Ground improvement methods

Abstract

To effectively utilize an excess solidification material (sludge).SOLUTION: A ground improvement method using a high pressure injection agitation method for injecting a solidification material from a double pipe rod 18 (rotary injection pipe) into the ground, and establishing an improvement body 24, includes: a collection step of collecting an excess solidification material 22 discharged at the time of establishment of a ground improvement body; a measurement step of measuring the property of the collected excess solidification material 22 as an index of a strength of the excess solidification material 22; and an excess solidification material strength estimation step of estimating the strength of the solidified excess solidification material 22, on the basis of the measured property of the excess solidification material 22.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a ground improvement method using a high-pressure jet mixing method, and in particular to the handling of excess solidification material generated during construction. [Background technology]

[0002] A known method for improving ground is a high-pressure injection and mixing method in which a solidifying material is injected into the ground from a rotary injection pipe to create an improved body. Also known is a technique for ensuring the quality of the improved body by measuring at least one of the specific gravity, viscosity, and type and amount of contained elements of the waste mud and / or unconsolidated improved body discharged during the creation of the improved body (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-157551 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, if the quality of the improved soil can be quickly estimated by measuring the properties of the sludge, it is easy to manage and ensure the quality of the improved soil in real time. However, even if the quality of the improved soil is improved, the sludge discharged during construction is still sucked up and removed by a vacuum truck or other device, and transported to an industrial waste treatment plant for treatment. This means that costs such as transportation and treatment fees are incurred.

[0005] The present invention has been made in consideration of the above points, and aims to enable the effective use of waste sludge (hereinafter, in this invention, waste sludge will be referred to as "excess solidification material"), thereby reducing costs such as transportation costs and processing costs. [Means for solving the problem]

[0006] To achieve the above objectives, The present invention provides A ground improvement method using a high-pressure injection mixing method in which a solidification material is injected into the ground from a rotary injection pipe to create an improved body, A collection process of collecting surplus solidification material discharged during the construction of the ground improvement body; a measuring step of measuring properties of the collected surplus solidification material, which are indicators of the strength of the surplus solidification material; an excess solidification material strength estimation step of estimating the strength of the excess solidification material after solidification based on the measured properties of the excess solidification material; The present invention is characterized by having the following.

[0007] This makes it easy to control the strength of the surplus solidification material itself, and therefore it can be easily used effectively, for example, as backfill material that requires a certain strength. [Effects of the Invention]

[0008] The present invention makes it possible to effectively utilize surplus solidification material, thereby reducing costs such as transportation costs and disposal costs. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram showing the outline of the process of a high-pressure injection mixing method. [Figure 2] FIG. 10 is a cross-sectional plan view showing a schematic example of a space where excess solidification material is backfilled. [Figure 3] FIG. 10 is a cross-sectional elevation view showing a schematic example of a space where excess solidification material is backfilled. [Figure 4] FIG. 10 is a cross-sectional elevation view showing a schematic example of another space where excess solidification material is backfilled. [Figure 5] 1 is a flowchart showing the main steps of quality control in the reuse of surplus solidification material in a ground improvement method. [Figure 6] 1 is a graph showing an example of the relationship between strength, density, and calcium content of surplus solidification material. [Figure 7] 10 is a graph showing an example of strength depending on the density and calcium content of excess solidification material. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0011] (General procedure for ground improvement using the high-pressure jet mixing method) First, referring to Figure 1, we will explain the general procedure for ground improvement using the high-pressure jet mixing method.

[0012] First, as shown in Figure 1 (1), a ground improvement device 12 is placed on the ground surface 10, and a vertical hole 16 is drilled to the planned depth by lowering the boring rod 14 at a predetermined speed while injecting high-pressure drilling water from the tip of the boring rod 14.

[0013] Next, as shown in Figure 1 (2), a double-tube rod 18 is installed in the vertical hole 16, and then, as shown in Figure 1 (3), a mixture of solidification material and water is sprayed at high pressure from a nozzle formed on the side of the tip of the double-tube rod 18 while it is rotated, and it is raised to the planned depth at a predetermined speed.

[0014] As a result, as shown in FIG. 1(4), a cylindrical improved body 24 (pile body) is formed, which is a mixture of the excavated soil, water, and solidification material.

[0015] In this construction, excess solidification material 22, which is a mixture of excavated ground, water, and solidification material, is discharged to the ground through the gap between the double-tube rod 18 and the vertical hole 16 and stored in the slime pit 20.

[0016] The ground improvement work may be terminated upon completion of the above construction, but it may also be possible to carry out multiple constructions in addition to the above construction, in which solidifying material and water are sprayed and mixed at high pressure at the same location before the improved body 24 solidifies, in order to improve the quality of the improved body 24.

[0017] (Disposal of excess solidification material 22) The excess solidification material 22 discharged to the ground during construction of the above-mentioned improved body 24 and stored in the slime pit 20 can be sucked and removed by a vacuum truck (not shown) or used to backfill a space that is created when a new structure is constructed above an existing structure with an improved body 24 constructed directly below it. In particular, if the present invention is applied, by controlling the strength (uniaxial compressive strength) of the excess solidification material 22 as described below, it can be used as a filler material to backfill a space that requires a certain strength.

[0018] Specifically, when a new structure 32 is constructed nested within an existing structure 30 constructed underground, as shown in Figures 2 and 3, backfill areas 34, such as spaces between the walls of the two structures and spaces between the pressure plates of the two structures, are backfilled. If the new structure 32 is to be supported by backfilling such backfill areas 34, the backfilling material must have a predetermined strength. Therefore, the surplus solidification material 22 according to the present invention can be used as the backfilling material.

[0019] The backfilling described above is not limited to the underground portion of a structure, but can also be applied to the backfilling of the backfilled area 34 on the ground surface, for example, when a new structure 32 is constructed in a nested manner while leaving an existing structure 30 exposed above the ground surface 10 as shown in Figure 4.

[0020] (Quality control of surplus solidification material 22) First, an outline of the quality control of the surplus solidification material 26 will be explained.

[0021] The improved ground constructed using the high-pressure jet mixing method is a mixture of cement or cement-based solidification material, water, and soil, and its strength (uniaxial compressive strength) depends on the amount of solidification material added.

[0022] Generally, cement or cement-based solidification materials are primarily composed of calcium oxide (calcium silicate mineral), so the amount of solidification material added is proportional to the calcium content, and therefore, it can be said that the unconfined compressive strength is also proportional to the calcium content.

[0023] Therefore, strength can be evaluated by measuring the calcium content of the surplus solidification material 22. In the reuse of the surplus solidification material 22 in this embodiment, when the calcium content of the surplus solidification material 22 changes, the ratio of water to soil also changes, and since the ratio of water to soil is reflected in the density, strength is estimated from the relationship between density and calcium content.

[0024] Specifically, the quality control of the surplus solidifying material 22 is carried out as shown in FIG.

[0025] (S11) First, as a test construction, surplus solidification material 22 is collected in the same manner as in the actual construction. More specifically, as explained in Figure 1 (3) (4) above, a mixture of solidification material and water is sprayed at high pressure from the side of the tip of the double-tube rod 18 while rotating and raising it, and the surplus solidification material 22, which is a mixture of the excavated ground, water, and solidification material discharged to the ground, is collected.

[0026] (S12) Using the collected surplus solidification material 22, an indoor mix test is conducted to measure the unconfined compressive strength after solidification for a predetermined number of days, such as four weeks, for multiple mix ratios of the soil to be improved, the solidification material, and water. A strength-property relationship is then calculated, which is the relationship between the strength and the properties of the surplus solidification material 22. More specifically, the correlation between calcium content (Ca content) and unconfined compressive strength is examined for a given density, and the measured strength is plotted as shown in Figure 6. An acceptance strength line is then created to evaluate the strength of the surplus solidification material 22, and the intersections (three points) of the set acceptance strength and the lines for each density are determined. In a graph of calcium content versus density, such as that shown in Figure 7, the regression line of these intersections becomes the set acceptance strength line. Here, by determining the calcium content and density distribution above and to the right of the pass / fail strength line as the pass range (both Ca content and density are increasing), and determining the distribution below and to the left as the fail range (both Ca content and density are decreasing), it is possible to easily determine the combination of calcium content and density that satisfies the specified set pass / fail strength.

[0027] (S13) After that, when the construction of the ground improvement by the high-pressure jet mixing method is started, the excess solidification material 22 discharged onto the ground during the construction of the ground improvement body 28 is collected.

[0028] (S14) Then, the properties of the collected excess solidification material 22, i.e., the calcium content and density, are measured. There are no particular limitations on the method for measuring the calcium content, but it can be easily measured using, for example, a fluorescent X-ray analyzer or the like.

[0029] (S15) Based on the measured calcium content and density and the strength-property relationship calculated in advance as described above, the strength of the excess solidification material 22 is estimated, i.e., it is determined whether it has the predetermined set pass strength.

[0030] (S16) If it is confirmed that the excess solidification material 22 has the predetermined set passability strength, the excess solidification material 22 is used as a filler material for the backfilled area 34 that requires the predetermined strength.

[0031] (S17) On the other hand, if it is determined that the surplus solidification material 22 does not have the predetermined pass / fail strength, it may be removed and disposed of by a vacuum truck or the like, as in normal sludge disposal, or used as filler for backfilling areas that do not require strength. However, it may also be used for backfilling after adding solidification material and increasing the calcium content to achieve a predetermined strength or higher. This allows for more effective use of the surplus solidification material 22. Note that adjustment of the surplus solidification material 22 is not limited to adding solidification material to increase strength, but may also include adding water to reduce the strength in order to balance it with the required design strength.

[0032] (Other matters) If the amount of quality-controlled excess solidification material 22 is less than the amount required for backfilling, it may be used in combination with other filler materials mixed at a different plant. However, it may not be desirable to mix filler materials with different properties (strengths) in the same backfilling area. In such cases, the backfilling area may be divided into sections, and each section may be filled with a different filler material.

[0033] Furthermore, even when quality control of the excess solidification material 22 as described above is performed, the backfilled excess solidification material 22 may be sampled after it has developed strength and subjected to a uniaxial compression test to confirm whether the uniaxial compressive strength of the backfilled excess solidification material 22 satisfies the design value.

[0034] Furthermore, in order to check the adhesion between the surplus solidification material 22 backfilled in the backfilled area 34 and the newly constructed structure 32, core boring may be performed on the surplus solidification material 22 and a uniaxial compression test may be performed.

[0035] By controlling the quality of the excess solidification material 22 as described above and using it for backfilling, etc., the area in which the excess solidification material 22 can be backfilled can be expanded, and the transportation costs and processing costs of transporting it to the industrial waste disposal site, as well as the costs of filler and its transportation costs that would be required separately if the quality is not controlled, can be reduced, thereby contributing to reducing the environmental burden.

[0036] In addition, by conducting a mixing test in advance and determining the strength after solidification for several different mixtures of the soil to be improved, the solidification material, and water, the strength-property relationship, which is the relationship between the strength of the surplus solidification material 22 and the properties of the surplus solidification material 22, it is possible to quickly manage the strength of the surplus solidification material 22 during the ground improvement work based on this. [Explanation of symbols]

[0037] 10 Earth's surface 12 Ground improvement equipment 14 Boring Rod 16 Vertical hole 18 Double tube rod (rotating injection tube) 20 Slime Pit 22 Excess solidification material 24 Improved body 30 Existing Structures 32 Newly constructed structures 34 areas

Claims

1. A ground improvement method using a high-pressure injection mixing method in which a solidification material is injected into the ground from a rotary injection pipe to create an improved body, A collection process of collecting surplus solidification material discharged during the construction of the ground improvement body; a measuring step of measuring properties of the collected surplus solidification material, which are indicators of the strength of the surplus solidification material; an excess solidification material strength estimation step of estimating the strength of the excess solidification material after solidification based on the measured properties of the excess solidification material; and Furthermore, the method includes a strength-property relationship setting step of determining a strength-property relationship, which is a relationship between the strength of the excess solidification material and the properties of the excess solidification material, in advance; The strength-property relationship setting step determines the strength-property relationship based on the strength after solidification for a plurality of combinations of the soil to be improved, the solidification material, and water, and The surplus solidification material strength estimation step estimates the strength of the surplus solidification material based on the strength-property relationship, A ground improvement method characterized in that the surplus solidification material is used as a filler material that requires a specified strength.

2. The ground improvement method of claim 1, The properties of the surplus solidification material are the density and calcium content of the surplus solidification material, and the ground improvement method is characterized in that the strength of the surplus solidification material is estimated based on the relationship between the density and calcium content of the surplus solidification material.

3. The ground improvement method according to any one of claims 1 to 2, Furthermore, the ground improvement method is characterized by having an adjustment step in which, depending on the strength of the surplus solidification material estimated in the surplus solidification material strength estimation step, if the estimated strength of the surplus solidification material is lower than a predetermined strength, the calcium content is increased by adding solidification material so that the strength becomes equal to or higher than the predetermined strength.

4. The ground improvement method according to any one of claims 1 to 3, The ground improvement method further comprises a backfilling step of filling the space between the existing structure and the new structure to be constructed within the existing structure with the surplus solidification material.

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