Claims
- 1. A method of constructing a pile in situ through a region of unstable soil to rest on a region of stable soil, said method comprising the steps of:
- (a) forming a hole through the unstable soil to a region of stable soil by allowing an elongate self-propelled soil displacing mole to descend to the stable soil, said mole drawing down with itself a first tubular member of internal diameter larger than the external diameter of the mole to line the hole;
- (b) withdrawing the mole up through the bore of the first tubular member;
- (c) inserting a second tubular member within the first tubular member, the second tubular member having an external diameter smaller than the internal diameter of the first tubular member and an internal diameter larger than the diameter of said mole;
- (d) filling the hole within the second tubular member with concrete;
- (e) inserting said mole into the filled hole before the concrete sets to produce a pile footing in said stable soil at the base of the second tubular member;
- (f) withdrawing said mole;
- (g) refilling the hole in said second tubular member with concrete and allowing the concrete to set to form an in situ double cased pile with an integral footing; and
- (h) completing steps (d) through (g) whereby the first tubular member may receive heave loads from the surrounding soil and move longitudinally along the axis of the pile without transfer of such loads to the second tubular member thereby isolating the pile from frictional engagement with the unstable soil.
- 2. The method according to claim 1 wherein the first and second tubular members extend over substantially the full length of the pile.
- 3. The method according to claim 1 wherein the first tubular member is of steel.
- 4. The method according to claim 1 wherein the second tubular member is of polyvinylchloride.
- 5. The method according to claim 3 wherein the second tubular member is of polyvinylchloride.
- 6. The method according to claim 1 wherein the second tubular method is cardboard.
- 7. The method according to claim 3 wherein the second tubular method is cardboard.
- 8. A method of constructing a pile in situ through a region of unstable soil to rest on a region of stable soil, said method comprising:
- (a) forming a hole through said region of unstable soil to a region of stable soil by directing an elongate self-propelled soil displacing mole to descend downwardly through said region of unstable soil;
- (b) lining a portion of the length of said hole with a first tubular member having an internal diameter significantly larger than the external diameter of the mole, said lining extending through said region of unstable soil leaving the hole at the bottom thereof unlined for a length of at least equal to half the length of said mole;
- (c) withdrawing said mole through the bore of said first tubular member;
- (d) lining said first tubular member with a second tubular member, said second tubular member having an outside diameter smaller than the inside diameter of said first tubular member and an inside diameter larger than the diameter of said mole, said second tubular member extending below the bottom end of said first tubular member and to said region of stable soil;
- (e) filling said second tubular member with unset concrete and directing said mole downwardly through said unset concrete to force the concrete outwardly into an enlarged pile footing below said second tubular member, and then withdrawing said mole before said concrete sets; and
- (f) refilling said second tubular member with concrete to form an in situ doubled cased pile with an integral footing, said pile resting on stable soil and isolated from said unstable soil over at least a portion of its length by said first tubular member.
- 9. The method according to claim 8 wherein the first and second tubular members extend over substantially the full length of the pile.
- 10. The method according to claim 8 wherein the first tubular member is first formed of steel.
- 11. The method according to claim 8 wherein the second tubular member is first formed of polyvinylchloride.
- 12. The method according to claim 8 wherein said second tubular member is first formed of cardboard.
- 13. The method according to claim 8 wherein steps (e) and (f) are completed without expanding the second tubular member against the first tubular member whereby the first tubular member may receive heave loads from the surrounding soil and move longitudinally along the axis of the pile without transfer of such loads to the second tubular member thereby isolating the pile from frictional engagement with the unstable soil.
BACKGROUND OF THE INVENTION
This patent application is a continuation-in-part application of U.S. patent application Ser. No. 288,133 filed on July 29, 1981 now abandoned.
This invention relates to the construction of an in situ pile in ground liable to uplift.
My published British Patent Application No. 2048999A, the disclosure of which is incorporated herein by reference, discloses a method for constructing a pile in situ comprising: forming a hole in the subsoil by allowing an elongate self-propelled soil displacing mole to descend through the subsoil; withdrawing the mole; filling the hole with concrete; allowing such mole to descend within the filled hole before the concrete sets to produce a pile footing and to displace concrete into the hole wall; withdrawing such mole; and refilling the hole with concrete and allowing the concrete to set to form an in situ pile with an integral footing.
My published British Patent Application No. 2054709A, the disclosure of which is incorporated herein by reference, further discloses a method of constructing a pile in situ comprising: forming a hole in the subsoil by allowing an elongate self-propelled soil displacing mole to descend through the subsoil; said mole being partially received within and drawing down with itself a tubular member of internal diameter larger than the external diameter of the mole whereby to line the hole; withdrawing the mole up through the bore of the tubular member; filling the lined hole with concrete; allowing such mole to descend within the filled lined hole before the concrete sets to produce a pile footing and to displace concrete from the bottom of the hole up outside the tubular member into the actual hole wall; withdrawing such mole; and refilling the hole with concrete and allowing the concrete to set to form an in situ cased pile with an integral footing.
One advantage of forming the hole by such methods of soil displacements, as opposed to soil removal, is to enhance the skin friction effect so that the pile bears a load by this effect as well as by direct end loading on a firm substratum. However certain subsoil materials are prone to expansion or swelling, for example clay in the presence of moisture. Thus, a stand of mature trees may be felled and new housing built. The tree roots no longer abstract ground water and so the clay absorbs moisture and swells over a period of months or years causing heave or uplift to the foundations of the houses.
Where heave is anticipated one course is to support the footings of the new buildings on piles taken down to the rock or other firm substratum. The footings themselves can be substantially isolated from the effects of heave by resting them on clayboard, e.g., of polystyrene. The end loading of the piles is taken by the substratum, but the remaining problem is the effect of uplift on the piles themselves due to the skin friction effect. This problem is particularly important where the piles are formed in situ holes prepared by soil displacement as discussed above.
An object of the present invention is to provide a method of constructing a pile in situ in which the above described problem of heave or uplift due to the skin friction effect is avoided.
The present invention relates to a means and method of isolating piles or footings from unstable soil, by creating a footing below the unstable soil, and sleeving the pile.
The particular invention is particularly suited for situations in which it is not practical or feasible to excavate the unstable soil to reach stable soil. The footing may be formed in the stable soil without removing the region of unstable soil.
The invention is also suited to the in situ construction of such a pile or footing under an existing building.
The method of constructing a pile in situ may be summarized as follows:
forming a hole in the subsoil by allowing an elongate self-propelled soil displacing mole to descend through the subsoil; said mole drawing down with itself a first tubular member of internal diameter significantly larger than the external diameter of the mole to line the hole;
withdrawing the mole up through the bore of the first tubular member;
inserting a second tubular member into the first tubular member;
filling the hole within the second tubular member with concrete;
allowing such mole to descend within the filled hole of the second member before the concrete sets to produce a pile footing;
withdrawing such mole; and
refilling the hole with concrete and allowing the concrete to set to form an in situ cased pile with an integral footing, whereby to isolate the pile from frictional engagement with the subsoil over at least a portion of its length.
It will be appreciated that the desired isolation is accomplished by a sliding motion of the first, outer tubular member vertically in relation to the second, inner tubular member and the concrete of the pile.
Normally the first and second tubular members would extend over substantially the full length of the pile down to adjacent the integral footing. The first tubular member could be steel and the second could be of polyvinylchloride or of cardboard.
US Referenced Citations (8)
Foreign Referenced Citations (3)
| Number |
Date |
Country |
| 1392868 |
May 1975 |
GBX |
| 2048999 |
Dec 1980 |
GBX |
| 2054709 |
Feb 1981 |
GBX |
Continuation in Parts (1)
|
Number |
Date |
Country |
| Parent |
288133 |
Jul 1981 |
|
Patent Grant
4605339
