Grout injection method and grout injection support device

Abstract

To reduce grouting costs while efficiently improving ground.SOLUTION: An injection method of a grout material comprises: a permeability coefficient acquisition step of acquiring a permeability coefficient of the ground in a drilled hole; a grout material determination step of determining a type of grout material based on the permeability coefficient acquired in the permeability coefficient acquisition step; and a grout material injection step of injecting the type of grout material determined in the grout material determination step into the drilled hole. In the grout material determination step, when the permeability coefficient acquired in the permeability coefficient acquisition step is greater than a predetermined threshold value, the type of grout material is determined to be a first grout material generated by mixing a first cement and water, and when the permeability coefficient acquired in the permeability coefficient acquisition step is equal to or less than the threshold value, the type of grout material is determined to be a second grout material generated by mixing second cement having an average particle size smaller than the average particle size of the first cement with water.SELECTED DRAWING: Figure 2

Description

Technical Field

[0005] ,

[0001] The present invention relates to a method for injecting a grout material into the ground and an apparatus for assisting the injection of the grout material.

Background Art

[0002] In dam construction, for the purpose of enhancing the water impermeability and strength of the ground, grouting is performed to form a drilled hole in the ground and inject a grout material to close cracks in the ground. In order to enhance the effect of ground improvement by immersing the grout material up to a distance from the cracks, it has been proposed to use a plurality of different types of grout materials (Patent Document 1).

[0003] In the method disclosed in Patent Document 1, first, an ultra-fine particle cement-based grout material obtained by mixing and stirring ultra-fine particle cement in water to form a slurry is injected into the drilled hole. Next, an ultra-fine particle cement-based grout material obtained by mixing and stirring ultra-fine particle cement having an average particle diameter larger than that of the ultra-fine particle cement in water to form a slurry is injected into the same drilled hole. The previously injected ultra-fine particle cement-based grout material is pushed out to a distance from the cracks by the subsequently injected ultra-fine particle cement-based grout material. Since the ultra-fine particle cement has a smaller average particle diameter compared to the ultra-fine particle cement, it penetrates even into minute cracks, and the grout material penetrates up to a distance from the cracks.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Cement is manufactured by crushing a lump of semi-molten mineral material (also called "clinker"). Since producing cement with a smaller average particle size requires grinding the clinker more finely, cement with a smaller average particle size is more expensive.

[0006] In the method disclosed in Patent Document 1, ultrafine particle cement-based grout material is injected into all boreholes formed in the ground. This reduces watertightness and increases the strength of the ground, but on the other hand, it increases the amount of ultrafine particle cement used, thus increasing the cost of grouting.

[0007] The present invention aims to efficiently improve the ground while reducing the cost of grouting. [Means for solving the problem]

[0008] The present invention relates to a method for injecting grout into a borehole formed in the ground, comprising: a permeability coefficient acquisition step for obtaining the permeability coefficient of the ground in the borehole; a grout material determination step for determining the type of grout material based on the permeability coefficient obtained in the permeability coefficient acquisition step; and a grout material injection step for injecting the type of grout material determined in the grout material determination step into the borehole, wherein in the grout material determination step, if the permeability coefficient obtained in the permeability coefficient acquisition step is greater than a predetermined threshold, the type of grout material is set to a first grout material produced by mixing a first cement and water; and if the permeability coefficient obtained in the permeability coefficient acquisition step is less than or equal to the threshold, the type of grout material is set to a second grout material produced by mixing a second cement having an average particle diameter smaller than the average particle diameter of the first cement and water. Furthermore, the second grout material has a higher water-cement mix ratio (the ratio of the weight of water to the weight of cement) than the first grout material. .

[0009] Furthermore, the present invention is a device for assisting in the injection of grout material into a borehole formed in the ground, comprising: a permeability coefficient acquisition unit for acquiring the permeability coefficient in the borehole; and a grout material determination unit for determining the type of grout material based on the permeability coefficient acquired by the permeability coefficient acquisition unit, wherein if the permeability coefficient acquired by the permeability coefficient acquisition unit is greater than a predetermined threshold, the grout material determination unit sets the type of grout material to a first grout material produced by mixing a first cement and water; and if the permeability coefficient acquired by the permeability coefficient acquisition unit is less than or equal to the threshold, the grout material determination unit sets the type of grout material to a second grout material produced by mixing a second cement having an average particle diameter smaller than the average particle diameter of the first cement and water. Furthermore, the second grout material has a higher water-cement mix ratio (the ratio of the weight of water to the weight of cement) than the first grout material. . [Effects of the Invention]

[0010] According to the present invention, it is possible to efficiently improve the ground while reducing the cost of grouting. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram illustrating the basics of grouting. [Figure 2] This is a cross-sectional view illustrating a grout injection method according to an embodiment of the present invention, showing the state after the formation of the first area in the drilled hole has been completed. [Figure 3] This is a block diagram showing the configuration of a grout injection support device according to an embodiment of the present invention. [Figure 4] This is a cross-sectional view illustrating a grout injection method according to an embodiment of the present invention, showing the state in which the formation of the first area in another borehole has been completed. [Figure 5] This figure shows the result of injecting grout material according to Example 1 of the present invention. [Figure 6] This figure shows the results of injecting grout material according to Comparative Example 1 of the present invention. [Figure 7] This figure shows the results of injecting grout material according to Comparative Example 2 of the present invention. [Figure 8]This is a diagram showing the result of injecting grout according to Example 2 of the present invention.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0013] First, referring to FIGS. 1 to 4, the grout injection method and the grout injection support device 20 according to the present embodiment will be described. The grout injection method is used for grouting in dam construction. Grouting is performed to block cracks in the ground with grout to improve the water impermeability and strength of the ground. The grout is produced by mixing cement and water.

[0014] First, an overview of grouting will be briefly described with reference to FIG. 1. Here, as illustrated in FIG. 1, the case of performing grouting on the ground 1 in which two cracks 2a and 2b exist will be described. In FIG. 1, for the sake of convenience of explanation, the cracks 2a and 2b are drawn in a straight line, but actual cracks are curved or branched.

[0015] In grouting in dam construction, first, drilling holes 3a and 3b are formed in the ground 1. In the example shown in FIG. 1, the drilling hole 3a penetrates the crack 2a, and the drilling hole 3b penetrates the crack 2b. After the formation of the drilling holes 3a and 3b, grout 6 is injected into the drilling holes 3a and 3b. The grout 6 penetrates from the drilling holes 3a and 3b into the cracks 2a and 2b and solidifies. Thereby, the cracks 2a and 2b are blocked, and the water impermeability and strength of the ground 1 are improved.

[0016] Hereinafter, when collectively referring to the cracks 2a and 2b, they will be simply referred to as "crack 2", and when collectively referring to the drilling holes 3a, 3b, and the drilling hole 3c described later, they will be simply referred to as "drilling hole 3".

[0017] The water impermeability and strength of the ground 1 are evaluated by the water permeability in a permeability test. The larger the Lugeon value, which is the result of the permeability test, the greater the water permeability, and it is estimated that the water impermeability and strength are lower. The smaller the Lugeon value, which is the result of the permeability test, the smaller the water permeability, and it is estimated that the strength is greater.

[0018] Then, grouting is performed based on the water permeability of the ground, and a grout material 6 containing a solidifying material such as cement is injected into the ground and solidified to reduce the water permeability. That is, the water impermeability and strength are improved.

[0019] In grouting, when the water permeability is large, due to the need to reduce it to a predetermined water permeability to improve the water impermeability and strength, it is necessary to penetrate the grout material 6 to the far side of the crack 2 in the ground 1 and even into small gaps. Therefore, it is effective to use a grout material of cement with a smaller average particle size. However, the smaller the average particle size of the cement, the higher the cost.

[0020] On the other hand, in the example shown in FIG. 1, it is estimated that the water permeability of the bored hole 3a is relatively large and the crack 2a existing in the bored hole 3a is relatively large. On the other hand, it is estimated that the bored hole 3b has a relatively small water permeability and a relatively small crack 2b. In order to reduce the water permeability of the entire ground across the bored holes 3a and 3b and improve the water impermeability and strength, using a grout material 6 of cement with a small average particle size for all bored holes will cause an increase in the cost of ground improvement and is not economical.

[0021] Therefore, in this embodiment, the permeability coefficient of the ground 1 in the borehole 3 is obtained, and based on the obtained permeability coefficient, it is decided whether to use cement with a relatively large average particle size or cement with a relatively small average particle size. Then, cement with a relatively large average particle size is used in borehole 3 with a large permeability coefficient (relatively high water permeability), and cement with a relatively small average particle size is used in borehole 3 with a small permeability coefficient (relatively low water permeability). Consequently, cement with a relatively large average particle size is used in cracks 2 that are large and less prone to clogging, and cement with a relatively small average particle size is used in cracks 2 that are small and prone to clogging, allowing the grout material to penetrate the entire ground, even far beyond the cracks 2. By suitably using cement with a relatively large average particle size and cement with a relatively small average particle size, it is possible to efficiently penetrate the grout material 6 into the cracks 2 while reducing the amount of cement with a relatively small average particle size used. This makes it possible to efficiently improve the ground 1 while reducing the cost of grouting.

[0022] Referring to Figures 2 to 4, the method of injecting the grout material 6 according to this embodiment will be explained in more detail. Here, we will describe the case in which the grout material 6 is injected into the borehole 3 using the stage injection method.

[0023] In the stage injection method, the entire length of the pre-set borehole 3 (for example, 25 m) is divided vertically into sections of predetermined length (for example, 5 m) to create multiple areas (stages) within the borehole 3. Starting from the upper vertical area, drilling and grout injection are carried out sequentially, and the work progresses to the deeper areas (lower vertical areas).

[0024] Figure 2 is a cross-sectional view illustrating the method of injecting grout material 6. In the example shown in Figure 2, five zones are defined in the borehole 3, and are designated sequentially from the surface to the depths as zone 1 Z1, zone 2 Z2, ..., and zone 5 Z5. Figure 2 shows the state where zone 1 Z1 in borehole 3a has been formed and borehole 3b has not yet been formed. In Figure 2, the dashed lines indicate the final shapes of boreholes 3a and 3b. Also, the crack 2 (see Figure 1) is not shown in Figure 2.

[0025] In this embodiment, as shown in Figure 2, after the formation of the first area Z1 in the borehole 3a, the permeability coefficient in the first area Z1 of the borehole 3a is measured and obtained (permeability coefficient acquisition step). Here, the Lugeon value is measured as the permeability coefficient.

[0026] The Lugeon value is measured by a so-called Lugeon test. The Lugeon test calculates the Lugeon value based on the injection pressure and injection flow rate when water is injected into a borehole 3. A higher Lugeon value means that the borehole 3 has high permeability (water penetrates easily). In other words, a higher Lugeon value means that the impermeability and strength of the ground 1 are lower.

[0027] The Lugeon test machine 10 includes a water injection pipe 11, a pump 12 for supplying water to the water injection pipe 11, an expandable and retractable packer 13 provided near the tip of the water injection pipe 11, a flow meter 14 for measuring the flow rate of water in the water injection pipe 11, a pressure gauge 15 for measuring the water pressure in the water injection pipe 11, and a Lugeon value calculation device 16 for calculating the Lugeon value based on the flow rate and pressure measured using the flow meter 14 and the pressure gauge 15.

[0028] The Lugeon value calculation device 16 is composed of a microcomputer that includes a CPU (Central Processing Unit) for performing calculations, a ROM (Read-Only Memory) for storing control programs executed by the CPU, and a RAM (random access memory) for storing the calculation results of the CPU. The Lugeon value calculation device 16 may be composed of a single microcomputer or multiple microcomputers.

[0029] In measuring the Lugeon value in the first area Z1 of the borehole 3a, the water injection pipe 11 is inserted into the first area Z1 of the borehole 3a, and the packer 13 is expanded to close the space between the outer circumference of the water injection pipe 11 and the inner circumference of the first area Z1 of the borehole 3a. In this state, the pump 12 is driven to inject water into the first area Z1 of the borehole 3a through the water injection pipe 11, and the water flow rate and pressure are measured using the flow meter 14 and pressure gauge 15. The measured flow rate and pressure information is sent to the Lugeon value calculation device 16, and the Lugeon value is calculated by the Lugeon value calculation device 16.

[0030] After measuring the Lugeon value in the first area Z1 of the borehole 3a, the type of grout material 6 to be injected into the first area Z1 of the borehole 3a is determined based on the Lugeon value (grout material determination step). An injection support device 20 is used to determine the type of grout material 6.

[0031] The injection support device 20, like the Lugeon value calculation device 16, is composed of a microcomputer that includes a CPU (Central Processing Unit) for performing calculations, a ROM (Read-Only Memory) for storing control programs executed by the CPU, and a RAM (random access memory) for storing the CPU's calculation results. The injection support device 20 may consist of a single microcomputer or multiple microcomputers. The injection support device 20 may be incorporated into the microcomputer that makes up the Lugeon value calculation device 16.

[0032] Figure 3 is a block diagram of the injection support device 20. As shown in Figure 3, the injection support device 20 functionally comprises a permeability coefficient acquisition unit 21 and a grout material determination unit 22. The permeability coefficient acquisition unit 21 and the grout material determination unit 22 are virtual units representing the functions of the injection support device 20.

[0033] The permeability coefficient acquisition unit 21 acquires the Lugeon value calculated by the Lugeon value calculation device 16.

[0034] The grout material determination unit 22 determines the type of grout material 6 to be injected into the first area Z1 of the borehole 3a based on the Lugeon value obtained by the permeability coefficient acquisition unit 21. Specifically, if the Lugeon value is greater than a predetermined threshold (for example, 20 Lugeon), the grout material determination unit 22 determines the type of grout material 6 to be a first grout material produced by mixing first cement and water, and if the Lugeon value is less than or equal to the threshold, the grout material determination unit 22 determines the type of grout material 6 to be a second grout material produced by mixing second cement, whose average particle size is smaller than the average particle size of first cement, with water.

[0035] As the first cement, for example, blast furnace cement can be used. Blast furnace cement has an average particle size of approximately 10-20 μm and a maximum particle size of approximately 90 μm. As the second cement, which has an average particle size smaller than the average particle size of the first cement, for example, ultrafine particle cement can be used. Ultrafine particle cement has an average particle size of approximately 4 μm.

[0036] For the average particle size of cement, for example, the average of the equivalent spherical diameter obtained by the optical scattering method specified in JIS Z 8901, and the average of the equivalent circular diameter obtained by the microscopy method specified in JIS Z 8901 can be used.

[0037] The type of grout material 6 determined by the grout material determination unit 22 is displayed on the monitor 30. The worker checks the monitor 30 and prepares the determined type of grout material 6.

[0038] Subsequently, the determined type of grout material 6 is injected into the first area Z1 of the borehole 3a (grout injection step). A grout injection device (not shown) is used to inject the grout material 6. The grout material 6 penetrates from the first area Z1 of the borehole 3a into the crack 2 (see Figure 1). This seals the crack 2, increasing the watertightness and strength of the ground 1.

[0039] With the above steps, the injection of grout material 6 into the first area Z1 of the borehole 3a is completed.

[0040] Subsequently, drilling, measurement of Lugeon values, and injection of grout material 6 are repeated sequentially from the second zone Z2 to the fifth zone Z5 of the borehole 3a. This completes the injection of grout material 6 into the first to fifth zones Z1 to Z5 of the borehole 3a.

[0041] When the injection of grout material 6 into the first area Z1 of the borehole 3a is completed, the first area Z1 of the borehole 3a is filled with grout material 6. Therefore, when forming the second area Z2 of the borehole 3a, the grout material 6 that has been filled into the first area Z1 of the borehole 3a will be drilled. Similarly, when forming the third area Z3, fourth area Z4, and fifth area Z5 of the borehole 3a, the grout material 6 that has been filled into the second area Z2, third area Z3, and fourth area Z4 of the borehole 3a will be drilled, respectively.

[0042] After the injection of grout material 6 into the first to fifth zones Z1 to Z5 of borehole 3a is completed, grout material 6 is injected into the first to fifth zones Z1 to Z5 of borehole 3b. The procedure for injecting grout material 6 into borehole 3b is the same as the procedure for injecting grout material 6 into borehole 3a, so the details are omitted here.

[0043] Thus, in this embodiment, the type of grout material 6 injected into the boreholes 3a and 3b is determined based on the Lugeon value. Therefore, a first cement with a relatively large average particle size is used for cracks 2 with a high permeability coefficient (relatively high water permeability) and relatively low clogging, while a second cement with a relatively small average particle size is used for cracks 2 with a low permeability coefficient (relatively low water permeability) and high clogging. Consequently, the amount of second cement with a relatively small average particle size used can be reduced while efficiently penetrating the grout material 6 into the cracks 2. This makes it possible to efficiently improve the ground 1 while reducing the cost of grouting.

[0044] Furthermore, the borehole 3 is divided into five zones Z1 to Z5, the Lugeon value is measured for each of the five zones Z1 to Z5, and the type of grout material 6 is determined for each of the five zones Z1 to Z5. Therefore, for each of the five zones Z1 to Z5 in the borehole 3, a type of grout material 6 is used that corresponds to the likelihood of clogging in the cracks 2. Consequently, the grout material 6 can be penetrated into the cracks 2 more efficiently while reducing the amount of cement used, which has a relatively small average particle size. This makes it possible to improve the ground 1 more efficiently while further reducing the cost of grouting.

[0045] After the injection of grout material 6 into boreholes 3a and 3b is completed, in order to confirm the permeability of the ground extending between boreholes 3a and 3b and to confirm the effect of the grout material 6 injection, a borehole 3c is formed between boreholes 3a and 3b, as shown in Figure 4, and the Lugeon value in borehole 3c is measured. The Lugeon value in borehole 3c is measured in each of the 1st to 5th zones Z1 to Z5, similar to the measurement of boreholes 3a and 3b. Figure 4 shows the state in which the Lugeon value in the 1st zone Z1 of borehole 3c is being measured. In Figure 4, the dashed line indicates the final shape of borehole 3c.

[0046] The Lugeon value in the borehole 3c is compared with a Lugeon value that determines the type of grout material 6 (in this embodiment, a threshold of, for example, 20 Lugeon), as well as a reference value (for example, 5 Lugeon) used to determine whether the impermeability and strength of the ground 1 have reached a level suitable for a dam, i.e., a reference value (for example, 5 Lugeon) that is smaller than a predetermined threshold (for example, 20 Lugeon).

[0047] If the Lugeon value in the borehole 3c is below the standard value, the impermeability and strength of the ground 1 are deemed to have reached the level suitable for a dam, and the grouting is completed after injecting grout material 6 into the borehole 3c to seal it. The impermeability and strength of the ground 1 are deemed to have reached the standard if the Lugeon value is below the standard value in all of the first to fifth zones Z1 to Z5 in the borehole 3c, or if the Lugeon value is below the standard value in a predetermined proportion (e.g., 60%) or more of the first to fifth zones Z1 to Z5 in the borehole 3c. It is preferable that the grout material 6 injected when the Lugeon value is below the standard value is a second grout material produced by mixing a second cement, whose average particle size is smaller than the average particle size of the first cement, with water.

[0048] If the Lugeon value in the borehole 3c is greater than the standard value, the impermeability and strength of the ground 1 are considered insufficient for a dam, and grouting is continued. Specifically, grout material 6 is injected into the borehole 3c with the aim of increasing the impermeability and strength of the ground 1. At this time, the type of grout material 6 is determined based on the Lugeon value, similar to the grout material 6 injected into boreholes 3a and 3b. Therefore, even when injecting grout material 6 into borehole 3c, it is possible to efficiently penetrate the cracks 2 with grout material 6 while reducing the amount of cement used, which has a relatively small average particle size.

[0049] Subsequently, in order to confirm the effect of injecting grout material 6 into borehole 3c, additional boreholes (not shown) are formed between borehole 3a and borehole 3c, and between borehole 3b and borehole 3c, and the Lugeon value in the additional boreholes is measured. If the Lugeon value in the additional boreholes is below the standard value, it is determined that the impermeability and strength of the ground 1 have reached the level suitable for a dam. In this case, grout material 6 is injected into the additional boreholes to seal them, and the grouting is completed.

[0050] If the Lugeon value in the additional borehole is greater than the standard value, grouting is continued. The type of grout material 6 injected into the additional borehole is determined based on the Lugeon value, similar to the grout material 6 injected into boreholes 3a and 3b. Therefore, until the impermeability and strength of the ground 1 reach the standard, the amount of cement used, which has a relatively small average particle size, can be reduced while efficiently penetrating the cracks 2 with grout material 6.

[0051] Even if the Lugeon value in the borehole 3c is below the standard value, if necessary, additional boreholes may be formed in the ground 1, the Lugeon value may be measured, and grout material 6 may be injected.

[0052] According to the above embodiments, the following effects and advantages are achieved.

[0053] In this embodiment, when the Lugeon value in the borehole 3 is below a threshold, a second grout material is used, which is a mixture of water and a second cement, the second cement having an average particle size smaller than the average particle size of the first cement. Therefore, the first cement with a relatively large average particle size is used for cracks 2 with a relatively large Lugeon value, a high permeability coefficient (relatively high water permeability), and that are less prone to clogging. Conversely, the second cement with a relatively small average particle size is used for cracks 2 with a relatively small Lugeon value, a low permeability coefficient (relatively low water permeability), and that are prone to clogging. Thus, the amount of second cement with a relatively small average particle size used can be reduced while efficiently penetrating the grout material 6 into the cracks 2. This makes it possible to efficiently improve the ground 1 while reducing the cost of grouting.

[0054] Furthermore, in this embodiment, if the Lugeon value in the borehole 3c is greater than the reference value used to determine whether the impermeability and strength of the ground 1 are at or have reached the standard impermeability and strength, an additional borehole is formed in the ground 1, and the steps of obtaining the permeability coefficient, determining the grout material, and injecting the grout material are repeated for the additional borehole. Therefore, even in the additional borehole, the first cement with a relatively large average particle size is used for cracks 2 that have a relatively large Lugeon value and a large permeability coefficient (relatively high water permeability) and are less prone to clogging, while the second cement with a relatively small average particle size is used for cracks 2 that have a relatively small Lugeon value and a small permeability coefficient (relatively low water permeability) and are prone to clogging. Thus, until the impermeability and strength of the ground 1 reach the standard, the amount of the second cement with a relatively small average particle size can be reduced while efficiently infiltrating the cracks 2 with the grout material 6. This makes it possible to efficiently improve the ground 1 while reducing the cost of grouting. In the grouting process, even if the initial grouting step involves injecting cement grout material 6 (first grout material) with a relatively large average particle size, the subsequent grouting step involves injecting cement grout material 6 (second grout material) with a relatively small average particle size. This reduces costs and lowers the overall permeability of the ground.

[0055] Furthermore, in the step of obtaining the permeability coefficient, the borehole 3 is divided into five zones Z1 to Z5, and the Lugeon value is measured for each of the five zones Z1 to Z5. In the step of determining the grout material, the type of grout material 6 is determined for each of the five zones Z1 to Z5. Therefore, for each of the five zones Z1 to Z5 in the borehole 3, a type of grout material 6 corresponding to the permeability coefficient (permeability) of the crack 2 is used. Consequently, the grout material 6 can be penetrated into the crack 2 more efficiently while reducing the amount of second cement with a relatively small average particle size used. This makes it possible to improve the ground 1 more efficiently while further reducing the cost of grouting.

[0056] In the above embodiment, the second grout material, which is produced by mixing a second cement having a relatively small average particle size with water, may have a water-cement ratio, which is the ratio of the weight of water to the weight of cement, that is greater than that of the first grout material. In this case, the fluidity of the second grout material becomes higher than that of the first grout material, and the highly fluid second grout material is used in cracks 2, which have a relatively small Lugeon value and are prone to clogging. Therefore, the grout material 6 can penetrate into the cracks 2 more efficiently.

[0057] Furthermore, in the above embodiment, if the Lugeon value is below the threshold, instead of injecting only the second grout material into the borehole 3, the first grout material may be injected into the same borehole 3 after injecting the second grout material.

[0058] Furthermore, the water-cement ratio of the grout material 6 is not limited to a constant value. As the amount of grout material 6 injected increases, grout material 6 with a lower water-cement ratio may be injected into the borehole 3. Specifically, grout material 6 with a water-cement ratio of 10 may be injected into the borehole 3 first, and then grout material 6 with a water-cement ratio of 8 may be injected into the borehole 3.

[0059] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0060] <Examples and Comparative Examples> The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0061] <Example 1> First, we will describe Example 1. In Example 1, grouting was performed using formulation / amount flow A shown in Table 1 when the rugeon value was 20 rugeon or less, and using formulation / amount flow B shown in Table 2 when the rugeon value exceeded 20 rugeon.

[0062] [Table 1]

[0063] [Table 2]

[0064] The ordinary particle cement in Tables 1 and 2 is cement with an average particle diameter of approximately 10 to 20 μm, measured by the light scattering method or microscopy method specified in JIS Z 8901, and corresponds to the first cement in the above embodiment. The fine particle cement in Table 1 is cement with an average particle diameter of approximately 4 μm, measured by the light scattering method or microscopy method specified in JIS Z 8901, and corresponds to the second cement in the above embodiment.

[0065] In the mix and volume flow A shown in Table 1, first, grout material MF1 (grout material produced by mixing fine particle cement and water with a water-cement ratio of 10) is injected into the borehole. When the amount of grout material MF1 injected reaches the upper limit of 400 liters, the grout material is switched from grout material MF1 to grout material MF2 (grout material produced by mixing fine particle cement and water with a water-cement ratio of 8) and injected into the borehole. When the amount of grout material MF2 injected reaches the upper limit of 600 liters, the grout material is switched from grout material MF2 to grout material F3 (grout material produced by mixing ordinary particle cement and water with a water-cement ratio of 6) and injected into the borehole. Similarly, each time the injection volume reaches its upper limit, the grout material is switched from grout material F3 to grout material F4, from grout material F4 to grout material F5, and from grout material F5 to grout material F6, and injected into the borehole. The injection is terminated when the injection volume of grout material F6 reaches its upper limit of 400 liters, or when the injection pressure reaches a predetermined pressure during the injection of grout materials MF1, MF2, F3, F4, F5, and F6.

[0066] In the mix and volume flow B shown in Table 2, first, grout material F3 (grout material produced by mixing ordinary particle cement and water with a water-cement ratio of 6) is injected into the borehole. When the amount of grout material F3 injected reaches the upper limit of 400 liters, the grout material is switched from grout material F3 to grout material F4 (grout material produced by mixing ordinary particle cement and water with a water-cement ratio of 4) and injected into the borehole. Similarly, each time the injection volume reaches the upper limit, the grout material is switched from grout material F4 to grout material F5, and from grout material F5 to grout material F6, and injected into the borehole. The injection is terminated when the amount of grout material F6 injected reaches the upper limit of 1200 liters, or when the injection pressure reaches a predetermined pressure during the injection of grout materials F3, F4, F5, and F6.

[0067] Figure 5 shows the simulation results of grouting performed by using the formulation and quantity flows A and B shown in Tables 1 and 2, respectively, based on the Lugeon value.

[0068] In Figure 5, the 1-1st primary drilling hole corresponds to drilling holes 3a and 3b shown in Figures 2 and 4, and the 1-2nd primary drilling hole corresponds to drilling hole 3c shown in Figure 4. The 2nd primary drilling hole corresponds to the additional drilling hole in the above embodiment.

[0069] In both the primary and primary drilled holes, the Lugeon value was 25 Lugeon, so grout was injected using mix and volume flow B. The amount of grout injected was 1800 liters in both primary and primary drilled holes, and the amount of ordinary particle cement used was 718.8 kg in both primary and primary drilled holes.

[0070] The Lugeon value in the primary and secondary boreholes was 18 Lugeon, so grout was injected using mix design / volume flow A. The injection volume was 2600 liters, with 110.8 kg of fine particle cement and 632.4 kg of ordinary particle cement used.

[0071] Since the Lugeon value in the primary and secondary boreholes was greater than the standard value (5 Lugeon), secondary boreholes were formed, and the permeability coefficient (water permeability) of the ground was checked after injecting grout material into the primary and secondary boreholes. In both secondary boreholes, the Lugeon value was 4 Lugeon, which was below the standard value. Therefore, the permeability coefficient (water permeability) was reduced, and the required watertightness and strength were ensured. As a result, grout material was injected into the secondary boreholes, and the grouting was completed. The amount of grout material injected into both secondary boreholes was 1400 liters, with 110.8 kg of fine particle cement and 63.2 kg of ordinary particle cement used. In the simulation of Example 1, it is preferable to inject grout material into the secondary boreholes using mix / volume flow A, but it is also acceptable to inject grout material using mix / volume flow B.

[0072] In Example 1, the total amount of fine particle cement used was 332.4 kg, and the total amount of ordinary particle cement used was 2196.4 kg. The total amount of cement used was 2528.8 kg.

[0073] <Comparative Example 1> In Comparative Example 1, grouting was performed on the same ground as in Example 1, using the mix and quantity flow A shown in Table 1, regardless of the Lugeon value. In other words, grouting was performed using fine particle cement regardless of the permeability of the ground. The simulation results for Comparative Example 1 are shown in Figure 6.

[0074] In Figure 6, the 1-1st primary drilling hole, the 1-2nd primary drilling hole, and the 2nd primary drilling hole correspond to the drilling holes 3a and 3b shown in Figures 2 and 4, the drilling hole 3c shown in Figure 4, and the additional drilling hole in the above embodiment, similar to Example 1.

[0075] When grout material was injected into each of the primary boreholes using mix and volume flow A, the amount of grout material injected into both primary boreholes was 2600 liters, with 110.8 kg of fine particle cement used and 632.4 kg of ordinary particle cement used.

[0076] When grout material was injected into the primary and secondary drilled holes using mix and volume flow A, the total amount of grout material injected was 2600 liters, with 110.8 kg of fine particle cement and 632.4 kg of ordinary particle cement used.

[0077] The Lugeon value in the primary and secondary boreholes was 12, which was higher than the standard value (5 Lugeon). Therefore, secondary boreholes were formed, and the permeability coefficient (water permeability) of the ground was checked after injecting grout into the primary and secondary boreholes. In both secondary boreholes, the Lugeon value was 3 Lugeon, which was below the standard value. Therefore, grout was injected into the secondary boreholes, and the grouting was completed. The amount of grout injected into both secondary boreholes was 1200 liters, with 110.8 kg of fine particle cement and 31.6 kg of ordinary particle cement used. In the simulation of Comparative Example 1, it is preferable to inject grout into the secondary boreholes using mix / volume flow A, but it is also acceptable to inject grout using mix / volume flow B.

[0078] In Comparative Example 1, the total amount of fine particle cement used was 554.0 kg, and the total amount of ordinary particle cement used was 1960.4 kg. The total amount of cement used was 2514.4 kg.

[0079] The total amount of cement used in Comparative Example 1 was 14.4 kg (= 2528.8 kg - 2514.4 kg) less than the total amount of cement used in Example 1, while the total amount of fine particle cement used in Comparative Example 1 was 221.6 kg (= 554.0 kg - 332.4 kg) more than the amount of fine particle cement used in Example 1. In other words, the amount of fine particle cement used in Example 1 was reduced compared to Comparative Example 1. Therefore, it was confirmed that the cost of grouting could be reduced.

[0080] <Comparative Example 2> In Comparative Example 1, grouting was performed on the same ground as in Example 1, using the mix and quantity flow C shown in Table 3, regardless of the Lugeon value. In other words, grouting was performed using ordinary particle cement regardless of the permeability of the ground. The simulation results for Comparative Example 2 are shown in Figure 7.

[0081] [Table 3]

[0082] The ordinary particle cement in Table 3 is the same as the ordinary particle cement in Tables 1 and 2. The injection procedure in mix design / volume flow C is almost the same as the injection procedure in mix design / volume flows A and B, so its explanation is omitted here.

[0083] When grout material was injected into each of the primary boreholes using the mix and volume flow C, the injection volume was 2600 liters in both primary boreholes, and the amount of ordinary particle cement used was 743.2 kg.

[0084] When grout material was injected into the primary and secondary drilled holes using the mix and volume flow C, the injection volume was 2200 liters, and the amount of ordinary particle cement used was 439.6 kg.

[0085] The Lugeon value in the primary and secondary boreholes was 15, which was higher than the standard value. Therefore, secondary boreholes were formed, and the permeability coefficient (water permeability) of the ground was checked after injecting grout material into the primary and secondary boreholes.

[0086] In both secondary boreholes, the Lugeon value was 6 Lugeon, which is higher than the standard value, indicating that the grouting effect was insufficient when grout was injected into the 1-1 and 1-2 secondary boreholes. Therefore, ground improvement was carried out by injecting grout into the secondary boreholes, and tertiary boreholes were formed and the Lugeon value in the tertiary boreholes was measured to confirm the permeability coefficient (water permeability) of the ground after grout was injected into the 1-1, 1-2, and secondary boreholes.

[0087] The amount of grout injected into each of the secondary boreholes was 1200 liters, and the amount of ordinary particle cement used was 142.4 kg.

[0088] The Lugeon values ​​in all of the tertiary boreholes were 4, which is below the standard value. Therefore, grout material was injected into the tertiary boreholes, and the grouting process was completed. The amount of grout material injected into each of the tertiary boreholes was 700 liters, and the amount of ordinary particle cement used was 74.8 kg.

[0089] In Comparative Example 2, the total amount of ordinary particle cement used was 2510.0 kg.

[0090] In Example 1, the Lugeon value fell below the standard value by injecting grout into the 1-1 and 1-2 secondary boreholes. However, in Comparative Example 2, it was necessary to inject grout into the secondary boreholes to bring the Lugeon value below the standard value. In other words, the number of additional boreholes required in the example was reduced compared to Comparative Example 2. Therefore, it was confirmed that the ground could be improved efficiently.

[0091] <Example 2> In Example 2, grouting was performed on a different ground than that used in Example 1. When the Lugeon value was 20 Lugeon or less, mix and volume flow A shown in Table 1 was used, and when the Lugeon value exceeded 20 Lugeon, mix and volume flow B shown in Table 2 was used. The simulation results for Comparative Example 2 are shown in Figure 8.

[0092] The Lugeon value in each of the primary boreholes was 25 Lugeon, so grout was injected using mix and volume flow B. The injection volume for both primary boreholes was 2600 liters, and the amount of ordinary particle cement used was 743.2 kg.

[0093] The Lugeon value in the primary and secondary boreholes was 4 Lugeon, which was below the standard value. Therefore, grout material was injected into the primary and secondary boreholes, and the grouting process was completed. The amount of grout material injected into the primary and secondary boreholes was 1600 liters, with 110.8 kg of fine particle cement and 109.6 kg of ordinary particle cement used.

[0094] In Example 2, the grouting effect was sufficient with only the injection of grout material into the 1-1 primary drilling hole, and the grouting could be completed without forming a secondary drilling hole. Therefore, it was confirmed that the ground could be improved efficiently. In the simulation of Example 2, it is preferable to inject the grout material into the 1-2 primary drilling hole using mix and volume flow A, but it is also possible to inject the grout material using mix and volume flow B.

[0095] <Example 3> In Example 3, the primary drilled hole was divided into three sections, the Lugeon value was obtained for each section, and for each section, it was decided whether to use mix / volume flow A shown in Table 1 or mix / volume flow B shown in Table 2, and then grouting was performed.

[0096] Although not shown in the diagram, in the first zone (the zone closest to the ground surface) of the 1-1 primary borehole, the Lugeon value was 25, so grout was injected using mix and volume flow B. In the second zone (the zone next closest to the ground surface after the first zone) and the third zone (the zone furthest from the ground surface), the Lugeon value was 15, so grout was injected using mix and volume flow A.

[0097] In the primary and secondary drilled holes, the area was divided into three zones, and the Lugeon value was obtained for each zone. Since the Lugeon value was below the standard value in all zones, grout material was injected into the primary and secondary drilled holes, and the grouting was completed.

[0098] In Example 3, the grouting effect was sufficient with only the injection of grout material into the primary borehole, and the grouting could be completed without forming secondary boreholes. Therefore, it was confirmed that the grout material could penetrate the cracks more efficiently while further reducing the amount of cement used, which has a relatively small average particle size. [Explanation of symbols]

[0099] 1...ground 3, 3a, 3b, 3c...Drilling holes 6. Grout material 20...Injection support device 21. Permeability coefficient acquisition section 22. Grout material selection section

Claims

1. A method for injecting grout material into boreholes formed in the ground, A step to obtain the permeability coefficient of the ground in the borehole, A grout material determination step in which the type of grout material is determined based on the permeability coefficient obtained in the permeability coefficient acquisition step, The process includes a grout injection step in which the type of grout determined in the grout determination step is injected into the borehole, In the grout material determination step, if the permeability coefficient obtained in the permeability coefficient acquisition step is greater than a predetermined threshold, the type of grout material is set to a first grout material produced by mixing first cement and water, and if the permeability coefficient obtained in the permeability coefficient acquisition step is less than or equal to the threshold, the type of grout material is set to a second grout material produced by mixing second cement, whose average particle size is smaller than the average particle size of the first cement, and water. The second grout material has a water-cement mix ratio, which is the ratio of the weight of water to the weight of cement, that is greater than that of the first grout material. Method of injecting grout material.

2. After the grout injection step, additional boreholes are formed in the ground, and the permeability coefficient in the additional boreholes is obtained. If the permeability coefficient in the additional borehole is less than or equal to the threshold and greater than a reference value less than the threshold, the grout material determination step and the grout material injection step are repeated for the additional borehole. The method for injecting grout material according to claim 1.

3. In the step of obtaining the permeability coefficient, the borehole is divided into multiple areas, and the permeability coefficient is obtained for each area. In the step of determining the grout material, the type of grout material is determined for the area. The method for injecting grout material according to claim 1.

4. A device that assists in injecting grout material into boreholes formed in the ground, A unit for obtaining the permeability coefficient in the borehole, The system includes a grout material determination unit that determines the type of grout material based on the permeability coefficient obtained in the aforementioned permeability coefficient acquisition unit, The grout material determination unit determines the type of grout material to be a first grout material produced by mixing first cement and water if the permeability coefficient obtained in the permeability coefficient acquisition unit is greater than a predetermined threshold, and determines the type of grout material to be a second grout material produced by mixing second cement, whose average particle size is smaller than the average particle size of the first cement, with water. The second grout material has a water-cement mix ratio, which is the ratio of the weight of water to the weight of cement, that is greater than that of the first grout material. A device to assist in the injection of grout material.

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