Hydraulic and earth engineering – Earth treatment or control – Shoring – bracing – or cave-in prevention
Reexamination Certificate
2000-05-18
2002-07-09
Will, Thomas B. (Department: 3673)
Hydraulic and earth engineering
Earth treatment or control
Shoring, bracing, or cave-in prevention
C405S284000, C405S262000, C052S606000
Reexamination Certificate
active
06416260
ABSTRACT:
BACKGROUND OF THE INVENTION
Many types, shapes and designs of retaining walls are used in architectural and site development applications. In several common constructions, the wall facings, which must withstand high lateral forces exerted by the retained fill, reinforcement is provided by grid-like or sheet-like materials which extend in layers within the backfill soil behind the wall face. These layered reinforcements are connected to elements forming the facing wall, typically concrete blocks, by suitable connectors. A number of recent patents have issued disclosing various forms of connectors and connecting means for such walls. See, for example, U.S. Pat. No. 5,975,810, U.S. Pat. No. 5,540,525, and the references cited therein for specific descriptions of several such connection means.
My recently issued U.S. Pat. No. 5,050,749, issued Apr. 19, 2000, and my soon-to-be issued U.S. patent application Ser. No. 08/994,327 describe a particular form of a mechanically stabilized earthen wall construction and a particularly suitable masonry unit suitable for use in such constructions. Both of those references, accordingly, are incorporated herein by reference thereto, as are all of the references which were of record in the prosecution of those patents, which references are readily available in the records of the U.S. Patent and Trademark Office.
Of the four basic classes of retaining walls, i.e., gravity, cantilever, anchored and mechanically stabilized backfill, the present invention relates solely to the latter. By way of background, gravity walls depend upon the weight of the wall itself to prevent overturning and sliding. A cantilever wall may be reinforced in order to resist applied moments and shear forces. Anchored walls resist lateral forces through the use of tieback anchors or soil nails. In contrast, mechanically stabilized backfilled walls include mechanical reinforcement members extending backwardly and generally horizontally from the front face of the wall into the retained embankment soil to form a coherent mass. Enhanced reinforcement is attained, at least in part, by increased frictional shear resistance and passive resistance which occurs along common interfaces between the soil in the embankment and the reinforcing members. Conventional reinforcing members generally are in the form of strips, grids, sheets, rods or fibers which increase the resistance of the soil to tensile forces far beyond those which the soil alone is able to withstand.
Both metallic (steel) and nonmetallic, e.g., glass fiber and polymeric (geotextile, geogrid), materials have been used for reinforcement purposes. By definition herein, metallic reinforcements such as steel and steel mesh and glass fiber will be termed “inextensible” or “rigid” materials and nonmetallics such as geogrids and geotextiles will be termed “extensible” or “flexible” materials, owing to their disparate elastic moduli and creep resistance properties, and to be more or less consistent with similar usage in prior literature in this art.
Prior mechanically stabilized backfilled wall systems generally comprise four essential components: (1) the facing elements; (2) the connection or connectors connecting the facing elements and the reinforcing elements; (3) the reinforcing elements themselves; and (4) the reinforced soil, all of which comprise the reinforced retaining wall system. The facing elements may be precast, modular concrete blocks. The front face of such blocks may be covered with a decorative material, such as slate or the like, which is generally employed solely for aesthetic purposes.
Use of strip or rod or sheet reinforcements creates a mechanically stabilized backfill by placing such reinforcements in horizontal planes between successive lifts of soil backfill. Grid reinforcement systems are formed by placing metallic or polymeric grid elements in horizontal planes vertically spaced apart in the soil backfill.
Reinforced retaining walls have many uses, particularly in the construction of transportation facilities wherein these constructions are used to retain embankments and as roadway supports. Further uses of such walls include sea walls, bridge abutments and other, similar configurations.
Several prior retaining wall systems are known. For example, U.S. Pat. No. 4,961,673 discloses a retaining wall construction comprised of a first portion which includes compacted granular fill defining a three dimensional earthenwork bulk form which includes a plurality of tensile members dispersed within the bulk form to enhance the coherency of the mass. The tensile members project from the bulk form and are connected to a second component portion which defines a face construction. The face construction is comprised of a plurality of facing panels connected to tensile members with concrete layers enveloping the connection between the facing panels and the tensile members. See also the references cited in the '673 patent, which disclose many and varied embodiments of reinforced retaining wall systems. A recently issued U.S. patent, U.S. Pat. No. 5,586,841, discloses a modular block wall which includes dry cast, unreinforced modular wall blocks with anchor type, frictional type or composite type soil stabilizing elements recessed therein and attached thereto by vertical rods which also connect the blocks together. The soil stabilizing elements are positioned in counterbores or slots in the blocks and project into the compacted soil behind the courses of modular wall blocks. The many and varied connector means disclosed in that patent, all of which are wholly unrelated to the system of the present invention, provide indications of the current state of this art in the retaining wall field. See also, U.S. Pat. No. 5,540,525, cited hereinabove, for recent teachings regarding connector means.
Mechanically stabilized backfill systems have many advantages over other types of systems. Those advantages include relatively easy and rapid construction, stability of the wall during construction, regardless of height or length, relative flexibility with respect to lateral deformation and differential vertical settlements, and, importantly, economic advantages. Disadvantages may include corrosion of metallic reinforcements (which may be delayed by galvanizing or by the use of resin coatings), excessive creep in the case of polymeric reinforcements and the depth and expanse of excavation needed in certain instances.
In contrast to the prior mechanically stabilized earthen wall constructions known and described hereinabove, which include face wall elements and reinforcements extending from the face wall into the backfill soil connected to the facing wall by various connector means, the reinforced wall system according to the present system is self-connecting, wherein the reinforcements and the facing wall together form a unitary, 3-dimensional stabilized construction having no separate and distinct connectors for connecting the wall elements and the reinforcing means.
Modular units of the invention may be constructed from a lower foundation level up to a certain designated height employing reinforced backfill, above which height the wall can be constructed as a conventional gravity wall, thus allowing increased construction flexibility, for example permitting unrestricted excavation of the retained soil near the crest of the wall to install utilities, etc.
The self-connecting system of the invention imposes only compressive stresses in the facing blocks. Concrete is very strong under compression and, as a result, this self-connecting system has substantially no weak links. The front faces of the blocks serve mainly as a facade rendering a desired aesthetic appearance. It also provides protection for the reinforcements such as from UV radiation, vandalism and fire (for polymeric reinforcements) and from fluctuating moisture that causes corrosion of metallic reinforcements.
The wall systems according to the invention comprising the reinforcement members and the facing blocks are massive and exceedingly strong, allowing- the use of
E. Alan Uebler, P.A.
Pechhold Alexandra K.
Permawall Systems, Inc.
Will Thomas B.
LandOfFree
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