JP6944899B2 - Ground structure estimation method - Google Patents

Description

The present invention relates to a technique for relatively reducing the processing load of the ground structure estimation process.

There is a surface wave exploration method as a ground exploration method, but there is a problem that the exploration accuracy decreases as the ground becomes deeper. Elastic wave tomography is a method that enables exploration of deep ground. Patent Document 1 proposes a method for exploring a ground structure by elastic wave tomography.

Japanese Unexamined Patent Publication No. 2007-298369

Conventional elastic wave tomography has a large processing load for analyzing a received wave to estimate the ground structure.

In view of the above background, a means for reducing the processing load in estimating the ground structure is provided.

In order to solve the above-mentioned problems, the present invention causes vibrations at the oscillation points of the ground surface with respect to each of the oscillation points of the plurality of ground surfaces having different horizontal positions, and the present invention causes a plurality of ground surfaces having different horizontal positions from each other. With respect to the process of receiving the surface wave of the vibration at each of the vibration receiving points of the above and each of the plurality of underground oscillation points having different positions in the vertical direction, vibration is generated at the ground oscillation points, and the plurality of grounds are subjected to vibration. A step of receiving a P wave of the vibration at each of a plurality of underground vibration receiving points having different positions in the horizontal direction from the oscillation point in the ground and having different vertical positions from each other. Based on the received surface wave, the step of estimating the S wave velocity structure of the ground by the surface wave exploration method, and the initial parameters are set based on the estimated S wave velocity structure, and the elasticity is based on the received P wave. A ground structure estimation method including a step of estimating a P-wave velocity structure of the ground by a wave tomography method is provided as a first aspect.

According to the ground structure estimation method of the first aspect, the processing load in estimating the ground structure is reduced.

The second aspect of the ground structure estimation method of the first aspect includes a step of estimating at least one of the distribution of the shear modulus of the ground and the distribution of Young's modulus based on the estimated P wave velocity structure. May be adopted as.

According to the ground structure estimation method of the second aspect, more detailed ground structure estimation is performed.

In the ground structure estimation method of the first or second aspect, the configuration that the vibration generated in the step of receiving the P wave is generated by penetrating the structural member into the ground is adopted as the third aspect. May be good.

According to the ground structure estimation method of the third aspect, the ground structure is estimated as the structural member penetrates into the ground.

In the ground structure estimation method of the third aspect, a configuration including a step of estimating the hardness of the ground based on the state of penetration of the structural member into the ground may be adopted as the fourth aspect.

According to the ground structure estimation method of the fourth aspect, more detailed ground structure estimation is performed along with the work of penetrating the structural member into the ground.

In the ground structure estimation method of the fourth aspect, the configuration in which the structural member is a sampler for a standard penetration test and includes a step of performing a standard penetration test using the sampler for the standard penetration test is adopted as the fifth aspect. May be done.

According to the ground structure estimation method of the fifth aspect, the ground structure is estimated in accordance with the standard penetration test.

The figure which showed the structure and arrangement of the ground structure estimation system which concerns on one Embodiment. The figure which showed the functional structure of the ground structure estimation apparatus which concerns on one Embodiment. The figure which illustrated the procedure of the ground structure estimation method which concerns on one Embodiment.

[Embodiment]
The ground structure estimation method according to the embodiment of the present invention will be described below. FIG. 1 is a diagram showing the configuration and arrangement of the ground structure estimation system 1 used for implementing the ground structure estimation method according to the embodiment.

First, the ground structure estimation system 1 has a plurality of receiving vibrations arranged at the receiving points of a plurality of ground surfaces G having different horizontal positions between points A and B of the ground surface G having different horizontal positions. A vessel 11 is provided. The distance between the points A and B is preferably about 30 to 50 meters, but is not limited to this.

The vibration receiver 11 receives vibration generated at an oscillation point on the ground surface G by an oscillator 13 described later. More specifically, the vibration receiver 11 continuously measures the magnitude of the received vibration and continuously outputs data representing the measurement result. The data continuously output from the vibration receiver 11 is stored in the ground structure estimation device 15 (described later) as waveform data representing a change in the magnitude of vibration with time, that is, a waveform. As the vibration receiver 11, a ground vibration receiver (geophone) is used if the ground surface G is exposed, and an underwater receiver (hydrophone) is used if the ground surface G is underwater. It is desirable that the plurality of receivers 11 are arranged at regular intervals of, for example, about 1 to 2 meters in the horizontal direction, but as long as the positions of the plurality of receivers 11 are known, the intervals between the receivers 11 are known. Does not matter.

Further, the ground structure estimation system 1 is a plurality of receivers arranged in the excavation hole 9 extending downward from the point B on the ground surface G, that is, at a plurality of vibration receiving points having different vertical positions in the ground. 12 is provided. The vibration receiver 12 receives vibration generated at an oscillation point in the ground by an oscillator 14 described later. More specifically, the vibration receiver 12 continuously measures the magnitude of the vibration received and outputs data indicating the measurement result. The data continuously output from the vibration receiver 12 is stored in the ground structure estimation device 15 (described later) as waveform data representing a change in the magnitude of vibration with time, that is, a waveform. As the vibration receiver 12, an underwater vibration receiver (hydrophone) is used. It is desirable that the plurality of receivers 12 are arranged at regular intervals of, for example, about 1 to 2 meters in the vertical direction, but as long as the positions of the plurality of receivers 12 are known, the intervals between the receivers 12 are known. Does not matter.

Further, the ground structure estimation system 1 includes an oscillator 13 that causes vibration at an oscillation point on the ground surface G. As the oscillating tool 13, for example, Kakeya is used, but the oscillating tool 13 may be any device or device as long as it can cause vibration on the ground surface G. The oscillator 13 has a function of outputting oscillation notification data at the timing of vibration.

Further, the ground structure estimation system 1 includes an oscillating tool 14 that causes vibration at an oscillating point in the ground located below the point A. As the oscillating tool 14, for example, an oscillating device that causes vibration by a piezoelectric diaphragm is used, but the oscillating tool 14 may be any device or device as long as it can cause vibration in the ground. The oscillator 14 has a function of outputting oscillation notification data at the timing of vibration.

Further, the ground structure estimation system 1 includes a ground structure estimation device 15 that estimates the ground structure based on the vibration received by the vibration receiver 11 and the vibration receiver 12. The ground structure estimation device 15 is realized by, for example, a computer performing a process according to the program according to the present embodiment, but instead, the ground structure estimation device 15 may be configured as a dedicated device.

FIG. 2 is a diagram showing a functional configuration of the ground structure estimation device 15. The ground structure estimation device 15 first includes a storage means 150 for storing various data and a timekeeping means 151 for continuously measuring the current time.

Further, the ground structure estimation device 15 includes an oscillation notification data acquisition unit 152 that acquires oscillation notification data output from each of the oscillator 13 and the oscillator 14 at the timing when the oscillators cause vibration. The oscillation notification data acquired by the oscillation notification data acquisition means 152 is accompanied by identification data for identifying the oscillator that outputs the oscillation notification data. When the oscillation notification data acquisition means 152 acquires the oscillation notification data, it acquires time data indicating the current time at the time of acquisition from the time measuring means 151, associates the time data with the oscillation notification data, and stores the time data in the storage means 150. ..

Further, the ground structure estimation device 15 continuously obtains waveform data acquisition means 153 from each of the plurality of receivers 11 and the plurality of receivers 12 to indicate the magnitude of vibration received by those receivers. Be prepared. The data acquired by the waveform data acquisition means 153 is accompanied by identification data that identifies the receiver that outputs the data. When the waveform data acquisition means 153 acquires data from the receiver 11 or the receiver 12, it acquires time data indicating the current time at the time of acquisition from the time measuring means 151, and converts the data acquired from the receiver 11 or the receiver 12 into the data. The time data is associated with each other and stored in the storage means 150. The data continuously acquired by the waveform data acquisition means 153 from the same receiver 11 or the receiver 12 and stored in the storage means 150 becomes waveform data representing a change in the magnitude of vibration with time, that is, a waveform.

Further, among the data stored in the storage means 150, the ground structure estimation device 15 stores the oscillation notification data acquired by the oscillation notification data acquisition means 152 from the oscillator 13 and the oscillation notification data in association with the oscillation notification data. The S wave velocity structure estimation means 154 for estimating the S wave velocity structure of the ground by using the time data and the waveform data acquired by the waveform data acquisition means 153 from the vibration receiver 11 is provided.

In general, the propagation velocity of the surface wave of the vibration propagating in the ground is 0.9 to 0.95 times the propagation velocity of the S wave of the vibration. The S wave velocity structure estimation means 154 uses the relationship between the surface wave and the propagation velocity of the S wave to convert the propagation velocity according to the frequency of the surface wave represented by the waveform data into the propagation velocity of the S wave, and S of the ground. Estimate the wave velocity structure.

The S wave velocity structure estimation means 154 stores the S wave velocity structure data representing the estimated S wave velocity structure of the ground in the storage means 150.

Further, among the data stored in the storage means 150, the ground structure estimation device 15 stores the oscillation notification data acquired by the oscillation notification data acquisition means 152 from the oscillating tool 14 and the oscillation notification data in association with the oscillation notification data. Using the time data, a series of waveform data acquired by the waveform data acquisition means 153 from the vibrator 12, the time data stored in association with the waveform data, and the S wave velocity structure data, the P wave velocity of the ground. A P-wave velocity structure estimation means 155 for estimating the structure is provided. The P-wave velocity structure estimation means 155 stores the P-wave velocity structure data representing the estimated P-wave velocity structure of the ground in the storage means 150.

Further, the ground structure estimation device 15 is a Young's modulus distribution estimation means for estimating the distribution of Young's modulus of the ground by using the S wave velocity structure data and the P wave velocity structure data among the data stored in the storage means 150. 156 is provided. The Young's modulus distribution estimation means 156 stores the Young's modulus distribution data representing the estimated Young's modulus distribution of the ground in the storage means 150.

Further, the ground structure estimation device 15 uses the S wave velocity structure data and the P wave velocity structure data among the data stored in the storage means 150 to estimate the distribution of the shear elastic modulus of the ground. The estimation means 157 is provided. The shear elastic modulus distribution estimation means 157 stores the shear elastic modulus distribution data representing the estimated distribution of the shear elastic modulus of the ground in the storage means 150.

Subsequently, a ground structure estimation method (hereinafter, referred to as “ground structure estimation method M”) according to the present embodiment, which is carried out using the ground structure estimation system 1, will be described.

The ground structure estimation method M largely includes the following steps.

(Step P1) Between points A and B, vibration is caused by the oscillator 13 at each of the oscillation points of a plurality of ground surfaces G whose horizontal positions are different from each other, and the surface wave of the vibration is generated by the plurality of receivers 11. The process of receiving vibration.

(Step P2) A step in which the S wave velocity structure estimation means 154 of the ground structure estimation device 15 estimates the S wave velocity structure of the ground based on the surface waves received by the plurality of vibration receivers 11.

(Step P3) Below point A, with respect to each of a plurality of underground oscillation points whose vertical positions are different from each other, vibration is caused by the oscillator 14 at the oscillation point, and the P wave of the vibration is transmitted to a plurality of receivers. Step of receiving vibration according to 12.

(Step P4) A step in which the P wave velocity structure estimation means 155 of the ground structure estimation device 15 estimates the P wave velocity structure of the ground based on the estimated S wave velocity structure and the received P wave.

(Step P5) A step in which the Young's modulus distribution estimation means 156 of the ground structure estimation device 15 estimates the Young's modulus distribution of the ground based on the estimated P wave velocity structure.

(Step P6) A step in which the shear elastic modulus distribution estimation means 157 of the ground structure estimation device 15 estimates the distribution of the shear elastic modulus of the ground based on the estimated P wave velocity structure.

The order of the above steps P5 and P6 does not matter.

FIG. 3 is a diagram showing an example of the procedure of the ground structure estimation method M including the above steps.

First, the operator sets a plurality of oscillation points set between points A and B on the ground surface G and having different positions in the horizontal direction, that is, oscillation points X1, X2, ..., Xn (however, n). Is an arbitrary natural number) (hereinafter, oscillation points X1, X2, ..., Xn are collectively referred to as "oscillation point X"), the oscillator 13 is used at the first oscillation point X, that is, the oscillation point X1. Causes vibration (step S101). It is desirable that the plurality of oscillation points X are arranged at regular intervals of, for example, about 1 to 2 meters in the horizontal direction, but as long as the positions of the plurality of oscillation points X are known, the intervals between the oscillation points X are known. Does not matter.

In step S101, the storage means 150 of the ground structure estimation device 15 stores time data indicating the time when the vibration occurred at the oscillation point X1.

Each of the plurality of vibration receivers 11 receives a surface wave of vibration generated in step S101 and propagated in the ground (step S102). In step S102, the storage means 150 of the ground structure estimation device 15 stores waveform data representing the waveform of the surface wave received by the receiver 11 for each of the plurality of receivers 11.

Subsequently, the operator vibrates at the next oscillation point X (hereinafter, “oscillation point Xi” (where i is a natural number of 2 or more and n or less)) using the oscillator 13 as in step S101. (Step S103). In step S103, the storage means 150 of the ground structure estimation device 15 stores time data indicating the time when the vibration occurred at the oscillation point Xi.

Each of the plurality of vibration receivers 11 receives a surface wave of vibration generated in step S103 and propagated in the ground (step S104). In step S104, the storage means 150 of the ground structure estimation device 15 stores waveform data representing the waveform of the surface wave received by the receiver 11 for each of the plurality of receivers 11.

If there is another oscillation point X (step S105; Yes), the operator repeats the operation of step S103 with respect to the oscillation point X. As a result, the storage means 150 of the ground structure estimation device 15 contains time data indicating the time when the vibration was generated at the new oscillation point Xi, and the waveform of the surface wave received by each of the plurality of vibration receivers 11 regarding the vibration. Waveform data representing is stored.

On the other hand, when there is no next oscillation point X (step S105; No), the operator finishes the work of causing vibration using the oscillator 13 and provides the operator in advance so as to extend downward from the point A on the ground surface G. A plurality of oscillation points set in the drilled holes 8 having different positions in the vertical direction, that is, oscillation points Y1, Y2, ..., Ym (where m is an arbitrary natural number) (hereinafter, m is an arbitrary natural number). Of the oscillation points Y1, Y2, ..., Ym are collectively referred to as "oscillation points Y"), at the first oscillation point Y, that is, the oscillation point Y1, the oscillator 14 is used to cause vibration (step S201). .. It is desirable that the plurality of oscillation points Y are arranged at regular intervals of, for example, about 1 to 2 meters in the vertical direction, but as long as the positions of the plurality of oscillation points Y are known, the intervals between the oscillation points Y are known. Does not matter.

In step S201, the storage means 150 of the ground structure estimation device 15 stores time data indicating the time when the vibration occurred at the oscillation point Y1.

Each of the plurality of vibration receivers 12 receives a P wave of vibration generated in step S201 and propagated in the ground (step S202). In step S202, the storage means 150 of the ground structure estimation device 15 stores waveform data representing the waveform of the P wave received by the receiver 12 for each of the plurality of receivers 12.

Subsequently, the operator vibrates at the next oscillation point Y (hereinafter, “oscillation point Yj” (where j is a natural number of 2 or more and m or less)) using the oscillator 14 as in step S201. (Step S203). In step S203, the storage means 150 of the ground structure estimation device 15 stores time data indicating the time when the vibration occurred at the oscillation point Yj.

Each of the plurality of vibration receivers 12 receives a P wave of vibration generated in step S203 and propagated in the ground (step S204). In step S204, the storage means 150 of the ground structure estimation device 15 stores waveform data representing the waveform of the P wave received by the receiver 12 for each of the plurality of receivers 12.

If there is another oscillation point Y (step S205; Yes), the operator repeats the work of step S203 with respect to the oscillation point Y. As a result, the storage means 150 of the ground structure estimation device 15 contains time data indicating the time when the vibration was generated at the new oscillation point Yj, and the waveform of the P wave received by each of the plurality of vibration receivers 12 regarding the vibration. Waveform data representing is stored.

On the other hand, when there is no next oscillation point Y (step S205; No), the operator instructs the ground structure estimation device 15 to estimate the S wave velocity structure. In response to this instruction, the S-wave velocity structure estimation means 154 of the ground structure estimation device 15 determines the oscillation time of vibration at each of the plurality of oscillation points X indicated by the time data stored in the storage means 150, and their vibrations. Based on the surface waves received by each of the plurality of oscillators 11 represented by the waveform data corresponding to each of the above, a shallow portion of the ground (for example, a portion from the ground surface G to a position of about 15 meters in depth, FIG. 1). The S-wave velocity structure of region C) is estimated (step S301).

Since the estimation of the S wave velocity structure performed by the S wave velocity structure estimation means 154 in step S301 follows a known surface wave exploration method, the description thereof will be omitted.

In step S301, the storage means 150 of the ground structure estimation device 15 stores S wave velocity structure data representing the estimated S wave velocity structure.

Subsequently, the operator finishes the work of causing vibration using the oscillator 14, and instructs the ground structure estimation device 15 to estimate the P wave velocity structure. In response to this instruction, the P wave velocity structure estimation means 155 of the ground structure estimation device 15 first obtains the ground from the S wave velocity structure in the ground region C represented by the S wave velocity structure data stored in the storage means 150. For estimating the P-wave velocity structure of the region C and the portion deeper than the region C (for example, the portion from the ground surface G to a depth of about 30 to 50 meters, the region D in FIG. 1) according to the elastic wave tomography method. Initial parameters are set (step S302).

ただし、Ｖ_pはＰ波の伝播速度、Ｖ_sはＳ波の伝播速度、νは地盤のポアソン比である。 In general, it is known that the relationship represented by the following equation 1 is generally established between the propagation velocity of the S wave of vibration propagating in the ground and the propagation velocity of the P wave.

However, V _p is the propagation velocity of the P wave, V _s is the propagation velocity of the S wave, and ν is the Poisson's ratio of the ground.

The Poisson's ratio of the ground generally takes a value of about 0.2 to 0.4. Therefore, in step S302, the P wave velocity structure estimating means 155 sets the propagation velocity of each P wave of the plurality of cells constituting the region C to the S wave velocity according to Equation 1, assuming that, for example, ν = 0.3. It is calculated based on the S wave propagation velocity of the cell estimated by the structure estimation means 154, and the calculated estimated value of the P wave propagation velocity is set as the initial parameter of the cell. In the present application, the “cell” means a partial region obtained by dividing the target region for estimating the P wave velocity structure of the ground by the elastic wave tomography method into a plurality of regions. It should be noted that the speed of the P wave is considered to be the same in each cell.

Further, in step S302, the P-wave velocity structure estimation means 155 sets each of the plurality of cells constituting the portion of the region D other than the region C, for example, the deepest cell among the cells in the region C directly above the cell. Set the same initial parameters as the set initial parameters. In this example, assuming that the P wave velocity structure of the portion other than the region C of the region D is the same as the P wave velocity structure of the lower end portion of the region C, the initial stage of the cell of the portion other than the region C of the region D. This is an example of setting parameters, but for example, predetermined default values may be used as the initial parameters of those cells.

Subsequently, the P-wave velocity structure estimating means 155 represents the oscillation time of vibration at each of the plurality of oscillation points Y indicated by the time data stored in the storage means 150, and the waveform data corresponding to each of the vibrations. Based on the P wave received by each of the plurality of vibration receivers 12, the P wave velocity structure of the ground region D (FIG. 1) is estimated using the initial parameters set in step S302 (step S303).

Since the estimation of the P wave velocity structure performed by the P wave velocity structure estimation means 155 in step S303 follows a known elastic wave tomography method, the description thereof will be omitted.

In step S303, the storage means 150 of the ground structure estimation device 15 stores P wave velocity structure data representing the estimated P wave velocity structure.

ただし、Ｅはヤング率、νは地盤のポアソン比、ρは地盤の密度、Ｖ_pはＰ波の伝播速度である。ヤング率分布推定手段１５６は、νの値として例えば０．３を用い、ρの値として例えば２．０（ｇ／ｃｍ³）を用い、Ｖ_pとしてステップＳ３０３において推定されたＰ波の伝播速度を用いる。ここで、ρ＝２．０（ｇ／ｃｍ³）は一般的な地盤の密度であるが、これに代えて、例えば領域Ｄの土のサンプルから計測した密度がρとして用いられてもよい。 Subsequently, the Young's modulus distribution estimation means 156 of the ground structure estimation device 15 estimates the Young's modulus distribution in the region D, that is, the Young's modulus of each cell in the region D, for example, according to the following equation 2 (step S304).

However, E is Young's modulus, ν is the Poisson's ratio of the ground, ρ is the density of the ground, and V _p is the propagation velocity of the P wave. The Young's modulus distribution estimation means 156 uses, for example, 0.3 as the value of ν, 2.0 (g / cm ³ ) as the value of ρ, and the propagation velocity of the P wave estimated in step S303 as _{V p.} Is used. Here, ρ = 2.0 (g / cm ³ ) is a general ground density, but instead, for example, the density measured from a soil sample in region D may be used as ρ.

In step S304, the storage means 150 of the ground structure estimation device 15 stores Young's modulus distribution data representing the estimated Young's modulus distribution.

ただし、Ｇはせん断弾性係数、νは地盤のポアソン比、Ｅはヤング率である。せん断弾性係数分布推定手段１５７は、νの値として例えば０．３を用い、ＥとしてステップＳ３０４において推定されたヤング率を用いる。 Subsequently, the shear elastic modulus distribution estimation means 157 of the ground structure estimation device 15 estimates the distribution of the shear elastic modulus in the region D, that is, the shear elastic modulus of each cell in the region D according to the following equation 3 (step S305). ).

However, G is the shear modulus, ν is the Poisson's ratio of the ground, and E is Young's modulus. The shear elastic modulus distribution estimation means 157 uses, for example, 0.3 as the value of ν, and uses the Young's modulus estimated in step S304 as E.

In step S305, the storage means 150 of the ground structure estimation device 15 stores shear elastic modulus distribution data representing the estimated shear elastic modulus distribution.

The P wave velocity structure data, Young's modulus distribution data, and shear elastic modulus distribution data stored in the storage means 150 of the ground structure estimation device 15 as described above indicate the characteristics of the ground region D for each cell. According to the ground structure estimation method M, the P wave propagation velocity estimated based on the S wave velocity structure estimated by the surface wave exploration method is used as an initial parameter in the estimation of the P wave velocity structure by the elastic wave tomography method. Be done. Therefore, the propagation velocity of the P wave in each cell can be easily specified as compared with the case where, for example, a predetermined default value is used as the initial parameter in the estimation of the P wave velocity structure by the elastic wave tomography method. As a result, the processing load required for estimating the P-wave velocity structure of the ground is significantly reduced.

[Modification example]
The above embodiments can be modified in various ways. An example of these modifications is shown below. In addition, two or more modified examples shown below may be combined as appropriate.

In the above-described embodiment, the excavation hole 8 is provided in advance so as to extend downward from the point A, and the oscillator 14 arranged at the oscillation point Y in the excavation hole 8 oscillates. Instead of this, the oscillator 14 is inserted into the ground from the point A on the ground surface G in the state where the excavation hole 8 is not provided, and each time the oscillator 14 reaches each of the plurality of oscillation points Y, the oscillator 14 is inserted. Oscillation may be performed.

If the oscillator 14 is a structural member (flat steel, angle steel, I-shaped steel, etc.) that can withstand impact, the oscillator 14 may penetrate into the ground by impact. In this case, the vibration generated in the step of receiving the P wave by the oscillator 14 may be generated by penetrating the oscillator 14 into the ground.

As the oscillator 14, a structural member that penetrates into the ground for which the main purpose is not to investigate the ground may be adopted. Examples of such structural members include steel pipe piles, PHC piles, steel pipe sheet piles, and the like. In this case, when these structural members are penetrated into the ground by a hydraulic hammer, a diesel hammer, or the like, vibrations used for estimating the P wave velocity structure are generated.

The ground structure estimation method M may include a step of estimating the hardness of the ground based on the state of penetration of the oscillator 14 (an example of a structural member) into the ground. In this case, the acquisition of the correct answer value regarding the hardness of the ground in the region extending downward from the point A and the estimation of the P wave velocity structure in the region D are performed at the same time.

In the above-mentioned step of estimating the hardness of the ground, a standard penetration test may be performed using a sampler for a standard penetration test as the oscillator 14 (structural member). In this case, when the standard penetration test sampler penetrates into the ground in the standard penetration test, the standard penetration test sampler causes vibration in the ground. Instead of the standard penetration test, other tests such as a ram sounding test, a dynamic cone penetration test, and a piezo drive cone test (liquefaction potential sounding test) may be adopted. For example, if the piezo drive cone test is adopted, information on soil quality can be obtained in addition to the hardness of the ground. The information obtained by these tests (ground hardness, etc.) may be used to estimate the P-wave velocity structure.

In the above embodiment, the vibration used for estimating the S wave velocity structure is generated by the oscillator 13. Instead, the S-wave velocity structure estimation means 154 may estimate the S-wave velocity structure using the constant tremor of the ground.

The mathematical formulas used in the above-described embodiments are examples, and mathematical formulas different from them may be used.

1 ... Ground structure estimation system, 8 ... Drill hole, 9 ... Drill hole, 11 ... Vibration receiver, 12 ... Oscillator, 13 ... Oscillator, 14 ... Oscillator, 15 ... Ground structure estimation device, 150 ... Storage means, 151 ... Time counting means, 152 ... Oscillation notification data acquisition means, 153 ... Waveform data acquisition means, 154 ... S wave velocity structure estimation means, 155 ... P wave velocity structure estimation means, 156 ... Young's modulus distribution estimation means, 157 ... Shear modulus Distribution estimation means.

Claims (5)

For each of the oscillation points on the ground surface having different horizontal positions, vibration is generated at the oscillation points on the ground surface, and the surface wave of the vibration is received at each of the vibration receiving points on the ground surface having different horizontal positions. And the process to do
With respect to each of a plurality of underground oscillation points having different vertical positions, vibration is generated at the underground oscillation points, and a plurality of underground vibration receiving points having different horizontal positions from the plurality of underground oscillation points are received. A step of receiving a P wave of the vibration at each of a plurality of underground vibration receiving points whose positions are different from each other in the vertical direction.
The process of estimating the S-wave velocity structure of the ground by the surface wave exploration method based on the received surface wave, and
A ground structure estimation method including a step of setting initial parameters based on the estimated S wave velocity structure and estimating the P wave velocity structure of the ground by elastic wave tomography based on the received P wave. The ground structure estimation method according to claim 1, further comprising a step of estimating at least one of the distribution of the shear modulus of the ground and the distribution of Young's modulus based on the estimated P-wave velocity structure. The ground structure estimation method according to claim 1 or 2, wherein the vibration generated in the step of receiving the P wave is generated by penetrating the structural member into the ground. The ground structure estimation method according to claim 3, further comprising a step of estimating the hardness of the ground based on the state of penetration of the structural member into the ground. The ground structure estimation method according to claim 4, wherein the structural member is a sampler for a standard penetration test, and includes a step of performing a standard penetration test using the sampler for the standard penetration test.

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