Shear Wave Velocity Measurement System

Abstract

To provide a shear wave speed measurement sensor and shear wave speed measurement system which can be easily installed without reducing the rigidity of a ground improvement body.SOLUTION: A shear wave speed measurement system 3 is provided in a ground improvement body 2 which includes a wall body 21 in a lattice shape in the plan view prepared in the ground, and includes an oscillation part 11 which oscillates a shear wave, a reception part 12 which receives the shear wave oscillated from the oscillation part 11, and a bracing 13 which connects the oscillation part 11 and the reception part 12. The speed of the shear wave propagating in the bracing 13 is slower than the speed of the shear wave propagating in the ground improvement body 2. The bracing 13 comprises: a shear wave speed measurement sensor 1 which has the rigidity that does not generate deformation in the time of installation to the ground improvement body 2; a processing unit which is provided on the outside of the ground improvement body 2, measures the shear wave speed and calculates a residual strain on the basis of the measured shear wave speed; and a waveform generation device which is provided on the outside of the ground improvement body 2 and oscillates the shear wave from the oscillation part 11.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention ,height This paper relates to a shear wave velocity measurement system. [Background technology]

[0002] Conventionally, as a countermeasure against liquefaction in liquefiable ground such as sandy ground where liquefaction is expected to occur during an earthquake, a construction method has been adopted in which a ground improvement body consisting of a lattice-shaped wall in plan view is constructed in the ground to suppress ground deformation in the liquefiable layer.

[0003] Such ground improvement bodies may crack or break if subjected to loads exceeding the design seismic force. Therefore, a method of observing shear waves using sensors embedded in the ground is used to observe whether or not the ground improvement body is damaged and where the damage is.

[0004] For example, Patent Document 1 discloses a method in which an oscillatory bender element and a receiver bender element are installed in a borehole excavated in the ground near a ground improvement body, and the shear wave velocity in the initial state without damage to the ground improvement body and after an earthquake occurs are measured at the in-situ position of the ground improvement body.

[0005] For example, Patent Document 2 discloses a method for measuring shear wave intensity at a predetermined depth by installing two base plates, each equipped with an oscillatory bender element and a receiver bender element, in the ground with their mounting positions and separation adjusted using guide rods. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-38587 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-286464 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the method of installing a bender element in a borehole described in Patent Document 1 requires the ground near the ground improvement body to be excavated separately in advance, which may reduce the construction efficiency of the ground improvement body and may damage the side of the ground improvement wall.

[0008] Regarding the method of adjusting the height of two base plates in Patent Document 2, the installation surface area of the base plate is large compared to the bender element, so there is a risk that the installation of the base plate will reduce the rigidity of the ground improvement body. On the other hand, if the thickness of the wall of the ground improvement body is increased in consideration of the above issues, there is a risk that the construction efficiency of the sensor and the wall of the ground improvement body will decrease.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a method for easily installing a ground improvement body without reducing the rigidity of the ground improvement body. Ruse The present invention provides a shear wave velocity measurement system. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, the shear wave velocity measuring sensor of the present invention is provided in a ground improvement body consisting of a lattice-shaped wall constructed in the ground in a planar view, and comprises an oscillator unit that emits shear waves, a receiver unit that receives the shear waves emitted from the oscillator unit, and a joint member that connects the oscillator unit and the receiver unit, wherein the speed of the shear waves propagating through the joint member is slower than the speed of the shear waves propagating through the ground improvement body, and the joint member has rigidity that prevents deformation when installed in the ground improvement body.

[0011] With the above configuration, the shear wave velocity measurement sensor can fix the separation distance between the oscillator and receiver using the joint, accurately maintaining the shear wave propagation distance between the oscillator and receiver, and accurately transmitting and receiving shear waves.The shear wave velocity measurement sensor can easily distinguish between the velocities of the two types of shear waves because the speed of shear waves propagating through the joint is slower than the speed of shear waves propagating through the ground improvement body.As a result, the shear wave velocity measurement sensor can accurately measure the speed of shear waves propagating through the ground improvement body. The shear wave velocity measurement sensor can be easily installed without reducing the rigidity of the ground improvement body because the joint material has enough rigidity to prevent deformation when installed in the ground improvement body. The shear wave velocity measurement sensor has a simple structure in which the emitting part and receiving part are fixed to a joint material, and when it is installed in the ground improvement body, the work of drilling additional holes in the ground for installation can be omitted. This reduces the occurrence of damage such as breakage of the ground improvement body, avoids a decrease in the rigidity of the ground improvement body, and improves construction efficiency.

[0012] In the shear wave velocity measurement sensor according to the present invention, the propagation distance of the shear wave in the joint may be longer than the separation distance between the oscillator and the receiver.

[0013] With the above configuration, the shear wave velocity measurement sensor can easily determine the propagation time of the shear wave emitted from the oscillator and received by the receiver, thereby easily and accurately measuring the propagation time of the shear wave and more accurately calculating the shear wave velocity calculated from the propagation time of the shear wave.

[0014] In addition, in the shear wave velocity measurement sensor of the present invention, the joint member may include a first extension portion extending in one direction, a second extension portion extending in another direction from one end of the first extension portion, and a third extension portion extending parallel to the second extension portion from the other end of the first extension portion, and the oscillating portion may protrude from the tip of the second extension portion toward the third extension portion, and the receiving portion may protrude from the tip of the third extension portion toward the second extension portion.

[0015] With the above configuration, the shear wave velocity measurement sensor has an oscillating section and a receiving section respectively provided at the tips of the second and third extension sections which extend parallel to both ends of the first extension section, so that with a simpler configuration, the propagation distance of the shear wave in the joint can be reliably made longer than the separation distance between the oscillating section and the receiving section. The shear wave velocity measurement sensor is formed with a simple linear outer shape for the joint, which improves installation efficiency.

[0016] In the shear wave velocity measurement sensor according to the present invention, the joint member may be made of resin.

[0017] With the above configuration, the shear wave velocity measurement sensor can form a joint using a resin that allows the speed of shear waves propagating through the joint to be slow. Because the shear wave velocity measurement sensor is formed using a resin, it is easier to process joints that have a portion that bends by approximately 90 degrees, thereby improving the workability of the joint.

[0018] In the shear wave velocity measurement sensor according to the present invention, the maximum thickness of each extension portion of the joint member in a direction perpendicular to the extension direction may be 10 mm or less.

[0019] With the above configuration, the shear wave velocity measurement sensor can be formed so that the cross section in the extension direction of the joint takes into account the rigidity of the ground improvement body when installed in the ground improvement body, thereby more reliably suppressing the decrease in rigidity of the ground improvement body due to the installation of the shear wave velocity measurement sensor in the ground improvement body. Since the maximum thickness of the shear wave velocity measurement sensor is specified, it can be a simple and small sensor, which reduces the effort required to install it in the ground improvement body.

[0020] In order to achieve the above-mentioned object, the shear wave velocity measurement system of the present invention comprises the shear wave velocity measurement sensor described above, a processing unit that is provided outside the ground improvement body and measures the velocity of shear waves and calculates residual strain based on the measured shear wave velocity, and a waveform generating device that is provided outside the ground improvement body and causes shear waves to be generated from the oscillator unit, and is characterized in that the processing unit measures the velocity of the shear waves that are generated from the oscillator unit, propagate through the ground improvement body, and are received by the receiver unit, and calculates the residual strain of the ground improvement body.

[0021] With the above configuration, the shear wave velocity measurement system can measure the velocity of shear waves propagating through the ground improvement body with high accuracy using the shear wave velocity measurement sensor, and can therefore calculate the residual strain in the ground improvement body with high accuracy. The shear wave velocity measurement system has a configuration in which the shear wave velocity measurement sensor joint has rigidity that prevents deformation when installed in the ground improvement body, and the processing unit that calculates the residual strain is located outside the ground improvement body, so that the rigidity of the ground improvement body is not reduced.

[0022] In addition, in the shear wave velocity measurement system according to the present invention, a plurality of the shear wave velocity measurement sensors may be provided in the ground improvement body.

[0023] With the above configuration, the shear wave velocity measurement system can measure the velocity of shear waves at multiple locations, thereby improving the measurement accuracy of the velocity of shear waves propagating through the ground improvement body. Furthermore, because the measurement locations for shear wave velocity are dispersed, the velocity of shear waves propagating through the ground improvement body can be measured with high accuracy even when the ground improvement body has structural constraints such as a complex or large structure.

[0024] In addition, the shear wave velocity measuring system of the present invention may include a first connecting cable that connects the oscillator unit and the waveform generating device so that the oscillator unit can oscillate, and a second connecting cable that connects the receiver unit and the processing unit so that the residual strain of the ground improvement body can be measured, and the joint member may be formed with a first hollow portion through which the first connecting cable is inserted and a second hollow portion through which the second connecting cable is inserted.

[0025] With the above configuration, the shear wave velocity measurement system can place the first connection cable and the second connection cable in the joint material, making it easy to protect the first connection cable and the second connection cable from the external environment.

[0026] In the shear wave velocity measurement system according to the present invention, the first hollow portion and the second hollow portion may be filled with a filler.

[0027] With the above configuration, the shear wave velocity measurement system can suppress vibration of the first connection cable and the second connection cable within the first hollow portion and the second hollow portion of the joint member, thereby preventing deterioration or breakage of the connection cables due to vibration. [Effects of the Invention]

[0028] According to the present invention, the soil improvement body can be easily installed without reducing its rigidity. Ruse A shear wave velocity measurement system can be provided. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a plan view illustrating an example of a shear wave velocity measurement sensor according to an embodiment of the present invention. [Figure 2] FIG. 1 is a perspective view showing a shear wave velocity measurement sensor according to an embodiment of the present invention attached to a ground improvement body. [Figure 3] 2A is a cross-sectional view taken along line AA in FIG. 1, and FIG. 2B is a cross-sectional view taken along lines BB and CC in FIG. [Figure 4] 1A and 1B are explanatory diagrams showing the results of an accuracy experiment on a shear wave velocity measurement sensor according to an embodiment of the present invention, where (a) shows the progression of the oscillation wave in this embodiment and a conventional method, and (b) shows the progression of the received wave in this embodiment and a conventional method. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, a shear wave velocity measuring sensor and a shear wave velocity measuring system according to an embodiment of the present invention will be described with reference to FIGS.

[0031] As shown in Fig. 1, the shear wave velocity measurement sensor 1 includes an oscillator 11, a receiver 12, and a joint 13. The oscillator 11 and receiver 12 are formed from known bender elements and are capable of emitting and receiving shear waves in horizontal, vertical, and oblique directions.

[0032] The joint 13 has a first extension 131, a second extension 132, and a third extension 133, and connects the oscillator 11 and the receiver 12. As shown in FIG. 2, the shear wave velocity sensor 1 is erected with the oscillator 11 and the receiver 12 at the bottom and buried in the ground improvement body 2. Hereinafter, the horizontal separation direction between the oscillator 11 and the receiver 12 when the shear wave velocity sensor 1 is buried is referred to as the X direction, the depth direction when the shear wave velocity sensor 1 is buried is referred to as the Y direction, and the height direction when the shear wave velocity sensor 1 is buried is referred to as the Z direction.

[0033] The oscillator 11 oscillates an oscillatory wave W1 that propagates through the ground improvement body 2, and the receiver 12 receives a received wave W2 that has propagated through the ground improvement body 2.

[0034] The ground improvement body 2 is installed as a liquefaction countermeasure for unimproved ground (not shown). The ground improvement body 2 is composed of walls 21 formed by, for example, excavating unimproved ground, filling holes formed with a filler such as cement or concrete in a grid pattern in a plan view, and solidifying the filler, and the inside of each grid is the improved ground.

[0035] The first extension portion 131 is formed to extend in the X direction. The second extension portion 132 is formed to extend downward in the Z direction from one end 131a of the first extension portion 131 in the X direction. The third extension portion 133 is formed to extend downward in the Z direction from the other end 131b of the first extension portion 131. The second extension portion 132 and the third extension portion 133 extend parallel to the Z direction.

[0036] The second extension portion 132 and the third extension portion 133 are bent at approximately 90° with respect to the first extension portion 131 in a downward direction in the Z direction at a portion where they are continuous with the first extension portion 131.

[0037] The oscillator 11 is provided to protrude rightward in the X direction from an inner surface 132b of a tip 132a of the second extension portion 132 toward the third extension portion 133. The receiver 12 is provided to protrude leftward in the X direction from an inner surface 133b of a tip 133a of the third extension portion 133 toward the second extension portion 132.

[0038] The oscillation unit 11 is bent at approximately 90° to the right in the X direction at the continuation with the inner surface 132b of the second extension portion 132. The oscillation unit 12 is bent at approximately 90° to the left in the X direction at the continuation with the inner surface 133b of the third extension portion 133.

[0039] The joint 13 is formed so that the speed V1 of the shear wave W3 propagating through the joint 13 is slower than the speed V2 of the shear wave W4 propagating through the ground improvement body 2. The speed V2 of the shear wave W4 propagating through the ground improvement body 2 is normally 400 m / s or more, for example, when the ground improvement body 2 is formed from a cement-based material, which is the main material used in liquefaction countermeasure works. The joint 13 is formed, for example, from a resin material such that the speed V1 of the shear wave W3 propagating through the joint 13 is approximately 350 m / s.

[0040] The joint 13 is formed so that the propagation distance D1 of the shear wave W3 propagating through the joint 13 is longer than the separation distance D2 between the oscillation section 11 and the receiving section 12. The separation distance D2 between the oscillation section 11 and the receiving section 12 is preferably 20 cm to 100 cm. The joint 13 is not limited to a configuration in which it is bent at approximately 90° at the continuous section between each of the extension sections described above, and it is sufficient that the propagation distance D1 of the shear wave W3 propagating through the joint 13 is longer than the separation distance D2 between the oscillation section 11 and the receiving section 12.

[0041] 3, the joint member 13 is formed so that the cross sections of the second extension portion 132 and the third extension portion 133 along the XY plane and the cross section of the first extension portion 131 along the YZ plane are substantially rectangular. The first extension portion 131, the second extension portion 132, and the third extension portion 133 of the joint member 13 may be formed from a single member, or may be formed from different members and connected at one end 131a and the other end 131b.

[0042] The joint material 13 is made of a resin material and has a rigidity sufficient to prevent deformation when the shear wave velocity measurement sensor 1 is installed in the ground improvement body 2.

[0043] The material of the joint 13 may be selected depending on the velocity V2 of the shear wave W4 propagating through the ground improvement body 2, and the material of the joint is not limited to resin.

[0044] The Y-direction thickness D3 and the Z-direction thickness D4 of the first extension portion 131 are both 10 mm or less. The X-direction thickness D5 and the Y-direction thickness D6 of the second extension portion 132 are both 10 mm or less. Similarly, the X-direction thickness D5 and the Y-direction thickness D6 of the third extension portion 133 are both 10 mm or less.

[0045] As shown in FIG. 2, the shear wave velocity measurement system 3 includes a shear wave velocity measurement sensor 1, a processing unit 31a (not shown), and a waveform generator 31b (not shown). The processing unit 31a measures the velocity V2 of the shear wave W4 from the oscillation wave W1 generated by the oscillation unit 11 and the received wave W2 received by the receiver 12, and calculates the residual strain γ1 based on the measured velocity V2. The waveform generator 31b applies a current of a predetermined frequency to the oscillation unit 11, vibrating the vibrator constituting the oscillation unit 11 to generate the oscillation wave W1, and transmits data on the current and frequency passed through the oscillation unit 11 to the processing unit 31a. The shear wave velocity measurement system 3 calculates the residual strain γ1 of the ground improvement body 2 through the above processing, thereby detecting damage to the ground improvement body 2 and determining whether or not the ground improvement body 2 needs to be continued to be used.

[0046] The processing unit 31a includes a data processing unit 31c and a determination unit 31d (not shown). The processing unit 31a is connected to the receiving unit 12 and is provided outside the ground improvement body 2. The waveform generating device 31b is connected to the oscillator 11 and is provided outside the ground improvement body 2. The data processing unit 31c measures the velocity V2 of the shear wave W4 from the oscillator wave W1 emitted from the oscillator 11 and the received wave W2 received by the receiving unit 12, and performs processing to calculate the residual strain γ1 based on the measured shear wave velocity V2.

[0047] The speed V2 of the shear wave W4 propagating through the ground improvement body 2 is calculated from the time required for the oscillatory wave W1 to be emitted from the oscillator 11 and for the received wave W2 to be received by the receiver 12, and the separation distance D2 between the oscillator 11 and the receiver 12. The time required for the oscillatory wave W1 to be emitted and for the received wave W2 to be received is defined as the propagation time T1.

[0048] Residual strain is calculated by determining the shear wave velocity ratio (V2 / V3) when the shear wave velocity measurement sensor 1 is in situ based on the measured shear wave velocity V2 of shear wave W4, and then calculating residual strain γ1 from the relationship between the shear wave velocity ratio and strain. Here, velocity V3 is the velocity of shear wave W4 in the 28-day-old ground improvement body 2. Velocity V2 is the velocity of shear wave W4 measured using the transmitter 11 and receiver 12. Since the ground improvement body 2 is made of cement-based materials, which are the main materials used in liquefaction countermeasures, it exhibits brittle behavior, so the maximum strain generated during vibration is considered to be the residual strain γ1. Using the above relationship, the residual strain γ1 of the ground improvement body 2 can be calculated from the velocity V2 of the shear wave W4 in the ground improvement body 2.

[0049] The judgment unit 31d judges the damage state of the ground improvement body 2 and evaluates its performance based on known judgment and evaluation indexes from the residual strain γ1, and determines whether or not the ground improvement body 2 needs to be used continuously.

[0050] The shear wave velocity measurement system 3 may be configured with multiple shear wave velocity measurement sensors 1 provided within the ground improvement body 2, taking into consideration the accuracy required for the residual strain γ1 of the ground improvement body 2 for measuring the velocity V2 of the shear wave W4 and conditions such as the dimensions of the ground improvement body 2. In this case, the velocity V2 of the shear wave W4 is measured at multiple points, which further improves the measurement accuracy of the velocity of the shear wave W4 propagating through the ground improvement body 2. Furthermore, because the measurement points for the velocity V2 of the shear wave W4 are dispersed, the velocity V2 of the shear wave W4 propagating through the ground improvement body 2 can be measured with high accuracy at multiple points and in multiple directions even if the ground improvement body 2 has structural constraints such as a complex or large structure.

[0051] The shear wave velocity measurement system 3 includes a first connection cable 32 that connects the oscillator 11 and the waveform generator 31b. The waveform generator 31b applies a current of a predetermined frequency to the oscillator 11 via the first connection cable 32. The shear wave velocity measurement system 3 also includes a second connection cable 33 that connects the receiver 12 and the processor 31a. Data such as the waveform of the received wave W2 received by the receiver 12 is transmitted to the processor 31a via the second connection cable 33.

[0052] 2 and 3(b), the joint 13 has a first hollow portion 132c formed inside the second extension portion 132 and extending in the Z direction. The first hollow portion 132c is formed so that its cross section along the XY plane is substantially rectangular, similar to the cross-sectional shape of the second extension portion 132 along the XY plane. The first hollow portion 132c is formed with separation distances D7 and D8 on both sides in the X direction from the edge portion 134 in the cross section along the XY plane, and similarly is formed with separation distances D9 and D10 on both sides in the Z direction from the edge portion 134.

[0053] In the first hollow portion 132c, a communication hole 132d communicating with the oscillator 11 is formed at a portion where the oscillator 11 and the second extension portion 132 are connected, and an opening 132e opening toward the outside is formed at a portion where the first extension portion 131 and the second extension portion 132 are connected. The communication hole 132d and the opening 132e have a size that allows the first connection cable 32 to pass through. The first hollow portion 132c may be extended to one end 131a of the first extension portion 131.

[0054] One end of the first connection cable 32 is connected to the oscillator 11, is disposed in the first hollow portion 132c through the communication hole 132d, extends to the outside of the extension member 13 from the opening 132e, and is connected at the other end to the waveform generator 31b. The first hollow portion 132c functions as a wiring route for the first connection cable 32 passing through the extension member 13.

[0055] Similarly, in the joint 13, a second hollow portion 133c extending in the Z direction is formed inside the third extension portion 133. The second hollow portion 133c is formed so that its cross section along the XY plane is substantially rectangular, similar to the cross-sectional shape of the third extension portion 133 along the XY plane. The second hollow portion 133c is formed with separation distances D7 and D8 on both sides in the X direction from the edge portion 134 in the cross section along the XY direction, and similarly is formed with separation distances D9 and D10 on both sides in the Z direction from the edge portion 134.

[0056] The second hollow portion 133c has a communication hole 133d formed therein that communicates with the vibration receiving portion 12 at the connection between the vibration receiving portion 12 and the third extension portion 133, and an opening 133e that opens toward the outside at the connection between the first extension portion 131 and the third extension portion 133. The communication hole 133d and the opening 133e have a size that allows the second connection cable 33 to pass through. The second hollow portion 133c may be extended to the other end 131b of the first extension portion 131.

[0057] The second connection cable 33 has one end connected to the receiving part 12, is disposed in the second hollow part 133c through the communication hole 133d, extends to the outside of the joint 13 from the opening 133e, and has the other end connected to the processing part 31a. The second hollow part 133c functions as a wiring route for the second connection cable 33 passing through the joint 13.

[0058] The first hollow portion 132c and the second hollow portion 133c are each filled with a filler 135. Any filler 135 may be used as long as it can fill the first hollow portion 132c and the second hollow portion 133c without leaving any gaps, and for example, a known epoxy adhesive may be used.

[0059] The second extending portion 132 and the third extending portion 133 are formed, for example, with a thickness D5 of 5 mm in the X direction and a thickness D6 of 10 mm in the Y direction. The first hollow portion 132c and the second hollow portion 133c are formed, for example, with a thickness D11 of 3 mm in the X direction and a thickness D12 of 6 mm in the Y direction.

[0060] The processing unit 31a may be, for example, a known oscilloscope that displays the time transition of the waveforms of the oscillating wave W1 and the receiving wave W2 in the oscillator 11 and the receiving unit 12, or a known amplifier that makes it easier to distinguish the waveform shapes of the oscillating wave W1 and the receiving wave W2 displayed on the oscilloscope. In either case, the oscillator 11 and the receiving unit 12 use known bender elements.

[0061] A demonstration experiment was conducted to confirm the measurement accuracy of the velocity V2 of the shear wave W4 by the shear wave velocity measurement sensor 1 according to this embodiment (hereinafter referred to as "Case 1") and the conventional method (hereinafter referred to as "Case 2"). Case 2 is the method described in Patent Document 1. Specifically, this method involves bringing an oscillator and a receiver into contact with the soil improvement body specimen 20 used in the experiment from the side of the soil improvement body specimen 20, and emitting and receiving vibrations.

[0062] The ground improvement specimen 20 used in the experiment is prepared so that the velocity V2 of the propagating shear wave W4 is in the range of 500 to 650 m / s. The ground improvement specimen 20 is a cement-based ground improvement specimen with an age of one day.

[0063] The oscillator 11 and receiver 12 in Case 1 and the oscillator and receiver used in Case 2 are all installed on the same ground improvement body specimen 20. The separation distance D2 between the oscillator 11 and receiver 12 in Case 1 and the separation distance between the oscillator and receiver used in Case 2 are set to 10 cm and 17 cm, respectively, in order to prevent any influence on the experimental results due to the configuration installed on the same ground improvement body specimen 20. The measurement positions for the velocity V2 of the shear wave W4 in Case 1 and Case 2 were set to the same depth in the original position of the ground improvement body specimen 20, and in the vicinity thereof.

[0064] In either case, known bender elements are used for the oscillator 11 and receiver 12. In either case, the oscillator 11 is connected to an oscillator (not shown) that corresponds to a load such as an earthquake force, and generates shear waves of a predetermined magnitude from the oscillator.

[0065] The shear wave W4 measured in Case 1 had a propagation time T1 of 144 μs and a velocity V2 of 694 m / s, while the shear wave W4 measured in Case 2 had a propagation time T1 of 254 μs and a velocity V2 of 699 m / s. From the above results, the shear wave velocity measurement sensor 1 can measure the velocity V2 of the shear wave W4 with the same level of accuracy as the conventional method. Furthermore, as shown in Figure 4, when comparing the time progression of the waveform of the received wave W2 received by the receiving unit 12 in Cases 1 and 2, the point in time at which the received wave W2 is received is clear in both cases, so the propagation time T1 of the shear wave W4 can be easily determined, just like the conventional method.

[0066] Next, the effects of the shear wave velocity measuring sensor 1 and the shear wave velocity measuring system 3 according to this embodiment will be described with reference to the drawings.

[0067] The shear wave velocity measurement sensor 1 includes an oscillator 11, a receiver 12, and a joint 13, and is embedded in a ground improvement body 2 consisting of a wall body 21. The joint 13 is made of a resin material such that the velocity V1 of the shear wave W3 propagating through the joint 13 is approximately 350 m / s, which is slower than the velocity V2 of the shear wave W4 of 400 m / s in a typical cement-based ground improvement body 2. The joint 13 has sufficient rigidity to prevent deformation when installed in the ground improvement body 2.

[0068] With the above configuration, shear wave velocity measurement sensor 1 can fix the separation distance D2 between oscillator 11 and receiver 12 using joint 13, accurately maintaining the propagation distance of shear wave W4 between oscillator 11 and receiver 12 and accurately transmitting and receiving oscillator wave W1 and receiver wave W2. Because the velocity V1 of shear wave W3 propagating through joint 13 is slower than the velocity V2 of shear wave W4 propagating through ground improvement body 2, shear wave velocity measurement sensor 1 can easily distinguish between the oscillation time at oscillator 11 and the reception time at receiver 12 of the two types of shear waves. As described above, shear wave velocity measurement sensor 1 can accurately measure the velocity V2 of shear wave W4 propagating through ground improvement body 2.

[0069] The shear wave velocity measurement sensor 1 can be easily installed without reducing the rigidity of the ground improvement body 2 because the joint material 13 has enough rigidity to prevent deformation when installed in the ground improvement body 2.

[0070] The shear wave velocity measuring sensor 1 is formed with a simple configuration in which the emitting part 11 and the receiving part 12 are integrated into the joint material 13, thereby improving construction efficiency and reducing the effort required for installation in the ground improvement body 2.

[0071] The shear wave velocity measurement sensor 1 is installed in the ground improvement body 2, eliminating the need to drill additional holes or other holes for installation in the ground. This reduces damage to the ground improvement body 2, such as loss of the body, and prevents a decrease in the rigidity of the ground improvement body 2, thereby improving construction efficiency.

[0072] The joint member 13 is formed so that the propagation distance D1 of the shear wave W3 propagating through the joint member 13 is longer than the separation distance D2 between the oscillation unit 11 and the reception unit 12.

[0073] With the above configuration, the shear wave velocity measurement sensor 1 can easily determine the propagation time T1 of the shear wave W4 propagating through the ground improvement body 2. By easily and accurately measuring the propagation time T1 of the shear wave W4, the velocity V2 of the shear wave W4 can be calculated and measured with higher precision.

[0074] The joint 13 includes a first extension portion 131, a second extension portion 132 extending downward in the Z direction from one end 131a of the first extension portion 131, and a third extension portion 133 extending parallel to the second extension portion 132 from the other end 131b of the first extension portion 131. The oscillation portion 11 protrudes from an inner surface 132b of a tip portion 132a of the second extension portion 132 toward the third extension portion 133. The vibration receiving portion 12 protrudes from an inner surface 133b of a tip portion 133a of the third extension portion 133 toward the second extension portion 132.

[0075] With the above-described configuration, the shear wave velocity measurement sensor 1 has the joints 13 formed from multiple straight lines, which allows the propagation distance D1 of the shear wave W3 in the joints 13 to be reliably longer than the separation distance D2 between the oscillator 11 and receiver 12, with a simpler configuration. The shear wave velocity measurement sensor 1 has the joints 13 formed from a simple, straight-line outer shape, which improves installation efficiency.

[0076] The joint 13 is made of a resin material. With the above-described configuration, the shear wave velocity measurement sensor 1 can easily process the joint 13 having a portion that bends at approximately 90 degrees, thereby improving the workability of the joint 13.

[0077] The Y-direction thickness D3 and Z-direction thickness D4 of the first extension portion 131 of the joint member 13, and the X-direction thickness D5 and Y-direction thickness D6 of the second extension portion 132 and the third extension portion 133 are all formed to be 10 mm or less.

[0078] With the above configuration, the shear wave velocity measurement sensor 1 can be formed so that the cross section in the extension direction of each extension portion of the joint 13 takes into consideration the effect on the rigidity of the ground improvement body 2 when it is installed in the ground improvement body 2. This makes it possible to more reliably prevent a decrease in the rigidity of the ground improvement body 2 due to the installation of the shear wave velocity measurement sensor 1 in the ground improvement body 2. Because the maximum thickness of the joint 13 in the X and Y directions is specified to be 10 mm or less, the shear wave velocity measurement sensor 1 can be a simple and compact sensor, further reducing the effort required for installation in the ground improvement body 2.

[0079] The shear wave velocity measurement system 3 includes a shear wave velocity measurement sensor 1, and a processing unit 31a and a waveform generator 31b provided outside the ground improvement body 2. The processing unit 31a measures the velocity V2 of the shear wave W4 from data on the current of a predetermined frequency passed from the waveform generator 31b to the oscillator 11 and waveform data of the received wave W2 received by the receiver 12, and calculates the residual strain γ1 based on the measured velocity V2 of the shear wave W4.

[0080] With the above configuration, the shear wave velocity measurement system 3 can use the shear wave velocity measurement sensor 1 to measure with high accuracy the velocity V2 of the shear wave W4 propagating through the ground improvement body 2, and can calculate with high accuracy the residual strain γ1 of the ground improvement body 2. The shear wave velocity measurement system 3 can detect damage to the ground improvement body 2 from the calculated residual strain γ1 of the ground improvement body 2, and can determine whether or not the ground improvement body 2 needs to be continued to be used.

[0081] The shear wave velocity measuring system 3 is configured so that the joint material 13 does not affect the rigidity of the ground improvement body 2, and the processing unit 31a and waveform generator 31b are located outside the ground improvement body 2, so it can be a mechanism that does not reduce the rigidity of the ground improvement body 2.

[0082] In the shear wave velocity measurement system 3, the separation distance D2 between the oscillator 11 and receiver 12 is fixed by the joint 13, and the oscillator 11 and receiver 12 can oscillate and receive in multiple directions, including horizontal, vertical, and diagonal directions. Therefore, the damage state of the ground improvement body 2 can be calculated accurately at multiple locations and in multiple directions.

[0083] The shear wave velocity measurement system 3 includes a first connection cable 32 and a second connection cable 33. The first connection cable 32 is disposed in a first hollow portion 132c formed in the second extension portion 132, and is connected to the oscillator 11 and the waveform generator 31b. The second connection cable 33 is disposed in a second hollow portion 133c formed in the third extension portion 133, and is connected to the receiver 12 and the processor 31a.

[0084] With the above configuration, the shear wave velocity measurement system 3 can place the first connection cable 32 and the second connection cable 33 in the joint 13 by using the first hollow portion 132c and the second hollow portion 133c. Therefore, the first connection cable 32 and the second connection cable 33 can be easily protected from the external environment.

[0085] The first hollow portion 132c and the second hollow portion 133c are filled with a filler 135 without leaving any gaps.

[0086] With the above configuration, the shear wave velocity measuring system 3 can suppress vibration of the first connection cable 32 and the second connection cable 33 within the first hollow portion 132c and the second hollow portion 133c, thereby preventing deterioration or breakage of the first connection cable 32 and the second connection cable 33 due to vibration.

[0087] The above describes embodiments of the shear wave velocity measurement sensor and shear wave velocity measurement system according to the present invention, but the present invention is not limited to the above embodiments and can be modified as appropriate within the scope of the spirit of the present invention.

[0088] For example, in the above embodiment, the oscillator 11 and the waveform generating device 31b, and the receiver 12 and the processing unit 31a are connected by the first connection cable 32 and the second connection cable 33, respectively, but the connections by the first connection cable 32 and the second connection cable 33 may be omitted, and the oscillator 11 and the waveform generating device 31b, and the receiver 12 and the processing unit 31a may be connected by wireless communication. [Explanation of symbols]

[0089] 1. Shear wave velocity measurement sensor 2 Ground improvement body 11 Oscillator 12 Receiving section 13 Joint material 21 Wall 31a Processing section 31b Waveform Generator 32 First connecting cable 33 Second connection cable 131 First extension section 131a one end 131b other end 132 Second extension 132a Tip 132c First hollow part 133 Third extension section 133a Tip 133c Second hollow part 135 Filling material

Claims

1. It is provided in a ground improvement body consisting of a grid-like wall in plan view constructed in the ground, an oscillator that generates a shear wave; a receiving unit that receives the shear wave oscillated from the oscillating unit; A joint member that connects the oscillation unit and the receiving unit; Equipped with The speed of the shear wave propagating through the joint material is slower than the speed of the shear wave propagating through the ground improvement body, The joint material includes a shear wave velocity measurement sensor having rigidity that does not deform when installed in the ground improvement body; A processing unit provided outside the ground improvement body, which measures the shear wave velocity and calculates the residual strain based on the measured shear wave velocity; A waveform generating device provided outside the ground improvement body and oscillating a shear wave from the oscillator; Equipped with The processing unit measures the velocity of the shear wave oscillated from the oscillator, propagated through the ground improvement body, and received by the receiver, and calculates the residual strain of the ground improvement body; a first connection cable that connects the oscillator and the waveform generator so that the oscillator can oscillate; A second connection cable that connects the receiving unit and the processing unit so that the residual strain of the ground improvement body can be measured; Equipped with the joint member is formed with a first hollow portion through which the first connection cable is inserted and a second hollow portion through which the second connection cable is inserted, The first hollow portion and the second hollow portion are filled with a filler. Shear wave velocity measurement system.

2. The propagation distance of the shear wave in the joint is longer than the separation distance between the oscillator and the receiver. The shear wave velocity measurement system of claim 1 .

3. The joint member includes a first extension portion extending in one direction, a second extension portion extending in another direction from one end of the first extension portion, and a third extension portion extending from the other end of the first extension portion in parallel to the second extension portion, the oscillation portion protrudes from a tip end of the second extension portion toward the third extension portion, The vibration receiving portion protrudes from the tip end of the third extension portion toward the second extension portion. The shear wave velocity measurement system according to claim 1 or 2.

4. The joint material is formed from a resin.

4. A shear wave velocity measurement system according to claim 1.

5. The maximum thickness in a direction perpendicular to the extension direction of each extension portion of the joint material is 10 mm or less.

5. A shear wave velocity measurement system according to any one of claims 1 to 4.

6. The shear wave velocity measurement sensor is provided in plurality in the ground improvement body. The shear wave velocity measurement system of claim 1 .

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