Survey boring method

Abstract

We provide a low-cost and accurate investigative boring method for detecting the presence of voids and air pockets in the ground. [Solution] A first hole 11 with a first diameter D1 is drilled into the ground 1 to be investigated, an injection material 2 is injected into the first hole 11 via a first bag 7, a second hole with a second diameter D2 that is concentric with the first hole 11 and larger than the first diameter D1 is drilled around the first hole 11, and the core drilled by the core boring is taken as the first sample S1.

Description

Technical Field

[0001] The present invention relates to an investigation boring method, and particularly to an investigation boring method for visualizing cavities and voids in the ground.

Background Art

[0002] The applicant of the present application proposed an investigation boring method described in Patent Document 1 as a method for accurately visualizing and investigating natural or artificial cavities and voids existing in the ground at low cost.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above conventional technique, when the cavities and voids in the ground are large, for example, the injection material may escape into the cavities around the boring, and the injection material may not spread along the axial direction of the boring. As a result, there is a problem that the presence of cavities and voids in the ground cannot be accurately visualized.

[0005] The problem to be solved by the present invention is to provide an investigation boring method that can accurately visualize and investigate the presence of cavities and voids in the ground even when they are large.

Means for Solving the Problems

[0006] The present invention drills a first hole with a first diameter in the ground to be investigated, inserts a long first bag body having an inner layer with water permeability and water retention and an outer layer with water permeability along the first hole, and injects an injection material that foams and cures at an adjusted time into the first bag body to cause foaming and curing. A core boring hole is drilled around the first hole, concentric with the first hole and having a second diameter larger than the first diameter. The above problem is solved by taking the core drilled by the core boring as the first sample. [Effects of the Invention]

[0007] According to the present invention, a first hole is drilled, a long first bag having a permeable and water-retentive inner layer and a permeable outer layer is inserted along the first hole, and an injection material that foams and hardens at a controlled time is injected into the first bag and allowed to foam and harden. After this, a second hole is drilled and a sample is taken. The first bag prevents the injection material from escaping into cavities and voids. As a result, even if the cavities and voids in the ground are large, their presence can be visualized and investigated accurately and at low cost. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view (part 1) showing one embodiment of the investigation boring method according to the present invention. [Figure 2] This is a cross-sectional view (part 2) showing one embodiment of the investigation boring method according to the present invention. [Figure 3] This is a cross-sectional view (part 3) showing one embodiment of the investigation boring method according to the present invention. [Figure 4] This is a cross-sectional view (part 4) showing one embodiment of the investigation boring method according to the present invention. [Figure 5] This is a cross-sectional view (part 5) showing one embodiment of the investigation boring method according to the present invention. [Figure 6] This is a cross-sectional view (part 6) showing one embodiment of the investigation boring method according to the present invention. [Figure 7] This is a cross-sectional view (part 7) showing one embodiment of the investigation boring method according to the present invention. [Figure 8] This is a cross-sectional view (part 8) showing one embodiment of the investigation boring method according to the present invention. [Figure 9]It is a cross-sectional view taken along the line IX-IX of FIG. 1. [Figure 10] It is a cross-sectional view taken along the line X-X of FIG. 5. [Figure 11] It is a cross-sectional view taken along the line XI-XI of FIG. 4. [Figure 12] It is a cross-sectional view taken along the line XII-XII of FIG. 6. [Figure 13] It is a cross-sectional view taken along the line XIII-XIII of FIG. 6. [Figure 14] It is a cross-sectional view taken along the line XIV-XIV of FIG. 8. [Figure 15] It is a cross-sectional view (Part 1) showing another embodiment of the investigation boring method according to the present invention. [Figure 16] It is a cross-sectional view (Part 2) showing another embodiment of the investigation boring method according to the present invention. [Figure 17] It is a cross-sectional view (Part 3) showing another embodiment of the investigation boring method according to the present invention. [Figure 18] It is a cross-sectional view (Part 4) showing another embodiment of the investigation boring method according to the present invention. [Figure 19] It is a cross-sectional view (Part 5) showing another embodiment of the investigation boring method according to the present invention. [Figure 20] It is a cross-sectional view (Part 6) showing another embodiment of the investigation boring method according to the present invention. [Figure 21] It is a cross-sectional view (Part 7) showing another embodiment of the investigation boring method according to the present invention. [Figure 22] It is a cross-sectional view (Part 8) showing another embodiment of the investigation boring method according to the present invention. [[ID=4]] [Figure 23] It is a cross-sectional view (Part 9) showing another embodiment of the investigation boring method according to the present invention. [Figure 24] It is a cross-sectional view (Part 10) showing another embodiment of the investigation boring method according to the present invention. [Figure 25] It is a cross-sectional view (Part 11) showing another embodiment of the investigation boring method according to the present invention. [Figure 26]This is a cross-sectional view (No. 12) showing another embodiment of the investigation boring method according to the present invention. [Figure 27] This is a front view showing the first bag used in the investigation boring method according to the present invention. [Figure 28] This is a cross-sectional view along the line XXVIII-XXVIII in Figure 27. [Figure 29] This is a longitudinal cross-sectional view showing the first bag and the first pipe used in the investigation boring method according to the present invention. [Figure 30] This is a cross-sectional view along the line XXX-XXX in Figure 29. [Figure 31] This is a longitudinal cross-sectional view showing how the injection material injected into the first pipe used in the investigation boring method according to the present invention spreads throughout the first bag. [Modes for carrying out the invention]

[0009] 《First Embodiment》 Hereinafter, examples of embodiments for carrying out the present invention will be described with reference to the drawings. Figures 1 to 8 are cross-sectional views showing one embodiment of the investigation boring method according to the present invention, Figure 9 is a cross-sectional view along the line IX-IX in Figure 1, Figure 10 is a cross-sectional view along the line XX in Figure 5, Figure 11 is a cross-sectional view along the line XI-XI in Figure 4, Figure 12 is a cross-sectional view along the line XII-XII in Figure 6, Figure 13 is a cross-sectional view along the line XIII-XIII in Figure 6, and Figure 14 is a cross-sectional view along the line XIV-XIV in Figure 8. Furthermore, Figure 27 is a front view showing the first bag used in the investigation boring method according to the present invention, Figure 28 is a cross-sectional view along the line XXVIII-XXVIII in Figure 27, Figure 29 is a longitudinal cross-sectional view showing the first bag and first pipe used in the investigation boring method according to the present invention, Figure 30 is a cross-sectional view along the line XXX-XXX in Figure 29, and Figure 31 is a longitudinal cross-sectional view showing how the injection material injected into the first pipe used in the investigation boring method according to the present invention spreads throughout the first bag.

[0010] As shown in Figures 1 and 2, the investigation boring method of this embodiment involves boring a first hole 11 with a first diameter D1 into the ground 1 to be investigated (hereinafter also referred to as the first step), and then, as shown in Figures 3 and 4, inserting a long first bag 7 having a permeable and water-retentive inner layer 73 and a permeable outer layer 74 so as to extend along the first hole 11, and injecting an injection material 2 that foams and hardens in a controlled time into the first bag 7 to foam and harden ( ) The following is also referred to as the second step.) Next, with the first bag 7, which has foamed and hardened from the injected material 2, remaining in the first hole 11, core boring is performed around the first hole 11 with a second diameter D2 that is concentric with the first hole 11 and larger than the first diameter D1, as shown in Figures 5 and 6 (hereinafter also referred to as the third step). Finally, as shown in Figures 7 and 8, core boring is performed and the core containing the first bag 7 is collected as the first sample S1 (hereinafter also referred to as the fourth step). Then, by visually observing the first sample S1 containing the first bag 7 collected in this manner, it is examined whether or not there are cavities or voids in the ground that is the subject of the investigation. Each step will be described in detail below.

[0011] In the first step shown in Figures 1 and 2, a first borehole 11 with a first diameter D1 is drilled into the ground 1 that is the subject of the investigation. Although not particularly limited, a first double core tube 3 with an outer diameter φ of 46 mm is attached to a boring machine (not shown), and using this boring machine, a first borehole 11 is drilled with a bore diameter (=first diameter D1) of 46 mm and a first drilling depth DP1 of 1 m, as shown in Figures 1 and 2. Figure 3 shows the state after the first borehole 11 has been drilled into the ground 1. In Figures 1 to 7, the symbol L indicates a geological layer (void layer) in which a cavity or void exists. The drilling depth is not particularly limited, and drilling may be done to any desired depth, however, if the groundwater level of the ground is high and the borehole wall is not self-supporting, it is preferable to shorten the drilling depth.

[0012] The first double core tube 3 used for drilling the first hole 11, as shown in the cross-sectional view of Figure 9, has a cylindrical inner core tube 31 and a cylindrical outer core tube 32. Drilling fluid (water, etc., in this embodiment) circulates between the inner core tube 31 and the outer core tube 32, and a drilling bit is provided at its tip, making it a boring tool.

[0013] In the second step shown in Figures 3 and 4, a long first bag 7, which has a permeable and water-retentive inner layer 73 and a permeable outer layer 74, is inserted into the first hole 11 drilled in the first step described above, so as to extend along the first hole 11, and an injection material 2 that foams and hardens in a controlled time is injected into the first bag 7. Figure 27 is a front view showing the first bag 7 used in the investigation boring method according to the present invention, and Figure 28 is a cross-sectional view along the line XXVIII-XXVIII in Figure 27.

[0014] As shown in Figure 27, the first bag 7 of this embodiment is a long, flexible bag-shaped member extending from an upper end 71 to a lower end 72, and is formed in a bottomed cylindrical shape with an open upper end 71 and a closed lower end 72. The first bag 7 of this embodiment is formed with an outer diameter smaller than the inner diameter of the first hole 11. As shown in Figure 28, the first bag 7 of this embodiment is constructed by laminating an inner layer 73 and an outer layer 74 together. The inner layer 73 of the first bag 7 of this embodiment is made of a material that has water retention properties that can retain water in the injection material 2 and water permeability that allows the injection material 2 to pass through, and is not particularly limited, but for example, absorbent cotton can be used. The outer layer 74 of the first bag 7 of this embodiment is made of a material that has water permeability that allows the injection material 2 to pass through, and is not particularly limited, but for example, gauze can be used.

[0015] When the injection material 2 is injected into the long first bag 7 having the inner layer 73 and outer layer 74 from the opening at the upper end 71, the injection material 2 injected into the inside of the first bag 7 does not directly permeate through the inner layer 73 and outer layer 74 to the outside from the lower end of the first bag 7, but is temporarily retained by the water-retentive inner layer 73 before permeating through the inner layer 73 and outer layer 74. While the injection material 2 is retained by the inner layer 73, the liquid level of the injection material 2 rises from the lower end 72 to the upper end 71 of the first bag 7, and spreads throughout the entire first bag 7.

[0016] The first bag 7 may be inserted into the first hole 11 shown in Figure 3 in the state shown in Figure 27, and the injection material may be injected from the opening at the upper end 71. Alternatively, the first bag 7 may be attached to the first pipe 9, which serves as a guide rod, and the first pipe 9 may be inserted into the first hole 11, and the injection material 2 may be injected from the opening at the upper end 71 of the first bag 7. By inserting the first bag 7 into the first hole 11 with the first pipe 9 attached, the position and shape of the first bag 7 relative to the first hole 11 can be stabilized, and the ease of insertion into the first hole 11 can be improved. Figure 29 is a longitudinal cross-sectional view showing the first bag 7 and the first pipe 9 used in the investigation boring method according to the present invention, and Figure 30 is a cross-sectional view along the line XXX-XXX in Figure 29.

[0017] As shown in Figures 29 and 30, the first pipe 9 in this embodiment is a pipe having a length corresponding to the depth of the first hole 11, and is not particularly limited, but for example, a heat-resistant polyvinyl chloride pipe can be used. The lower end of the mixer 92 is attached to the upper end of the first pipe 9 in this embodiment via a detachable socket joint 91, and the upper end of the mixer 92 is connected to a first liquid supply device 21A and a second liquid supply device 21B of the injection material. After completing the second step shown in Figures 3 and 4, the first pipe 9 in this embodiment is separated from the mixer 92 at the socket joint 91 and remains in the first hole 11 together with the first bag 7, as shown in Figures 5 and 6.

[0018] The mixer 92 in this embodiment is a stationary mixer equipped with spiral blades inside. When the first liquid from the first liquid supply unit 21A and the second liquid from the second liquid supply unit 21B flow into the upper part of the mixer 92, these first and second liquids flow downward along the spiral blades. This allows the first and second liquids of the two-component curing type injection material 2 to be thoroughly mixed, enabling good foaming and curing. Alternatively, a water packer made of heat-resistant rubber (a water balloon-shaped member) may be provided on the outer surface of the mixer 92 in this embodiment to suppress the rise of the foamed injection material 2 around the first pipe 9.

[0019] In this embodiment, the first tube 9 has a first through-hole 93 formed near its upper end. In this embodiment, there are four first through-holes 93 formed in the circumferential direction of the first tube 9, although this is not particularly limited. The position of the first through-holes 93 formed in the first tube 9 is not particularly limited, and they may be formed near the central part or the lower end of the first tube 9. However, by forming the first through-holes 93 near the upper end of the first tube 9, the injection material 2 can be injected from the upper end of the space partitioned by the inner surface of the first bag 7 and the outer surface of the first tube 9, thereby widening the filling range in the vertical direction. Furthermore, by forming the first through-holes 93 near the upper end of the first tube 9, the length of the flow path until the injection material 2 foams is increased, improving the agitation between the first liquid and the second liquid.

[0020] In this embodiment, the first bag 7 is provided so as to surround the outer surface of the first tube 9, with the upper end 71 of the first bag 7 liquid-tightly fixed to the upper end of the first tube 9, and the lower end 72 of the first bag 7 liquid-tightly fixed to the lower end of the first tube 9. Figures 31(A) to (E) are longitudinal cross-sectional views showing how the injection material injected from the upper end of the first tube 9 spreads along the vertical direction of the first bag 7.

[0021] First, as shown in Figure 31(A), the injection material 2 injected from the upper end of the first pipe 9 via the mixer 92 begins to fill from the lower end of the first pipe 9. Subsequently, as shown in Figure 31(B), when the liquid level of the injection material 2 reaches the first through-holes 93, the injection material 2 flows through these four first through-holes 93 into the space partitioned by the outer surface of the first pipe 9 and the inner surface of the first bag 7, from its upper end 71 to its lower end 72.

[0022] As shown in Figure 31(C), the injection material 2, which flows into the space partitioned by the outer surface of the first pipe 9 and the inner surface of the first bag 7 from its upper end 71, begins to fill this space from its lower end 72. At this time, since the inner surface of the first bag 7 in this embodiment is composed of a water-retentive inner layer 73, the injection material 2 is temporarily retained in the inner layer 73 before it permeates through the inner layer 73 and the outer layer 74. As a result, as shown in Figure 31(D), the liquid level of the injection material 2 rises while retaining water in the inner layer 73, filling the first bag 7 from its lower end 72 to its upper end 71, and the injection material 2 spreads throughout the entire first bag 7. Then, as shown in Figure 31(E), the injection material 2, which has spread throughout the entire vertical direction of the first bag 7, foams and hardens in the first hole 11 while permeating through the inner layer 73 and the outer layer 74.

[0023] The injection material 2 used in this embodiment can be exemplified by a two-component curing foamed urethane resin, but is not particularly limited and any material that foams and hardens in a controlled time is acceptable. Since the injection material 2 is injected into the ground 1 that is the subject of the investigation, it is preferable that the injection material 2 does not contain harmful substances. Furthermore, since there is a third step after the injection of the injection material 2, it is preferable that the material has a flexible curing time. In addition, since the sample taken in the investigation is from a very limited area (for example, about φ86 mm of the second diameter described later), it is preferable that the injection material 2 has a viscosity that does not penetrate too deeply into the ground 1.

[0024] As shown in Figure 3, the injection material 2, such as the two-component curing foamed urethane resin, is supplied to the mixer 92 using a supply machine 21A that supplies the first liquid of the injection material 2 and a supply machine 21B that supplies the second liquid of the injection material 2. When the first and second liquids of the injection material 2 are supplied to the mixer 92 at a predetermined pumping pressure, both liquids are agitated as they pass through the mixer 92, and the curing reaction begins.

[0025] As shown in Figure 31(D), the injection material 2, which has spread throughout the first bag 7, foams and hardens in the first hole 11 while permeating the inner layer 73 and outer layer 74, as shown in Figure 31(E). Figures 4 and 11 show the state in which the injection material 2 has filled the first hole 11 via the first tube 9 and the first bag 7. As shown in Figure 4, once the injection material 2 has filled the first hole 11 via the first tube 9 and the first bag 7, it is left to wait until the injection material 2 hardens and develops sufficient strength. Once the injection material 2 has hardened, the first tube 9 and the mixer 92 are separated at the socket joint 91, and as shown in Figures 5 and 6, the first bag 7 and the first tube 9, in which the injection material 2 has foamed and hardened, are left in the first hole 11, and the mixer 92 is withdrawn from the first hole 11.

[0026] In the third step shown in Figures 5 and 6, the first bag 7 and the first tube 9, which have foamed and hardened from the injected material 2, remain in the first hole 11, and a core boring is performed around the first hole 11 with a second diameter D2 that is concentric with the first hole 11 and larger than the first diameter D1. Although not particularly limited, a second double core tube 4 with an outer diameter φ of 86 mm is mounted on a boring machine (not shown), and using this boring machine, a second hole 12 is drilled, for example, with a drilling diameter (= second diameter D2) of 86 mm and a first drilling depth DP1 of 1 m, as shown in Figures 5 and 6. Figure 7 shows the second hole 12 after the core, which will be used as the first sample S1, has been taken.

[0027] The second double core tube 4 used for drilling the second hole 12, as shown in the cross-sectional view of Figure 10, has a cylindrical inner core tube 41 and a cylindrical outer core tube 42. Drilling fluid (water, etc., in this embodiment) circulates between the inner core tube 41 and the outer core tube 42, and a drilling bit is provided at the tip of the boring tool. The core that will become the first sample S1 is held in the inner core tube 41.

[0028] Figure 12 shows a cross-section along the line XII-XII in Figure 6, and Figure 13 shows a cross-section along the line XIII-XIII in Figure 6. At the borehole depth where the cavity layer L shown in Figure 12 does not exist, the same geological layer as the ground 1 exists between the central injection material 2 and the outer second double core tube 4. In contrast, at the borehole depth where the cavity layer L exists, as shown in Figure 13, a geological layer 2a into which the injection material 2 has penetrated exists between the central injection material 2 and the outer second double core tube 4.

[0029] In the fourth step, shown in Figures 7 and 8, the second double core tube 4 is lifted, and the core held by the inner core tube 41 is collected as the first sample S1. Figure 8 shows a cross-section of the collected first sample S1, and Figure 7 shows the second hole 12 after the first sample S1 has been collected. The collected first sample S1 is a cylindrical mass with a diameter equal to the inner diameter of the inner core tube 41 and a length equal to the first drilling depth DP1. It is used to investigate whether or not there are cavities or voids in the ground under investigation, and is observed visually.

[0030] Figure 14 is a cross-sectional view along the line XIV-XIV, which is part of the first sample S1. At the drilling depth where the cavity layer L shown in the figure exists, the outer layer of the first sample S1 contains a geological layer 2a into which the injection material 2 has penetrated via the first pipe 9 and the first bag 7. Therefore, by simply visually observing the collected first sample S1, it is easy to confirm which first drilling depth DP1 contains the cavity layer L. Such visual observation does not require the skills of experienced drillers. Furthermore, by combining this with indirect investigations such as electromagnetic wave exploration, electrical exploration, or ground-penetrating radar exploration, investigations can be conducted quickly, at low cost, and with high accuracy.

[0031] In addition, even if the cavity layer L extends to the first borehole depth DP1, the injection material 2 injected through the first pipe 9 and the first bag 7 spreads sufficiently along the vertical direction, allowing it to penetrate the cavity layer L. Furthermore, even if the cavity layer L extends horizontally for a long distance, injecting it through the first bag 7 prevents the injection material 2 from concentrating solely on the cavity layer L, thus enabling accurate detection of cavity layers L in other parts of the vertical direction.

[0032] 《Second Embodiment》 The first embodiment described above is an example in which a first sample S1 is taken at a first drilling depth DP1. Subsequently, a second sample S2 from a deeper layer than the first drilling depth DP1 can be taken using a second borehole 12. Figures 15 to 26 are cross-sectional views showing other embodiments of the investigation boring method according to the present invention.

[0033] In the investigation boring method of this embodiment, a second sample S2 from a first drilling depth DP1 to a second drilling depth DP2 is collected by performing the same first to fourth steps as in the first embodiment described above. At this time, if a means for supporting the boring tool is provided in the second hole 12 as shown in Figure 7, drilling can be performed with even greater accuracy. Therefore, in this embodiment, as shown in Figures 15 and 16, a cylindrical casing 5 with a diameter corresponding to the diameter of the second hole 12 is inserted and installed in the second hole 12 from which the first sample S1 was taken (fifth step). Then, as shown in Figures 17 and 18, a center riser 6 for guiding the boring rod is inserted and installed in the cylindrical casing 5 (sixth step). Then, as shown in Figures 19 and 20, a third hole 13 with a first diameter D1 is drilled in the bottom surface of the second hole 12 using a boring rod guided by the center riser 6 (seventh step).

[0034] Next, as shown in Figures 21 and 22, a long second bag 8 having a permeable and water-retentive inner layer 73 and a permeable outer layer 74 is inserted along the second hole 12, and an injection material 2 that foams and hardens in a controlled time is injected into the second bag 8 to foam and harden (step 8). Then, with the second bag 8, in which the injection material 2 has foamed and hardened, remaining in the second hole 12, as shown in Figures 23 and 24, a core boring is performed around the third hole 13 with a second diameter D2 that is concentric with the third hole 13 and larger than the first diameter D1 (step 9). Finally, as shown in Figures 25 and 26, a core boring is performed and the core containing the second bag 8 is taken as the second sample S2 (step 10). Each step will be described in detail below.

[0035] First, in the fifth step shown in Figures 15 and 16, in order to reinforce the second hole 12 drilled in the third step shown in Figures 5 and 6, a cylindrical casing 5 with a diameter corresponding to the second diameter D2 of the second hole 12 is inserted into the second hole 12. Although not particularly limited, if the second diameter D2 is φ86 mm, a steel cylindrical casing 5 with an inner diameter of φ90.2 mm, an outer diameter of φ101.6 mm, and a plate thickness t of 5.7 mm can be used. As shown in Figure 16, by inserting a cylindrical casing 5 with a diameter slightly larger than the second diameter D2 of the second hole 12, the hole wall of the second hole 12 is firmly reinforced.

[0036] In the sixth step shown in Figures 17 and 18, a center riser 6, which guides a boring rod such as the first double core tube 3, is inserted and installed into the cylindrical casing 5. The center riser 6 in this embodiment is used to center the first double core tube 3 when drilling the third hole 13 with the first double core tube 3. For this reason, the center riser has an inner diameter corresponding to the outer diameter of the first double core tube 3, and as shown in Figure 17, protrusions 61 that discretely contact the inner surface of the cylindrical casing 5 are provided at equal intervals in the circumferential direction. As shown in Figure 18, when the center riser 6 is inserted into the cylindrical casing 5, its protrusions 61 contact the inner surface of the cylindrical casing 5, so that the center riser 6 is positioned concentrically with the cylindrical casing 5.

[0037] In the seventh step shown in Figures 19 and 20, a first hole 11 with a first diameter D1 is drilled into the bottom surface of the second hole 12, similar to the first step described above. Although not particularly limited, a first double core tube 3 with an outer diameter φ of 46 mm is mounted on a boring machine (not shown), and guided by a center riser 6, a third hole 13 is drilled using the boring machine, for example, with a drilling diameter (=first diameter D1) of 46 mm and a second drilling depth DP2 of 1 m. Figure 20 shows the state in which the third hole 13 has been drilled below the second hole 12 in the ground 1.

[0038] In the eighth step shown in Figures 21 and 22, a long second bag 8, which has a water-permeable and water-retentive inner layer 73 and a water-permeable outer layer 74, is inserted into the third hole 13 drilled in the seventh step described above, so as to extend along the second hole 12, and an injection material 2 that foams and hardens in a controlled time is injected into the second bag 8. The second bag 8 in this embodiment has the same configuration as the first bag 7 of the first embodiment shown in Figures 27 and 28, and the second tube 10, which serves as a guide rod for the second bag 8, has the same configuration as the first tube 9 of the first embodiment shown in Figures 29 and 30, so the descriptions of the first bag 7 and the first tube 9 are used here. Therefore, the second bag 8, although not shown, has an upper end 81 and a lower end 82, and an inner layer 83 and an outer layer 84, similar to the first bag 7 shown in Figures 27 and 28. Furthermore, although not shown in the illustration, the second pipe body 10 has a socket joint 101, a mixer 102, and a second through hole 103, similar to the first pipe body 9 shown in Figures 29 and 30.

[0039] Furthermore, the injection material 2 used here is the same as the injection material 2 used in the first embodiment described above. Figure 22 shows the state in which the injection material 2 has been filled into the third hole 13 via the second tube 10 and the second bag 8. As shown in Figure 22, once the injection material 2 has been filled into the third hole 13, the system is left waiting until the injection material 2 hardens and develops sufficient strength. Once the injection material 2 has hardened, the second tube 10 and the mixer 102 are separated at the socket joint 101, and as shown in Figures 23 and 24, the second bag 8 and the second tube 10, in which the injection material 2 has foamed and hardened, are left in the second hole 12, and the mixer 102 is withdrawn from the second hole 12.

[0040] In the ninth step shown in Figures 23 and 24, with the second bag 8 and second tube 10, which have foamed and hardened from the injected material 2, remaining in the second hole 12, a core boring hole is drilled around the third hole 13 concentrically with the third hole 13 and with a second diameter D2 that is larger than the first diameter D1. Although not particularly limited, after removing the center riser 6, the second double core tube 4 with an outer diameter φ of 86 mm is mounted on a boring machine (not shown), and using this boring machine, a fourth hole 14 is drilled, for example, with a drilling diameter (= second diameter D2) of 86 mm and a second drilling depth DP2 of 1 m, as shown in Figures 23 and 24. Figure 25 shows the fourth hole 14 after the core for the second sample S2 has been taken.

[0041] In the tenth step, shown in the final Figures 25 and 26, the second double core tube 4 is lifted, and the core held by the inner core tube 41 is collected as the second sample S2. Figure 26 shows a cross-section of the collected second sample S2, and Figure 25 shows the fourth hole 14 after the second sample S2 has been collected. The collected second sample S2 is a cylindrical mass with a diameter equal to the inner diameter of the inner core tube 41 and a length equal to the second drilling depth DP2. It is used to investigate whether or not cavities or voids exist in the ground under investigation, and is observed visually.

[0042] Furthermore, if a sample is to be taken from a portion deeper than the bottom surface of the fourth hole 14 shown in Figure 25, the above steps 5 through 10 should be repeated. [Explanation of symbols]

[0043] 1...Ground 11...1st hole 12…Second hole 13…3rd hole 14...4th hole 2…Injection material 21A,21B…Feeding machine 2a...Stratum into which the injection material has penetrated 3…First double core tube 31…Inner core tube 32…Outer core tube 4…Second double core tube 41…Inner core tube 42…Outer core tube 5. Cylindrical casing 6... Center riser 61…Convex part 7...First bag body 71...Top end 72...Lower end 73...Inner layer 74...outer layer 8…Second bag body 81...Top end 82…Lower end 83...Inner layer 84…outer layer 9…First pipe 91...Socket joint 92... Mixer 93…1st through hole 10…Second pipe 101...Socket joint 102... Mixer 103…Second through hole S1...First sample S2…2nd sample D1…1st caliber D2…Second caliber DP1…1st drilling depth DP2…Second drilling depth L…Cavity layer

Claims

1. A first borehole of the first diameter is drilled into the ground targeted for investigation. A long first bag, comprising an inner layer having water permeability and water retention properties and an outer layer having water permeability, is inserted so as to extend along the first hole. An injection material that foams and hardens at a controlled time is injected into the previous first bag and allowed to foam and harden. A core boring hole is drilled around the first hole, concentric with the first hole and with a second diameter larger than the first diameter. A survey boring method in which the core drilled by the aforementioned core boring is taken as a first sample.

2. A cylindrical casing with a diameter corresponding to the diameter of the second hole is inserted into the second hole from which the core was removed and installed. A center riser for guiding the boring rod is inserted into the aforementioned cylindrical casing and installed. Using the boring rod guided by the center riser, a third hole of the first diameter is drilled into the bottom surface of the second hole. A long second bag, comprising a water-permeable and water-retentive inner layer and a water-permeable outer layer, is inserted so as to extend along the third hole, and the injection material is injected into the second bag and allowed to foam and harden. A core boring hole is drilled around the third hole, concentric with the third hole and having a second diameter larger than the first diameter. The investigation boring method according to claim 1, wherein the core drilled by the core boring method is taken as a second sample.

3. The first bag is provided so as to surround the outer surface of a long first tube having a first through hole, The upper end of the first bag is liquid-tightly fixed to the upper end of the first tube, and the lower end of the first bag is liquid-tightly fixed to the lower end of the first tube. The investigation boring method according to claim 1 or 2, wherein the injection material is injected from the upper end of the first pipe, passes through the first through hole of the first pipe, and is injected into the first bag.

4. The second bag is provided so as to surround the outer surface of the elongated second tube having a second through hole, The upper end of the second bag is liquid-tightly fixed to the upper end of the second tube, and the lower end of the second bag is liquid-tightly fixed to the lower end of the second tube. The investigation boring method according to claim 2, wherein the injection material is injected from the upper end of the second pipe, passes through the second through hole of the second pipe, and is injected into the second bag.

5. The investigation boring method according to claim 3, wherein the first through hole is provided in close proximity to the upper end of the first pipe body.

6. The investigation boring method according to claim 4, wherein the second through hole is provided in close proximity to the upper end of the second pipe body.

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