US3630037A

US3630037A - Arctic piles

Info

Publication number: US3630037A
Application number: US54985A
Authority: US
Inventors: George C Howard
Original assignee: BP America Production Co
Current assignee: BP America Production Co
Priority date: 1970-07-15
Filing date: 1970-07-15
Publication date: 1971-12-28
Anticipated expiration: 1988-12-28
Also published as: CA929755A

Abstract

Piles are used quite widely in the Arctic to support buildings and structures. However, in many areas the piles are forced upwardly by the thawing and refreezing of the surrounding earth. I solve this problem of pile heaving by placing a rubberlike sleeve around the pile. The lower end of the rubber sleeve is fastened to the pile below the thaw zone. The upper end of the rubber sleeve is sealingly and slideably fitted about the pile above the surface. The cavity between the sleeve and the pile is filled with a viscous nonfreezing liquid. The heaving force which would ordinarily act on the pile now acts only on the rubber sleeve.

Description

United States Patent Inventor George C. Howard [56] References Cited Tulsa, Okla- UNITED STATES PATENTS Q f 53.??? 1970 3,180,099 4/1965 Mikolajczyk et al 61/54 Patented Dec. 28,1971 3,370,432 2/1968 Butler et al. 61/54 Assignee Amoco Production Company Primary Examiner-Jacob Shapiro Tulsa, Okla. Attorneys-Paul F. Hawley and John D. Gassett ABSTRACT: Piles are used quite widely in the Arctic to support buildings and structures. However, in many areas the ARCTIC "LES piles are forced upwardly by the thawing and refreezmg of the 12 Claims 7 Drawing Figs. surrounding earth. l solve this problem of pile heaving by placing a rubberlike sleeve around the pile. The lower end of the U.S. Cl 61/54, rubber sleeve is fastened to the pile below the thaw zone. The 61/36, 61/], upper end of the rubber sleeve is sealingly and slideably fitted Int. Cl E02d 5/60, about the pile above the surface. The cavity between the E02d 31/08 sleeve and the pile is filled with a viscous nonfreezing liquid. Field of Search 61/54, 36 The heaving force which would ordinarily act on the pile now A-46, 46.5 acts only on the rubber sleeve.

i! 2 i 1-, so o o 28 SURFACE j l6 THAW LINE 1 26 V P V I; v v.

PATENIED Imam 3630.037

SHEET 1 or 3 46 56 56 v Ii 50 52 2 J11:

' 5 2s SURFACE THAW l6 3; UNE l6 THAW LINE INVENTOR. GEORGE C. HOWARD TTORNE Y Pmzmsn was an SHEET 2 UF 3 vm mm vm om om INVENTOR. GEORGE C. HOWARD ATTORNEY ARCTIC PILES BACKGROUND OF THE INVENTION Field of the Invention This invention relates to the setting of piles in a permafrost zone. It relates especially to a system of preventing the piles from heaving during the refreezing of the thawed portion of the permafrost.

Setting of the Invention One of the more difficult areas of the world on which to support structures or buildings is in the Arctic North such as the North Slope of Alaska and Canada. There the upper layer or portion of the earth includes a frozen section known as permafrost. Permafrost consists of both a frozen matrix of water and soil and lens of ice without any soil. This zone extends in thickness from a few feet to a thousand feet or more. When this permafrost section is frozen it is a rigid mass. However, upon thawing, the thawed portion typically becomes fluid. Ordinarily this thawing, under natural conditions, only takes place to a depth of not over about feet in the summer and then it refreezes in the winter. However, when it refreezes, the surface of the earth heaves. That is, it causes mounds to appear.

It is most difficult to support structures or buildings on the surface of permafrost. The most common way is to set piles deep through the permafrost thawing section and support the structures from these piles. When the permafrost refreezes in the late fall and early winter, there is a tremendous upward force exerted on the piles. These piles will then rise out of the earth, sometimes as much as 18 inches or more. This of course plays havoc with any structure the piles are supposed to sup port. One way which has been used reasonably successfully in overcoming this problem is to set the piles deep into the permafrost. As a rule of thumb the portion of the piles set in the permanently frozen part of the permafrost is about two to four times as long as is the thickness of that portion of the permafrost which thaws. This of course necessitates considerable expense in obtaining real long piles and in the placing of them to such a great depth. It is thus seen that there is a great need for an improved technique and system in setting piles in this permafrost area. My invention disclosed herein provides such an improved system.

BRIEF DESCRIPTION OF THE INVENTION This is an improved pile and method of placing it. I drill a hole in the permafrost only slightly deeper than the depth to which the permafrost normally thaws. I place a rubber" sleeve about the pile, which sleeve is slightly longer than the thickness of the portion of the permafrost which melts and refreezes. The lower end of the rubber sleeve is fixed to and sealed to the pile at a point which will be below the thaw line. The upper end of the sleeve is slideably and suitably fitted to the pile which will be at the top of the surface. The cavity between the rubber sleeve and the pile is filled with a viscous nonfreezing liquid. Any upward heaving force will be transferred to the rubber sleeve but not to the pile. TI-Ie adhesive force acts on the rubber sleeve to stretch it. This adhesive force is not transferred through the liquid to the pile. Thus the pile remains in a fixed position.

DESCRIPTION OF THE DRAWINGS Various objects and a better understanding of the invention can be had from the following description taken in conjunction with the drawings.

FIG. 1 is a detailed drawing partly in section showing a pile modified according to my invention as it is being set in place.

FIG. 2 illustrates a pile of my invention after it has been set in place.

FIG. 3A illustrates a pile set in a normal manner.

FIG. 38 illustrates the pile of FIG. 3A after it has heaved.

FIG. 4A illustrates the pile of my invention set in the permafrost area.

FIG. 48 illustrates the pile of my invention when the surrounding permafrost has been subjected to heaving forces.

FIG. 5 illustrates a modification of the embodiment of FIGS. 1 and 2 to facilitate the replacing of the elastic sleeve.

DETAILED DESCRIPTION OF THE DISCLOSURE Attention is first directed to FIGS. 3A and 3B which illustrate the problem which my invention solves. Shown in FIG. 3A is a pile 10 which is set into the permafrost. The permafrost consists of an upper portion 12 which thaws and melts seasonally and a lower portion 14 which is permanently frozen. In FIG. 3B, pile 10 has been forced upwardly a significant distance. Although this heaving is a common occurrence, the exact cause and mechanism of the heaving forces is not known. It is believed that the transfer of force from the freezing permafrost to the pile is by adhesion. It has also been found that if a sufficient load is placed on top of the pile that the pile will not rise. This gives some measure and indication of the adhesive force. It also gives some indication as to the anchoring which must be made available to keep the piles from rising if they are set in a conventional manner.

It is believed that a description of the piles of FIGS. 1 and 2 will be helpful before the discussion of FIGS. 4A and 4B is given. Shown in FIG. 1 is the upper zone 12 which seasonally thaws and refreezes and the lower zone 14 which is a permanently frozen part of the permafrost. Thaw line 16 is indicated between these two portions. A borehole 18 is drilled through the upper portion 12 into the top few feet of the permafrost below thaw line 16. A pile 20 is placed inside the hole 18. Near the lower end of pile 20 and below thaw line 16 is a fixed ring 22. Rubber sleeve 24 surrounds the pile and is secured to ring 22 in a sealing connection. Ring 22 is secured to pile 20 such as by welding as indicated at 26. The upper end of sleeve 24 extends above the surface 28 of the earth. Sleeve 24 is fastened to an upper ring member 30 which is slideably mounted about pile 20. Seals 32 are provided between ring 30 and pile 20. An inlet line 34 with valve 36 is provided through ring 30 and opens into the annular space 38 between the flexible sleeve 24 and pile 20. A discharge conduit 40 having valve 42 and relief valve 44 is also provided to provide a discharge line from cavity 38 to the exterior thereof.

A viscous nonfreezing liquid is injected through valve 36 and conduit 34 into chamber 38. A suitable liquid is napalm thickened Arctic diesel fuel.

FIG. I shows how the sleeve 24 is stretched before it is placed in the borehole. The hole 18 is of course first drilled to the desired depth. Sleeve 24 is mounted about pile 20. The lower end of sleeve 24 is connected to ring 22 which is sealed to pile 20. The upper end of sleeve 24 is connected to upper ring 30 which is placed over or about pile 20. If the sleeve 24 were permitted to stay in a laterally expanded position then it might be damaged when it is placed in the borehole 18. Therefore, it is desired that the sleeve 24 hug the pile 20. This is accomplished by opening valve 42 and allowing any entrapped air or fluid to escape from the chamber 38. The sleeve is stretched by the jack arrangement shown in FIG. 3 causing the sleeve to reduce in diameter to the minimum allowed by pile 20. This includes a yoke 46, a support plate 48 on the upper end of pile 20 and a jack 50 therebetween. Annular ring 30 is connected to yoke 46 by lines 52 connected to lifting

eyes

54 and 56 connected respectively to ring 30 and yoke 46.

The annular space between the lower end of the pile 20 below ring 22 is filled with a slurry of water and soil or a waterfilled grout and allowed to freeze. The rubber sleeve 24 is relaxed now by permitting upper ring 30 to move downwardly to the position shown in FIG. 2. This is obtained by proper manipulation of jack 50. Then the jack 50, yoke 46 and lines 52 are removed. Now the space 38 between pile 20 and sleeve 24 is filled with a viscous nonfreezing liquid. This forces the sleeve 24 out against the borehole wall 18. The pile is now ready for any structure to be placed thereon as may be desired.

Attention is now directed to FIGS. 4A and 48 to show how my invention reacts to the heaving problem. Shown in FIG. 4A is pile 20 having upper ring 30 above the surface and lower ring 22 below the thaw line. Rubber sleeve 24 is therebetween. Shown in FIG. 4B the surface has heaved as shown at 58. Any upward force created by the expanding and refreezing permafrost zone is absorbed by sleeve 24. The upward force causes the sleeve 24 to elongate. As can be seen, upper member 30 has risen a considerable amount. This amount can be as much as up to about 18 inches and represents the approximate distances which the pile would have heaved had it not been for my invention. The upward force on rubber sleeve 24 merely causes it to elongate and no upward force is exerted on the pile itself as the liquid in chamber 38 cannot transfer the force laterally to pile 20.

Excessive liquid pressure in the interior of sleeve 24 is relieved by pressure relief valve 44. The outlet of relief valve 44 is connected through line 87 having valve 84 to a container 80. Container 80 contains gas 81 and viscous liquid 82 which has been forced from the sleeve through regulator 44. A bypass flow line 86 is provided around

valves

82 and 84 and relief valve 44. This bypass contains valve 85. By closing

valves

42 and 84 and opening valve 85, container 80 is connected directly to the interior of sleeve 24. When the assembly is in this condition, during freezing, a part of the viscous fluid is forced out of sleeve 24 and into container 80 compressing gas 81. When the thaw occurs the viscous fluid 82 in the con tainer 80 is forced back into the sleeve 24 until pressure is equalized between the container and the sleeve.

It is anticipated that in some situations after a period of time the rubber sleeve may become punctured or deteriorated to the point where it will no longer hold the viscous liquid. In such a case some means must be provided to replace the sleeve. One such means is illustrated in FIG. 5. Shown therein is pile 20 with deteriorated sleeve 24 connected to member 22. When the viscous fluid inside sleeve 24 is continually being lost, it shows that the sleeve 24 has deteriorated and should be replaced. The replacement should be made as soon as the deterioration is first observed. This will permit the replacement to be made before the hole 18 sloughs.

Attention will now be directed to that part of FIG. which is useful for replacing the sleeve. Before pile was set it was provided with a circumferential groove 62 which is at a position which after the pile is set is below the thaw line. Replacement sleeve 24A is connected to ring 22A. The diameter of ring 22A is less than ring 22 so that it can fit inside sleeve 24 and slide downwardly. Ring 22A has been modified to have a cavity 62 which holds an inwardly biased latching dog 64. Spring 62 is provided to force latching means 64 inwardly. Seal means 68 and 70 are provided respectively between latching means 64 and the outer wall of pile 20 and the lower cavity surface 63. The function of these seal means is to prevent fluid from above ring 22A and inside sleeve 24A from being forced to below ring 22A. Inasmuch as this sealing means can be readily perfected no further detail will be given on it in this application.

As soon as the first indication of the deterioration of the sleeve 24 is made, I insert my secondary sleeve 24A. l secure sleeve 24A to ring 22A. I remove upper ring from about pile 20. At the same time I secure the deteriorated sleeve 24 to a point above the surface 28. I then connect the upper end of new sleeve 24A to ring 30. I then position lower ring 22A over pile 20. Ring 22A is loosely fitted about pile 20 and will ordinarily slide down due to gravity. If need be, a tamping rod means (not shown) can be used to force the ring 22A down to the desired position below the thaw line. If tamping rods are used, ring 22A would be shoved downwardly before sleeve 24A is secured to upper ring 30.

While the above information has been described with a certain amount of detail other modifications can be made thereto without departing from the spirit or scope of the invention.

Iclaim:

l. A pile assembly for setting in a permafrost formation which comprises:

an elongated rigid member;

an elastic impermeable sleeve surrounding a portion of said elongated member;

first sealing means sealing one end of said sleeve and fixed to said elongated member;

second sealing means placed about said pile at the other end of said sleeve, said second sealing means being slideably mounted on said elongated member, the other end of said sleeve being sealingly attached to said second sealing means;

means to inject a fluid between the said sleeve and the said elongated member.

2. A pile assembly as defined in claim 1 including an enclosed container and a flow line connecting said container to the interior of said sleeve.

3. A pile assembly as defined in claim 1 with conduit means connecting the interior of said sleeve with the exterior and a relief valve in said conduit means.

4. A pile assembly as defined in claim 3 including an enclosed container and a flow line connecting the outlet of said pressure regulator to said container.

5. A pile assembly as described in claim 3 including a viscous fluid and having a freezing point less than about below zero.

6. A pile assembly as defined in claim 1 in which said second sealing means includes a first ring member, seal means between said first ring member and said pile, a conduit means extending from the interior of said sleeve through said first ring member to the exterior thereof, a valve and a pressure regulator in said conduit means.

7. A pile assembly as described in claim 1 including a latching groove in the exterior wall of said elongated member above said first sealing means.

8. A pile assembly as defined in claim 6 including a third sealing means having a second ring member of smaller diameter than said first ring member, and latching dogs biased inwardly carried by said second ring member to engage said latching groove of said elongated member;

a replacement sleeve attached to said second ring member.

9. A pile assembly as described in claim I including means to place said sleeve in longitudinal tension.

10. A pile assembly as described in claim 1 in which the upper end of said elongated member includes a spool member which is detachably attached to the remaining portion of the said elongated rigid member.

11. A method of setting a pile assembly in a permafrost formation in which said pile assembly includes an elongated member, and elastic impermeable sleeve surrounding a portion of the elongated member which comprises:

drilling a hole in said pennafrost formation to a depth greater than the thaw line;

securing the lower end of said sleeve in a fixed position about the lower end of said elongated member, the distance from said point of securing said sleeve to lower end of the elongated member being of a less dimension than the depth of the hole below said thaw line;

placing said elongated member and said sleeve in said hole so that the lower end of said sleeve is below said thaw line;

sealing the upper end of said sleeve in a sliding relationship with said elongated member;

placing a viscous fluid within said sleeve.

12. A method as defined in claim 11 including the step of applying longitudinal tension to said sleeve while said pile is lowered into said hole.

Claims

1. A pile assembly for setting in a permafrost formation which comprises: an elongated rigid member; an elastic impermeable sleeve surrounding a portion of said elongated member; first sealing means sealing one end of said sleeve and fixed to said elongated member; second sealing means placed about said pile at the other end of said sleeve, said second sealing means being slideably mounted on said elongated member, the other end of said sleeve being sealingly attached to said second sealing means; means to inject a fluid between the said sleeve and the said elongated member.

5. A pile assembly as described in claim 3 including a viscous fluid and having a freezing point less than about 90* below zero.

8. A pile assembly as defined in claim 6 including a third sealing means having a second ring member of smaller diameter than said first ring member, and latching dogs biased inwardly carried by said second ring member to engage said latching groove of said elongated member; a replacement sleeve attached to said second ring member.

9. A pile assembly as described in claim 1 including means to place said sleeve in longitudinal tension.

11. A method of setting a pile assembly in a permafrost formation in which said pile assembly includes an elongated member, and elastic impermeable sleeve surrounding a portion of the elongated member which comprises: drilling a hole in said permafrost formation to a depth greater than the thaw line; securing the lower end of said sleeve in a fixed position about the lower end of said elongated member, the distance from said point of securing said sleeve to lower end of the elongated member being of a less dimension than the depth of the hole below said thaw line; placing said elongated member and said sleeve in said hole so that the lower end of said sleeve is below said thaw line; sealing the upper end of said sleeve in a sliding relationship with said elongated member; placing a viscous fluid within said sleeve.