Hydraulic and earth engineering – Foundation – Columnar structure
Reexamination Certificate
1999-07-14
2001-05-22
Pezzuto, Robert E. (Department: 3671)
Hydraulic and earth engineering
Foundation
Columnar structure
Reexamination Certificate
active
06234720
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to sheet piles which are driven through soils to form retaining walls or bulkheads. More specifically, the present invention relates to a reduced skin friction sheet pile which minimizes the downward frictional force (down drag) applied to the sheet pile by the settling of compressible soils surrounding the pile after the pile has been driven.
2. Description of the Related Art
Sheet piles are piles that interlock with each other to form walls or bulkheads that are capable of retaining soils and/or water depending on the particular application. Typically, these piles are relatively long, slender structural members which can be formed with any one of a variety of cross-sectional shapes including flat, U-shaped, and Z-shaped configurations, among others. The side edges of the sheet piles are configured to interlock with each other so that the piles can be arranged in edge-to-edge relationship to form bulkheads of various shapes. The sheet piles usually are driven through compressible soils to a sufficient depth so that the downwardly driven ends of the sheet piles penetrate harder underlying materials to a specified depth or penetration or until refusal is achieved. Typically, significant support of the piles is provided by these underlying harder materials.
Pile penetration results in a downward frictional force on the piles that is a function of the horizontal stress applied to the pile by the soil and the coefficient of friction of the pile's exterior surfaces relative to the soil. This downward force can result in failure of a sheet pile bulkhead due to an unexpected downward movement of the piles, or increase the time required to install the pile.
For many years, departments of transportation, structural engineers and geotechnical engineers have struggled with the problem of how to reduce downward frictional forces imposed upon piles. Many costly measures have been implemented to address this problem.
Sheet piles are installed without consideration for the downward friction force as part of the pile design. This method results in considerable increased construction cost.
In cases in which the anticipated structural load on the piles is increased to account for a downward frictional force anticipated, this results in a higher capacity pile which requires driving the pile farther into the harder consistency soils, thereby requiring an increase in pile length and an increase in the capacity of the pile driving hammer capable of driving a pile to a higher criteria. In some cases, these requirements increase the cost of pile driving and the length of time for pile installation and may require an increased cross sectional area of the pile to allow for the higher capacity.
Historically frictional considerations have not been an issue when installing sheet pilings. They have generally been overdriven which usually results in substantial added cost of installation.
Sheet piles oftentimes are temporarily driven into soils and then removed when associated work has been completed, such as when a temporary bulkhead for diverting water is required, or for accommodation of staged construction. As sheet piles are installed, sometimes cohesive soils are encountered and it becomes difficult to penetrate and friction becomes a major problem. The piles are difficult to install causing a tremendous drain on labor and equipment resources. During removal of the piles, frictional forces between the outer surface of the piles and the soils surrounding the piles increases the extraction force which must be exerted upon the piles in order to pull the piles form the soils. Depending upon the particular characteristics of the surrounding soil, extraction of such a temporarily driven pile can be extremely difficult, and can place excessive strain upon the pile removal equipment and involves additional time spent at the construction site.
Therefore, there is a need for improved sheet piles which address these and other shortcomings of the prior art.
BRIEF SUMMARY OF THE INVENTION
Briefly described, the present invention relates to a reduced skin friction sheet pile which reduces the downward frictional force applied to the pile by the settling of compressible soils surrounding the pile during and after the pile has been driven into the soil and upon extraction. A preferred embodiment of the reduced skin friction driven sheet pile is particularly suited for driving into soils having compressible soil disposed above harder soil, with the sheet pile being configured to extend downwardly through the compressible soil into the harder soil. Preferably, the sheet pile is formed of sheet material, such as steel, and incorporates elongated opposed exterior surfaces and elongated opposed side edges which are shaped for interlocking with side edges of duplicate ones of the sheet pile. A friction reduction coating is adhered to the opposed exterior surfaces over a predetermined portion of the length of the sheet pile so that when the sheet pile is driven through the compressible soil and into the harder soil, the friction reduction coating contacts at least the soft compressible soil, and thereby decreases the coefficient of friction between the opposed exterior surfaces of the sheet pile and the soft compressible soil.
In accordance with another aspect of the present invention, a preferred method includes the steps of: (1) providing a sheet pile formed of extruded sheet material, elongated and of constant size and shape along its length and having opposed exterior surfaces and elongated side edges shaped for connection to side edges of duplicate ones of the sheet pile; (2) determining the portions of the sheet piles to contact the soils; (3) applying a friction reduction coating to the opposing exposed exterior surfaces of the portions of the sheet piles to contact the soils, and; (4) driving the sheet piles into the soils. In those applications where the soils include both a compressible soil layer and an underlying harder soil layer, the step of determining the portions of the sheet piles to contact the soils preferably includes the steps of: (1) determining the depth of the compressible soil layer, and; (2) determining the portions of the piles to contact the compressible soil layer, so that the friction reduction coating need only be applied to the opposing exterior surfaces of the portions of the piles to contact the compressible and/or harder soil layers after the piles are driven into the soils.
In accordance with another aspect of the present invention, an alternative method includes the steps of: (1) providing first and second sheet piles of similar configuration, the first and second sheet piles being formed of extruded sheet material, elongated and of constant size and shape along their lengths and each having opposed exterior surfaces and elongated opposed side edges configured for interlocking with the side edges of the other sheet pile; (2) determining the depth to which the sheet piles are to be disposed into the soil; (3) applying a friction reduction coating to the opposed exterior surfaces of the portion of the first sheet pile to contact the soil after being driven; (4) driving the portion of the first sheet pile to which the friction reduction coating has been applied into the soil; (5) connecting together a side edge of the first sheet pile and a side edge of the second sheet pile, and; (6) driving the portion of the second sheet pile to which the friction reduction coating has been applied into the soil so that the first and second sheet piles interlock to form a first wall structure.
Another typical methodology is, a second wall structure can be formed that is spaced from and approximately parallel to the first wall structure so that soil can be effectively removed from between the wall structures to form an evacuated cavity without hazard of the soils outside of the walls flowing into the excavation. After work is completed within the cavity, at least a portion of the cavity can be refilled wit
Queen Frankie A. R.
Sailors Jimmy Don
Foundation Technologies, Inc.
Pezzuto Robert E.
Thomas Kayden Horstemeyer & Risley
LandOfFree
Reduced skin friction sheet pile does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reduced skin friction sheet pile, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reduced skin friction sheet pile will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2556037