JP2017141636A - Combustible gas jetting predictor in earthquake time - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustible gas jetting predictor in earthquake time, capable of effectively and easily predicting "an event of jetting combustible gas onto the ground by separating from an underground water layer in earthquake time".SOLUTION: A first combustible gas jetting predictor 1 comprises a sealed type observation well 2, a pressure gauge 21 and a data processing device 201. The sealed type observation well 2 is arranged in the vicinity of a building 205, and is constituted of a strainer pipe 11, a circular pipe 12 and a sealing cover 13. The strainer pipe 11 is buried so as to penetrate into a water bearing layer 103 being a pressured underground water layer of dissolving combustible gas, and is formed with a plurality of holes for taking in underground water. The data processing device 201 calculates a change speed of pressure detected by the pressure gauge 21, and determines that abnormality of a pressure change is caused based on the calculated change speed. Jetting onto the ground of the combustible gas caused by the occurrence of an earthquake, can be effectively and easily predicted by this abnormality determination.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for predicting that combustible gas is released from a groundwater layer and is ejected to the ground with the occurrence of an earthquake.

  When vibration is applied to the solvent containing the dissolved gas, a phenomenon occurs in which the liberation between the dissolved gas and the solvent increases. As an example, when a carbonated water that is not supersaturated in a plastic bottle is shaken by hand to give vibration, the stopper is loosened, and carbon dioxide gas spouts out with a push sound. In addition, if this phenomenon is used to dissolve flammable gas in groundwater pumped up from a well or groundwater that has come out during excavation, vibration will be applied after pumping or pumping out the groundwater from the viewpoint of explosion prevention. In some cases, measures are taken to forcibly release flammable gases.

  On the other hand, methane and other flammable gas dissolved groundwater layers are not limited to a specific area, but are distributed throughout Japan. Gas explosion accidents are caused by flammable gas generated from the groundwater layer. Many cases have occurred. For example, in June 2007, there was an accident that killed three people in a gas explosion at a hot spring facility in Shibuya Ward.

  From the facts mentioned above, the combustible gas dissolved in the groundwater layer is released due to the vibration of the groundwater layer at the time of the earthquake, and it floats in the groundwater layer and spouts to the ground surface. It is predicted that the potential danger of the combustible gas exploding using electrical equipment as an ignition source and causing a huge disaster will be hidden throughout Japan.

  Despite such potential dangers, no means has yet been established for predicting the event that combustible gases released from groundwater during the earthquake erupt to the ground and taking countermeasures.

  For example, Patent Document 1 discloses a method for detecting a combustible gas contained in a formation and predicting the risk of a gas explosion in tunnel construction. However, this conventional method is based on the amount of groundwater to be excavated, the temperature, and the hydrostatic pressure, and the amount of dissolved combustible gas based on data such as the amount and concentration of gas released from the collected groundwater. The degree of saturation is calculated by a data processing device, and the risk of gas explosion is judged based on the calculation result. Combustible gas is released from the groundwater layer when an earthquake occurs, There is no disclosure or suggestion of a device that predicts ejection.

Japanese Patent Application Laid-Open No. 8-263377

  An object of the present invention is to provide a prediction device that can effectively and easily predict an event for which a prediction method has not yet been established, that is, an “event in which combustible gas is released from a groundwater layer and erupts to the ground during an earthquake”. That is.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a combustible gas ejection predicting apparatus at the time of an earthquake, and includes a head detecting means for detecting a head of a groundwater layer in which combustible gas is dissolved, and a head detecting means. Based on the change rate of the water head detected in, the abnormality determination means to determine the abnormality of the head change of the groundwater layer at the time of the earthquake, and when the abnormality determination means determines that the head change of the groundwater layer is abnormal, Prediction means for predicting that combustible gas is ejected to the ground with the occurrence of an earthquake.

  The present invention is based on the inventor's knowledge obtained with respect to the relationship between the mechanism of flammable gas ejection due to an earthquake and the change in the head of the groundwater layer. The outline will be described below.

  The combustible gas dissolved in the groundwater layer is released by the earthquake motion and becomes bubbles. The bubbles receive buoyancy and rise in the groundwater layer toward the ground. At the initial stage of the rise, the head change in the groundwater layer is relatively minor. As the rise proceeds, the pressure in the bubble decreases, and the bubble expands rapidly according to Boyle's Law. As the bubbles rise and expand rapidly, the pressure in the upper part of the groundwater layer rapidly increases, and the head of the surrounding groundwater layer rapidly increases. After the bubbles rise further and the combustible gas is ejected to the ground, the pressure in the upper part of the groundwater layer is lowered, and the head of the surrounding groundwater layer is also lowered accordingly. There is no other phenomenon in which the head of the groundwater layer changes rapidly.

  It should be noted that the process in which combustible gas dissolved in the groundwater layer erupts to the ground due to an earthquake and the change in the head of the groundwater layer in each process vary depending on the conditions of the geological structure in which the groundwater layer exists, but are generally as described above. is there.

  Based on the above knowledge, according to this configuration, the head of the groundwater layer is detected by the head detection means, and the abnormality of the head change of the groundwater layer at the time of the earthquake is detected by the abnormality judgment means based on the detected head change speed. judge. As described above, the phenomenon in which the head of the groundwater layer suddenly changes occurs only due to the liberation and rise of combustible gas from the groundwater layer during an earthquake. Therefore, when it is determined that the head change of the groundwater layer is abnormal, it is possible to effectively predict that the combustible gas is ejected to the ground with the occurrence of the earthquake by the prediction means. That is, by catching the head of the groundwater layer containing the combustible gas over time, it is possible to predict the ejection of the combustible gas to the ground effectively and easily.

  The invention according to claim 2 is the flammable gas ejection prediction apparatus according to claim 1, wherein the water head detecting means includes a sealed observation well embedded so as to penetrate into the groundwater layer, and a sealed observation well And a pressure gauge for detecting the pressure in the sealed observation well as a head of the groundwater layer, and the closed observation well is connected to a pipe whose upper end is closed and a lower end of the pipe And a strainer that is provided.

  According to this configuration, the water head detection means includes a sealed observation well embedded so as to penetrate into the groundwater layer, and a pressure gauge provided inside the sealed observation well. The head of the groundwater layer is detected.

  Since the sealed observation well is buried so as to penetrate into the groundwater layer, the head of the groundwater layer and the head of the groundwater in the sealed observation well coincide with each other. When the head of the groundwater layer rises due to the occurrence of an earthquake, a pressure difference occurs between the groundwater layer and the groundwater in the sealed observation well, and the groundwater in the groundwater layer flows into the sealed observation well through the strainer. Along with this, the groundwater head in the sealed observation well rises. Specifically, the groundwater level and water pressure in the sealed observation well rise. Since the upper end of the pipe constituting the sealed observation well is closed, the sealed air in the sealed observation well is compressed and the pressure increases as the groundwater level in the sealed observation well rises. The increase in pressure stops when the air pressure of the sealed air and the head of the groundwater layer are in equilibrium. That is, at the time of an earthquake, the water head of the groundwater layer can be detected by detecting the pressure in the sealed observation well with a pressure gauge.

  In addition, according to this configuration, since the upper end of the pipe constituting the sealed observation well is closed, the pressure of the sealed air in the sealed observation well is maintained even in a situation where the head of the groundwater layer rises greatly during an earthquake. As a result, the rise of the water level in the closed observation well can be suppressed, and as a result, the amount of groundwater flowing into the closed observation well through the strainer is suppressed and the inflow time is shortened. Change can be captured.

  The invention according to claim 3 is the flammable gas ejection predicting apparatus according to claim 1, wherein the water head detecting means includes an open type observation well embedded so as to penetrate into the groundwater layer, and an open type observation well A water level gauge that detects the water level in the open observation well as a head of the groundwater layer, and the open observation well is connected to a pipe having an open top and a lower end of the pipe And a strainer that is provided.

  According to this configuration, the water head detection means is composed of an open type observation well buried so as to penetrate into the groundwater layer and a water level gauge provided inside the open type observation well. The head of the groundwater layer is detected.

  The open observation well is buried so as to penetrate into the groundwater layer, and the upper end of the pipe constituting the open observation well is open, so in normal times the head of the groundwater layer and the groundwater in the open observation well The water levels (heads) are the same. When the head of the groundwater layer rises due to the occurrence of an earthquake, a pressure difference occurs between the groundwater layer and the groundwater in the open observation well, and the groundwater in the groundwater layer flows into the open observation well through the strainer. Along with this, the groundwater level (head) in the open observation well also rises. The rise of the water level (head) stops when the water level (head) in the open observation well and the head of the groundwater layer are in equilibrium. That is, at the time of an earthquake, the water head in the open observation well can be detected by detecting the water level with a water level gauge.

  In addition, according to this configuration, the upper space in the open observation well is connected to the air in the atmosphere, and unlike the ground, in the open observation well, the flammable gas is not restricted and freely flows out.・ Inflow is secured. Therefore, the flammable gas released from the groundwater rises in the open observation well and is directly released into the atmosphere before being ejected from the ground toward the ground while being restrained in the ground. Therefore, by promptly confirming the ejection of the combustible gas in the open type observation well, the ejection of the combustible gas from the ground can be predicted in advance.

  The invention according to claim 4 is the combustible gas ejection prediction device at the time of the earthquake according to claim 3, and is connected to a discharge duct connected to the upper end of the pipe via a connection part in order to discharge the combustible gas. And a groundwater discharge mechanism for discharging the groundwater inside the open type observation well that is ejected together with combustible gas during an earthquake to the outside.

  According to this configuration, the discharge duct connected to the upper end of the pipe can positively discharge and release the flammable gas released from the groundwater layer, and suppress the flammable gas from being directly ejected to the ground. be able to.

  In addition, when groundwater is jetted into the observation well together with combustible gas, the groundwater is discharged to the outside by the groundwater discharge mechanism provided at the connection between the pipe and the discharge duct. Therefore, the combustible gas can be discharged more smoothly from the discharge duct.

  The invention according to claim 5 is the combustible gas ejection predicting device according to claim 4, wherein the discharge duct rises higher than the height of the building when a building is installed nearby. It is characterized by that.

  According to this configuration, since the discharge duct stands higher than the height of the nearby building, flammable gas such as methane that is lighter than air in the atmosphere is discharged from the discharge duct to a position higher than the building, Furthermore, it diffuses upward. Therefore, the risk of explosion of combustible gas in the building can be reduced.

  According to a sixth aspect of the present invention, in the flammable gas ejection prediction device at the time of an earthquake according to any one of the first to fifth aspects, when a flammable gas ejection is predicted by the prediction means, it is supplied to a nearby building. The power supply device further includes a power cut-off device that cuts off the power, and an alarm device that informs the surroundings that the ejection of the combustible gas is predicted.

  According to this configuration, when the flammable gas is predicted to be ejected, the power supply to the nearby building is interrupted by the power interrupt device, so that the electrical equipment in the building becomes an ignition source and is combustible. It is possible to prevent the explosive gas from exploding and the fire due to the ignition of the combustible gas.

  In addition, when a flammable gas blowout is predicted, a warning issued by the warning device will inform people around the flammable gas blowout. Damage caused by can be reduced.

It is a figure which shows roughly the 1st combustible gas ejection prediction apparatus by embodiment with the disaster prevention system to which this is applied. It is a figure which shows roughly the 2nd combustible gas ejection prediction apparatus by embodiment with the disaster prevention system to which this is applied. It is a figure which shows roughly the cross section of the connection part of a 2nd combustible gas ejection prediction apparatus. It is a figure which shows roughly the mechanism of the groundwater discharge | emission of a connection part.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  The 1st combustible gas ejection prediction apparatus 1 by this embodiment and the disaster prevention system to which this is applied are demonstrated, referring FIG.

  The first combustible gas ejection prediction device 1 includes a sealed observation well 2, a pressure gauge 21, and a data processing device 201. The sealed observation well 2 is buried underground, and the stratum structure is composed of a sediment layer 101, a hardly permeable layer 102, and an aquifer 103 in order from the surface layer side. The groundwater in the aquifer 103 is pressured groundwater in which a combustible gas such as methane is dissolved and is filled with the aquifer 103 and receiving pressure. Therefore, the groundwater head in the aquifer 103 is represented by the sum of the position head (water level) and the pressure head (pressure).

  The sealed observation well 2 is arranged in the vicinity of the building 205, and includes a strainer tube 11, a circular tube 12 connected to the upper end of the strainer tube 11, and a sealed lid 13 that closes the upper end of the circular tube 12. It is configured. A plurality of circular or elliptical holes for taking in groundwater are formed almost uniformly in the peripheral wall of the strainer pipe 11 over the entire wall. The connection position between the strainer pipe 11 and the circular pipe 12 is lower than the upper end of the aquifer 103. Thereby, the groundwater in the aquifer 103 can be reliably taken into the closed observation well 2 through the hole of the strainer pipe 11.

  The connection position is preferably as high as possible under the condition that it is lower than the upper end of the aquifer 103, and the lower end of the strainer pipe 11 is preferably as deep as possible. Thereby, the surface area of the strainer pipe 11 can be increased, the groundwater uptake range in the aquifer 103 can be widened, and the groundwater can be taken into the sealed observation well 2 more quickly. In addition, a filter for preventing clogging with soil particles may be provided on the outer peripheral portion of the strainer tube 11.

  A pressure gauge 21 for detecting the air pressure of the sealed air A in the sealed observation well 2 is provided at the lower end of the inner surface of the sealed lid 13. The pressure gauge may be of a type that detects the water pressure of groundwater in the sealed observation well 2, or both may be used in combination.

  The data processing device 201 is constituted by a microcomputer or the like, and the output terminal of the pressure gauge 21 is connected to the input side, and a detection signal representing the air pressure of the sealed air A is input. The data processing device 201 executes a process for predicting the ejection of the combustible gas in accordance with the input detection value of the pressure gauge 21 in accordance with a predetermined control program.

  Further, an alarm device 202 for warning the predicted ejection of combustible gas is connected to the output side of the data processing device 201, and a power cutoff device 203 for shutting off the power supply to the building 205 is also provided. Connected.

  Next, a method for predicting the ejection of combustible gas during an earthquake using the first combustible gas ejection prediction device 1 having the above-described configuration and the operation of the disaster prevention system according to the result will be described.

  The pressure of the sealed air A in the sealed observation well 2 is always detected by the pressure gauge 21. The head of the groundwater (water level + pressure) in the aquifer 103 changes gradually depending on the rainfall situation, the situation of pumping in the vicinity, changes in the tide level, and others. Along with this, the detected value of the pressure gauge 21 also changes gradually. The detected value of the pressure gauge 21 is captured and stored in the data processing device 201.

  When a relatively large earthquake occurs from this state, the flammable gas dissolved in the groundwater in the aquifer 103 due to the large vibration is released from the groundwater and becomes bubbles. The generated bubbles receive buoyancy from the groundwater and rise in the aquifer 103 toward the ground. The rising bubbles are blocked by the poorly permeable layer 102 and accumulate near the boundary between the hardly permeable layer 102 and the aquifer 103. As the accumulated bubbles increase, the water head (pressure) of groundwater in the aquifer 103 increases rapidly. As a result, a pressure difference is generated between the groundwater in the aquifer 103 and the sealed observation well 2, and the groundwater flows into the sealed observation well 2 through the strainer pipe 11, thereby The sealed air A is compressed and its pressure increases rapidly. The data processing device 201 calculates the pressure change rate of the sealed air A detected by the pressure gauge 21 and an abnormality in the pressure change occurs when the calculated pressure change rate exceeds a predetermined threshold value. It is determined that By this abnormality determination, it is possible to predict the possibility that the combustible gas is ejected to the ground.

  At this stage, the data processing device 201 activates the alarm device 202 to alert the people around it, and activates the power shut-off device 203 to supply power to the building 205 and the surrounding electrical equipment. By shutting off, it is possible to prevent the flammable gas from exploding due to the power equipment and other fire as an ignition source, and the fire from being caused.

  Thereafter, when the pressure of the aquifer 103 further increases and reaches the limit, the hardly water-permeable layer 102 cracks, and the accumulated bubbles are caused by the pressure difference generated between the top and bottom of the hardly water-permeable layer 102. Ascend toward the earth and sand layer 101 at a stretch. At the same time, the groundwater also rises at a stretch through the crack toward the sediment layer 101. As a result, the pressure in the aquifer 103 that has increased rapidly decreases, and the detected value of the pressure gauge 21 that has increased also decreases rapidly.

  On the other hand, groundwater and combustible gas erupt on the ground. In some cases, sand or the like contained in the earth and sand layer 101 is ejected to the ground together with groundwater and combustible gas.

  As described above, according to the present embodiment, when the pressure value detected by the pressure gauge 21 is taken into the data processing device 201 and the head of groundwater in the aquifer 103 changes very rapidly, it is determined as abnormal. To do. Therefore, by this abnormality determination, it is possible to predict the possibility of flammable gas ejection to the ground during an earthquake with a very high probability.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. In the present embodiment, the sealed observation well 2 is embedded so as to penetrate into the aquifer 103, targeting the ground composed of the earth and sand layer 101, the hardly permeable layer 102, and the aquifer 103 in order from the surface layer side. Yes. For example, when the ground is composed of a sediment layer and a hardly water-permeable layer in order from the surface layer side, the sealed observation well 2 may be embedded so as to penetrate the sediment layer. In addition, if there are a poorly permeable layer and a second aquifer (groundwater layer) below the aquifer, the sealed observation well 2 is buried so as to penetrate the second aquifer. Also good.

  The 2nd combustible gas ejection prediction apparatus 3 by this embodiment and the disaster prevention system to which this is applied are demonstrated, referring FIG.

  Since the configuration of the second combustible gas ejection prediction device 3 has many portions in common with the first combustible gas ejection prediction device 1, the description of the common portions will be omitted, and differences will be mainly described.

  The second combustible gas ejection prediction device 3 includes an open observation well 4, a water level gauge 22, and a data processing device 201. The water level gauge 22 is arranged in the ground water in the open type observation well 4. In the present embodiment, the water level gauge 22 is a water pressure type that detects the water pressure and obtains the water level using the fact that this water pressure is proportional to the water depth. For example, an ultrasonic water level meter that emits ultrasonic waves to the water surface, detects the propagation time of the ultrasonic waves reflected from the water surface, and converts them to the water level may be used. A float-type water level meter may be used to obtain the water level by floating a float on the surface and mechanically transmitting a change in the water level to a rotating shaft in the float. Alternatively, when a plurality of reed switches are arranged at predetermined intervals in the observation well and a float with a built-in permanent magnet follows the water level change and moves up and down in the pipe, the reed switch corresponding to the water level is energized by magnetic force. It is also possible to use an underwater type water level gauge that obtains the water level by using the above. These may be used in combination.

  The open-type observation well 4 is disposed above the strainer tube 11 disposed in the aquifer 103, the circular tube 12 connected to the upper end of the strainer tube 11, and the circular tube 12 so as to allow the combustible gas to flow upward. A discharge duct 15 for discharging, and a connecting portion 14 for connecting the circular pipe 12 and the discharge duct 15 are configured. The discharge duct 15 is composed of a circular pipe with an open upper end, and rises higher than the height of the building 205.

  As a result, combustible gas such as methane, which is lighter than air in the atmosphere, is released into the atmosphere from the opening at the upper end of the discharge duct 15 and diffuses. Therefore, the risk of explosion and fire of combustible gas in the building 205 and its surroundings can be reduced.

  Further, since the combustible gas rising in the open type observation well 4 can be directly confirmed from the opening at the upper end of the discharge duct 15, the ejection of the combustible gas from the ground can be predicted more accurately. .

  As shown in FIG. 3, the connection portion 14 is provided with a groundwater discharge mechanism 30. The groundwater discharge mechanism 30 includes a connection pipe 33, a diffusion prevention weir 31, and a storage weir 32, and these components are provided concentrically with the circular pipe 12 and the discharge duct 15. The connecting pipe 33 has the same diameter as the circular pipe 12 and the discharge duct 15 and is connected so as to communicate the both 12 and 15. A plurality of vertically long slits 34 are formed at equal intervals along the circumferential direction in the upper part of the peripheral wall of the connection pipe 33.

  The diffusion prevention weir 31 has a short tubular shape with a bottom, and has a bottom portion 31a and a peripheral wall portion 31b. The bottom 31a is a donut plate having a diameter larger than that of the discharge duct 15, is watertightly provided at the upper end of the outer surface of the connection pipe 33, and extends horizontally outward. The peripheral wall portion 31 b extends downward from the periphery of the bottom portion 31 a and substantially covers the upper half portion of the connection pipe 33 including the slit 34.

  The storage weir 32 is also a short tubular shape with a bottom, and has a bottom portion 32a and a peripheral wall portion 32b. The bottom portion 32a is a donut plate-like shape having a larger diameter than the bottom portion 31a of the diffusion preventing weir 31 and is provided in a watertight manner at the lower end portion of the outer surface of the connection pipe 33 and extends horizontally outward. The peripheral wall portion 32 b extends upward from the peripheral edge of the bottom portion 32 a and substantially covers the lower half portion of the peripheral wall portion 31 b of the diffusion preventing weir 31.

  In the event of an earthquake, combustible gas is spouted into the open observation well 4 together with groundwater, and when the groundwater level in the open observation well 4 becomes higher than the position of the connection portion 14, as shown in FIG. The groundwater passes through the slit 34 of the connecting pipe 33 and accumulates in the storage weir 32.

  When the amount of groundwater further increases, the groundwater accumulated in the storage weir 32 overflows the storage weir 32. As shown in FIG. 4C, since the slit 34 is closed by the groundwater accumulated in the storage weir 32, the release of combustible gas from the slit 34 into the atmosphere can be prevented.

  The method for predicting the ejection of combustible gas at the time of an earthquake using the second combustible gas ejection prediction device 3 is substantially the same as the method for predicting the ejection using the first combustible gas ejection prediction device 1 described above. Omitted.

  In Examples 1 and 2, both the alarm device 202 and the power shut-off device 203 are provided in the first and second combustible gas ejection prediction devices 1 and 3, but only one of them may be provided. Or both may be omitted.

  Further, in the first embodiment, the single first combustible gas ejection predicting device 1 is used, and in the second embodiment, the single second combustible gas ejection predicting device 3 is used. May be used. Furthermore, Example 1 and Example 2 may be combined, and a plurality of first combustible gas ejection prediction devices 1 and a plurality of second combustible gas ejection prediction devices 3 may be used in combination.

  Further, a gas detection device (not shown) for detecting the concentration of flammable gas such as methane is disposed in the discharge duct 15 to detect the concentration of the flammable gas discharged from the discharge duct 15, and the data processing device. An abnormality in groundwater head change in the aquifer 103 by taking into account both the detection result of the water level in the open observation well 4 and the detection result of the concentration of combustible gas with a predetermined control program. May be determined. As a result, a bubbly flow or slag flow is generated in the groundwater in the open type observation well 4 due to a large shaking caused by an earthquake, causing unexpected turbulence in the water level. Can be predicted.

DESCRIPTION OF SYMBOLS 1 1st combustible gas ejection prediction apparatus 2 Sealed observation well 3 Second flammable gas ejection prediction apparatus 4 Open type observation well 11 Strainer pipe (strainer)
12 circular tube 13 sealing lid 14 connection part
15 Discharge duct 21 Pressure gauge (head detection means)
22 Water level gauge (water head detection means)
30 Groundwater discharge mechanism 31 Diffusion prevention weir 31a Bottom of diffusion prevention weir
31b Perimeter wall of diffusion prevention weir
32 storage weir 32a bottom of storage weir 32b peripheral wall of storage weir 33 connecting pipe 34 slit 101 sediment layer 102 impermeable layer 103 aquifer 201 data processing device (abnormality determination means, prediction means)
202 Alarm device 203 Power interruption device 205 Building
A Sealed air

Claims (6)

A head detection means for detecting the head of the groundwater layer in which the combustible gas is dissolved;
Based on the change rate of the head detected by the head detection means, an abnormality determination means for determining an abnormality of the head change of the groundwater layer at the time of an earthquake,
Predicting means for predicting that the combustible gas is ejected to the ground with the occurrence of an earthquake when it is determined by the abnormality determining means that the head change of the groundwater layer is abnormal,
A combustible gas ejection predicting device at the time of an earthquake characterized by comprising: The water head detection means includes a sealed observation well embedded so as to penetrate into the groundwater layer,
A pressure gauge that is provided inside the sealed observation well and detects the pressure in the sealed observation well as a head of the groundwater layer;
Have
The sealed observation well has a tube whose upper end is closed;
A strainer connected to the lower end of the tube;
It is characterized by having
The combustible gas ejection prediction apparatus at the time of the earthquake of Claim 1. The water head detection means includes an open type observation well embedded so as to penetrate into the groundwater layer,
A water level meter that is provided inside the open observation well and detects a water level in the open observation well as a head of the groundwater layer;
Have
The open observation well has a tube with an open upper end,
A strainer connected to the lower end of the tube;
It is characterized by having
The combustible gas ejection prediction apparatus at the time of the earthquake of Claim 1. A discharge duct connected via a connection to the upper end of the pipe for discharging flammable gases;
A groundwater discharge mechanism for discharging the groundwater in the open observation well, which is provided in the connection portion and is ejected together with combustible gas during an earthquake,
Further comprising:
The combustible gas ejection prediction apparatus at the time of the earthquake of Claim 3. The discharge duct is characterized in that when a building is installed in the vicinity, it rises higher than the height of the building,
The combustible gas ejection prediction apparatus at the time of the earthquake of Claim 4. A power interruption device that cuts off the supply of power to nearby buildings when a flammable gas ejection is predicted by the prediction means, and an alarm to inform the surroundings that a flammable gas ejection is predicted Equipment,
Further comprising:
The combustible gas ejection prediction apparatus at the time of the earthquake of Claim 1 to 5.

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