Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Reexamination Certificate
2001-07-12
2003-03-25
Bagnell, David (Department: 3673)
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
C405S284000, C405S286000, C403S381000
Reexamination Certificate
active
06536994
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a retaining wall block system for use with soil reinforcement materials, such as a geogrid. In particular, this invention relates to a retaining wall block and connectors used with geosynthetic materials.
BACKGROUND OF THE INVENTION
Numerous methods and materials exist for the construction of retaining walls. Such methods include the use of natural stone, poured in-place concrete, pre-cast concrete, masonry, and landscape timbers or railroad ties. In recent years, segmental concrete retaining wall units which are dry stacked (i.e., built without the use of mortar) have become a widely accepted product for the construction of retaining walls.
Many retaining wall systems described in the art include the use of reinforcing materials, also referred to as geogrids, geosynthetic reinforcement, or geogrid tie-backs.
Reinforcement materials may be inextensible, such as steel mesh, or extensible geosynthetic materials, such as mats and oriented polymeric materials. For example, flat polymeric sheets are used to form geogrids by forming holes in the sheets and then drawing them to orient the polymer and increase the modulus. Such polymeric materials include high density polyethylene (HDPE) and these materials form relatively rigid geogrids commercially available under the trade designation “TENSAR”.
While the HDPE materials are relatively rigid, a second type of geosynthetic material is a generally more flexible. These may comprise rectilinear polymer constructions characterized by large (e.g., 1 inch (25 cm) or greater) openings. In these open structure geogrids, polymeric strands are woven or “welded” (by means of adhesives and/or heat) together in a grid. Polymers used for making relatively flexible geogrids include polyester fibers. The polyester typically is coated with a polyvinyl chloride (PVC) or a latex topcoat. The coating may contain carbon black for ultraviolet (UV) stabilization. Some open structure geogrids comprise polyester yarn for the warp fibers and polypropylene as the fill fibers. Another flexible reinforcing geosynthetic material is fabric, i.e., woven constructions without large openings. These fabrics typically comprise polymers and are referred to as geofabrics. The geofabric can be laid between courses of blocks in a wall, and typically is tied into the wall and held there. When blocks are configured to have pin connectors, for example, a hole or slit is formed in the geofabric at the construction site and the geofabric is held on the blocks by fitting it over the pins.
A geogrid with an open structure, either the relatively rigid HDPE geogrids or the relatively flexible open structured geosynthetic materials also can be hooked onto a block or blocks by means of pins. Alternatively, rake-shaped connector bars can be used with a block with the prongs of the connector extending through the openings in the geogrid. However the geogrid connects to the block, the geogrid extends behind the retaining wall and ties into the earth behind the wall, thus increasing the structural strength of the wall.
For example, after placement of a course of blocks to the desired height, geosynthetic material is placed onto a course of blocks and held in place by means of pins in the block (which may have a primary function of holding blocks together) or by means of special connectors. The geosynthetic material is put under tension by pulling back and staking the geosynthetic material behind the retaining wall. Backfill is placed and compacted over the geosynthetic material. Construction of the wall continues and may include another layer of geosynthetic material.
There are some disadvantages in the use of both the rigid HDPE and the flexible polymer geosynthetic materials, including PVC-coated polyester geogrids and polyester woven fabrics. For HDPE geogrids and the flexible polyester geogrids or geofabrics, there typically is low connection capacity between the geogrid and the wall, as present systems rely mainly on friction to hold the geogrid in place. Friction between a block and a flexible geogrid or geofabric can result in abrasion and damage.
A need in this art is a retaining wall block system that will provide for stronger connection of the geosynthetic material to the block wall. Such a system would provide for greater ease of handling during installation of the geosynthetic material. A better connection method would also permit the use of relatively low cost, low strength polymer geogrids and geofabrics without damage to the geogrid during installation or use.
SUMMARY OF THE INVENTION
A retaining wall block system comprising a grooved block and a connector for use with a geogrid. In one embodiment, the connector is a channel connector configured to be used with flexible geosynthetic material, such as fabric or open structure polymer grids. The advantage to this connector is that it prevents damage to the fabric by abrasion from the blocks in the wall. In another embodiment, the connector comprises a plurality of spaced-apart projections adapted to be used with an apertured, relatively rigid geogrid. The connector holds the geogrid firmly in place, providing for increased connection capacity.
In one aspect, this invention is a connector for engaging a geosynthetic material used for stabilizing a wall formed from a plurality of wall blocks having a top surface defining a groove, the connector comprising an elongate channel portion having first and second sides defining a channel therebetween; and an elongate bar configured to engage a section of the geosynthetic material within the channel, the channel portion and bar being sized to be accommodated within the groove of at least one block.
The connector may comprise polyvinyl chloride or polyethylene copolymer. One of the first and second sides of the elongate channel portion may face the top surface of the block, or the channel may open onto the top surface of the block.
In a second aspect, this invention is a retaining wall comprising a plurality of blocks including at least one lower course and at least one upper course, at least one block having a top surface defining a groove, the groove being substantially perpendicular to a vertical plane of symmetry; a geosynthetic material; and a connector including a channel portion having first and second sides defining a channel therebetween and an elongate bar configured to engage a section of the geogrid within the channel, the connector being sized to be accommodated within the groove of the at least one block when the geogrid is engaged in the channel. The geosynthetic material may comprise fabric. The connector may be sized to be accommodated within the grooves of at least two adjacent blocks in one course of the plurality of blocks.
In a third aspect, this invention is a retaining wall comprising a plurality of blocks including at least one lower course and at least one upper course, each block of the plurality of blocks having opposing front and rear faces, at least a portion of the front face being substantially parallel to the rear face, the at least one block having a top surface defining a groove, the groove being substantially parallel to the rear face; a geosynthetic material; and a connector including a channel portion having first and second sides defining a channel therebetween and an elongate bar configured to engage a section of the geogrid within the channel, the connector being sized to be accommodated within the groove of the at least one block when the geogrid is engaged in the channel.
In a fourth aspect, this invention is a connector for engaging an apertured geogrid used for stabilizing a retaining wall formed from a plurality of wall blocks having a top surface defining a groove, the connector comprising: a base portion; a plurality of spaced-apart projections extending from the base portion, each projection including a top portion and a spacing portion intermediate the base portion and the top portion, each spacing portion having a first width, each top portion having a second width, the second widt
Bagnell David
Keystone Retaining Wall & Systems, Inc.
Popovich & Wiles, P.A.
Singh Sunil
LandOfFree
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