US3302407A

US3302407A - Subterranean storage facilities and method of constructing such facilities

Info

Publication number: US3302407A
Application number: US360886A
Authority: US
Inventors: Richard L Every
Original assignee: Continental Oil Co
Current assignee: ConocoPhillips Co
Priority date: 1964-04-20
Filing date: 1964-04-20
Publication date: 1967-02-07
Anticipated expiration: 1984-02-07

Description

Feb. 7, 1967 R n.. EVERY 3,302,407

SUBTERRANEAN STOAGE FACILITIES AND METHOD 4 OF CONSTRUCTING SUCH FACILITIES Filed April 20, 1964 2 Sheets-Sheet l WHI'IIgIIIIIAIIIIIIn .".zr'l'lnul'a'l'lm TIEL- E www Feb. 7, 1967 R. l.. EVERY 3,302,407

SUBTERRANEAN STORAGE FACILITIES AND METHOD 0F CONSTRUCTING SUCH FACILITIES Filed April 20, 1964 2 Sheets-Sheet 2 "'Illlllllf 'FlrEflr BY @OMM United States Patent Oiiice 3,302,407 Patented Feb. 7, 1967 SUBTERRANEAN STORAGE FACILITIES AND METHOD OF CONSTRUCTING SUCH FA- CILITIES Richard L. Every, Ponca City, Okla., assigner to Continental Oil Company, Ponca City, Okla., a corporatlon of Delaware Filed Apr. 20, 1964, Ser. No. 360,886 12 Claims. (Cl. 61.5)

This invention relates to earthen facilities for storing large volumes of uids. More particularly, the present invention relates to subterranean cavities adapted to contain liquids maintained at cryogenic temperatures, and to methods which can be beneficially employed in constructin g cavities of this type.

The tremendous production in this country of liquefied petroleum gases, as Well as other liquefied gases exerting high vapor pressure, has presented a serious problem of providing suitable storage facilities to accommodate such fluids. This is particularly true during the seasons of the year when a readily available market for such production does not exist. The difficulty which is often encountered in providing suitable storage facilities for fluids of the type mentioned is the requirement that tanks and containers which are constructed for this purpose must be very massive and therefore quite expensive in order to withstand the high vapor pressures developed by such fluids. Moreover, in order to avoid excessive heat trans fers from the surrounding atmosphere to the cold fluids contained in such storage facilities, expensive insulation for such yfacilities must be provided. Many of the same problems which are associated with the above-ground storage of liquefied petroleum gases are also characteristic of the storage of all liquids at cryogenic temperatures in this type of facility.

One solution to the problems encountered in storing liquefied petroleum gas and other volatile liquids, and also non-volatile liquids at cryogenic temperatures, in aboveground tanks and storage facilities has been the provision of either natural or artificial subterranean storage caverns for this purpose. One type of such cavern is that which is formed in impermeable rock formations, such as shale and limestone. However, naturally occurring formations which lend themselves to the construction of such caverns are difficult to find, and, of course, do not always accommodate themselves to storage of such liquids in the most desirable locations. Also, expensive linings are frequently required to -make such natural or artificial caverns absolutely impermeable to the liquids that are to be stored therein, or the ground waters which may infiltrate the cavern to contaminate the contents thereof.

More recently, it has been proposed to Iform the underground storage cavern in a permeable, Water bearing formation. In this case, the water in the cavern walls is frozen to render the walls impermeable to the fluids stored in the cavern, and also to the connate Waters surrounding the cavern. One of the methods which has been proposed for forming such storage caverns in impermeable, water bearing formations is the so-called ring freeze technique. According to this method, a plurality of wells is drilled in circular formation around a perimeter of the area which is to be excavated to form the underground cavern. A refrigerating medium is then pumped down into the wells to freeze the Water in a ring and surrounding the portion of the ground which is to be excavated. The earth is excavated Within the frozen perimeter and a protective cover or roof is placed over the excavation to prevent the loss through volatilization and evaporation of the liquid petroleum gas or other fluid which is to be stored. Despite the advantages which underground storage offers over storage in tanks constructed above the surface of the earth, there are still several significant problems which have not been satisfactorily solved in the construction of artificial underground storage facilities. In the case of the construction of underground caverns or chambers surrounded by earth having water frozen in the interstices thereof, it is quite expensive to prefreeze the earth prior to excavating the storage facility. Moreover, frozen earth which is permitted to attain a temperature above 40 F. has a tendency to creep or shift and this may result in sloughing of the Walls of the storage facility or major cave-ins which destroy 'the usefulness of the storage facility. Where liquids are to be stored at 10W temperatures, it is sometimes the present practice to line the subterranean cavern with prestressed concrete so as to avoid creeping, sloughing and cave-ins of the type hereinbefore described. When liquids are stored in concrete lined caverns of this type at cryogenic temperatures, heaters must be incorporated in the concrete liner or must be placed in close proximity to the concrete liner on the outside thereof in order to avoid cracking of the concrete resulting from the exposure to cryogenic temperatures.

The present invention provides a novel method for constructing underground storage facilities which are particularly useful for storing fluids at cryogenic temperatures. Broadly described, the method comprises excavating the earth to form a generally frusto-conically shaped excavation having side Walls which are inclined at approximately the angle of repose of the earth excavated; positioning a relatively thin, tubular liner in the excavation; then backfilling the earth around the tubular liner and, simultaneously with such backfilling, supporting the liner from the inside by at least partially filling it with a liquid which serves to oppose the compressive forces exerted by the earth deposited around the outside of the liner. Finally, after the backfilling operation has been completed, the ballasting liquid which has been used to counteract the forces of the earth deposited around the liner is drained or removed from inside the liner.y

By positioning the tubular liner in position in the ground in the manner described, collapse of the liner as a result of creeping or shifting of the earth which may occur during the backfilling operation is avoided. Moreover, the cavity which is defined by the thin tubular liner can be constructed at substantially lower cost than the cost which is involved in constructing a cavity having a concrete liner or in prefreezing the earth prior to excavating. Also, the necessity for providing means for heating the liner, such as is necessary in the case of concrete liners, is avoided. By forming the side walls of the excavation at an inclination which approximately corresponds to the angle of repose of the earth excavated, slides and cave-ins are avoided during this phase of the construction.

Although the tubular liner which is positioned in the earth may be generally cylindrical in configuration, it is preferably frusto-conical, with the smaller end of the liner resting upon the bottom -of the excavation. In other words, the tube has a larger diameter at its top than at the bottom, and therefore, less force is exerted on the liner by the backfilled earth. Also a tubular liner which does not have a bottom in the lower end is preferably used where storage at cyrogenic temperatures is con# templated, since, in this case, the moisture in the earth which will form the bottom of the storage facility will be frozen to provide a substantially impermeable bottom, and also since at the low temperatures of cyrogenic storage, expansion and contraction of the bottomless tank will result in less structural stress and failure than would be the case if the tank were provided with a bottom. In instances 3 where a bottom is to be provided, however, a plastic insulating material is preferred to the use of metal since the plastic can accommodate more successfully to the expansion and contraction resulting from variations in the thermal environment.

Several novel renements in the procedure for constructing subterranean storage facilities in accordance with the present invention as hereinbefore broadly outlined can be practiced. These modifications and innovations will be hereinafter described in greater detail, and it is believed that it will suffice at this point to mention but two of the more important of these. First, it is usually desirable, when constructing a subterranean storage facility for use in stor-ing liquids at cyrogenic temperatures, to use, for the purpose of filling the tubular lining during backilling, a liquid which is cooled well below the freezing point of water. For example, brine maintained at a temperature of from about -l C. to about 20 C. can be employed. When a liquid cooled to the described extent is placed in the tubular liner during the backfilling phase of the construction, the moisture which is located in the interstices of the earth which is deposited around the outside of the liner is frozen so as to consolidate this earth and prevent it from caving in or creeping. The freezing of the interstitial water also assists in further irnproving the impermeability of the walls of the storage facility. Moreover, the moisture in the earth which forms the bottom of the storage facility is simultaneously frozen to provide a substantially impermeable bottom.

A second technique which is preferably used in conjunction with the broad procedure of the present invention as hereinbefore outlined constitutes that of providing certain types of reinforcing elements around the outside of the tubular liner during the deposition of earth in the excavation around the outside of the outside of the liner. The reinforcing elements used are preferably generally frusto-conical, woven wire mats which are disposed around the outside of the tubular liner and extend downwardly and outwardly therefrom into the portion of the excavation `which is being backfilled. The direction in which the frusto-conical reinforcing elements project downwardly in the excavation is preferably such that the reinforcing elements extend at an angle of about 90 to the walls of the excavation. With reinforcing elements of the type described positioned in the manner indicated, there is substantially less tendency for the earth which is backlled around the tubular liner to creep or shift during or following the backfilling operation.

The described procedures for -constructing subterranean storage facilities are particularly useful in situations where a subterranean impermeable rock formation which is overlain by unconsolidated soil constitutes the locus in which it is desired to construct the subterraneans facility. The procedure which has been described is, under these circumstances, utilized for providing an access passageway through the loose soil to the top of the consolidated rock formation. The rock formation can then be removed to form a subterranean cavity having impermeable walls, which cavity is accessible through the thin, tubular liner which is installed in the manner hereinbefore described. The manner of using the process of the invention for constructing an underground storage facility in consilidated, impermeable rock formations will be described in greater detail hereinafter.

From the foregoing general description of the invention, it will have become apparent that it is a major object of the present invention to provide an improved method for constructing subterranean facilities which may be used for the purpose of storing fluids below the surface of the ground.

An additional object of the invention is to provide a method for constructing a subterranean storage facility which may be effectively used for storing fluids at cryogenic temperatures, which method does not require costly prefreezing of the earth surrounding the facility in order to reduce its permeability and provide suitable walls for containing such fluids.

An additional object of the present invention is to overcome the problems of earth cave-ins and creeping of the earth during and following the excavation of underground storage facilities.

An additional object of the present invention is to provide an underground storage chamber or cavity which can be -constructed substantially cheaper than above-ground storage facilities, and which requ-ires relatively little insulation in order to retain fluids therein at cyrogenic temperatures.

Yet another object of the present invention is to provide an underground chamber for storing cyrogenic fluids which does not require the use of heaters to prevent cracking or thermal distortion of the materials of which the walls of the chamber are constructed.

Another object of the present invention is to provide a novel subterranean storage facility which is less expensive to construct than previous types of subterranean storage facilities, and yet which is suitable for storing liquids a cyrogenic temperatures over long periods of time.

Another object of the invention is to provide a subterranean liquid storage cavity which is at least partially lined with a thin, tubular liner and is therefore less costly to construct than a concrete lined storage facility.

In addition to the foregoing described objects and advantages of the invention, additional objects and advantages will become apparent as the following disclosure is read in conjunction with a perusal of the accompanying drawings which illustrate certain specific aspects of my invention.

In the drawings:

FIGURE 1 is a somewhat schematic vertical sectional view through the center of an excavation which is formed during the construction of a subterranean storage facility in accordance with the present invention. A rigid tubular liner is shown in place in the excavation.

FIGURE la is a sectional view similar to FIGURE l, but illustrating a modified form of rigid tubular liner which may be utilized in the method of the invention.

FIGURE 2 is a view in section similar to FIGURE l, but illustrating the second step of the process of the invention, i.e., the commencement and progress-ion of backlling around the rigid tubular liner.

FIGURE 3 is a vertical sectional view through the earth and through a rigid tubular liner positioned in the earth and forming the walls and bottom of a subterranean storage facility constructed in accordance with one embodiment of the present invention.

FIGURE 4 is a View in section similar to FIGURE 3, but illustrating a subterranean storage facility which has been completed in accordance with a modified embodiment ofthe process of the present invention.

FIGURE 5 is a somewhat schematic sectional view illustrating the first step which is followed in using the present invention to form a subterranean storage facility at a location where an impermeable, -consolidated rock is located at a relatively shallow depth in the earth and is overlain with loose or unconsolidated earth.

FIGURE 6 is a vertical sectional view similar to FIG- URE 5, but illustrating the manner in which the rigid tubular liner used in the process of the invention is positioned over the opening in the impermeable rock and is anchored in such rock.

FIGURE 7 is a vertical sectional view similar to FIG- URES 5 and 6, but further illustrating the manner in which the process of the invention is completed.

The broadest and most basic method of practicing the present invention will first be described by referring to FIGURES 1 through 3 of the drawings. In FIGURE 1, the earth in which a subterranean storage facility is to be located is indicated generally by reference character 10. The process of constructing the storage facility is commenced by providing an excavation 12 in the earth with the excavation having inclined walls 14. The walls 14 slope upwardly and outwardly from the bottom 16 of the excavation at an angle which is not more than, and preferably substantially equal to, the angle of repose of the particular earth in which the excavation is to be located.

After the excavation 12 has been formed to the desired depth, a tubular liner 18 is placed in the excavation with the bottom of the liner resting on the bottom 16 of the excavation or, if desired, embedded therein. The tubular liner 18 is constructed of a thin material, such as plastic, synthetic resin, metal or alloy which is not deleteriously affected by very low temperatures-that is, does not become brittle or structurally weakened at the cryogenic temperatures at which liquids will be stored Within the liner. For this purpose, aluminum and 9 percent nickel steel are good materials.

As used herein the word thin indicates a wall thickness, less than about two inches, suicient to withstand the external pressures applied to the liner during construction of the cavity. Because of the wide Variety of materials used and further :because of the different tech,- niques used in construction it is not possible to assign an exact numerical range to delineate the term thinf In general, however, a rliner having a wall thickness between about 1/32 and 1 inch will be used. The shape of the tubular liner 18 can be Varied from the generally cylindrical shape illustrated in FIGURE'I to the frusto-conical shape illustrated in FIGURE la. In some instances, the use of the frusto-conically shaped tubular liner is much to be preferred since there is, in this case, considerably less force exerted on the tube from the outside by the earth which is to be backlled around the tube as subsequently explained herein. Moreover, vertical ilutin-g may be added to the -liner to further increase its resistance to lateral pressure. y

Whether the tubular liner 18 contains a bottom as a part thereof, or whether the earth at the bottom of the excavation is used for this purpose is 0f some significance. The earth, after it has been frozen in the manner hereinafter described, is used as `the bottom of the tubular liner `18 in preference to a metal bottom. This is because the radial expansion and contraction of the tubular liner as a result of temperature fluctuations during cryogenic storage conditions introduce stresses to 1a metallic bottom which may buckle or crack this type of bottom. On the other hand, certain types of plastics or synthetic resins such as polyurethane, polymethylene, polytetrafluoroethylene, polyethylene and the like, may be satisfactorily used as the bottom of the tubular liner 18 since many plastics exhibit a resiliency sufficient to undergo the expansion and contraction without structural failure. A plastic bottom 20 for the tubular liner 18 is illustrated in FIGURES la, 2 and 3. After the tubular liner 18 has been placed in position in the excavation 12, the procedure of backfilling Ithe excavated earth around the outside of the liner is commenced. Since, in the case of loose, dry, unconsolidated earth, the earth may shift or become 4overconcentrated at one point along the tubular liner 18, there is considerable danger that the tubular liner, being made of thin metal, may be collapsed or buckled as a result of the forces exerted by the surrounding earth. To counteract this undesirable, potentially damaging force, the tubular liner 18 is gradually filled with a liquid 22. The rate at which the liquid is introduced to the tubular liner 18 is preferably correlated to the rate at which earth is backlled in the excavation 12 around the tubular liner 18 so that the level of the earth outside the liner and the level of the liquid 22 inside the liner are maintained substantially equal. In this way, the tubular liner 18 is internally reinforced against collapsing resulting from the backlling of the earth therearound.

When the earth returned to the excavation 12 during backlling is clayey, or has a gummy, adhesive quality, it may be compacted vertically during filling to reduce the tendency of the backfilled earth to collapse or distort the tubular liner after the liquid 22 is removed upon completion of the backlling. Where the soil is loose `and unconsolidated, however, and cannot be consolidated suciently by vertical mechanical compaction to safely alleviate cave-in tendency, consolidation of the backfilled soil by another technique is employed. This technique entails freezing interstitial water in the soil returned to the excavation to form a consolidated, impermeable wall of earth surrounding the liner 18. A sufficient amount of interstitial water for this purpose may occur naturally in the excavated soil, or it may be necessary to add water to the soil prior to backfilling. A moisture content of at least l0 percent by weight preferably characterizes the soil when consolidation is effected by freeezing.

In a preferred method of effecting consolidation of the backll by freezing, the liquid 22 which is introduced into the tubular liner 18 is maintained at a substantially lower temperature than the freezing point of water. A good liquid for use when proceeding in this way is brine Which can, of course, be cooled considerably below the freezing point of pure Water without itself being frozen. With the liquid within the tubular liner 18 being retained at a lower temperature than the freezing point of water, the moisture in the interstices of the soil which is returned to the excavation around the outside of the tubular liner 18 will be frozen. The freezing of this interstitial water consoldates the earth around the liner as the excavation 12 is being filled. Also, the soil around the liner is rendered substantially impermeable as the water in the interstices of the soil is converted to ice and undergoes expansion. In FIGURE 2, that portion of the backlled soil which is frozen is indicated by reference character 24, while the remainder of the -backfilled soil is designated by reference character 26.

An alternative method of freezing the moisture in the backlled earth is to reduce the temperature of the liquid 22 inside the tubular liner 18 after the excavation 12 is completely filled and while the liner is filled with liquid.

After the backfilling has been completed so that the soil surrounding the tubular liner 18 is at ground level, the liquid 22 is removed from the liner 18 to complete the underground storage facility as shown in FIGURE 3. The facility is especially useful for the purpose of storing liquids at cryogenic temperatures since the walls of the facility are constructed of material which does not become brittle or weakened at extremely low temperatures. Where the ballast liquid 22 which is used to provide internal support to the tubular liner 18 during construction is cooled to a temperature below the freezing point of water, the liner 18 will be surrounded by the frozen earth 24 as illustrated in FIGURE 3. The earth beneath the bottom 20 of the liner 18 will also be frozen so that impermeability of the bottom is retained even though the plastic bottom 28 develops leaks or becomes eroded or corroded away after extended periods of usage. vOnce the liquid which is to be stored in the facility is placed in the tubular liner 18, the earthen walls outside the liner are maintained in their frozen condition as a result of the low temperature of the liquid contained inside the liner. It will, of course, be generally desirable to place some type of roof or cover across the top of the tubular liner 18 at ground level to prevent loss through excessive vaporization of the fluid contained in the storage facility.

One further innovation which may be included in the procedure herein'before described, and which improves the stability of the backll when certain types of soils are encountered, is the use of reinforcing elements around the tubular liner in the excavation during the backfilling operation. The reinforcing elements employed are illustrated in FIGURE 4 and are designated by reference character 30. The reinforcing elements 38 are frusto-conical in configuration, and are coaxially positioned around the tubular liner 18. The reinforcing elements 38 extend downwardly and outwardly from the liner 18 and, preferably, extend at approximately a right angle with respect to the angle of repose of the soil removed from the excavation, which angle is indicated by the dashed lines in FIGURE 4. Viewed in another way, the reinforcing elements 30 preferably extend substantially normal to the inclined walls ofthe excavation.

The reinforcing elements 30 are porous or apertured to permit the soil to pass therethrough and may conveniently be made of a mesh material such as woven wire. These elements are placed in the illustrated position as the soil is returned to the excavation 12 around the outside of the tubular liner 18. When the reinforcing elements 3f) are employed, it is preferable to widen the bottom of the excavation 12 so that the bottom is characterized by a diameter substantially larger than the diameter of the lower end of the tubular member 18. Better anchorage for the lowermost reinforcing member 30 is thus provided in that one end of the reinforcing member can be quite easily embedded in the enlarged fiat bottom of the excavation 12. In most instances, additional reinforcing members will not be necessary since creeping of the soil placed in the excavation during backfilling will, in most cases, be prevented through the use `of the one reinforcing member located at the bottom of the excavation.

The process of the present invention is particularly useful when employed to construct a subterranean storage facility in an environment in which the earth contains a consolidated rock formation underlying a relatively shallow bed of unconsolidated earth. The method of constructing the underground cavity or storage chamber in this environment is best illustrated in FIGURES 5, 6 and 7. As illustrated in FIGURE 6, the unconsolidated earth 32 is initially removed to provide `an excavation 34 extending downwardly in the soil to the depth at which the impermeable rock formation 36 is located. As in the case of the excavation 12 illustrated in FIGURES 1 and 2, the excavation 34 has inclined side walls 38 which slope at approximately the angle of repose of the earth which is removed.

After the impermeable rock formation 36 is reached, a cavity 40 is formed in the rock and, of course, opens into the excavation 34. Since the rock formation is consolidated and does not present any problem of cave-in or creeping, the walls of the cavity 40 formed in the rock formation may be made substantially vertical or may be undercut as shown.

After the excavation 34 and cavity 40 have been formed, a thin metallic tubular liner 42 is placed in the excavation in the position illustrated in FIGURE 6 so that the bottom of the liner is positioned around the opening to the cavity 40 in the rock and is preferably embedded in the rock for stability and structural strength. After the liner 42 has been placed in position, backfilling is carried out in the manner hereinbefore described. Thus, the cavity 40 in the impermeable rock formation is filled with a liquid until the liquid level enters the lower end of the tubular liner 42. Backfilling of the earth in the excavation 34 around the liner is then commenced and the level of the earth outside the liner and the liquid inside the liner are continuously equalized as the backfilling continues. As previously indicated, it may he preferable to refrigerate the liquid during ybackfilling :to maintain it at a temperature below the freezing point Iof water. It may further be preferable to increase the moisture content of the earth being replaced in the excavation to above about l percent by weight if the soil `does not contain moisture to this extent in its natural state. Finally, it is also desirable, as in the case of the types of storage facilities described in referring to FIG- URES 1-5, to provide reinforcing elements, such as the woven wire frusto-conical members 44 shown in FIGURE 7. This figure illustrates the `subterranean storage facility formed through the loose, unconsolidated soil 32 and in the consolidated rock formation 36 as the facility appears nafter it has been completed using a refrigerated liquid to 8 freeze the soil 46 adjacent the tubular liner 42 and also the moisture in the rock surrounding the cavity 40.

Upon completion of the procedures hereinbefore described, the thickness of the frozen soil surrounding the tubular liner 42 and the cavity 40 in the rock formation 36 may be further increased if desired to assure greater structural strength and impermeability in the walls defining the facility. This can be accomplished by circulating a refrigerant through buried tubes or conduits in a manner well understood in the art, or by retaining a liquid at an extremely low temperature in contact with the walls of the rock formation or the tubular liner for an extended period of time. conduits may be placed in the original excavation prior to completion of the backll.

Although particular embodiments of the method of forming subterranean storage facilities in accordance with the present invention have been hereinbefore described by way of example, it will be appreciated that various innovations and modifications may be effected in the described procedures without departing from the basic principles upon which the invention is based. Insofar, therefore, as variations from the described procedures continue to include a reliance upon the fundamental principles of the invention,r such variations are intended to be circumscribed by the spirit and scope of the invention.

What is claimed is:

1. A method of constructing a subterranean chamber comprising:

excavating the earth to form a generally frusto-conically shaped excavation having side walls inclined not more than the angle of repose of the earth excavated;

positioning a tubular liner in said excavation;

depositing earth in said excavation around the outside of said liner to fill the portion of said excavation -outside of and around said liner, and simultaneously with the deposition of said earth, at least partially filling the interior of the liner with a liquid at a temperature below the freezing point of water whereby the moisture in at least a portion of the earth deposited around the outside of said liner is frozen to a solid state to consolidate said deposited earth to oppose the compressive forces of said deposited earth outside of said liner; and

when the vertical level of said deposited earth corresponds to the level of the ground, removing said liquid from said liner.

2. A method of constructing a subterranean chamber as defined in claim 1 wherein the interior of the liner is filled with a liquid at a rate such that the level of liquid inside said liner is always at least as high as the vertical level of the earth deposited around the outside of said liner.

3. A- method of constructing a `subterranean chamber as dened in claim 2 wherein the rate at which the earth is deposited around the outside of said liner, and the rate at which the liner is filled with liquid are correlated to maintain the vertical levels of the deposited earth and the liquid substantially equal.

4. A method of constructing a subterranean chambe as defined in claim 1 wherein said liner is generally frusto-conical in configuration with its sides being inclined to the vertical at an acute angle less than the angle of repose of the earth excavated when the liner is in place in said excavation.

5. A method of constructing a subterranean chamber as defined in claim 1 wherein said liquid is brine.

6. A method of constructing a subterranean chamber as defined in claim 1 and further characterized to include the step of freezing the moisture in the earth lying radially outwardly of the earth containing said frozen moisture, to increase the radial thickness of the ice-containing earth surrounding said tubular liner.

If desired, such tubes or` 7. A method of constructing a subterranean chamber as dened in claim 1 wherein said tubular liner is provided with a generally horizontally extending bottom.

8. A method of constructing a subterranean chamber as defined in claim 1 and further characterized to include the step of positioning at least one rigid, perforated, reinforcing member of generally frusto-conical configuration in said excavation and coaxially around said rigid tubular liner with said frustoconical reinforcing member extending downwardly and outwardly from the external peripheral wall of said rigid tubular liner.

9. A method of constructing a subterranean chamber as defined in claim 8 wherein said rigid, perforated reinforcing member extends at substantially a right angle to the walls of said frusto-conically shaped excavation.

10. A method of constructing a subterranean storage facility in a consolidated rock formation overlain by unconsolidated earth comprising excavating the unconsolidated earth to form a generally frusto-conically shaped excavation terminating at its bottom at the upper surface of said con- `solidated rock and having walls inclined upwardly and outwardly from the bottom of the excavation to the top of the excavation at not more than the angle of repose of the unconsolidated earth;

forming a cavity in the consolidated rock communicating with said excavation in the unconsolidated earth;

positioning a tubular, rigid liner in said excavation with the lower end of said tubular liner based upon said rock formation and the bore of said tubular liner communicating with the Cavity in the consolidated rock;

depositing earth in said excavation around the outside of said tubular liner to fill the portion of said excavation outside of and around said liner, and simultaneously with the deposition of said earth, at least partially filling the interior of the liner with a liquid to oppose the compressive forces of the earth deposited outside of said liner;

freezing interstitial water in the earth surrounding said tubular, rigid liner and surrounding the cavity in said consolidated rock to form relatively impermeable walls surrounding the cavity in said rocks and to conconsolidate the earth around said liner, and

after the vertical level of said deposited earth corre sponds to the level of the ground, removing the liquid from said liner.

11. A method of constructing a subterranean storage facility as defined in claim 10 wherein the freezing of said interstitial water is accomplished by filling said cavity and said generally tubular, rigid liner with a liquid maintained at a temperature below the freezing point of water.

12. An underground storage facility for liquids to be stored at cryogenic temperatures comprising:

a consolidated rock formation defining a cavity having frozen wall portions around said cavity containing interstitially located ice;

a generally tubular metallic liner supported -on said consolidated rock formation and extending to the surface of the ground with the bore of said tubular liner communicating with the cavity in said consolidated rock formation;

earth containing frozen interstitial moisture around said tubular metallic liner and extending from said consolidated rock formation to the surface; and

at least one rigid, perforated reinforcing member of generally frusto-conical configuration positioned coaxially around said generally tubular metallic liner and extending downwardly and radially outwardly from said generally tubular member to arrest creeping of the earth surrounding said liner.

References Cited by the Examiner UNITED STATES PATENTS Re. 25,199 7/1962 Brownell.

1,968,993 8/1934 Cox 61-35 2,193,425 3/1940 Lake 61--35 X 2,333,315 11/1943 Klingberg 61--.5 2,488,915 11/1949 Jackson 61-36 X FOREIGN PATENTS 124,053 10/ 1901 Germany.

921,844 3/1963 Great Britain.

EARL I. WITMER, Primary Examiner.

Claims

12. AN UNDERGROUND STORAGE FACILITY FOR LIQUIDS TO BE STORED AT CRYOGENIC TEMPERATURES COMPRISING: A CONSOLIDATED ROCK FORMATION DEFINING A CAVITY HAVING FROZEN WALL PORTIONS AROUND SAID CAVITY CONTAINING INTERSTITIALLY LOCATED ICE; A GENERALLY TUBULAR METALLIC LINER SUPPORTED ON SAID CONSOLIDATED ROCK FORMATION AND EXTENDING TO THE SURFACE OF THE GROUND WITH THE BORE OF SAID TUBULAR LINER COMMUNICATING WITH THE CAVITY IN SAID CONSOLIDATED ROCK FORMATION; EARTH CONTAINING FROZEN INTERSTITIAL MOISTURE AROUND SAID TUBULAR METALLIC LINER AND EXTENDING FROM SAID CONSOLIDATED ROCK FORMATION TO THE SURFACE; AND AT LEAST ONE RIGID, PERFORATED REINFORCING MEMBER OF GENERALLY FRUSTO-CONICAL CONFIGURATION POSITIONED COAXIALLY AROUND SAID GENERALLY TUBULAR METALLIC LINER AND EXTENDING DOWNWARDLY AND RADIALLY OUTWARDLY FROM SAID GENERALLY TUBULAR MEMBER TO ARREST CREEPING OF THE EARTH SURROUNDING SAID LINER.