Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Reexamination Certificate
2000-10-25
2002-10-01
Shackelford, Heather (Department: 3673)
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
C405S284000, C405S286000
Reexamination Certificate
active
06457911
ABSTRACT:
TECHNICAL FIELD
The present invention relates to earth retaining walls. More particularly, the present invention relates to mechanically stabilized earth retaining walls having laterally extending soil reinforcement sheets for connecting the wall to backfill.
BACKGROUND OF THE INVENTION
Mechanically stabilized earth retaining walls are construction devices used to reinforce earthen slopes, particularly where changes in elevations occur rapidly, for development sites with steeply sloped embankments. These embankments must be secured, such as by retaining walls, against collapse or failure to protect persons and property from possible injury or damage caused by the slippage or sliding of the earthen slope.
Many designs for earth retaining walls exist today. Wall designs must account for lateral earth and water pressures, the weight of the wall, temperature and shrinkage effects, and earthquake loads. The design type known as mechanically stabilized earth retaining walls employ either metallic or polymeric tensile reinforcements in the soil mass. The tensile reinforcements extend laterally of the wall formed of a plurality of modular facing units, typically precast concrete members, blocks or panels that stack together. The tensile reinforcements connect the soil mass to the blocks that define the wall. The blocks create a visual vertical facing for the reinforced soil mass.
The polymeric tensile reinforcements typically used are elongated lattice-like structures, often referred to as grids. These are stiff polymeric extrusions that define sheet-like structures. The grids have elongated ribs which connect to transversely aligned bars thereby forming elongated apertures between the ribs. As discussed below, other non-extruded tensile reinforcements have been developed.
Various connection methods are used during construction of earth retaining walls to interlock the blocks or panels with the grids. One known type of retaining wall has blocks with bores extending inwardly within the top and bottom surfaces. The bores receive dowels or pins. After a first tier of blocks has been positioned laterally along the length of the wall, the dowels are inserted into the bores of the upper surfaces of the blocks. Edge portions of the grids are placed on the tier of blocks so that each of the dowels extends through a respective one of the apertures. This connects the wall to the grid. The grid extends laterally from the blocks and is covered with back fill. A second tier of blocks is positioned with the upwardly extending dowels fitting within bores of the bottom surfaces of the blocks. The loading of backfill over the grids is distributed at the dowel-to-grid connection points. The strength of the grid-to-wall connection is generated by friction between the upper and lower block surfaces and the grid and by the linkage between the aggregate trapped by the wall and the apertures of the grid. The magnitude of these two contributing factors varies with the workmanship of the wall, normal stresses applied by the weight of the blocks above the connection, and by the quality and size of the aggregate.
Other connection devices are known. For example, my U.S. Pat. No. 5,417,523 describes a connector bar with spaced-apart keys that engage apertures in the grid that extends laterally from the wall. The connector bars are received in channels defined in the upper and lower surfaces of the blocks.
The specifications for earth retaining walls are based upon the strength of the interlocking components and the load created by the backfill. Once the desired wall height and type of ground conditions are known, the number of grids, the vertical spacing between adjacent grids, and lateral positioning of the grids is determined, dependent upon the load capacity of the interlocking components.
Heretofore, construction of such mechanically stabilized earth retaining walls has been limited to large walls involving significantly expensive projects. This is due in part to the cost of the mechanical components used for construction of such large earth retaining walls. To reduce costs, flexible tensile reinforcement sheets other than grids have been developed for use with mechanically stabilized earth retaining walls. These flexible tensile reinforcement sheets include large open-grid woven lattices and small-aperture woven lattices, as well as woven textile sheets. These other tensile reinforcements are significantly less expensive than extruded grids. However, when these other flexible reinforcements are used in construction of mechanically stabilized earth walls, their connection with the wall facing units has been a major technical challenge. Up to now, the flexible reinforcements are connected to the modular blocks through is the block-reinforcement friction. The magnitude of the frictional force, (i.e., connection strength) depends on the overburden pressure acting on the reinforcement under consideration. The higher the overburden pressure, the larger the connection strength. For small block walls, the normal stresses that are applied by the weight of blocks are limited and the required connection strength is often difficult to meet.
Accordingly, there is a need in the art for an earth retaining wall that is mechanically stabilized with normal stress by the mass of the blocks in the wall and supplemental loading by connectors transferring tensile loading on reinforcement sheets that extend laterally from the wall into backfill material. It is to such that the present invention is directed.
BRIEF SUMMARY OF THE INVENTION
The present invention meets the need in the art by providing an earth retaining wall, comprising at least two stacked tiers of blocks placed side by side to form a wall with a channel extending at least partially along a longitudinal axis of the wall. The channel defines at least two adjacent bearing surfaces and a pathway that extends from the channel to an exterior side of the wall. The channel receives an elongate connector bar that conforms in cross-sectional shape at least relative to the bearing surfaces. A reinforcement sheet wraps around the connector bar and a portion extends through the pathway laterally of the wall. The connector bar, being wrapped by a portion of the reinforcement sheet and received in the channel with the reinforcement sheet extending laterally and a portion thereof loaded by backfill, mechanically engages the bearing surfaces of the channel to distribute the tensile loading to the block.
In another aspect, the present invention provides an earth retaining wall, comprising at least two stacked tiers of blocks placed side by side to form a wall with a channel extending at least partially along a longitudinal axis of the wall. The channel is defined by vertically opposing blocks in the tiers of blocks with respective top and bottom surfaces of adjacent blocks defining two bearing surfaces. The blocks closely nest together while leaving the pathway therebetween through which the reinforcement sheet extends. The channel receives an elongate connector bar that conforms in cross-sectional shape at least relative to the bearing surfaces. A reinforcement sheet wraps around the connector bar and a portion extends through the pathway laterally of the wall. The connector bar, being wrapped by a portion of the reinforcement sheet and received in the channel with the reinforcement sheet extending laterally and a portion thereof loaded by backfill, mechanically engages the bearing surfaces of the channel to distribute the tensile loading to the block.
In another aspect, the present invention provides a method of constructing an earth retaining wall, comprising the steps of:
(a) placing first and second tiers of blocks side by side to define a length of a wall with a channel extending at least partially along a longitudinal length thereof, the channel defining at least two bearing surfaces, and a pathway extending from the channel to an exterior side of the wall;
(b) wrapping a portion of a reinforcement sheet over a connector conforming in cross-sectional shape at least relative t
Pe Zehong Yuan
Scales John M.
Baker, Donelson Bearman & Caldwell
Geostar Corporation
Lagman Frederick L.
Shackelford Heather
LandOfFree
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