US3638431A - Storage tank - Google Patents

Abstract

A storage tank for storing liquid is adapted for construction in soil having a high-water table. The tank has sidewalls and a floor with the upper level of the floor being set below the height of the water table in the soil. To stabilize the tank and counter the effect of the uplift of the water in the soil, a ballast voided fill is placed within the tank.

Description

[451 Feb. 1,1972

United States Patent Shelander [56] References Cited UNITED STATES PATENTS [54] STORAGE TANK [72] Inventor: Charles P. Shelander, Dix Hills, N.Y.

[73] Assignee: Preload Company, Inc., Garden City, N.Y. Rohren.......................................6l/.5

[22] Filed: Feb. 19, 1970 Primary Examiner-J. Karl Bell AttorneyCurtis, Morris & Safford 21 Appl. No.:

ABSTRACT A storage tank for storing liquid is adapted for construction in soil having a high-water table. The tank has sidewalls and a floor with the upper level of the floor being set below the height of the water table in the soil. To stabilize the tank and counter the efiect of the uplift of the water in the soil, a ballast voided fill is placed within the tank.

3 Claims, 2 Drawing Figures PATENTED FEB I 1972 INVENTOR CHARLES P. SHELANDER BY 7 7m {Maj ATTORNEYS STORAGE TANK BACKGROUND OF THE INVENTION This invention relates to tanks for storing liquids, and more particularly to tanks which are placed in soils having highwater tables with the upper surface of the tank floor at an elevation below that of the water table.

It is often necessary to place liquid storage tanks, such as those used in water supply systems and the like, on land with high-water tables. A water table is the natural height or elevation of water in the soil in relation to the top or ground line of the land. A high-water table is one where the water is very close to the surface. Often times for asthetic purposes or for engineering reasons it is necessary to construct tanks so that the floor of the tank is at an elevation below that of the water table. When tanks are so constructed the hydrostatic pressure caused by the water table has a tendency to force the floor upwardly. This uplift effect can cause substantial damage to the tank unless adequate precautions are taken. One solution would be to provide an extremely heavy and thick concrete floor to counterbalance the uplift. In essence, the thickened floor serves as a counterweight to overcome the hydrostatic head of the water table. However, such a solution is too costly and reduces the storage volume of the tank.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ballast system for tanks built in regions having high-water tables so as to eliminate the necessity for costly thickened floors. It is a further object of the present invention to provide a tank construction so that the ballast system does not substantially reduce the storage capacity of the tank.

In the present invention the ballast which is used is of a rock-filled type and extends to a height sufficiently above the floor surface to counteract the uplift effect of the water table.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a tank in accordance with the present invention; and

FIG. 2 is a sectional view showing the tank construction and ballast system in relationship to the surrounding soil area and the water table of the soil.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Referring to the drawings, a tank in accordance with the present invention is shown. The tank 10 includes a foundation 12 of suitable reinforced concrete and which is integrally connected to a reinforced concrete floor 14. Supported on the foundation 12 is a reinforced concrete core wall 16. The wall 16 is set on a rubber pad of suitable elastomeric material so as to permit inward movement of the wall 16 during prestressing of that unit. This type of tank construction is more fully illustrated and discussed in US. Pat. No. 2,932,964, issued Apr. 19, 1960.

To insure the watertight construction of the tank where the wall 16 is supported on the pad 18, a continuous water stop 20 is provided. After the tank wall 16 has been erected in place it is advantageously prestressed by means of tendons 22 which are covered over by a suitable cover coat 24 of cementious material. Flow of liquid into and out of the tank is provided by means of a conduit line 26. The inlet and outlet line 26 is preferably encased in concrete 29 to strengthen it against possible damage. Surrounding the inlet portion of the line 26 is a perforated concrete cylinder 30 which in the illustration is a concrete pipe. Placed on the upper surface of the floor 14 and surrounding the cylinder 30 is rock ballast 32. From the top surface 34 of floor 14 to the top surface 36 of the ballast 32 is a distance which has been indicated as Hr. As shown in FIG. 2, the distance from surface 34 to the water table W/T in the surrounding soil E is designated Hw. It will be noted that the water table W/T is below the ground line G/L of the surroundin earth.

In or er to determine the height of the rock ballast the following forrnula may be used:

Hr=(62.5/200) Hw 62.5 is the approximate weight per cubic foot of water while 200 is the approximate weight of a cubic foot of rock. The formula may be more empircally written as:

Advantageously the ballast rock 32 permits the voids between the individual rocks to be used as a storage area for liquid in the tank. Accordingly, it is only the solid portion of the ballast which is deducted from the interior storage volume of the structure 10.

In order to clean the ballast 32 of any silt which may settle therein, a backwashing system may be utilized. To do this liquid is pumped in through the line 26 causing any deposits within the ballast to be flushed upwardly. It is then possible to flush away any silt by means of high-pressure hoses in a routine fashion.

If desired, a silt ring 38 may be provided in connection with the line 26 to prevent the entry of silt into the line.

While the present invention has been disclosed in the illustrated embodiment as applying to a soil with a high-water table, it may also be utilized as a precaution and safety feature where the tank is subject to possible flooding. In that case Hw would be determined as the height of high water above the surface 34.

What is claimed:

1. A storage tank for storing liquids and built on soil having a height water table, said tank including a cylindrical concrete sidewall and floor, the floor being placed at an elevation lower than that of the water table, drainage means connected to said tank for removing liquid therefrom, a voided rock ballast fill within the tank and resting on the floor, said rock ballast fill being disposed within said storage tank to a level less than the height of said sidewall so that the upper portion of said storage tank is free of rock ballast till, the weight of said fill being sufficient to overcome substantially and equalize the uplift effect of water in the soil against the bottom of the floor, the ballast fill having sufficient voids to store liquid whereby the storage volume of the tank is only reduced by the solid portion of the fill.

2. A storage tank for storing liquids as defined in claim 1 wherein the height of the fill above the upper surface of the floor is at least about 0.3 the height of the water table above the upper surface of the floor.

3. A storage tank for storing liquids as defined in claim 1 and further including a screening device separating the ballast fill from the tank drainage means.

Claims (3)

1. A storage tank for storing liquids and built on soil having a height water table, said tank including a cylindrical concrete sidewall and floor, the floor being placed at an elevation lower than that of the water table, drainage means connected to said tank for removing liquid therefrom, a voided rock ballast fill within the tank and resting on the floor, said rock ballast fill being disposed within said storage tank to a level less than the height of said sidewall so that the upper portion of said storage tank is free of rock ballast fill, the weight of said fill being sufficient to overcome substantially and equalize the uplift effect of water in the soil against the bottom of the floor, the ballast fill having sufficient voids to store liquid whereby the storage volume of the tank is only reduced by the solid portion of the fill.

2. A storage tank for storing liquids as defined in claim 1 wherein the height of the fill above the upper surface of the floor is at least about 0.3 the height of the water table above the upper surface of the floor.

3. A storage tank for storing liquids as defined in claim 1 and further including a screening device separating the ballast fill from the tank drainage means.

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