Method and Apparatus For Building Support Piers From One or Successive Lifts Formed In A Soil Matrix

Abstract

A method and apparatus for forming a support aggregate pier having compacted aggregate lifts in a soil matrix, includes an elongate, hollow tube with a bulbous leading end bottom head element that is forced or lowered into the soil matrix. The hollow tube includes a mechanism for releasing aggregate from the lower head element of the tube as the tube is lifted in predetermined increments. The same hollow tube is then lowered or pushed in predetermined increments to vertically compact the released aggregate in thin aggregate lifts, while forcing a portion of the compacted aggregate transaxially into the soil matrix at the sidewalls of the cavity. The process may be repeated to form a series of compacted aggregate lifts comprising an aggregate pier or the process may include forming only a single lift for the aggregate pier while densifying adjacent matrix soils and imparting lateral stress in these soils.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application is a continuation in part application of Ser. No. 11 / 747,271 filed May 11, 2007 which is a continuation of Ser. No. 10 / 728,405 filed Feb. 12, 2004 which is a utility application based upon provisional application Ser. No. 60 / 513,755 filed Oct. 23, 2003, all of which are incorporated herein by reference and for which priority is claimed. BACKGROUND OF THE INVENTION [0002] In a principal aspect, the present invention relates to a method and apparatus for constructing a support pier comprised of one or more compacted lifts of aggregate material. The apparatus enables formation or construction of a single or multi-lift pier within a soil matrix while simultaneously reinforcing the soil adjacent the pier. The apparatus thus forms a cavity in the soil matrix by forcing a hollow tube device into the soil matrix followed by raising the tube device, releasing or injecting aggregate through the tube device into the cavity section ...

AI Technical Summary

Benefits of technology

[0007] The aggregate material is released from the special bottom head element of the hollow tube as the bulbous bottom head element is lifted, preferably in predetermined incremental steps, first above the bottom of the cavity and then above the top portion of each of the successive pier aggregate lifts that has been formed in the cavity and the adjacent soil matrix by the process. The aggregate material released from the hollow tube is compacted by the compacting forces delivered by the hollow tube and special bottom head element after the hollow tube has been lifted to expose a portion of the cavity while releasing aggregate material into that exposed portion. The hollow tube and bulbous bottom head element is next forced downward to vertically compact the aggregate and to push a portion of the aggregate laterally into the soil matrix. The aggregate material is thereby compacted and partially displaced in predetermined, sequential increments, or lifts. The process is continuously repeated along the length or depth of the cavity with the result that an aggregate pier or column of separately compacted lifts or layers is formed within the soil matrix. A vertically compacted aggregate pier having a length of fifty (50) feet or greater can be constructed in this manner in a relatively short period of time without removal of the hollow tube and special bottom head element from the soil. The resulting vertically compacted aggregate pier also generally has a formed cross sectional dimension consistently greater than that of the hollow tube.

[0030] Another object of the invention is to provide a pier forming apparatus useful for quickly and efficiently constructing compacted multi-lift aggregate piers and / or aggregate piers comprised of as few as a single lift.

Problems solved by technology

However this method of pier construction has a limitation in terms of the depth at which the pier forming process can be accomplished economically, and the speed with which the process can be conducted.

Another limitation is that in certain types of soils, especially sand soils, cave-ins occur during the cavity drilling or forming process and may require the use of a temporary casing such as a steel pipe casing.

Use of a temporary steel casing significantly slows pier production and therefore increases the cost of producing piers.

Thus, typically the process described in U.S. Pat. No. 5,249,892 is limited to forming piers in limited types of soil at depths generally no greater than approximately 25 feet.

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