JP2005047682A - Leakage preventive method for underground storage and underground storage facility using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage preventive method for an underground storage for reducing construction cost. <P>SOLUTION: Pressure in the underground storage 1 is lowered and maintained to be lower than pore water pressure of surrounding ground 2 to prevent a stored material 3 in the underground storage 1 from leaking to the surrounding ground 2. The pressure in the underground storage 1 is maintained to be lower than the pore water pressure of the ground outside a low permeable region so that hydraulic gradient of the low permeable region of the ground surrounding the underground storage 1 can have a value not less than the value for allowing the stored material 3 to stay in the underground storage 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a leakage prevention method for an underground storage and an underground storage facility using the same. More specifically, the present invention relates to a leak prevention method for an underground storage using the pressure difference between the inside and outside of the underground storage, and an underground storage facility using the same.

  There are underground storage facilities that store liquid combustible fuel such as oil and LPG in tunnels and cavities provided in the ground. A conventional underground storage facility is shown in FIGS. An artificial water sealing tunnel 102 is provided above the underground storage 101, and by making the groundwater level 104 in the tunnel 102 higher than the groundwater level 105 of the ground where the underground storage 101 is provided, The pore water pressure in the ground around the underground storage 101 was increased to prevent the stored matter 103 in the underground storage 101 from leaking to the surrounding ground. The artificial water sealing tunnel 102 has a large number of branch tunnels 102 a, and the pore water pressure in the ground around the underground storage 101 is uniformly increased.

Miyanaga, Fukuhara: Regarding the design of underground oil storage base, 219, 63-74, 1989

  However, in the method for preventing leakage of the underground storage 101 that increases the pore water pressure in the surrounding ground of the underground storage 101, it is necessary to dig a large number of water sealing tunnels 102 and 102a in addition to the underground storage 101, resulting in a great cost for construction. It was hanging.

  An object of the present invention is to provide an underground storage facility leakage prevention method and an underground storage facility using the same, which can be reliably prevented from leaking stored items at a low construction cost.

  In order to achieve such an object, the leakage prevention method for an underground storage according to claim 1 maintains the pressure in the underground storage by lowering the pressure in the underground storage to maintain the pressure lower than the pore water pressure of the surrounding ground. This prevents leakage to the ground.

  Therefore, the force in the direction in which groundwater flows into the underground storage due to the pressure difference between the inside and outside of the underground storage is generated, and leakage of stored items can be prevented.

  The leakage prevention method for an underground storage according to claim 2 is such that the hydrodynamic gradient of the low-permeability region of the ground surrounding the underground storage is greater than or equal to a value capable of retaining the storage in the underground storage. The pressure in the storage is maintained at a pressure lower than the pore water pressure of the ground outside the low water permeability region.

  When a space serving as a storage is provided in the basement, a low-permeability region is formed on the surrounding ground so as to surround the underground storage. In the low-permeability area, groundwater does not flow easily, and therefore the hydraulic gradient is larger than in other areas. By adjusting the pressure difference between the pressure in the underground storage and the pore water pressure in the surrounding ground, the hydraulic gradient in the low water permeability region can be adjusted.

  Here, in order to reliably prevent the leakage of stored items from the underground storage, the movement of a value greater than the value that can hold the stored material in the underground storage around the underground storage (hereinafter referred to as the containable value). A water gradient should be generated. When generating a dynamic gradient greater than the confinable value around the underground storage, it is most efficient to set the dynamic gradient in the low permeability region to a value greater than the confinable value. This is because the hydraulic gradient in the low water permeability region is larger than the hydraulic gradient in other parts. In other words, by reducing the pressure in the underground storage so that the hydraulic gradient in the low water permeability area is greater than or equal to the confinable value, the hydraulic gradient having a value that is greater than or equal to the confinable value around the underground storage with the smallest reduction width. Can be generated.

  In addition, as in the method for preventing leakage of underground storage according to claim 3, by opening the underground storage to the ground at a position lower than the groundwater level of the ground where the underground storage is provided, the pressure in the underground storage is reduced. The water pressure may be maintained at a pressure lower than the pore water pressure of the surrounding ground, and the groundwater level in the communication passage between the underground storage and the ground is set underground as in the method for preventing leakage of the underground storage according to claim 4. By lowering the groundwater level of the ground where the storage is provided, the pressure in the underground storage may be maintained at a pressure lower than the pore water pressure of the surrounding ground. The underground storage leakage prevention method according to claim 3 is suitable for application to, for example, an underground storage provided in a mountainous area, and the underground storage leakage prevention method according to claim 4 is provided, for example, in a plain area. Suitable for underground storage applications.

  Furthermore, the underground storage facility according to claim 5 includes an underground storage provided in the ground, and pressure maintaining means for maintaining a pressure lower than the pore water pressure of the surrounding ground by lowering the pressure in the underground storage. is there.

  Therefore, a force in a direction in which groundwater flows into the underground storage due to a pressure difference between the inside and outside of the underground storage is generated, and leakage of stored items in the underground storage can be prevented.

  Further, in the underground storage facility according to claim 6, the pressure maintaining means is configured so that the hydraulic gradient in the low water permeability region of the ground surrounding the underground storage is greater than or equal to a value capable of retaining the storage in the underground storage. The pressure in the underground storage is maintained at a pressure lower than the pore water pressure of the ground outside the low water permeability region.

  Therefore, the pressure drop in the underground storage can be minimized, and a hydraulic gradient having a value greater than the confinable value can be generated around the underground storage.

  Further, as in the underground storage facility according to claim 7, the pressure maintaining means may be a communication passage that opens the underground storage to the ground at a position lower than the groundwater level of the ground where the underground storage is provided. In addition, as in the underground storage facility according to claim 8, the pressure maintaining means drains the groundwater level in the communication passage between the underground storage and the ground to lower than the groundwater level of the ground where the underground storage is provided. It may be a device. The underground storage facility according to claim 7 is suitable for construction in, for example, a mountainous area, and the underground storage facility according to claim 8 is suitable for, for example, construction in a plain or the like.

  Thus, in the underground storage leak prevention method according to the first aspect of the present invention, it is possible to reliably prevent leakage of stored items by utilizing the pressure difference between the inside and outside of the underground storage. In addition, since the pressure in the underground storage is controlled to create a pressure difference, there is no need to provide a water sealing tunnel as in the case of controlling the pressure outside the underground storage, greatly reducing construction costs. Can do.

  Further, in the underground storage leak prevention method according to claim 2, since the pressure decrease in the underground storage can be minimized, the amount of groundwater discharged in the underground storage can be reduced, and the storage cost can be reduced. be able to.

  In addition, as in the method for preventing leakage of underground storage according to claim 3, by opening the underground storage to the ground at a position lower than the groundwater level of the ground where the underground storage is provided, the pressure in the underground storage is reduced. It may be possible to maintain the pressure lower than the pore water pressure of the surrounding ground. As in the method for preventing leakage of the underground storage according to claim 4, the underground storage stores the groundwater level in the connecting passage between the underground storage and the ground. You may make it maintain the pressure in an underground storage tank in the pressure lower than the pore water pressure of a surrounding ground by lowering the groundwater level of the ground provided. By either method, the pressure in the underground storage can be maintained at a low pressure at a low cost. Further, the underground storage leakage prevention method according to claim 3 can be applied to, for example, an underground storage provided in a mountainous area, and the underground storage leakage prevention method according to claim 4 is provided, for example, in a plain area. Can be applied to underground storage.

  Furthermore, in the underground storage facility according to claim 5, leakage of stored items can be surely prevented by utilizing a pressure difference between the inside and outside of the underground storage. In addition, since the pressure maintaining means controls the pressure in the underground storage in order to generate a pressure difference, it is not necessary to provide a tunnel for water sealing as in the case of controlling the pressure outside the underground storage, thereby reducing the construction cost. It can be greatly reduced.

  In the underground storage facility according to the sixth aspect, the pressure reduction in the underground storage can be minimized, so that the storage cost can be reduced.

  Further, as in the underground storage facility according to claim 7, the pressure maintaining means may be a communication passage that opens the underground storage to the ground at a position lower than the groundwater level of the ground where the underground storage is provided. In addition, as in the underground storage facility according to claim 8, the pressure maintaining means drains the groundwater level in the communication passage between the underground storage and the ground to lower than the groundwater level of the ground where the underground storage is provided. It may be a device. The underground storage facility according to claim 7 is suitable for construction in, for example, a mountainous area, and the underground storage facility according to claim 8 is suitable for, for example, construction in a plain or the like.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.

  FIG. 1 shows an example of an embodiment of an underground storage facility to which the present invention is applied. 1-4, the arrow around the underground storage 1 indicates the flow of groundwater. The underground storage facility 1 uses the underground storage facility 1 to prevent leakage of the underground storage facility 1 by lowering the pressure in the underground storage facility 1 to maintain a pressure lower than the pore water pressure of the surrounding ground 2 and surrounding the stored items 3 in the underground storage facility 1. This prevents leakage to the ground 2. That is, the underground storage facility of the present invention includes an underground storage 1 provided in the ground, and pressure maintaining means 4 for maintaining the pressure in the underground storage 1 at a pressure lower than the pore water pressure of the surrounding ground 2 by lowering the pressure in the underground storage 1. ing.

  By maintaining the pressure in the underground storage 1 at a pressure lower than the pore water pressure of the surrounding ground 2, the groundwater flows into the underground storage 1 from the surrounding ground 2, and this flow can prevent the stored material 3 from leaking. .

  The store 3 is a liquid combustible fuel such as petroleum or LPG. However, it is not limited to liquid combustible fuel, but may be other liquid storage, or solid or gaseous storage. Moreover, industrial waste, radioactive waste, etc. may be sufficient.

  The underground storage 1 is, for example, a tunnel or a cavity dug in a mountainous area. FIG. 2 schematically shows a cross section of the ground around the underground storage 1 and its pore water pressure. In the ground around the underground storage 1, there are a digging influence area 5 and a low water permeability area 6 outside the digging influence area 5. The excavation influence area 5 is an area where the ground is loosened by excavation, and has a thickness of several meters, for example. Further, the low water permeability region 6 is a region where the stress increases due to stress redistribution accompanying excavation and the water permeability coefficient decreases. Around the underground storage 1, an excavation-affected area 5 and a low water-permeable area 6 exist substantially concentrically.

  When the pressure in the underground storage 1 is lowered below the pore water pressure of the surrounding ground 2, the pore water pressure greatly decreases in the low water permeability region 6 as indicated by an arrow A in FIG. For this reason, a large force is generated in the low water permeability region 6 in the direction in which groundwater flows into the underground storage 1, and the stored matter 3 is retained in the underground storage 1 by the flow of groundwater due to this force to prevent leakage. it can. That is, since the permeability coefficient of the low water permeable region 6 is small, the rate of decrease in pore water pressure (hydrodynamic gradient) in the low water permeable region 6 becomes larger than that of the other surrounding ground 2, and the leakage of the stored product 3 is made use of this. Can be prevented.

  The pressure maintaining means 4 is such that the hydrodynamic gradient of the low-permeability region 6 of the ground surrounding the underground storage 1 becomes a value greater than or equal to a value (hereinafter referred to as a containable value) that can keep the storage 3 in the underground storage 1. In addition, the pressure in the underground storage 1 is maintained at a value lower than the pore water pressure of the ground outside the low water permeability region 6. In the present embodiment, the pressure maintaining means 4 is constituted by a communication passage (access tunnel) 7 that opens the underground storage 1 to the ground at a position lower than the groundwater level of the ground where the underground storage 1 is provided.

  The confinable value of the dynamic water gradient is, for example, 0.8 (the water head changes by 0.8 m with respect to a 1 m position change of the ground). If the dynamic water gradient is at least 0.8 or more, even if the stored product 3 is in a gaseous state, leakage of the stored product 3 can be prevented by the force with which groundwater flows into the underground storage 1. Since the gaseous storage product 3 is most likely to leak, if the gaseous storage product 3 can be reliably prevented from leaking, the liquid storage product 3 and the solid storage product 3 are also reliably prevented from leaking. be able to.

  Since the hydrodynamic gradient of the low water permeable region 6 is determined by the pressure difference between the inside and the outside, the pressure in the underground storage 1 is lowered with respect to the pore water pressure of the ground outside the low water permeable region 6, and the width of the decrease is appropriate. By setting to, the hydraulic gradient of the low water permeability region 6 can be adjusted. In the present invention, the pressure in the underground storage 1 is adjusted so that the hydrodynamic gradient of the low water permeability region 6 becomes a value that is greater than or equal to the containable value (0.8). That is, when the pressure in the underground storage 1 is P, the pressure difference between the pressure in the underground storage 1 and the pore water pressure outside the low water permeable region 6 becomes T, and when this pressure difference is T, the low water permeable region 6 If the hydrodynamic gradient of becomes 0.8, the pressure in the underground storage 1 is adjusted to P.

  Here, in order to surely prevent the leakage of the stored product 3 from the underground storage 1, it is only necessary to generate a hydraulic gradient of 0.8 or more around the underground storage 1. Alternatively, a hydrodynamic gradient of 0.8 or more may be generated. However, as is clear from FIG. 2, the hydraulic gradient in the low water permeability region 6 is larger than the hydraulic gradient in other regions. For this reason, it is most efficient to make the hydraulic gradient of the low water permeability region 6 0.8 or more. That is, by managing the pressure in the underground storage 1 so that the hydraulic gradient in the low water permeable region 6 is 0.8 or more, the amount of pressure decrease in the underground storage 1 can be minimized, and the most economical Is.

  Since the communication passage 7 opens to the ground at a position lower than the groundwater level 9 of the ground where the underground storage 1 is provided, the groundwater flowing into the underground storage 1 and the communication passage 7 from the surrounding ground 2 is connected to the ground. It flows out from the opening of 7 to the ground. By adjusting the height at which the communication passage 7 opens to the ground, the ground water level 10 in the underground storage 1 and the communication passage 7 can be changed, and the pressure in the underground storage 1 can be set. That is, the communication passage 7 is opened to a height at which the pressure in the underground storage 1 becomes P.

  In the vicinity of the opening of the communication passage 7, a treatment device 8 for the groundwater that has flowed out is provided. The storage device 3 and contaminants contained in the groundwater are removed by the processing device 8.

  In the above description, the pressure in the underground storage 1 is set to the pressure P at which the hydraulic gradient in the low water permeable region 6 becomes 0.8. However, in practice, it is preferable to provide a margin. That is, it is preferable to set the pressure in the underground storage 1 so that the hydraulic gradient in the low water permeability region 6 is 0.8 + α in consideration of the margin of α as the hydraulic gradient.

  Further, since the groundwater level 9 fluctuates, the opening of the communication passage 7 is provided at a position sufficiently lower than the position where the groundwater level 9 is lowest.

  As described above, according to the present invention, it is possible to reliably prevent leakage of the stored item 3 by using the pressure difference between the inside and outside of the underground storage 1. Moreover, since the pressure in the underground storage 1 is controlled to provide the pressure difference, it is not necessary to provide a water sealing tunnel as in the case of controlling the pressure outside the underground storage shown in FIG. Can be greatly reduced.

  Further, by opening the underground storage 1 to the ground at a position lower than the groundwater level 9 of the ground where the underground storage 1 is provided, the pressure in the underground storage 1 is set to a pressure lower than the pore water pressure of the surrounding ground 2. Since the water level is maintained, the water level 10 can be lowered by utilizing the natural overflow of the underground water in the underground storage 1 and the communication passage 7. For this reason, the pressure in the underground storage 1 can be maintained at a low pressure at low cost, which is economical.

  Furthermore, since the pressure in the underground storage 1 is adjusted (lowered) so that the hydraulic gradient in the low water permeability region 6 becomes a value that can be contained (0.8) or more, the pressure in the underground storage 1 The amount of lowering can be minimized. For this reason, since the amount of groundwater drainage can be reduced most and the processing amount of the processing apparatus 8 can be reduced most, the cost which maintains an installation can be made cheap.

  Moreover, not only when excavating the underground storage 1 newly, it is also possible to utilize an existing tunnel or the like. For example, underground spaces such as tunnels, road tunnels, and railway tunnels that are no longer necessary may be used as the underground storage 1. In this case, the construction cost can be further reduced.

  As described above, in the present invention, by managing the pressure in the underground storage 1 and the drainage of the groundwater, the leakage of the stored item 3 in the underground storage 1 can be surely prevented by utilizing the pressure difference of the groundwater. Can do.

  In the conventional geological disposal of high-level radioactive waste, the design is expected to prevent the leakage of stored materials from the permeability characteristics of metal, bentonite, and existing ground called artificial barriers and natural barriers. In such a geological disposal facility, it is difficult to reduce the pressure in the underground storage below the pore water pressure of the surrounding ground after the underground storage is completely filled and radioactive waste (stored material) is subjected to geological disposal. However, before the underground storage is completely filled, the drainage in the underground storage is performed at the time of operation at the stage where the stored items are carried into the underground storage. Therefore, even in geological disposal facilities, applying this leakage prevention method at the operation stage makes it possible to ensure multiple safety in addition to other safety designs and improve reliability. it can.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, when storing things that are lighter than water as the storage 3, for example, as shown in FIG. 3, a trap 11 is provided by lowering a part of the underground storage 1 or the communication passage 7, and the communication passage of the storage 3. It is preferable to prevent the outflow from 7.

  In the above description, the underground storage facility is provided in the mountainous area, but the underground storage facility may be provided in a place other than the mountainous area. For example, the example in the case of providing an underground storage facility in a plain part is shown in FIG. The pressure maintaining means 4 in this case is a drainage device that lowers the groundwater level 10 in the communication passage 7 between the underground storage 1 and the ground below the groundwater level 9 in the ground where the underground storage 1 is provided. That is, by lowering the groundwater level 10 in the underground storage 1 and the communication passage 7 to be lower than the groundwater level 9 in the ground in which the underground storage 1 is provided, the pressure in the underground storage 1 is made higher than the pore water pressure in the surrounding ground 2. Also try to keep it at a low pressure.

  The drainage device 4 is a pump, for example. By draining the ground water in the communication passage 7 and the underground storage 1 to the ground constantly by the drainage device 4, the water level 10 of the ground water in the communication passage 7 and the underground storage 1 can be lowered. Also in this example, since the pressure in the underground storage 1 is reduced and the groundwater flows into the underground storage 1 from the surrounding ground 2, the leakage of the storage 3 can be prevented by this flow as in the case described above. . In this example as well, wastewater from the drainage device 4 is treated by a treatment device (not shown) to remove the stored matter 3 and contaminants in the wastewater.

It is a conceptual diagram which shows an example of embodiment of the underground storage facility to which this invention is applied. It is a schematic diagram which shows the cross section of the ground around an underground storage, and its pore water pressure. It is a conceptual diagram which shows other embodiment of the underground storage facility to which this invention is applied. It is a conceptual diagram which shows other embodiment of the underground storage facility to which this invention is applied. It is a conceptual diagram which shows the conventional underground storage facility. It is a conceptual diagram which shows the cross section which follows the VV line | wire of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Underground storage 2 Periphery ground 3 Stored thing 4 Pressure maintenance means 6 Low-permeability area 7 Connecting passage

Claims (8)

  A method for preventing leakage of an underground storage, characterized in that the pressure in the underground storage is lowered to maintain a pressure lower than the pore water pressure of the surrounding ground to prevent leakage of stored items in the underground storage to the surrounding ground.   The pressure in the underground storage is set outside the low water permeable region so that the hydraulic gradient of the low water permeable region of the ground surrounding the underground storage is greater than or equal to a value capable of retaining the storage in the underground storage. 2. The method for preventing leakage of underground storage according to claim 1, wherein the pressure is maintained at a pressure lower than the pore water pressure of the ground.   Maintaining the pressure in the underground storage at a pressure lower than the pore water pressure of the surrounding ground by opening the underground storage to the ground at a position lower than the groundwater level of the ground where the underground storage is provided. The leak prevention method of the underground storage of Claim 1 or 2 characterized by the above-mentioned.   The pressure in the underground storage is lower than the pore water pressure in the surrounding ground by lowering the groundwater level in the communication passage between the underground storage and the ground below the groundwater level of the ground where the underground storage is provided. 3. The method for preventing leakage of underground storage according to claim 1 or 2, wherein   An underground storage facility comprising: an underground storage provided in the ground; and pressure maintaining means for maintaining a pressure lower than the pore water pressure of the surrounding ground by lowering the pressure in the underground storage.   The pressure maintaining means adjusts the pressure in the underground storage so that the hydrodynamic gradient of the low-permeability region of the ground surrounding the underground storage is equal to or greater than a value at which the stored matter can be retained in the underground storage. 6. The underground storage facility according to claim 5, wherein the underground storage facility is maintained at a pressure lower than the pore water pressure of the ground outside the low water permeability region.   The underground storage according to claim 5 or 6, wherein the pressure maintaining means is a communication passage that opens the underground storage to the ground at a position lower than the groundwater level of the ground where the underground storage is provided. Facilities. 6. The drainage device according to claim 5, wherein the pressure maintaining means is a drainage device that lowers a groundwater level in a communication passage between the underground storage and the ground to be lower than a groundwater level in a ground where the underground storage is provided. 6. Underground storage facility.

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