Slotted Mandrel for Lateral Displacement Pier and Method of Use

• US 20080193223A1
• Filed: 05/19/2006
• Published: 08/14/2008
• Est. Priority Date: 05/20/2005
• Status: Active Grant

• Current Assignee: Geopier Foundation Company Incorporated (Tensar International Corporation)
• Original Assignee: Geopier Foundation Company Incorporated (Tensar International Corporation)
• Inventors: Wissmann, Kord J., Peterson, Gale M.
• Granted Patent: US 8,079,780 B2
• Time in Patent Office: Days
• US Class Current: 405/229
• CPC Class Codes: E02D 3/08 by inserting stones or lost bodies, e.g. compaction piles sand drains for soil compaction E02D3/10; stressing soil while forming foundations E02D27/28
• CPC Class Codes: E02D 3/10 by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains E02D3/11 takes precedence; soil-penetrating vibrators with auxiliary watering E02D3/054; drainage of soil in general E02B11/00
• CPC Class Codes: E02D 5/385 with removal of the outer mould-pipes documents also covered by one or several of the groups E02D5/40 - E02D5/44 are classified in all the relevant groups
• CPC Class Codes: E02D 5/66 Mould-pipes or other moulds for plant use B28B
• CPC Class Codes: E02D 5/72 Pile shoes
• CPC Class Codes: E02D 7/18 Placing by vibrating vibrators for soil compacting E02D3/046

Abstract

A slotted mandrel is used in displacement pier construction. Longitudinal slots are formed in the sides of the hollow mandrel which allow for the introduction of aggregate efficiently into the mandrel from a hopper through which the mandrel passes while being driven into the ground. Water may also be employed with the aggregate. Once in the ground the mandrel is raised to release the aggregate (and water if present) into the formed hole in lifts and a mandrel head then compacts the aggregate in the hole. This apparatus and method obviates the need for complicated and expensive hoppers that are raised with the mandrel or the use of expensive aggregate delivery systems.

Claims

1. A system for constructing aggregate piers which comprises a hollow mandrel having elongated slots spaced vertically in a sidewall of said mandrel, a base machine for driving said mandrel generally vertically into the ground, and a hopper at the ground surface through which said mandrel passes, said hopper filled with aggregate to flow into said mandrel through said slots.

2. The system of claim 1, wherein the mandrel has a cylindrical shape.

3. The system of claim 1, wherein the mandrel has an articulated shape, such as a hexagonal or an octagonal cross-section.

4. The system of claim 1, wherein the mandrel includes a mandrel head and a mandrel shaft and said mandrel head is larger in diameter than said mandrel shaft.

5. The system of claim 1, wherein the mandrel includes a mandrel head and a mandrel shaft and said mandrel head has an outside diameter the same as the mandrel shaft.

6. The system of claim 1, wherein the mandrel has a mandrel head having a beveled shape.

7. The system of claim 1, wherein the mandrel has a cylindrical mandrel head.

8. The system of claim 1, wherein the aggregate is selected from the group consisting of stone, fine materials, recycled concrete, recycled asphalt, slag, or other construction materials.

9. The system of claim 1, further comprising a sacrificial plate positioned in the bottom of said mandrel.

10. The system of claim 1, wherein water is added to the aggregate.

11. The system of claim 1, further comprising a valve positioned in the bottom of said mandrel to alternately retain said aggregate in said mandrel and release said aggregate from a bottom of said mandrel.

16. The system of claim 1, wherein said elongated slots spaced vertically in a sidewall of said mandrel includes two series of said slots spaced vertically on opposite sidewalls of said mandrel.

12. An apparatus for constructing aggregate piers which comprises a hollow mandrel having vertical slots spaced longitudinally therein and a sacrificial driving shoe positioned at the bottom thereof, a base machine for driving the mandrel and driving shoe vertically to a depth in the ground, and a hopper having a hole through which said mandrel is driven and containing aggregate which flows into said mandrel through said slots as said mandrel is driven into the ground.

13. A slotted mandrel for constructing aggregate piers which comprises an elongated tubular body and a series of vertical slots extending longitudinally through said body along a major length of said body.

14. The slotted mandrel of claim 13, wherein said slots have a width which is no more than fifty percent (50%) of the peripheral length at any cross-sectional elevation of said mandrel body.

15. The slotted mandrel of claim 13, wherein said slots are sized to permit aggregate to flow freely from outside said mandrel body to inside said mandrel body.

17. A method for constructing an aggregate pier in ground soils where sidewall stability of a vertical cavity is difficult to maintain, which comprises:

positioning a slotted mandrel vertically in a hole of a hopper placed at ground level;

filling said hopper with aggregate;

driving said slotted mandrel through said hopper and said hole while aggregate flows into the mandrel through slots of the mandrel;

driving said mandrel to form a hole to a desired vertical depth while filling said mandrel with aggregate through said slots;

lifting said mandrel in said hole to allow aggregate to flow out at a head of the mandrel; and

driving said mandrel downwardly to compact the aggregate which flowed out of said mandrel head into the hole.

18. The method of claim 17, wherein the lifting of said mandrel in said hole is only a short distance to allow a lift of aggregate to flow out into said hole and the driving of said mandrel downwardly compacts the lift of aggregate, and the aforesaid steps are repeated for each aggregate lift as the mandrel moves upwardly in the hole until said aggregate pier is formed.

19. The method of claim 17, wherein said driving of the mandrel downwardly to compact the aggregate causes the aggregate to push laterally into the sidewalls of the hole and increase the pressure in the surrounding soils.

20. The method of claim 17, wherein water is added to the aggregate.