KR100745036B1 - In-hole seismic method for measuring dynamic stiffness of subsurface materials - Google Patents

Abstract

An in-hole seismic wave test method for measuring the stiffness of the ground is provided to let a filed technician make an in-hole seismic wave test easily by installing an oscillator and a sensor in one borehole. The in-hole seismic wave test method for measuring the stiffness of the ground comprises the steps of: forming one borehole(60) on the ground; connecting an oscillator(10) and a sensor(20) connected with a controller(50) and a dynamic signal analyzer(52) electrically using a connection member(40) and inserting to a measurement spot of the borehole in order; adhering the oscillator and the sensor inserted to the measurement spot of the borehole to a cavity wall of the borehole using an adhesion member(30) operated by the controller; operating a working member and a trigger arm(14) installed to the inside of the oscillator using electric signals of the controller, hitting the cavity wall of the borehole using an impact pestle(16) operated by the trigger arm and setting up a vibration; sensing a generation spot of the vibration using a sensor installed to the oscillator and sensing a destination spot of the vibration spread vertically along a stratum using the sensor; and storing the vibration signals sensed from the oscillator and the sensor in the dynamic signal analyzer and measuring.

Description

IN-HOLE SEISMIC METHOD FOR MEASURING DYNAMIC STIFFNESS OF SUBSURFACE MATERIALS}

1 is a view showing a test apparatus provided for the in-hole seismic test according to a preferred embodiment of the present invention,

2 to 5 are views showing the in-hole seismic test process according to a preferred embodiment of the present invention,

6a to 6c is a view showing the results calculated by performing the in-hole seismic test in the soil layer according to the present invention,

7a to 7c is a view showing the result calculated by performing the in-hole seismic test in the rock according to the invention, and

8 and 9 are views showing a field acoustic wave test process according to the prior art.

<Description of Symbols for Major Parts of Drawings>

10: oscillator 20: detector

30: contact member 40: connection member

50: control device 52: dynamic signal analyzer

60: detection hole

The present invention relates to an in-hole seismic test method for measuring the stiffness of the ground, and more specifically, it can be easily used by general technicians at low cost by supplementing the cross-hole test and the down-hole test, which are field acoustic wave tests, oscillators and detectors. It is related to the in-hole seismic test method for measuring the stiffness of the ground that can be installed in one detection hole to measure the direct shear wave propagated vertically along the strata.

In general, the seismic analysis of the ground structure requires precise measurement of the dynamic properties of the ground. This dynamic property consists of shear modulus and damping ratio curves. This curve consists of the maximum shear strain coefficient of the small strain, the minimum damping ratio, and the nonlinear portion according to the strain.

In particular, the maximum shear strain coefficient is measured by the field acoustic wave test, and the double crosshole test and the downhole test are the most widely used.

First, as shown in Figure 8, the cross-hole test is a field test method that can measure the P wave speed and S wave speed of the ground for each depth to install two or more detection holes 200 and one side oscillator 100 Install and the remaining detection holes 200 to the same depth to install the detector 110. In this case, by measuring the time the vibration generated in the oscillator 100 passes through the ground to reach the detector 110, it is possible to obtain the seismic velocity for each depth, and also to obtain the shear strain coefficient and Poisson's ratio (POISSON'S RATIO) . And the wave propagation path is constant, and the oscillator 100 and the detector 110 are located at the same position, it is possible to find out the detailed strata structure.

However, the cross-hole test is the most accurate measurement method, but the cost is expensive because two or more detection holes (200) are required, and small enough to be installed in the detection holes (diameter 75 mm) 200 can produce an efficient impact energy. There is a need for a good performance oscillator 100. In addition, this method is being avoided due to the cumbersomeness and difficulty of installing the casing and adding grouting to secure close contact with the surrounding ground.

As shown in FIG. 9, the downhole test is one of field acoustic wave tests that have been recently performed to measure dynamic physical properties (compression wave speed and shear wave speed) of fat, and the oscillator 100 is installed on the surface of the sensor. 110 is installed at the planned point depth within the detection hole (200). When the oscillator 100 is subjected to an impact, it causes vibration. When the impact is applied in the vertical direction, the compression wave component is generated, and when the impact is applied in the horizontal direction, vibrations rich in the shear wave SH component are generated.

However, since the downhole test installs one detection hole 200, the deeper the position of the detector 110, the smaller the signal-to-noise ratio (S / N RATIO) is, so that it is difficult to obtain high-quality data, and the stiffness is high. It is difficult to apply in high contrast ground (soil and rock). In addition, since only a rough stiffness column is obtained compared to the crosshole test result, the test is easy and economical, but there is a limit of utilization.

The present invention has been made in order to solve the problems of the prior art as described above, the technical problem of the present invention can be easily used by the general technician at a low cost by supplementing the advantages and disadvantages of the cross-hole type test and downhole test In addition, the present invention provides a means for measuring a direct shear wave propagated vertically along the ground by installing an oscillator and a detector in a single detection hole.

The present invention for solving the above technical problem,

Forming one detection hole in the ground; Connecting an oscillator and a sensor electrically connected to the control device and the dynamic signal analyzer provided on the ground, respectively, to the measuring point of the detection hole sequentially from the oscillator; Bringing the oscillator and the sensor inserted into the detection hole into close contact with the empty wall of the detection hole by using an adhesion member operated by the control device; Operating an operating member and a trigger ball installed in the oscillator through an electrical signal of the control device, and generating vibration by striking the empty wall of the detection hole with an impact ball operated by the trigger ball; Detecting a time point of occurrence of vibration by a sensor installed in the oscillator, and detecting a time point of arrival of vibration propagated vertically along the stratum by oscillation of the oscillator by a sensor installed in the detector; And storing and measuring the vibration signal sensed by the oscillator and the detector in a dynamic signal analyzer provided on the ground, and measuring the stiffness of the ground.

Hereinafter, the in-hole seismic test method for measuring the stiffness of the ground according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 to 5 are views illustrating an in-hole seismic test process according to a preferred embodiment of the present invention. FIG. 2 illustrates a state in which one detection hole is formed in the ground, and FIG. 3 illustrates an in-hole at a measurement point of the detection hole. The state of inserting the seismic test device is shown, and FIG. 4 shows a state in which the in-hole seismic test device inserted into the measuring point of the detection hole is in close contact with the empty wall of the detection hole, and in FIG. The state of generating vibration with the in-hole seismic test device is shown.

2 to 5, the in-hole seismic test method for measuring the stiffness of the ground according to a preferred embodiment of the present invention, forming one detection hole 60 in the ground, the control device provided on the ground ( 50) and the oscillator 10 and the detector 20 electrically connected to the dynamic signal analyzer 52 and the detector 20, respectively, are connected to the connecting member 40 and sequentially inserted into the measuring points of the detection hole 60 from the oscillator 10. Step of the step of contacting the oscillator 10 and the detector 20 inserted into the detection hole (60) and the detector 20 in close contact with the empty wall of the detection hole 60 by using the contact member 30 operated by the control device, The operation member 12 and the trigger ball 14 installed inside the oscillator 10 are operated through the electrical signal of the control device 50, and the detection is performed by the impact ball 16 operated by the trigger ball 14. Step to generate vibration by hitting the ball wall of the ball 60, installed in the oscillator 10 Detects the timing of the occurrence of vibration with the sensor 18, and detecting the time of arrival of the vibration propagated vertically along the stratum with the sensor 24 installed in the detector 20, and the oscillator 10 and the detector And storing the measured vibration signal in the dynamic signal analyzer 52 provided on the ground.

In order to perform the in-hole seismic test according to the preferred embodiment of the present invention as described above, as shown in Figure 1, the in-hole seismic test device consisting of the oscillator 10, the sensor 20, and the connecting member 40 It is provided.

At this time, the oscillator 10 and the detector 20 are electrically connected to the control device 50 and the dynamic signal analyzer 52 provided on the ground, the oscillator 10 and the detector 20 by the control device 50 The operation of the control is controlled, and the vibration signal detected by the oscillator 10 and the detector 20 is stored and measured in the dynamic signal analyzer 52.

The oscillator 10 is for generating elastic wave energy, that is, vibration, and is provided with a cylindrical body 11 having a predetermined length. An installation space 11A is formed inside the body 11. An operating member 12 is provided below the installation space 11A of the body 11. This operating member 12 is made of a servo motor to control the trigger ball 14 to be described later by the control device 50 in the correct position and speed. In the installation space 11A positioned at the upper portion of the operating member 12, a trigger ball 14 is formed to be rotatable by a hinge so that the locking projections 14A and 14B protrude from the corresponding positions of the outer periphery, respectively. . This trigger ball 14 is connected via the operating member 12 and the bevel gear (not shown). The impact ball 16 is rotatably installed in the installation space 11A so as to be located above the trigger ball 14 by a hinge in a vertical state. A catching portion 16A is formed at a lower end of the impact ball 16, and a hitting portion 16B is formed to protrude at an upper end thereof, and a catching protrusion 14A formed at both outer peripheries of the trigger ball 16 at the catching portion 16A. The locking projection 14A of any one of 14B is engaged to contact. One side of the impact ball 16 is provided with an elastic member 16C for elastic support to always maintain the vertical state. The impact ball 16 hits the ball wall of the detection hole 60 with the striking part 16B by the rotation of the trigger ball 14 to generate vibration. A detection sensor 18 is installed at the upper portion of the installation space 11A to accurately detect the time point of the vibration generated by the impact ball 16. This sensor 18 is made of an accelerometer.

And the outer periphery of the body 11 of the oscillator 10 is formed by protruding portion 11B protrudes in a position corresponding to the contact member 30 to be described later. At this time, the protrusion 11B is formed to protrude on the outer periphery of the body 11 to be located in front of the impact portion 16B of the impact ball 16. The protrusion 11B is in close contact with the vacant wall of the detection hole 60 when the oscillator 10 is in close contact with the vacant wall of the detection hole 60 by the contact member 30. To make it possible.

The body 11 of the oscillator 10 configured as described above is made of aluminum to prevent corrosion when measuring the shear wave velocity under the groundwater level, and the outer periphery of the epoxy resin to prevent the penetration of water by water pressure. Using the waterproof coating layer 19 is molded.

On the other hand, the sensor 20 is to detect the vibration generated in the oscillator 10 and transmitted through the ground layer, a cylindrical body 22 having a predetermined length is provided. The inside of the body 22 is provided with a sensor 24 for accurately detecting the arrival time of the vibration transmitted through the excitation layer of the oscillator 10. This sensor 24 is made of a speedometer.

And the outer periphery of the body 22 of the sensor 20 is formed by projecting the protrusions 26 to a position corresponding to the contact member 30 to be described later. At this time, the protrusion 26 is formed to protrude on the outer periphery of the body 22 to be located in front of the sensor (24). The protruding portion 26 is such that when the sensor 20 is in close contact with the empty wall of the detection hole 60 by the contact member 30, the sensor portion of the detector 60 is concentrated in close contact with the empty wall of the detection hole 60. To do this.

Like the oscillator 10, the body 22 of the sensor 20 configured as described above is made of aluminum to prevent the influence of the surrounding magnetic field and to prevent corrosion when measuring the shear wave velocity under the groundwater level. In order to prevent penetration of water by water pressure, the waterproof coating layer 28 is formed by using an epoxy resin.

On the other hand, the oscillator 10 and the detector 20 is provided with a close contact member 30 for bringing the oscillator 10 and the detector 20 in close contact with the empty wall of the detection hole 60 when measuring the shear wave speed, such a close contact member 30 is a close contact with the oscillator 10 and the detector 20 is provided with a contact bar 32, which is provided to be movable sideways on one surface of the body (11, 22) so as to be in close contact with the vacant wall of the detection hole 60, and It is provided at both ends of the body (11, 22) so as to be connected through the bar (32) and the rack (33A) and pinion (33B), respectively, the operation member for contacting the close bar 32 to the ball wall of the detection hole 60 It consists of 34. At this time, the rack 33A is formed on the contact bar 32, the pinion 33B is formed on the actuating member 34, the actuating member 34 is made of a known servo motor.

On the other hand, the connection member 40 is provided to connect the oscillator 10 and the detector to block the vibration during the excitation of the oscillator 10 does not directly reach the detector 20, the oscillator 10 and the detector 20 ) Has a certain length so as to maintain a constant distance, both ends are connected to the oscillator 10 and the detector 20, respectively.

The connection member 40 is characterized by measuring the arrival time of the wave propagating up and down the detection hole 60 by using the oscillator 10 and the sensor 20, rather than the rigidity of the ground of the connection member 40 If the stiffness is large, the vibration transmitted to the sensor 20 through the connecting member 40 is faster than the vibration transmitted to the sensor 20 through the ground layer, and for this reason, the vibration transmitted through the ground layer causes the connection member 40 to move. Buried in the vibration transmitted through it becomes very difficult to accurately identify the starting point of the vibration transmitted through the strata by the sensor 18 of the oscillator 10 it is impossible to obtain the dynamic properties of the ground.

Therefore, the connecting member 40 has a very small stiffness of all known materials that can be used as the connecting member, including a chain, an anti-vibration rubber hose, and a fiber rope, and the speed transmitted to the detector 20 during the excitation of the oscillator 10 is the most. It is preferable that the silicon vacuum hose is formed by compressing the silicon so that it can be applied not only to rock but also to soil ground.

2 to 5 will be described in more detail the in-hole seismic test process for measuring the stiffness of the ground in accordance with a preferred embodiment of the present invention.

First, as illustrated in FIG. 2, one detection hole 60 is formed in the ground. At this time, the detection hole 60 is drilled to the depth of the ground through a perforator in the ground to be measured is formed in a porous state in which the casing is not installed.

3, the oscillator 10 and the detector 20 electrically connected to the control device 50 and the dynamic signal analyzer 52 provided on the ground, respectively, are connected to the connection member 40. By inserting the oscillator 10, the connecting member 40 and the detector 20 in the order of measuring points of the detection hole (60).

Then, as shown in Figure 4, after inserting the oscillator 10 and the detector 20 at the measuring point of the detection hole 60, the oscillator 10 and the oscillator 10 by the control device 50 provided on the ground; The oscillator 10 and the detector 20 are brought into close contact with the empty wall of the detection hole 60 by operating the contact member 30 provided in the detector 20.

That is, the operating member 34 provided in the oscillator 10 and the bodies 11 and 22 of the detector 20 is operated in accordance with the electrical signal of the control device 50, and the operating member 34 and the rack 33A are operated. ) And the close contact bar 32 connected by the pinion 33B are moved laterally in contact with the bodies 11 and 22 to be in close contact with the empty wall of the detection hole 60, whereby the oscillator 10 and the detector 20 ) Is strongly adhered to the ball wall of the detection hole 60 through the mechanical adhesion of the contact member 30 to maximize the impact energy due to the vibration of the oscillator (10). At this time, the protrusions 11B and 26 formed on the outer circumferences of the oscillator 10 and the bodies 11 and 22 of the detector 20 are concentrated on the air walls of the detection holes 60.

Next, as shown in FIG. 5, the operation member 12 and the trigger ball 14 installed in the oscillator 10 are operated through the electrical signal of the control device 50 to the impact ball 16. Vibration is generated by hitting the empty wall of the detection hole (60).

That is, the trigger ball 14 connected to the operation member 12 and the bevel gear is rotated according to the electrical signal of the control device 50, and any of the protrusions 14A and 14B formed on both outer peripheries of the trigger ball 14 is rotated. One of the engaging projection 14A and the engaging portion 16A formed at the lower end is engaged so that the impact ball 16 installed perpendicular to the installation space 11A is retracted toward the elastic member 16C around the hinge to be elastic. When the member 16C is contracted and at the same time the latching state of the engaging protrusion 14A and the engaging portion 16A is released, the elastic member 16C that has been contracted is restored and rapidly moves in the opposite direction in which the impact ball 16 is flipped. The oscillator 10 can be easily oscillated through the control device 50 because the oscillation is generated by striking the ball wall of the detection hole 60 with the striking part 16B while being rotated. Then, after the impact ball 16 is hit, the trigger ball 14 is rotated at the correct position and speed by the operation member 12 so that the other engaging protrusion 14B is caught to reload the impact ball 16. Since it contacts and locks to 16A, the repeatability of the oscillator 10 is excellent.

Then, when the oscillation of the oscillator 10 is detected through the detection sensor 18 installed in the body 11, the occurrence point of the vibration, the vibration propagated vertically through the strata is the body 22 of the detector 20 Detect with a sensor 24 installed in the).

At this time, the connecting member 40 connecting the oscillator 10 and the sensor 20 is the sensor 20 through the connecting member 40 rather than the vibration transmitted to the detector 20 through the excitation layer of the oscillator 10. The vibration transmitted through the strata is faster than the vibration transmitted through the strata, so that the speed of the vibration transmitted directly to the slower is lowered, so that the vibration transmitted through the strata is transmitted to the vibrations transmitted through the coupling members 40. It can be applied to precisely measure the shear wave velocity of the ground even in rock and loose soil layers. The connecting member 40 is preferably made of a silicon vacuum hose formed by compressing silicon so that the rigidity is very small so that it can be applied to rock and soil layers.

Then, the vibration signal detected by the oscillator 10 and the sensor 20 is stored in the dynamic signal analyzer 52 provided on the ground and measured. At this time, the dynamic signal analyzer 52 measures the occurrence time of the vibration stored from the oscillator 10 and the detection sensors 18 and 24 of the sensor 20 and the arrival time of the vibration transmitted through the ground, thereby measuring the shear wave velocity of the ground. It can increase the reliability of the results when measuring.

Herein, analyzing the information stored from the oscillator 10 and the sensing sensors 18 and 24 of the detector 20 through the dynamic signal analyzer 52 is a well-known technique that can be easily carried out by those skilled in the art. Will be omitted.

Then, when the measurement of the shear wave velocity for the corresponding measuring point of the detection hole 60 is completed, the operating member provided in the oscillator 10 and the bodies 11 and 22 of the detector 20 by the control device 50. (34) to operate the close contact bar 32, which was in close contact with the ball wall of the detection hole 60 to move toward the body (11, 22) to release the close contact between the oscillator 10 and the sensor 20, and Through the same series of processes to measure the shear wave velocity for each depth of the detection hole (60).

On the other hand, the body (11, 22) of the oscillator 10 and the sensor 20 is an in-hole seismic test under the groundwater level by preventing the penetration of water by corrosion and water pressure through the aluminum material and waterproof coating layers (19, 28) The shear wave velocity can be easily measured.

On the other hand, Figure 6a to 6c shows the results calculated by performing the in-hole seismic test according to the present invention in the soil layer.

For the in-hole seismic test according to the present invention, a test hole was excavated to a depth of 2.8 m using a power auger at a granite weathered site in Kyunghee University. The in-hole seismic test apparatus connected the oscillator 10 and the sensor 20 to the connecting member 40 at 1 m intervals, and the casing was not installed to exclude the influence of the casing.

FIG. 6A is a shear wave signal obtained in an in-hole seismic test, and shear wave initialization (point of arrival) is indicated by an arrow in each signal. The starting point of the shear wave is the point at which the high frequency compressed wave ends and the low energy wave starts.

In order to verify the in-hole seismic test, the hole was further excavated with a spacing of 2.68 m and a cross-hole test was performed. The oscillator 10 and the sensor 20 used the in-hole seismic test apparatus used in the in-hole seismic test as it is. 6B is a shear wave signal obtained in a crosshole test.

6C is a shear wave velocity distribution obtained from the shear wave arrival times of the in-hole seismic test and the cross-hole test described above.

As a result, the shear wave velocity difference of the in-hole seismic test is within 8%, which is in good agreement with the cross-hole test result, and the excellent shear wave signal can be easily obtained for the initial wave discrimination. The difference is that the shear wave propagation direction is different between the two techniques (cross holes are vertical in-holes and vertical directions), and it is considered that the difference between the anisotropy of soil layer and the method of seeding.

7A to 7C show the results calculated by performing the in-hole seismic test in the rock according to the present invention.

For the in-hole seismic test according to the present invention, Seomjin River Dam in Jeongeup, Jeollabuk-do and Doam Dam in Pyeongchang-gun, Gangwon-do were selected. In both sites, the size of the detection hole is NX, and the depth of Seomjin River Dam is 14m and Doam Dam is 12m. In order to perform the in-hole seismic test, the distance between the oscillator and the detector was 1 m, the connecting member was inserted and inserted into the detection hole, and the test was performed at 0.5 m intervals, and the signal acquisition time was 7 msec.

7A is a result of in-hole seismic tests for each depth performed in Seomjin River Dam and Doam Dam. The initial measurement time was 7msec, but the length of the record length was extended to 2msec to clearly distinguish the first wave of the shear wave from the detector. 6A represents a trigger signal of an oscillator and all signals below are shear wave signals of a detector for each depth of a detection hole. The point of arrival of the shear wave is shown in a true table for easy identification.

Fig. 7B is a shear wave velocity column diagram drawn by calculating the shear wave arrival time obtained from this signal as the shear wave velocity. These two sites proved to be high quality hard rock with a shear wave velocity distribution of 2,200 to 3,000 m / sec.

In order to confirm the reliability of the in-hole seismic test performed in Seomjin River Dam and Doam Dam, the cross-hole test and the down-hole test were performed in the same site rock where the in-hole seismic test was performed.

In the crosshole test, the instantaneous spacing between the detection hole and the detection hole was 2.1 m at the Seomjin River Dam and the foundation, and the oscillator and detector used the in-hole seismic test device used in the in-hole seismic test. The instantaneous spacing was 2.5 m. The oscillator and detector also used the in-hole seismic tester used in the in-hole seismic test.

In addition, the downhole test was performed with the distance between the detection hole and the oscillator at 2.5 m in both sites. Since downhole tests generally use longer propagation paths than crosshole tests, they are less reliable and cause seismic waves at the surface, making measurements near the surface relatively inapplicable at deeper depths.

The shear wave velocity columnarity of the result of the crosshole test and the downhole test as shown in the in-hole seismic test is shown in FIG. 6C.

As a result, as shown in FIG. 7C, the cross-hole result is very close to the in-hole seismic test result, which supports the reliability of the in-hole seismic test. The results of the downhole test show that the signals of the deep measurements are difficult to identify the shear wave, so that the shear wave velocity cannot be obtained or an incorrect value is obtained, which proves the superiority of the in-hole seismic test.

As described above, the in-hole seismic test method for measuring the stiffness of the ground according to the present invention is improved by the existing field seismic test can be easily used by technicians in the field when measuring the shear wave velocity of the ground, using one detection hole It is possible to reduce the drilling cost, and can be applied to rock and loose soil ground, so that the effect can be widely used in the field.

The present invention has been described above by way of example, but the present invention is not limited to the above-described embodiments, and those skilled in the art without departing from the gist of the present invention claimed in the claims. Anyone can make a variety of variations.

Claims (1)

Forming one detection hole in the ground; Connecting an oscillator and a sensor electrically connected to the control device and the dynamic signal analyzer provided on the ground, respectively, to the measuring point of the detection hole sequentially from the oscillator; Bringing the oscillator and the sensor inserted into the detection hole into close contact with the empty wall of the detection hole by using an adhesion member operated by the control device; Operating an operating member and a trigger ball installed in the oscillator through an electrical signal of the control device, and generating vibration by striking the empty wall of the detection hole with an impact ball operated by the trigger ball; Detecting a time point of occurrence of vibration with a sensor installed in the oscillator and detecting a time point of arrival of vibration propagated vertically along the stratum with a sensor installed in the detector; And Storing and measuring the vibration signal detected by the oscillator and the detector in a dynamic signal analyzer provided on the ground; In-hole elastic plate test method for measuring the stiffness of the ground, characterized in that it comprises a.

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