numbers (1) and (2) in Table 3 (the locations where the cores were taken are shown in Figures 15 and 16. The numbers in circles indicate the test numbers) and wet sampling samples (fluidized solidified material before and after pumping) are shown in Tables 6 and 7 and Figure 17.

[0051] [Table 6]

[0052] [Table 7]

[0053] - Discussion of core test results (Tables 6 and 7 and Figure 17) (1) Moisture content The moisture content of test number (1) was 14.9% to 18.9%, while the moisture content of test number (2) was 17.2% to 19.2%, with test number (1) tending to be lower. (2) Dry density The dry density of test number (1) is 1.71 g / cm 3 ~1.82g / cm 3 , the dry density of test number (2) is 1.70 g / cm 3 ~1.74g / cm 3 and test number (1) tends to be higher. (3) Uniaxial compressive strength The unconfined compressive strength of test number (1) is 12.2 kN / m 2 ~25.4kN / m 2 , the unconfined compressive strength of test number (2) is 10.7 kN / m 2 ~22.4kN / m 2 and the trend is almost the same. Compared to wet sampling, the unconfined compressive strength tends to be higher. (4) Filling amount of fluidized solidification material The dry density of the fluidized solidification material was 1.42 before pumping (when mixed in the plant), but after injection into the ground, it increased by 1.20 to 1.28 times, to 1.71 to 1.82, for test number (1), and by 1.09 to 1.23 times, to 1.55 to 1.74, for test number (2). Since the volume of the fluidized solidification material decreases and the dry density increases due to pressurized dehydration (reduction of voids) caused by injection, an increase of about 9 to 28% on a dry density basis is necessary to obtain the specified finished shape. The wet density of the fluidized solidification material was an average of 1.75 (1.73 to 1.77) before pumping (when mixed in the plant), but after injection into the ground, it increased by 1.14 to 1.19 times, from 1.99 to 2.09 in test number (1), and by 1.06 to 1.17 times, from 1.85 to 2.04 in test number (2). Since the volume of the fluidized solidification material decreases and the wet density increases due to pressure dehydration (reduction in water content) caused by injection, an increase of about 6 to 19% on a wet density basis is necessary to obtain the specified finished shape. (5) Dry and wet densities of fluidized solidification materials The dry density and wet density of the fluidized solidification material are greater after pressure (after pumping) than before pressure (when mixed in the plant), and are even greater after being injected into the ground (core sample).

[0054] The above describes the ground compaction method of the present invention based on its embodiment, but the present invention is not limited to the configuration described in the above embodiment, and the configuration can be changed as appropriate within the scope of the spirit of the present invention. [Industrial Applicability]

[0055] The ground compaction method of the present invention can be suitably used as a ground compaction method, since it places a small load on the pump that pressurizes the fluid solidification material, the improvement diameter that can be created is not restricted by the limit of the maximum injection pressure depending on the soil quality and stress state of the target ground, there is no risk of ground upheaval in low soil covering areas, there is a wide range of fluid solidification materials that can be used, and CO2 emissions can be reduced. [Explanation of symbols]

[0056] 1 Boring Rod 11 Flow Path 2 Expansion tool 21 Flow Path 21a Bottom opening 22 Expanded diameter wing 22a Claw part 23 Axis

Claims

1. This is a ground compaction method in which fluid solidification material is injected into the ground, filling it and compacting the surrounding ground, and includes the steps of (1) drilling a hole to a specified depth using a boring rod made of a tubular member. (2) A process of forming a cylindrical loose space in the ground by rotating an expansion jig attached to the lower end of the boring rod through the boring rod. (3) A process in which the fluid solidification material is pumped through a boring rod and discharged from the lower end opening of the boring rod into a cylindrical loosened space formed in the ground, thereby filling it. (4) A process of forming a cylindrical ground improvement portion within a specified depth range of the ground by pulling up the boring rod and performing the processes (2) and (3). (5) The process of raising the boring rod to the surface. A ground compaction method comprising the steps of:

2. The ground compaction method according to claim 1, characterized in that in step (4), the boring rod is pulled up and steps (2) and (3) are repeated a predetermined number of times to form a cylindrical ground improvement portion within a predetermined depth range of the ground.

3. The ground compaction method according to claim 1, characterized in that in step (4), the boring rod is pulled up and steps (2) and (3) are performed simultaneously to form a cylindrical ground improvement section within a specified depth range of the ground.

4. A ground compaction method according to claim 1, 2 or 3, characterized in that in step (3), a fluid solidification material is pressed and filled in an amount ranging from -10% to +1000% of the volume of the cylindrical loosened space formed in the ground in step (2).

5. 4. The ground compaction method according to claim 1, 2 or 3, characterized in that the expansion wing of the expansion jig is fixedly installed on the lower end of a boring rod.

6. 4. The ground compaction method according to claim 1, 2 or 3, characterized in that the expansion wing of the expansion jig is movably installed at the lower end of the boring rod between a protruding state and a retracted state.

7. 4. The method of claim 1, 2 or 3, wherein the inner diameter of the lower end opening of the boring rod from which the fluid solidification material is discharged is equal to or larger than the inner diameter of the boring rod.

8. The fluidized solidification material is 1 m ３ Hit CO ２ 4. The method for compacting ground according to claim 1, 2 or 3, characterized in that the discharge amount is -350 to 100 kg.

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