Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Reexamination Certificate
2000-04-17
2002-04-16
Bagnell, David (Department: 3673)
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
C405S285000, C405S286000
Reexamination Certificate
active
06371699
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to stabilized earth structures, such as retaining walls.
BACKGROUND OF THE INVENTION
Wall systems for retaining soil and the like are well known in the prior art, particularly for use in association with the construction of roadways and railways. It is known in the prior art for retaining wall systems to utilize the weight of the retained material to assist in the stabilization of the retaining wall system. It is also known in the prior art for retaining wall systems to be constructed out of mass-produced components, for reasons of economy in purchase and installation. However, known prior art retaining wall systems which utilize the weight of the retained material suffer from, inter alia, unduly high production and installation costs, and a lack of flexibility in use.
An example of such prior art is shown in U.S. Pat. No. 5,127,770 (Ditcher), issued Jul. 7, 1992. In the Ditcher patent, a levelling pad is first installed for the structure. Thereafter, discrete facing panels, preferably precast in concrete, are arranged in stacked coplanar relation. As each course of panels is laid down, interlocking tie-backs with anchors are installed, which lock each panel to the panels adjacent, and the region behind each panel is filled with fill material and compacted. The length of the tie-backs are a function of the height of the wall, with the tie-backs to the lower courses being preferably of greater length than the tie-backs employed in the upper courses, with the longest tie-backs being approximately 80% of the wall height.
Such a design suffers from unduly high costs of production and installation. Firstly, the installation of the levelling pad typically requires that a footing be excavated, that forms be constructed and that concrete be poured into the forms and manually levelled. Such a procedure has high associated costs, both in financial terms and in terms of the time required to complete the installation. In addition, as each course of panels and tie-backs are installed, the wall must be backfilled and compacted, which requires that suitable machinery be available throughout the entire erection process. Further, as the Ditcher invention requires tie-backs to horizontally extend approximately 80% of the wall height, with the longest tie-backs being utilized at the lower courses, additional excavation of the slope to be supported may be required, with further consequential costs. Finally, the Ditcher design teaches the use of cast concrete and reinforcing bar tie-backs, which have significant expense and further complicate the installation of the retaining wall.
It is also known in the art for tie-backs to be used of flexible material. For example, U.S. Pat. No. 4,710,062 (Vidal et al.), issued Dec. 1, 1987, teaches the use of metal tie-back strips for use in stabilised earth structures such as retaining walls. Such an arrangement has beneficial cost consequences, in that metal strip tie-backs are economical to purchase. Unfortunately, however, this design again requires that the strips extend deeply into the fill material, since the gripping friction between the strip and the surrounding fill is utilized to stabilize the retaining wall panels to which the strips are attached. Accordingly, the strips must be exceedingly long to generate sufficient friction within the fill, with associated costs in terms of excavation and fill material.
Further, known retaining wall systems of the Vidal type suffer from susceptibility to slip circle failure. For reasons of economy, known wall systems of this general type typically employ tie-backs which extend through the fill material to a distance beyond the Ranking wedge for the particular retaining wall, which is a wedge commencing at the base of the wall and extending into the fill material at an angle which is a function of the angle of repose of the particular fill material. In such manner, the weight of the stable material beyond the Ranking wedge is used to retain the unstable fill retained therewithin. It is evident that such an arrangement results notionally in a structure of significant mass being created, which incorporates the mass of all of the soil retained by the tie-backs in friction. In abnormal conditions, such as flooding or earth shifting, the entire wall system, including the soil retained by the tie-backs, can shift, although the wall system, per se, does not fail, as the soil continues to be retained behind the retaining wall. Such shifting normally occurs in a circular fashion, with the base of the wall pivoting outwardly, and has proven to be of serious concern.
It has also been found that known retaining wall systems suffer from an inability to conveniently include an unsupported structure above the level of the retained soil. Such a feature would be useful, for example, where a retaining wall is to be installed between divided roadways of different altitudes, and it is desired to incorporate a Jersey-type barrier, of the type described in U.S. Pat. No. 5,406,039 (Rerup et al.), issued Apr. 11, 1995, between the road surfaces; or where a retaining wall is used to support a highway cut, and it is desired to incorporate an acoustic barrier at the ridge. In known prior art retaining wall systems, the erection of such unsupported structures essentially constitutes new construction, requiring appropriate foundations, etc. to be installed. Moreover, such installation is complicated by the inevitable settling of the fill, which necessitates that either additional expense be incurred in more completely compacting the fill material during construction, or that construction of the unsupported above-grade structure be delayed until the fill has had an opportunity to settle.
Further, it has also been found that known retaining wall systems suffer from the presence of tie-backs utilized in the upper courses of the retaining wall, which interfere with normal surface activities, such as tree-planting, underground wiring or piping, etc.
Finally, the installation of known retaining wall systems is also complicated by the requirement that suitable drainage means must be incorporated during construction. Providing such drainage means, and ensuring that same are not damaged during construction, adds further to the costs of installation.
Wall systems of the general type having concrete wall panels inserted in stacked relation between the flanges of pairs of galvanized I-beam support columns, each of which columns being supported in the ground by a respective concrete footing, are known in the acoustical barrier art. Two well-known wall systems of this general type for use as acoustical barriers are shown and is described in detail in U.S. Pat. No. 4,325,457 (Docherty et al.), issued Apr. 20, 1982 and in U.S. Pat. No. 5,406,039 (Rerup et al.), issued Apr. 11, 1995, both of which patents are hereby incorporated by reference. Such acoustical barrier wall systems have some characteristics which are inherently well-suited to adaptation to retaining wall applications, notably, their resistance to slip-circle type failure, more particularly, the concrete footings utilized such acoustical barriers extend beneath same and can, therefore, act as pins, to resist the pivoting of the base of the wall and thereby limiting the likelihood of slip-circle failures. Unfortunately, known acoustical barrier wall systems of this type have proven unsuitable for use as soil retaining walls, particularly where the height of such installations is to exceed several meters. In order to safely support the lateral loads generated by the fill behind a retaining wall having a height of several meters or more, it is necessary to use concrete footings and support columns which are exceedingly large. As the height of such a retaining wall increases, the costs of constructing the necessary concrete footings and support columns rapidly becomes prohibitive.
It is known in the prior art for structures of the Vidal type (referenced in this specification at page 3), to be constructed with a face of posts and panels, such as i
Bagnell David
Durisol Inc.
Hofbauer Patrick J.
Lagman Frederick L.
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