JP7095188B1 - Bottoming judgment system and bottoming judgment method - Google Patents

Abstract

A bottoming determination system and a bottoming determination method capable of reliably determining a bottoming layer on which a casing pipe is to be grounded are provided. A bottoming determination system is a bottoming determination system that determines whether a casing pipe, which is penetrated into a soft layer of the seabed by vibration of a vibratory hammer, has reached the bottom, which is the supporting ground beneath the soft layer. The frequency is calculated by repeatedly calculating the frequency characteristics of the vibration detected by the sensor attached to the strut that supports the vibrating hammer and detecting the vibration transmitted from the vibrating hammer, and the vibration detected by the sensor while the casing pipe penetrates the seabed. a determining unit that determines whether the tip of the casing pipe reaches the bottom layer when detecting that the characteristic includes a second peak frequency higher than the characteristic peak frequency in addition to the characteristic first peak frequency of the vibratory hammer; characterized by having [Selection drawing] Fig. 3

Description

The present invention relates to a bottoming determination system and a bottoming determination method.

A sand compaction pile method is known in which a casing pipe is vibrated by a vibro hammer to penetrate into the ground, sand is thrown in while pulling back the casing pipe, and the thrown sand is compacted (see, for example, Patent Document 1). A method for determining that there is a supporting ground layer when the average value obtained by Fourier transforming the vibration data when the auger rod penetrates into the ground changes significantly, which is the average value of the maximum values for each frequency band of the spectrum data. Is known (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2007-309091 Japanese Unexamined Patent Publication No. 2000-19261

Generally, in the sand compaction pile method in which the soft layer on the seabed is replaced with compacted sand piles, the operator who operates the vibro hammer reads the oscillograph showing the time change of the tip position of the casing pipe to land the casing pipe. It is determined that the pipe has reached the bottom layer. For example, the oscillograph is generated based on the time change of the movement amount of the casing pipe and is displayed on a display screen or the like.

When the bottoming layer on which the casing pipe is to be landed is a clay layer or hard gravel ground, it is possible to determine the bottoming with an oscillograph, but there is a problem that it cannot be determined automatically. On the other hand, for example, if the bottoming layer is a diluvial clay layer with an N value of about "5" or a clay layer mixed with gravel, and it is difficult to distinguish it from the penetration speed of the soft layer, it may be difficult to determine the bottoming by an oscillograph. be.

Furthermore, when the bottoming determination is performed by monitoring the load current value of the motor that operates the vibro hammer or the suspension load value of the casing pipe, the load current value or load value is affected by the friction on the peripheral surface of the casing pipe and It changes depending on the specifications of the machinery and equipment. For this reason, it is necessary to adjust the judgment criteria for the bottoming judgment according to the condition of the ground on the seabed and the specifications of the mechanical equipment, and it is difficult to reliably carry out the bottoming judgment.

In view of the above problems, the present invention provides a bottoming determination system and a bottoming determination method that can reliably determine the bottoming layer to which the casing pipe is desired to land, regardless of the ground condition of the seabed and the specifications of the mechanical equipment. The purpose is to do.

According to one viewpoint, the bottoming determination system determines that the casing pipe penetrating into the soft layer of the sea floor due to the vibration of the vibro hammer has landed on the bottom layer which is the supporting ground of the lower layer of the soft layer. A bottom determination system, a sensor attached to a support column supporting the vibro hammer and detecting vibration transmitted from the vibro hammer, and a frequency characteristic of vibration detected by the sensor during penetration of the casing pipe into the sea floor. Was repeatedly calculated, and it was detected and detected that the calculated frequency characteristic included a plurality of second peak frequencies higher than the unique first peak frequency in addition to the unique first peak frequency of the vibro hammer. When the number of the second peak frequencies whose spectral value is higher than the spectral value of the first peak frequency is equal to or larger than the first reference number among the plurality of the second peak frequencies, the landing at the tip of the casing pipe is performed. It is characterized by having a determination unit for determining the arrival at the bottom layer.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a bottoming determination system and a bottoming determination method that can reliably determine the bottoming layer on which the casing pipe is desired to land, regardless of the condition of the ground on the seabed and the specifications of mechanical equipment. ..

It is a figure which shows an example of the sand compaction ship which carries the bottoming determination system in 1st Embodiment of this invention. It is a figure which shows the outline of the hardware of the measuring apparatus in the bottoming determination system of FIG. It is a flow chart which shows an example of the operation of the bottoming determination system of FIG. It is a figure which shows an example of the acceleration data and the frequency characteristic of the acceleration data which the control device of FIG. 2 displays on a display screen. FIG. 3 is a diagram showing an example of frequency characteristics when the tip of the casing pipe is penetrated into the soft layer in step S40 of FIG. It is a figure which shows the example of the extraction process of the peak frequency in step S60 of FIG. It is a figure which shows an example of the extraction processing of the spectrum larger than the spectrum at the reference frequency by step S70, S80 of FIG. 3 and the count processing of the extracted spectrum. It is a figure which shows an example of the arrival determination processing to the bottom layer by step S90 of FIG. It is a flow figure which shows an example of the operation of the bottoming determination system in 2nd Embodiment of this invention. It is a figure which shows an example of the scalogram displayed in step S30A of FIG. It is a figure which shows an example of the oscillograph which shows the relationship between the position in the sea of the tip of the casing pipe of FIG. 1 and the elapsed time. It is a block diagram which shows an example of the hardware composition of the control device of FIG.

Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of a bottoming determination system according to the first embodiment of the present invention. For example, the bottoming determination system is installed on a sand compaction ship (pedestal) equipped with a compaction device for driving sand piles on the soft ground of the seabed by the offshore sand compaction pile method.

The compaction device has a leader mast 10 erected on the ship and a casing pipe 12 arranged so as to be movable in the vertical direction along the leader mast 10. The leader mast 10 is an example of a support column that supports the vibro hammer 16. Further, the compaction device includes a sand pile driving mechanism portion 20 including a hopper 14, a vibro hammer 16 and a shock absorber 18 installed at the upper end of the casing pipe 12, and a guide roller 22 attached to the sand pile driving mechanism portion 20. And have. The sand pile driving mechanism portion 20 is suspended together with the casing pipe 12 by the suspension wire W.

The guide roller 22 is guided in contact with the slide guide 24 provided on the sand pile driving mechanism 20 side of the leader mast 10 and moves together with the sand pile driving mechanism 20 moving in the vertical direction. Although not particularly limited, the leader mast 10 has a truss structure at the lower part and a tubular structure at the upper part.

Further, the sand compaction ship is equipped with a bottoming determination system that detects that the tip of the casing pipe 12 has passed through the soft layer of the seabed and reached the bottom layer, which is a supporting ground harder than the soft layer. The bottoming determination system includes a sensor unit 30, a measuring device 40, and a control device 50 mounted below the reader mast 10. Hereinafter, the bottoming determination system is also referred to as a bottoming determination system SYS.

For example, the sensor unit 30 is attached to the leader mast 10 at a position on the work floor at a height of 1 m to 2 m on the deck of the sand compaction ship. Therefore, the operator or the like can attach the sensor unit 30 to the reader mast 10 without climbing the reader mast 10, and can safely carry out the attachment work.

For example, the control device 50 is installed in the maneuvering room of the sand compaction ship. The sensor unit 30 and the measuring device 40 are connected by a cable CABL. For example, the measuring device 40 and the control device 50 are wirelessly connected. The measuring device 40 and the control device 50 may be connected by wire.

The sensor unit 30 has an angle ANGL fixed to the truss structure of the reader mast 10 and an acceleration sensor SNS (SNS1, SNS2, SNS3) attached to the angle ANGL at intervals. For example, each acceleration sensor SNS1-SNS3 is fixed to the truss structure together with the angle ANGL by the clamp CLMP.

The acceleration sensors SNS1-SNS3 function as a three-axis acceleration sensor that detects acceleration in the longitudinal direction of the ship, the width direction of the ship, and the vertical direction, respectively. Each acceleration sensor SNS1-SNS3 transmits the measured acceleration signal to the measuring device 40 via the cable CABL.

The measuring device 40 generates acceleration data (amplitude data) by sampling acceleration signals received from each acceleration sensor SNS1-SNS3 at a predetermined cycle, and transmits the generated acceleration data to the control device 50. The sensor unit 30 may have only an acceleration sensor SNS that detects the vertical acceleration of the ship.

For example, the control device 50 is a computer device such as a PC (Personal Computer). The control device 50 may be a mobile terminal such as a tablet. The control device 50 detects whether or not the tip of the casing pipe 12 has reached the bottoming layer, which is the supporting ground of the lower layer of the soft layer, based on the acceleration data received from the measuring device 40. When the control device 50 determines that the tip of the casing pipe 12 has reached the bottoming layer, the control device 50 outputs bottoming information indicating arrival at the bottoming layer to the outside. For example, the control device 50 outputs bottoming information to the outside by at least one of a display screen, an alarm sound (including voice), and light emission of a lamp. As a result, the operator or the like operating the compaction device can recognize the arrival of the tip of the casing pipe 12 at the bottom layer without reading the oscillograph or the like.

In the compaction device shown in FIG. 1, first, the tip of the casing pipe 12 suspended by the wire W is penetrated into the seabed (the surface of the soft layer) by its own weight. After that, the vibro hammer 16 is vibrated in the vertical direction to push the tip of the casing pipe 12 into the soft layer. For example, after removing the silt in the casing pipe 12, a predetermined amount of sand may be put into the tip of the casing pipe 12 so that the sand functions as a lid due to the blocking effect. In this case, the casing pipe 12 can be penetrated into the soft layer by the vibration of the vibro hammer 16 without the silt entering the casing pipe 12 after this.

Hereinafter, for example, the vibration frequency of the vibro hammer 16 will be described as being approximately 9 to 10 Hz. This is because the vibration frequency of the vibro hammer 16 does not depend on the model and is approximately 9 to 10 Hz. Therefore, the control device 50 does not need to determine the reference frequency used for the bottoming determination according to the hardness of the soft layer, and can be the vibration frequency of the vibro hammer 16. In other words, the bottoming determination method according to the present invention can always be carried out using a constant reference frequency regardless of the geology of the seabed ground penetrating the casing pipe 12.

The tip of the casing pipe 12 penetrates into the soft layer by the vibration of the vibro hammer 16 and reaches the bottom layer which is located under the soft layer and is harder than the soft layer. Further, the tip of the casing pipe 12 penetrates into the upper part of the bottoming layer. When the tip of the casing pipe 12 reaches the bottom layer, vibrations containing frequency components higher than the reference frequency are transmitted to the vibro hammer 16 in addition to the specific reference frequency of the vibro hammer 16 due to reflection of vibration from the bottom layer or the like. ..

The natural vibration of the vibro hammer 16 and the vibration having a frequency higher than the reference frequency are transmitted to the reader mast 10 via the guide roller 22 and the slide guide 24. Then, the vibration transmitted to the leader mast 10 is detected as an acceleration by the acceleration sensor SNS attached to the leader mast 10.

As will be described later, the control device 50 detects that the tip of the casing pipe 12 has reached the bottom layer and has begun to penetrate into the bottom layer based on the change in the characteristics of the acceleration detected by the acceleration sensor SNS. ..

FIG. 2 is a diagram showing an outline of the hardware of the measuring device 40 in the bottoming determination system SYS of FIG. 1. The measuring device 40 includes a strain measuring unit 40a, a wireless unit 40b, and a battery unit 40c.

The strain measuring unit 40a converts the acceleration signals received from the acceleration sensors SNS1 to SNS3 via the cable CABL into acceleration data, and outputs the converted acceleration data to the wireless unit 40b. When the sensor unit 30 has only an acceleration sensor SNS that detects acceleration in the vertical direction, the strain measuring unit 40a converts an acceleration signal received from one acceleration sensor SNS into acceleration data, and wirelessly converts the converted acceleration data. Output to unit 40b.

For example, the strain measuring unit 40a converts an acceleration signal into acceleration data at a sampling frequency of 500 Hz to 2000 Hz. The sampling frequency of the acceleration signal is sufficiently higher than the vibration frequency of the vibro hammer 16 (for example, 9 Hz). Therefore, it is possible to accurately detect the reference frequency of the vibration of the vibro hammer 16 transmitted to the reader mast 10 and the acceleration data of the vibration having a frequency higher than the reference frequency.

The wireless unit 40b transmits the acceleration data received from the strain measuring unit 40a to the control device 50. The battery unit 40c supplies electric power to the strain measuring unit and the wireless unit 40b. When an external power source such as an AC (Alternating Current) power source can be supplied to the measuring device 40, the measuring device 40 does not have to have the battery unit 40c.

FIG. 3 is a flow chart showing an example of the operation of the bottoming determination system SYS of FIG. The flow shown in FIG. 3 is started based on, for example, putting the tip of the casing pipe 12 into the sea. For example, the flow shown in FIG. 3 is realized by the control device 50 of FIG. 2 executing the bottoming determination program. That is, FIG. 3 shows an example of a bottoming determination method and a bottoming determination program. The control device 50 that carries out the process of FIG. 3 is an example of a determination unit that determines that the tip of the casing pipe 12 reaches the bottom layer.

First, in step S10, the control device 50 starts receiving acceleration data via the measuring device 40, and stores the received acceleration data in a memory or the like. Next, in step S20, the control device 50 starts an analysis (hereinafter, FFT analysis) of the received acceleration data by a fast Fourier transform (FFT), and calculates the frequency characteristics of the acceleration data. After that, the control device 50 repeatedly receives the acceleration data and calculates the frequency characteristics by the FFT analysis of the acceleration data until the process shown in FIG. 3 is completed.

Next, in step S30, as illustrated in FIG. 4, the control device 50 displays a graph showing the time change of the acceleration data and a graph showing the frequency characteristics of the acceleration data calculated by the FFT analysis on the display screen. do. The control device 50 does not have to display a graph showing the time change of the acceleration data and a graph showing the frequency characteristics on the display screen.

Next, in step S40, the control device 50 repeatedly determines whether or not a peak of the reference frequency has appeared by FFT analysis, and if a peak of the reference frequency appears, the process shifts to step S50.

For example, the control device 50 determines the appearance of a peak of the reference frequency for 1 minute after the tip of the casing pipe 12 penetrates into the soft layer. When an oscillograph is used when placing a sand pile, the control device 50 determines the appearance of a peak of a reference frequency when the tip of the casing pipe 12 is within an arbitrary depth range of a predetermined depth of the soft layer. You may. When using an oscillograph, the control device 50 acquires depth information indicating the depth of the tip of the casing pipe 12 in the sea, which is determined according to the amount of movement of the casing pipe, from the oscillograph generation device.

As described with reference to FIG. 1, the reference frequency is the vibration frequency of the vibro hammer 16 (for example, 9 Hz). In step S50, the control device 50 stores the acquired frequency value Fv of the reference frequency and the spectrum value Sv such as the linear spectrum in a memory or the like. In the following, frequency and spectral values are also simply referred to as frequency and spectrum.

Next, in step S60, the control device 50 performs an extraction process for extracting a peak frequency higher than the reference frequency Fv based on the result of the FFT analysis. For example, the control device 50 starts the peak frequency extraction process based on the fact that the tip of the casing pipe 12 reaches a position separated by a predetermined distance from the assumed bottoming layer. For example, when the sampling pitch is 500 Hz and the data extraction process is performed once every 2 seconds, 1000 data can be acquired in 2 seconds, so 1024 (2 to the 10th power) is selected as the number of analysis data.

Next, in step S70, the control device 50 determines whether or not there is a spectrum larger than the spectrum Sv among the peak frequencies extracted in step S60. The control device 50 shifts the processing to step S80 when there is a spectrum larger than the spectrum Sv, and returns the processing to step S60 when there is no spectrum larger than the spectrum Sv.

In step S80, the control device 50 counts the number m (landing determination index) of spectra larger than the spectrum Sv.

Next, in step S90, the control device 50 determines whether or not the tip of the casing pipe 12 has reached the bottom layer based on the counted number m. For example, when the counted number m is equal to or larger than the preset first reference number, the control device 50 may determine the arrival at the bottom layer. Further, the control device 50 may determine the arrival at the bottom layer when the number of times the counted number m is determined to be equal to or greater than the first reference number is equal to or greater than the reference number of times.

When the control device 50 determines that the landing layer has been reached, the process proceeds to step S100, and when it is determined that the process has not reached the bottom layer, the control device 50 returns the process to step S60. An example of the determination process of reaching the bottom layer is shown in FIG.

The control device 50 may determine that the tip of the casing pipe 12 reaches the bottom layer when the peak frequency having a frequency higher than the reference frequency is detected without counting the number m in step S80. .. Alternatively, when the control device 50 does not count the number m in step S80 and detects that the spectral value of the peak frequency higher than the reference frequency is larger than the spectral value of the reference frequency, it determines that it has reached the bottom layer. May be.

Further, when the control device 50 does not count the number m in step S80 and detects a plurality of peak frequencies having frequencies higher than the reference frequency, the control device 50 determines that the tip of the casing pipe 12 reaches the bottom layer. May be good.

In step S100, the control device 50 outputs bottoming information (reaching the bottoming layer) indicating that the tip of the casing pipe 12 has reached the bottoming layer, for example, for displaying on a display screen, and the processing of FIG. To finish.

FIG. 4 is a diagram showing an example of the acceleration data displayed on the display screen by the control device 50 of FIG. 2 and the frequency characteristics of the acceleration data. For example, the control device 50 displays a graph showing the time change of the acceleration data for each of the acceleration sensors SNS1 to SNS3, and displays a graph of the frequency characteristics (spectrum) of the acceleration data every time a predetermined time elapses. Here, the acceleration data and the linear spectrum are shown, and the unit is m / s ² .

In FIG. 4, in order to make it easier to understand the explanation of the frequency characteristics converted from the acceleration data, the graph of the acceleration data (acceleration amplitude) is shown until a predetermined time (360 seconds) elapses regardless of the arrival determination of the bottom layer. It is displayed.

For example, the control device 50 displays the frequency characteristics of the acceleration data acquired by the acceleration sensor SNS designated in advance by the operator or the like as a graph. In the example of FIG. 4, the control device 50 acquires the frequency characteristic of the acceleration data acquired by the acceleration sensor SNS that detects the vibration in the vertical direction (the height direction of the leader mast 10). FIG. 4 illustrates frequency characteristics at time T1 (30 seconds) and time T2 (240 seconds).

From 0 seconds to time T1, acceleration data before the tip of the casing pipe 12 reaches the seabed is shown. At the time T1 (30 seconds) when the tip of the casing pipe 12 started to penetrate the sea floor (soft layer), the vibration of the tip of the casing pipe 12 penetrated into the soft layer was absorbed by the soft layer, and the casing was made from the soft layer. There is almost no reflection of vibration on the pipe 12.

Therefore, the waveform of the spectrum at time T1 has a peak only in the vicinity of 9 Hz, which is the vibration frequency of the vibro hammer 16. In other words, when the peak frequency of the spectrum is only the vibration frequency of the vibro hammer 16, the control device 50 can determine that the tip of the casing pipe 12 does not reach the bottom layer.

On the other hand, after the time T2 (240 seconds) when the tip of the casing pipe 12 reaches the bottom layer, the tip of the casing pipe 12 vibrates in the bottom layer which is harder than the soft layer. Therefore, a part of the vibration at the tip of the casing pipe 12 is not absorbed by the bottom layer, but is transmitted to the tip of the casing pipe 12 as a reflection of the vibration from the bottom layer, and further, the vibro hammer 16, the guide roller 22, and the leader mast. It is transmitted up to 10. At this time, as the frequency of vibration transmitted from the bottom layer, peaks of a plurality of frequencies higher than the reference frequency (= 9 Hz) appear. Further, some of the peak values (spectral values) of a plurality of frequencies higher than the reference frequency are larger than the peak values of the reference frequency.

FIG. 5 is a diagram showing an example of frequency characteristics calculated when the tip of the casing pipe 12 penetrates into the soft layer in step S40 of FIG. When the control device 50 acquires the reference frequency Fv (for example, 9 Hz), the control device 50 records the values of the reference frequency Fv and the spectrum Sv (for example, 0.15 m / s ² ) in a memory or the like. Note that FIG. 5 shows the frequency characteristics at the time T1 of FIG. 4, and the control device 50 repeatedly performs the acquisition process of step S40 until the reference frequency Fv is extracted, and calculates the frequency characteristics respectively.

FIG. 6 is a diagram showing an example of the peak frequency extraction process in step S60 of FIG. For example, the control device 50 extracts peak frequencies higher than the reference frequency Fv in descending order of the spectrum by a preset number of samples n (n = "5" in this example). Then, the control device 50 records the extracted peak frequency value Fn (F1-F5) and the spectrum value Sn (S1-S5) in a memory or the like. The reference frequency Fv is an example of the first peak frequency, and the peak frequency higher than the reference frequency Fv is an example of the second peak frequency.

FIG. 7 is a diagram showing an example of extraction processing of a spectrum larger than the spectrum Sv at the reference frequency Fv according to steps S70 and S80 of FIG. 3 and counting processing of the extracted spectrum. The control device 50 counts the number m of peak frequencies whose spectrum is larger than the spectrum Sv at the reference frequency Fv among the five peak frequencies extracted in FIG.

In the example shown in FIG. 7, the control device 50 counts the number m (3 in this example) of the peak frequencies F1, F2, and F3 of the spectra S1, S2, and S3, which are larger than the spectra Sv. For example, the peak frequencies are F1 = 65 Hz, F2 = 38 Hz, and F3 = 84 Hz, respectively, and the spectra are S1 = 0.65 m / s ² , S2 = 0.22 m / s ² , and S3 = 0.19 m / s, respectively. It is ² . The numerical values at the end of the spectra S2, S1 and S3 indicate the order of the magnitude of the spectra.

Then, the control device 50 repeatedly performs the extraction process of the peak frequency shown in FIG. 6 and the counting of the number m shown in FIG. 7 at predetermined time intervals. When the number m of spectra larger than the spectrum Sv is equal to or greater than the first reference number having a predetermined threshold value Vth, the control device 50 may determine the arrival at the bottom layer. For example, the first reference number is three.

As shown in the equation (1), the control device 50 extracts a spectrum larger than the value obtained by multiplying the spectrum Sv by the coefficient α from the spectra Sn of the five peak frequencies, and determines the number m of the extracted spectra. You may count. For example, in FIG. 7, the coefficient α is set to "1.0".
Sn> α × Sv ‥ (1)

FIG. 8 is a diagram showing an example of the arrival determination process to the bottom layer in step S90 of FIG. As shown in FIG. 8, the control device 50 generates data (distribution data of the number of appearances m) of the appearance number m of the spectrum Sn larger than the spectrum Sv. The control device 50 sequentially adds data of the number of appearances m obtained by FFT analysis every 2 seconds to the distribution data, for example.

Next, the control device 50 calculates the average value _move of the number of appearances m for each predetermined time. Then, the control device 50 determines that the tip of the casing pipe 12 has reached the bottom layer when the time when the average value _move becomes "1" or more continues for the second predetermined time. Although not particularly limited, in the example shown in FIG. 8, the first predetermined time is 30 seconds and the second predetermined time is 60 seconds. "1" of the average value _move is an example of the second reference number.

Further, in the example shown in FIG. 8, the control device 50 determines that the time when the average value _move is "1" or more continues for 60 seconds or more with the elapsed time = 120 seconds. Then, the control device 50 sets the elapsed time 60 seconds (that is, the second time) back from the determined elapsed time as the arrival time at the bottom layer. As a result, when the tip of the casing pipe 12 is determined to reach the bottom layer, the tip of the casing pipe 12 has already penetrated the bottom layer for 60 seconds, so that the tip of the casing pipe 12 can reach the bottom layer more reliably. Can be. As a result, the reliability of reaching the bottom layer of the sand pile by the compaction device can be improved.

After that, as shown in step S100 of FIG. 3, the control device 50 outputs bottoming information indicating arrival at the bottoming layer for display on a display screen or the like.

As described above, in this embodiment, the control device 50 calculates the frequency characteristic of the vibration transmitted from the vibro hammer 16 to the reader mast 10, and calculates the spectrum at a frequency higher than the reference frequency Fv of the vibro hammer 16. Then, the control device 50 determines that the tip of the casing pipe 12 reaches the bottom layer based on the detection of the spectrum at a peak frequency higher than the reference frequency Fv. As a result, the operator or the like operating the compaction device can recognize the arrival of the tip of the casing pipe 12 at the bottom layer based on the determination result by the control device 50 without reading the oscillograph or the like.

When the control device 50 determines that the tip of the casing pipe 12 has reached the bottoming layer, the control device 50 outputs bottoming information indicating arrival at the bottoming layer to the outside. As a result, the operator or the like operating the compaction device can recognize the arrival of the tip of the casing pipe 12 at the bottom layer based on the recognition of the bottoming information without reading the oscillograph or the like.

For example, the vibration frequency of the vibro hammer 16 is determined by the model of the vibro hammer 16. Therefore, the control device 50 does not need to determine the reference frequency used for the bottoming determination according to the hardness of the soft layer, and can be the vibration frequency of the vibro hammer 16. In other words, the bottoming determination method according to the present invention does not depend on the geology of the submarine ground penetrating the casing pipe 12 and the specifications of the mechanical equipment, and it is desired to always use a constant reference frequency to land the casing pipe 12. The bottom layer can be reliably determined.

For example, when the control device 50 detects that the spectral value of the peak frequency higher than the reference frequency Fv is larger than the spectral value of the reference frequency Fv, the control device 50 can determine that the tip of the casing pipe 12 has reached the bottom layer. Alternatively, when the control device 50 detects that the spectral values of a plurality of peak frequencies higher than the reference frequency Fv are larger than the spectral values of the reference frequency Fv, it may determine that the tip of the casing pipe 12 reaches the bottom layer. can.

Further, when the number of peak frequencies having a spectrum value larger than the spectrum value of the reference frequency Fv and higher than the reference frequency Fv is equal to or more than the first reference number, the control device 50 reaches the bottom layer at the tip of the casing pipe 12. Can be determined. Further, when the number of times that the control device 50 determines that the number of times is equal to or greater than the first reference number is equal to or greater than the reference number of times, the control device 50 can determine that the tip of the casing pipe 12 has reached the bottom layer.

Alternatively, the control device 50 calculates an average value of the number of second peak frequencies equal to or greater than the first reference number per predetermined time, and determines that the calculated average value is equal to or greater than the second reference number. If so, it is possible to determine that the tip of the casing pipe 12 has reached the bottom layer. Further, when the determination that the average value is equal to or more than the second reference number continues for a second predetermined time longer than the first predetermined time, the control device 50 reaches the bottom layer at the tip of the casing pipe 12. Can be determined.

FIG. 9 is a flow chart showing an example of the operation of the bottoming determination system according to the second embodiment of the present invention. Detailed description of the same processing as in FIG. 3 will be omitted. The bottoming determination system SYS that carries out the operation of FIG. 9 has a function of performing wavelet analysis in addition to the function of the bottoming determination system SYS of the first embodiment.

The configuration of the bottoming determination system SYS of this embodiment is the same as the configuration of the bottoming determination system SYS shown in FIG. Further, the bottoming determination system SYS of this embodiment is installed on a sand compaction ship equipped with a compaction device, as in FIG. 1. The flow of FIG. 9 is the same as the operation flow of FIG. 3 except that steps S20A and 30A are executed instead of steps S20 and S30 of FIG. 3 and steps S92A and S94A are newly executed.

After step S10, in step S20A, the control device 50 starts the wavelet analysis together with the FFT analysis of the received acceleration data, and calculates the time change of the frequency characteristic of the vibration by the wavelet analysis. After that, the control device 50 continues the reception of the acceleration data, the FFT analysis of the acceleration data, and the wavelet analysis until the processing shown in FIG. 3 is completed.

Next, in step S30A, the control device 50 includes a graph showing the time change of the acceleration data exemplified in FIG. 4 and a graph showing the frequency characteristic of the acceleration data, and a scalogram showing the time change of the frequency characteristic obtained by the wavelet analysis. Starts displaying. The control device 50 does not have to display the graph showing the time change of the acceleration data, the graph showing the frequency characteristics, and the scalogram on the display screen. After that, the control device 50 carries out the processes from step S40 to step S80 in the same manner as in FIG.

After determining the arrival at the bottom layer in step S90, the control device 50 extracts the change in the dominant frequency in step S92A based on the scalogram data obtained by the wavelet analysis.

Next, in step S94A, the control device 50 redetermines whether or not the tip of the casing pipe 12 has reached the bottom layer based on the change in the dominant frequency. The control device 50 shifts the process to step S100 when the scalogram data indicates arrival at the bottom layer, and returns the process to step S60 when the arrival at the bottom layer is suspected.

For example, the control device 50 determines the arrival at the bottom layer when the scalogram data changes from the dominant frequency indicating the penetration of the soft layer to the dominant frequency indicating the penetration of the bottom layer. On the other hand, if the scalogram data does not change from the dominant frequency indicating the penetration of the soft layer to the dominant frequency indicating the penetration of the bottom layer, the control device 50 determines that the bottom layer has not been reached.

Then, in step S100, the control device 50 outputs the bottoming information indicating the arrival at the bottoming layer to the display screen or the like, and ends the process of FIG. 9. In this way, the control device 50 determines whether or not the tip of the casing pipe 12 has reached the bottom layer based on the double determination by step S90 and step S94A. Thereby, the accuracy of the arrival determination to the bottom layer can be improved. Further, it can be reliably determined that the tip of the casing pipe 12 has penetrated into the bottom layer.

FIG. 10 is a diagram showing an example of the scalogram displayed in step S30A of FIG. When the tip of the casing pipe 12 is penetrating the soft layer, the scalogram shows that the predominant frequency is 10 Hz, which is about the same as the vibration frequency of the vibro hammer 16. At this time, the bandwidth of the dominant frequency is narrow.

On the other hand, when the tip of the casing pipe 12 is penetrating the bottom layer, the scalogram shows that the predominant frequency is becoming 65 Hz, which is different from the vibration frequency of the vibro hammer 16. When the tip of the casing pipe 12 is penetrating the bottom layer, 10 Hz, which is close to the vibration frequency of the vibro hammer 16, appears in the scalogram, but its intensity is smaller than that of 65 Hz and 40 Hz. Further, the bandwidth of 10 Hz appearing in the scalogram is substantially the same as the bandwidth in which the tip of the casing pipe 12 penetrates the soft layer.

Therefore, when the control device 50 detects that the predominant frequency has changed from the vibration frequency of the vibro hammer 16 to a frequency higher than the vibration frequency of the vibro hammer 16, or when it detects that the frequency is changing, it is transferred to the bottom layer. Penetration can be determined.

As described above, also in this embodiment, similarly to the above-described embodiment, the control device 50 is the bottom layer at the tip of the casing pipe 12 based on the spectral value of the peak frequency of the vibration transmitted from the vibro hammer 16 to the leader mast 10. Can be determined to reach. As a result, the operator or the like operating the compaction device can recognize the arrival of the tip of the casing pipe 12 at the bottom layer based on the determination result by the control device 50 without reading the oscillograph or the like.

Further, in this embodiment, the control device 50 determines the penetration into the bottom layer based on the fact that the dominant frequency determined from the scalogram changes from the vibration frequency of the vibro hammer 16 to a frequency higher than the vibration frequency of the vibro hammer 16. can do. Alternatively, the control device 50 detects intrusion into the bottom layer based on the detection that the dominant frequency determined from the scalogram is changing from the vibration frequency of the vibro hammer 16 to a frequency higher than the vibration frequency of the vibro hammer 16. It can be determined.

Further, the control device 50 determines whether or not the tip of the casing pipe 12 has reached the bottom layer based on the double determination based on the number m of spectra larger than the spectrum Sv (landing determination index) and the scalogram. .. As a result, the accuracy of reaching the bottom layer can be improved, and it can be reliably determined that the tip of the casing pipe 12 has penetrated into the bottom layer.

FIG. 11 is a diagram showing an example of an oscillograph showing the relationship between the position of the tip of the casing pipe 12 in FIG. 1 in the sea and the elapsed time. The oscillograph shown in FIG. 11 shows the time change of the tip position (depth) of the casing pipe 12 in the sea, which is determined according to the movement amount of the casing pipe.

In the example shown in FIG. 11, the surface of the soft layer has a water depth of 20 m, and the surface of the bottom layer has a depth of 33 m. The shallow tip position during penetration into the soft layer indicates the implementation of silt removal treatment. After the silt removal process, sand is put into the tip of the casing pipe 12 to make the sand function as a lid by the blocking effect, and the penetration into the soft layer is continued.

The penetration speed of the casing pipe 12 into the soft layer is almost constant. When the tip of the casing pipe 12 passes through the soft layer and reaches the bottom layer, the penetration speed drops rapidly. Conventionally, an operator or the like operating a compaction device reads an oscillograph displayed on a display device to determine arrival at the bottom layer.

After the tip of the casing pipe 12 reaches the bottom layer, the casing pipe 12 penetrates into the bottom layer by a predetermined amount. After this, the sand pile driving process is started. In the sand pile driving process, first, a predetermined amount of sand is put into the casing pipe 12, and then the casing pipe 12 is pulled out by a predetermined length. Next, the vibro hammer 16 is vibrated and the sand is pressed toward the bottom layer at the tip of the casing pipe 12 to partially form a sand pile. After that, sand is repeatedly put into the casing pipe 12, a predetermined amount of sand is pulled out from the casing pipe 12, and sand is pressed by the vibro hammer 16, to form a sand pile in the soft layer.

FIG. 12 is a block diagram showing an example of the hardware configuration of the control device 50 of FIG. The control device 50 includes a CPU (Central Processing Unit) 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, and an external storage device 54. Further, the control device 50 includes an input interface unit 55, an output interface unit 56, a wireless interface unit 57, and a communication interface unit 58. For example, the CPU 51, ROM 52, RAM 53, external storage device 54, input interface unit 55, output interface unit 56, wireless interface unit 57, and communication interface unit 58 are connected to each other via a bus BUS.

The CPU 51 executes various programs such as an OS (Operating System) and a bottoming determination program, and controls the overall operation of the control device 50. The CPU 51 is an example of a computer that executes a bottoming determination program.

The ROM 52 holds various programs including a bottoming determination program executed by the CPU 51, various parameters, and the like. The RAM 53 stores various programs executed by the CPU 51, data used in the programs, and the like. The external storage device 54 is, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores various programs expanded in the RAM 53.

An input device 60 such as a mouse or a keyboard that receives input from an operator or the like that operates the control device 50 can be connected to the input interface unit 55. Various output devices 70 such as a display device having a display screen, a speaker, a light, or a printer can be connected to the output interface unit 56. When the control device 50 is a mobile terminal such as a notebook computer or a tablet, a part of the input device 60 and the output device 70 may be built in the control device 50.

The wireless interface unit 57 carries out wireless communication with, for example, the wireless unit 40b of FIG. 2. The communication interface unit 58 connects the control device 50 to a network or the like.

Although the present invention has been described above based on each embodiment, the present invention is not limited to the requirements shown in the above embodiments. With respect to these points, the gist of the present invention can be changed to the extent that the gist of the present invention is not impaired, and can be appropriately determined according to the application form thereof.

10 Leader mast 12 Casing pipe 14 Hopper 16 Vibro hammer 18 Shock absorber 20 Sand pile driving mechanism 22 Guide roller 24 Slide guide 30 Sensor unit 40 Measuring device 40a Strain measuring unit 40b Wireless unit 40c Battery unit 50 Control device 51 CPU
52 ROM
53 RAM
54 External storage device 55 Input interface unit 56 Output interface unit 57 Wireless interface unit 60 Input device 70 Output device ANGL angle BUS bus CABL cable CLMP clamp SNS (SNS1, SNS2, SNS3) Acceleration sensor SYS bottoming judgment system W hanging wire

Claims (7)

It is a bottoming determination system that determines that the casing pipe that penetrates into the soft layer of the seabed due to the vibration of the vibro hammer has landed on the bottom layer that is the supporting ground of the lower layer of the soft layer.
A sensor attached to a support column that supports the vibro hammer and detecting vibration transmitted from the vibro hammer,
The frequency characteristics of the vibration detected by the sensor during the penetration of the casing pipe into the sea floor are repeatedly calculated, and the calculated frequency characteristics are added to the unique first peak frequency of the vibro hammer and the unique first peak frequency. It is detected that a plurality of second peak frequencies higher than the peak frequency are included , and among the plurality of detected second peak frequencies, the second peak frequency whose spectral value is higher than the spectral value of the first peak frequency. A bottoming determination system comprising a determination unit for determining the arrival of the tip of the casing pipe at the bottom layer when the number of frequencies is equal to or greater than the first reference number . When the number of times the determination unit determines that the number of second peak frequencies whose spectral value is higher than the spectral value of the first peak frequency is equal to or greater than the number of the first reference number is equal to or greater than the reference number, the bottom layer The bottoming determination system according to claim 1 , further comprising determining the arrival at. The determination unit calculated an average value of the number of second peak frequencies equal to or greater than the first reference number per predetermined time, and determined that the calculated average value was equal to or greater than the second reference number. In the case, the bottoming determination system according to claim 1 , wherein the arrival at the bottoming layer is determined. When the determination that the average value is equal to or greater than the second reference number continues for a second predetermined time longer than the first predetermined time, the determination unit determines that the landing layer has been reached. The bottoming determination system according to claim 3 , which is characterized. The determination unit calculated the time change of the frequency characteristic of the vibration detected by the sensor by wavelet analysis , and determined both the arrival at the bottom layer by the peak frequency and the arrival at the bottom layer by the wavelet analysis. The bottoming determination system according to any one of claims 1 to 4 , wherein the arrival of the tip of the casing pipe to the bottoming layer is determined. When the determination unit detects that the dominant frequency has changed from the first peak frequency to the second peak frequency based on the scalogram data obtained by the wavelet analysis, the determination unit moves to the bottom layer by the wavelet analysis. The bottoming determination system according to claim 5 , wherein the arrival of the frequency is determined. It is a bottoming determination method for determining that the casing pipe penetrating into the soft layer of the seabed due to the vibration of the vibro hammer has landed on the bottom layer which is the supporting ground of the lower layer of the soft layer.
The vibration transmitted from the vibro hammer is detected by a sensor attached to a support column that supports the vibro hammer.
The frequency characteristics of the vibration detected by the sensor during the penetration of the casing pipe into the sea floor are repeatedly calculated, and the calculated frequency characteristics are added to the unique first peak frequency of the vibro hammer and the unique first peak frequency. It is detected that a plurality of second peak frequencies higher than the peak frequency are included , and among the plurality of detected second peak frequencies, the second peak frequency whose spectral value is higher than the spectral value of the first peak frequency. A bottoming determination method comprising determining the arrival of the tip of the casing pipe at the bottom layer when the number of the frequency is equal to or greater than the first reference number .

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