JP4986031B2 - Low temperature rock storage tank - Google Patents

Description

  The present invention relates to a low-temperature rock storage tank that uses a cavity excavated in the rock as a storage tank (tank) for storing a low-temperature fluid.

  This type of low temperature rock storage tank excavates a large-scale cavity in a stable rock mass, and makes the cavity function as a tank, and makes low temperature liquefied gas such as LPG, LNG, DME (dimethyl ether), or other low temperature liquid or low temperature. A gas is stored, and a so-called “freezing type” as shown in Patent Document 1 and a so-called “Patent Document 2” as shown in Patent Document 1 depending on a lining structure provided on the inner surface of the cavity. It is roughly classified into “membrane type”.

In a freezing low-temperature bedrock storage tank, the groundwater existing around the storage tank naturally freezes due to the low temperature below freezing point, and a stable freezing area is formed around the storage tank.Therefore, there are some cracks and gaps in the bedrock. Even if there is, it can be expected that the air tightness and liquid tightness of the storage tank will be secured stably. Therefore, it is possible to omit a special lining material and large-scale lining just by providing a simple support such as sprayed concrete and rock bolts on the inner surface of the cavity, and the construction is relatively simple and the construction cost is suppressed. This is advantageous in that
However, since such a freezing type is concerned that temperature cracks may occur in the rock if the storage temperature is extremely low, the storage temperature is limited to about −60 ° C. to −80 ° C. Therefore, the DME (boiling point) -25 ° C) and LPG (boiling point -42 ° C), which can be suitably used for fuels with relatively high storage temperatures, but is not suitable for cryogenic fluids such as LNG (boiling point -162 ° C). It is said that.

On the other hand, the membrane-type cryogenic rock storage tank was proposed to be applied to the storage of cryogenic particles such as LNG, and the membrane material ensures the airtightness and liquid-tightness required for the storage tank. It is. In this case, concretely, a lining with sprayed concrete and framed concrete is provided inside the cavity, and a lining with a multilayer structure is provided in which a membrane material is attached to the surface after a cold insulation material is provided on the inside. Therefore, although the structure is more complicated than that of the freezing type, it is difficult to be affected by the rock, and as with the freezing type, a freezing region is formed outside the storage tank. Since it can be considered as a next barrier, it is considered more advantageous in terms of reliability and stability.
JP-A-2005-195110 Japanese Unexamined Patent Publication No. 7-54366

By the way, a freezing low-temperature rock mass storage tank must have a good freezing area around the storage tank after operation, so even when excavating a cavity as a storage tank, the surrounding rock mass is always saturated. It needs to exist. In other words, when excavating a cavity, if the groundwater level of the surrounding rocks declines and becomes temporarily unsaturated, even if the groundwater level is subsequently recovered, it is difficult to recover to a fully saturated state. For this reason, it is assumed that a good freezing area is not formed around the storage tank even after operation, and there is a concern that the problem may remain in terms of reliability and safety required for this type of facility.
Therefore, when constructing a cryogenic low-temperature rock mass storage tank, prior to excavating the cavity as a storage tank, a large-scale water injection tunnel or water injection boring hole is pre-constructed above it, and from there to the surrounding rock mass in the cavity excavation area It is said that it is necessary to excavate the cavity while maintaining the surrounding rock mass in a saturated state by continuously performing a large amount of water injection as artificial groundwater recharge, which requires a lot of labor and cost. It was.

On the other hand, in the membrane-type low-temperature rock storage tank, it is advantageous to perform excavation by reducing the groundwater level around the cavity and making the surroundings dry during construction. In other words, in the case of the membrane type, a skeleton body is constructed in a cavity excavated in the ground, but if such construction is performed in a bedrock deeper than the groundwater level, a large amount of groundwater inflow occurs. In addition, large groundwater pressure acts as an external pressure on lining materials during construction, especially concrete and membrane materials, so it is extremely difficult to ensure construction accuracy and construction accuracy. is there.
Therefore, when constructing a membrane-type low-temperature rock storage tank, the ground is drained from the surrounding rocks to lower the groundwater level in the same way as in normal soil construction, and the cavity is excavated by lining the construction area as dry. It is necessary to construct. For this purpose, a large drainage tunnel and drainage borehole for collecting and draining water are pre-constructed below the area where the cavity should be excavated, and a large amount of groundwater is pumped from there to lower the groundwater level. It is necessary to keep the surroundings dry, and much labor and cost are required to implement such a large-scale drainage method. In addition, even with such construction methods, it is assumed that it cannot always be sufficiently dry depending on the condition of the bedrock, in which case the groundwater pressure acts on the lining and the workability is not good, and the construction quality may be adversely affected. There is.

  Also in the case of the membrane type, the groundwater level will eventually recover by stopping drainage from the surrounding rock mass after the start of low-temperature storage after completion of the storage tank, so that after operation, a frozen area will be formed around the storage tank. Although it is thought that it functions as a secondary barrier, as described above, the surrounding rock mass is desaturated during construction, so there is no guarantee that a good frozen area will be formed. Since it is assumed that sufficient functions cannot be expected as a barrier, it is necessary to design the lining in anticipation of such a function.

  In addition, after the storage tank is completed, it cools down in a short time and starts cold storage, but if the area around the storage tank is not completely unsaturated, a large groundwater pressure is applied locally or the area is expanded by freezing expansion. Concerns about abnormal cracks in the rock cannot be completely ruled out, and in order to ensure structural stability and reliability, it is necessary to eliminate the adverse effects of groundwater pressure and freezing expansion as much as possible. It is thought that there is.

In Patent Document 1, water is circulated in a water-sealed boring provided in a bedrock above the storage tank for the purpose of preventing the frozen region formed around the storage tank from reaching the surface area. It is disclosed that the surrounding ground is maintained above the freezing temperature. Patent Document 2 discloses that a surrounding pipe rock is prevented from being frozen by a heating pipe as a well-known technique in a general underground tank for LNG.
If such anti-freezing method is applied to the surrounding rock mass of membrane type low-temperature rock mass storage tank, it is thought that the adverse effect on the lining due to freezing and expansion can be prevented. No method has been proposed.

  In view of the above circumstances, the present invention can effectively eliminate the adverse effects of receiving groundwater pressure from the surrounding rock mass and the freezing and expansion of the surrounding rock mass, and sufficiently improve the structural stability and reliability. An object of the present invention is to provide a membrane-type low-temperature rock storage tank having an effective and suitable structure.

  The present invention is a membrane type in which a cover made of sprayed concrete, reinforced concrete, cold insulation material, membrane material is formed on the surface of a cavity excavated in the rock, and the internal space is used as a storage tank for storing a cryogenic fluid. A low-temperature bedrock storage tank with a drainage channel network for collecting and draining groundwater from the surrounding bedrock in the sprayed concrete, and circulating warming media such as hot water and brine in the concrete By burying a heated pipeline network for maintaining the concrete, sprayed concrete and surrounding rock mass above the freezing temperature, and placing the heated pipeline network on the inside of the drain network It is characterized by becoming.

In the present invention, a drainage network that excavates a cavity in a tunnel shape and is buried in shotcrete is a vertical and horizontal shape formed by intersecting a vertical drainage channel along the axial direction of the cavity and a horizontal drainage channel along a circumferential direction. A hollow shaft is formed by connecting the ends of the heating pipes, which are formed as lattice meshes and embedded in the concrete in the concrete, at the positions overlapping the inside of the vertical drainage channels in the drainage channel network. It is formed in a meandering state that reciprocates in the direction and is formed by piercing the frame concrete in the tunnel axis direction, and the joint portion formed in the joint portion is formed at a position overlapping with one of the horizontal drainage channels. It is preferable.
In that case, it is preferable that the longitudinal drainage channel and the lateral drainage channel forming the drainage channel network are each formed of a plate-shaped drainage material having a long strip plate shape having a rectangular cross section.
It is also conceivable to embed a secondary drainage network in the concrete to collect and drain the groundwater that intrudes beyond the shotcrete.

According to the present invention, the freezing region is generated to the concrete and the outside thereof by controlling the temperature of the concrete and the surrounding rock mass by forcibly circulating the heating medium in the heating pipe network embedded in the concrete. This can prevent the adverse effect caused by freezing and expansion, which has been a concern in the past, and sufficiently ensure the structural mechanical reliability and safety of the lining.
In addition, since there is no freezing area in the surrounding rock mass, the groundwater in the surrounding rock mass is always collected by the drainage network and drained quickly, so excessive groundwater pressure is applied to the lining after the storage tank is completed. In this respect as well, the structural mechanical reliability of the lining can be improved.
In addition, it is possible to drain from the surrounding rock mass through the drainage network at the construction stage, thereby providing a large drainage tunnel and drainage boring hole as in the case of constructing a conventional membrane-type storage tank. It is not necessary to dry the entire surrounding rock mass, so that the workability can be sufficiently improved and the construction period can be greatly reduced and the construction cost can be reduced.
Of course, since the heating pipe network is provided inside the drainage channel network so as to overlap with it, the drainage channel network is not effectively heated and frozen, and stable water collection and drainage are always possible. Can be performed reliably.

Moreover, by forming the drainage network in a vertical and horizontal grid pattern with vertical drainage channels and horizontal drainage channels, water can be collected and drained from the entire cavity, and both vertical drainage channels and horizontal drainage channels can be used. By using a flat strip-shaped drainage material, it is possible not only to secure a sufficient amount of water collection and water flow with a small cross-section, but also to increase the thickness of the sprayed concrete in which it is embedded more than necessary. .
In addition, if a similar drainage channel network is provided for the frame concrete, groundwater entering the sprayed concrete can be further collected and drained, which is more thorough.

FIGS. 1-6 shows the schematic structure of the low-temperature bedrock storage tank which is embodiment of this invention.
The low temperature bedrock storage tank of this embodiment has a sprayed concrete 2, a conditioned concrete 3, a concrete frame 4, a cold insulation material 5, and a membrane material 6 sequentially laminated on the inner surface of a tunnel-shaped cavity 1 having a substantially horseshoe-shaped cross section formed in the rock. By forming a membrane type lining, it functions as a storage tank (tank) for low temperature fluids such as LNG, LPG, DME, etc., but the low temperature bedrock storage tank of this embodiment is a conventional one. The difference is that the drainage network 7 is always embedded in the shotcrete 2 to collect and drain the groundwater from the surrounding bedrock, and in the concrete 4 the heating medium is circulated by circulating the heating medium. The heating pipe network 8 is embedded in the concrete 4 and the temperature outside thereof for always maintaining the freezing temperature or higher.

  In other words, the conventional low temperature rock storage tank of this type is based on the fact that the freezing area that naturally occurs in the surrounding rock mass due to the storage of the cryogenic fluid as described above is also used as a secondary barrier. Since various adverse effects due to expansion may become a problem, the low-temperature rock storage tank of this embodiment does not intentionally generate such a freezing region. For this purpose, a heated pipeline network embedded in the concrete frame 4 is used. In FIG. 8, for example, hot water or brine (antifreeze) of about 20 ° C. is always forcedly circulated to maintain the temperature outside the concrete frame 4 at least at a freezing point or higher.

  However, in this case, since the groundwater pressure in the surrounding rock always acts as an external pressure on the lining as it is, the drainage channel network 7 is embedded in the shotcrete 2 in this embodiment as a countermeasure. The groundwater in the surrounding rock is actively drained by actively flowing into the cavity 1 through the drainage network 7. As a result, it is possible to effectively prevent excessive underground water pressure from acting on the lining after the storage tank is completed, and also to drain the surrounding rock mass by effectively using the drainage network 7 in the construction stage. Therefore, there is no need to provide a large drain tunnel or drain boring hole as in the past to dry the entire surrounding rock mass, and the lining can be performed efficiently, accurately and safely. ing.

The structure of the low-temperature rock storage tank of this embodiment will be described in detail along with its construction procedure.
While digging the cavity 1, rock bolts are placed as necessary, and concrete is sprayed onto the inner surface of the cavity 1 to form the shot concrete 2. 3, the drainage channel network 7 is buried (in FIG. 2, the frame concrete 4 to be constructed in the subsequent stage is shown by a chain line, and the cold insulation material 5 and the membrane material 6 are not shown).

For example, a resin molded product, a porous material, a perforated pipe, or the like that is used as a slope drainage material in the field of civil engineering work can be used as the drainage network 7. A long strip plate-shaped drainage material having a flat rectangular cross section is used, and the drainage material is installed along both the axial direction and the circumferential direction of the cavity 1.
That is, on the bottom surface and the peripheral surface of the cavity 1, plate-like drainage materials that become the vertical drainage channel 7 a along the axial direction of the cavity 1 and the horizontal drainage channel 7 b along the circumferential direction are arranged in a state where they intersect each other at a predetermined interval. As a result, a drainage channel network 7 is formed as a vertical and horizontal grid network. The drainage channel network 7 is connected to a main drainage groove 9 provided at the center of the bottom of the cavity 1, and a main drainage pipe 10 such as a perforated fume pipe is laid in the inside. The main drain grooves 9 and the main drain pipes 10 are preferably inclined downward toward the wellhead and drained by natural flow.
As a result, groundwater from the surrounding rock mass is collected by the drainage channel network 7 and drained through the main drainage pipe 10. Therefore, after the construction of such a drainage channel network 7, the concrete body 4 and the cold insulation material 5 in the latter stage are used. Even during the construction of the membrane material 6 and after the storage tank is completed, a large underground water pressure does not act on them.

After constructing the shotcrete 2 while burying the drainage channel network 7, the concrete concrete 3 is placed on the inside as needed, and the concrete frame 4 is placed on the inside. As shown in FIGS. 2 and 4, a heated pipe network 8 is embedded in the concrete frame 4.
The heating pipe network 8 heats the frame concrete 4 by forcibly circulating a heating medium such as warm water or brine over the entire surface of the frame concrete 4, thereby freezing the surrounding rock mass as well as the drain channel network 7. It is for preventing.
The heating pipe network 8 is appropriately set in position and pitch so that the entire concrete frame 4 is as uniform as possible and temperature unevenness does not occur, and circulation resistance is not excessive. However, in the present embodiment, a large number (32 in FIG. 4) of heating tubes 8a are laid in parallel to the axial direction of the cavity 1, and as shown in FIG. Both are arranged at a position overlapping the inside of the vertical drainage channel 7a forming the drainage channel network 7 described above, with respect to the adjustment concrete 3 (sprayed concrete 2 as the foundation when the adjustment concrete 3 is omitted) The anchor 12 is fixed through the saddle 11. And as shown in FIGS. 4-5, by connecting the both ends of the adjacent heating pipe 8a as a set of a plurality of heating pipes 8a, a single heating pipe network is connected. 8 is formed in a meandering state so as to reciprocate in the axial direction of the cavity (in FIG. 4, all of the 32 heating tubes 8a are one or four, each of which has six heating channels). An example in which a net 8 is provided is shown).

  Since a device for forcedly circulating the heating medium while heating is naturally necessary, as shown in FIG. 5, if main devices such as the heat source device 13 and the circulation pump 14 are appropriately provided on the surface portion. good. In addition, it is preferable to effectively use natural energy and various exhaust heat as a heat source for heating the heating medium, and depending on the location conditions and when there is no concern of adversely affecting the surrounding environment, For example, heat exchange between natural water such as sea water, lake water, and river water and a heating medium can be considered, or the natural water can be used directly as a heating medium, and the use of geothermal or solar heat can also be considered. Of course, various exhaust heat generated artificially from the facility that uses the cryogenic fluid stored in this storage tank, such as turbine exhaust heat, and effective use of exhaust heat from the refrigeration cycle to reliquefy boil-off gas, etc. It is done.

When constructing the concrete frame 4 while burying the heating pipe network 8 as described above, the concrete frame 4 is transferred stepwise by a predetermined distance in the axial direction of the cavity 1. Therefore, it is necessary to form a joint at the joint, but in this embodiment, the joint 4a is formed at a position inside one of the horizontal drainage channels 7b as shown in FIG. 2 (b). It is said. Therefore, the planned formation position of the joint portion 4a is determined in advance at the stage of constructing the shotcrete 2 while burying the drainage channel network 7, and the horizontal drainage channel 7b is provided at the planned position where the joint portion 4a is to be formed. Must be buried.
Thereby, even if it assumes that the water stop performance in the joint part 4a is spoiled by any chance, since drainage is made by the horizontal drainage channel 7b installed in the back side, the frame concrete 4 is passed through the joint part 4a. It is possible to prevent a situation in which water leaks to the inside of the door.
In addition, when the concrete body 4 is handed over in the circumferential direction of the cavity 1, a joint portion along the axial direction of the cavity 1 is formed. In that case, the joint is formed at a position inside the vertical drainage channel 7 a. It is preferable to provide a portion (a vertical drainage channel 7a is formed in advance at the joint formation planned position).

After the concrete body 4 is constructed, an appropriate cold insulating material 5 (that is, a heat insulating material) such as hard polyurethane foam is attached to the entire surface thereof, and a membrane material 6 made of stainless steel sheet or the like is further applied to the entire surface. Install and complete the lining.
At that time, as described above, the surrounding groundwater is collected and drained by the drainage network 7, so that the groundwater pressure does not act at the lining construction stage and the work is carried out efficiently. can do.

After the lining is completed as described above, the lining and the surrounding rock mass are cooled down prior to the storage of the cryogenic fluid. Prior to that, the heating medium is forcibly circulated through the heating pipe network 8 to form the concrete. 4 is started, and the circulation temperature and circulation amount of the heating medium are controlled so that the surrounding rock mass temperature does not fall below the freezing point temperature even after the cryogenic fluid is stored.
Specifically, for example, hot water is used as a heating medium, the supply temperature is set to 15 ° C., the return temperature is set to 5 ° C., and the average temperature of each part of the frame concrete 4 is maintained to be about 10 ° C. To control. By performing such control, the freezing line (0 ° C. isotherm) stays inside the heating pipeline network 8 even after the cryogenic fluid is stored, and a freezing region does not occur outside thereof.

The result of having analyzed the temperature change of the frame concrete 4 at the time of performing the above temperature control with respect to the storage tank for storing LNG (-162 degreeC) is shown below. As an analysis model, a hollow section 1 having a radius of 10 m is excavated horizontally to a depth of 60 m below the ground surface. The thickness of spray concrete 2 and adjusted concrete 3 is 10 cm on each inner surface, and the thickness of frame concrete 4 is Is formed with a lining having a thickness of 50 cm, and the thickness of the cold insulating material 5 (hard urethane foam) is 30 cm (therefore, an effective radius as a storage tank is 9 m). It is arranged along the axial direction at equal intervals in the circumferential direction (center angle 11.25 degrees), and the supply temperature of hot water as a heating medium is controlled to 15 ° C. and the return temperature is controlled to 5 ° C. The outside air temperature was assumed to be 15 ° C, and the rock temperature at the specified temperature boundary position (depth -210 m) was assumed to be 21.3 ° C.
According to the analysis, when the warming control by hot water is not performed, the temperature of the concrete frame 4 rapidly decreases from the start of operation and reaches -50 ° C after about 50 years (after about 18000 days). On the other hand, by performing the heating control as described above, it was confirmed that the temperature does not become stable at about + 5 ° C., and thus the frozen region does not reach the outside of the frame concrete 4.

  According to the analysis from the heat radiation per unit length of the heating tube 8a, the water temperature drop in the heating tube 8a is only about 0.8 deg per 1000 m. Therefore, the difference in water temperature between the return and return is 10 deg as described above. In this case, the length of one line can be increased to 10,000 m or more. Therefore, for example, when the cavity length is 500 m, if 20 heating pipes 8 a having a length of 500 m are connected and the heating pipe network 8 in a meandering state in which the cavity 1 reciprocates 10 times is provided as one system, Well, it is sufficient to provide only two such heating pipeline networks 8.

  According to the low-temperature bedrock storage tank of the present embodiment described above, the heating medium is forcibly circulated through the heating pipe network 8 embedded in the frame concrete 4 to control the temperature of the frame concrete 4 and the surrounding rock mass. In addition, it is possible to prevent the freezing region from occurring to the frame concrete 4 and the outside thereof, thereby eliminating the adverse effects caused by freezing and expansion, which has been a concern in the past, and improving the structural mechanical reliability and safety of the lining. It can be secured sufficiently.

In addition, since there is no freezing area in the surrounding rock mass, the groundwater in the surrounding rock mass is always collected by the drainage network 7 and quickly drained through the main drainage pipe 10, and therefore the lining work after the storage tank is completed. Excessive groundwater pressure does not act as an external pressure, and also in this respect, the structural mechanical reliability of the lining can be improved.
In addition, it is possible to drain from the surrounding rock mass through the drainage channel network 7 at the construction stage, so that large drainage tunnels and drainage boreholes can be formed as in the case of constructing a conventional membrane-type storage tank. It is not necessary to provide the entire surrounding bedrock to be dry, so that the workability can be sufficiently improved and the construction period can be greatly reduced and the construction cost can be greatly reduced.

In particular, since the drainage network 7 is formed in a vertical and horizontal grid pattern by the vertical drainage channels 7a and the horizontal drainage channels 7b, water can be reliably collected and drained from the entire cavity 1, and the vertical drainage channel 7a and the horizontal drainage can be obtained. As the road 7b, a flat plate-shaped drainage material having a flat rectangular cross section is used, so that not only a sufficient amount of water collection and water flow can be secured even with a small cross section, but also the shotcrete 2 in which it is embedded There is no need to increase the thickness of the film more than necessary.
Of course, since the heating pipe network 8 is provided inside the drainage channel network 7 and each heating pipe 8a is arranged at a position overlapping the inside of the vertical drainage channel 7a, the drainage channel network 7 is connected to the heating pipe network 7a. It is not heated and frozen effectively by the road network 8, and stable water collection and drainage can always be performed reliably.

Although one embodiment of the present invention has been described above, the above embodiment is merely a preferred example, and the present invention is not limited to the above embodiment, and appropriate design changes and applications are possible.
For example, in the above embodiment, the drainage channel network 7 is formed in a vertical and horizontal grid pattern by the vertical drainage channels 7a and the horizontal drainage channels 7b. However, the present invention is not limited to this, and water can be collected and drained from the entire periphery of the cavity 1. If so, only the vertical drainage channel 7a or only the horizontal drainage channel 7b may be provided, or conversely, it may be provided as a mat-like drainage channel network almost entirely.
The structure of the heating pipe network 8 also overlaps the inside of the concrete so that the concrete 4 and its outer rock can be effectively heated and the drainage network 7 in the concrete 4 is prevented from freezing. As long as it is provided, instead of providing the heating tube 8a in a meandering state reciprocating in the axial direction as in the above embodiment, the heating tube is in a meandering state such as reciprocating in the circumferential direction. It may be provided or formed in a series of spiral states that are continuous in the circumferential direction.

Further, in addition to embedding the drainage channel network 7 in the shotcrete 2 as in the above embodiment, it is conceivable to further provide the drainage channel network in the frame concrete 4.
That is, the same secondary is applied to the frame concrete 4 as shown in FIG. 6 while basically collecting and draining most of the groundwater flowing into the cavity 1 by the drainage channel network 7 in the above embodiment. If the drainage network 20 is provided, the groundwater that has entered through the shotcrete 2 and the adjusted concrete 3 can be further collected and drained.
In that case, a flat plate drainage material may be used as the secondary drainage channel network 20 in the same manner as the drainage channel network 7 described above, and as shown in FIG. Alternatively, the vertical drainage channels 20a and the horizontal drainage channels 20b may be provided in a lattice shape as shown in FIG. In addition, when providing the horizontal drainage channel 20b, since it will cross the heating pipe 8a, if the heating pipe 8a is arranged in a state of being floated from the surface of the adjustment concrete 3 by an amount corresponding to the thickness of the horizontal drainage channel 20b. good.

It is a cross-sectional view which shows schematic structure of the low-temperature bedrock storage tank which is one Embodiment of this invention. It is the elements on larger scale which show a drainage channel network and a heating pipe network. It is a figure which shows the arrangement | positioning condition of a drainage channel network. It is a figure which shows the arrangement | positioning condition of a heating pipe network. It is a figure which shows the general | schematic system | strain of a heating pipe network similarly. It is a figure which shows the modification of a drainage channel network.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cavity 2 Shotcrete 3 Adjustable concrete 4 Frame concrete 4a Joint part 5 Coolant 6 Membrane material 7 Drainage channel network 7a Vertical drainage channel 7b Horizontal drainage channel 8 Heating channel network 8a Heating tube 9 Main drainage channel 10 Main drainage tube 11 Saddle 12 Anchor 13 Heat source device 14 Circulation pump 20 Secondary drainage channel network 20a Vertical drainage channel 20b Horizontal drainage channel

Claims (4)

Membrane-type low-temperature bedrock storage tank that forms a lining made of sprayed concrete, reinforced concrete, cold insulation, membrane material on the surface of the cavity excavated in the bedrock, and uses the internal space as a storage tank for storing cryogenic fluid Because
In the sprayed concrete, buried a drainage network for collecting and draining groundwater from the surrounding rock,
A heating pipe network is embedded in the concrete to maintain the concrete, sprayed concrete and surrounding rock mass above the freezing temperature by circulating a heating medium such as hot water or brine in the concrete, and the heating pipe A low-temperature bedrock storage tank characterized in that a road network is arranged at a position overlapping the inside of the drainage network. The low-temperature bedrock storage tank according to claim 1,
Drilling the cavity into a tunnel,
The drainage network embedded in the shotcrete is formed as a vertical and horizontal grid network that intersects the vertical drainage channel along the axial direction of the cavity and the horizontal drainage channel along the circumferential direction,
A meandering state that reciprocates in the axial direction of the cavity by connecting the ends of the heating pipes that are placed in positions inside the vertical drainage channel in the drainage channel network, with the heating pipe network embedded in the concrete frame Formed into
In addition, the low temperature rock storage tank is characterized in that it is formed by piercing the frame concrete in the tunnel axis direction, and the joint portion formed in the joint portion is formed at a position overlapping one of the lateral drainage channels. . The low-temperature bedrock storage tank according to claim 2,
A low-temperature bedrock storage tank characterized in that a longitudinal drainage channel and a lateral drainage channel forming a drainage channel network are each formed by a long strip plate-like drainage material having a flat rectangular cross section. The low-temperature bedrock storage tank according to any one of claims 1 to 3,
A low temperature bedrock storage tank characterized by burying a secondary drainage channel network to collect and drain the groundwater that infiltrates beyond the shotcrete in the frame concrete.

Images