JP2000187080A - Setting method for gas supply stop reference for earthquake, determination method for earthquake meter placing position and gas supply stop method for earthquake in earthquake block - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge properly to stop supply of gas in earthquake blocks where a gas supplier stops gas supply for preventing secondary hazard immediately after a large scale of earthquake. SOLUTION: In earthquake blocks 1, 2, 3,... wherein a lead pipe network 10 is separated, automatic earthquake sensing interrupters are provided in governors 13, 14, 15 and 16. A Vi index corresponding to the ground amplification factor is obtained by usual small motion observation in an earthquake block 1 and the Vi index is corrected in accordance with the ground kind so as to correspond to SI index (indicating an index shown by an earthquake meter). In an earthquake block 1, at least one of earthquake meters 17 and 18 is placed in a position representing the amplification characteristic of the ground. The SI indexes of each governor 13, 14, 15 and 16 when the earthquake meter 17 placed in a representative position shows 60 kines which is the SI index of interruption for preventing secondary hazard are calculated based on the corrected Vi index ratio. Interruption SI indexes are set based on the calculated values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an earthquake in an earthquake block, in which a gas company determines immediately after a large-scale earthquake occurs whether or not to cut off gas supply in order to prevent a secondary disaster. The present invention relates to a method of setting an hourly gas shutoff value, a method of determining a seismometer installation position, and a method of shutting down an earthquake gas.

[0002]

2. Description of the Related Art For a gas company, automatically shutting off gas supply immediately after a large-scale earthquake occurs to prevent a secondary disaster is an important measure as an emergency response in the event of an earthquake. This is also shown in the report of the Earthquake Countermeasures Study Group organized by the Ministry of International Trade and Industry after the 1995 Hyogoken-Nanbu Earthquake in January 1995, and the SI value indicating the shaking index indicated by the seismograph was 60 kine In areas where the above is recorded, it is stated that the gas supply will be stopped immediately.

FIG. 11 shows the definition of an SI value which is an index indicating the magnitude of the earthquake shaking on the ground surface. The SI value is represented by the shaded T about the maximum value Sv (T) of the response speed to an earthquake of one degree of freedom having a natural period T.
= As the average value of the integrated values in the section from 0.1 to 2.5,
It can be calculated by the following first equation.

[0004]

(Equation 1)

[0005] A gas company divides a pipeline network for supplying gas into seismic blocks each having an appropriate size, and detects earthquake shaking by a plurality of governors arranged in the seismic block. If the magnitude of the shaking exceeds a preset cutoff value, an automatic seismic isolation system that shuts off the governor and immediately stops the gas supply when an earthquake occurs, or installs a seismometer inside the earthquake block to When the indicated value of the meter exceeds a preset cutoff value, the supply of gas in the earthquake block is immediately stopped. Usually, a plurality of governors are installed in one earthquake block, and the automatic seismic isolation system is installed in all of the plurality of governors. Also,
Since it is necessary to record the seismic motion, at least one seismometer is installed in one seismic block. In one earthquake block, the cut-off value of the automatic seismic isolation device installed in multiple governors and the cut-off value for determining the immediate stop of supply to city gas based on the measured value of a seismometer are set in one earthquake block. , For example, is set to 40 Cain with allowance for the above-mentioned value of 60 Cain or more.

[0006]

As described above, a gas company divides a gas pipeline network into units of earthquake blocks of an appropriate size, and within one earthquake block, one SI value is used as a cutoff value. When a seismic motion indicating the magnitude of the shake equal to or greater than the cutoff value occurs, the gas supply is stopped. As a method of actually shutting off the gas supply, for example, the above-described seismic automatic shutoff is applied to the medium-pressure governor installed at the point where gas is supplied from the main medium-pressure pipe network to the branch low-pressure pipe network. We have a system in place.

However, even within one earthquake block, there may be a point where a large SI value is recorded, which is a shaking point, and a point where the SI value is not large, which is a point that does not shake much, due to a difference in amplification characteristics of the ground. . If an automatic seismic isolation system with a uniform cutoff value is located in an area with different shaking, it is determined that a shutoff operation that immediately stops the gas supply when an earthquake motion actually occurs. As a result, the result will be different for each automatic seismic isolation system.

Further, when a seismometer is installed in one earthquake block and it is determined whether or not to stop the gas supply according to the SI value detected by the seismometer, the difference in the amplification characteristics of the ground causes Depending on whether the location of the seismometer is shaking well or does not shake much, the determination as to whether or not to immediately stop the gas supply to the seismic block will result in different results.

SUMMARY OF THE INVENTION An object of the present invention is to set a gas shutoff value for an earthquake in an earthquake block in which it is possible to appropriately judge whether or not to stop gas supply when an earthquake occurs in consideration of the ground amplification characteristics in the earthquake block. The purpose of the present invention is to provide a method, a method for determining a seismometer installation position, and a method for shutting off gas during an earthquake.

[0010]

SUMMARY OF THE INVENTION According to the present invention, the magnitude of the magnitude of a seismic motion is set in a seismic block in which a gas company divides a pipeline network and determines whether or not to stop gas supply when an earthquake occurs. A seismometer that measures the height of the ground motion and an automatic seismic sensor that shuts off the gas supply when the magnitude of the seismic motion is greater than Using the amplification characteristics of the ground related to the following SI value,
When the seismometer that measures the magnitude of the seismic motion reaches the SI value that determines the stop of gas supply, the magnitude of the SI value at the installation point of the automatic seismic isolation device is estimated, and the estimated SI value A method of setting a gas shutoff value during an earthquake in an earthquake block, wherein a shutoff value of an automatic seismic isolation device is set based on the threshold value.

According to the present invention, the gas utility divides the pipeline network to define seismic blocks. In the earthquake block, it is determined whether or not to stop the gas supply according to the SI value, which is an index indicating the magnitude of the seismic motion on the ground surface. A point representing the shaking in the earthquake block is determined using the amplification characteristic of the ground related to the SI value. A seismometer will be installed at the determined point to determine the gas supply stop, so the measured value of the seismometer will be representative of the magnitude of the overall seismic motion in the seismic block and will be extremely large or small. Since it does not pass, it is possible to appropriately determine whether to stop the gas supply.

[0012] Further, the present invention provides a seismic block in which a gas company divides a conduit network and determines whether or not to stop gas supply when an earthquake occurs. Using the amplification characteristic of the ground related to the SI value, which is an index indicating, a point representing the shaking of the seismic block is determined, and a seismometer is installed at the determined point to determine whether to stop gas supply. This is a method for determining a seismometer installation position within an earthquake block.

According to the present invention, a plurality of seismic automatic shutoff devices are installed in one seismic block, and the cutoff value for immediately stopping the supply of city gas in the seismic block is set to each seismic automatic shutoff. When the SI value has reached the cutoff value at the position where the device is installed and the position where the seismometer is installed, it can be appropriately set in consideration of the amplification characteristics of the ground at that point.

[0014] Further, the present invention provides a seismic block in which a gas company divides a conduit network to determine whether or not to stop gas supply when an earthquake occurs. By using the amplification characteristic of the ground related to the SI value as an index indicating the, a point representing the shaking of the earthquake block is determined, and a seismometer is installed at the determined point to determine whether to stop gas supply. When the seismometer measures a predetermined magnitude of seismic motion, the gas supply cutoff devices installed in the seismic block are operated in conjunction with each other in the seismic block. This is the method to shut off gas during an earthquake.

In accordance with the present invention, a gas utility divides a network of conduits to define seismic blocks. In the earthquake block, it is determined whether or not to stop the gas supply according to the magnitude of the seismic motion set in advance with respect to the SI value which is an index indicating the magnitude of the seismic motion on the ground surface. . A point representing the shaking in the earthquake block is determined by using the ground amplification characteristics related to the SI value. A seismometer will be installed at the determined point to determine the gas supply stop, so the measured value of the seismometer will be representative of the magnitude of the overall seismic motion in the seismic block and will be extremely large or small. Thus, it is possible to appropriately determine whether to stop the gas supply. All the gas shut-off devices in the earthquake block operate in conjunction with the measurement of the seismometer to measure a predetermined size, so that the supply of the earthquake block can be immediately stopped when an earthquake occurs.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention.
This shows a state where the image is divided into 2, 3,. An intermediate-pressure conduit 11 and a low-pressure conduit 12 are arranged in a conduit network 10 for gas supply. In the low-pressure conduit 12, governors 13, 14, 1
The gas whose pressure has been reduced is supplied from the medium pressure conduit 11 via 5, 5. From the low-pressure conduit 12, gas is further supplied to gas consumers. One earthquake block 1,2,2
Seismometers 17 and 18 that record the magnitude of shaking due to earthquake motion are arranged in 3,. The measurement data of the seismometers 17 and 18 is transmitted to a monitoring center or the like via a wired or wireless radio wave. In the present embodiment, the positions of the seismometers 17 and 18 are set at points representing the magnitude of shaking of the seismic blocks 1, 2, 3,.
The interruption value of the automatic seismic isolation system provided at 16 is set to an appropriate value according to the ground amplification characteristics at the installation position.

FIG. 2 shows a procedure for determining a seismograph installation position and setting a cutoff value in each of the automatic seismic sensors according to the present embodiment. The procedure starts from step s1, and in step s2, the earthquake blocks 1, 2, 3,... Are set. The seismic blocks 1, 2, 3,... Can be appropriately managed by a gas company, and are set as ranges affected by a gas supply stop when all governors 13, 14, 15, 16 are shut off. . In step s3, the governors 13, 14, 15, 16 in the set earthquake blocks 1, 2, 3,.
Each will be equipped with an automatic seismic isolation device. When the shaking caused by the seismic motion reaches a preset cutoff value, the automatic seismic sensor automatically cuts off the supply of gas from the primary side to the secondary side of the governors 13, 14, 15, and 16. When the supply of gas is interrupted by the automatic seismic isolation device, the interruption is not automatically restored even if the seismic motion disappears, and the gas can be supplied only after the operation for releasing the interruption is performed.

In this embodiment, in order to set a cutoff value of each of the automatic seismic isolation devices, the installation position of the automatic seismic isolation device,
That is, at the position where the governors 13, 14, 15, 16 are installed,
Observe microtremors at all times. The microtremor is generated by a natural force such as wind or waves, or an artificial force such as a transportation system or a factory, and is usually a vibration of about several tens μm. Step s5
Then, the time domain data of microtremors observed in step s4 is converted into frequency domain data, and the ratio of the horizontal component to the vertical component is integrated over a certain frequency section to calculate the Vi value. The Vi value represents the amplification characteristic of the ground. Steps
In step 6, the calculated Vi value is corrected so as to correspond to the SI value in accordance with a relationship further empirically obtained.

In step s7, each governor 13, 14,
By comparing the correction values of the Vi value at the installation positions 15 and 16,
It is determined that the seismometers 17 and 18 are to be installed at the positions of the governors 13, 14 and 15 that indicate the Vi values considered to be representative of the respective earthquake blocks 1, 2, 3,... . In step s8, the positions of the governors 13, 14, 15, 16 are determined by relative comparison of the correction values of the Vi values with reference to one of the seismometers 17, 18 whose installation positions are determined in step s7. Then, the relative SI value when the reference seismometers 17 and 18 detect the SI value corresponding to the shutoff value of the gas supply immediate stop is calculated. In each of the governors 13, 14, 15, 16 based on the relative SI value, a cutoff value for immediately stopping the gas supply is set. The cutoff value to be set may be the relative value of the SI value itself, or may be a value close to the relative value. When the position determination in step s7 and the setting of the cutoff value in step s8 are completed, the procedure ends in step s9.

FIG. 3 shows a waveform of a ground motion observed by a seismograph. FIG. 3A shows a waveform of the acceleration A, and FIG. Ground motions generally originate from underground epicenters and propagate through the basement. Seismic waves pass through the ground from the basement and propagate to the ground surface. As the seismic waves propagate through the ground, they are amplified according to the depth and structure of the ground. When the amplitude increases during a large earthquake, the component of the acceleration A may saturate and show nonlinearity, but the velocity component maintains linearity. FIG. 3 (a),
An almost flat part is always a microtremor area before and after a waveform indicating an earthquake motion as shown in (b), and can be always observed using a high-sensitivity vibration sensor.

FIG. 4 shows a schematic configuration of an observation apparatus for constantly observing microtremors and obtaining a Vi value from the observation result. On the ground surface of the observation point, for example, two fine motion sensors 21 and 22 pointing in the north-south (NS) and east-west (EW) directions, respectively.
Is installed. Further, a fine movement sensor 23 oriented in the vertical (UD) direction is also installed. Output signals from the fine movement sensors 21, 22, and 23 are amplified by the amplifier 24, and the signal conditioner 25 removes noise and the like. The output of the signal conditioner 25 is recorded on a recorder 26 in real time, and is subjected to a fast Fourier transform (FFT) process by an FFT analyzer 27 to be converted from time domain data to frequency domain data. The result of the FFT processing is stored in the memory 28. The operating power of the observation device is supplied from a power supply 29 such as a battery. Such an observation device is movable and has a plurality of governors 13, 14, 1.
The microtremor can be always observed by moving to the positions 5 and 16. The data stored in the memory 28 can be subjected to further analysis and arithmetic processing using a personal computer 30 or the like, and can also be used for calculating a Vi value.

FIG. 5 shows a procedure for obtaining a Vi value from observations of microtremors using the observation apparatus shown in FIG. Step a
0, the procedure starts at step a1.
In each of 1, 2, and 23, for example, 10 sets of data are collected. One piece of data is sampled, for example, every 0.01 seconds, and performs sampling at 2048 points. In this case, 20.4
It takes 8 seconds. In step a2, each component is converted into a Fourier spectrum by the FFT analyzer 27. In step a3, two components in the horizontal direction are synthesized. Step a4
Then, smoothing is performed using a Parzem window of 0.3 Hz. In step a5, the geometric mean of each of the horizontal component and the upper and lower components is obtained. In step a6, the horizontal two-dimensional spectrum H and the upper and lower spectrum V are obtained. In step a7, the spectrum ratio H / VR is calculated, and the procedure ends in step a8.

FIG. 6 shows an example of a data waveform during the procedure of FIG. FIGS. 6A and 6B show examples of fine movement of the horizontal component and the vertical component obtained in step a1 of FIG. The horizontal component in FIG. 6A indicates one of the two components. The other is obtained as a similar waveform. FIG.
(C) and FIG. 6 (d) show the Fourier spectrum obtained in step a2 of FIG. FIG. 6E shows FIG.
H / V−R obtained from the ratio between (c) and FIG. 6 (d)
3 shows the waveforms of FIG. The Vi value, which indicates the degree of the sway of the ground and is an index corresponding to the amplification factor of the ground, is calculated according to the following second equation.

[0024]

(Equation 2)

The horizontal component H and the vertical component V are calculated as functions of the period T, respectively. The period T is the reciprocal of the frequency. The integration sections T1 and T2 are set so that the Vi value corresponds to the amplification factor of the ground obtained from the strong vibration record of the past vibration.

FIG. 7 shows H obtained according to the procedure of FIG.
One example of a change in / VR is shown. The area of the integration range indicated by hatching corresponds to the Vi value. Based on data obtained from the Hyogoken Nanbu Earthquake, it has been found that it is appropriate to set an integration range where T1 = 0.1 seconds and T2 = 5 seconds.

FIG. 8 (a) shows the relationship between the ground amplification factor and the Vi value, and FIG. 8 (b) shows the relationship between the maximum speed on the ground surface and the SI value. As shown in FIG. 7A, the ground amplification factor corresponds to the Vi value. Therefore, if the magnitude of the ground motion that propagates to the base is assumed, the ratio of the maximum velocity of the ground motion that is amplified on the ground and transmitted to the ground surface at a plurality of points where the Vi value is obtained can be obtained. FIG.
From (b), it can be seen that the maximum speed and the SI value on the ground surface have a corresponding relationship even though there is a difference between the hard ground shown by the dotted line and the soft ground shown by the solid line. It can be seen that if the Vi value is corrected according to the type, the ratio of the corrected Vi value becomes equal to the ratio of the SI value. The correction of the Vi value corresponding to the ratio of the SI value is performed in the following third case on hard general ground.
In accordance with the following formula, the following formula 4 is used for soft bay shore landfill.

Vi correction value = 1.2 × Vi value (3) Vi correction value = Vi value (4) The following Table 1 corrects the Vi value of one earthquake block and calculates the SI value from the ratio. Is obtained, and the value of the cutoff SI value set in the governor is shown.

[0029]

[Table 1]

Governors are installed at the positions (1) to (1) shown in Table 1. At each position, the Vi value is always obtained from microtremor observation, and correction is performed according to the third or fourth equation according to the type of ground. By comparing the correction values, for example, a position indicated by is determined as a representative of the earthquake block.
A seismometer will be installed near the governor at the location. In this embodiment, another seismometer is installed, for example, adjacent to the governor at the position. The corrected Vi value determined as the representative position is set to 1.0000, and the corrected V value at another position is set.
Calculate the i-value ratio. If the SI value at the position is 60.0, the SI values at other positions change according to the corrected Vi value ratio. The breaking SI value of each governor is, for example, 40.0, 5 based on 60.0 at the position where the seismometer is installed.
Set to 0.0 and 60.0, respectively.

FIG. 9 shows a state of variation of SI values for each earthquake block and a state of determination of an installation position of a seismometer in a certain wide area. In one earthquake block, for example, the SI value is obtained corresponding to the installation position of the governor, and the symbol “□”
As shown. The installation position of the seismometer is set to an average value, an intermediate value, or a position where the appearance frequency is high. The SI value at the position where the seismometer is installed is indicated by the symbol "●". Although the seismometer is installed adjacent to the governor, it can be installed independently of the governor. However, it is advantageous for gas companies to secure a site for seismometer installation if it is installed adjacent to the governor.

FIG. 10 shows another embodiment of the present invention. As in the embodiment of FIG. 1, a gas company divides a pipeline network into a plurality of seismic blocks 1, 2, 3,. In the supply network 10, the medium pressure line 11 is connected to the low pressure line 1.
FIG. 2 shows a configuration in which a gas whose pressure has been reduced is supplied via governors 13, 14, 15, and 16. The seismometers 17 and 18 are arranged in one of the seismic blocks 1, 2, 3,. The measurement data of the seismometers 17 and 18 is transmitted to the shut-off devices 33, 34, 35 and 36 installed in the governors 13, 14, 15 and 16 via a wire or a radio wave. The positions of seismometers 17 and 18 are
Since it represents the magnitude of the shake of 3, ..., the seismograph 1
When the magnitude of the ground motion exceeding the threshold value for stopping the supply of 60 Cain etc., which is set at 7, 18 is measured,
Each of the shut-off devices 33, 34, 35, 36 operates immediately to cut off the gas supply. As a result, the gas supply to all governors 13, 14, 15, 16 in the earthquake block is immediately stopped. When a plurality of seismometers are installed, each of the shutoff devices 33, 34, 35, 36 may be operated based on a representative value of the measured values, for example, an average value or a maximum value.

[0033]

As described above, according to the present invention, the set values of a plurality of automatic seismic isolation devices installed in an earthquake block are
Appropriate settings can be made in accordance with the change in the ground amplification characteristics at the installation point. By setting the cut-off value to be large at points that are prone to shaking and to be small at points that are not prone to shaking, it is possible to ensure safety by immediately shutting off the gas supply reliably in the event of a large earthquake and to reduce the magnitude of the shaking It is possible to reliably prevent erroneous shutoff due to an unprecedented earthquake.

Further, according to the present invention, a seismometer is installed at a point having a typical ground amplification characteristic in the earthquake block, and it is determined whether or not the gas supply is immediately stopped according to the magnitude of the detected shaking. In addition, it is possible to judge whether or not to stop the gas supply immediately without being affected by the fluctuation of the easiness of the earthquake motion.

Further, according to the present invention, a seismometer is installed at a point having a typical ground amplification characteristic in the earthquake block, and when the magnitude of the measured swing becomes a predetermined magnitude, All the gas shut-off devices inside operate in conjunction with each other, and can immediately stop supply as an earthquake block when an earthquake occurs.

[Brief description of the drawings]

FIG. 1 is a simplified map showing a state of an earthquake block according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure for determining a seismometer installation position and setting a shutoff value of an automatic seismic sensor shutoff device in the earthquake block of FIG. 1;

FIG. 3 is a waveform diagram of acceleration and velocity of a seismic motion observed by a seismograph.

FIG. 4 is a block diagram showing a schematic electrical configuration of a microtremor observation device.

FIG. 5 is a flowchart showing a procedure for calculating a Vi value using the observation device of FIG. 4;

FIG. 6 is a graph showing a data waveform in the middle of the procedure of FIG. 5;

FIG. 7 is a graph showing an integration range for calculating a Vi value.

FIG. 8 is a graph showing the relationship between the amplification factor of the ground due to seismic motion and the Vi value, and the relationship between the maximum velocity of the ground surface and the SI value.

FIG. 9 is a graph showing the relationship between the distribution of SI values for each of a plurality of earthquake blocks and the installation position of the seismometer.

FIG. 10 is a simplified map showing a state of an earthquake block according to another embodiment of the present invention.

FIG. 11 is a graph showing definitions of SI values.

[Explanation of symbols]

 1, 2, 3,... Earthquake block 10 Pipe network 13, 14, 15, 16 Governor 17, 18 Seismometer 21, 22, 23 Micromotion sensor 27 FFT analyzer 28 Memory 30 Personal computer 33, 34, 35, 36 Breaking device

Claims (3)

[Claims] 1. A seismometer for measuring the magnitude of a seismic motion in a seismic block in which a gas company divides a conduit network and determines whether to stop supplying gas when an earthquake occurs. An automatic seismic sensor that shuts off the gas supply when the magnitude of the seismic motion is greater than the cutoff value is installed, and is used as an index that indicates the magnitude of the seismic motion on the ground surface.
When the seismometer that measures the magnitude of seismic motion using the amplification characteristic of the ground related to the value becomes the SI value that determines the gas supply stop, the magnitude of the SI value at the installation point of the automatic seismic isolation device And setting a shutoff value of the automatic seismic isolation device based on the estimated magnitude of the SI value. 2. An index indicating the magnitude of the vibration of a ground motion on a ground surface in a seismic block in which a gas company divides a pipeline network to determine whether to stop gas supply when an earthquake occurs. SI
An earthquake characterized by determining a point representing the shaking of the seismic block using the amplification characteristic of the ground related to the value, and installing a seismometer at the determined point to judge the stop of gas supply. How to determine the seismometer installation position in the block. 3. An index indicating the magnitude of the tremor of a ground motion in a seismic block in which a gas company divides a pipeline network and determines whether or not to stop gas supply when an earthquake occurs. SI
Using the amplification characteristics of the ground related to the value, determine a point representing the shaking of the seismic block, and install a seismometer at the determined point to determine whether to stop gas supply. A method for shutting off gas during an earthquake in an earthquake block, characterized in that all installed gas supply cutoff devices are operated in conjunction with each other when the seismometer measures a predetermined magnitude of seismic motion. .