Monitoring apparatus and monitoring method

Abstract

To easily confirm the state of a soil improvement body constructed by a high-pressure injection agitation method in real time.SOLUTION: A monitoring device, comprising a boring machine (21) for driving a drill pipe (22) to drill a hole in the ground, and a detection structure (30,40), wherein the detection structure (30,40) comprises an optical fiber (31,41), a detection portion (32,42) provided at one end of the optical fiber (31,41), a light source, and a light receiving portion, and light of the light source passes through the optical fiber (31,41) and is emitted from the detection portion (32,42) as inspection light; Reflection light of the inspection light is received by the detection part (3242), and is received by the light receiving part through the optical fibers (3141), and the detection part (3242) is arranged in a sensor hole (26a, 26b) arranged on the outer periphery of the boring rod (22), and is exposed to the soil improvement body from the sensor hole (26a, 26b).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a monitoring device and a monitoring method used when constructing a ground improvement body using a high-pressure jet mixing method.

[0002] The high-pressure injection mixing method is known as a construction method for improving soft ground to high strength. In this method, a hardening material is injected at high pressure from the nozzle of an injection pipe inserted into the ground while the injection pipe is rotated and pulled up, creating a cylindrical or fan-shaped ground improvement body in the ground.

[0003] In the high-pressure jet mixing method, the condition of the ground improvement body, such as its effective diameter, can vary depending on the shear strength and hardness of the soil layer to be improved, as well as the unevenness of the target soil layer. For this reason, it is necessary to confirm that the ground improvement body has been constructed as planned. Traditionally, after the ground improvement body has been constructed, follow-up survey borings have been conducted and the results confirmed using the cores extracted. However, with this method, the constructed ground improvement body must be allowed to cure for several days before the cores can be extracted, making it impossible to check the condition of the ground improvement body during or immediately after construction, which means it takes time to confirm the condition of the ground improvement body.

[0004] On the other hand, as an alternative to the core sampling method, there is a method for monitoring the condition of the ground improvement body in real time based on sound, heat, etc. For example, Patent Document 1 monitors the condition of the ground improvement body based on sound. In the device and method disclosed in Patent Document 1, a piercing pipe is provided around the injection pipe, and a sound collector is placed inside the piercing pipe. This sound collector monitors the sound of the hardening material sprayed from the nozzle of the injection pipe hitting the piercing pipe. Whether the hardening material has reached the piercing pipe is determined based on the volume level of the monitored sound. In other words, the device and method disclosed in Patent Document 1 make it possible to grasp in real time the condition of the ground excavated around the piercing pipe when the hardening material is sprayed from the nozzle of the injection pipe, thereby enabling the condition of the ground improvement body to be confirmed in a short period of time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-62626 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the device and method disclosed in Patent Document 1 have a problem in that it takes time and effort to install monitoring equipment such as built-in pipes and sound collectors.

[0007] In view of these points, the present invention aims to provide a monitoring device and a monitoring method that can easily check the condition of a ground improvement body constructed using a high-pressure injection mixing method in real time. [Means for solving the problem]

[0008] The monitoring device is a monitoring device used when creating a ground improvement body in a high-pressure injection mixing method in which a ground improvement body is created by injecting hardening material from the nozzle of an injection pipe inserted into the ground while rotating and lifting the injection pipe, and comprises a cylindrical boring rod, a boring machine that drives the boring rod to drill holes in the ground, and a detection structure that detects the condition of the ground improvement body, the detection structure comprising an optical fiber, a detection unit provided at one end of the optical fiber, a light source, and a light receiving unit, the light from the light source passes through the optical fiber and is emitted from the detection unit as inspection light, the reflected light of the inspection light is received by the detection unit and passes through the optical fiber to be received by the light receiving unit, the detection unit is placed in a sensor hole provided on the outer periphery of the boring rod and is exposed to the ground improvement body from the sensor hole.

[0009] The monitoring method is a monitoring method used when creating a ground improvement body in a high-pressure injection mixing method in which a hardening material is sprayed from the nozzle of an injection pipe inserted into the ground while the injection pipe is rotated and pulled up to create the ground improvement body, and the method involves driving a boring rod with a boring machine to drill a hole in the ground, detecting the condition of the ground improvement body using a detection structure comprising an optical fiber, a detection unit provided at one end of the optical fiber, a light source, and a light receiving unit, the light from the light source passing through the optical fiber and emitted from the detection unit as inspection light, the reflected light of the inspection light being received by the detection unit and also passing through the optical fiber to be received by the light receiving unit, and the reflected light being received by the detection unit exposed to the ground improvement body from a sensor hole provided on the outer periphery of the boring rod. [Effects of the Invention]

[0010] According to the present invention, a monitoring device and a monitoring method can be provided that can easily check the condition of a ground improvement body constructed using a high-pressure jet mixing method in real time. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing a schematic diagram of a high-pressure injection stirring device and a monitoring device according to the present embodiment. FIG. [Figure 2] FIG. 2 is an exploded perspective view showing a boring rod and a swivel. [Figure 3A] FIG. 1 shows a first detection structure. [Figure 3B] FIG. 10 shows a second detection structure. [Figure 4] This is a graph showing the light intensity detected by a monitoring device during the construction of a ground improvement body using a high-pressure jet mixing device. [Figure 5] 10 is a graph showing changes in light intensity of a curing agent during the curing process. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a monitoring device and a monitoring method using this monitoring device according to the present invention will be described with reference to the drawings.

[0013] FIG. 1 is a diagram schematically illustrating a high-pressure injection stirring device 10 and a monitoring device 20 of this embodiment. The high-pressure injection mixing device 10 comprises a construction machine 11, an injection pipe 12 supported vertically on the ground G by the construction machine 11, a hose 13 connected to the injection pipe 12, and a plant (not shown) connected to the hose 13 for supplying the hardening material.

[0014] The construction machine 11 has the function of moving the injection pipe 12 in the vertical direction, and the function of rotating the injection pipe 12 around its central axis or swinging it around its central axis within a predetermined rotation angle.

[0015] The injection pipe 12 has a single-pipe structure or a multiple-pipe structure, and a flow path for flowing the hardening material is formed inside the injection pipe 12. A nozzle 12a that leads to this flow path is provided on the side of the lower part of the injection pipe 12. A hose 13 is attached to the upper part of the injection pipe 12, and the hose 13 is connected to the plant that delivers the hardening material at a predetermined pressure. The hardening material is, for example, a cement-based hardening material, such as cement milk, which is a mixture of water and cement.

[0016] By operating the construction machine 11 and plant described above, the injection pipe 12 is raised while rotating, and the hardening material delivered from the plant flows through the inside of the hose 13 and injection pipe 12 and is injected at high pressure from the nozzle 12a into the ground G. That is, the ground G is cut and collapsed by the hardening material injected at high pressure, and is further stirred and mixed with the hardening material, so that a cylindrical or fan-shaped ground improvement body B can be created in the ground G. Furthermore, the high-pressure jet stirring device 10 is equipped with a nozzle position detection unit (not shown) that detects the depth position of the nozzle 12a in the ground G. Note that the monitoring device 20 may also be equipped with the nozzle position detection unit.

[0017] The monitoring device 20 comprises a boring machine 21 installed on the ground G, a cylindrical boring rod 22, and a first detection structure 30 and a second detection structure 40 (see Figure 2) for detecting the condition of the ground improvement body B. The boring machine 21 rotates and moves the boring rod 22 up and down to bore a hole in the ground G.

[0018] A swivel 24 is connected to the upper end of the boring rod 22. When the boring rod 22 is rotationally driven by the boring machine 21, the boring rod 22 rotates relative to the stationary swivel 24. A water supply hose (not shown) is connected to the swivel 24. When the boring machine 21 is drilling a hole, water supplied from the water supply hose can be supplied into the boring rod 22 via the swivel 24.

[0019] The axis of rotation 22 a of the boring rod 22 is parallel to the central axis of the injection pipe 12 . The boring machine 21 is positioned so that the boring rod 22 overlaps the ground improvement body B from above. In other words, the boring rod 22 is positioned inside the effective diameter D (construction diameter) of the ground improvement body B in a plan view. Therefore, when the boring rod 22 has drilled to the depth of the ground improvement body B, the lower end of the boring rod 22 is exposed to the ground improvement body B.

[0020] FIG. 2 is an exploded perspective view showing the boring rod 22 and the swivel 24. The boring rod 22 comprises a cylindrical boring rod body 25, a cylindrical sensor section 26 connected to the lower end of the boring rod body 25, a bit 27 connected to the lower end of the sensor section 26, and a cylindrical upper sensor section 28 connected to the upper end of the boring rod body 25.

[0021] The length of the boring rod 22 can be increased by adding multiple boring rod bodies 25 in the vertical direction. In detail, the length of the boring rod 22 is extended by connecting the lower end of an extension boring rod body 25 (not shown) to the upper end of the boring rod body 25 in Fig. 2 by screwing it, and then screwing the lower end of the upper sensor part 28 to the upper end of this extension boring rod body 25. The upper end of the upper sensor part 28 is connected to the lower end of the swivel 24. When the boring rod 22 is driven to rotate, the upper sensor part 28 rotates relative to the swivel 24. The upper sensor section 28 has a fiber-through hole 28a formed on its outer periphery, which passes through the outer periphery in the radial direction.

[0022] The sensor unit 26 is detachably connected to the boring rod body 25 by screwing the upper end of the sensor unit 26 into the lower end of the boring rod body 25. The length of the sensor unit 26 is shorter than the length of the boring rod body 25. A plurality of sensor holes 26a, 26b that penetrate the outer periphery in the radial direction are provided on the outer periphery of the sensor unit 26. The sensor holes 26a and the sensor holes 26b are provided at positions spaced apart from each other in the circumferential direction of the sensor unit 26. The bit 27 is detachably connected to the sensor unit 26 by screwing the upper end of the bit 27 into the lower end of the sensor unit 26. A cutting part 27a for cutting the ground G is provided on the lower surface of the bit 27.

[0023] FIG. 3A shows a first detection structure 30. As shown in FIG. The first detection structure 30 includes an optical fiber 31, a detection unit 32 provided at one axial end 31a of the optical fiber 31, a light source 33, and a light receiving unit . The detection section 32 is arranged in the sensor hole 26a of the sensor section 26 of the boring rod 22, and can be exposed from the sensor hole 26a toward the ground improvement body B.

[0024] Light from the light source 33 passes through the optical fiber 31 and is emitted as inspection light from the detection unit 32 to the ground improvement body B to be inspected, and the reflected light of the inspection light is received by the detection unit 32 and passes through the optical fiber 31 and is received by the light receiving unit 34.

[0025] The optical fiber 31 includes an incident fiber section 35 that connects the light source 33 and the detection section 32, and a light receiving fiber section 36 that connects the detection section 32 and the light receiving section . At one end 31a of the optical fiber 31, the axis 35a of one end of the incident fiber section 35 and the axis 36a of one end of the receiving fiber section 36 are parallel, and the optical fiber 31 is formed so that the axial end face of the incident fiber section 35 and the axial end face of the receiving fiber section 36 are aligned.

[0026] The detection unit 32 is formed by attaching a cap 37 to one end 31a of the optical fiber 31. The cap 37 is made of a light-transmitting material. The cap 37 includes a cylindrical fitting portion 37a that fits onto the outer periphery of the one end portion 31a, and a cover portion 37b that covers the axial end face of the one end portion 31a.

[0027] The axial end face of the cover portion 37b is exposed to the soil improvement body B and has a tip face 38 that covers the one end 31a of the optical fiber 31 in the axial direction. Specifically, the tip surface 38 has an incident side inclined surface 38a inclined relative to the axis 35a of the incident fiber portion 35 and a light receiving side inclined surface 38b inclined relative to the axis 36a of one end of the light receiving fiber portion 36. The tip surface 38 is formed into a triangular shape tapering toward the tip side like the tip of a double-edged blade, by an incident-side inclined surface 38a and a light-receiving-side inclined surface 38b facing the incident-side inclined surface 38a.

[0028] The detection unit 32 is attached to the sensor hole 26a by fitting the outer periphery of the fitting portion 37a of the cap 37 into the sensor hole 26a.

[0029] Referring to Figure 3A, when light from the light source 33 enters the incident fiber section 35, the light is emitted as inspection light from the incident side inclined surface 38a of the detection section 32 and is reflected from the incident side inclined surface 38a.This reflected light is reflected from the light-receiving side inclined surface 38b and enters one end of the light-receiving fiber section 36, and is received by the light-receiving section 34. Here, the reflectance of the reflected light reflected by the incident-side inclined surface 38a and the light-receiving-side inclined surface 38b varies depending on the material present around the tip surface 38 based on the nature of light refraction. In detail, for example, when a hardening material such as cement milk containing water is present around the tip surface 38, the reflectance of the reflected light is significantly reduced compared to when air is present around the tip surface 38, and the intensity of the light received by the light receiving unit 34 is reduced. By detecting such changes in the light intensity, the condition of the ground improvement body B can be detected.

[0030] Furthermore, since the refractive index of the cap 37 that constitutes the detection unit 32 is known, the refractive index of the soil improvement body B can be obtained based on the intensity of light detected by the light receiving unit .

[0031] FIG. 3B shows a second detection structure 40. As shown in FIG. The second detection structure 40 includes an optical fiber 41, a detection unit 42 provided at one axial end 41a of the optical fiber 41, a light source 43, and a light receiving unit 44. The detection section 42 is arranged in the sensor hole 26b of the sensor section 26 of the boring rod 22, and can be exposed toward the ground improvement body B from the sensor hole 26b.

[0032] Light from the light source 43 passes through the optical fiber 41 and is emitted as inspection light from the detection unit 42 to the ground improvement body B to be inspected, and the reflected light of the inspection light is received by the detection unit 42 and passes through the optical fiber 41 and is received by the light receiving unit 44.

[0033] The optical fiber 41 includes an incident fiber portion 45 that connects the light source 43 and the detection portion 42 , and a light receiving fiber portion 46 that connects the detection portion 42 and the light receiving portion 44 . At one end 41a of the optical fiber 41, the axis 45a of one end of the incident fiber section 45 and the axis 46a of one end of the receiving fiber section 46 are parallel, and the optical fiber 41 is formed so that the axial end face of the incident fiber section 45 and the axial end face of the receiving fiber section 46 are aligned.

[0034] The detection unit 42 is formed by attaching a cap 47 to one end 41a of the optical fiber 41. The cap 47 is made of a light-transmitting material. The cap 47 includes a cylindrical fitting portion 47a that fits onto the outer periphery of the one end portion 41a, and a cover portion 47b that covers the axial end face of the one end portion 41a.

[0035] The axial end face of the cover portion 47b is exposed to the soil improvement body B and has a tip face 48 that covers the one end 41a of the optical fiber 41 in the axial direction. More specifically, the tip surface 38 is a plane perpendicular to the axis 45 a of one end of the incident fiber portion 45 and the axis 46 a of one end of the receiving fiber portion 46 .

[0036] The detection unit 42 is attached to the sensor hole 26b by fitting the outer periphery of the fitting portion 47a of the cap 47 into the sensor hole 26b.

[0037] Referring to Figure 3B, when light from the light source 43 enters the incident fiber section 45, the light is emitted as inspection light at the tip surface 48 and is reflected by the ground improvement body B in the ground G, etc., and this reflected light is received by the tip surface 48, enters one end of the light receiving fiber section 46, and is received by the light receiving section 44. Here, the light intensity of the reflected light varies depending on the object that reflects the inspection light. Therefore, by detecting the change in the light intensity of the reflected light, the state of the ground improvement body B can be detected.

[0038] Since the first detection structure 30 and the second detection structure 40 detect light reflected from the ground improvement body B around the detection units 32, 42, the positions of the detection units 32, 42 in the circumferential direction of the boring rod 22 have almost no effect on the detection of light intensity. Therefore, there is no need to manage the rotational position of the boring rod 22 to detect light intensity, and monitoring of the ground improvement body B is easy.

[0039] 2, the detection units 32, 42 are attached to the sensor holes 26a, 26b and disposed inside the sensor unit 26. The optical fibers 31, 41 are routed inside the sensor unit 26 and the boring rod body 25, and are drawn out from the fiber-through hole 28a of the upper sensor unit 28 to the outside. The other end of the optical fiber 31 is connected to a light source 33 and a light receiving unit 34 outside the boring rod 22 . The other end of the optical fiber 41 is connected to a light source 43 and a light receiving unit 44 outside the boring rod 22 .

[0040] FIG. 4 is a graph showing the light intensity detected by the monitoring device 20 during the construction of the ground improvement body B by the high-pressure jet mixing device 10. In Figure 4, the horizontal axis shows the number of light intensity measurements, and the vertical axis shows the light intensity. The measurements are taken once per second. In other words, the value shown on the horizontal axis is also the elapsed time (seconds) from the start of construction. In FIG. 4, the light intensity of the light receiving portion 34 of the first detection structure 30 and the light intensity of the light receiving portion 44 of the second detection structure 40 are shown. 4 also shows detection depths GL8 and GL3 that indicate the depth positions of the light receiving units 34 and 44. The detection depth GL8 is 8 m deep from the ground surface, and the detection depth GL3 is 3 m deep from the ground surface.

[0041] In FIG. 4, a first construction stage W1, a second construction stage W2, and a third construction stage W3 are illustrated. In the first construction stage W1, a hardening material (cement milk) and air are sprayed from the nozzle 12a to create a ground improvement body B over a construction range of 12 m to 7 m deep. In the first construction stage W1, the ground G is sandy soil. In the second construction stage W2, pledget injection is performed from the nozzle 12a over a construction range of 4 m to 2.5 m deep. In the pledget injection, only water and air are injected, and the ground G is preliminarily loosened. In the third construction stage W3, after the second construction stage W2, the work returns to a position at a depth of 4 m, and hardening material (cement milk) and air are sprayed from the nozzle 12a over a construction range of 4 m to 2.5 m in depth to create the ground improvement body B. In the second construction stage W2 and the third construction stage W3, the ground G is clayey soil. The depth position of the nozzle 12a is monitored by the nozzle position detection unit (not shown).

[0042] In the construction shown in Figure 4, the effective diameter D (Figure 1) of the ground improvement body B is set to a diameter of 3.5 m. In contrast, the boring rod 22 of the monitoring device 20 is placed at a position corresponding to the diameter of the ground improvement body B of 3.0 m. In other words, the light receiving units 34, 44 are placed at a position corresponding to a radius of the ground improvement body B of 1.5 m.

[0043] Referring to Figure 1, before the start of the first construction stage W1, the boring machine 21 drives the boring rod 22 to drill the observation hole 50. The observation hole 50 is drilled so as to overlap the planned construction area of ​​the ground improvement body B. In the construction of Figure 4, when the observation hole 50 is drilled, the light receiving units 34, 44 are located at a position corresponding to a radius of 1.5 m of the ground improvement body B and at a depth of the detection unit depth GL8.

[0044] When drilling the observation hole 50, the optical fiber 31 is detached from the light source 33 and the light receiving unit 34, and the optical fiber 41 is detached from the light source 43 and the light receiving unit 44. Therefore, when the boring rod 22 is rotated to drill the observation hole 50, the optical fibers 31 and 41 are prevented from becoming entangled with the boring rod 22. Moreover, the optical fibers 31, 41 are passed through the fiber-passing hole 28a (FIG. 2) and are fixed to the boring rod 22 by the fiber-passing hole 28a. Therefore, the optical fibers 31, 41 can rotate integrally with the boring rod 22 while being fixed in the fiber-passing hole 28a, and the optical fibers 31, 41 are prevented from becoming entangled with the boring rod 22. Once drilling of observation hole 50 is completed, optical fiber 31 is connected to light source 33 and light receiving unit 34, and optical fiber 41 is connected to light source 43 and light receiving unit 44.

[0045] First, the detection result of the first detection structure 30 will be described. 4, in the first detection structure 30, in the first construction stage W1, the light intensity of the light receiving unit 34 remains at a substantially constant initial state S1 until approximately 1500 seconds have elapsed (depth position of the nozzle 12a: approximately 10.3 m). When the elapsed time exceeds 1500 seconds, the light intensity increases significantly, and when the elapsed time reaches approximately 2500 seconds (depth position of the nozzle 12a: approximately 8.3 m), the light intensity decreases. Here, in the first construction stage W1, the light receiving unit 34 is fixed at a detection depth GL8. When the depth position of nozzle 12a is between 10.3 m and 8.3 m, it is believed that the curing agent sprayed from nozzle 12a does not reach detection unit 32, but the light intensity increases. This is believed to be because the air sprayed from nozzle 12a flows around detection unit 32 through observation hole 50, changing the conditions around detection unit 32.

[0046] In the first detection structure 30, during the first construction stage W1, from approximately 2500 seconds elapsed (depth position of the nozzle 12a: approximately 8.3 m) to approximately 2850 seconds elapsed (depth position of the nozzle 12a: approximately 7.7 m), the light intensity of the light receiving unit 34 is in an oscillation state S2, where the light intensity oscillates greatly. In the oscillation state S2, the light intensity is higher than in the initial state S1, and the oscillation of the light intensity is greater than in the initial state S1. This is thought to be because the curing material and air sprayed from the nozzle 12a are present around the detection unit 32, causing the reflectance of the reflected light from the tip surface 38 of the detection unit 32 to fluctuate. In this way, when the position of the nozzle 12a detected by the nozzle position detection unit is close to the detection unit depth GL8 and the vibration state S2 is detected, it can be considered that the ground improvement body B has reached the periphery of the detection unit 32. That is, in the case of Figure 4, it can be determined that the ground improvement body B has been constructed at a position corresponding to a diameter of 3.0 m of the ground improvement body B and at a depth of 8 m.

[0047] In the first construction stage W1, the detector 32 is provided at a predetermined depth, ie, a detection depth GL8. The light intensity detected by the light receiver 34 when the position of the nozzle 12a detected by the nozzle position detector reaches 8 m, which is the depth of the detection depth GL8, is defined as a reference light intensity L1. The reference light intensity L1 is detected in the vibration state S2.

[0048] In the first detection structure 30, after the elapsed time exceeds approximately 2850 seconds (depth position of the nozzle 12a: approximately 7.7 m) in the first construction stage W1, an increasing state S3 in which the light intensity of the light receiving unit 34 increases relative to the reference light intensity L1 is detected. When the elapsed time exceeds approximately 2850 seconds, the light intensity rises sharply from the oscillation state S2 to enter the increasing state S3. Specifically, the increasing state S3 is a state in which the light intensity is increased relative to the reference light intensity L1 and maintained for a predetermined period of time. This predetermined period of time may be long enough to distinguish the increasing state S3 from a momentary increase in light intensity due to noise or the like. The light intensity in the increasing state S3 is substantially constant but oscillates to some extent. Furthermore, the frequency of the light intensity in the increasing state S3 is greater than the frequency of the light intensity in the oscillating state S2.

[0049] The reason why the light intensity increases to the state S3 in this way is thought to be that the position of the nozzle 12a moves upward relative to the detection section depth GL8, the hardening material and air sprayed from the nozzle 12a no longer affect the detection section 32, and the movement of the ground improvement body B around the detection section 32 stabilizes. Therefore, by detecting the transition from the vibration state S2 to the increasing state S3, it can be considered that the ground improvement body B has reached the periphery of the detection unit 32. That is, in the case of Figure 4, it can be determined that the ground improvement body B has been constructed up to a position corresponding to at least a diameter of 3.0 m of the ground improvement body B around the 8 m depth position. If the ground improvement body B does not reach the 3.0 m diameter position at a depth of 8 m, it is considered that the increased state S3, which increases relative to the reference light intensity L1, will not be detected.

[0050] Once the first construction stage W1 is completed, the second construction stage W2 begins. In the first detection structure 30, the detection unit 32 moves to a detection depth GL3 in the second construction stage W2. For example, after the first construction stage W1 is completed, the detection depth can be changed from GL8 to GL3 by driving the boring machine 21.

[0051] In the first detection structure 30, during the second construction stage W2, the light intensity of the light receiving unit 34 is in a second vibration state S4, where it oscillates greatly, from approximately 3500 seconds (depth position of the nozzle 12a: approximately 4.0 m) to approximately 3900 seconds (depth position of the nozzle 12a: approximately 2.5 m). This is thought to be because the water and air sprayed from the nozzle 12a are present around the detection unit 32, causing the reflectance of the reflected light from the tip surface 38 of the detection unit 32 to fluctuate.

[0052] When the second construction stage W2 is completed, the nozzle 12a returns to a depth of 4.0 m and the third construction stage W3 begins. In the third construction stage W3, the detector 32 is provided at a predetermined depth, ie, a detection depth GL3. Here, the light intensity detected by the light receiver 34 when the position of the nozzle 12a detected by the nozzle position detector reaches 3 m, which is the depth of the detection depth GL3, is defined as the reference light intensity L2.

[0053] In the first detection structure 30, when the elapsed time exceeds approximately 4650 seconds (depth position of the nozzle 12a: approximately 2.7 m) in the third construction stage W3, an increasing state S5 is detected in which the light intensity of the light receiving unit 34 increases relative to the reference light intensity L2. When the elapsed time exceeds approximately 4650 seconds, the light intensity rises sharply and enters the increasing state S5. The light intensity in the increasing state S5 is approximately constant, but fluctuates to some extent. Furthermore, the light intensity in the increasing state S5 is greater than that in the initial state S1. Specifically, the increasing state S5 is a state in which the light intensity is increased relative to the reference light intensity L2 and maintained for a predetermined period of time. This predetermined period of time may be long enough to distinguish the increasing state S5 from a momentary increase in light intensity due to noise or the like.

[0054] The reason why the light intensity increases to state S5 in this way is thought to be that the position of nozzle 12a moves upward relative to the detection section depth GL3, the hardening material and air sprayed from nozzle 12a no longer affect detection section 32, and the movement of ground improvement body B around detection section 32 stabilizes. Therefore, by detecting the transition from the reference light intensity L2 to the increasing state S5, it can be considered that the ground improvement body B has reached the periphery of the detection unit 32. That is, in the case of Figure 4, it can be determined that the ground improvement body B has been constructed up to a position corresponding to at least a diameter of 3.0 m around the 3 m depth position. If the ground improvement body B does not reach the 3.0 m diameter position at a depth of 3 m, it is considered that the increased state S5, which increases relative to the reference light intensity L2, will not be detected.

[0055] Next, the detection results of the second detection structure 40 will be described. Referring to Figure 4, in the second detection structure 40, in the first construction stage W1, the light intensity of the light receiving unit 44 remains at an approximately constant initial state SS1 until the elapsed time reaches approximately 2850 seconds (depth position of the nozzle 12a: approximately 7.7 m).

[0056] In the first construction stage W1, the detection unit 42 is provided at a predetermined depth, detection depth GL8. Here, the light intensity detected by the light receiving unit 44 when the position of the nozzle 12a detected by the nozzle position detection unit reaches 8 m, which is the depth position of detection depth GL8, is defined as the reference light intensity LL1. The reference light intensity LL1 is detected in the initial state SS1.

[0057] In the second detection structure 40, in the first construction stage W1, an increasing state SS2 in which the light intensity of the light receiving unit 44 increases relative to the reference light intensity LL1 is detected from the time elapsed beyond approximately 2850 seconds (depth position of the nozzle 12a: approximately 7.7 m) until the time elapsed reaches approximately 3150 seconds (depth position of the nozzle 12a: approximately 7.0 m). When the time elapsed exceeds approximately 2850 seconds, the light intensity rises sharply and enters the increasing state SS2. Specifically, the increasing state SS2 is a state in which the light intensity is increased relative to the reference light intensity LL1 and maintained for a predetermined period of time. This predetermined period of time may be long enough to distinguish the increasing state SS2 from a momentary increase in light intensity due to noise or the like. The light intensity in the increasing state SS2 is generally constant, but does fluctuate to some extent.

[0058] The reason why the light intensity reaches the increased state SS2 in this manner is thought to be that the position of the nozzle 12a moves upward relative to the detection unit depth GL8, the ground improvement body B is stably present around the detection unit 42, and the detection unit 42 is stably detecting the reflected light from the ground improvement body B. Therefore, by detecting the transition from the reference light intensity LL1 to the increasing state SS2, it can be considered that the ground improvement body B has reached the periphery of the detection unit 42. That is, in the case of Figure 4, it can be determined that the ground improvement body B has been constructed up to a position corresponding to at least a diameter of 3.0 m of the ground improvement body B around the 8 m depth position. If the ground improvement body B does not reach the 3.0 m diameter position at a depth of 8 m, it is considered that the increased state SS2, which increases relative to the reference light intensity LL1, will not be detected.

[0059] Once the first construction stage W1 is completed, the second construction stage W2 begins. In the second detection structure 40, in the second construction stage W2, the detection section 42 moves to a detection section depth GL3.

[0060] In the second detection structure 40, during the second construction stage W2, from when the elapsed time is approximately 3500 seconds (depth position of the nozzle 12a: approximately 4.0 m) to when the elapsed time is approximately 3900 seconds (depth position of the nozzle 12a: approximately 2.5 m), the light intensity of the light receiving unit 34 is in an oscillation state SS3 where it oscillates greatly. This is thought to be because the water and air sprayed from the nozzle 12a are present around the detection unit 42, causing the light intensity of the reflected light detected by the detection unit 42 to fluctuate.

[0061] When the second construction stage W2 is completed, the nozzle 12a returns to a depth of 4.0 m and the third construction stage W3 begins. In the third construction stage W3, the detection unit 42 is provided at a predetermined depth, that is, a detection depth GL3. Here, the light intensity detected by the light receiving unit 44 when the position of the nozzle 12a detected by the nozzle position detection unit reaches 3 m, which is the depth position of the detection depth GL3, is defined as a reference light intensity LL2.

[0062] In the second detection structure 40, when the elapsed time exceeds approximately 4750 seconds (depth position of the nozzle 12a: approximately 2.6 m) in the third construction stage W3, an increasing state SS4 is detected in which the light intensity of the light receiving unit 44 increases relative to the reference light intensity LL2. When the elapsed time exceeds approximately 4750 seconds, the light intensity rises sharply and enters the increasing state SS4. The light intensity of the increasing state SS4 is approximately constant, but fluctuates to some extent. Furthermore, the light intensity of the increasing state SS4 is greater than that of the initial state SS1. Specifically, the increasing state SS4 is a state in which the light intensity is increased relative to the reference light intensity LL2 and maintained for a predetermined period of time. This predetermined period of time may be long enough to distinguish the increasing state SS4 from a momentary increase in light intensity due to noise or the like.

[0063] The reason why the light intensity reaches the increased state SS4 in this way is thought to be that the position of the nozzle 12a moves upward relative to the detection unit depth GL3, the ground improvement body B is stably present around the detection unit 42, and the detection unit 42 is stably detecting the reflected light from the ground improvement body B. Therefore, by detecting the transition from the reference light intensity LL2 to the increasing state SS2, it can be considered that the ground improvement body B has reached the periphery of the detection unit 42. That is, in the case of Figure 4, it can be determined that the ground improvement body B has been constructed up to a position corresponding to at least a diameter of 3.0 m around the 3 m depth position. If the ground improvement body B does not reach the 3.0 m diameter position at a depth of 3 m, it is considered that the increased state SS4, which increases relative to the reference light intensity LL2, will not be detected.

[0064] FIG. 5 is a graph showing the change in light intensity of the curing agent during the curing process. 5, the horizontal axis indicates the number of measurements of the light intensity detected by the light receiving unit 34, and the vertical axis indicates the light intensity. The above measurement is performed once every five minutes. In FIG. 5, the detection section 32 of the first detection structure 30 is inserted into the hardening material (cement milk), and the light intensity of the reflected light from the hardening material (cement milk) is measured.

[0065] The light intensity rose sharply at approximately the 200th measurement (approximately 16.5 hours later) and the 330th measurement (approximately 27.5 hours later) after the start of construction, and then reached a steady state after approximately the 330th measurement. The change in light intensity corresponds to the change in the moisture content of the curing material. As the moisture content of the curing material decreases, the refractive index of the curing material changes, the reflectance of light at the interface between the detecting unit 32 and the curing material increases, and the light intensity detected by the light receiving unit 34 increases. The change in light intensity corresponds to the change in the refractive index of the curing material. Furthermore, the moisture content of the curing material decreases as the curing progresses. According to this, in FIG. 5, it is believed that the hardening reaction of the hardening material begins to be significant after about 16.5 hours, and the hardening reaction has progressed significantly after about 27.5 hours. That is, by detecting the light intensity with the first detection structure 30, the curing state of the curing agent can be detected.

[0066] For example, in the construction of Fig. 4, after detecting the increased state S3, the hardening state of the ground improvement body B can be detected by maintaining the detection unit 32 at the detection unit depth GL8 and continuing to detect the light intensity as shown in Fig. 5. In other words, the light intensity for the hardening ground improvement body B is detected via the detection unit 32, and if a certain degree of increase in light intensity is detected, it can be determined that the ground improvement body B has hardened well.

[0067] As described above, according to the embodiment to which the present invention is applied, the monitoring device 20 is used when constructing a ground improvement body B in a high-pressure injection mixing method in which a hardening material is injected from the nozzle 12a of the injection pipe 12 inserted into the ground G while the injection pipe 12 is rotated and pulled up to construct a ground improvement body B. The monitoring device 20 includes a cylindrical boring rod 22, a boring machine 21 that drives the boring rod 22 to bore holes in the ground G, and a first detection structure 30 and a second detection structure 40 that detect the state of the ground improvement body B. The first detection structure 30 and the second detection structure 40 include optical fibers 31 and 41, detection units 32 and 42 provided at one ends 31a and 41a of the optical fibers 31 and 41, light sources 33 and 43, and light receiving units 34 and 44. Light from the light sources 33, 43 passes through the optical fibers 31, 41 and is emitted as inspection light from the detection units 32, 42, and the reflected light of the inspection light is received by the detection units 32, 42 and passes through the optical fibers 31, 41 to be received by the light receiving units 34, 44.The detection units 32, 42 are arranged in sensor holes 26a, 26b provided on the outer periphery of the boring rod 22 and are exposed to the ground improvement body B from the sensor holes 26a, 26b. According to this configuration, the detection units 32, 42 provided at one end 31a, 41a of the optical fibers 31, 41 are disposed in the sensor holes 26a, 26b provided on the outer periphery of the boring rod 22. Therefore, when the boring rod 22 is driven by the boring machine 21 to drill a hole in the ground G, the detection units 32, 42 can be positioned in the ground G. The detection units 32, 42 are exposed to the ground improvement body B through the sensor holes 26a, 26b, and the reflected light of the inspection light from the ground improvement body B is received by the detection units 32, 42, allowing the condition of the ground improvement body B to be confirmed in real time. In this way, when the boring rod 22 drills a hole in the ground G, the detection units 32, 42 are also positioned in the ground G together with the boring rod 22, and the detection units 32, 42 can be exposed to the ground improvement body B, allowing the condition of the ground improvement body B to be easily confirmed in real time.

[0068] In addition, the detection unit 32, 42 is composed of a cap 37, 47 which has a cylindrical fitting portion 37a, 47a that fits onto the outer periphery of one end 31a, 41a, and a cover portion 37b, 47b that covers one end 31a, 41a in the axial direction of the optical fiber 31, 41 and is exposed to the ground improvement body B, and the outer periphery of the fitting portion 37a, 47a of the detection unit 32, 42 is fitted into the sensor hole 26a, 26b. According to this configuration, the cover portions 37b, 47b of the caps 37, 47, which function as detection portions, can be used to protect the one ends 31a, 41a of the optical fibers 31, 41. Furthermore, because the outer peripheries of the cylindrical fitting portions 37a, 47a of the caps 37, 47 are fitted into the sensor holes 26a, 26b, even if the optical fibers 31, 41 are linear, the one ends 31a, 41a can be firmly fixed to the sensor holes 26a, 26b by using the caps 37, 47.

[0069] The cover portion 37b has an incident side inclined surface 38a inclined with respect to the axis 35a of the one end 31a of the optical fiber 31. According to this configuration, since the cover portion 37b of the detection unit 32 has an incident side inclined surface 38a, by receiving the reflected light from the cover portion 37b with the light receiving unit 34, changes in the refractive index of the ground improvement body B can be detected, and the condition of the ground improvement body B can be confirmed in real time based on the changes in the refractive index.

[0070] In addition, the optical fibers 31, 41 are detachably attached to the light sources 33, 43 and the light receiving units 34, 44, and when the boring rod 22 is rotated by the boring machine 21, the optical fibers 31, 41 are detached from the light sources 33, 43 and the light receiving units 34, 44. According to this configuration, the optical fibers 31, 41 can rotate integrally with the boring rod 22 without being restricted by the light sources 33, 43 and the light receiving units 34, 44. This prevents the optical fibers 31, 41 from becoming entangled with the boring rod 22, and allows the boring rod 22 to easily drill a hole.

[0071] Furthermore, the boring rod 22 has a fiber passing hole 28a through which the optical fibers 31, 41 pass from the inside to the outside of the boring rod 22, and when the boring rod 22 is rotated, the optical fibers 31, 41 are fixed to the boring rod 22 by the fiber passing hole 28a and rotate integrally with the boring rod 22. According to this configuration, by utilizing the fiber passing holes 28a through which the optical fibers 31, 41 pass from the inside to the outside of the boring rod 22, the optical fibers 31, 41 can be fixed to the boring rod 22 with a simple structure, and the optical fibers 31, 41 can be rotated integrally with the boring rod 22. This makes it possible to prevent the optical fibers 31, 41 from becoming entangled with the boring rod 22, and allows the boring rod 22 to easily bore holes.

[0072] The boring rod 22 also includes a cylindrical boring rod main body 25, a cylindrical sensor section 26 connected to the lower end of the boring rod main body 25 and shorter than the boring rod main body 25, and a bit 27 connected to the lower end of the sensor section 26. The optical fibers 31, 41 are routed within the boring rod main body 25 and the sensor section 26, and the sensor holes 26a, 26b are provided in the sensor section 26. According to this configuration, the sensor holes 26a, 26b are provided in the cylindrical sensor part 26, which is shorter than the boring rod main body 25, so that the detection parts 32, 42 can be easily attached to the sensor holes 26a, 26b. Also, since the optical fibers 31, 41 are routed inside the boring rod main body 25 and the sensor part 26, the optical fibers 31, 41 can be effectively protected from the ground G. Furthermore, since the detection parts 32, 42 can be provided in positions close to the bit 27, the detection parts 32, 42 can be easily positioned deep in the ground G.

[0073] The monitoring method of this embodiment is a monitoring method used when constructing a ground improvement body B in a high-pressure injection mixing method in which a hardening material is injected from the nozzle 12a of an injection pipe 12 inserted into the ground G while the injection pipe 12 is rotated and pulled up to construct a ground improvement body B. In this method, a boring rod 22 is driven by a boring machine 21 to drill a hole in the ground G, and the condition of the ground improvement body B is detected by a detection structure (first detection structure 30, second detection structure 40) comprising optical fibers 31, 41, detection units 32, 42 provided on one ends 31a, 41a of the optical fibers 31, 41, light sources 33, 43, and light receiving units 34, 44. Light from the light sources 33, 43 passes through the optical fibers 31, 41 and is emitted as inspection light from the detection units 32, 42, and the reflected light of the inspection light is received by the detection units 32, 42 and passes through the optical fibers 31, 41 and is received by the light receiving units 34, 44, and the reflected light is received by the detection units 32, 42 exposed to the ground improvement body B through sensor holes 26a, 26b provided on the outer periphery of the boring rod 22. According to this method, when the boring rod 22 is driven by the boring machine 21 to drill a hole in the ground G, the detection units 32, 42 provided at one end 31a, 41a of the optical fibers 31, 41 are exposed to the ground improvement body B through the sensor holes 26a, 26b provided on the outer periphery of the boring rod 22, and the reflected light of the inspection light from the ground improvement body B is received by the detection units 32, 42, allowing the condition of the ground improvement body B to be confirmed in real time. In this way, when the boring rod 22 drills a hole in the ground G, the detection units 32, 42 are also located in the ground G together with the boring rod 22, and the detection units 32, 42 can be exposed to the ground improvement body B, making it possible to easily check the condition of the ground improvement body B in real time.

[0074] Furthermore, the detection units 32, 42 are fixed at detection unit depths GL3, GL8, which are predetermined depth positions within the ground G, and the ground improvement body B is created by pulling up the nozzle 12a from a position deeper than the detection units 32, 42. The light intensity received by the light receiving unit 34 when the depth position of the nozzle 12a reaches the detection unit depth GL8 is set to the reference light intensity L1, and when the light intensity received by the light receiving unit 34 increases relative to the reference light intensity L1 as the nozzle 12a is pulled up and reaches an increasing state S3 in which the increased state is maintained for a predetermined time, it is determined that the ground improvement body B has reached the position of the detection unit 32 in the radial direction of the ground improvement body B at the detection unit depth GL8. According to this method, when the light intensity transitions to an increasing state S3 relative to the reference light intensity L1, it can be determined that the ground improvement body B has reached the position of the detection unit 32 in the radial direction of the ground improvement body B at the detection unit depth GL8, and the condition of the ground improvement body B can be easily confirmed in real time. Furthermore, when the light intensity transitions to an increasing state S5 relative to the reference light intensity L2, it can be determined that the ground improvement body B has reached the position of the detection unit 32 in the radial direction of the ground improvement body B at the detection unit depth GL3, and the state of the ground improvement body B can be easily confirmed in real time. Furthermore, when the light intensity transitions to an increasing state SS2 relative to the reference light intensity LL1, it can be determined that the ground improvement body B has reached the position of the detection unit 32 in the radial direction of the ground improvement body B at the detection unit depth GL8, and the condition of the ground improvement body B can be easily confirmed in real time. Furthermore, when the light intensity transitions to an increasing state SS4 relative to the reference light intensity LL2, it can be determined that the ground improvement body B has reached the position of the detection unit 32 in the radial direction of the ground improvement body B at the detection unit depth GL3, and the condition of the ground improvement body B can be easily confirmed in real time.

[0075] Furthermore, the detection unit 32 has a tip surface 38 that is exposed to the ground improvement body B and covers one end 31a in the axial direction of the optical fiber 31, and the tip surface 38 has an incident side inclined surface 38a that is inclined with respect to the axis 35a of one end 31a of the optical fiber 31. After the ground improvement body B is constructed, the state of the ground improvement body B during hardening is detected by the detection unit 32, and the hardening state of the ground improvement body B is determined based on the intensity of the light received by the light receiving unit 34. According to this method, since the tip surface 38 of the detection unit 32 has an incident-side inclined surface 38a, the reflected light from the incident-side inclined surface 38a is received by the light-receiving unit 34, thereby making it possible to detect changes in the refractive index of the ground improvement body B. Then, based on the changes in the refractive index of the ground improvement body B, the hardening state of the ground improvement body B can be confirmed in real time.

[0076] Although one embodiment of the present invention has been described above, the present invention is not limited to the specific embodiment, and unless otherwise limited in the above description, various modifications and changes are possible within the scope of the spirit of the present invention as set forth in the claims. Furthermore, the effects of the above embodiment are merely examples of the effects that can be obtained from the present invention, and do not mean that the effects of the present invention are limited to the above effects. In the above embodiment, it has been explained that the detection depth is changed from GL8 to GL3 by driving the boring machine 21 after the first construction stage W1 is completed, but the present invention is not limited to this. For example, multiple monitoring devices 20 may be provided, and the ground improvement body B at the detection depth GL8 and the ground improvement body B at the detection depth GL3 may be monitored by different monitoring devices. Alternatively, multiple sensor units 26 equipped with light receiving units 34, 44 may be provided in the axial direction of the boring rod, and the conditions of the ground improvement bodies at different depths may be monitored simultaneously. [Explanation of symbols]

[0077] 12: Injection tube 12a: Nozzle 20: Monitoring equipment 21: Bowling machine 22: Bowling rod 25: Boring rod body 26: Sensor section 26a, 26b: sensor holes 27: Bit 28a: Fiber hole 30: First detection structure (detection structure) 31, 41: Optical fiber 31a, 41a: One end 32, 42: Detection unit 33,43:Light source 34,44: Light receiving part 35a: Axis 38: Tip surface 38a: Inclined surface on the incident side (slanted surface) 40: Second detection structure (detection structure) B: Ground improvement body G: Ground GL3, GL8: Detection depth (predetermined depth position) L1, L2, LL1, LL2: Reference light intensity S3, S5, SS2, SS4: Increased state

Claims

1. In a high-pressure injection mixing method in which a ground improvement body is created by injecting a hardening material from the nozzle of an injection pipe inserted into the ground and lifting the injection pipe while rotating, a monitoring device is used when creating the ground improvement body, A cylindrical boring rod, a boring machine that drives the boring rod to drill holes in the ground, and a detection structure that detects the state of the ground improvement body, the detection structure includes an optical fiber, a detection unit provided at one end of the optical fiber, a light source, and a light receiving unit; light from the light source passes through the optical fiber and is emitted from the detection unit as inspection light, and reflected light of the inspection light is received by the detection unit and is received by the light receiving unit through the optical fiber; The detection unit is a monitoring device that is placed in a sensor hole provided on the outer periphery of the boring rod and is exposed to the ground improvement body from the sensor hole.

2. The detection unit is configured by a cap having a cylindrical fitting portion that fits onto the outer periphery of the one end and a cover portion that covers the one end in the axial direction of the optical fiber and is exposed to the ground improvement body, The monitoring device according to claim 1 , wherein the outer periphery of the fitting portion of the detection unit is fitted into the sensor hole.

3. The monitoring device according to claim 1 , wherein the cover portion has an inclined surface inclined with respect to the axis of the one end of the optical fiber.

4. the optical fiber is detachably provided with respect to the light source and the light receiving unit, 2. The monitoring device according to claim 1, wherein the optical fiber is detached from the light source and the light receiving unit when the boring rod is rotationally driven by the boring machine.

5. The boring rod has a fiber passing hole through which the optical fiber passes from the inside to the outside of the boring rod, 5. The monitoring device according to claim 4, wherein when the boring rod is rotated, the optical fiber is fixed to the boring rod by the fiber-through hole and rotates integrally with the boring rod.

6. The boring rod comprises a cylindrical boring rod body, a cylindrical sensor part connected to a lower end of the boring rod body and shorter than the boring rod body, and a bit connected to a lower end of the sensor part, 2. The monitoring device according to claim 1, wherein the optical fiber is arranged in the boring rod body and the sensor portion, and the sensor hole is provided in the sensor portion.

7. In a high-pressure injection mixing method in which a ground improvement body is created by injecting a hardening material from the nozzle of an injection pipe inserted into the ground and lifting the injection pipe while rotating, a monitoring method used when creating the ground improvement body is A boring rod is driven by a boring machine to bore a hole in the ground; The state of the ground improvement body is detected by a detection structure including an optical fiber, a detection unit provided at one end of the optical fiber, a light source, and a light receiving unit, light from the light source passes through the optical fiber and is emitted from the detection unit as inspection light, and reflected light of the inspection light is received by the detection unit and is received by the light receiving unit through the optical fiber; A monitoring method in which the reflected light is received by the detection unit exposed to the ground improvement body through a sensor hole provided on the outer periphery of the boring rod.

8. The detection unit is fixed at a predetermined depth position in the ground, The nozzle is pulled up from a position deeper than the detection unit to create the ground improvement body, a light intensity received by the light receiving unit when the depth position of the nozzle reaches the predetermined depth position is defined as a reference light intensity; A monitoring method as described in claim 7, in which, when the light intensity received by the light receiving unit increases relative to the reference light intensity as the nozzle is pulled up and this increased state is maintained for a predetermined period of time, it is determined that the ground improvement body has reached the position of the detection unit in the radial direction of the ground improvement body at the predetermined depth position.

9. The detection unit has a tip surface that is exposed to the ground improvement body and covers the one end in the axial direction of the optical fiber, and the tip surface has an inclined surface inclined with respect to the axis of the one end of the optical fiber, After constructing the ground improvement body, the state of the ground improvement body during hardening is detected by the detection unit, The monitoring method according to claim 7, wherein the hardening state of the ground improvement body is determined based on the intensity of light received by the light receiving unit.

Images